Info on the Yamaha JA-6681 compression driver

[jlsem]

I recently opened up my pair of 6681Bs and found that although they are fairly close in serial number, the diaphragms are slightly different. One has what appears to be latex rubber that has been brushed on around the perimeter and on the leads, the other is plain. My question is: Is this someone's mod or were some Yamaha diaphragms supplied with this coating? Has anyone attempted to remove this coating and is it advisable?





Thanks,
John

[bear]

Meyer Sound did these mods.

In all probability they are inaudible in terms of the difference, imo... why? Because the freqs where the stuff on the diaphragm will have an effect is very very likely substantially above the frequency where most horns will roll off due to the throat geometry and the throat dimension...

...also there is variability in frequency response and sensitivity between drivers with the "same" diaphragm to begin with... so it's probably not much to get worried about.

And, I have measured a fair amount of difference in DCR between various diaphragms... so go figure...

_-_-bear

[jlsem]

I managed to successfully remove the latex from the offending diaphragm. Now I need to make the horn. I use an Apple computer and am unable to make any of the available programs for generating a Le Cleac'h profile work. Anyone out there willing to help me out for a fee?

John

[bear]

suggest you post that request to the Le Cleac'h thread?

what did you do to remove the stuff??


_-_-bear

[jlsem]

I used a Q-Tip dipped in lacquer thinner. Once the layer of latex was broached, I could roll it off with the Q-Tip and a small stiff brush. I didn't attempt to remove it from the leads.

John

[bear]

you are a very brave man with steady hands...

tnx