I have recently acquired a pair of these and i am currently looking for a design to mount them in , i have drifted towards folded horn designs for both SPL and aesthetics. I'm a total newby can someone point me in the direction of a suitable design, also is it necessary to redesign these basic designs to accommodate resonate frequencys and air volumes ? I have no idea.
tuba 24 ?
Hey thanks for the quick reply, those designs seem simple, but would a design like the Tuba 24 be unsuitable ? personally I prefer the looks of it.
Hey thanks for the quick reply, those designs seem simple, but would a design like the Tuba 24 be unsuitable ? personally I prefer the looks of it.
If I wanted to design my own Tl cab what would I need to pay attention too and is there any advice you could give to me ?
The best advice anybody could give with with these drivers in not to reinvent the wheel.
Having played around with these a few years ago I actually thought they did best in a small sealed box. I sold all mine when I bought a pair of Cerwin-Vegas with almost the exact same TS specs but a 800 watts of power handling and 20mm of travel
Nostalgia didn't sound as good as I thought it should
Having played around with these a few years ago I actually thought they did best in a small sealed box. I sold all mine when I bought a pair of Cerwin-Vegas with almost the exact same TS specs but a 800 watts of power handling and 20mm of travel
Nostalgia didn't sound as good as I thought it should
It all depends on the kind of sound you like. One of the most well known desgin using the KEF B139 is the Bailey Transmission Line enclosure.
http://user.faktiskt.se/lennartj/Audio/Bailey-1972-Transmission-Line-Loudspeaker-Enclosure.pdf
The low bass reach is good and the efficiency is good because it uses the enclosure as a phase inverter (half wavelength of B139 resonance) to get the back side wave to enhance the front. The best part is the quality of the bass which is fast, non-resonant.
The beauty of the Bailey design is that everyone can duplicate his result. He did that out of his dissatisfaction with the loosy, boomy bass of vented enclosures. The real, original TL bass may sound thin at first audition. That's why it may not be good for rock music. If you like classical or vocal, TL is for you.
One small problem is that the Transmission Line needs long fiber wool or the right kind of fine open cell foam to work right. Fiber glass or polyster fiber cannot do the job. (You may find some statement on the internet to say otherwise from people who never heard a long fiber wool filled transmission line.)
Irving M. "Bud" Fried invented the open cell foam damped TL speakers and believe that he could tailer it better than the Bailey approach. However, he also held his tuning as a trade secret. I met him once when did a product tour to a audio shop in Minnesota. Very personable gentleman.
One can purchase the LOW density open cell polyuerethane foam at fabric stores like Jo-Ann Fabrics.
Airtex High Density Urethane Foam Sheet 1''x18''x30' at Joann.com
It comes in large rolls that have to be flattened out to mark measure and cut.
The foam is more expensive then fiberglass. The amount of foam used in both enclosures was around $75 in the early 2000's. The foam that is required is a combination of 2" and 1" thick pieces in the lines. The foam has increased in price a lot in recent years because it is made from petroleum.
During the late 90's when one purchased a parts kit directly from Fried supplying the foam and crossover parts were left to the purchaser.
All of the required parts were specified with the plans including the exact gauge of wire used with the air core inductors.
Yes, it is expensive, but worth it. Bud Fried said the the foam was equivalent to the long fiber wool, which is even more expensive. Fiberglass cannot do the job in transmission line enclosure because the acoustics is completely different.
I don't know if there is a reliable source of long fiber wool in the US anymore. I got mine a long time ago from the St. Peter Woolen Mill. But I am not sure their wool today still meets the fiber dimension requirement of the TL.
When I got mine, I had the option of getting the raw wool. I decided to have them clean and card the wool into same batting that they were making for 2 loudspeaker makers in Minnesota. Minnesota was a hot bed of audio industry in the 70's. The processing costed 2 times of the cost of raw wool, but well worth it. After 40 years, the wool does not sack and has no smell or any other problem.
While it is difficult to repeat the experiments that Bailey and Bradbury did. But today's speaker builder can still check the result. A properly stuffed TL will have a very small second, higher frequency peak in the impedance curve. The frequency response will have the 6 db/octave slow decay starting at a low frequency. On the other hand, a faulty TL enclosure with Dracon or other polyfill stuffing will act just like a bass reflex enclosure or worse.
Plans http://p10hifi.net/TLS/classics/Bailey-WW-TL-map.pdf
It should be noted that to be a non-resonant enclosure (as per the title) the entire rear output of the driver needs to be absorbed. Since this is not the case, bass is reinforced by the terminus output, the enclosure is resonant (just like any TL designed to enhance bass output)
dave
Hi,
I agree with MD55, best not to get carried away.
Keep it simple, opposed sealed or move them on,
you can get better drivers for what they go for.
rgds, sreten.
I agree with MD55, best not to get carried away.
Keep it simple, opposed sealed or move them on,
you can get better drivers for what they go for.
rgds, sreten.
Haha, you may have a point here. Using layman's term, if you let something out, it is vented. LOL 😀
However, there is a very specific engineering definition on "Vented Speaker Enclosures" as developed by 2 Australian professors, Neville Thiel and Richard Small. It is a very well established definition. Unfortunately, most of their work were published at the Journal of Audio Engineering Society and would cost $25 to download. Their work allowed easy symthesize of a speaker system for a already manufactured speaker driver. The vented, or some times called bass reflex, enclousure has an opening. The air mass in this opening resonates with the "springiness" of the air inside the enclosure to improve the low frequency limit and/or efficiency over the performance of a similarly sized sealed box enclosure. The frequency at which the box/port system resonates, known as the Helmholtz resonance, depends upon the effective length and cross sectional area of the duct, the internal volume of the enclosure, and the speed of sound in air. Though helpful with extending bass performance, bass reflex cabinets can have poor transient response compared to sealed enclosures at frequencies near the lower limit of performance.
There are 2 attempts to get the better of both world, extended bass, better efficiency and good transient response. One is the Bailey transmission line already mentioned. Another is Ted Jordan's Aperiodic Enclosure.
http://www.ejjordan.co.uk/PDFs/A-Cabinet-of-Reduced-Size-with-Better-Low-Frequency-Performance.pdf
Yes, both TL and Aperiodic let air out of their opening. But they do not use the Helmholtz resonance principle and are very different in their bass transient response from a bass reflex enclosure.
The best analytical presentation of the TL theory is published by Professor Leslie Bradbury, another JAES paper that would cost $25.
L J S Bradbury, "The use of Fibrous Materials in Loudspeaker Enclosures", AES Journal, Vol. 24, No. 3, (April 1976)
You can find some of Bradbury result in an article on speaker damping material that Robert White wrote.
Volume filling a reflex box
Yes, one can build an enclosure using the Bailey plan. But when he fills it with polyester or similar fiber, the enclosure has completely different acoustic response than what Bailey originally intended. A Bailey enclosure with polyester fill is NOT a transmission line and can be called a bass reflex design. In fact, it is a resonant enclosure without the long fiber wool filling.
Last edited:
Can be downloaded from here: Read Research - Articles
Some important follow-up: AES Papers -- Official website of D.B.Keele
Bailey's was the 1st popular presentation, but not the 1st.
http://p10hifi.net/TLS/downloads/Acoustic-Labyrinth-Olney.pdf
Bailey's articles:
http://p10hifi.net/TLS/downloads/Bailey_TLs_1.pdf
http://p10hifi.net/TLS/downloads/Bailey_TLs_2.pdf
http://p10hifi.net/TLS/downloads/bailey_letters.pdf
A complete understanding of TLs did not really start until Martin King's work on creating an analytical model in 1999 (Augspurger also did a model but did not follow up & extend his work). Quarter Wavelength Loudspeaker Design
A TL uses a quarter-wave resonance instead of a helmholz resonance. A BR will transition to a TL as the aspect ratio of the enclosure changes such that one dimension is substantially larger than the other 2.
I am quite familiar with that paper -- the above links to the scan i made of the paper.
The last page of this brochure has Ted's realization.
http://p10hifi.net/TLS/downloads/goodmans-axiom-brochure.pdf
Small's paper on the subject
http://p10hifi.net/TLS/downloads/Richard-Small-Aperiodic.pdf
An aperiodic enclosure can be considered as a vented encloure with a resistance inserted into the vent. A continuum of alignments exist between a BR and a sealed box.
Depends.
MJK's work showed that Bradbury's work was not very good.
One just has to take into account the different properties of the absobing material. Some polyester fibre fills are quite poor, some designed specifically for audio are at least as good as wool without the downsides.
I will repeat … Bailey's line is a resonant enclosure. It uses a quarter-wave resonance to augment bass. To be non-resonant it would need to be stuffed until it is aperiodic and the rear wave is completely absorbed.
dave
Martin King never worked with a long fiber wool filled transmission line speaker enclosure. If he did, he never published it. His work at his website are all based on polyester/Darcon filled enclosures which has very different acoustic response to sound waves. He called his design a "quarter wave" or mass loaded transmission line. But it has no link to the Bailey/Bradbury design.
Martin King claimed that he went through the Bradbury paper and repeated his calculation. When I asked him whether he found the typo in the paper, he could not answer. He would not have been able to repeat the Bradbury calculation without correcting the typo in the JAES paper.
The Bradbury theory is well respected by combining higher order mathematics with very good experimental data. He showed excellent agreement between the two. But the non-linear characteristics of a long fiber filled line does not lend itself well to integration with enclosure modeling using simple linear filter model.
You can see the detail of the argument at the AudioKarma.
Transmision Line ? - AudioKarma.org Home Audio Stereo Discussion Forums
Martin's work opened up a whole lot of TL space and we now know how primitive these TLs were. Even ignoring that we have much better drivers to work with these days, we know so much more about how to design a TL, one would only do a Bailey-like line for nostalgia reasons.
dave
You will not know how good a long fiber wool filled Bailey enclosure sounds until you build one. If you like the more accurate and well damped transient bass for vocal and classical music, you will want to try one.
While it is difficult to repeat the experiments that Bailey and Bradbury did. (They need very specifilized engineering equipment and setups that were originally developed for submarine acoustic control.) But today's speaker builder can still check the result. A properly stuffed TL will have a very small second, higher frequency peak in the impedance curve. The frequency response will have the 6 db/octave slow decay starting at a low frequency. On the other hand, a mass loaded TL enclosure with Dracon or other polyfill stuffing will act just like a bass reflex enclosure with twin impedance peaks and 12 dB/octave decay. The MLTL also comes with the ringing bass that Ted Jordan and Arthur Bailey complaint about.
The driver makes some difference too, but was a secondary factor to the fiber fill issue. Bud Fried started with KEF drivers when he started his business, but at the end, used all customer made drivers for his system.
However, the characteristic of a speaker is a very personal choice. If you like the punchy bass of a bass reflex design, you will like the Martin King approach too. The audio effect difference of a fast transient (wool filled line) vs. a slow decay (Polyester filled) line can be easily heard in a listening comparison. No, it is not for nostalgia reasons, but rather a matter of musical taste.
Just curious, have you built a long fiber wool filled TL enclosure? Have you heard one of the IMF or TDL classical TL speakers? In Canada, you should be able to find long fiber wool material rather easily.
In the late 70s.
Yes.
I owned TLS80II. And Fried H.
From the old sheep's farm (a customer is a vet, i can have as much wool as i want)
dave
The classic transmission line using long fiber wool or open cell foam may sound lean in bass and unexciting at first when compared to bass reflex boxes. Is that your impression from the 70's too? But it is more accurate and non-fatique when you listen more carefully.
Did you hear any similarity between the IMF's and the Martin King's MLTL? Or the MLTL is more like bass reflex or vented in character to you?
The Leslie Bradbury JAES paper was peer reviewed. I found it of very high quality. He used complex number to formulate an analytical model of sound wave moving around stiff fiber of larger diameter and provide excellent test data to validate the model. This fluid dynamics based model is necessary because conventional thermodynamics model for fine fiber yields very different results. The mathematics is taught in advanced calculus for upper class science and engineering students and should be easy to follow.
Last question. Have you ever stuff a Martin King MLTL with long fiber wool, measure the impedance and frequency response curves and listen to it? I will love to see the comparison of curves using long fiber wool vs. Darcon in the same MLTL cabinet.
I am no fan of regular BR boxes.
I'd rank the Woden designed ML-TL we built for a pair of Alpair 12pWeN as the best bass we've had… a pair of SDX7eN sealed with a bit of EQ are pretty good too.
No. I gave up on wool long before King. We use Acousta-Stuff or UltraTouch.
dave
Hi,
LFW has no magic properties and you are just respouting
a load of nonsense propounded at the time. You don't
understand what you are evangelising so please give
it a rest. Reality has moved on a lot since those days.
rgds, sreten.
You are absolutely right that long fiber wool has no magic properties. It just interacts with sound wave in a specific way as described by Leslie Bradbury in precise scientific terms. On what basis you can call his work "nonsense"? Sorry, science does not change with time. It does get more discovery. Einstein's relativity does not invalidate the Newtonian physics, but expand the realm that science is applicable.
If you have problem with the science that Bradbury used, please, be more specific. You are evangelising with no basis, not me.
You will never say what you said if you build a long fiber wool filled Bailey enclosure and listen to it.
You can find some discussion and very useful work on how different fiber materials interact differently with sound from Ken Kantor. Ken is NOT talking about Bailey TL and his is NOT a believer of TL theory. But he is a well accomplished speaker designer. He found the NHT among other things. I think his opinion is worth something.
http://auralization.blogspot.com/?zx=cd110d9a201c1e5e
His conclusion that polyester has no sound attenuation at bass does have some implication on speaker enclosure stuffing. Robert White also said that polyester has no attenuation below 1 KHz. He was NOT talking about TL enclosure either.
Volume filling a reflex box
Are there any third party review of this stuffing material with measurements? By measurement, I mean diameter and density of the fiber and the acoustic attenuation as function of frequency at various packing densities.
Ken Kantor has shown most polyester fiber are poor stuffing material for closed box enclosures. But most commercial offering provides no specifics on performance in enclosure, just PR statements.
The best stuffing for closed box enclosure I can find is the Monacor MDM-3 damping pad that Falcon Acoustics recommanded. It is not cheap, but well worth it after spending all the money on drivers, crossover and enclosure.
http://www.monacor.co.uk/products/speakerbuilding-dampeningfoam/vnr/127880/?type=257&no_cache=1
It would be wonderful if someone can provide a comparison of performance between the Acousta-Stuff vs. the Monacor MDM-3 in the Ken Kantor type measurements.
Last edited: