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#1
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transmission line bass
I'd like to solicit the opinion(s) of knowledgeable readers.
As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel |
#2
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transmission line bass
"ludovic mirabel" wrote in message
news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel Suggested reading: G.L. Augspurger, "Loudspeakers in Damped Pipes--Part one: Modeling and Testing; and Part Two: Behavior," 107th JAES Convention, 24-27 September, 1999, prepring No. 5011. G.L. Augspurger, Transmission Lines Updated, Part 1 Speaker Builder 2/00 G.L. Augspurger, Transmission Lines Updated Part 2 Speaker Builder 3/00 G.L. Augspurger, Transmission Lines Updated Part 3 Speaker Builder 4/00 J.A. D'Appolito, Testing Loudspeakers, Audio Amateur Corporation Peterborough New Hampshire, 1998 Also the article in audioXpress from May 2002 describing the design of the THOR TL kit for SEAS Mr. D'Appolito mentions that "after many months of operation, the Dacron pillow filler settled in the second half of one of the lines." He says that this did not appear to affect performance but can be avoided by using Acousta Stuf or Dcron Quilt padding. Read the full article for all the details. |
#3
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transmission line bass
I would refer you to a google search and Martin J. King's site on
transmission lines, which includes some modeling software. There are other sites with modelling software to be found for TLs. If the FS of your 'mutt' drivers is not fairly low, then you may merely have found a room node which you managed to excite. Try taking the boxes (tubes) outside and see what they measure. _-_-bear ludovic mirabel wrote: I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. snip The brief version is: a) absorb all the backwave (in effect) making it an infinite baffle. (usually called a labrynth, iirc) or b) tune the backwave to like a lowish Q organ pipe and excite it. (usually called a "Tranmission Line", iirc) iirc... _-_-bear (Please make it as simple as possible). Ludovic Mirabel |
#4
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transmission line bass
Check out this link to nelson Pass's DIY site.
http://www.passdiy.com/speakers.htm A very interesting big transmission line. "ludovic mirabel" wrote in message news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel |
#5
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transmission line bass
"Don Gortemiller" wrote in message ...
Check out this link to nelson Pass's DIY site. http://www.passdiy.com/speakers.htm A very interesting big transmission line. Thanks for this link. Essentially what I have but mucho bigger. Nice to know that professional designers use sonotubes as well. What I wanted to and obviously failed to communicate was that with very little expense and skill one can get extraordinary bass performance. The cylindrical lines I set up are amazingly efficient. I had to equalise downwards BOTH sides. The left "only" 16db. down at 80, 50, 40 and 30 Hz. The right 30 db down *over two octaves*. And the bass is clean incomparably better sounding than what came from the closed boxes, properly Thiele measured for my 12" woofers. If all these cylindrical tubes do is go hunting for "room nodes" of that magnitude on both sides over two octaves then good hunting. Everyone should have nodes like that. I should say that my Acoustats have 100 watts monoblocks to produce 1000Hz while my bass comes fromm 200watts Bryston amp. But the same amp served the closed boxes with nowhere near such output and performance. What still puzzles me is why should the output get stronger and stronger while the filler was settling down. I read most of the links offered but found no explanation Ludovic Mirabel "ludovic mirabel" wrote in message news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel |
#6
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transmission line bass
"ludovic mirabel" wrote in message
news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel Having the 2 subs on opposite sides of the room is probably part of your problem. Comb filtering is the most liely culprit, since your not getting normal node excitation as I understand it. Try placing them both in the same corner and then see what happens. I'd bet you get a much smoother response. |
#7
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transmission line bass
Don Gortemiller wrote:
Check out this link to nelson Pass's DIY site. http://www.passdiy.com/speakers.htm A very interesting big transmission line. Well, imho, not so very interesting. Here's why. First, Pass uses no less than TWO 21" pro sound woofers, with an Fs of 25Hz, per channel. Then he loads them into what is simply a very large long tube. The result is not tuned particularly. So, he has to EQ the whole thing to get the response flat. In effect throwing out the relative sensitivity (two 96dB woofies in parallel - presumably getting 102dB/1w/1m/4 ohms) to achieve a "flat response." The filter he calls for is a 2nd order LP @ 20 Hz! One has to ask, would the effect be much different if he merely built what has been so popular here, what-it-called? The EBS alignment? And, a much smaller box. Ok, so you might like the long delayed LF coming out of those smokestacks in your listening room, I dunno. Note also, the end of the pipes are actually 2 feet from what is basically a large conic horn section - the peaked inside of the roof. Gain from this is possible too. Then he goes and plays them with 4,000 w/ch amps! Yeah, ok. As noted, check Martin King's method, I think it is likely superior. _-_-bear |
#8
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transmission line bass
"Michael Mckelvy" wrote in message ...
"ludovic mirabel" wrote in message news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel Having the 2 subs on opposite sides of the room is probably part of your problem. Comb filtering is the most liely culprit, since your not getting normal node excitation as I understand it. Try placing them both in the same corner and then see what happens. I'd bet you get a much smoother response. 1) These are no subs. They are 12" bass speakers crossed over at 400 Hz. to complement my ESL Acoustats also crossed. 2) I have no problem unless you call oodles of clean bass to pad down a problem. I just wanted to hear from people experienced with transmission lines if getting so much more output from transmission lines than from closed box is a common experience. Ludovic Mirabel |
#9
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transmission line bass
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#10
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transmission line bass
"ludovic mirabel" wrote in message
... "Michael Mckelvy" wrote in message ... "ludovic mirabel" wrote in message news I'd like to solicit the opinion(s) of knowledgeable readers. As I recounted recently I made two transmission line woofers, each consisting of two "sonotubes'" (compressed paper cylinders)one inside the other with a 12" woofer (Electrovoice frame and Altec Lansing cone). The whole enterprise is very primitive and just within my very limited aptitude for jigsawing and so on. The tubes are packed with Dacron pillow fill. They are 24db Linkwitz Xovered at 400Hz. Two things happened: 1) From the start I got clean bass and low treble. And buckets of it. I use Radio Shack SPL meter with the Stereophile warble 1/3 octave tones from my listening seat as a guide to equalisation Behringer 2084 digital equaliser) From the start I was getting more bass esp in the lower octaves, beginning with 100 Hz, than I ever got out of my old closed boxes (originally Magnat made) 2) Over the succeeding weeks it became obvious that the bass was getting obnoxiously too much. I remeasured. To cut the long story short: on the right side of my room which opens into an L dining room- (so no corner) I had to cut 80 Hz to 30 Hz range- mostly by 30 db(yes- no typo) to get it to match my starting point of ZERO db at 1000Hz. Even 20 Hz had to go 10 db down, And believe me I hear plenty of bass. No mistake. It would appear that as the filling settled down the lower octaves got louder. Is it what should happen with transmission line? I should say that now the right side is the "strong" side. When I had closed boxes I would blow the woofers trying to get 50 Hz up to mark. Hence my custom sturdy 12" made by a friendly speaker repairsman who took pity on me. The overall quality of my bass is the best I evar had and possibly the best I can recall having heard. The cost of sonotubes/pillowfill and one day's work is about the best return for the expenditure I ever made in audio. But I still would like to know HOW it works. (Please make it as simple as possible). Ludovic Mirabel Having the 2 subs on opposite sides of the room is probably part of your problem. Comb filtering is the most liely culprit, since your not getting normal node excitation as I understand it. Try placing them both in the same corner and then see what happens. I'd bet you get a much smoother response. 1) These are no subs. They are 12" bass speakers crossed over at 400 Hz. to complement my ESL Acoustats also crossed. I guess the next question I would ask is were the ESL's lacking in that area? 2) I have no problem unless you call oodles of clean bass to pad down a problem. Any time you have to make an adjustment it is a problem of sorts. The frequencies you mentioned did not sound like room nodes so I was interested in what sort of placement options you had experimented with. If there's no lack in FR at the range yiou have them crossed over at, what not try the TL's as subs? IME many rooms have dips at around 200 Hz and bumps around 50Hz that can only be gotten rid through some sort of passive (room treatment) or active EQ. If your happy with the setup you have, enjoy. I just wanted to hear from people experienced with transmission lines if getting so much more output from transmission lines than from closed box is a common experience. Ludovic Mirabel |
#11
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transmission line bass
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#12
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transmission line bass
"BEAR" wrote in message
... Don Gortemiller wrote: Check out this link to nelson Pass's DIY site. http://www.passdiy.com/speakers.htm A very interesting big transmission line. Well, imho, not so very interesting. Here's why. First, Pass uses no less than TWO 21" pro sound woofers, with an Fs of 25Hz, per channel. Then he loads them into what is simply a very large long tube. The result is not tuned particularly. So, he has to EQ the whole thing to get the response flat. In effect throwing out the relative sensitivity (two 96dB woofies in parallel - presumably getting 102dB/1w/1m/4 ohms) to achieve a "flat response." The filter he calls for is a 2nd order LP @ 20 Hz! One has to ask, would the effect be much different if he merely built what has been so popular here, what-it-called? The EBS alignment? And, a much smaller box. Ok, so you might like the long delayed LF coming out of those smokestacks in your listening room, I dunno. Note also, the end of the pipes are actually 2 feet from what is basically a large conic horn section - the peaked inside of the roof. Gain from this is possible too. Then he goes and plays them with 4,000 w/ch amps! Yeah, ok. As noted, check Martin King's method, I think it is likely superior. _-_-bear So far as I know Augpurger's work is currently the best and most definitive on TL's which is why i recomended it. I know of nobody who has done more to refine TL theory. |
#13
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transmission line bass - addenum
Two corrections:
1. The "EBS alignment" is not popular *here*, it's popular on another forum that I frequent. What it refers to is putting a long excursion/high power woofer in a box that is actually a bit small, and then EQ'ing the thing to get flat response down to some F3 (like 20Hz.) and then dropping the response off below that with a HP filter to keep from really wasting more power and heating the driver too much. It works nicely with the modern drivers now available. 2. I forgot to mention that shows these "TLs" against a floor/wall boundary, making it pi/4 space (that's right?), which provides boost. And then as noted the "outlet" of these smokestacks is only 2 feet from the sloped ceiling/wall boundary. I dunno, maybe he should stick to amps... _-_-bear BEAR wrote: Don Gortemiller wrote: Check out this link to nelson Pass's DIY site. http://www.passdiy.com/speakers.htm A very interesting big transmission line. Well, imho, not so very interesting. Here's why. First, Pass uses no less than TWO 21" pro sound woofers, with an Fs of 25Hz, per channel. Then he loads them into what is simply a very large long tube. The result is not tuned particularly. So, he has to EQ the whole thing to get the response flat. In effect throwing out the relative sensitivity (two 96dB woofies in parallel - presumably getting 102dB/1w/1m/4 ohms) to achieve a "flat response." The filter he calls for is a 2nd order LP @ 20 Hz! One has to ask, would the effect be much different if he merely built what has been so popular here, what-it-called? The EBS alignment? And, a much smaller box. Ok, so you might like the long delayed LF coming out of those smokestacks in your listening room, I dunno. Note also, the end of the pipes are actually 2 feet from what is basically a large conic horn section - the peaked inside of the roof. Gain from this is possible too. Then he goes and plays them with 4,000 w/ch amps! Yeah, ok. As noted, check Martin King's method, I think it is likely superior. _-_-bear |
#14
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transmission line bass
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#16
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transmission line bass - addenum
BEAR wrote in message ...
Two corrections: 1. The "EBS alignment" is not popular *here*, it's popular on another forum that I frequent. What it refers to is putting a long excursion/high power woofer in a box that is actually a bit small, and then EQ'ing the thing to get flat response down to some F3 (like 20Hz.) and then dropping the response off below that with a HP filter to keep from really wasting more power and heating the driver too much. It works nicely with the modern drivers now available. Actually, the excursion requirements for such an alignment are no more stringent than for any other woofer for the bandwith and SPL requirements. Driver excursion is determined by the frequency, the radiating area and the total acoustic power, not by the aligment of the system. In other words, to get, say, 100 dB SPL out of a 12" woofer at 20 Hz requires an excursion of 1.35 cm, it makes NO difference whether the system resonance is 15 Hz or 150 Hz. However, here's the advantage of a very small box alignment. As you approach resonance and, expecially, below, the driver is more and more stiffness-controlled. That is, the mechanical and acoustical stiffness control motion (above resonance, the system is mass- controlled, the moving mass controls the movement). That means, at low frequencies, where you are at or below resonance AND your excursion requirements are increased, the linearity of motion is more and more determined by the linearity, or more importantly, lack thereof, of the driver suspension. If you take a driver with a high compliance and a very low free- air Qts, and place it in a VERY small enclosure, small enough that it's system Qts is now raised to 0.707 (Butterworth 2nd order rolloff), it is now no longer the driver suspension that dominates the total system stiffness, it is the compression of the air in the box, which is a WHOLE lot more linear than the driver suspension. Further, since the volume of air is fixed and very accurately determined by simple cabinet dimensions, it is the acoustical stiffness that dominates over the mechnical stiffness, the latter having very poor manufacturing tolerance. These are precisely the arguments originally advanced by Villchur for the AR-1 and subsequent speakers, the so-called "acoustic suspension" principle. The technical arguments advanced are sound. The twist here is that the original acoustic suspension systems suffered from very poor efficiency. That problem is solved with the use of active equalization. It's perfectly sound, technically, to have a system that by itself has a system resonance of, oh, 150 Hz and a Qtc of 0.707, then be augmented with a +12 dB/octave boost down to 20 Hz, with a rolloff below that. The result is a 4th order system that's flat down to the system cutoff. The resulting system has a 6 dB orn better advantage over an acoustic suspension system of the same cutoff and bax volume. But, again, the excursion requirements for a 12" acoustic suspension and a 12" small-box, EQ'd design such as mentioned here are exactly the same. |
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