Highwood Audio...
was the parent company started by Paul Burton and myself. Paul had the idea for a traveling wave driver. I had been working on ESL's at the time. The two of us worked solid for a year and developed a line source version with a magnetic drive. Shortly after doing this work we realized that we had a potential product and started the company with a lot of quality help and good fortune.
I would not say that Bill designed the driver however his assistance and design input along with his machine work skill was what made it all possible to come together. The basic team at that time was Paul myself, John Wright with Bill making the motor parts. Paul's Dad designs Circlitrons and when we took our motor design to him for an assesment the said there was nothing left to do. That felt pretty great comming fro him. I will also say that the point source design was the undoing of our little company. All the original designs had been line source designs and I can say that to this day I have not heard the equal in terms of image quality. Only the the big German MBL's do the kind image we were getting from the line sourcees. We feared that magnet structure cost would kill us and time was pressing as we had borrowed a lage sum of money to proceed. We had been playing with very inexpensive point source design motors at the time and felt that we could solve the problems they had by designing our own. With the commitment made we shelved the line source and proceeded with the point source version. The cost in time and development expenses struck a near killing blow. At the end of the day we had a low mass single layer 4 ohm coil point source with good enough bandwidth. The motor cost alone was about $360.00 each (this in 1989). The driver used ferro fluid as a liquid bearing (a first as far as I know) to replace the spider to stabilize the coil as spider talk through a 150 gage mylar diaphragm was not acceptable. While the point source was very good we never achieved the quality of sound from it that we had from the line source design. The point source design was a traveling wave design and could be discribed as a mechanical version of the Quad 63 approach. I liked to think of it as a hornless horn loaded design.
If you consider the old pebble in a pond visualization the VC pokes the film diaphragm and launches a forward traveling wave into the air the size if the coils cone (in this case 1.25 inche). At the same time the diaphragm comes back to centre and a secondary wave spreads outward along the diaphragm toward the frame. The leading edge of this wave in the diaphragm then spreads out the outside edge of the forward in air traveling wave . So the traveling wave acts like a wave guide forming the resulting wave front. This then generates a half hemisphere wave front (we are talking now of just half of what is going on as this is a dipole design). You need to do some fancy work at the frame to eat up the bulk of the reflection which would normally occur. Additional diphragm damping to controll tympanic resonances is also required. We did all of the initial work by ear and by the seat of our pants. Later on Bill Perkins built us a world class measurement system. This was both a good and a bad thing as it is easy to follow the lead given by the measured data and not trust your ears. We got over that issue and developed a fine speaker, not perfect but time and money were pushing hard. A very simple idea but very difficult to implement.
Considering the billions that must have been invested and spent in the following years by NXT think that what we did stands as a superior overal acomplishment. The time and money that we spent to jump into the point source (given that a line source had been just about ready to go to market) combined with issues that our distribution partner (Sumo) had were too much to overcome and things unwound. Paul cut loose from the project and was given a golden handshake to go away. We ended up having our investors essentally float (buy) Meitner and merged the two companies and things went worse from there on. Lots of reasons but not worth going into. That's the story in a nut shell. Regards Moray James.
was the parent company started by Paul Burton and myself. Paul had the idea for a traveling wave driver. I had been working on ESL's at the time. The two of us worked solid for a year and developed a line source version with a magnetic drive. Shortly after doing this work we realized that we had a potential product and started the company with a lot of quality help and good fortune.
I would not say that Bill designed the driver however his assistance and design input along with his machine work skill was what made it all possible to come together. The basic team at that time was Paul myself, John Wright with Bill making the motor parts. Paul's Dad designs Circlitrons and when we took our motor design to him for an assesment the said there was nothing left to do. That felt pretty great comming fro him. I will also say that the point source design was the undoing of our little company. All the original designs had been line source designs and I can say that to this day I have not heard the equal in terms of image quality. Only the the big German MBL's do the kind image we were getting from the line sourcees. We feared that magnet structure cost would kill us and time was pressing as we had borrowed a lage sum of money to proceed. We had been playing with very inexpensive point source design motors at the time and felt that we could solve the problems they had by designing our own. With the commitment made we shelved the line source and proceeded with the point source version. The cost in time and development expenses struck a near killing blow. At the end of the day we had a low mass single layer 4 ohm coil point source with good enough bandwidth. The motor cost alone was about $360.00 each (this in 1989). The driver used ferro fluid as a liquid bearing (a first as far as I know) to replace the spider to stabilize the coil as spider talk through a 150 gage mylar diaphragm was not acceptable. While the point source was very good we never achieved the quality of sound from it that we had from the line source design. The point source design was a traveling wave design and could be discribed as a mechanical version of the Quad 63 approach. I liked to think of it as a hornless horn loaded design.
If you consider the old pebble in a pond visualization the VC pokes the film diaphragm and launches a forward traveling wave into the air the size if the coils cone (in this case 1.25 inche). At the same time the diaphragm comes back to centre and a secondary wave spreads outward along the diaphragm toward the frame. The leading edge of this wave in the diaphragm then spreads out the outside edge of the forward in air traveling wave . So the traveling wave acts like a wave guide forming the resulting wave front. This then generates a half hemisphere wave front (we are talking now of just half of what is going on as this is a dipole design). You need to do some fancy work at the frame to eat up the bulk of the reflection which would normally occur. Additional diphragm damping to controll tympanic resonances is also required. We did all of the initial work by ear and by the seat of our pants. Later on Bill Perkins built us a world class measurement system. This was both a good and a bad thing as it is easy to follow the lead given by the measured data and not trust your ears. We got over that issue and developed a fine speaker, not perfect but time and money were pushing hard. A very simple idea but very difficult to implement.
Considering the billions that must have been invested and spent in the following years by NXT think that what we did stands as a superior overal acomplishment. The time and money that we spent to jump into the point source (given that a line source had been just about ready to go to market) combined with issues that our distribution partner (Sumo) had were too much to overcome and things unwound. Paul cut loose from the project and was given a golden handshake to go away. We ended up having our investors essentally float (buy) Meitner and merged the two companies and things went worse from there on. Lots of reasons but not worth going into. That's the story in a nut shell. Regards Moray James.
Hi, moray james. I remember from another forum your mentioning you had been invoved with Sumo, which had been mentioned in the article also. I had thought to ask about this from you, but never got around to it.
I'm wondering if this different take on the concept, and it does seem different - a "soft piston" using a foam sandwich - has any merit. This would seem to combine your original idea with a larger soft piston area. It would limit the bandwidth to the bass region, and should deal with many of the issues that the EnABL and Mamboni processes deal with, though maybe not so well nor so elegantly. Instead of a large woofer mounted in a larger panel, the woofer membrane itself would form most of the front baffle - or the side, or sides, of a fuller arrangement.
Wish I could have heard your line sources. Ever think of trying to bring them to market again? Or is the meat grinder world of audio business not something you want to face again?
I'm wondering if this different take on the concept, and it does seem different - a "soft piston" using a foam sandwich - has any merit. This would seem to combine your original idea with a larger soft piston area. It would limit the bandwidth to the bass region, and should deal with many of the issues that the EnABL and Mamboni processes deal with, though maybe not so well nor so elegantly. Instead of a large woofer mounted in a larger panel, the woofer membrane itself would form most of the front baffle - or the side, or sides, of a fuller arrangement.
Wish I could have heard your line sources. Ever think of trying to bring them to market again? Or is the meat grinder world of audio business not something you want to face again?
this was a little different...
Our original line source design used a very thin tight diaphragm in conjunction with periferal wave traps which loaded each side of the diaphragm. The diaphragm was fairly thin prior to stretching and I believe that this resulted in a far faster wave transmission than with the thicker far lower tensioned diaphragm of the point source version. Yet with the point source version we were able to measure with a B&K capsule mic facing the outside edge of the speaker frame (same plane as the diaphragm) 10 KHz which would never happen with a conventional planar such as a maggie or an ESL.
berm: Soft won't get you there. If you want to have the waveform shape preserved you have to aim to transmit in the diaphragm at as close to the speed of sound in air as possible. Remember the sucess that guys were getting gilding paper cones with aluminum foil to speed the surface transmission of energy? Same thing here, once you launch the wave into the air you have to attempt to match the speed of transmission in the diaphragm to that in air or you will get waveform deformation. We used 1.5 mil mylar on the Sumo Aria diaphragm and heavier would have been nice for better bass reproduction.
You borrow a lot of money to make a business go and things change. Reasons for doing things change and you have investors looking over your shoulder. Partner relations change. Enough stuff went down you could have choked a horse on it so yes that took its toll. There was a bad taste associated with the whole thing for a very long time.
I am toying with an old idea from a long time ago that may or may not ever see the light of day. If it does I will let you know. Regards Moray James.
Our original line source design used a very thin tight diaphragm in conjunction with periferal wave traps which loaded each side of the diaphragm. The diaphragm was fairly thin prior to stretching and I believe that this resulted in a far faster wave transmission than with the thicker far lower tensioned diaphragm of the point source version. Yet with the point source version we were able to measure with a B&K capsule mic facing the outside edge of the speaker frame (same plane as the diaphragm) 10 KHz which would never happen with a conventional planar such as a maggie or an ESL.
berm: Soft won't get you there. If you want to have the waveform shape preserved you have to aim to transmit in the diaphragm at as close to the speed of sound in air as possible. Remember the sucess that guys were getting gilding paper cones with aluminum foil to speed the surface transmission of energy? Same thing here, once you launch the wave into the air you have to attempt to match the speed of transmission in the diaphragm to that in air or you will get waveform deformation. We used 1.5 mil mylar on the Sumo Aria diaphragm and heavier would have been nice for better bass reproduction.
You borrow a lot of money to make a business go and things change. Reasons for doing things change and you have investors looking over your shoulder. Partner relations change. Enough stuff went down you could have choked a horse on it so yes that took its toll. There was a bad taste associated with the whole thing for a very long time.
I am toying with an old idea from a long time ago that may or may not ever see the light of day. If it does I will let you know. Regards Moray James.
ScottG said:While the 12NDA520 is a fantastic driver.. I'm not so sure this is the driver that should be run fullrange.. Dispersion becomes poor about 1.4 kHz, and it looks like at 1.8 kHz you start into time domain problems.
Now of course you *might* be able to modify the driver to an extent to clear things up (in time).. but that still won't do anything for the dispersion pattern.
It could be that the Tone Tubby is FAR better with time at the top of its passband.. don't know. I also don't know about its horizontal dispersion (which, including price, is why I didn't mention it to Paul in his thread).
One possibility to improve in-room power response while even further limiting dispersion, (creating a more linear off-axis response), and near time room reflections would be a hypercardoid based on a free air bipole with a pair of 12" drivers (mounted back to back). It would however need a very similar dispersion pattern at higher freq.s - which could be accommodated via those 18 sound horns. (in a paired bipole config.). Note that such a config. for the free air bipole would significantly reduce frame energy build up, (provided the two drivers were connected physically via a high transmission material), and mildly reduce 2nd order distortion. More importantly though, it should reduce time problems at the top of the driver's passband (..when compared to virtually any other mounting scheme). Additionally, you could always vary the rear in-phase output for most of the passband with a simple acoustic trap.
(Note that such a bipole will NOT have the side combing problems of traditional bipoles).
Well, it's an idea.
Many many thanks for all the good stuff in the Large Midrange for OB thread. Tons of information, fabulous photos and test data, along with a wealth of subjective information what this stuff actually sounds like.
As for the whole idea of "pushing" a large diaphragm to the top of its range, good question about the 12" Alnico Tone Tubby vs the 18Sound 12NDA520 . The TT is plenty directional, as you'd expect from a straight-sided cone, but the hemp cone does have good damping qualities at HF, as shown by my MLSSA measurements on a flat baffle.
A more "classical" approach would be the 18Sound 8NMB420, with near-flawless FR and quite respectable T/S normalized efficiency of 95.6 dB/metre. Considering that I'm looking at de facto bi-amplification of the midbass and bass drivers anyway, that could remove the unpleasant necessity of a passive highpass filter at 200 ~ 250 Hz for the 8NMB420. Good-quality caps in the 100 uF range pretty much don't exist - and the trick of a smaller film cap to bypass a yucky back-to-back electrolytic doesn't do much to get rid of the electrolytic coloration. The better the driver, the more poor-quality parts in the crossover become audible, unfortunately.
So there are several options for the widerange driver, depending on how much I want to take them out of their recommended ranges - or what I ask of the tweeter. The 18Sound ND1060 plastic-film diaphragm CD combined with the XT1086 80 x 60 elliptical horn look interesting, particularly since I'm strongly considering a pair of XD125's on the rear of the speaker - one pointing straight back to illuminate the back wall, and the other pointing out at the side wall. Both the ND1060 and XD125 use the same plastic-film diaphragms and similar horn profiles, so there shouldn't be a conflict in the dissimilar-driver coloration for the front and rear sound.
As for the bipole - or hypercardiod - using a pair of 12" drivers, one in front of the other, I'm very concerned about degradation of impulse response. Diaphragms are pretty much transparent acoustically, and the impulse from the rear driver would travel right through the front one - but with a 0.4 to 0.5 mSec delay, depending how close you can get the drivers to each other. That's going to create large ripples in the time response, comb filtering in the frequency response, and some narrow lobes at high frequencies. It would certainly tax the crossover design, since there would have to be a very sharp cut (probably 24 dB/oct) before the comb filtering starts disrupting things. There's nothing the crossover could do to fix the time domain, though.
But - even though I am wary of doing this in the midrange region - the deep bass is quite another thing. In fact, I was thinking along similar lines this morning before I turned on the computer and read your message.
I was considering a version of the speaker with a pair of 12" drivers side by side, when it dawned on me that they don't need to have the same type of enclosure. In fact, one could be in a closed-box (a simple monopole), and the other could be in a short resistive-loaded tube (a dipole). Just as in a microphone, this creates a cardioid speaker.
But then I started thinking about the inter-driver phase relationships and the effect on the cardioid pattern. If the rolloff of the monopole creates a 180 phase rotation (relative to the dipole), that would shift the cardioid pattern all the way from front to back! Not a small difference to the sound, and something that's not obvious from inspection of the FR curves for each type of loudspeaker enclosure.
Since closed-boxes, vented-boxes, resistive-loaded boxes, TQWT's, etc. are all minimum-phase highpass filters, the phase relationship is predicted by the frequency response. For Butterworth filters, the phase shift at the -3 dB frequency is half of the phase shift at the ultimate attenuation frequency. So for a 12 dB/oct highpass (a closed box), the phase shift is 90 degrees at -3 dB, and approaches 180 degrees at zero frequency (although it gets pretty close one decade away from the -3 dB frequency). Similarly, for a 24 dB/oct highpass (vented boxes, TQWT's, etc.), the phase shift is 180 degrees at the -3 dB frequency, and approaches 360 degrees a decade lower.
This has implications for combining a dipole with an adjacent box enclosure. The dipole's natural 1/f rolloff is creating a mild degree of phase shift (90 degrees or less), depending how far away from the 1/f transition frequency we are (the path-length of the baffle). This is fairly close to what the closed-box is doing, but we're going to get in trouble with the vented box (in all its forms, including back horns) thanks to its higher phase shift interfering with the dipole. This problem would be greatly worsened if the TQWT or horn have ripples in their response, which creates associated phase shifts. By themselves, these phase shifts are reasonably benign, but could create cancellation problems if the TQWT or horn output is summed with a dipole.
So I guess the moral of the story is: we have to be very careful about both phase and time relationships when we have two or more drivers close to each other. If the drivers have well-matched phase relationships and are on a common plane (at the same distance from the listener), things are fairly straightforward. This why combining dissimilar drivers at high frequencies gets us in trouble, because small differences in FR result in large differences in phase, rotating the polar pattern.
film diaphragm
I don't want to get this thread too far off topic, since I got interested because I wanted to read what Lynn Olsen's thinking was on speakers at this time. However, another question for moray james: With the "Spandex woofer", as it seems to operate somewhat more like a piston than a bending wave device, do you still think it would be bad as a bass driver? I was thinking that the things that inherently limit its use as a fullrange driver might make it a good bass driver. It would have a natural low roll-off, and be able to move a large mass of air. Since most of the pad is moving rather than starting as a point (mostly), would this cause a wave at the lower frequencies to deform too much? I suppose the foam core in the sandwich could be replaced by a more rigid panel, but then we are getting into a different area with its own problems.
I'm mostly looking for potential options for a bass dipole to augment whatever full/widerange driver I would mount topside. And I'm learning a lot about what I should look for and how to treat it in Lynn's and others' posts on this thread.
p.s. I saw your post on another forum about the CyberHome DVD & picked one up. Nice, and thanks, though it wasn't written to me.
I don't want to get this thread too far off topic, since I got interested because I wanted to read what Lynn Olsen's thinking was on speakers at this time. However, another question for moray james: With the "Spandex woofer", as it seems to operate somewhat more like a piston than a bending wave device, do you still think it would be bad as a bass driver? I was thinking that the things that inherently limit its use as a fullrange driver might make it a good bass driver. It would have a natural low roll-off, and be able to move a large mass of air. Since most of the pad is moving rather than starting as a point (mostly), would this cause a wave at the lower frequencies to deform too much? I suppose the foam core in the sandwich could be replaced by a more rigid panel, but then we are getting into a different area with its own problems.
I'm mostly looking for potential options for a bass dipole to augment whatever full/widerange driver I would mount topside. And I'm learning a lot about what I should look for and how to treat it in Lynn's and others' posts on this thread.
p.s. I saw your post on another forum about the CyberHome DVD & picked one up. Nice, and thanks, though it wasn't written to me.
Re: this was a little different...
Hello there Moray, maybe you could answer something I've always been curious about: when a material with a high speed of sound (like aluminum) is bonded to something with a slow speed of sound (like paper), what happens to the speed of sound in the new composite material?
Is it as fast as aluminum? Are there two wavefronts travelling at different speeds through the new composite, with the first arrival followed by an echo? Or does the faster speed win, with altered decay characteristics compared to either material on its own?
moray james said:
Hello there Moray, maybe you could answer something I've always been curious about: when a material with a high speed of sound (like aluminum) is bonded to something with a slow speed of sound (like paper), what happens to the speed of sound in the new composite material?
Is it as fast as aluminum? Are there two wavefronts travelling at different speeds through the new composite, with the first arrival followed by an echo? Or does the faster speed win, with altered decay characteristics compared to either material on its own?
well...
berm I think that you are looking at a differnt mode of operation and with the high mass of your structure (diaphragm) you will have a bigger and more complicated job of fudging it all into polite operation. I am afraid you are on your own there. People have done this to varying degrees over the years. one of our early prototypes used a head phone VC and motor driving an 8.5 x 11 inch piece of 1/8 inch glass plate. Not very loud but boy did piano sound real and that was about it with no midbass or lower.
You might try a bass version of a Lineaum driver where you build in intentional loss into the diaphragms. Woth a try.
Lynn I think that it ends up somewhere in the middle. Bud has been discussing surface energy and I think that is where the thin foil comes into paly for the most part. Unless you have real balanced constrained layers (prestressed even better) a thin foil layer is not going to add much if any stiffness to the base substraite material (cone), if anything given the foil and the adhesive used you probably pick up some extra mass and some damping of upper modes of the cone.
I suspect that you are on track with thinking that the faster material (harder) lets the surface energy launch additional useful sound but that as a composite you get a little effect of the harder on the softer(in this particular example). With out laser measurement it would be a Dog's breakfast to really figure out properly but you can sound such stuff out by ear. I think tha you (and Bud) re right there is the acoustical wave to deal then there is the surface energy to deal with as well. Wish I could offer more information /answers but that is as much as I know. Regards Moray James.
berm I think that you are looking at a differnt mode of operation and with the high mass of your structure (diaphragm) you will have a bigger and more complicated job of fudging it all into polite operation. I am afraid you are on your own there. People have done this to varying degrees over the years. one of our early prototypes used a head phone VC and motor driving an 8.5 x 11 inch piece of 1/8 inch glass plate. Not very loud but boy did piano sound real and that was about it with no midbass or lower.
You might try a bass version of a Lineaum driver where you build in intentional loss into the diaphragms. Woth a try.
Lynn I think that it ends up somewhere in the middle. Bud has been discussing surface energy and I think that is where the thin foil comes into paly for the most part. Unless you have real balanced constrained layers (prestressed even better) a thin foil layer is not going to add much if any stiffness to the base substraite material (cone), if anything given the foil and the adhesive used you probably pick up some extra mass and some damping of upper modes of the cone.
I suspect that you are on track with thinking that the faster material (harder) lets the surface energy launch additional useful sound but that as a composite you get a little effect of the harder on the softer(in this particular example). With out laser measurement it would be a Dog's breakfast to really figure out properly but you can sound such stuff out by ear. I think tha you (and Bud) re right there is the acoustical wave to deal then there is the surface energy to deal with as well. Wish I could offer more information /answers but that is as much as I know. Regards Moray James.
Surface Propagation
Well, I was thinking of an inverse to the Mamboni mod where you add triangular-shaped strips of metal foil to a paper cone. Similarly, the EnABL treatment could be applied as simply as a stencil, or the lift-off lettering used for front panels.
I've also wondered for many years how an amorphous metal like gold foil would behave, as opposed to metals with crystalline structure. All of these things must surely affect wave propagation through the cone.
I've kind of gone past rescuing those coaxes - every blessed one of them has the worst freq resp curves imaginable. That indicates geometrical problems, like severe standing waves in the cone attachment/VC former area, or something ugly like a dustcap that has one or more cavity resonances.
Fancy cone treatments can clean up the cone and greatly reduce energy storage, but I don't see them correcting gross abnormalities like bad dustcaps or design errors in the cone attachment/VC former area. You put a perfect driver in a tin can, it's still gonna sound like a tin can.
I certainly sympathize with the horrendous difficulties that confronted your design team. Optimizing rigidity (low IM distortion) while keeping desirable energy-dissipation characteristics (rapid decay and freedom from resonance) seems to have eluded driver designers for many decades.
The current crop of audiophile drivers actually seems to be going backwards in this area, despite the availability of greatly superior measurement tools. That's why I'm looking at archaic materials like hemp and HF Olson's work - I suspect a great deal of "company proprietary" information has simply been lost over the last several decades, due to corporate infighting, good engineers leaving and taking their intellectual property with them, and VC losing interest in alternative technologies. It would be tragic if all the hard work your development team put in simply disappeared in a flurry of hand-written notes.
I briefly worked for NASA in the summers of 1969 and 1970, and was horrified a few years when I found out the Saturn V technology no longer exists - the USA would have to start from scratch if we wanted to return to the Moon. It's an unsettling thought that aerospace technology has actually regressed - quite a bit - over the last 35 years.
The SR-71: scrapped, all tooling destroyed (by order of Nixon)
The Boeing 2707 Mach 3 Trans-Pacific SST: scrapped by Congress
The Space Transportation System with a continuously occupied moonbase, nuclear-engined (NERVA) long-distance interplanetary transports, and a Mars Mission by 1990: scrapped, leaving only a crippled Space Shuttle with degraded performance specs
Jet transportation: airspeeds are slower than they were in 1970 (to save fuel), passengers must use a hub-and-spoke system instead of direct city-to-city flights (to maximize economy for the airlines), and levels of service that combine Greyhound-bus-terminal crowding, filth and dirt with Federal prison treatment at every airport.
No wonder the elites avoid all this unpleasantness and are driven in their limos directly to their corporate jets, where the pilot of the plane meets them, hangs up their coats, and serves them a pleasant refreshment from the bar before taking off - in planes that fly higher and faster, and go directly where they want to go.
moray james said:
Well, I was thinking of an inverse to the Mamboni mod where you add triangular-shaped strips of metal foil to a paper cone. Similarly, the EnABL treatment could be applied as simply as a stencil, or the lift-off lettering used for front panels.
I've also wondered for many years how an amorphous metal like gold foil would behave, as opposed to metals with crystalline structure. All of these things must surely affect wave propagation through the cone.
I've kind of gone past rescuing those coaxes - every blessed one of them has the worst freq resp curves imaginable. That indicates geometrical problems, like severe standing waves in the cone attachment/VC former area, or something ugly like a dustcap that has one or more cavity resonances.
Fancy cone treatments can clean up the cone and greatly reduce energy storage, but I don't see them correcting gross abnormalities like bad dustcaps or design errors in the cone attachment/VC former area. You put a perfect driver in a tin can, it's still gonna sound like a tin can.
I certainly sympathize with the horrendous difficulties that confronted your design team. Optimizing rigidity (low IM distortion) while keeping desirable energy-dissipation characteristics (rapid decay and freedom from resonance) seems to have eluded driver designers for many decades.
The current crop of audiophile drivers actually seems to be going backwards in this area, despite the availability of greatly superior measurement tools. That's why I'm looking at archaic materials like hemp and HF Olson's work - I suspect a great deal of "company proprietary" information has simply been lost over the last several decades, due to corporate infighting, good engineers leaving and taking their intellectual property with them, and VC losing interest in alternative technologies. It would be tragic if all the hard work your development team put in simply disappeared in a flurry of hand-written notes.
I briefly worked for NASA in the summers of 1969 and 1970, and was horrified a few years when I found out the Saturn V technology no longer exists - the USA would have to start from scratch if we wanted to return to the Moon. It's an unsettling thought that aerospace technology has actually regressed - quite a bit - over the last 35 years.
The SR-71: scrapped, all tooling destroyed (by order of Nixon)
The Boeing 2707 Mach 3 Trans-Pacific SST: scrapped by Congress
The Space Transportation System with a continuously occupied moonbase, nuclear-engined (NERVA) long-distance interplanetary transports, and a Mars Mission by 1990: scrapped, leaving only a crippled Space Shuttle with degraded performance specs
Jet transportation: airspeeds are slower than they were in 1970 (to save fuel), passengers must use a hub-and-spoke system instead of direct city-to-city flights (to maximize economy for the airlines), and levels of service that combine Greyhound-bus-terminal crowding, filth and dirt with Federal prison treatment at every airport.
No wonder the elites avoid all this unpleasantness and are driven in their limos directly to their corporate jets, where the pilot of the plane meets them, hangs up their coats, and serves them a pleasant refreshment from the bar before taking off - in planes that fly higher and faster, and go directly where they want to go.
you might consider...
cryo treating your foil as this has the affect of reducing material surface tension so that oought to speed the foil up. Gold leaf sound like an experiment to check, you can cryo that as well. If you want I would be happy to cryo treat your foil materials for you if there is no local treater willing to do so for free, just PM me for my address and send it over (I am in Calgary so it won't take long back and forth in the mail).
Thought I would mention that Tannoy do sell (at much reduced cost a lot of drivers through thier pro and or install branch. They have a new 4 inch true dual concentric that can be had in an inwall frame for about $150.00 each. This is the same driver that they use in the miny westminster design which sell for about $2K to the audio market. I have listened to these and they are very good and can play loud around 103 db continous and peaks around 113 db (single units). They could make a cool scaled down version of your OB design and in a medium to smallish room be most of what people are looking for. Not to mention that the project cost would be reasonable. Tannoy have 6.5 inch DC and 8" DC drivers available as well. You are right in that you can not make that silk purse from the pigs ear so the Tannoy ought to get you as close as you can get with this technology for a reasonable prive. Close enugh to decide if custom drivers are worth investing in.
I think that the foil idea (wedges) could be combined with the felt wedge idea. Sounds like the impact of the felt wedge treatment goes beyound what anyone could expect from a damping (mass) point of view. Would be reasonable to think that the increase of air load due to the fiber tangle impacts the impedance match of the cone/felt combination to the surrounding air. Might the Olson multi cone design have a similar impact? Not only in respect to increasing the cone surface area but also in terms of complex air load on the driver? I wonder if (don't laugh now) if a speaker might benefit from tha addition of a brush cut wig? If you placed a wig like web with hair like fibers on a cone which started short at the VC and grew longer toward the outer edge of the cone the surface energy would get progressively distributed up off of the cone surface? This would kind of tie into your idea of the mesh termination. Hair fiber direction and length would be easy to control. Might also explain why ZZ Top sound so good. This idea combines to some degree both the enable idea along with the felt
This reminds me I have some raw factory piezo cones made by motorola (felted paper) about 1.75" total dia. including a small flange. These are the cones used in piezo drivers. If you are interested in experimenting with some of these on a fullrange driver cone I would be happy to send you some. Let me know. You might be able to reproduce similar results to that Olson did. Combinning Bud's enable techniques to these cone might also produce results. Stands to reason that nobody will allow you to play with thier Olson designed RCA's so this might be the closest that you are going to get for free (almost) you still need to provide a raw driver set to play with. Best regards Moray James.
cryo treating your foil as this has the affect of reducing material surface tension so that oought to speed the foil up. Gold leaf sound like an experiment to check, you can cryo that as well. If you want I would be happy to cryo treat your foil materials for you if there is no local treater willing to do so for free, just PM me for my address and send it over (I am in Calgary so it won't take long back and forth in the mail).
Thought I would mention that Tannoy do sell (at much reduced cost a lot of drivers through thier pro and or install branch. They have a new 4 inch true dual concentric that can be had in an inwall frame for about $150.00 each. This is the same driver that they use in the miny westminster design which sell for about $2K to the audio market. I have listened to these and they are very good and can play loud around 103 db continous and peaks around 113 db (single units). They could make a cool scaled down version of your OB design and in a medium to smallish room be most of what people are looking for. Not to mention that the project cost would be reasonable. Tannoy have 6.5 inch DC and 8" DC drivers available as well. You are right in that you can not make that silk purse from the pigs ear so the Tannoy ought to get you as close as you can get with this technology for a reasonable prive. Close enugh to decide if custom drivers are worth investing in.
I think that the foil idea (wedges) could be combined with the felt wedge idea. Sounds like the impact of the felt wedge treatment goes beyound what anyone could expect from a damping (mass) point of view. Would be reasonable to think that the increase of air load due to the fiber tangle impacts the impedance match of the cone/felt combination to the surrounding air. Might the Olson multi cone design have a similar impact? Not only in respect to increasing the cone surface area but also in terms of complex air load on the driver? I wonder if (don't laugh now) if a speaker might benefit from tha addition of a brush cut wig? If you placed a wig like web with hair like fibers on a cone which started short at the VC and grew longer toward the outer edge of the cone the surface energy would get progressively distributed up off of the cone surface? This would kind of tie into your idea of the mesh termination. Hair fiber direction and length would be easy to control. Might also explain why ZZ Top sound so good. This idea combines to some degree both the enable idea along with the felt
This reminds me I have some raw factory piezo cones made by motorola (felted paper) about 1.75" total dia. including a small flange. These are the cones used in piezo drivers. If you are interested in experimenting with some of these on a fullrange driver cone I would be happy to send you some. Let me know. You might be able to reproduce similar results to that Olson did. Combinning Bud's enable techniques to these cone might also produce results. Stands to reason that nobody will allow you to play with thier Olson designed RCA's so this might be the closest that you are going to get for free (almost) you still need to provide a raw driver set to play with. Best regards Moray James.
Having worked as a lowly GS-4 Graphics Aide for NASA HQ in the glory years gave me a ringside seat in what should have been the technology of the Seventies, Eighties, and Nineties. Surprisingly, I had no security classification, and signed no non-disclosure agreements, yet I was making 8 x 10 Vu-Graphs for presentations for Von Braun and top management, and was the one that tape-recorded the meetings for later transcription. As a result, I saw, and heard, all of the plans that NASA had for the years 1970 through 2000.
The Space Shuttle we have now is a militarized travesty of the original. The original was to have used JT-79 engines modified to run on liquid hydrogen, giving it the ability to fly back and land on any airport in the world, under controlled powered flight. The first-stage launcher was designed to have a fly-back capability as well, and looked like a really big delta-winged rocket.
Since the Space Shuttle is basically a glorified low-altitude truck, without the ability to attain high-altitude synchronous orbit, a complementary system called the Space Tug was intended for visits to synchronous and above. A version of the Space Tug was optimized for visits to the moon and back, supplying the moonbase from Low Earth Orbit.
The Apollo missions were designed to continue indefinitely, building up a moonbase of discarded LEM parts (the middle habitation module), and planned to be continuously occupied from 1975 onward. Experience gained at the moonbase was to be applied to the long-duration Mars mission, planned for the mid-Nineties (that was the "conservative" schedule - the "aggressive" schedule had them landing in 1983).
We got none of that. Instead, we got Vietnam, a succession of resource wars that continue to this day, and what appears to be class war (marketed to the public as globalism). The USA had a choice between the future of Kubrick's 2001 (which was quite accurate at the time) and an empire, and chose empire.
All of this is to underscore the point that the future doesn't always bring advancements - or if it does, it may happen somewhere else, not the center of an empire. We have the Internet (free pR0n!) and almost-free electronics from China, but many other technologies have stagnated or gone backward. Real per-capita incomes have stayed the same since the 1970's, while prices for housing and automobiles have gone up in real dollars. Kind of a mixed bag - some wins, some loses. The Internet does let us get together and create new communities, hooray for that!
Returning to audio, I need to re-read HF Olson's books again, and look for those revealing little asides that point to areas of further research that were never undertaken. The whole experience of digging up Western Electric's Harmonic Balancer was a shock - here's a circuit that is as important as negative feedback, by the people that invented negative feedback, that was lost to all of the literature after the Thirties. Gone. Forgotten. Invented by the most advanced electronics lab in the world, and still forgotten by the time of the Williamson in 1948.
So there's a lot of stuff to dig up, and why I most sincerely hope the work of BudP, Mamboni, and Moray is developed further, or at the absolute minimum, is widely published. Audio is filled with brilliant work that is forgotten for reasons that have nothing to do with technical merit.
It does make you think how much was lost when religious fanatics burned the Library of Alexandria, which contained all the knowledge of the classical world. What we have now are only scraps and scattered fragments, badly copied by a handful of medieval monks. We know they had batteries - what did they use them for? We know they had mechanical clocks - what else did they have? The emotional and spiritual center of classical Greek civilization were the Mysteries of Eleuisis - and we know almost nothing of a religious ceremony that was in use for a thousand years.
The Space Shuttle we have now is a militarized travesty of the original. The original was to have used JT-79 engines modified to run on liquid hydrogen, giving it the ability to fly back and land on any airport in the world, under controlled powered flight. The first-stage launcher was designed to have a fly-back capability as well, and looked like a really big delta-winged rocket.
Since the Space Shuttle is basically a glorified low-altitude truck, without the ability to attain high-altitude synchronous orbit, a complementary system called the Space Tug was intended for visits to synchronous and above. A version of the Space Tug was optimized for visits to the moon and back, supplying the moonbase from Low Earth Orbit.
The Apollo missions were designed to continue indefinitely, building up a moonbase of discarded LEM parts (the middle habitation module), and planned to be continuously occupied from 1975 onward. Experience gained at the moonbase was to be applied to the long-duration Mars mission, planned for the mid-Nineties (that was the "conservative" schedule - the "aggressive" schedule had them landing in 1983).
We got none of that. Instead, we got Vietnam, a succession of resource wars that continue to this day, and what appears to be class war (marketed to the public as globalism). The USA had a choice between the future of Kubrick's 2001 (which was quite accurate at the time) and an empire, and chose empire.
All of this is to underscore the point that the future doesn't always bring advancements - or if it does, it may happen somewhere else, not the center of an empire. We have the Internet (free pR0n!) and almost-free electronics from China, but many other technologies have stagnated or gone backward. Real per-capita incomes have stayed the same since the 1970's, while prices for housing and automobiles have gone up in real dollars. Kind of a mixed bag - some wins, some loses. The Internet does let us get together and create new communities, hooray for that!
Returning to audio, I need to re-read HF Olson's books again, and look for those revealing little asides that point to areas of further research that were never undertaken. The whole experience of digging up Western Electric's Harmonic Balancer was a shock - here's a circuit that is as important as negative feedback, by the people that invented negative feedback, that was lost to all of the literature after the Thirties. Gone. Forgotten. Invented by the most advanced electronics lab in the world, and still forgotten by the time of the Williamson in 1948.
So there's a lot of stuff to dig up, and why I most sincerely hope the work of BudP, Mamboni, and Moray is developed further, or at the absolute minimum, is widely published. Audio is filled with brilliant work that is forgotten for reasons that have nothing to do with technical merit.
It does make you think how much was lost when religious fanatics burned the Library of Alexandria, which contained all the knowledge of the classical world. What we have now are only scraps and scattered fragments, badly copied by a handful of medieval monks. We know they had batteries - what did they use them for? We know they had mechanical clocks - what else did they have? The emotional and spiritual center of classical Greek civilization were the Mysteries of Eleuisis - and we know almost nothing of a religious ceremony that was in use for a thousand years.
Huh. The admin has disabled private messaging, so why don't you visit Nutshell Hi-Fi and scroll down past the News section. You'll see the contact information there. Look forward to the message!