Considering Transmission Line

[TLS Guy]

Nothing like resurrecting an old thread

I have a pair of the 3" Tang Band Bamboo full range (if you can call them that) drivers WS-1364SA in a ported box tuned around 86 Hz. This was my first speaker build ever. I run them with no crossover and they sound pretty good, although the upper end gets a little harsh when pushed and they are definitely not an spl driver. I find these best to listen to nearfield at low to moderate volume and I really like the natural sound they have.

I came across this article: http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf that talks about the TABAQ (TAng BAnd Quarterwave) and thought maybe I should try a TL enclosure for my bamboo drivers.

Of course I have to consult the audio wizards here at audioholics before I embark on any audio adventure. What do you think? I think mostly I'm itching to try something new that doesn't cost any money (or very little!).

That pipe is far from optimal and I have reviewed it previously.

Problems.

The pipe is straight and therefore the driver is helped over a narrow frequency range. Tapering would augment output over a larger frequency range.

The pipe is not folded, which will result in too much HF output from the port.

Adding extra volume well make Qt unnecessarily high, and be like a poorly tuned reflex.

G.L. Auspurger has shown that uniform stuffing is superior to non uniform stuffing. In an optimally tuned TL the line is damped to produce one tuning hump, then roll off will be second order, and you will have even more lower bass.

If you taper and fold the line you will have a more compact enclosure, and it will be to a large extent self bracing.

If you PM your Email. I can send you Auspurger's papers he presented at AES.

That driver though small should be capable of good TL performance.

Quarter wave pipe loading was first described by Paul Voight back in the thirties. However he knew enough to taper the pipe. Things have progressed a lot since then. Although a Voight quarter wave pipe as Voight described it, can work surprisingly well. The first enclosure I ever built was a Voight quarter wave, and the second and third. The state of the art has progressed though, and built on Voight's pioneering work.

[audiofox]

That pipe is far from optimal and I have reviewed it previously.

Problems.

The pipe is straight and therefore the driver is helped over a narrow frequency range. Tapering would augment output over a larger frequency range.

The pipe is not folded, which will result in too much HF output from the port.

Adding extra volume well make Qt unnecessarily high, and be like a poorly tuned reflex.

G.L. Auspurger has shown that uniform stuffing is superior to non uniform stuffing. In an optimally tuned TL the line is damped to produce one tuning hump, then roll off will be second order, and you will have even more lower bass.

If you taper and fold the line you will have a more compact enclosure, and it will be to a large extent self bracing.

If you PM your Email. I can send you Auspurger's papers he presented at AES.

That driver though small should be capable of good TL performance.

Quarter wave pipe loading was first described by Paul Voight back in the thirties. However he knew enough to taper the pipe. Things have progressed a lot since then. Although a Voight quarter wave pipe as Voight described it, can work surprisingly well. The first enclosure I ever built was a Voight quarter wave, and the second and third. The state of the art has progressed though, and built on Voight's pioneering work.

Does the taper act as a horn for the TL, ie, acoustically amplifying the sonic energy (almost like a venturi effect)?

[TLS Guy]

Does the taper act as a horn for the TL, ie, acoustically amplifying the sonic energy (almost like a venturi effect)?

No it does not. It possibly has a slight effect in the classic Voight Quarter wave pipe, but not in the aperiodic reverse tappered line.

A horn needs a box, throat and then an exponential, parabolic or tractrix expansion. In a horn F3 is dictated by the size of the opening and not the length as in a pipe.

Horns and pipes are quite different in terms of physics, but a lot of DIY designers seem to get their physics confused.

[roline]

I was fortunate to have been exposed to TL speekers in the 70's out in California. IMF Studio monitors and the larger TL's with the B139 woofer. I'm slowly aquiring kef units to build a pair for the left /right units for the plazma entertainment center. A couple yrs ago I build a set for computer monitors, I spend too much time on the computer to not have a decent set of speakers to listen to while surfing or doing cad.... All the work is worth it, folds, stuffing and achieving the tapered length. The IMF's are still my favorites...

[TLS Guy]

I was fortunate to have been exposed to TL speekers in the 70's out in California. IMF Studio monitors and the larger TL's with the B139 woofer. I'm slowly aquiring kef units to build a pair for the left /right units for the plazma entertainment center. A couple yrs ago I build a set for computer monitors, I spend too much time on the computer to not have a decent set of speakers to listen to while surfing or doing cad.... All the work is worth it, folds, stuffing and achieving the tapered length. The IMF's are still my favorites...

This is the old IMF.

Here is the Hi-Fi News design

There is a lot of nice old gear of the period here.

I think the KEF B 139 is a great driver and a classic for TLs. I would not use the KEF B 110. Bextrene ages and they are now cracking. Bextrene is no longer produced.

I have some KEF T 27s I can make available to you, however it is pre ferro fluid and outclassed by more modern units. The Celestion tweeters are now failing with no repair possible.

I doubt you will find any Coles/ITT super tweeters. I used to have a pair of those, but eventually the voice coils separate from the poly dome.

So by all means use the B139, but use modern mids and tweeters. You will need redesigned crossovers.

My rear speakers use the B 139 in TLs.



KEF B 139 in three way bass reflex.



Right and left dual TLs with SEAS Excel drivers and center TL with SEAS prestige drivers.

[Guiria]

I found this style of TL speaker for the Tang Band W3-871S


I own the WS-1364SA but I have found a couple of posts on the net where people have tried the WS-1364SA in enclosures designed around the W3-871S and they said it sounded 1:1...could not tell a difference. Now I know I really go out a limb here by basing a whole build off of a couple of forum posts from strangers, and not even audioholics at that.

Since I am in no build mode on my main system for the time being I thought about throwing a set of these together and seeing how they sound. These speakers are currently in a smaller 2 channel, non-audiophile setup

...what do I have to lose besides a little time and mdf, besides I could use a project, all I do in the evenings these days is watch TV.

[Bjohannesen]

Hi TLS Guy, i found the thread and I would like to comment on my design.

TABAQ is a straight pipe with two sections, with the last part having a much smaller cross section.

Distribution of stuffing is calculated by the use of MJK´s spreadsheet.

The unwanted HF output from the driver is tamed by stuffing and the location of the driver in the pipe.

The large volume of the cabinet is to increase the wanted bass output from the opening.

TABAQ is performing very well with the 3" driver. I have, however, replaced the driver with a TB 4" for more SPL.

I have made a foldet book shelf version, called TABAQ BOX and is about to build a prototype of TABAQ MICRO with TB 2" ! Not hi-fi but fun-fi.

TABAQ is not ment to be a high end solution, but a simple design with good SAF, low cost, no "boom bass". The result is not bad at all :-)

Hope this cleared up things a bit.

Build it and have fun !

Hi from Wonderful Copenhagen

[Texun1]

I have a pair of DCM TimeFrame 600's and they sound very good. The Bass that comes from those 2 6" woofers is impressive. It has to be the tranmission line concept.

[GranteedEV]

Martin King uses a different TL, what he calls a mass loaded TL. He himself acknowledges the controversy as to whether they are TLs or not. I personally regard them as a variety of coupled cavity reflex, with some features of the Vopight quarter wave pipe.

Martin King's software similates both types of TLs, as well as many other quarter wave resonators as well as open baffles. There is a separate worksheet for Open Ended TL, Closed End TL, TQWT, ML-TL, Backloaded Horn, Open Baffle, U-Frame, and H-Frame. In fact most of these have two or three worksheets, with varying degrees of precision.

What it does show, however, is that regardless of whether something is pure bass reflex, mass loaded transmission line or tapered transmission line, or straight transmission line both will eventually roll off at 24db/octave and lose control of driver motion.

The tapered TLs will generally have a shallow rolloff towards a so-called tuning, so the eventual rolloff is less conspcious.

The ML-TL (or standing wave optimized bass reflex, whatever you wanna call it) will be virtually flat towards its knee and then the hard rolloff will be of course more evident.