you guessed it...
you can patent just about anything, the patent office is happy to take your money for the application and the yearly dues to keep it in place. Some of the biggest piles of (stuff) that you will ever read is to be found in some patents.
You are going into this one pretty much blind and almost on your own. That's not a bad thing really. Blind in that you don't have a set established design to build. That way at least you can do what ever you think you need to do to make it work. You get to have a fresh and personal kick at this cat. There are enough folks here that will be interested in your results and most likely also want to throw their two cents into the bank if it does not work out as hoped.
Sounds like volenti has the right idea to get the max possible options from his build. You could do worse than to follow his lead. Perhaps you two could double track with each other and do some experimenting together to fast track the project? Regards Moray James.
you can patent just about anything, the patent office is happy to take your money for the application and the yearly dues to keep it in place. Some of the biggest piles of (stuff) that you will ever read is to be found in some patents.
You are going into this one pretty much blind and almost on your own. That's not a bad thing really. Blind in that you don't have a set established design to build. That way at least you can do what ever you think you need to do to make it work. You get to have a fresh and personal kick at this cat. There are enough folks here that will be interested in your results and most likely also want to throw their two cents into the bank if it does not work out as hoped.
Sounds like volenti has the right idea to get the max possible options from his build. You could do worse than to follow his lead. Perhaps you two could double track with each other and do some experimenting together to fast track the project? Regards Moray James.
Re: you guessed it...
Yea I'm approaching this from the angle that I understand most, which is transmission lines. I build a line that is just long enough to sound good with music but that would be "weak" for HT in the lower end, then add the resonator to it and see what effect it has (with the ideal result of an extended bottom end), all the modular stuff just makes it quick and easy to go "now what happens if I do this..."
moray james said:
Yea I'm approaching this from the angle that I understand most, which is transmission lines. I build a line that is just long enough to sound good with music but that would be "weak" for HT in the lower end, then add the resonator to it and see what effect it has (with the ideal result of an extended bottom end), all the modular stuff just makes it quick and easy to go "now what happens if I do this..."
Going into it blind? I wouldn't call it that, since there is documentation describing all the sizes - you don't have to design it, just build it from the instructions.
Cost is not a huge deal. MDF is cheap, and you can use a driver you have on hand - most of us have something we could use.
For many of us, the real issue is having a room that suits.
Cost is not a huge deal. MDF is cheap, and you can use a driver you have on hand - most of us have something we could use.
For many of us, the real issue is having a room that suits.
another way of looking at blind...
Hey Paul: the design is decades old and a real cold potatoe at that. There are only two known accounts of people building this thing (not counting Wimslow) and with limited feedback. That is as close to blind as I want to get. Yes there are drawings to build off of. My point was that aside from the patent (which makes limited sence) there is an open playing field here. Any one who wants to play with this design and pick up where Holliman left off is free to do so. There is no common theory to have to follow. The new builder is free of the normal pressures that come from trends.
The patent tells you about the box in the drawings but not how to design one or what really makes it work, it is Holliman's theory. That and a dollar won't buy you a cup of "Joe".
So the new builder has all the options in the world to play with and that is good. I will be interested to hear of the results of any here who give this cat a kick. Regards Moray james.
Hey Paul: the design is decades old and a real cold potatoe at that. There are only two known accounts of people building this thing (not counting Wimslow) and with limited feedback. That is as close to blind as I want to get. Yes there are drawings to build off of. My point was that aside from the patent (which makes limited sence) there is an open playing field here. Any one who wants to play with this design and pick up where Holliman left off is free to do so. There is no common theory to have to follow. The new builder is free of the normal pressures that come from trends.
The patent tells you about the box in the drawings but not how to design one or what really makes it work, it is Holliman's theory. That and a dollar won't buy you a cup of "Joe".
So the new builder has all the options in the world to play with and that is good. I will be interested to hear of the results of any here who give this cat a kick. Regards Moray james.
I really don't have any idea why I feel so compelled to speak up in regards to this box's (relatively unproven) merits and I will probably stop soon, but...
People are still wondering why this box can do the things people claim it can. I have said it before (maybe not in this thread) and I will say it again. It is all about the loading method. That is why Akabak cannot model it properly and why so many people don't understand what is going on here. The following excerpt is from the Decware thread. It documents a preliminary experiment that someone did with the same type of loading method. It is something everyone can try, and the people that have Akabak can try it, then model it, then compare and wonder what went wrong. This information came from 2 or 3 long posts so I editted for meaningful content. Head over to the Decware forums to see it whole.
"Try this... Using an existing sub woofer enclosure that has the driver firing into the listening space; remove the driver, and stuff the port with an old shirt or towel or something to plug it off. Extend the hook up wires about a foot or so and attach them to the driver terminals. insert the screws that held the driver in place back into thier holes until the head of the screw is approx. 9/16th above the hole in the enclosure turn the driver so that the magnet is outside the cabinet and place it upsidedown with the edge of the basket resting on the screws. Hold the driver still with your hand or use a pair of pipe clamps and a board if you like.
This is what I have done so far with experimentation. I dis assembled my KLH 10-120 sub and used 4 sets of home made sdjustable spacers to find the most effective distance between the hole the 10 inch driver was origionally mounted in and the basket with the cone firing into the hole. Essentially, I pulled out the driver, and placed it backwards over the cabinet it came in. I plugged off the origional vent, and used no other baffle for the first experiment.
The Result: most efficient spacing is a mere 9/16 inch above the hole. I can feel the vibration through the chair I'm sitting on at moderate volume, and the old fashioned metal bell alarmclock across the room starts ringing if I turn the gain past half way at 25 cycles.
I am a little worried because my ears are complaining a little bit. Maybe this isn't such a good idea? Next time I will have to wait till no one else is home and use ear plugs just in case this gets a little dangerous. "
There lies the magic of this box. It's all about the loading method. Add a couple of tapered ports for added sensitivity and lower bottom end tuning, add some velocity coupling for even more of the same, and that's it.
And finally, just to back up my opinion that this thing will be capable of getting loud, a quote from GM from another thread where I specifically asked if he would like to comment on this design.
"I researched the G-H some time ago, but can't find my notes, though in a nutshell, in theory I can get superior performance overall in a smaller bulk using a corner loaded PWT now that low Fs, high Xmax/power handling drivers and megawatt amps are available at a reasonable price. Still, a low pass filtered resonant cavity can be a 'moving' experience if you have a basement, attic, or similar size volume available to couple it to."
Now in the end, I will be building this box but I wonder how the news will be received. I will be only the third documented evidence of someone who has built it and is (likely to be) very happy with it. I don't own an SPL meter, why believe me either when the time comes?
People are still wondering why this box can do the things people claim it can. I have said it before (maybe not in this thread) and I will say it again. It is all about the loading method. That is why Akabak cannot model it properly and why so many people don't understand what is going on here. The following excerpt is from the Decware thread. It documents a preliminary experiment that someone did with the same type of loading method. It is something everyone can try, and the people that have Akabak can try it, then model it, then compare and wonder what went wrong. This information came from 2 or 3 long posts so I editted for meaningful content. Head over to the Decware forums to see it whole.
"Try this... Using an existing sub woofer enclosure that has the driver firing into the listening space; remove the driver, and stuff the port with an old shirt or towel or something to plug it off. Extend the hook up wires about a foot or so and attach them to the driver terminals. insert the screws that held the driver in place back into thier holes until the head of the screw is approx. 9/16th above the hole in the enclosure turn the driver so that the magnet is outside the cabinet and place it upsidedown with the edge of the basket resting on the screws. Hold the driver still with your hand or use a pair of pipe clamps and a board if you like.
This is what I have done so far with experimentation. I dis assembled my KLH 10-120 sub and used 4 sets of home made sdjustable spacers to find the most effective distance between the hole the 10 inch driver was origionally mounted in and the basket with the cone firing into the hole. Essentially, I pulled out the driver, and placed it backwards over the cabinet it came in. I plugged off the origional vent, and used no other baffle for the first experiment.
The Result: most efficient spacing is a mere 9/16 inch above the hole. I can feel the vibration through the chair I'm sitting on at moderate volume, and the old fashioned metal bell alarmclock across the room starts ringing if I turn the gain past half way at 25 cycles.
I am a little worried because my ears are complaining a little bit. Maybe this isn't such a good idea? Next time I will have to wait till no one else is home and use ear plugs just in case this gets a little dangerous. "
There lies the magic of this box. It's all about the loading method. Add a couple of tapered ports for added sensitivity and lower bottom end tuning, add some velocity coupling for even more of the same, and that's it.
And finally, just to back up my opinion that this thing will be capable of getting loud, a quote from GM from another thread where I specifically asked if he would like to comment on this design.
"I researched the G-H some time ago, but can't find my notes, though in a nutshell, in theory I can get superior performance overall in a smaller bulk using a corner loaded PWT now that low Fs, high Xmax/power handling drivers and megawatt amps are available at a reasonable price. Still, a low pass filtered resonant cavity can be a 'moving' experience if you have a basement, attic, or similar size volume available to couple it to."
Now in the end, I will be building this box but I wonder how the news will be received. I will be only the third documented evidence of someone who has built it and is (likely to be) very happy with it. I don't own an SPL meter, why believe me either when the time comes?
Jensen loading configuration...
Freddy over at the asylum posted a thread on an old Jensen design that used a similar vent loading system. The mini sub that I just posted about also uses a similar arrangement.
Don't understand why you are taking the reluctance of others to agree with you regarding this design personally. You said it yourself you will be only the third person in decades to build one of these. Ok that's great and many will be interested in your results. Everybody else could well be wrong that's possible, what do you really think?
I think that you may be sucessful in finding a way to make it better which would be great. However you may not succeed and the design may be a bust. Its a crap shoot. You are willing to give it a roll just as others are not and intitled to give it a pass. You asked for opinions but get upset when the opinions don't support what you want to believe. Build one and post about it. I am sure that there will be interest either way. You will want to build a very rigid system so MDF is not going to be in the cards. Regards Moray James.
Freddy over at the asylum posted a thread on an old Jensen design that used a similar vent loading system. The mini sub that I just posted about also uses a similar arrangement.
Don't understand why you are taking the reluctance of others to agree with you regarding this design personally. You said it yourself you will be only the third person in decades to build one of these. Ok that's great and many will be interested in your results. Everybody else could well be wrong that's possible, what do you really think?
I think that you may be sucessful in finding a way to make it better which would be great. However you may not succeed and the design may be a bust. Its a crap shoot. You are willing to give it a roll just as others are not and intitled to give it a pass. You asked for opinions but get upset when the opinions don't support what you want to believe. Build one and post about it. I am sure that there will be interest either way. You will want to build a very rigid system so MDF is not going to be in the cards. Regards Moray James.
In the thread I started I posted my thoughts on this design. No one agreed and one person disagreed. Believe me, I'm not upset about that. I started a separate thread because in that one I wanted to discuss the possibility of slightly manipulating the tuning to suit personal taste before I build.
The reason I did not want to post those ideas here are because the thread I started assumes from the beginning that this design works while this thread has still not come to that conclusion. The only agreement I am looking for in this thread is that the Holliman type loading method - not the entire design, just the loading method - actually does work and if used properly, can be used to obtain lower than ordinary bass from a given driver at unusually high sensitivity.
After reading my last post I suppose I almost do sound upset because of a bad choice of wording that I can no longer change. So what I meant was - I will be building the box but the only measurement tools I have are signal generators and my ears. It's still only one guy's opinion in the end.
All of this is just yet another way of saying I see potential here, and I will stop saying that without proof. I agree, I do sound a bit upset in that last post and I certainly am not.
The reason I did not want to post those ideas here are because the thread I started assumes from the beginning that this design works while this thread has still not come to that conclusion. The only agreement I am looking for in this thread is that the Holliman type loading method - not the entire design, just the loading method - actually does work and if used properly, can be used to obtain lower than ordinary bass from a given driver at unusually high sensitivity.
After reading my last post I suppose I almost do sound upset because of a bad choice of wording that I can no longer change. So what I meant was - I will be building the box but the only measurement tools I have are signal generators and my ears. It's still only one guy's opinion in the end.
All of this is just yet another way of saying I see potential here, and I will stop saying that without proof. I agree, I do sound a bit upset in that last post and I certainly am not.
what is your basic take on this design?
Can you explain where youre understanding and mine diverge? I see the big box cavity as a Helmholtz resonator you can establish at what frequency this volume will resonate as well as its Q and band using the speaker calculator since you have the volume and the vent opening size and can decide the cabinet wall thickness at what ever thickness you choose. Then I see what you discribe as reflex ducts as a pipe all be the the shape is modified (tapered). The reason that I see them as a pipe rather than ducts is that they couple together acoustically in the middle over the top section of the Helmholtz cabinet right where the vent is. So I dont see them (the ducts) as an extension of the Helmholtz port like a reflex vent. Both sections couple and should (as far as I can tell) act like a single pipe (of the combined length) would.
So I see the driver as the generator of the acoustic energy that excites the pipe (as I see it) which then in turn excites the resonance of the helmholtz cavity. I suppose that this process could be reversed but amounts to much the same thing. I am thinking that you want the resonant frequency of the Helmholtz resonator (which should be the lower frequency of the two systems) to be positioned at the low end (or even below the lowest resonant mode of the pipe) of the pipe's resonance to obtain the maximum extension of the rpossible resonant boost of the system.
Does this make sense to you? If not tell me where we differ. Hope that this discussion helps, looking forward to your thoughts. Regards Moray James.
Can you explain where youre understanding and mine diverge? I see the big box cavity as a Helmholtz resonator you can establish at what frequency this volume will resonate as well as its Q and band using the speaker calculator since you have the volume and the vent opening size and can decide the cabinet wall thickness at what ever thickness you choose. Then I see what you discribe as reflex ducts as a pipe all be the the shape is modified (tapered). The reason that I see them as a pipe rather than ducts is that they couple together acoustically in the middle over the top section of the Helmholtz cabinet right where the vent is. So I dont see them (the ducts) as an extension of the Helmholtz port like a reflex vent. Both sections couple and should (as far as I can tell) act like a single pipe (of the combined length) would.
So I see the driver as the generator of the acoustic energy that excites the pipe (as I see it) which then in turn excites the resonance of the helmholtz cavity. I suppose that this process could be reversed but amounts to much the same thing. I am thinking that you want the resonant frequency of the Helmholtz resonator (which should be the lower frequency of the two systems) to be positioned at the low end (or even below the lowest resonant mode of the pipe) of the pipe's resonance to obtain the maximum extension of the rpossible resonant boost of the system.
Does this make sense to you? If not tell me where we differ. Hope that this discussion helps, looking forward to your thoughts. Regards Moray James.
My full description of the design is in the other thread, in an attachment. I still firmly believe everything I put in there. But since there is no consensus at this point there is another way to go about this. Instead of talking about how and why, I will try "what if..." Note that I have not tried any of this yet, it's just my best guess at what might happen.
What if you took a suitably sized subwoofer, took the driver out, reversed it, and suspended it in front of it's mounting hole? (2 cubic foot sealed box for a 10 inch driver, 4 for a 12, 7 for a 15) Although I have not done it yet, I expect that there would be a huge but narrow resonant peak much lower than the box tuning/driver combination would suggest. Because of the loading method, the resonant frequency of the driver/resonator combination should be between 20 and 30 hz for the driver and box sizes we are dealing with. I would expect this narrow-band peak to swamp everything outside of it's range of resonance, and even without a baffle or external ports, to do so with incredible sensitivity and low distortion, all simply because of the loading method. In this form it would be unusable in an audio system, as it would simply be a huge narrow resonant spike lasting only a few hz with a steep rolloff on either side.
Now, what if you add a baffle for the driver and control the output by using ports, passive radiators, etc, like Holliman's examples? If you were to do a frequency sweep starting high and going down, I would expect to hear little to nothing until you got down to the resonant peak of the sealed chamber as detailed in the last paragraph, somewhere around 20 - 30 hz. But instead of being a narrow-band spike, I would expect the resonance to continue down in frequency to a point dictated by the helmholtz resonator/port (or PR) combination. Basically, the longer the port (or the lower tuned the PR) the lower the overall box's range of resonance will extend. I would expect everything outside of this range of resonance to be rolling off at a very steep rate.
That is what I think should happen, but again, I haven't tested any of it. If it works out like that, the how and why is not so important. If this much is true, it allows for a bit of tweaking for the upper and lower frequency cutoff points.
What if you took a suitably sized subwoofer, took the driver out, reversed it, and suspended it in front of it's mounting hole? (2 cubic foot sealed box for a 10 inch driver, 4 for a 12, 7 for a 15) Although I have not done it yet, I expect that there would be a huge but narrow resonant peak much lower than the box tuning/driver combination would suggest. Because of the loading method, the resonant frequency of the driver/resonator combination should be between 20 and 30 hz for the driver and box sizes we are dealing with. I would expect this narrow-band peak to swamp everything outside of it's range of resonance, and even without a baffle or external ports, to do so with incredible sensitivity and low distortion, all simply because of the loading method. In this form it would be unusable in an audio system, as it would simply be a huge narrow resonant spike lasting only a few hz with a steep rolloff on either side.
Now, what if you add a baffle for the driver and control the output by using ports, passive radiators, etc, like Holliman's examples? If you were to do a frequency sweep starting high and going down, I would expect to hear little to nothing until you got down to the resonant peak of the sealed chamber as detailed in the last paragraph, somewhere around 20 - 30 hz. But instead of being a narrow-band spike, I would expect the resonance to continue down in frequency to a point dictated by the helmholtz resonator/port (or PR) combination. Basically, the longer the port (or the lower tuned the PR) the lower the overall box's range of resonance will extend. I would expect everything outside of this range of resonance to be rolling off at a very steep rate.
That is what I think should happen, but again, I haven't tested any of it. If it works out like that, the how and why is not so important. If this much is true, it allows for a bit of tweaking for the upper and lower frequency cutoff points.
thinking about a reply...
I wanted to mail this to you directly but your mail is blocked. I think that you may well find some interesting information in this patent application. The company has been around for a good number of years and has substantial financial backing. They actually produce a variety of different models. I will assume that this idea works as they have been building and selling them for some time. You can see a review at 6 moons. The application below is the second refinement of the concept so work has been on going. You may find some techniques to shrink your Holliman design in the application. As a diy project I see this as far more practical. I should think that you could either scale the design if you wanted but a better idea might be to use four or eight such small units dispersed through out your room to achieve better controll of room modes and still keep the volume impact almost invisable.
Will try to come up with a reasonable reply as soon as i can figure one out. Best regards Moray James.
United States Patent Application 20040251079
Kind Code A1
Plummer, Jan Princeton December 16, 2004
Inventors: Plummer, Jan Princeton; (Marietta, GA)
Correspondence Name and Address: JAN P. PLUMMER
341 ENGLAND PL NE.
MARIETTA
GA
30066
US
Serial No.: 709538
Series Code: 10
Filed: May 12, 2004
U.S. Current Class: 181/199; 181/156
U.S. Class at Publication: 181/199; 181/156
Intern'l Class: A47B 081/06
[0036] DIRECT COUPLED LOW FREQUENCY ONLY APPLICATIONS-Conventional loudspeakers need large diaphragm areas and/or high mass to produce low frequencies while attaining high efficiency in the process. The current processes for bass reproduction are inherently efficient because they operate the driver at and near its' resonant frequency but this is also the Achilles' heel for sound quality. Resonance is the number one enemy of a finished sound system although the parameter is involved with the execution of any speaker system. The DC EATL 5 mode of operation will allow a very small driver to produce low bass frequencies at low to moderate efficiencies. When a 3" driver is made capable of producing very low frequencies at a useful level then efficiency isn't a proper term to characterize its' performance.
[0037] FIG. 5 represents the application of the EATL5 in conjunction with a dynamic driver 41 for the purpose of generating very low frequencies only and is called the Direct Coupled DC EATL 5. The EATL construction is very similar to the IDC with the exception of a larger throat/mouth opening 6 equal to the driver diameter and compression plug 12 located immediately in front of the driver 41. The EATL 5 is Directly Coupled (DC) to the driver 41 with minimum area air volume in chamber 10 between the driver and the throat/mouth 6 of the EATL 5. The driver is mounted with front facing the EATL5 mouth 6 so as to create a high compression chamber 10 for driver loading. In this mode the driver 41 is compression loaded so a compression plug 12 is used to help direct wave motion into the EATL 5 and to minimize air turbulence at the throat/mouth 6 of the EATL5 and to establish the correct throat/mouth 6 area for the EATL5. DC coupling places the driver 41 completely under the influence of the EATL5 and it will follow the frequency pattern it establishes. The ADTM 4 establishes delay of the waves through depth migration thus allowing a wide DSW bandwidth. The higher low frequencies above driver 41 resonance are not effected as readily by the cellular structure and will sustain constant pressure in the EATL 5 before depth migration. This can be seen in FIGS. 13C and 14D. The frequency response curve FIG. 13C represents the driver 41 output of a DC driver and EATL5 only and it can be seen that the frequency response shows a 12 db/oct falling output from the driver 41 resonance frequency and frequency irregularities above driver resonance. This represents a constant high positive pressure on the DD 3 relative to frequency and a dynamic pressure much greater than atmospheric pressure for all frequencies in the systems bandwidth. When measured at 100 Hz this signal at the DD3 is 40 db greater than that at the mouth of the port 17 when it is added. This output curve represents the actual output that the driver 41 will deliver with the positive pressure applied to the DD 3 from the EATL 5. In free air a similar pattern would be generated except the 12 db/oct slope would begin at the drivers' free air resonance frequency. Under these conditions the frequency would shift if the acoustic impedance of the driver is altered. Curve S is a reference high-pressure curve with a predictable 12 db/oct rate of fall and is easy to shape with an acoustic low pass filter. This curve also reflects a predictable falling diaphragm excursion relative to lower frequencies. A reflex enclosure would further reduce DD 3 motion in the power bass frequency range (30 Hz-60 Hz) and not have a subsonic distortion problem after the EATL5 peak. An acoustic low pass filter 18 connected to the driver 41/EATL5 in FIG. 5 would favor the lowest frequencies even though these frequencies are falling in curve S FIG. 13C. The 12 db/oct falling output of FIG. 13C are transformed into the curve R of FIG. 13D for FIG. 6 which shows 6 db/oct rising output from 70 Hz. The curve in FIG. 13C is generated with the driver 41 in high-pressure environment that will resonate the box with little effect on the constant pressure loading of the driver. The positive pressure allows the output from the rear of the driver to resonate a reflex enclosure with acoustic volume 19 at frequencies within the 12 db/oct slope. The efficiency in the range of the transformation is moderate relative to the driver mid-band efficiency yet it allows a small low mass driver to use its' fast responding diaphragm to produce usable bass at frequencies determined by the EATL5. Almost any similar diameter driver 41 used if its compliance is not to stiff will generate the curves of FIG. 13C and FIG. 13D. The 1/4 wave positive pressure is a real-time mass component acoustically applied to the DD 3 to produce the enhanced low pass performance from the driver 41 as indicated in FIG. 13D for FIG. 6. The drivers' 41 mass and other parameters will affect distortion, efficiency and to some degree extreme frequency cut-off so optimum performance from a certain EATL/Reflex enclosure can be had through driver 41 choice. The efficiency of this type of bass system is still related to actual DD 3 area and it increases with a larger driver 41 as would be normal since more air molecules would be moved. Typically the low frequency output of large drivers 41 increase relative to mid-band output because of diaphragm area as mass deters output at higher frequencies. The DCEATL 5 low frequency system develops output from diaphragm area not geometry. The listening room, typically being an acoustic space with dimensional gain, also favors lower frequencies if they are present. The curve of FIG. 14C represents distant microphone placement when measuring the sub-bass system of FIG. 6. The room acts similar to the reflex enclosure in lifting the output at the lower bass frequencies as is seen in curve O by the big increase in gain in the 15 Hz octave in FIG. 14C relative to adjacent frequencies. FIG. 14A indicates the impedance of FIG. 5 and FIG. 6. The curves are overlaid to show how little the reflex box alters the resonant frequency and Q of the driver when it is connected. This indicates that the positive pressure within the EATL 5 dominates the drivers' impedance with little effect on the driver 41/EATL 5 operating parameters from the addition of the acoustic low pass filter. In FIG. 14A the large peak K represents the impedance of the driver in FIG. 5. The small peak J trailing the driver peak L in FIG. 14A would be considered the ports peak with a conventional reflex enclosure and the output would fall off rapidly as the frequency approaches this peak. This peak represents the same EATL 5 peak that was observed in the impedance peak of FIG. 12B, FIG. 13A, FIG. 13B except that it has been pushed below the driver resonance due to the close coupling of the EATL5. It has been shown that increasing the length of the EATL5 will lower the EATL5 peak, as close coupling will also cause. Depth migration is greater under high pressure causing the 1/4 wave signal to appear at the driver diaphragm below box tuning. It is also observed as shown in FIG. 13D that the output will fall after the main EATL 5 peak but the close coupling will load the driver to the EATL5 cut-off frequency of near 15 Hz. If it is observed carefully the output curve R of FIG. 13D of the sub-bass enclosure FIG. 6 has its' highest output at the EATL 5 peak of 35 Hz which is an extraordinary feature. The reason for this can be seen if the curves of FIG. 14D are observed. FIG. 14D represents the phase curves of the subwoofer in FIG. 6. The curves are overlaid to show their relationships.
I wanted to mail this to you directly but your mail is blocked. I think that you may well find some interesting information in this patent application. The company has been around for a good number of years and has substantial financial backing. They actually produce a variety of different models. I will assume that this idea works as they have been building and selling them for some time. You can see a review at 6 moons. The application below is the second refinement of the concept so work has been on going. You may find some techniques to shrink your Holliman design in the application. As a diy project I see this as far more practical. I should think that you could either scale the design if you wanted but a better idea might be to use four or eight such small units dispersed through out your room to achieve better controll of room modes and still keep the volume impact almost invisable.
Will try to come up with a reasonable reply as soon as i can figure one out. Best regards Moray James.
United States Patent Application 20040251079
Kind Code A1
Plummer, Jan Princeton December 16, 2004
Inventors: Plummer, Jan Princeton; (Marietta, GA)
Correspondence Name and Address: JAN P. PLUMMER
341 ENGLAND PL NE.
MARIETTA
GA
30066
US
Serial No.: 709538
Series Code: 10
Filed: May 12, 2004
U.S. Current Class: 181/199; 181/156
U.S. Class at Publication: 181/199; 181/156
Intern'l Class: A47B 081/06
[0036] DIRECT COUPLED LOW FREQUENCY ONLY APPLICATIONS-Conventional loudspeakers need large diaphragm areas and/or high mass to produce low frequencies while attaining high efficiency in the process. The current processes for bass reproduction are inherently efficient because they operate the driver at and near its' resonant frequency but this is also the Achilles' heel for sound quality. Resonance is the number one enemy of a finished sound system although the parameter is involved with the execution of any speaker system. The DC EATL 5 mode of operation will allow a very small driver to produce low bass frequencies at low to moderate efficiencies. When a 3" driver is made capable of producing very low frequencies at a useful level then efficiency isn't a proper term to characterize its' performance.
[0037] FIG. 5 represents the application of the EATL5 in conjunction with a dynamic driver 41 for the purpose of generating very low frequencies only and is called the Direct Coupled DC EATL 5. The EATL construction is very similar to the IDC with the exception of a larger throat/mouth opening 6 equal to the driver diameter and compression plug 12 located immediately in front of the driver 41. The EATL 5 is Directly Coupled (DC) to the driver 41 with minimum area air volume in chamber 10 between the driver and the throat/mouth 6 of the EATL 5. The driver is mounted with front facing the EATL5 mouth 6 so as to create a high compression chamber 10 for driver loading. In this mode the driver 41 is compression loaded so a compression plug 12 is used to help direct wave motion into the EATL 5 and to minimize air turbulence at the throat/mouth 6 of the EATL5 and to establish the correct throat/mouth 6 area for the EATL5. DC coupling places the driver 41 completely under the influence of the EATL5 and it will follow the frequency pattern it establishes. The ADTM 4 establishes delay of the waves through depth migration thus allowing a wide DSW bandwidth. The higher low frequencies above driver 41 resonance are not effected as readily by the cellular structure and will sustain constant pressure in the EATL 5 before depth migration. This can be seen in FIGS. 13C and 14D. The frequency response curve FIG. 13C represents the driver 41 output of a DC driver and EATL5 only and it can be seen that the frequency response shows a 12 db/oct falling output from the driver 41 resonance frequency and frequency irregularities above driver resonance. This represents a constant high positive pressure on the DD 3 relative to frequency and a dynamic pressure much greater than atmospheric pressure for all frequencies in the systems bandwidth. When measured at 100 Hz this signal at the DD3 is 40 db greater than that at the mouth of the port 17 when it is added. This output curve represents the actual output that the driver 41 will deliver with the positive pressure applied to the DD 3 from the EATL 5. In free air a similar pattern would be generated except the 12 db/oct slope would begin at the drivers' free air resonance frequency. Under these conditions the frequency would shift if the acoustic impedance of the driver is altered. Curve S is a reference high-pressure curve with a predictable 12 db/oct rate of fall and is easy to shape with an acoustic low pass filter. This curve also reflects a predictable falling diaphragm excursion relative to lower frequencies. A reflex enclosure would further reduce DD 3 motion in the power bass frequency range (30 Hz-60 Hz) and not have a subsonic distortion problem after the EATL5 peak. An acoustic low pass filter 18 connected to the driver 41/EATL5 in FIG. 5 would favor the lowest frequencies even though these frequencies are falling in curve S FIG. 13C. The 12 db/oct falling output of FIG. 13C are transformed into the curve R of FIG. 13D for FIG. 6 which shows 6 db/oct rising output from 70 Hz. The curve in FIG. 13C is generated with the driver 41 in high-pressure environment that will resonate the box with little effect on the constant pressure loading of the driver. The positive pressure allows the output from the rear of the driver to resonate a reflex enclosure with acoustic volume 19 at frequencies within the 12 db/oct slope. The efficiency in the range of the transformation is moderate relative to the driver mid-band efficiency yet it allows a small low mass driver to use its' fast responding diaphragm to produce usable bass at frequencies determined by the EATL5. Almost any similar diameter driver 41 used if its compliance is not to stiff will generate the curves of FIG. 13C and FIG. 13D. The 1/4 wave positive pressure is a real-time mass component acoustically applied to the DD 3 to produce the enhanced low pass performance from the driver 41 as indicated in FIG. 13D for FIG. 6. The drivers' 41 mass and other parameters will affect distortion, efficiency and to some degree extreme frequency cut-off so optimum performance from a certain EATL/Reflex enclosure can be had through driver 41 choice. The efficiency of this type of bass system is still related to actual DD 3 area and it increases with a larger driver 41 as would be normal since more air molecules would be moved. Typically the low frequency output of large drivers 41 increase relative to mid-band output because of diaphragm area as mass deters output at higher frequencies. The DCEATL 5 low frequency system develops output from diaphragm area not geometry. The listening room, typically being an acoustic space with dimensional gain, also favors lower frequencies if they are present. The curve of FIG. 14C represents distant microphone placement when measuring the sub-bass system of FIG. 6. The room acts similar to the reflex enclosure in lifting the output at the lower bass frequencies as is seen in curve O by the big increase in gain in the 15 Hz octave in FIG. 14C relative to adjacent frequencies. FIG. 14A indicates the impedance of FIG. 5 and FIG. 6. The curves are overlaid to show how little the reflex box alters the resonant frequency and Q of the driver when it is connected. This indicates that the positive pressure within the EATL 5 dominates the drivers' impedance with little effect on the driver 41/EATL 5 operating parameters from the addition of the acoustic low pass filter. In FIG. 14A the large peak K represents the impedance of the driver in FIG. 5. The small peak J trailing the driver peak L in FIG. 14A would be considered the ports peak with a conventional reflex enclosure and the output would fall off rapidly as the frequency approaches this peak. This peak represents the same EATL 5 peak that was observed in the impedance peak of FIG. 12B, FIG. 13A, FIG. 13B except that it has been pushed below the driver resonance due to the close coupling of the EATL5. It has been shown that increasing the length of the EATL5 will lower the EATL5 peak, as close coupling will also cause. Depth migration is greater under high pressure causing the 1/4 wave signal to appear at the driver diaphragm below box tuning. It is also observed as shown in FIG. 13D that the output will fall after the main EATL 5 peak but the close coupling will load the driver to the EATL5 cut-off frequency of near 15 Hz. If it is observed carefully the output curve R of FIG. 13D of the sub-bass enclosure FIG. 6 has its' highest output at the EATL 5 peak of 35 Hz which is an extraordinary feature. The reason for this can be seen if the curves of FIG. 14D are observed. FIG. 14D represents the phase curves of the subwoofer in FIG. 6. The curves are overlaid to show their relationships.
Moray, I was checking the links out that you provided in the other thread. The patent website is the most frustration I have encountered in a long time. I was able to find a patent by Jan Plummer for this thing but I think it was an earlier one, dated Mar. 9, 04 or something like that. I have been unsuccessful at searching for anything else, and in fact I can't even find the same patent I found before anymore. I will have to read it a dozen more times but I think I have a decent handle on what's going on in there and it's fascinating. I would like you to send me any more info you have, my email is no longer blocked (I think) and I also checked the option for private messages, although I'm not even sure how to access that feature.
Anyway, the Plummer design obviously has merit, based on it's size, specs, measured output vs driver size. But without a bit more detail I don't think I would try to do anything but copy the commercial model. I'm not sure who would be buying at $1200 each though, as I would need about 4 of them and it looks like I could make the box (driver not included) for about $10. Actually I have lots of scrap wood, the only thing I would need is the recommended foam/insulation/whatever it is they block the front radiation of the driver with.
Anyway, the Plummer box seems like a great idea but I wouldn't even want to try to mod it for infrabass without lots more info, or at least trying to copy the commercial model first. I'm still all about the Holliman box for sub 20 hz content.
MIKE - I searched the website and found a couple of references to Holliman but not the thread you were talking about. I'll try later when I have more time, or maybe if you want to post a direct link that might work better. I too have seen a couple of not so glowing reviews of the Holliman box, but in each case it was because the builder was not aware until later that this box was not supposed to have "normal" subwoofer range, for example, they were expecting it to play 30 - 100 hz, not 5 - 25. Either way, I want that link and any other info you may have on the Holliman box.
Thanks for your time and ideas, guys.
Anyway, the Plummer design obviously has merit, based on it's size, specs, measured output vs driver size. But without a bit more detail I don't think I would try to do anything but copy the commercial model. I'm not sure who would be buying at $1200 each though, as I would need about 4 of them and it looks like I could make the box (driver not included) for about $10. Actually I have lots of scrap wood, the only thing I would need is the recommended foam/insulation/whatever it is they block the front radiation of the driver with.
Anyway, the Plummer box seems like a great idea but I wouldn't even want to try to mod it for infrabass without lots more info, or at least trying to copy the commercial model first. I'm still all about the Holliman box for sub 20 hz content.
MIKE - I searched the website and found a couple of references to Holliman but not the thread you were talking about. I'll try later when I have more time, or maybe if you want to post a direct link that might work better. I too have seen a couple of not so glowing reviews of the Holliman box, but in each case it was because the builder was not aware until later that this box was not supposed to have "normal" subwoofer range, for example, they were expecting it to play 30 - 100 hz, not 5 - 25. Either way, I want that link and any other info you may have on the Holliman box.
Thanks for your time and ideas, guys.
Here's the link for the Jan Plummer patent.
http://appft1.uspto.gov/netacgi/nph...79".PGNR.&OS=DN/20040251079&RS=DN/20040251079
If you scroll to the bottom and click on "images" you'll need a TIFF viewer to see them. I use this viewer. It's free.
http://www.alternatiff.com/
I found a member on AVforums who has built a Holliman box. I contacted him and I'm waiting for his reply. I'm interested to find out how it worked for him. If it looks promising I'll try building one to see what it's all about.
Mike
http://appft1.uspto.gov/netacgi/nph...79".PGNR.&OS=DN/20040251079&RS=DN/20040251079
If you scroll to the bottom and click on "images" you'll need a TIFF viewer to see them. I use this viewer. It's free.
http://www.alternatiff.com/
I found a member on AVforums who has built a Holliman box. I contacted him and I'm waiting for his reply. I'm interested to find out how it worked for him. If it looks promising I'll try building one to see what it's all about.
Mike
Hi just a guy,
The plots I shown above are very accurate to what I could hear and also measure when testing and why not involve MJK and discuss the validity of his software for this case, as the infra source is important in the first hand and not the eventually ‘room aspects’ that easily can be handled separated, as usual with speakers?
Quote at text from: ’ MY PERSONAL THOUGHTS ON HOW AND WHY THE HOLLIMAN DESIGN WORKS.doc’
“It is described as incredibly clean, low distortion, very powerful, surprisingly efficient bass that increases in volume as it decreases in frequency.”
The expected result of the so-called unique loading method didn’t show up when I tested, no broadening to lower frequencies but rather some sort of simple band pass action instead, an efficiency loss, with dampening of higher frequencies as a result of my Holliman speaker setup.
I spent this weekend a lot of hours testing this Holliman phenomenon with a real setup (40L box and Peerless XLS 10”) and came to the conclusion that the high efficiency 5 to 25 Hz bandwidth probably is only a myth for this type of infra speaker.
Where is the optimal volume velocity to sound pressure transformer and where is the pronounced effect of the unique method?
Is there an infra seesaw kind of energy action between the speaker volume and the connecting room that obey other laws not yet described in physics or is understood with the good acoustic modeling software I used? I doubt.
I tested with the door hermetically closed (concrete high Q walls in a 6m x 4,5m x 2.4m room) and found no more infra SPL than what also can be expected with a sub with good excursion capability (fs lower than 20 Hz) placed at 2 to 3 m close to a room corner.
Velocity coupled, ok but only benefit for suppression of frequencies higher than the lowest resonance.
The volume velocity plummets rapidly down under 10 Hz as expected, below the lowest resonance and so did the SPL.
This indicates constant low acoustic impedance and when meet with the free air impedance is equivalent to a very low efficiency at the terminus.
There was no ‘bandwidth broadening’ action at all except for a certain flattening of the higher in band frequencies.
Despite I was from the beginning very suspicious and already knew the outcome; I also tested with different port lengths at the terminus side to see if any magical action could take place.
A lot of port noise at higher levels and other artifacts could easily be heard, like high gain modal standing waves caused by driver distortion overtones and maybe because my sub amplifier only has LP LR 12-dB/octave attenuation at 40 Hz.
This was not enough and probably 24-dB/octave could have worked better. I will later test with my DEQ 2496 hooked up, if I have some time left over.
External box loading below the lowest modals;
I believe below the lowest modal standing wave that can occur in a closed room with no losses or leaks, is that the infra pressure must obey the very simple physical law of equating partial pressures and volumes; p1 x V1 = p2 x V2.
If the room size is 60 m^3 and the speaker is 60 L the possible room pressure is a 1/1000 and equals – 60 dB of what is produced inside the speaker cabinet.
For frequencies slightly lower than 20 Hz to be heard the pressure inside a speaker box must exceed 140 dB!
Most speakers operating at this internal level produce a lot of artifacts through the port that certainly can easily be heard if a suitable low pass filter is connected at 25 Hz.
B