A Picture I have been looking for has finally appeared on Pinterest.

TLS Guy

TLS Guy

Audioholic Jedi
I have been looking for a picture of John Wright's (TDL) last design just before his untimely early death. It is his dual TL speaker.



It is a dual TL. The two bass speakers are actually in one line and the two smaller drivers in the other.

It looks as if someone may still own one of these speakers.

As far as I am aware, the BBC Maida Vale monitors, this TDL speaker and my left and right mains are the only dual TDLs built. The BBC speakers are long dismantled.
 
S

shadyJ

Speaker of the House
Staff member
Interesting looking design. An early WMTMW. Looks like it should have a very broad horizontal dispersion. Potentially very narrow vertical dispersion. I would be curious to know the crossover design and driver performance.
 
TLS Guy

TLS Guy

Audioholic Jedi
Interesting looking design. An early WMTMW. Looks like it should have a very broad horizontal dispersion. Potentially very narrow vertical dispersion. I would be curious to know the crossover design and driver performance.
TDL made really good drivers, and John Wright's crossovers were second to none. That was a really expensive speaker and few were made.

That design was a major part of the inspiration for my left and right mains.
 
Eppie

Eppie

Audioholic Ninja
Now that those bass drivers are in production again, it would be nice if someone posted design schematics. Would have to be a real enthusiast as most collectors would be leery about dismantling a rare vintage speaker. I assume the crossovers would have to be redesigned as the mids and tweeters would be long out of production.
 
TLS Guy

TLS Guy

Audioholic Jedi
Now that those bass drivers are in production again, it would be nice if someone posted design schematics. Would have to be a real enthusiast as most collectors would be leery about dismantling a rare vintage speaker. I assume the crossovers would have to be redesigned as the mids and tweeters would be long out of production.
That is an interesting speaker. I could hardly believed it when that picture popped right up on my feed. The carpentry of that speaker is very complex, so it was easily the most expensive speaker in the world when released. John Wright was the principal designer of the lines for the BBC monitor. Others involved where Peter Walker of Quad who provided the amps that were modified 405 II boards, and he designed the active crossovers. Jim Rogers was also involved as was Raymond Cooke of KEF. As told to me by John Wright, the key to dual lines is to have the F3 of the lines half an octave apart. John Wright died suddenly in 1999 of a heart attack. TDL was sold, as usually happens in the UK to pay death duties. So few of those speakers were made, I do not know how many.

Now those lines were designed before HT and did not allow for the incorporation of the subwoofer feed. In any event those TDL speakers were passive. The other issue is that they were designed before George Augspurger published his landmark paper on TL design in the AES journal in 2000. The landmark piece of that research is that the volume as well as the length of the pipe is crucial. I suspect that John Wright got is close by trial and error. I have never heard those speakers.

Raymond Cooke had a devastating stroke around 1990 and KEF was sold to the Gold Peak Group out of Hong Kong in 1992. Raymond Cooke died in 1995.

Anyhow when I was planning my AV room for the our lake home in the early 2000s I had the benefit of George's work.

I also made the decision that the speakers would be active except the tweeters, I did not thing it justified to employ Quad amps to drive speakers. I wanted a truly integrated full range design, and not have separated subs. I also wanted to include the SUB and LFE outputs. This has been achieved.

Care was taken to minimize phase shifts to preserve coherent sound. The crossover between the two lines is entirely acoustic to preserve phase coherency. The active nature of the speakers allowed me to make baffle step compensation fully adjustable to location.

Of course the elephant in the room with TL designs and especially a full range design is the size of the speaker.

Two of those TDL designs would really fill up a room.
My mains are huge and only fit in with the room specifically designed and built to take them. But they do take in John Wright's precepts for dual lines and take advantage of George Augspurger's enormous contribution.

So, the question becomes: - is it all worth the trouble? In my view it is a resounding yes. The bass quality is noticeably improved by several orders of magnitude, and truly like it really is.

So, I have feel really fortunate to have known and spoken to some of the real pioneers in all this.
 
Eppie

Eppie

Audioholic Ninja
Very fortunate indeed. I wrongly assumed that the TDL would have used George's work. It's interesting that they managed that design without it. While the TDL is large by today's standards, it pales in comparison to your mains. When speakers get that large you really need a dedicated space designed with audio in mind (proper room dimensions). That TDL looks small enough that it would still fit in a retail setting.
 
TLS Guy

TLS Guy

Audioholic Jedi
Very fortunate indeed. I wrongly assumed that the TDL would have used George's work. It's interesting that they managed that design without it. While the TDL is large by today's standards, it pales in comparison to your mains. When speakers get that large you really need a dedicated space designed with audio in mind (proper room dimensions). That TDL looks small enough that it would still fit in a retail setting.
I don't know what it's f3 was but I doubt it was in sub range quite. I would take a guess that f3 was probably around 30Hz, as those bass drivers were closely modelled on the KEF B 139s.

The issue is that if you design a TL and then have a sealed or ported sub, you lose the whole point of it all.

So my mains are larger. The calculated F3 of my bass lines is 27 Hz, however in their location they are dead flat to 20 Hz and not starting to roll off and they achieve high spl.

However, as you rightly point out they are not practical as a commercial proposition I don't think. There must be a lot of interest in TLs in the DIY community. George's program on my website has had thousands of downloads.

My in wall TL though could have commercial application and is a better sub than most. The single 10" Dayton sub driver can easily fill that large space with high quality bass.

I played that in wall system to Squishman recently and he was really impressed with the bass quality.

TLs are being built and sold again by Falcon acoustics.

The bass quality of good TLs is order of magnitudes better quality than sealed or ported alignments.
 

Latest posts

newsletter

  • RBHsound.com
  • BlueJeansCable.com
  • SVS Sound Subwoofers
  • Experience the Martin Logan Montis
Top