Small Full Range Driver in TL for office

[TLS Guy]

@TLS Guy This is really fascinating. If I understood correctly the two drivers are not playing the same signal?

I'm going to come forward and just say what's on my mind; long time ago you mentioned a DIY competition that also has a category for less skilled builders who use some proprietary parts in building their projects. From that moment on I kept wondering how would a TL speaker sound using the UniQ from LS50:
View attachment 34912

But going for the full range sound in an enclosure like this one:
View attachment 34913

First of all you are correct that the drivers are not playing the same signal. However they are playing the same signal at the range that the pipe is operating. If that were not the case, then it would not work. However the lower driver is 'shelved' to provide the correct amount of baffle step compensation. The upper tweeter is providing a fill in signal. Mainly it is providing for a fill in dip in response at 9 KHz.

Now as to using the KEF driver you state, I have considered buying a couple of speakers to get the drivers. However, I'm worried I would buy them, measure them, and find that they were not suitable for TL designs. So I stuck with the SEAS drivers which are a well known entity and it worked out very well.

The full rangers you show are classic horns, Lowther fashion.

Here are the specs from one of the ranges of Lowther speakers for horn loading. Note that the sensitivity is very high and the flux densities enormous. The Qts is very low. It is these features that make them the most suitable for horn loading then any other drivers on the planet.

Back when I was kid and pre Thiel/Small and long before computer assisted design, if you wanted really good sound in the home, your option was basically Lowther and then Lowther or Quad ESL after its introduction. The rest in the main were pretty awful. The Wharfedale Airedale getting just about a passing grade also.

Lowther PM 6 from the fifties era.

Original Quad ESL and amps from the mono era

Wharfedale Airedale

It is so important to remember where we came from in all of this.

 

[adwilk]

Yes, my center line TL uses two SEAS prestige coaxial drivers.

The lower speaker is fed from one channel of a Quad 909. The top driver, uses a modified for purpose Shure SR 106 crossover feeding the other channel of a Quad 909. This signal provides active continuously variable BSC. These drive units from SEAS are based on an older KEF design and built under license from KEF. They do have a response irregularity in the 9 KHz range and above. The tweeter of the top unit is fed a correction signal for this problem. Others have found it a problem to get a really pretty much perfect response from these units. I have managed through a number of iterations of the electronics to get a really good response from this center speaker. This proved to be the most difficult aspect of the whole design of this novel TL speaker system.

Ok, I can see how the Shure SR106 would be used for BSC- I am curious how it was modified, though, and what frequency range do you start to roll off? I'm guess thats the mod, because the optional factory points wouldn't be ideal. So I'm understanding correctly- is the center channel signal split from the source? Then one coaxial driver amplified with passive xover- then the other coaxial driver has active correction with BSC and tweeter correction- then does that speaker also use passive xover? How is the tweeter correction applied? is that active or part of the passive xover? Complex for sure, but impressive results. I'm curious also about the Shure's performance VS today's best DSPs. It must be a pretty special unit. Seems to me a modern DSP would be much easier to dial in.

It raises what a probably fairly elementary questions from me. Based on some of your correction approaches- active BSC being one of them- where's the threshold for full active xo overcoming a mildly improperly aligned TL, Horn or even more traditional "box" enclosure? It seems to me that if a driver is capable, then active eq could overcome a bunch, no? Also curious- if you "set" an active xover as close as possible to a passive counterpart, would the speaker sound much the same or what would vary? Could you reliably use active xo to design passive xo?

EDIT TO ADD: Also- why two drivers? Just for efficiency/output? In a smaller setting, a single driver would produce good results if the appropriate corrections were applied to the single driver?

 

[killdozzer]

To use this extra quarantine-given time, please give me a link to pics and info on TL speakers. (Sure, I can google, but I'm asking you to filter it out so that I don't stumble upon someone who doesn't know his stuff)

 

[TLS Guy]

Ok, I can see how the Shure SR106 would be used for BSC- I am curious how it was modified, though, and what frequency range do you start to roll off? I'm guess thats the mod, because the optional factory points wouldn't be ideal. So I'm understanding correctly- is the center channel signal split from the source? Then one coaxial driver amplified with passive xover- then the other coaxial driver has active correction with BSC and tweeter correction- then does that speaker also use passive xover? How is the tweeter correction applied? is that active or part of the passive xover? Complex for sure, but impressive results. I'm curious also about the Shure's performance VS today's best DSPs. It must be a pretty special unit. Seems to me a modern DSP would be much easier to dial in.

It raises what a probably fairly elementary questions from me. Based on some of your correction approaches- active BSC being one of them- where's the threshold for full active xo overcoming a mildly improperly aligned TL, Horn or even more traditional "box" enclosure? It seems to me that if a driver is capable, then active eq could overcome a bunch, no? Also curious- if you "set" an active xover as close as possible to a passive counterpart, would the speaker sound much the same or what would vary? Could you reliably use active xo to design passive xo?

EDIT TO ADD: Also- why two drivers? Just for efficiency/output? In a smaller setting, a single driver would produce good results if the appropriate corrections were applied to the single driver?

Yes, two drivers, as one would not have enough power to match the mains which have prodigious power. Also this technique of using a "fill driver" is commonly done and a good idea as it keeps down cone excursion. These are known as 2.5 ways. My surrounds are 2.5 ways.

Finding the correct frequency and orders, takes some research and trial an error. The center works well with first order starting at 250 Hz, that being the 3 db down point.

The mains on the other hand required staring at 200 Hz and a transition to second order around 500 Hz. I just had to go by a bit of trial and measurement on this. The old SR 106 crossover are very open and discrete transistor with not a chip in sight. Changing the crossover and slopes is quite simple and actually explained in the user manual! How things have changed. A manufacturer actually telling you to open up a units and solder in different components. The changing order was a little more difficult but not bad.

So the lower driver is crossed to the tweeter with a passive crossover at 2.5 KHz. The upper tweeter EQ circuit is also fed from this channel and is passive.

The lower speaker amp channel is fed from the unbalanced RCA out. The upper fill driver is fed by the center balanced out to the Shure SR 106. That make is very simple. There is a mono pot in my amp controller between the Shure SR 106 and the Quad 909.

That is all there is to it.

The mains are much more complex. The smaller lines use the unbalanced signals. The balanced out puts go to the Shure SR 106 units for the left and right. The outputs go to the upper 10" driver and again a pot is used this time a dual ganged one to set the BSC. However this is where it gets complicated. The unbalanced sub out goes to the lower 10" driver. The balanced sub outs go to buffer amps. Then a mixing circuit combines the sub out with the BSC from the Shure SR 106 from the output of the control pot. This did take some getting right. But right it all is and works very well indeed with spectacular results.

 

[TLS Guy]

To use this extra quarantine-given time, please give me a link to pics and info on TL speakers. (Sure, I can google, but I'm asking you to filter it out so that I don't stumble upon someone who doesn't know his stuff)

I can give you links to my speakers if you want. There is not a lot of GOOD information on the net, very little in fact. There is an enormous amount of bad information.

The math is fairly complex. Fortunately Gearge Augspurger shared his design software with me. He was with Harmon Kardon at the time and published it all in the AES journal.
This has been a real joy, as it is hard to eyeball the specs of a driver and have a good idea whether it will work or not in a TL. One of the big problems, is that you end up running a lot of models to find ones that are truly suitable. I did not have this software when I designed my speakers in the AV room. They were designed largely on 2005 and built 2006. I obviously did have his software when I designed the in wall sub TL in my wife's system.

I'm actually busier than you might think at the moment, mainly because my wife is recovering from a total foot reconstruction and it has been tough going.

 

[killdozzer]

I can give you links to my speakers if you want. There is not a lot of GOOD information on the net, very little in fact. There is an enormous amount of bad information.

The math is fairly complex. Fortunately Gearge Augspurger shared his design software with me. He was with Harmon Kardon at the time and published it all in the AES journal.
This has been a real joy, as it is hard to eyeball the specs of a driver and have a good idea whether it will work or not in a TL. One of the big problems, is that you end up running a lot of models to find ones that are truly suitable. I did not have this software when I designed my speakers in the AV room. They were designed largely on 2005 and built 2006. I obviously did have his software when I designed the in wall sub TL in my wife's system.

I'm actually busier than you might think at the moment, mainly because my wife is recovering from a total foot reconstruction and it has been tough going.

Well thank you most sincerely. I didn't know about your wife and I was looking for something to keep me busy, not you. Best of luck to your lady and a swift recovery.

No rush, when you have the time please give me whatever you can. The worst thing that can happen is to sprain my brain!

Thanks again.

 

[TLS Guy]

Well thank you most sincerely. I didn't know about your wife and I was looking for something to keep me busy, not you. Best of luck to your lady and a swift recovery.

No rush, when you have the time please give me whatever you can. The worst thing that can happen is to sprain my brain!

Thanks again.

Here is the build album you wanted.

 

[killdozzer]

Here is the build album you wanted.

Again, nothing short of fascinating. Short of tuning, XO and drivers, going by box alone it's the opening that gives it away, right?

Did Lowther offer TL DIY kits (or any other company for that matter)? I guess that would be very difficult without knowing which driver will be used, right?