Nominating 8' DIY Voight Tube for test

[folzag]

For those that haven't heard of him, Tech Ingredients might be the interwebz' East Coast to @amirm West Coast.

He's a 21st century Mr. Wizard. You couldn't do it today on broadcast TV, but there's still an audience for hard science content paced to teach and inform rather than dazzle and show-off, and of course YouTube fills the need.

On the audio topic, he's done a couple of videos on DIY panel speakers, built his own anechoic chamber to measure them, and then built his own pair of Voight tubes.

Anyone planning a road-trip from Vermont to Washington?

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[CrowDaddy]

This guy is great! Thanks so much for introducing him to those of us who hadn't known.
As speaker nerds may know, Cain & Cain in Walla Walla made highly-regarded Voigt tube speakers, called Abbys, with single Fostex drivers.
Carl Blumenstein apprenticed with Cain ( who passed away a few years ago ) and runs Blumenstein Audio.
A good documentary was made about his speaker manufacturing operation:

Blumenstein recently moved from Seattle to Tennessee, taking a couple pair of B-stock Abbys with him which are for sale.
He plans eventually to manufacture his own version.

 

[cavedriver]

Bumping this thread because I just discovered this guy and because I've been looking for an affordable ~95dB speaker to go with a Coincident SET amp (so ~8 W/channel). I could buy the Coincident speakers, or any of a variety of 10k+ speakers by Devore, Zu, Klipsch, Audio Note, and others (I have original Snell E/III's so I'm familiar with their strengths and weaknesses), but at <1k in materials and some interesting performance claims, I am truly fascinated enough by these speakers that I might bother to build a pair. The question is, who has actually heard the design??

 

[mightycicadalord]

This guy is great! Thanks so much for introducing him to those of us who hadn't known.
As speaker nerds may know, Cain & Cain in Walla Walla made highly-regarded Voigt tube speakers, called Abbys, with single Fostex drivers.
Carl Blumenstein apprenticed with Cain ( who passed away a few years ago ) and runs Blumenstein Audio.
A good documentary was made about his speaker manufacturing operation:

Blumenstein recently moved from Seattle to Tennessee, taking a couple pair of B-stock Abbys with him which are for sale.
He plans eventually to manufacture his own version.

Whoa why are they asking $2000-$4000 for some GRS woofers?

 

[DanielT]

With the right type of speaker driver plus the right amount of stuffing, damping in them maybe. But with a crappy bass driver it turned out like this for me:

Page 2, #37 in this thread:

Post in thread 'ND25FW-4 , tweeter. What are + and -? Red-black?'

Sep 14, 2025

I got a couple of old empty transmission line speakers* boxes for free (no one wanted to buy them so the seller gave them away, thanks for that)
I have a couple of low power 8 inch vintage bass drivers, with pitiful small magnets, probably pretty high Fs and so on that were suitable to mount directly in the TL boxes. Tweeter, the subject of this thread, ND25FW-4 I mounted in them. They also fit directly in the TL boxes.

I use an active crossover for this test. Crossover point set to 2.6 kHz (24 db L-R filter). It fits with the C-C distance bass - tweeter. Plus you probably shouldn't...

• DanielT

By the way the black Voight pipes I got have exactly this construction:


That construction, it's the same speaker as in the picture above in the video below, with SB's eight inch full range driver. There's probably potential. Given the price of that full range driver in particular, it costs around $40.

 

[mhardy6647]

For those who wish to do web searches and whatnot: the design(s) we're discussing are named for Paul Gustavus Alexander Helm Voigt (no "h" in his surname). https://www.lowtherloudspeakers.com/paul-voigt

The rest is just my typically egocentric rambling - offered strictly FWIW.
One of the nicer pairs (to listen to) of DIY loudspeakers here are folded, mass loaded TQWTs loaded with modest but redoubtable Radio Shack twincone "full range" drivers. Bob Brines designed the enclosure, my friend Mike Berg built mine. I installed the drivers. (gotta play to one's strengths, you know?).








TQWTs (tapered quarter-wave tubes, aka "Voigt tubes" or "Voigt pipes") are interesting - sort of mimicking the design of a pipe organ pipe but tuned and tweaked to spread out the resonance(s). Some black magic art is generally invoked for the choice of material and arrangement of "stuffing" for the pipe, but there's legitimate physics in the design, too.
see: http://www.quarter-wave.com/

see, e.g., https://www.diyaudio.com/community/threads/rs-40-1354-suggestions.311129/

The late Terry Cain's TQWTs are good but 1) somewhat physically imposing (folding, as above, helps in that regard) and, 2) to my ears and taste, suffer a bit from the choice of the rather piercing Fostex drivers that were generally installed in them.

Then again, if any of y'all've ever heard a pair of Lowther "fullrange" drivers -- well... I think they may be called out by name as being proscribed in the Geneva convention.

 

[mhardy6647]

The Abbys, since I neglected to mention it previously, were typically loaded with Fostex FE166E twincones. Those (and their larger siblings, the FE206E) were always a little too zingy for me.

 

[cavedriver]

Then again, if any of y'all've ever heard a pair of Lowther "fullrange" drivers -- well... I think they may be called out by name as being proscribed in the Geneva convention.

Not sure I'm following you- are the Lowthers good or bad? And in what way? I've never heard them but am extremely pessimistic that they will come anywhere close to linear and I assume all the draw is in their point source behavior.

 

[mhardy6647]

They are very lively and with some recordings they can be spine-tinglingly real sounding. Unfortunately, with complicated music (e.g., symphonic) and/or with over-processed (e.g., '80s pop) music, they get shrieky. The term of art is the "Lowther shout", but this expression oozes with traditional British understatement.

Not sure I'm following you- are the Lowthers good or bad? And in what way? I've never heard them but am extremely pessimistic that they will come anywhere close to linear and I assume all the draw is in their point source behavior.

 

[mhardy6647]

They are very sensitive (in both senses of the word ) , very finicky, very expensive, and not very flat. They make the heritage Klipsch loudspeakers sound polite.

See, e.g., "the 98 cent Lowther tweak".

FR taming tricks

I just bought some old CHEAP FR drivers with a wizzer. Not much good but much better after coating the paper with a couple of coats of PVA, they are a bit harsh at the top end, I remember dave/planet10 had a trich with winding soft wool around the base of the wizzer but can't find the link or...

www.diyaudio.com

 

[DanielT]

The Infinity bass drivers I popped into the black TQWT/Voigt pipes is from a pair of Infinity 1500e speakers. 1500e, sealed speakers of around 35 liters. I have checked the bass response with the Infinity 1500e and they roll, as per the specs, off around 75 Hz.
I know what the low bass FR looks like in my listening room via my Yamaha subwoofers (f3 23 Hz). A peak around 30 Hz, valley around 60 Hz and peak around 80 Hz.

Now I measured, via very rudimentary apps, a sweep (20Hz-120 Hz) with the Infinity bass drivers in my TQWT/Voigt pipes. This is what it looks like:

The same FR in the large TQWT/Voigt pipes as in the original Infinity 1500e boxes they were in.

However, short stroke/ small x-max, high FS probably mean that the bass driver works more evenly higher up in frequency (I haven't measured that yet).
Mid to tweeter (with WG..ND25FW-4 is a superb tweeter, especially considering its low price) ok/good. As good as it gets with an 8 inch woffer and a 1 inch tweeter.

The bass driver also doesn't seem to have any nasty break ups. Plus fairly high sensitivity. BUT roll off around 75 Hz! I mean why such big speaker boxes in that case? Quite unnecessary.

Any smaller "standard" bookshelf speaker can handle that. Small speakers that takes up much less space.

With all that said. In my TQWT/Voigt pipes defense, with a suitable/good bass driver for them it could probably be better. Result in lower bass FR that is.

 

[DanielT]

I missed to say this in my last post:
Even though I don't see any difference in FR, sealed 35 liters vs TQWT/Voigt, I experience the bass as better in the TQWT/Voigt. Higher sensitivity yes, but beyond that I don't know what it is due to. Lower distortion? Even though the bass doesn't go far down in frequency, it feels like "heavier" with the TQWT/Voigt construction, bass with a little more punch.

Maybe it's the TQWT/Voigt construction itself that brings some bass advantages?

Edit:
Another slight difference is how steeply they roll off down frequency. The seald exhibits typical seald roll off patterns.

Edit 2:
Speaking of matching speaker drivers for . Here is exactly the type of design on the TQWT/Voigt pipe that I have with Visaton 20BG broadband elements:

And here again. The same TQWT/Voigt pipe but with 8″ SB20FRPC30-8 broadband elements.Seems to have potential:

 

[DanielT]

With a pair of old Seas 21 REX DD bass drivers plus the exhaust covered a bit I managed to get it down to f3 around 53Hz-50Hz. Which would be okay for a pair of bookshelf speakers, but these are fairly large speakers so not really great. Or on the verge of being ok. It would have been nice with f3 at 40 Hz, even better at best 35 Hz but for now it is what it is.

The advantage of the Voigt pipes is the nice bass sound, which I have a hard time describing what it is that is appealing about it. There is something.


Seas measured in many cases in 20 liter sealed boxes in the past. So they did with the Seas 21 REX DD. Hence the bass response in that graph:


Edit:
Dual Peerless SLS 10 in those 78 liter boxes, sealed then would probably give better bass. It would also allow for EQ or

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in the bottom, which now considering how they roll off so extremely steeply, is impossible. But I don't know if I want to saw the boxes apart. It's mostly just a thought.

An SLS or two con to con isobaric in those speaker boxes that the active crossover and the receiver are on in the picture above however. I'll see what I do.