I wonder if high Q drivers could profit from a more damped TML than usually constructed.
The aim would be a low resonance frequency and lowering the Q at the expense of output from the line.
Did anyone try this out? Or is there no benefit of a damped TML against other designs for putting Q down like Variovents (resistive damping techniques).
If the principle of a damped TML would keep resonance frequency low and lower the Q at the same time would it be better than a closed box with a variovent of same size?
I never built TMLs and have no simulation programs but maybe there are already analysis on this.
Would simulation programs simulate correctly the properties of damping material and the grade of damping inside the line like 60 / 80 / 90 / 100 per cent?
Like Hornresp or
The aim would be a low resonance frequency and lowering the Q at the expense of output from the line.
Did anyone try this out? Or is there no benefit of a damped TML against other designs for putting Q down like Variovents (resistive damping techniques).
If the principle of a damped TML would keep resonance frequency low and lower the Q at the same time would it be better than a closed box with a variovent of same size?
I never built TMLs and have no simulation programs but maybe there are already analysis on this.
Would simulation programs simulate correctly the properties of damping material and the grade of damping inside the line like 60 / 80 / 90 / 100 per cent?
Like Hornresp or
No need for heavy stuffing inside TL, moderate stuffing is enough for high Qts. You must use simulation, like HornResp or SpicyTL.
High Qts drivers work best in TL. Variovent box is better than closed box, but both are worse then TL.
I wonder.
They say high Qts woofers are best used in sealed enclosures or open baffle.
But these 2 examples are in horn speakers
Mauhorn
? AC-2B Qts .73
http://www.audiodesignguide.com/Fullrange-Speakers/Fullrange-Speakers_project.html
--------
Viech Horn
Beyma 8AG/N Qts 1.15
http://www.einklang-audio.com/treiber/beyma/8agn.pdf
https://www.hifi-selbstbau.de/images/stories/forentreffen/ViechTreff2009/DasViechNeu.pdf
https://www.jogis-roehrenbude.de/LS-Box/Berndt_Burghards-Viecher/Viech.htm
"The horn
According to earlier common doctrine, a driver with QTS of over 1 is completely unsuitable for a horn, and the high resonance frequency of a good 100 Hz certainly does not make you think of a full-range operation without additional bass support. The realization that it works is only possible through such sophisticated simulation programs as AJHorn, which I also used to construct the crit. Two prerequisites are necessary for this trick to work:
The crum is a horn with an exponential contour, a barrel length of 2 meters, the neck cross-section is 150 cm2, the mouth cross-section 1250 cm2. Depending on the room, this allows a lower limit frequency of 50-60 Hz."
Google Translate
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They say high Qts woofers are best used in sealed enclosures or open baffle.
But these 2 examples are in horn speakers
Mauhorn
? AC-2B Qts .73
http://www.audiodesignguide.com/Fullrange-Speakers/Fullrange-Speakers_project.html
--------
Viech Horn
Beyma 8AG/N Qts 1.15
http://www.einklang-audio.com/treiber/beyma/8agn.pdf
https://www.hifi-selbstbau.de/images/stories/forentreffen/ViechTreff2009/DasViechNeu.pdf
https://www.jogis-roehrenbude.de/LS-Box/Berndt_Burghards-Viecher/Viech.htm
"The horn
According to earlier common doctrine, a driver with QTS of over 1 is completely unsuitable for a horn, and the high resonance frequency of a good 100 Hz certainly does not make you think of a full-range operation without additional bass support. The realization that it works is only possible through such sophisticated simulation programs as AJHorn, which I also used to construct the crit. Two prerequisites are necessary for this trick to work:
- A frequency response of the driver increasing in the midrange
- A horn without a forechamber
The crum is a horn with an exponential contour, a barrel length of 2 meters, the neck cross-section is 150 cm2, the mouth cross-section 1250 cm2. Depending on the room, this allows a lower limit frequency of 50-60 Hz."
Google Translate
https://translate.google.com/?sl=auto&tl=en&op=translate
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It makes plenty of "logical sense" to use a high Q woofer in a highly damped TL, and in the 80s when I was a teenager building speakers that's exactly what I did - I used Morel 9" woofers with a Q of 0.8 in a box with a fair bit of stuffing. When I measured the impedance curve, what I saw was a highly damped broad resonance. The woofer appeared from the impedance curve to have a Q of about 0.6. So what I ended up with resembled an acoustic suspension design with a lower QB than the original QT of the woofer.
However back then, I would have needed really special computer modeling skills to actually model a TL and I didn't really know what I was doing. I made the best of the limited tools I had at the time.
The articles in speaker builder claimed that a TL was a non-resonant enclosure. That non-resonance was my objective with the stuffing, but it was based on a complete misunderstanding of how at TL actually works.
A while later, I wrote a term paper in engineering school where I derived the math of the TL.That was my start of actually understanding how a TL works.
In modern times I've built quite a few TL systems and run simulations of high Q woofers and stuffing using the various programs available like HornResp. If you do that you'll confirm that yes, you get a highly damped resonance from the resistive load of the stuffing.
But that misses the entire point of a TL pipe, which is to get the TL port to do all the heavy lifting and thus minimize the excursion of the woofer. (Back pressure from the resonance of the box, just like a bass reflex.) Stuffing a TL with a lot of resistive material only puts the brakes on everything and prevents the pipe from doing that work. So your woofer has to do the work all by itself. IMHO that's not good.
On the other hand, if you use only a little stuffing, you can take advantage of the line resonance so at the Fb of the system 3/4 of the air movement will come from the pipe. The woofer will have minimum excursion at box resonance. Around that frequency band it can play quite loud with little movement.
You'll also find that in order to get this to work right, you'll need a lower Q driver, typically between 0.25 and 0.4. High Q woofers work poorly in properly designed TLs.
However back then, I would have needed really special computer modeling skills to actually model a TL and I didn't really know what I was doing. I made the best of the limited tools I had at the time.
The articles in speaker builder claimed that a TL was a non-resonant enclosure. That non-resonance was my objective with the stuffing, but it was based on a complete misunderstanding of how at TL actually works.
A while later, I wrote a term paper in engineering school where I derived the math of the TL.That was my start of actually understanding how a TL works.
In modern times I've built quite a few TL systems and run simulations of high Q woofers and stuffing using the various programs available like HornResp. If you do that you'll confirm that yes, you get a highly damped resonance from the resistive load of the stuffing.
But that misses the entire point of a TL pipe, which is to get the TL port to do all the heavy lifting and thus minimize the excursion of the woofer. (Back pressure from the resonance of the box, just like a bass reflex.) Stuffing a TL with a lot of resistive material only puts the brakes on everything and prevents the pipe from doing that work. So your woofer has to do the work all by itself. IMHO that's not good.
On the other hand, if you use only a little stuffing, you can take advantage of the line resonance so at the Fb of the system 3/4 of the air movement will come from the pipe. The woofer will have minimum excursion at box resonance. Around that frequency band it can play quite loud with little movement.
You'll also find that in order to get this to work right, you'll need a lower Q driver, typically between 0.25 and 0.4. High Q woofers work poorly in properly designed TLs.
@perrymarshall
interesting to read about your practical experience.
I made this topic in order to find out if a TL will give a high Q driver something otherwise impossible:
a low fs combined with a linear response.
A closed box design with variovent would put fs up and having a bump in the response worsens the things if you want linearity. The variovent properly designed will bring it down but also a very damped sound.
So maybe a not too much damped TML will help to get maybe the best out of a high Q driver.
@ChrisABC
I studied exactly the enclosure called "viech" for the beyma 8agn as I have these drivers and still dont know how to use them.
In a reflex box of decent size the Beyma really really does nothing below 150 hz - I did not expect this bad result!
Its suspension is so stiff - for vocals its o..k. but 150 hz is far from being o.k for a fullrange.
So the trick of the viech horn is the concentrated damping below the driver - acting like a slight variovent - adding mechanical damping to the driver.
As the suspension of the Beyma is very stiff its also very PA like in the bass sound what many people like when you drive a box hard. And from measurements it could be learned that the horn dominates the bass frequency response irrespective of driver parameters. So the horn was the best choice for the beyma.
interesting to read about your practical experience.
I made this topic in order to find out if a TL will give a high Q driver something otherwise impossible:
a low fs combined with a linear response.
A closed box design with variovent would put fs up and having a bump in the response worsens the things if you want linearity. The variovent properly designed will bring it down but also a very damped sound.
So maybe a not too much damped TML will help to get maybe the best out of a high Q driver.
@ChrisABC
I studied exactly the enclosure called "viech" for the beyma 8agn as I have these drivers and still dont know how to use them.
In a reflex box of decent size the Beyma really really does nothing below 150 hz - I did not expect this bad result!
Its suspension is so stiff - for vocals its o..k. but 150 hz is far from being o.k for a fullrange.
So the trick of the viech horn is the concentrated damping below the driver - acting like a slight variovent - adding mechanical damping to the driver.
As the suspension of the Beyma is very stiff its also very PA like in the bass sound what many people like when you drive a box hard. And from measurements it could be learned that the horn dominates the bass frequency response irrespective of driver parameters. So the horn was the best choice for the beyma.
Measurement of Beyma 8 ag/n in marble reflex box with Arta in the near field 15cm with aluminized whizzer with thin foil and the paper cone sandwiched with household alu foil.
There is no measurement of the raw unmodified driver.
Really the Beyma due to a very stiff corrugated paper surround does not do anything below 100 Hertz.
Maybe the driver will get more response after long time break in, who knows.
There is no measurement of the raw unmodified driver.
Really the Beyma due to a very stiff corrugated paper surround does not do anything below 100 Hertz.
Maybe the driver will get more response after long time break in, who knows.
That's what I was trying to accomplish back in the day. I had the idea that I could "cheat" the laws of physics using line length and stuffing resistance to absorb the backwave and get deep bass out of a small box.
The computer modeling and acoustical engineering answer is that when a traveling wave reaches a boundary, ONLY 3 things can happen:
-Transmitted
-Reflected
-Absorbed
It takes at least 1/4 wavelength for the wave to "decide" what it is going to do, or to "sense" what the impedance is at that boundary.
What that means is that if your line is 1/4 wavelength long at 30Hz which is 3 meters, the length of stuffing in that line is too short to ABSORB the wave the way it would at higher frequencies. When I say absorb, I mean attenuate it and not reflect it back to the woofer.
So if you have super dense stuffing, the air can't pass through and the wave reflects off of the stuffing. Now all you did was make a smaller acoustic suspension cabinet.
(Also, back in the day, the belief was that stuffing slowed the speed of sound, making the line effectively longer. That's only a little bit true. It doesn't buy you much.)
If you have medium density stuffing, the air drags as it passes through, but it still passes through, you still get an output from the port, and you get a super damped response.
A high Q woofer has lower BL which means its ability to overcome that resistance is lower.
The practical experience of listening is that you get really anemic bass.
Also: The worst thing you can do with a transmission line is make the cross section too small. This was where I imagined I was cheating the laws of physics. I reasoned that a 30Hz wavelength is the same length whether I have a skinny pipe or a fat pipe, so why not make a skinny pipe?
Well the answer is that the pipe has an acoustical impedance, and a 10" diameter cone can't shove a wave down a 5" diameter pipe. The skinny pipe will just resist it and you'll get a shallow tapered response that starts rolling off below say 150Hz.
When you run the models you see that as you fatten the pipe, you fatten the response between Fb and 2xFb and you can get a nice plump bass if that's what you want. You tweak it until you get the response that you desire.
The notion that a TL is a "non resonant speaker enclosure" is a naive fantasy and most of the time that's not what you really want anyway. ANY speaker that has a low frequency roll off [= therefore ALL of them] is resonant, it's just a matter of what the Q of that resonance is and what the knee is like at the roll-off. There is no way around this.
Just like in bass reflex, if you want a more damped, less "ringy" tighter sound, a good option is to tune it to a lower frequency and have a more tapered response. It will somewhat resemble a low Q acoustic suspension.
I don't think it's ever a good idea to use a lot of stuffing in a TL because it just adds resistance to the port output. That increases cone excursion at Fb, which is the last thing you want it to do. Xmax is expensive. You want the pipe to do the work, not the woofer.
OK, so then what is it that makes people like TLs or makes it seem like they're non-resonant?
I say it's because the port output, which can exceed the woofer's output by 5-10dB, also has more bandwidth - more output in the lower midrange and not just at Fb, and it effectively adds to the surface area. The delayed output generates a sense of transparency and low frequency "space."
In theory this would not seem to be desirable at all, but remember we are talking about real rooms and real ears and real recorded musical instruments, not theoretical measurements and test tones and models, and I think pipes have a signature sound that the ear identifies as "natural." A well designed TL has a very large and expansive "low frequency soundstage."
It's more complex and messy, and TLs usually don't measure as neatly as reflex and sealed boxes. However, when the planets line up (when room acoustics and speaker and placement all match) the end result can be very satisfying. I really like the sound of well designed transmission lines (and back loaded horns as well). They have a much larger presentation than the more conventional box types, and they do sound less "boxy."
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These BLHs tend to have some interesting character in terms of how they terminate with the driver. A lower Qts driver is usually needed to avoid sharp, peaking modes from forming inside the horn. The increased air load of the line couples with the woofer and requires the motor to control the resonances forming inside the air column. As already mentioned, using extra dampening media hurts the supporting output efficiency provided by the rear horn. The transient response is also hit and miss with a BLH and the output falls off very sharp after the cutoff point.
Vsonics Transmission Line 8" woofer
Modeling?
This could be built with 3 rectangular cross sections (same area x 3).
Easier modified design.
How would it sound ?
https://web.archive.org/web/20110926081449/http://www.aksaonline.com/products/products_Vsonics.html
Construction photos, pages 1,4,5
https://www.audiocircle.com/index.php?topic=70732.0
-----
"VSONICS TRANSMISSION LINE SPEAKER
The VSonics were conceived by me and Laurie Menogue, for whom I am grateful for his detail design and hard work starting five years ago but continuing to this day. This is a compact, two way transmission line, using a three-way fold, an 8” (200mm) SEAS woofer and a 1” (25mm) Peerless tweeter. Fs is 35Hz but the quality of the bass is astonishing for its clarity.
The 32 litre speaker enclosure is a complex construction, but designed for easy assembly. There are three distinct chambers, all connecting to make a complete, 3 metre transmission line. The enclosure is 980mm height, 220mm wide, and more than 400mm deep. This is very convenient for small apartments with a perceived small footprint.
Xover is 2,600Hz and sensitivity is 87dB/watt/meter. The aperture is at front, making this a very suitable, as it is 100cms height by 23cm, ideally suited to a modern apartment. The kit is $1420, including crossovers, filling, fasteners and detailed specifications and instructions. You are obliged topurchase the drivers and the timber; but your total cost is just over $2200 for a product which exceeds most of the best TLs produced over the last fifty years.
Hugh R. Dean, Melbourne April 2016"
--------
"The VSonics were redeveloped recently with the demise of the Peerless 830884 driver to use the SEAS CA22RNY, another exceptional 8" driver. I'm happy to report that the sonics are now even better, with superior bass and, I think, slightly better resolution.
Hugh"
Peerless 830884 Qts .38, Vas 69 litres
SEAS CA22RNY Qts .3, Vas 82 litres
Modeling?
This could be built with 3 rectangular cross sections (same area x 3).
Easier modified design.
How would it sound ?
https://web.archive.org/web/20110926081449/http://www.aksaonline.com/products/products_Vsonics.html
Construction photos, pages 1,4,5
https://www.audiocircle.com/index.php?topic=70732.0
-----
"VSONICS TRANSMISSION LINE SPEAKER
The VSonics were conceived by me and Laurie Menogue, for whom I am grateful for his detail design and hard work starting five years ago but continuing to this day. This is a compact, two way transmission line, using a three-way fold, an 8” (200mm) SEAS woofer and a 1” (25mm) Peerless tweeter. Fs is 35Hz but the quality of the bass is astonishing for its clarity.
The 32 litre speaker enclosure is a complex construction, but designed for easy assembly. There are three distinct chambers, all connecting to make a complete, 3 metre transmission line. The enclosure is 980mm height, 220mm wide, and more than 400mm deep. This is very convenient for small apartments with a perceived small footprint.
Xover is 2,600Hz and sensitivity is 87dB/watt/meter. The aperture is at front, making this a very suitable, as it is 100cms height by 23cm, ideally suited to a modern apartment. The kit is $1420, including crossovers, filling, fasteners and detailed specifications and instructions. You are obliged topurchase the drivers and the timber; but your total cost is just over $2200 for a product which exceeds most of the best TLs produced over the last fifty years.
Hugh R. Dean, Melbourne April 2016"
--------
"The VSonics were redeveloped recently with the demise of the Peerless 830884 driver to use the SEAS CA22RNY, another exceptional 8" driver. I'm happy to report that the sonics are now even better, with superior bass and, I think, slightly better resolution.
Hugh"
Peerless 830884 Qts .38, Vas 69 litres
SEAS CA22RNY Qts .3, Vas 82 litres
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