Acoustic Transmission Line Speakers ??

[GranteedEV]

Modelled impulse response:

TL

Sealed

ML-TL

 

[LAB3]

To this date, no one has ordered a pair of 1's. So I've pretty much given up on them. But I have the cabinets and will certainly sell them to anyone who wants them. People just seem to want the RAAL tweeter, and are willing to pay an extra $400 to get them. To clear up a couple of other misconceptions, the
HT2 TL is hardly an inefficient speaker. It's quite sensitive, and can easily be driven by an amp with a solid 60 watts of power. I've heard them play nicely with a 35 watt tube amp. More power might be better, but it's not a necessity.
They're just as sensitive as the SongTower, which is an extremely easy speaker to drive. Are the Salks and Philharmonics transmission lines? Yes. They are mass loaded transmission lines using precise mathematical models. They function far more effectively in harnassing the quarter wave than most older classic designs without mass loading. We've been down this road many times. At some point it becomes a matter of semantics, and what counts is performance.

Thanks for posting about the TL information on SALK and Philharmonics.
Louis

 

[LAB3]

I was reading the Paul Klipsch learned about his "Transmission Lines and Wave Filters" from Dr. F.E. terman from Stanford in 1933. I need to Google Dr. Terman and read his article on this vs the designs being used now by Philharmonic and SALK.

 

[TLS Guy]

Paul Voight has to get the credit for first loading a speaker with a pipe.

After the war, Ralph West and Dr Bailey picked up the mantle.

The reversed tapered aperiodically damped lines grew out of work done at Radford, by Bailey, John Wright, and Irving M Freid.

There were very successful designs from Radford, IMF and especially from TDL as a result of this work. PMC continues that tradition today.

Unfortunately for reasons I will never understand there is confusion in the minds of many between horns and pipes.

This whole business of mass loaded TLs has confused the situation even more and defeated the whole foundation of the reasons behind the aperiodically damped line, which is critically damped.

The we get the total nonsense, that once the pipe is critically damped, there is no port output.

Well as I posted above, my lines are critically damped as proved by the impedance curve. However drive a tone at reasonable volume in the range at which the line supports the driver and it blows out a propane lighter flame! They really connect to the room.

Mass loaded lines are not critically damped as seen by the impedance curve.

Further a resonant port will not give the driver such wide bandwidth support as a reverse tapered aperiodic line.

Also the mass loaded line flies in the face of the physics of the line.

One of the big advantages of stopped pipe is that pressure is very high towards the closed end and air displacement (air movement) is low. At the closed end air displacement is zero, which is obvious.

At the open end pressure changes are zero, but air displacement is high.

This is exactly what is required. This produces reduced and controlled cone displacement and couples the drivers to the room efficiently with large air displacement. And boy do my lines couple to the room without bloom.

Now when you put a resonant ported chamber at the end of the line, you are converting the end of the line to a high pressure zone.

I will never accept the mass loaded concept as a TL, in the way the original developers conceived it. And some of them I knew, especially those involved in the legendary BBC triamped TL monitors which also came out of that work.

 

[LAB3]

Mark............ that is a lot to take "In" more "Light" reading to do.... I had to think about a Quater Wave Horn was a Voigt "PIPE" or TQWT as it was called. it shows you spent a lifetime learning all this.
Regards
Louis

 

[GranteedEV]

This whole business of mass loaded TLs has confused the situation even more and defeated the whole foundation of the reasons behind the aperiodically damped line, which is critically damped.

The graphs I posted speak for themselves. There was about 2-3db of lift between 25hz and 100hz in the critically damped "true" Transmission line from about 25hz to 130hz and then rolls off 24db between 12hz and 24hz.

The mass loaded line shows at least 2db of lift between about 20hz to 70hz give or take, including a much larger ~9db boost in efficiency at about 25hz. In the teen frequencies its response becomes identical to the damped line.

So what you've got from a critically damped line, is a smoother frequency response which may work better in some rooms.

...something which you can more effectively tackle with active equalization, while also realizing the 7db more gain near the tuning.

Mass loaded lines are not critically damped as seen by the impedance curve.

But the question is "so what"?

Further a resonant port will not give the driver such wide bandwidth support as a reverse tapered aperiodic line.

But does it really matter with today's upper-end highly linear, klippel optimized drivers? Does an 8" driver get pushed anywhere near limits at 70hz?

The only place I can see this as being a relevant advantage, are with inexpensive or dated drivers. But then that begs the question - are you really saving much money given the box size requirements?

And boy do my lines couple to the room without bloom.

That's great. And in another room the ML-TL can still "couple" better. There's no one set solution.

I will never accept the mass loaded concept as a TL, in the way the original developers conceived it.

That's fine. The reason being that it doesn't really matter if it's a TL or not - the means should not justify the ends. And likewise, despite the constant claims, I will never accept the TL concept as being a 2nd order system, which is one of the biggest so-called advantages, unless you've got ground plane 5hz to 100hz measurements. It's a pseudo-second order over some of its passband yes, but whether it's pros are justified is debatable. A 2 - 3db lift over its intended passband, and then a sharp rolloff below that.