No, I thought I was clear about that in several posts #479 and 487. The plan is to ask those OEMS-who all offer custom engineering services-if they can and will clone the blown diaphragm we can loan them. If yes, and if the engineering and prototyping fees are agreeable to us, we will have them ship the pair of prototypes either to one of us or to Troy Crowe for testing. Troy's fee is ~ $200. CAN. If all of the tests compare perfectly against his measurements on the pair of 6681B drivers he has we can have him ship them to you or another of our members for extensive listening tests. If we love what we hear then we can do either single or a group buy.
That's why Pierre, a 4001 and 6681B user, strongly advised me against using the Athos adapters and to go instead with his own model T2 adapters. https://www.diyaudio.com/community/members/pierrequiroule.9545/
Speaking of exit angles, if you put your finger inside the 2.7” hole of a JA6681B you will notice a sharp edge. You can see this in the Yamaha H-1230 horn as well, between the adapter and the horn. For some reason they thought in the 70’s and 80’s that sharply changing angles would sound great. I am not so convinced.
I have a another suggestion: SB Audience could be interested in making a JA6681B inspired diaphragm for their own driver: SB Audience 65CDN-T, which has already been tested by Joseph Crowe and scored very high, and is affordable. It is quite similar to the JA6681B in its dimensions. And it comes in both ceramic and nD versions. It would be easier, since they already have the molds and tooling. They would need to use paper as voice coil former, similar to full range speakers. And somehow cut out the copper finger suspension (water jet?). Then change to aluminium foil instead of titanium foil when stamping out the domes. Somehow I think that approach is more achievable. Making custom tooling for the JA6681B driver might cost more than we can afford.
At the same time, the magnetic motors in a JA6681B was magnetized 50 years ago. How many have the option (and desire) to send their drivers to some shop for remagnetizing? Not so many, I think.
I have a another suggestion: SB Audience could be interested in making a JA6681B inspired diaphragm for their own driver: SB Audience 65CDN-T, which has already been tested by Joseph Crowe and scored very high, and is affordable. It is quite similar to the JA6681B in its dimensions. And it comes in both ceramic and nD versions. It would be easier, since they already have the molds and tooling. They would need to use paper as voice coil former, similar to full range speakers. And somehow cut out the copper finger suspension (water jet?). Then change to aluminium foil instead of titanium foil when stamping out the domes. Somehow I think that approach is more achievable. Making custom tooling for the JA6681B driver might cost more than we can afford.
At the same time, the magnetic motors in a JA6681B was magnetized 50 years ago. How many have the option (and desire) to send their drivers to some shop for remagnetizing? Not so many, I think.
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BIG thanks for sharing that peculiar and potentially problematic physical aspect of the 6681B's exit angle, especially
since Pierre hasn't made my adapters yet. He's either been long aware of that issue but may have found it to be sonically irrelevant when the drivers are used with his 4001 horns and/or has designed his adapters accordingly to fix any such problem-or this is something he now needs to investigate, measure and run listening tests on himself with existing or modified adapters in his 4001 horns.
Meanwhile, it's heartening to find an experienced 6681B DIYer looking to pursue a feasible and cost-effective plan for cloning these diaphragms. And that it may be far more likely to happen by making the cloned diaphragms also fully compatible with the SB Audience driver, which presumably impressed Troy Crowe equally with its measurements and sound quality.
But while this all sounds very promising, my long and strange DIY speaker journey, does impose certain limits on what I can achieve financially and sonically from Troy services versus on my own. For one thing, while I earned two CET certificates after tech school (long ago), I simply don't have enough math, physics and engineering skills to design crossovers and run most if any of the tests Troy and you often do on drivers and entire speaker systems (though I do expect to get over much of the room correcting software learning curves, at least from help here and/or elsewhere).
OTOH, I'm incredibly fortunate that with lots of Pierre's guidance and Troy selling me that same pair of 6681B (whose magnets are evidently far from demagnetized) and agreeing to finish designing and building my speakers, I am finally within some months of realizing a dream that all manner of hardship had squashed for well over five years.
I was elated when Pierre mentioned that the 4001 horns were designed to be used with my Altec 416-8B midwoofers-and also by his description of the 6681B's sonic qualities, especially as they well coincided with reports from earlier trusted sources.
As these may have to be my first and last DIY speakers, unless the 65CDN-T driver is a perfect fit with Troy's crossover for the Yamahas/Altecs and the tweeter to be selected for above them, my main concern is that the diaphragms be perfect clones of the originals, as that may be essential for insuring that the 6681B's sonic signature remains intact.
I am also indebted to past forum member Gary Dahl, who designed the Altec midwoofers cabinets for his Beyond the Ariel speakers. But Gary seems to have found lasting happiness when switching from the Radian 745NeoBe to the 6681B since early 2018. And given his long professional experience in music I felt very confident in doing likewise. https://www.bremertonwestsoundsymphony.org/gary-dahl-bio
https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-724#post-5138781
https://www.diyaudio.com/community/...impedance-question.318749/page-2#post-5352494
Gary supplied all construction info for Jim Salk to clone the midwoofers boxes for me.
https://www.salksound.com/home.php# SEE attached sketches and a few of over 20 photos.
Certainly, with a system like this (e.g. Huge mods done on Lynn Olson's Amity 300B p-p amps and cloning what was likely Gary Pimm's last known and best SS amp), you could imagine Gary's interest in finally having perfectly cloned 6681B diaphragms which he, Pierre and many others believe could never happen. https://galibierdesign.com/wa-trip-01/
I'm pretty sure that these guys offer remagnetizing for many kinds of vintage drivers, especially since Alnico is known to lose its field strength faster than most other magnets. And their fees ae probably reasonable.
https://greatplainsaudio.com/wp-content/uploads/2016/06/Classic-Series-416-8B-Spec-Sheet.pdf
Most of this seems quite encouraging. Will be in touch with Pierre and Troy about all of the above and a few other matters.
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It would change the sound. Maybe there is something ingenious about using heavy and slow copper with lower resonance (using too big words here). Brass comes to mind, maybe brass fingers would be a good idea. I bet it would sound good with jazz trumpets.
Since this is a DIY forum, I think whoever is interested, but lack the cash to make someone else do it, would learn to make a “tribute” diaphragm themselves.
Since this is a DIY forum, I think whoever is interested, but lack the cash to make someone else do it, would learn to make a “tribute” diaphragm themselves.
I think the copper was necessary to spatter the beryllium onto. Spattering can only be done with a highly conductive target.
Carbon composit could be routed with high rpm fine tip bit into this S-shaped Surround.
Your horns look beautiful. I can't believe you ditched the Raals.
A good ringradiator like Fane ST 5022 with a very light weight membrane is usually better than a 1" compression Driver from about 8k up. Bruce Edgar used the Fane on top of the TAD 4001.
I still got the slot version of the Fane in the basement. Best Ringradiator I ever Heard. Did not hear the Fostex T900 though.
Carbon composit could be routed with high rpm fine tip bit into this S-shaped Surround.
Your horns look beautiful. I can't believe you ditched the Raals.
A good ringradiator like Fane ST 5022 with a very light weight membrane is usually better than a 1" compression Driver from about 8k up. Bruce Edgar used the Fane on top of the TAD 4001.
I still got the slot version of the Fane in the basement. Best Ringradiator I ever Heard. Did not hear the Fostex T900 though.
We really don't know that you until you, me or someone asks SB and at least the other eight or so brands I've listed. Again, if they have the know-how and are able to affordably prototype a true clone our (blown) loaned diaphragm and delivered to our test panel, then any custom tooling costs might likewise be affordable, at least if we can assure the brand of some minimal size run (e.g. 30 pairs). I should be up to making these inquiries in a few weeks.
If you don't ask you don't get.
I got an heretic though. TruExtend. They work with Beryllium anyway, they produce small numbers and the extra hf is exactly what the 6681 needs. The tonal character of the driver would change a bit but a TAD 2001 sounds really good dispite/because of Beryllium.
Only sending in a diaphragm will propably not suffice. The exact curvature of the phase dome has to be determined on the driver.
I can give my 6681 for that purpose.
Only sending in a diaphragm will propably not suffice. The exact curvature of the phase dome has to be determined on the driver.
I can give my 6681 for that purpose.
I found that out the hard way when I got a sliver of an EV DL18MT voicecoil lead wire stuck under the skin of my fingernail. I had ro get antibiotics and a course of chelation treatment to get it out of my system. Be is dangerous stuff, even in smaller alloyed quantities.
WOW! Good thing at least one person thought of this. And thanks for this critically important offer! I hope to start making the rounds among these OEMs next week to pitch our request.
No confusion Here.
If they work with Beryllium they most likely have a spattering chamber. The target can be copper of any shape. You can leave the copper on to have the desired properties like in the case for the surroud, or etch it away like in the case of the Be dome.
There are other ways to manufacture Be but I would be surprised if the domes are not spattered.
If they work with Beryllium they most likely have a spattering chamber. The target can be copper of any shape. You can leave the copper on to have the desired properties like in the case for the surroud, or etch it away like in the case of the Be dome.
There are other ways to manufacture Be but I would be surprised if the domes are not spattered.
Hi radian
Maybe I'm confused! My understanding is that the original Yamaha 6681 diaphragms are alu dome and spring copper suspension.
Were we talking about having replacements made with beryllium domes? That would be cool...
But materion who supply the domes to - ahem - radian, I believe, use foil Be for these. It's TAD who do vacuum deposition as you've described.
Sorry if I've misunderstood the preamble!
Best
CV
Maybe I'm confused! My understanding is that the original Yamaha 6681 diaphragms are alu dome and spring copper suspension.
Were we talking about having replacements made with beryllium domes? That would be cool...
But materion who supply the domes to - ahem - radian, I believe, use foil Be for these. It's TAD who do vacuum deposition as you've described.
Sorry if I've misunderstood the preamble!
Best
CV
Again, WOW! Glad CV reminded us that the original 6681B used AL diaphragms and that this could be critical for cloning the tonality of these drivers! Indeed, compared to Be, this is could very well be why after some years Gary Dahl swapped out his Radian 745 NeoBe drivers for the pair of 6681B he had purchased from PierreQuiRoule to use in his Beyond the Ariel system, and has apparently been happy ever after.
https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-724#post-5138781
https://www.diyaudio.com/community/...impedance-question.318749/page-2#post-5352494
So it certainly seems that the last thing we want to do, especially now that we are apparently gaining more interested members, is to risk second guessing those Yamaha designers and ignoring Gary's comparative experiences. Let's play it safe and do our best to get the diaphragms cloned 100%!
one of the main