Speakers' Corner

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22-Dec 2010
Thanks to all readers and respondents throughout 2010. It's been exiting to view what some have made from the constructions suggested on these pages. I was pleased to see a few building the ScanSpeak Jensen 1071 speaker, and even more exited following those cutting sheets for the DTQWT. If you have read the entry level construction, TQWT, you will know why I'm particularly fond about this.
Last winter was spent making a lot of experiments on 1st order filters and of all the speakers made, only the
PRELUDE and TQWT/DTQWT mkII have seen some of the fruits from this. The QUATTRO and OBL-11 took a lot of time as I wanted the finish right. After many, many hours have been spent in the workshop, uploading the intro page with a link to a new construction is always with mixed feelings. Is this speaker really the best I can make from these drivers? Are readers really going to pay some interest at all? What will I learn next year that might have made me do differently? Will people wire the drivers and crossovers correctly, damp the cabinets properly, etc., to hear how it was meant to sound? I could go on.
The final question is this: What's Next? The thing to do is relax and wait. Ideas will start popping up even before I think they should - and didn't I promise myself to leave speakers for a while and remodel the workshop this winter? And last winter?

Happy New Year!

18-Dec 2010
When did a planned project take the scheduled amount of time? The vintage greencones certainly didn't. Making the cabs was more difficult than expected and once the drivers were mounted, unforeseen trouble and possibilities occurred. As is often the case with vintage drivers, these were in reality made for a specific application (radios) and bringing them into a modern world may call for modifications to make the best of it.
What also could be learned from this project was that it is indeed possible to make decent bass from a driver really not suited for bass at all by applying a resonant, thin-walled box. Adding ribs to the thin panels to better control resonances might be a never ending story and the use of lightweight solid wood, like spruce or cedar used for guitars, would be even more interesting. We're into instrument making and I'm sure several years could be spent in gaining sufficient experience to control the technology.

The final two month of this year will be devoted to finishing my next open baffle construction, again based on JA8008/TW034/Eminence DeltaLite 2515 drivers, this time with a full passive crossover between bass and mid. The crossover is finished and my OB-9 test panels are playing in our living room right now and most of the panels for the final construction are just waiting for glue and lacquer in the workshop. Sound radiated from a large panel - being close to an infinite baffle - is certainly different from any usual slim-line speaker with their inevitable baffle edge diffraction, and the wide panels have qualities that makes you wonder if this is not really what it should be like. Visitors' opinions are devided.

OBL-11, Open Baffle Loudspeaker. My homage to Gilbert A. Briggs' SFB.

The OB-11 panels will be part of my stock speakers. On one side these panels are a gift to head-bangers as they can play immensely loud with low distortion. On the other hand I've never heard as much opera and live recordings before as one these panels. They provide a live-feeling that is rare.
By the way: The OB11s will have a front grille! How about that? I think it will be the only speaker on these pages - so far - having a front grille. Being some 85-90 cm wide we kind of have to try make them look like a piece of furniture although non-hifi visitors most likely will raise the question on what the heck are these strange looking panels?

The use of front grille is interesting I think. Ideally I would like to have a larger demo room with a room-wide, acoustically transparent curtain in front of the speakers, elimination the listeners ability to see what he's listening to. I'm sure this will cause some confusion - if not frustration. When we see a speaker and we see the driver set-up, we may already have made up our minds on what we think of this speaker and whether we like it or not. Obviously the listening experience counts as well, but my postulate is that we might choose quite differently if we had to base our preference entirely on listening. As humans we are - for very good reasons - enormously focused on visual appearrance. All our lives we've been trained to make judgement on visual appareance in order to know if what we see is something we should worry about - or not. Sound, odour, taste and feeling comes next.

18-Oct 2010
There are things we buy regardless of price, just because we want to own it. Not because the "thing" will provide us quality or pleasure no other product couldn't, but because we have set our minds to owing this particular product due to age, history, show-off value, or whatever.

I recently followed an auction on eBay on a single (!) Altec 755A driver including a quite well preserved cabinet. Actually I bid up to 500 USD thinking this was my max bid to satisfy my curiosity on this driver. My goodness! This driver ended at more than 2,000 USD. Crazy!

27-Sept 2010
Making an up-grade crossover for vintage Tannoy Monitor Golds, MG15, turned out more time consuming than anticipated. As always with vintage gear, we may run into surprises. The crossover data sheet from Tannoy prescribes a series coil to the low-pass section close to only one third of what was found in the actual crossover. Getting hold of the actual drivers also revealed that the schematics were far from ideal and in fact would jeopardize the performance of the driver. So, should the original schematics be maintained or should we tweak the crossover to a better performance? The fact that the Tannoy team made changes to the actual crossovers may suggest they were not satisfied themselves with the performance from the original schematics. In short it produces at huge bump at 1.5 kHz due to the steep impedance rise. Problem here was that even the change Tannoy made was in no way optimal, only taking the bump down to 1 kHz, albeit at lower level.

Peoples' attitude towards vintage equipment is very different. To some people vintage gear is almost sacred and shouldn't be changed in any way. If it only has to be kept on the shelf, this is fine with me. If the equipment actually has to be used we may leave things as they are and not really enjoy the full potential of an e.g. speaker driver. It's like digging out an old Gran Torino from the barn and leave it rusty and dented and never again enjoy the ride as it once was. Like old cars, speaker drivers may need new/restored suspensions to work properly. I've seen vintage drivers with softened spiders lacking elasticity and resilience and being pretty much useless despite pristine cone and voice coil. Towards loudspeaker drivers - usually made by the thousands - my feeling of reverence is modest. As the saying goes: It takes three hifi nerds to change a light bulb, one to do it and two to discuss why the old one was better!

The Tannoy MG15 project postponed this Autumn's fun project: A pair of resonanz-boxen for my vintage greencones. And re-building my RIAA stage is on hold too.

By the way: Check out this website if you want to protect your DTQWTs from tiny fingers :-)

02-Sept 2010
Tweaking a website layout seems more tricky than tweaking a speaker! Trying out varios designs created responses from "excellent, thanks!" to "remove the crap". Thanks to those taking the time to constructively commenting.

Making some kind of order and overview of the material accumulating over the last eight years is quite a task and I hope the new front page - being the key entry to all information - may help you find what you seek.

I've had response from a professional website designer and one of the things these guys have to fight is the appearrance of websites on various browsers and display settings. If my website pages look funny on your computer and if you bother, it would be a great help if you would send me an image of my intro page on your computer screen:
- Press "print screen" botton.
- Open "Paint" (from Microsoft Office) or similar program - a bitmap file.
- Paste your screen image and save.
- Mail your file to
troels.gravesen@hotmail.com - thanks in advance.

28 August 2010

Tweaking for the better is hard. Whenever we invest a lot of effort on improving things, we start preparing our minds for the success and may have a hard time evaluating the objective outcome of our project. And at the end of the day, the objective outcome is only a matter of statistics. If a majority of people think it is a failure, there's not much we can do about it. Have we made the best car, wine or amplifier if nobody buys it?
When it comes to something as subjective as sound, it may be even more difficult.

DTQWT tweaks is a page describing some of the things I've tried over the last couple of years to possibly improve the sound of the TQWT and DTQWT constructions. Launching the TQWT mkII and DTQWT mkII has indeed been given some thought. The kits have sold in considerable numbers and customers may wonder if they have an out-dated product. My best advice is this: If you like what you have, stay where you are. If you have box of coil/caps leftovers, the tweak is easy to try out before buying expensive caps and coils although the investment is modest.
In the DTQWT tweaks file you can read what it's all about. Extensive listening tests and positive response from visitors made me certain the tweak was worth the mkII extension.

The launch of the TQWT mkII and DTQWT mkII follows closely the QUATTRO release. If 40 liters is more acceptable than 120-150 liters, this may be a way to get the 8008/TW034 sound without upsetting family life.
Due to experiences gained during the QUATTRO work, both the TQWT and DTQWT crossovers were revised to include these latest developments, and the choice between the QUATTRO and TQWT is really a matter of size - where DTQWT will take the lead due to overall soundstage and low-end extension.

What interests me the most right now is whether people will build the QUATTRO. The construction is based on a lot of requests, but the diy-community is a tricky niche segment. It may want a lot of things, but when it comes to actually buying, things may be different. Time will tell. Sure is that this 40 liter bas-reflex design is going to be one of my - few - stock speakers.

16 June 2010

The AudioTechnology based PRELUDE was a long journey into some new territories and as should-be, a learning experience. Based on history, very few people will build this speaker due to overall cost but maybe some of the ideas can be built into similar designs based on lower priced drivers. Time will tell.
On the to-do agenda is a 40 liter bass-reflex design from the JA8008/TW034 drivers used in
TQWT and DTQWT. Many have asked for such a design and I'm curious myself how it will perform. A center speaker with the same drivers is also included in the to-do list. Both these projects will require some time as I have to make nice looking cabs - and it takes time.

Appearance is critical for any speaker design. If it looks crappy, nobody will build it. The Jensen speaker has that problem. Being the best ScanSpeak construction on these pages, it has zero feedback from people actually building the speaker. Raw MDF panels simply don't turn diy people on.
I recently sold a pair of beautiful oak-veneered speakers and buyer's spouse was truly unhappy with the prospect of having these ugly monsters in the living room. Taste cannot be argued, but I'm sure a lot of people could have better sounding speakers if design wasn't such a critical parameter. The skinny towers requested by most people are not necessarily ideal from an acoustic perspective. If instead of a 30 liter floorstander we allowed a cabinet size of 100 liters, we might get better sound from cheaper drivers. Large drivers don't have to move much and distortion is reduced compared to the poor 6" driver that has to deliver deep bass and smooth midrange at the same time.

The Chario Sonnet "review" was an interesting break from speaker building and gave some new ideas that will be tested in the future. A 34 mm dome has been modified by vented pole piece and voice coil to produce a smooth response down to 1 kHz and will be used for experiments with points of crossover in the 1-2 kHz range. Something I never found 1" domes being able to do properly.

Vintage speakers still keep me interested and the greencones are being investigated for the time being. Reproduced music can be enjoyed in numerous ways and as long as we don't push light-weight paper cones too hard, some enjoyable moments can be had.

21 April 2010

I'm pleased to have added the NOMEX 164 construction to my website. This speaker delivers a midrange that qualifies the midbass drivers for use in even bigger speaker systems as a dedicated midrange driver. Pity Peerless doesn't make an 8ohm/90dB/10inch version of the same. A 10" NOMEX, the 5.25" NOMEX middriver and the HDS tweeter might make a powerful, classic 3-way. The 10" SLS driver doesn't quite make it.

Having set up the NOMEX 164 construction, four SEAS CA18RNX drivers were at hand and would fit the front panel without further woodwork, thus the SEAS CA18RNX construction. Another 2½-way featuring SEAS 27TDC tweeter. As for the NOMEX 164, we get an awful lot of sound from a modest investment: Twice the power handling, twice the sensitivity and overall lower distortion compared to a single 6" driver having to do it all.

The Audio Technology PRELUDE is in progress. 3 pairs of different 15H52 middrivers are being tested and I think I have a candidate. Having the middriver in place more tweeters have been simulated and there may be changes. Hopefully this project will be launched over the summer. So far, it's going to be the most costly speaker I've ever launched.

New drivers: I often have requests on specific drivers and given the vast amount of drivers available, I can only cover a fraction of them. New drivers are often brought in by diy'ers needing a crossover for their dream speaker and a 3-way from the SS Illuminator 18WU may appear some day, possibly with the new SS Discovery 10F for mid and HIQUPHON OWI for treble. Based on history I know a lot of diy'ers give up when it comes to cabinet construction, so let's see.
I had the opportunity to measure the SS 15WU drivers some months ago and I certainly wasn't impressed. With dips in the 1-2 kHz range and peaky like hell in the treble range it was very hard to model and the guy bringing them in immediately sold the again. The 15WU8741T00 does some 83.5 dB/2.8 volts where the good old Revelator 15W8530-K00 does a healthy 85.5 dB/2.8 volts. And the 18WU8741T00 does 2 dB less compared to the venerable 18W8531-G00! Generally it appears SS has gone another step down the latter in reducing efficiency! Even Qm has gone down.

Vifa (Tymphany) has launched new drivers based on fancy chassis and one-piece molded paper/wood cones, Vifa Innovation, all 4 ohms drivers and the NE180W-04 looks interesting. High Qm, high sensitivity (due to low impedance) and a frequency response that doesn't look too bad. BUT... only 133 cm^2 membrane area, not a driver that can match the SS 18W Revelator. The 10" driver NE265W-04? Only 88 dB despite 4 ohms impedance. Too heavy cone. Hmm......none of these Illuminator or Innovation drivers make me drool.
What looks more interesting is the Discovery range from ScanSpeak, in particular the 10F middrivers. The 6" drivers won't deliver the deep bass of the 18W8531G00 drivers but some of these drivers should make crossover work very easy.
Other drivers people have been asking about are the SBAcoustics units. Looks interesting and very decent prices too. What didn't thrill me so much was the frequency response from some of the drivers, e.g.
SB17NRXC35-8. Nice response up to 3 kHz, then all hell breaks loose in the 4-10 kHz range, although the impedance profile suggests nothing serious is going on. Cone geometry? I'm not saying it makes a bad driver, but most likely a profile like this will take special measures when doing the crossover. Very nice TS data by the way.
I did buy some speakers this winter: The Beyma 12B100R bass drivers. 94 dB. Not sure where they end up, but some high-efficiency 3-way - some day. And I bought a pair of Audio Technology 6I52-12-06-SD drivers too. Very special drivers. Light-weight cones and 92 dB sensitivity. Not sure where these may end up either.

A center speaker based on JA8008/TW034 drivers is in preparation. Quite a few people have asked for a center speaker for their DTQWT speakers and not being a surround fan, I've been reluctant - or just plain lazy...sometimes I need a break from building speakers - to find new directions.

01 March 2010

It's been a long and cold winter and people in Scandinavia and the Northern Europe - based on response to my website - have spent a lot of time in the workshops building speakers. Apparently there's no economic recession when it comes to diy speakers.
Fortunately our local symphony orchestra have made great performances to cope with the dark and the cold, thus Mahler's 9th the other evening. Moments of intense beauty in particular 1st and 4th movements. One of my neighbours is a bass player in the orchestra and from time to time they may not be playing and have free tickets for the concerts and what he told me from taking advantage of this was quite a surprise. Sitting among the crowd he really thought things sounded crappy! Nothing compared to sitting on the podium with all the musicians around. Well, well.... We have a great concert hall and nothing wrong with the acoustics. Thus, for Mahler's 9th I bought tickets on 3rd row - to the left. This is like 3-4 meters to the nearest violins and I think I got an idea of what he meant. From this position the orchestra is a listening angle of more than 90 degrees and to be honest, sonically it's not ideal. But it certainly gives you quite a different auditive perspective and ability to hear details from all the instruments adding to the overall sonic painting. Great evening. Next in March is Nikolaj Znaider - and his Strad. Late this year Renee Fleming is visiting town and I've bought tickets. And speaking of concerts, Diana Krall was in town recently. Great music and poor sound. Her Steinway just sounded like a plastic Yamaha. Shame on the PA guys who did this.

What else has been going on in my workshop these recent months? From the most recent files, Study on stepped baffles with little impact on tweeter performance., Siri's Killer Note, it may shine through I've taken a deep look in the practicalities of making 1st order Butterworth filters. Actually it seems clear that it's easier to make a 3-way 1st order crossover compared to a 2-way. Nevertheless, the last month I've been listening to eight crossover versions of a small "6+1" monitor. In reality this can go on forever trying to improve phase integration and frequency response from changing the stepped baffle, tilt of cabinet and subsequent crossover mods. What seems mandatory is proper phase integration between 1-10 kHz. Reversing tweeter polarity we need a decent suck-out between these two extremes and things appear to start sounding right. One octave below and above point of crossover isn't quite enough. My best guess at this stage is 1½ octave and we're safe. It either takes drivers with exceptional linearity - or a lot of equalisation via notch filters. Don't be frightened by 3 notch filters in shaping the roll-off of the midbass. Fortunately these are in parallel to the driver and sometimes do very little - but may improve phase integration considerably. What also seems clear is that amplitude irregularities (linear distortion) are much less noticeable when drivers are driven from a 1st order Butterworth filter. Well in accordance with the findings of Vandersteen, et al.

Currently I have this monitor in our living room run by the JungSon and I like what I hear. I've listened to more classical music from these speakers than I use to do. Audience clapping - as always a great tool for evaluation of speakers - are improved compared to high-order filters. Clapping sounds darker with reduced impulse distortion. Sibilance is much more tolerable, which is great! Sibilance is a much too common problem due to poor stage microphones and singers having a much to close relationship to their mics. Next to this any sound of acoustic instruments seems improved and more natural with regard to timbre.
The drivers used are an 18H52 from Audio Technology and SEAS T29CF002 tweeter. Hopefully this will construction will be launched some day. I need an 18H52 driver with higher efficiency than the one currently in use and will probably have a 4 ohms version built.
All this is taking place while I wait for the final midrange drivers for the
PRELUDE. This has taken much longer than anticipated.

Oh yes, I've read Michael Fremer's review of Vandersteen Model 7 speaker (Stereophile, March 2010). The ultimate impulse and phase coherent speaker system with proprietory cones made from balsa wood and carbon fiber. I've been looking forward to this. Fremer says he could live happily ever after with this (45,000 USD) speaker system and only reservation is the lack of visceral slam from ochestral climaxes. No wonder, this speaker claims 85 dB sensitivity and Atkinson measures 84 dB. All this work and 84 dB sensitivity...Vandersteen must be really keen on keeping size small and bass extension deep.

01 Dec 2009

It's been two months since last speaker's corner and November was indeed a busy month of diy. Many, many mails with no particular theme, rather comments and questions regarding a wide range of constructions found on this website. Quite a few people have visited the 10C77 pre-study and the PRELUDE is up and running although not yet with the final midrange. The target sensitivity of the midrange has been handed over to Per Skaaning of AudioTechnology and hopefully I'll have the drivers before Christmas. In the meantime I can sand and oil the cabs.

Regarding frd and zrd files for speaker simulation: I do not provide these files from my LspCAD library. I have done a few times and people sometimes get all sorts of funny results and I do not have time to discuss how to use the files correctly. Sorry!

Looking at website statistics is always interesting and I'm surprised how many hits the L100 and Spendor BC1 have. The BC1 scores high month after month and apparently holds a huge audience seeking information. I have two front panels waiting for a BC1 refurbishing, which will probably turn BC1 lovers away in disgust, because I'll transform the cabs into solid, well-braces cabs, flush mount the drivers and make a new crossover.... How about that? I took the speakers to my livingroom recently and what a sluggish and un-precise bass performance. We should be able to do a little better here. For all the thin-walled cabinet is supposed to do, don't forget it also meant low weight, reduced production cost and not least, reduced transport costs. I don't think we should be too blue-eyed here.

Asking for contribution to the website was certainly not something I'd ever considered until my webhotel gave me three options: Reduce file size/upgrade to superpack/get lost! This is a little more polite than last time where my former webhotel just shut down my website without any warning. Who are these people running webhotels? Robots? Apparently they don't have names and they like to express themselves in one-liners. I mean, I have no interest in annoying these people and something like "Mr. Gravesen, your traffic is exceeding so and so many GB/month and you need to udgrade you hotel." No problem! Of coarse I will.
The problem is that you guys have downloaded more than 200 GB per month and the Wharfedale brochures are a heavy burden, but reducing the file size here would not really solve the problem. Generally I post a lot of high-res images and there's no way I'll reduce the quality here. Seeing is believing and so it's going to be.

11 Oct 2009

Making a crossover and connecting the drivers right may not be as easy as it seems from a quick look at the crossover schematics. I steady flow of emails from first-time diy'ers suggest that reading this file may be a good idea: the importance of wiring crossovers correctly.
I recently had a response from a DTQWT builder complaining about the bass being weak and after a few mails back and forth, it turned out the upper bass driver wasn't connected and the lower bass most likely connected with reverse polarity. No wonder it didn't play much bass. So, read the files carefully and check your wiring over and over again. There's no pointing fingers here! I often find errors in first-time speaker set-ups. Having measuring equipment is usually quite easy to find out what has gone wrong. If you're a diy'er with no measuring equipment, the only thing you can do is taking extra care in construction of the crossovers and speaker wiring.

I'm pleased and proud to have the Audio Technology 2-way back again on the website, now with the SWANS RT2H-A planar tweeter in replacement of the Raidho planar tweeter. Read here about the new AT-SW.

And I've been visiting Audio Technology to pick up the 10C77-25-10-KAP 10" bass drivers with the new sandwich cones. Initial measurements suggest a 45-55 liter cabinet volume and a decent response down to 30 Hz. The sensitivity of the driver suggests a system sensitivity of 90 dB being possible. A pre-study has been done to gather information on performance before cutting sheets: 10C77.htm

Click images to view large.

These bass drivers are some chunky beasts weighing more than 8 kgs each. Measurements suggest a flat response up to 1.5-2 kHz and for fun I tried modelling a two-way system with a point of crossover at 800 Hz. No problem at all. Next I'll do some measurements to compare the drivers with ScanSpeak 26W/8861T00 and SEAS W26FX002.

11 Sept 2009

In June's Speaker Corner I made some comments on boring "6 +1 inch" speakers and I won't change a word of what I wrote. However, a recent standmount speaker project incorporating an Audio Technology Flex Unit 6A77-25-10-KASD (4 ohms version) got me exited again on small speakers. This driver features a generous 3" voice coil former being a composite of both aluminium and kapton. Now, having some 174 square centimeter membrane area, this driver falls well in between a 6 inch and an 8 inch driver but I think it will be hard to find any other 8" driver that can truly match this driver when it comes to power handling, dynamics and resolution. It's phenomenally good and should you ever wonder if high-priced raw speakers are worth while, not to forget premium crossover components, this may be the one can demonstrate that proper design pays off.
The 6A77 driver is mated with an Accuton C44 upper mid/lower treble driver and the well-known HIQUPHON OWI tweeter. Placed in a 23 liter vented cabinet I don't think you can find a "bigger" speaker at similar size. From a 4th order LR filter crossing over at 800 and 4500 Hz, this true monitor delivers a scaringly level of transparency and is currently a great tool for telling me which of my amps really aren't that good. It's sounds magic from my 8 watts 300B amps, but obviously at low level. 20 watts SET does better but 50-100 watts is what it takes to make this speaker sing from its 2 ohms minimum impedance. Only bad I haven't got any 100 wpc amp that can match the 300B midrange.

Up-dating the ATR and ATR25 constructions for the new SWANS planar tweeter obviously made we wonder if this high-sensitivity planar was suitable for the DTQWT design. For a couple of months I had the set-up running thinking it was work done! It took an old friend to tell me this really wasn't as good as the old one. Being your own hardest critic is not always easy. Thus the DTQWT goes on as-is and is my reference speaker. I have made drawings for 1.5 meter tall version for 10" and 12" bass drivers, but when they'll see light is hard to tell. Woodwork takes time.

And no, I have not tried the RAAL ribbon and I won't. I think I have a mail every second day if I have tried this ribbon. I've tried a lot of alu ribbons and generally find them suitable for metal cones and some polyprop cones as well. For paper pulp cones - generally not a good match to my hearing. Planars usually goes well with polyprop and sometimes (heavily) coated paper. Alu domes for alu midbass drivers and sometimes polyprop or coated paper. Good softdomes goes with everything without always making the perfect match. Very little experience with ceramic domes.
I find driver integration more important than having a tweeter that may excel on single parameters like speed and resolution. Two drivers must make a good sonic match to produce a coherent sound. Trade off may be lack of resolution, but so be it. No speaker is perfect anyway.

08 July 2009

View/hear the lectures by Daniel J. Levitin at Microsoft facility.

16 June 2009

Setting up the Summer-09 open baffle project, the OB9, from JA8008/TW034 + Eminence 15" bass drivers made me realise how utterly boring conventional speakers can be. How can I ever make a 6" + 1" midbass-dome-thing again? I will be doing it, actually a lot of them, but it takes a little time to recover and see the fun in small, boxy sounding and un-dynamic speakers again. Most speakers simply cannot even come close to rendering the true dynamics of an upright bass the way a 15" driver on an e.g. open baffle can do. Small speakers may to some extent be emotional engaging, but only when we hear a really large bass driver on an open baffle - or in a horn - do we also get the physical engaging sound we're longing for. We finally get the "punch and the drama"! The featherlight kick in the stomach - and we're looking at the bass-drivers to see if the cones are thinking of leaving the chassis' - and they're certainly not. They barely move at all. Magic! With a total of 1700 square centimetres membrane area, things start to work out. No wonder some 130-150 cm^2 from a single 6" driver can't do much. Even a 2½-way system from 6" drivers won't count for more than a total of 500-600 square centimetres.

A rather big ScanSpeak construction has been launched recently, the Jensen, from 10" ScanSpeak bass driver, well-known 18W/8531-G00 for mid - and the 18W has never sounded better - relieved of pumping air and at the same time trying to cope with upper mid and lower treble. Goes well at modest sound levels, but here we render the full potential of this fine driver. Last but not least I was pleased to get first-hand experience with the 9900 tweeter. It's great, the best Revelator I think and on level with the excellent SEAS T29 domes.

The DTQWT is doing well and a lot of kits have been sold and I'm looking forward to receiving comments and pics from the buyers. I've had a number of visitors for hearing the DTQWT and the response has been good. Whatever people bring of CDs and LPs, the DTQWT will play it all. From classical music to the most outrageous heavy metal stuff.
I never thought a 150 liter construction would take off the way the DTQWT has been doing. This is not a particular small speaker, but it seems to fill a gap for high-efficiency speakers, which was my basic motivation for initiating the project and having the 8008 driver made by SEAS. The 8008 is the heart of the system and so far its versatility is by far exceeding my expectations; the
TQWT, DTQWT and most recent, the OB9. It takes time to develop new constructions and with the help of a potential JA8008/TW034 customer, a 2 x 12" version may be realised within the next year. This will be a 300 liter brutto volume monster and if I had the space, I'd build a pair for myself.

My new line stage project, 5687, is coming to an end, and the hum-war is on hold from the final version. The DTQWT system is not totally free of hum yet, but now it's one of the Audio Mirror amps that needs some attention. The blessing of home-made electronics...

I feel urged to comment on the quality of some recent Verve vinyl pressings from the US. Diana Krall, Anthony Wilson, etc. 180-200 grams "super" pressings and the vinyl surface is crap. Visually blurred and sometime so noisy it's looks like it's been taken hot from the mold and thrown into its sleeve. How come? Who's pressing these LPs? Has anyone experienced the same thing?
Shipping it back to seller (
Elusive Disc, US) just doesn't pay off.

08 April 2009

It's been a busy winter with quite a range of SEAS constructions and Scanspeak crossover for speakers coming in from diy people here in Denmark. Check ScanSpeak constructions and SEAS constructions on intro page.
And some more ScanSpeak constructions are in preparation for crossover: Three big speakers from ScanSpeak drivers:
2x21W/8554-00+15M/4531-K00+XT25TG (Mark21), 26W/8861T00+15M/4531-K00+9700 and 26W/8861T00 + 18W/8531-G00 + D2905/9900 (crossover done; still need to do some writing and box size simulation). If they turn out good, they may pop here on the website. Mark21 already there.

These early days of April the temperature has risen to some 15 deg. C and it's time for spending time outdoor, digging the vegetable garden and getting rid of the garden debris from five long winter months. Speakerwork will slow down for some months. Not least due to amplifier building although an open baffle speaker is on the to-do list; the summer fun-project, like the OB7. This time OB9 from 8008/TW034 and a 15 inch bass driver.

Identifying bottlenecks in our systems is a never ending exercise. Few years a go I had a guy visiting with all his silver interconnects and silver speaker cables and we weren't able to hear any difference comparing these to my rather mixed blessing of cables. Not at all. The set-up at that time was a modded Rotel CD player, Audio Research SP16L line stage and Copland CTA505 power amp. I don't recall the speakers at that time.
I recently took the time to make a silver cable from my LINN tonearm to the RIAA and later silver cables for RIAA to 5687 line stage and from line stage to Audio Mirror mono blocks - and well, here it was. Midrange transparency improved with reduced smearing of detail and a midrange presence I didn't think possible. The silver cables are all made from 0.4 mm pure silver in teflon tubing and all are shielded being wrapped in aluminium foil. Basically good interconnects should be able to improve the sound in any system, but I guess overall quality can be so compromised that adding silver cables just doesn't come through. Timing is important to render all qualities of the never ending tweaking process.

Once and a while we may be fortunate borrowing a piece of gear that may identify a true bottleneck in our system. The 5687 line stage with output transformers was such a piece of equipment, originating from diyhifisupply in HongKong as the TRAM w.o.t. line stage. Product is discontinued, probably due to cost of output transformers - or maybe hum problems, because the original TRAM has some serious hum problems only realised when you run real high-efficiency speakers. Cloning the TRAM isn't particularly difficult, but getting rid of the hum turned out to be serious trouble. So much trouble that I'm rebuilding the line stage with a separate power supply unit. This line stage is so good I'm ready to go all the way and I have even ordered a new power supply trafo to get all the secondary tabs I want.

*Having success with the silver interconnects, I thought it was time to try out that silver foil for speaker cables I've had on the shelf much too long. So, the foil was wrapped in paper (painters' tape) and I ran bi-wiring to the DTQWT having silver plated copper in teflon for the bass drivers.
What a disappointment! Honky kind of midrange with poor treble integration. Tried various musical sources - same thing. Hmm.....Should it rather be a multistrand silver cable, or is silver just bad for speaker cables? Switching back to the silver plated copper in teflon immediately brought back a proper soundstage with former transparency and tonal balance. Weird!

Things like the above certainly need repetition! So, next day I installed the bi-wiring system again and it wasn't quite as bad as yesterday - late evening - maybe I was tired, but something certainly wasn't right. Midrange/treble integration still didn't work. So I ran the DTQWT from the silver foil alone and now things started to develop in the direction I had expected. Silver does something to the midrange in particular. It sounds less lush, less coloured, less smeared. It sounds very cool and clean and you wonder whether you would voice your speakers differently had they been developed with silver wires, etc. How about a DTQWT set-up with silver wires, Mundorf Silver/Gold caps, Jantzen Audio Silver Coils, graphite resistors and - - dream on. This would triple the cost of the kit. Anyway, foil wires are trouble. Fragile, trouble when you need cleaning around the speakers, low WAF, etc. What I really had in mind was making a multistrand silver wire from e.g. 12 x 0.4 mm silver wire = 1.5 mm^2. I only need 2.5 meters of speaker cable + 1.25 meter for internal cabling in the DTQWTs, thus (4x12) x 3.75 meters = 180 meters of wire = 235 grams silver = 1400 DKK (250 USD) from my local supplier. Not too bad after all. Let's see.

15 February 2009

Yesterday was Saturday and with the lady of the house gone shopping, it was time for some serious kick-butt, rock'n roll. Front end was Garrard 401 + LINN ITTOK LV II arm + Dyna XX2 mkII cartridge/Transcendent RIAA with Mundorfs/TRAM w.o.t. line stage (DiyHiFiSupply)/modded Audio Mirror 6AS7 mono-blocks/Rotel RB981 for bass drivers in DTQWT speakers. The TRAM line stage has out-put transformers (w.o.t. = with output transformers) and can easily driver two power amps.
Needless to say this set-up can play at ear-splitting levels without serious distortion. So, old Sgt. Pepper and Band of Gypsys LPs were on the spinner - and not least Dog Eat Dog/Joni Michell. I've had this recording for more than 20 years and I never liked the sound, being overly bright and harsh. I always thought this LP was poorly recorded, mixed and cut, having the typical Eighties hard-hitting, short reverb on drums. The XX2 told another story, revealing details I didn't know were there.

Which makes me think of a visitor I recently had, bringing in a 20,000 DKK (~3,500 US $) TentLab CD player to compare with my slightly modded Shanling CD-T80 (I paid 650 US $ for this player from Hong Kong). Playing a wide range of CDs, we really weren't able to hear any difference at all. Now, my visitor also brought a CD which I happen to have on vinyl (Eva Cassidy) and this called for some A-B testing of vinyl vs. CD. Visitor was pretty shocked from the difference. Needless to say the CD sounded flat and congested with poor dynamics and transparency compared to what the XX2 cartridge could pick up from the vinyl grooves. Now, CDs can be good and bad. I have a (very few) excellent CDs where everything seems to have been done right to get as much information through the media as possible, but generally most of the CDs I have on my shelves are poor. In Stereophile, Feb-09, you can read about a demonstration at DIY Burning Amp Festival, where " - Jan played back samples of the same song released over a span of several decades. Each one sounded worse, more compressed, than the last. It was so shocking that it made people angry". No wonder!

Recent Months have brought a range of new speaker constructions : SP44, CNO-mkII, CNO-T25, Maya (SEAS CA18RNX/T25C003) and CNO-25 (CNO 2½-way), and I guess I'll take a break from SEAS constructions after this. I need to put together some plug'n play kits to finance new projects. And I'll be cloning the TRAM line stage and have started sourcing components. The project I'm looking forward to the most is an open baffle construction with the JA8008/TW034 drivers and some 15" at bottom. This OB should as close as possible look like the old Wharfedale SFB. I just love that design.

28 December 2008

Economic recession or not, people are building speakers like crazy these dark winter evenings and weekends - at least on the Northern Hemisphere - and coming home from work, I find my mailbox full. It takes an hour or so every evening and please forgive my short replies. Usually the Christmas holidays are very quiet with mails, so time for some writing and a few experiments.

There are a lot of speakers in pipeline the coming winter months: CNO mkII, CNO-T25 (T25C003 tweeter) and a CNO-25 (2½-way CNO). I have reworked my test cabs for these constructions.
A replacement for the
Peerless HDS134 construction has been finished, this time with HDS PBB 134 (830860) + DX25TG. The recently launched PL14 construction is a worthy alternative, but needs a 10-11 liter cab, where the HDS will do with 7.5 liters. Some HDS164 Nomex drivers (830875) are on the shelf too and might end up with the Peerless HDS tweeter in a 2½-way construction as a replacement of the old HDS164 (850438) construction.
For the
DTQWT construction Eminence DELTALITE 1520 II have been tested and is the recommended bass driver option.

A Happy New Year to all diy'ers visiting my website!

07 November 2008
Listening to music

Do you have the same experience as I that sometimes your hifi system sounds crap and sometimes just sounds great? Nothing in the system has been changed and yet there are good days and there are bad days.
Whenever possible - and when I feel like - I often listen to music on Saturday and Sunday mornings. It's weekend, I've had a long night's sleep, I'm fresh and relaxed and I'm fully open to the world and what I choose to let in.
I do this in particular when I have to evaluate a new speaker system, evaluate new coupling caps in my amps, a new cartridge or when I have new vinyls I want to fully enjoy.

I'm tired after a normal working day filled with mails that have to answered, meetings I have to attend, talk with my colleagues, driving my car and paying attention to heavy traffic, watching the news and the Obama election, etc., etc. The everyday contains an enormous amount of information that has to taken in and/or taken care of - and after all this I'm really not in the mood to be fully aware of subtle differences in the performance of hifi components. Good or bad is sometimes a matter of state of mind and not how the system is performing.
I've sometimes had visitors who have spend 1½-2 hours in a car and 5 minutes after leaving the car they sit in front of my speakers and this is a far from ideal "preparation" for having to do aural evaluations. 1-1½ hour of car noise tires our mind and ears and the general stress is bad for having to pay utmost attention to sound.
Maybe I should name my next speaker "TGI" (
Thank God It's Friday). I think I will, and the 2½-way version will be TGI-25. Anyway.....

Loudspeakers are the most troublesome components in our system. We not only listen to our speakers, we listen to our speakers and the room, and not only the speakers in our room, but the way the speakers are placed in our rooms.
Speakers rarely have #1 priority when it comes to room decoration, which is sad because really they should have unconditionally #1 priority. The "world's best speakers" in the wrong room may be a total waste of money.
Modern room construction and room decoration is often a total disaster when it comes to acoustics. In particular modern Scandinavian design with minimalistic decoration, concrete walls, tile floors and hardly any fabrics in terms of carpets and curtains. Bookshelves filled with books aren't allowed either and stored away in smaller "office" rooms. Clap your hands (once) in one of these environments and you'll often hear severe reverberation.

If you happen to have a listening room of e.g. 20-30 square meters of reasonable dimensions, square is often worst, take a day off and move your system around including all your furniture. Try every possible positioning of your speakers and hear what happens. If possible try your system in a smaller room and a bigger room too. Try the bedroom also! At least here we may have some fabrics. Now, how does it all sound? One room better than the other? One position better than the other?
I'm pretty sure you'll all be surprised from how enormously different your system performs. I've often seen people spending minor fortunes on new speakers and amps and what they should have done instead is maybe buying a heavy 3 x 4 meter carpet or move a piece of furniture into a corner of the room, etc. The number of options is infinite when it comes to tweaking acoustics - but give it thorough thought before spending 400 $ on a new pair of silver interconnects that might do something to that troublesome midrange. The money may be better spent on a new 200 $ carpet in front of your speakers.

By chance I came about this website: http://www.stereodan.com/stereo.htm
Take a look and enjoy the pics. Here's a guy who has had a good time not only sourcing his components, but who also has spend a lot of time positioning his gear and treating his room. I have no idea - obviously - how this all sounds, but I like what I see and I think it's an example to follow with heavy carpets, bass trap in corners, etc. It looks like somewhere in the UK. I don't know the guy or where the website belongs.

19 September 2008
- mails, magazines and other stuff .....

"Could I use 2 x SS 18W/16831G00 in replacement of the single bass driver in the SP38/13 construction and use the same crossover?".
Sorry, cannot... Still these are the most common questions I have. I may have to re-write the sorry-cannot file.... From the mails I have I can see that the number of files found on my website has grown considerably over the years and I've tried to organize the intro page to make better overview. Hope it helps.

"Could you change the page set-up in your files because I have an old monitor and 800 x 600 pixel setup?" Now, that's a new one! I have asked around and I can't find anyone running this format anymore. I have a standard laptop/14" screen and usually make my tables 1000-1100 pixel width. I use tables because it allows me making the page layout I want (from my stoneage Frontpage version, I admit). I'm not particularly interested in computers (- but I love what they can do) and usually stick to my old software if it works well. There are about 250 pages on my website and changing the format would be an enormous task. So, "sorry, won't".
BTW: If you press "Ctrl" and roll your mouse wheel, you can reduce/increase page size and view it all to your liking. I don't know from which Windows version this works.

The poor devil buying my TJL3Ws hadn't checked with his spouse in advance and all hell broke loose when the speakers were installed in their livingroom. Wood finish didn't fit furniture veneer and to avoid sudden divorce, the speakers were wrapped in white plastic foil.... All that nice woodwork - for Heaven's sake! Point is: Don't forget to check with your loved ones before engaging in new speakers!

More WAF issues: I had a mail from a guy showing some of my constructions to his spouse to hear her opinion about possible designs. Now that's the way to do it! Her response was: "All these speakers look like coffins! Horrible!" She has a point. Most floorstanders may look more or less like upright coffins. We only need some flowers to bury our addiction to music! The single construction she did like was the Acapella. So, I asked my wife the same question and she was in favour of the Acapella too, comparing all the speakers she'd been living with over the years. Hmm... I always liked these cabs better than anything else I've made, but it will be tough squeezing the DTQWT into an Acapella design!

Thinking of coffins, these come in all shapes and sizes and maybe this would be an options for those engaging in speaker-building for the first time. As can be seen above someone already got the idea. I have seen speakers looking more terrible than these. Some coffins come fairly cheap. Add braces and bitumen pads and a pair of 12-15" bass drivers and I'm sure you could impress you bodies - but I guess it's for "singles only". To keep green-house gasses down you can even buy coffins made from recycled materials degrading without environmental damage. Fully RoHS compliant!
(Pic in middle: calendar from an Italian coffin maker. Nice coffin, BTW)

- anyway.....

Reading the latest Stereophile I couldn't help digging into a review on the
Fried Compact 7 loudspeaker (1795 $/pair) and I'll make this short:
Stereophile: "As shown in the Follow-Up elsewhere in this publication, the FC7 significantly departs from linear frequency response on axis. A huge suck-out spans 1-5 kHz, the deepest part of which (at 3.2 kHz) is about -16 dB. There is also a suck-out from about 260 to 500 Hz, with a trough of -7dB. These doubtless account for the hollow coloration I heard, and compare unfavorable with Stereophile's 1990 measurements of Fried's Q4".
Fried's website: "Loudspeaker design and performance has little to do with producing a flat response".
Stereophile/Follow-Up: "Some people prefer such a response because it "nicefies" typically hot modern recordings...."

I suggest reading the whole article at Stereophile's website once published: http://www.stereophile.com/thefifthelement/
My point in bringing this here is that I think the reviewers are too gentle on a seriously flawed product like this. Yes, it's a critical article on a product being so badly constructed that the reviewer can actually hear something is seriously wrong, hence ships the speakers to Atkinson for measurements. First order filters, same polarity of drivers...... Hmm....Apparently Fried Products doesn't know that 1st order filters will throw each driver's phase 90 degrees in opposite direction, hence the tweeter must be connected with inverted polarity.

An extensive test of coupling capacitors has been performed on my 300B integrated amp and this is a never-ending exercise. Mundorf silver/gold/PP and VCaps are the winners here, but read for yourself.
And while we're at coupling caps: Should you have an Rotel RB981 (my workshop power amp), try replacing the two electrolytic caps at the input with some good film caps. Very rewarding. I used two 1 uF/400V Hovlands. Replace C601 and C602. These caps see 33k and can do with 1 uF caps without compromising bass extension.

Rotel RB981 with 1 uF Hovlands.
Service Manual, 800KB

Last but not least: Some bedtime reading on the state of hifi (Gordon Holt/1991 and Art Dudley/2004). Download here.

23 August 2008

Finally: The launch of the DTQWTs. It's been a long, long journey and hifi - to me - has never been more exiting. The DTQWTs are doing what I want my speakers to do: A huge soundstage, a midrange delivering the presence and detail I want without being harsh or aggressive, deep bass delivering the punch and drama we want from reproduced music and last but not least: High sensitivity allowing low-wattage triode amps to be used. With these speakers I can easily evaluate subtle differences in the quality of components used in my amplifiers. My Audio Mirror 6AS7 SET mono-blocks and the 300B SET amp are already revealing interesting - and different - ways of amplifying source material and soon a Transcendent T16 OTL will be finished and tell if omitting out-put transformers really is as important as Bruce Rosenblit says.

28 July 2008

The final DTQWT cabs are shaping up and only needs the final lacquer before finished. The DTQWTs pretty much do what I want my speakers to do and I might just quit speaker building here. My bank account to some extent reflects this as I spend more money on vinyl and less on new drivers. That's how it should be! Well, a few more amps are on my wishlist and besides a diy 300B SET under construction, a Transcendent T16 OTL has arrived.

The DTQWTs are sensitive and they project a big, wide and transparent soundstage and allow me to use all sorts of amplifiers, but I do rush to say I do not recommend 2 wpc SET amps. No matter what loudspeaker and amplifier producers may claim, there are limits. I do recommend 6-8 watts minimum. Often we see that 2 wpc amp producers may claim their products suitable for minimum 90 dB speakers, but be cautious, it very much depends. And speaker producers may claim their 90 dB speakers suitable for 5-10 watt amps. Again, be cautious. I recently made a crossover for a large 3-way speaker (ScanSpeak drivers) and I ran it from a 6 wpc SET amp and it sounded great - but indeed not very loud. If we run 2 wpc SET amps we need humongous horns with extremely light-weight paper cone drivers to render a true presentation of bass fundamentals.

Anyway, there will be more speaker constructions in the future and more 2-way/6"+1" kits and some 3-way classic kits from ScanSpeak 21W/8555-01 + mid + 8513 tweeter. I have a range of mid drivers that look very promising from simulation, i.e. simple 2nd order filters and flat impedance curves. The D2010/8513 is special in this context and seems just made for 3-ways with a relatively high point of crossover between mid and tweeter. Modern 1" tweeters are often designed to extent the lower end - to make two-ways - and some of the 3-way simulations I have made got into serious trouble when replacing the 8513/OWI with e.g. SEAS 27TFFC, SS 9500, etc. These 1" dome tweeter often takes 3rd or 4th order filter to perform from e.g. 3.5 kHz in a 3-way set-up. The EKTA might do well with the 8513 tweeter from a simple 2nd order filter at 3.8 kHz - but I'm afraid people wouldn't believe it.

The summer sale quickly ran out of 2-way kits and I need a break before launching more. Selling a kit requires quite some hours of actually making the kit with presentations, etc., and often takes 10-20 mails before it's actually sold, not to forget packing the kit to ensure safe transport. But it's also fun hearing from people all over the globe and exchanging views on speakers building.

One of my summer holidays has been spent reading reviews - speaker reviews - and gosh, are reviewers and manufacturers one big family! I'm amazed by how reviewers manage to write 3-4 pages on a new speaker that is slightly different from the old model. We are told it's a significant improved product, yet in no way does it diminish the qualities of the old product. So, we're all happy! A few times I may actually know first hand the new drivers - don't ask how - and know the changes were made to cut production costs and increase profit. I wouldn't never blame manufacturers for doing so, but the way reviewers are able to handle this is a matter of linguistic artistry. Bravo!
What's more serious is the factual errors often found. A six inch driver that is really a five inch driver and a paper cone that is really a polyprop cone, etc., etc. I sometimes wonder if the reviewer really had the speaker in his room. I guess he had, but should leave technicalities to someone qualified.

Buying on eBay has been low for the past months, but a single Wharfedale Super 8 FS/AL was found - and bought. And it's one of the better drivers from the Fifties. Much better than the terrible Super 8/RS/DD. As expected, not much of the foam surround had survived transport but I managed to find some fine felt material and have made a new surround. What I don't get from these Wharfedale drivers of the Fifties and Sixties is the acoustically transparent outer surrounds. Why? Even some of the later fabric surrounds were acoustically transparent. It causes serious trouble in the midrange. It doesn't fit with the response graphs found in Briggs' book. Any ideas?
I also found - and bought - a Wharfedale "North England M8", same basket as the Super 8 FS/AL, square alnico magnet, 15 ohms cobber wire voice coil, fabric spider (!) and - former - foam surround. I wonder what these were for - probably diy units. This is actually a NOS driver - never used and including original box. Cone in perfect shape. It will have a new felt surround like the Super 8 FS/AL.

17 May 2008

Launching a sale takes a deep, deep breath! Space and finance is the reason behind this and I know it takes tons of mails back and forth before diy-people decide to buy anything. But here we go! Take a look at the '08 Summer Sale' if you might be thinking about the following items: Acapella NEXT, TJL3W, Compact Studio Monitor Kit, JBL L100 matched drivers + crossover KIT, ARC SP16L preamp, TubeBox phono stage, Rega RB300/Incognito tonearm and W11XT speakers.
Please do not feel disapointed with me from selling the e.g. Acapella NEXT and TJL3W. If space was unlimited I'd keep these speakers forever. The numerous hours that went into designing and building them is something I simply have to repress. The recent 150 liter project has made this step absolutely necessary.

7 May, 2008

It's springtime and really not a time for doing loudspeakers, but you can always gather components for the next project while digging the vegetable garden and mowing the lawn. And so I do - like seen on the photos below. 10" bass drivers, wax coils, super caps, cables in teflon wrap, low-ohmic C-coils, new cable plugs, gold plated soldering tags, etc. All meant for the DTQWT project, i.e. Double-Tapered-Quarter-Wave-Tube.

The DTQWT is the JA8008/TW034 kit with two 10" drivers on the rear panel loading a common center horn together with the front driver. No big deal really, but finding the right bass drivers and the right dimensions of the horn has taken time. Some 5 different 10" drivers have been tested and two candidates seem to do the job well. One is Beyma 10LW30N, rather expensive but with excellent build quality. The other is a 10" Pioneer driver derived from the US. This one is cheap and does a great job too - at a fraction of the cost of the Beyma drivers.
With two 10" drivers the total (bass) membrane area of one speaker now exceeds one single 15" driver and it can be heard - and felt. Tight, deep bass.....
The DTQWT has the same front panel dimensions as the TQWT but is now 50 cm deep. WAF hasn't gone down too much from this latest version, fortunately...

My system has been through a lot of up-grades lately and this has urged me to use the very best I can afford for the DTQWT. In addition to the components seen above I'm doing homemade silver foil speaker cables and graphite resistors for the crossover. I'm not sure all these measures will contribute equally to the good sonics, but for the benefit of the doubt - and to gain experience.

Gathering components also includes bits and pieces for a 8 wpc 300B SET amp. I need a really low-wattage amp for reference with the MAE now back in Norway. The 300B amp is based on the Oliver design shown here.

20 March, 2008

I've bought a new phono cartridge! I never invested heavily in these things and I was pretty happy with my Dynavector 10x5 until a wire from one of the coils broke and these tiny wires are way too thin for repair (I tried). So, a deep pocket dive and a Dyna DV20X was in place. 400 £ for a cartridge was serious money I thought, but it provided one of these rare occasions where you - once more - have to go through a lot of your vinyl collection to hear what you've missed over the years. Self-pity is a really bad thing, but it came close and it kept me wondering what I would get for 800 £ or maybe even 1600 £. Better start saving for that next step.
The DV20X is the high-output version because it works wonder with
Bruce Rozenblit's Transcendent RIAA. I recently installed the alu/silver/teflon caps I got from Mike in Moscow. The RIAA feeds a Transcendent Grounded Grid preamp if not an Audio Research Corp. SP16L line stage. Bruce's amps provide true high-end amplification at modest price and there's no mushy valve sound if that's what you want. Solid state speed combined with all the transparency valves can provide, which is really the wrong thing to say because valves aren't slow by any means, they just have this sad image from old mushy valve amps driving inefficient speakers.
Should you want to try out the GG preamp, add the shorting circuit and the 50 k attenuator to your buying list. The standard pot supplied with the kit is crap and the ELMA attenuator is an excellent layout for listening at low levels. The GG preamp is merciless clean, neutral and transparent. The SP16L may have a slightly warmer sound compared to the grounded grid but a tad less transparency. I currently use Superior Z-caps in the GG but I have some new prototype gold/silver caps from Jantzen Audio and the GG is the place to test these. 2 x 1 uF is what's needed, leaving excellent opportunity for experimentation. I also have to try the brown 1 uF PIO cabs from Mike.
Piano is a particular difficult instrument to reproduce faithfully and I never really liked the sound from the Steinway piano on Keith Jarrett's The Köln Concert until I had this Dynavector DV20X. I always thought it sounded a little bit too harsh and aggressive. I favour the sound from e.g. Oscar Peterson's Bösendorfer piano, having a sweeter and more mellow tone. But the DV20X dig out the vibrant and forward sound of the Steinway in a very persuasive manner.

The ATR25 was finished early March - took a long time to get the cabs finished - and these are "disturbing" speakers. Disturbing because they do a lot of things better than any other speaker I have. Still don't beat my JA8008/TW034 - a matter of taste and WAF - but at half the size - and twice the cost - they take midrange clarity and treble quality to new levels. No domes can do what these planars can do, that's for sure. My 20 wpc SET mono blocks have no trouble driving these transmission lines and I'm having good times in front of these speakers. Despite high level of transparency, they handle all musical genres equally gracefully. They don't make poor recordings sound worse. Low distortion is the key word.

Right now the JBL L100 Recreation is on the workshop bench. Cabs are finished and I need to add damping, install crossovers and drivers. I think I've spoiled the L100 kit as much as possible and I'm looking forward to hear if it all makes a significant improvement compared to the originals. I think it will. The original box is rather resonant and having the 12" bass driver handling most of the midrange, there just gotta be serious improvement gained from a well damped and braced cabinet.

On my way home from work today I picked up some 5 square metres of 19 mm DMF (pre-cut to some extent) for my double TQWT, the next JA8008/TW034 system. Have collected 10" bass drivers over the last half year and I'm expecting to have some 5 pairs for test. Two pairs of Beyma drivers, two pairs of SEAS drivers and I'm waiting for the last pair of 10" drivers from the US. You can find the principal "DTQWT" design here and here: Two conical horns feeding a common center horn mouth.

The High-End Kit for Beginners is ready for sale.
Orders here at:
Article here:

The JA8008/TW034 is ready for sale.
Build a high-efficiency 2-way system for high quality low-wattage valve or ss amps.
Orders here at:

12 January 2008

The Acapella NEXTs are up and running: This project started like: "Well, I have the cabs and only need a bass driver" and turned out to one of the most rewarding projects I've made. You never can tell.

There's a long list of projects planned for 2008. After the Acapella NEXT, the ATR 2½-way is next. View ATR-2-way here. Initial test set-up will be a bass-reflex design and initial listening test from a quick simulated crossover is promising. The final cabs will probably be a classic transmission line with the same front panel dimensions, allowing the crossover to be the same for both versions.

When the ATR-2½-way is finished, the JA8008 55-litre bass-reflex is scheduled. The project has been on hold for some time as initial tests in a classic 36 x 80 x 28 cm (W x H x D) cabinet didn't sound right. The crossover was easy, measurements were good, but the sound was just too forward. Too much midrange despite an overall flat response. My main suspicion is the width of the front panel and a more narrow design will be tried. Actually similar to what can be seen on the sketch shown at the JA8008 page.
The JA8008 3-way, double TQWT, is certainly on the agenda this year. I have some old SEAS CA25FEY drivers for a start for the rear mounted bass driver.

Next project is something I'm really looking forward to do: A "W26-Classic" 3-way from SEAS W26FX002 + M15CH002 + T29CF001. Possibly the middriver is going on top in a separate semi-open cabinet. Having the mid on top is seen before in older KEF & B&W speakers. However, my initial inspiration came from the Spendor SP100 and Naim DBL. We'll see.

The W26FX002 is a very capable 2" voice coil bass driver with lots of punch and a better frequency response than suggested in the SEAS data file. It has a smooth roll-off and one of the few drivers you can stand listening to full-range. Furthermore the claimed 89-90 dB sensitivity seems to come true and this should allow an overall 90 dB system sensitivity. The M15CH002 is not an easy driver in terms of crossover construction but it can be done and I'm looking forward to hearing what this low-rear-reflection design can accomplish.

The "W26-Classic" cabs will also allow a test set-up of my JBL L100 drivers. Modelling the 123A bass driver in a 65 litre cab looks promising.

Did I say 2008? I also look at my Spendor BC1 speakers from time to time and I have 22 mm plywood sheets on the shelf for new front panels... and I've had a pair of "vintage" SEAS EXCEL W21EX001 drivers for a reasonable price. These drivers have a hard paper cone and performs exceptionally well although sensitivity is some 3-4 dB lower than promised from the old SEAS data. An "EXCEL VINTAGE" from W21EX001/W11CY001/tweeter could be interesting.
Well, one thing at a time. Fortunately this is a hobby with no boss yelling deadlines and milestones.

Speaker Talk 9 December 2007

SEAS has got a new website and it's certainly better than before. And they are about to launch a new "alnico-whizzer" driver - with rubber surround...Hmm... Have they heard the cry from the SET people right?
Anyway: I've had a pair of the new 27TBCD-GB-DXT some weeks now and this is certainly the tweeter with the most even power response I've ever had. All the way up to 20 kHz. Very well made indeed.

While the Norwegians seem fit for fight, I'm wondering how things are in Videbaek town, not too distant from where I live. Apparently people are fleeing the castle of Vifa/ScanSpeak and have started new companies, e.g. SB Acoustics and GAMUT, based on former dst employees. I'm sorry to say that whenever you guys "over there" take over smaller companies "over here", things seem to rapidly deteriorate - from our perspective. RCF, Audax and now Vifa/Peerless/ScanSpeak are examples. I'm wondering if the Tymphany air-pump can compensate for the departure of some key figures in the former dst organisation. This is - to my eyes - the only radical new product from the Tymphany company for a long time.
One thing is capitalising well known brand names, but who will make the next generation of drivers after the e.g. sliced paper range? At present we see Usher speakers fitted with drivers similar to what ScanSpeak developed 2 decades ago. Is Usher sliced paper the next to come? The new range of drivers from SBAcoustics look interesting, but purely based on specs, they seem to face tough competition from a lot of other brands. The initial announcements from SBAcoustics leaves no doubt: "Hey, we're the former ScanSpeak people!"
Soon we may have only AudioTechnology and HIQUPHON left here in Denmark. The Peerless factory has long been closed and maybe there isn't any future for driver production in Denmark, unless you develop specialty, high-priced products. Driver manufacture is not necessarily rocket science and soon the Chinese may be producing the former DK brands as is the case with a lot of former UK based brands, like QUAD, Mission, Wharfedale, etc.

This Month's Speaker Talk was meant to deal with a few reflections on how differently we perceive sound. Not a new topic, but I still wonder sometimes how people claim aural nirvana from speakers I dislike - and know first hand - like the vintage Philips 9710. I had a mail from a studio engineer, seriously suggesting this driver as a great tool for monitoring. I don't get it.
Anyway, from visiting numerous websites I came across these wise words from Wilke/Germany, and this very much tells what I had in mind:

"I have found myself 100% captured by listening to 12 x 17 cm full range drivers mounted in cardboard boxes with an open back. I have also found myself 100% involved by listening to 40 cm coaxial drivers. Every speaker has something to say! The beauty of the sound of some small driver may weigh up the power of some big driver. On the other hand, the sheer power and authority of the big driver may please me more than the delicate sound of the small ones. It depends on my mood and on the sort of musical material. I have had lengthy discussions with a former Klangfilm speaker engineer and we have both agreed that the whole matter depends very much on proportion and on harmonic and well balanced tonality. If you listen to a 20 cm full range driver you will obviously not hear the authentic impact of a full scale big orchestra. But – provided it is a “good” driver – you will hear the orchestra as an entire phenomenon. On a smaller scale!"
Read the full article here: http://www.german-vintage-loudspeakers.com/navid.458/an-approach-to-sound.htm

In line with these words, I recommend reading an article by Art Dudley (Stereophile, Nov-07, page 41) on a speaker system from Aurum Acoustics:
"Bear in mind that even the hard-core single-ended-triode movement wasn't conceived as just a new branch of high-end audio: It was intended as a whole new tree, by hobbyists who considered the old tree to be very, very sick. To the SET pioneers, audio had gone from being an interesting way of enjoying recorded music to a turgid and fetishistic exercise in irrelevance in which wealthy men with too much time on their hands try to outdo each other in identifying arcane sound effects in a handful of guru-approved recordings.
Also remember that the high-end audio establishment didn't take long to dismiss the SET guys as a bunch of self-conscious hipsters less concerned with fidelity than with the coolness factor: gracelessly aging punk wannabes whose willingness to live with grossly colored , narrow range sound reproduction is rivalled only by their disdain for any model of amplifier or speaker that might be owned by more than two other people.
The fact is, there's an archetypal high-end audio sound and an archetypal SET sound. At its best, high-end audio sound is impressive open and clear, with deep bass, shimmering highs, and a flair for thrilling spatial effects: At it's worst, it's lifeless , boring, constricted, undramatic, uninvolving, and incapable of any suggestion of flow in the music.
At its best, SET sound has the kind of punch and drama that can startle you out of your pants - plus real musical drive, momemtum, presence, and tone; at its worst, it has no bass, no treble, and a level of coloration and sheer fuzz that could drive you out of your house after a few songs".