[Kevin Warne]

A simple nearfield bass test will tell you whether a company is telling the truth. Some of the TL specs quoted by manufacturers would require huge resonant peaks to get anywhere close to what is claimed for bass extension.

Good point. Keith Howard (Hi-Fi News) actually did this test for our previous model the VS a couple of years ago and it exactly backed up our claims. No you don't need a resonant peak to get good bass extension, just a well tuned cabinet that is designed to extend. The resonant peak of the cabinet is placed low enough in the driver response curve that the combined effect is extension of the flat response region. A badly tunec cabinet will produce a resonant peak and can be used to artificially exaggerate a section of bass, but this is not our approach. The speaker should produce a flat response (in a large enough room) and at the point the response curve does tend to fall off the room itself can be used for extension to some extent. It is important that the room resonant frequency is below the -3db cut-off of the speaker for this to occur or you would indeed get a resonant peak. This is called matching the speaker to the room.

kevin

[Letitroll98]

It is important that the room resonant frequency is below the -3db cut-off of the speaker for this to occur or you would indeed get a resonant peak. This is called matching the speaker to the room.

So one would need to rebuild the home to suit the speaker?  Or is it that the speaker only works well in specific rooms, a subtle difference.  If indeed a 5 1/2" driver in a loaded (stuffed) T-line cabinet achieves sub 30hz bass response in real world environments without severe response peaks I would applaud the designer's skill at defying the laws of physics.  Yes, I'm skeptical.  I'm willing to learn new things, but very little is new in speaker design beyond improved drivers and crossover modeling.

On a side note Kevin, I don't want to deny you the ability to answer direct questions about your product as is allowed for all Industry Participants in the community circles, however you are straying dangerously close to self promotion which is not permitted on this circle.  The bulk of the above post is acceptable so I'll let it stand, but phrases like "Keith Howard (Hi-Fi News) actually did this test for our previous model the VS a couple of years ago and it exactly backed up our claims." and "but this is not our approach." is pushing the envelope.  If you take out those phrases and read your post, that's what we expect of Industry Participants answering questions about their products in the community circles.  Thanks in advance for your cooperation and continued participation on AC.   

[Kevin Warne]

So one would need to rebuild the home to suit the speaker?  Or is it that the speaker only works well in specific rooms, a subtle difference.  If indeed a 5 1/2" driver in a loaded (stuffed) T-line cabinet achieves sub 30hz bass response in real world environments without severe response peaks I would applaud the designer's skill at defying the laws of physics.  Yes, I'm skeptical.  I'm willing to learn new things, but very little is new in speaker design beyond improved drivers and crossover modeling.   

My comment on room size/speaker is general guidance for all speakers. The room/speaker match is important. Of course there are things you can do to alleviate problems such as critical positioning, port stuffing etc. Nothing new here. It is quite interesting that you are taking such a negative view of us and our products. Quite frankly I have no interest in promoting ouselves here, I just wanted to correct some unjustified negative comments and criticism from individuals that now nothing about us or our product, and have indeed never seen or heard it. I shan't waste any more time here as anything that I say that to the contrary is deemed as 'promotion'. It's quite funny actually and very sad as to teh state of the industry in  the USA!

As for our measurements, they are not exaggerated at all. We use 2 such drivers in an array configuration. Severe response peaks, indeed any response peaks are not an issue. Its achieved with correct cabinet damping, driver offset from the top, use of 2 drivers instead of one etc. If you want some evidence that we have achieved this in our design we can provide many references. Email me if you are interested in such info.

Kevin

[Guy 13]

Almost every  manufacturer makes claims that cannot be backed up. Most fall short of what they advertise. Some are funny. www.coconut-audioshop.com/ comes to mind.

Hi geowak and all Audio Circle members.
That link is really funny,
they can't be serious with illarious prices like that.
I have speakers to sell:
They perform like 1,000,000 USD speakers.
They are listed at 500,000 USD
But for a limited time, I will let them go for 9,95 USD
 

Guy 13

[Jim Griffin]

Well, I’m sitting in my Tennessee home listening to my 42” tall by 7.5” wide by 8” deep DIY mass loaded transmission line speakers (MLTL) which have bass response below 35 Hz at the 3 dB down point.  The cabinets have two 4.5” diameter drivers in each box.  According to several responses to this thread, I’m defying the laws of physics, doing the impossible, and polluting my ears with sound peaks, etc.  But I do this daily so I’m not the worst for it.  The music is exceptional so I’m enjoying it.

Some of those who responded need to learn about 21st century loudspeaker design techniques and comprehend what is possible.  Researchers like George Augspurger, Martin J. King, and others have enabled speaker builders and manufacturers to achieve the impossible. Their work can be viewed at these links:

http://documents.jordan-usa.com/Famous-Articles/Augspurger-Loudspeakers-on-Damped-Pipes.pdf

http://www.quarter-wave.com/

Augspurger’s Audio Engineering Society paper and King’s work detail how they developed computer models which accurately model transmission-line loudspeakers.     King’s MathCAD based spread sheets and Augspurger’s software enable users to model performance similar to the Thiel-Small analysis of vented boxes and to build enclosures that agree with theoretical predictions.   Transmission-line speakers can now be derived via sound design techniques using T/S parameters versus previously used cut-and-try methods or other secret mystical means which gave unpredictable performance.

Use of King’s, Augspurger’s, and similar work is spreading within the industry with Salk Audio, Philharmonic Audio, Acoustic Insight, and others offering several MLTL models based transmission-line modeling techniques.  My friend Paul Kittinger has a brief write-up on mass loaded transmission line methods and some simulation results for several of the Philharmonic models at:

http://philharmonicaudio.com/philharmonicaudio/Graph_Pages/bassresponse.html

Using a similar technique, Atlantic Technology offers three products which utilize their H-PAS technology.  H-PAS enables greater extended low frequency range, and/or greater output, with increased dynamic range and impact.

My DIY speakers were designed with Martin King’s spread sheets and I’ve built more than a dozen different MLTL speakers over the past 7 years.   Many of my projects are cataloged on threads on  DIYAudio.com forums.

Jim Griffin

[nickd]

I suppose transmission lines are like all things in audio, they have fans and detractors. I have owned a few T.L. commercial designs TDL and Energy "Ref. Cons." come to mind. I would do NOT judge their bass depth or in room response WITHOUT hearing them first. I have been surprised several times.

I built a 16' long folded 1/4 wave T.L. for a 18" woofer (built in sub) a few years back. It was not an easy process. In fact it took a couple of trys to get the dampening right. It was worth the effort. Crazy powerful subterranean bass.

I am neutral on most loudspeaker design ideas now. I have heard too many good and bad examples of all types of boxes and O.B. designs. A quick listen is all it takes to tell the good from the bad. No amount of "white paper" engineering speak will convince me otherwise. I must say despite the marketing lingo, this design has stirred my curiosity. Makes me wish the brick and mortar stores were still in business to actually hear a pair.

They would do well to hit the shows hard in the US if they intend to sell here, RMAF, Newport, Axpona etc.
People trust their ears.

[Pete Schumacher]

Well, I’m sitting in my Tennessee home listening to my 42” tall by 7.5” wide by 8” deep DIY mass loaded transmission line speakers (MLTL) which have bass response below 35 Hz at the 3 dB down point.  The cabinets have two 4.5” diameter drivers in each box.  According to several responses to this thread, I’m defying the laws of physics, doing the impossible, and polluting my ears with sound peaks, etc.  But I do this daily so I’m not the worst for it.  The music is exceptional so I’m enjoying it.

Some of those who responded need to learn about 21st century loudspeaker design techniques and comprehend what is possible.  Researchers like George Augspurger, Martin J. King, and others have enabled speaker builders and manufacturers to achieve the impossible. Their work can be viewed at these links:

http://documents.jordan-usa.com/Famous-Articles/Augspurger-Loudspeakers-on-Damped-Pipes.pdf

http://www.quarter-wave.com/

Augspurger’s Audio Engineering Society paper and King’s work detail how they developed computer models which accurately model transmission-line loudspeakers.     King’s MathCAD based spread sheets and Augspurger’s software enable users to model performance similar to the Thiel-Small analysis of vented boxes and to build enclosures that agree with theoretical predictions.   Transmission-line speakers can now be derived via sound design techniques using T/S parameters versus previously used cut-and-try methods or other secret mystical means which gave unpredictable performance.

Use of King’s, Augspurger’s, and similar work is spreading within the industry with Salk Audio, Philharmonic Audio, Acoustic Insight, and others offering several MLTL models based transmission-line modeling techniques.  My friend Paul Kittinger has a brief write-up on mass loaded transmission line methods and some simulation results for several of the Philharmonic models at:

http://philharmonicaudio.com/philharmonicaudio/Graph_Pages/bassresponse.html

Using a similar technique, Atlantic Technology offers three products which utilize their H-PAS technology.  H-PAS enables greater extended low frequency range, and/or greater output, with increased dynamic range and impact.

My DIY speakers were designed with Martin King’s spread sheets and I’ve built more than a dozen different MLTL speakers over the past 7 years.   Many of my projects are cataloged on threads on  DIYAudio.com forums.

Jim Griffin

Of course small drivers with the proper TS parameters can go low in a well designed cabinet.  TL or vented makes no difference.  Either can achieve the same low end cutoff with the same drivers.

The real point is whether the stated sensitivity matches up to the stated extension given the TS parameters and box volume.  And of course, small drivers are inherently very limited as to the amount of low bass they can generate without simply falling apart.

[Jim Griffin]

Comment from nickd:  "They would do well to hit the shows hard in the US if they intend to sell here, RMAF, Newport, Axpona etc.  People trust their ears."

For one I know that Salk Audio exhibits at all major shows and have for years.  Their SongTower speakers have been reviewed in Absolute Sound and has been an A-S Editor choice for three years.  See this page from the Salk website:

http://www.salkaudio.com/songtower%20home.htm

Philharmonic Audio has also been showing at major shows for the past couple of years.  Atlantic Technology as been advertising and showing their H-PAS technology products for the past 2-3 years.  Information is out there.

Comment from Pete Schumacher:   

"Of course small drivers with the proper TS parameters can go low in a well designed cabinet.  TL or vented makes no difference.  Either can achieve the same low end cutoff with the same drivers.

The real point is whether the stated sensitivity matches up to the stated extension given the TS parameters and box volume.  And of course, small drivers are inherently very limited as to the amount of low bass they can generate without simply falling apart."

While it is true that most MLTLs have been realized with 4 to 7 inch diameter woofers, as Paul Kittinger points out in his link in my previous post, transmission line speakers trend toward very long line lengths and large cabinets for as driver size increases.   Depending on driver selection, you will find that sensitivities in the low 90s dB SPL and greater than 100 dB SPL at cone peak extension are easily achieved for reasonable sized enclosures as low as 30 Hz. 

Clearly, we are not talking about subwoofer capable performance but the majority of household these days routinely use separate subs for movie sound effect coverage.  The market for 250 pound, bathtub size full range speaker boxes with 15 inch diameter woofers is exceedingly small in the current speaker market.     

[DaveC113]

http://www.theaudiocritic.com/downloads/article_1.pdf

Kevin

 

[Pete Schumacher]

While it is true that most MLTLs have been realized with 4 to 7 inch diameter woofers, as Paul Kittinger points out in his link in my previous post, transmission line speakers trend toward very long line lengths and large cabinets for as driver size increases.   Depending on driver selection, you will find that sensitivities in the low 90s dB SPL and greater than 100 dB SPL at cone peak extension are easily achieved for reasonable sized enclosures as low as 30 Hz. 

Clearly, we are not talking about subwoofer capable performance but the majority of household these days routinely use separate subs for movie sound effect coverage.  The market for 250 pound, bathtub size full range speaker boxes with 15 inch diameter woofers is exceedingly small in the current speaker market.   

Then why use such small woofers and put them in enclosures that try to get below 50Hz if you're using subs?  A sub will be able to better reproduce signals below 60Hz than any 4" woofer can.  Not to mention that asking a small cone area driver to thrash about reproducing low frequencies will necessarily add a lot more distortion in the midrange.

What I meant by sensitivity and extension in a certain enclosure volume is spelled out in Hoffman's iron law, which applies to TLs just like it does to vented enclosures.

Claiming F3 of 29Hz in-room with a sensitivity of 89dB/1W is pretty ambitious, especially after any baffle step correction is applied.  For example, I've used a Vifa NE225W-04 8" woofer in a 1.2 cubic foot enclosure tuned to 33Hz, which will probably do a similar F3 in-room, but it's final sensitivity, after modest baffle step correction, is 89dB / 2.83V or 2W.  That's why the 89dB/1W claim seems mighty inflated to me and others.

Oh, and you'd be amazed how many people ask about 250 pound full range speakers with 15" woofers.   

If you want accurate low end, there's no comparison between a 15" woofer and a pair of 4" woofers.

[nickd]

If you want accurate low end, there's no comparison between a 15" woofer and a pair of 4" woofers.

Agreed.

[MJK]

29Hz @-3dB, 89dB efficiency from what looks like two 4" drivers. Is that possible from any sized box?

http://websites.uk-plc.net/Ultra_Resolution_Loudspeakers/focalstage-floorstander-38825.htm

I have not looked at the design in detail and I do not have a pair of the new Jordan drivers, but looking at the specs and the picture of the speaker I believe that it is possible. If you have only been listening to or designing bass reflex enclosures then an ML TL or a TL may not make much sense. A ML TL or TL uses different physics and can produce deeper bass output from the same cabinet volume as a standard bass reflex enclosure. Getting a TL to dip into the 30 Hz range for a relatively small driver (<= 8 inches) is not that hard or uncommon with the right choice of driver.

[Jim Griffin]

A couple of links on the Atlantic Technology AT-1 MTM speaker which uses their H-PAS technology.  They claim frequency response between 29-20 kHz +/- 3 dB response.  The enclosure size ( ith dual 5 1/4" drivers) is 1.6 cu. ft volume, sensitivity is 89 dB,  and sound pressure levels that exceed 106 dB can be created according to A-T.  They modestly claim that they break the "Iron Law" of loudspeaker acoustics.

http://www.atlantictechnology.com/Upload/PDFs/AT-1-pis-print.pdf

http://www.hometheater.com/content/atlantic-technology-1-loudspeaker-way-we-are

For what is worth, Martin King consulted with A-T on the H-PAS technology.

[Danny Richie]

Really?

Looking at that design you guys question the bass extension?

Did anyone else notice the use of more than one full range driver playing full range with no crossover?

This will cause major cancellation issues from comb filtering effects that will cause 20db swings in the vertical off axis even with small movements up or down. Then adding in a third high frequency driver further complicates matters with even more cancellation effects. The response will be pretty rough.

[Danny Richie]

Good point and couldn't agree more, but it's not just manufacturers unfortunately. The magazines, reviewers and retailers are nearly all in on the game. Common audio lies summarised below:

http://www.theaudiocritic.com/downloads/article_1.pdf

Kevin

There are more lies in that article than truth.

[AJinFLA]

Uh oh,

Another one where I swore I'd stay on the sidelines...but here are those pesky technical claims....again.

A couple of links on the Atlantic Technology AT-1 MTM speaker which uses their H-PAS technology.  They claim frequency response between 29-20 kHz +/- 3 dB response.

Yup. But what does physical reality say?
From your link:


Ok, so let's make that 38-39hz, -3db. And like any reflex, things are pretty much kaput below.

The enclosure size ( ith dual 5 1/4" drivers) is 1.6 cu. ft volume, sensitivity is 89 dB

Right. 90db (avg) measured. But once again, from your link "6 ohms nominal".  Impedance (unfortunately, not shown) 4.2 ohm (min) at 203hz. Oops.
I'd suspect it's more like 4-5 across the midbass, so lets subtract for 1 watt (the way the OP specs theirs).
So we have a 87-88 db (1 watt) 1.6 cu ft speaker with 38hz (-3db) extension. Uh, not doable with a "standard bass reflex enclosure"? Hmmm.

They modestly claim that they break the "Iron Law" of loudspeaker acoustics

I went fishing once and caught this really big......

cheers,

AJ

p.s. let me know when you're coming down next time, missed you the last

[Letitroll98]

Excellent arguments gentlemen, presenting data, arguing your point, not calling into question another's character, system, or hearing.  This is the way all threads with disagreements should go, I applaud you all.   

[Pete Schumacher]

They modestly claim that they break the "Iron Law" of loudspeaker acoustics.

As bugs bunny once said while floating in mid air, "I know this defies the law of gravity, but I never studied law."

[Tyson]

Ported bass sucks, and TL bass is even worse.  Sealed or OB is really the only way to go.  And big drivers.  Hell, a 4 inch driver is barely enough to cover the midrange.  Foghorn Leghorn - that little chicken hawk is out to get you "Lemme at him!  Lemme at him!"

[JLM]

If you listen to artificially created/produced music you can skip this post.

I've been a MLTL/TL fanboy since 1976 when I first heard I. M. Fried Model H (the 'famous' coffin stereo sub, with 8 inch woofer, was rated to 114 dB at 17 Hz).  Bass was fast, deep, and so musical (like no horn, OB, sealed, or ported speaker I've heard in 40 years).  The Model H was responsible for 2 of maybe 4 major audio epiphanies (3D imaging and 'real' bass) I've ever had and sent me directly into a 'serious' audio direction where recreating un-amplified music is the goal.