Info on the Yamaha JA-6681 compression driver

[Radian]

Radian, do you know the thickness of the BeCu suspension on the diaphragm for the 6681B?

John

I had to rip the diaphragm appart to measure it. It kind of hurts to do that
but it was broken anyway.
It's 0.16mm on my digital caliper.
Temperature at the time of the measurement was 17 degrees Celsius.
Hope that helps.

Klaus

 

[Radian]

here is a pair available :

PAIR Yamaha JA-6681B Horn Compression Drivers TAD - eBay (item 200470792205 end time May-12-10 15:44:45 PDT)

Thanks Angelo for posting this.
It is really risky to obtain these drivers from someone
you don't know.
"working original diaghragms" does not mean that the
copper beryllium fingers are still all intact as I had to
find out the hard way.

Klaus

 

[jlsem]

I had to rip the diaphragm appart to measure it. It kind of hurts to do that
but it was broken anyway.
It's 0.16mm on my digital caliper.
Temperature at the time of the measurement was 17 degrees Celsius.
Hope that helps.

Klaus

Thanks, Klaus, that's very helpful.

John

 

[tuyen]

Hi guys, just bought a pair of Yamaha 6681b.

Just did a search and found a place that apparently sells 6681 diaphragms.
JBL, ElectroVoice, Jamo, Vifa, Peerless, Infinity horn tweeter diaphragms - Speakerbits

Search for 6681 on that page. Doesn't look like the right diaphargms do they?

Tuyen

 

[bear]

No - those are general purpose replacement type.

_-_-

 

[traskutis]

Hi guys,

I have a pair of Yamaha 6681b and the foam inside the back cover disintegrated.

Could you recommend the replacement foam/felt maybe?

Is the foam function to dampen the back chamber ?

Cheers

 

[bear]

there is usually felt under the foam...

Remove the foam.

Replace or add to the felt with something appropriate and similar... a little thought will likely lead you to the right choice(s) on the material. I think the foam was not so good... but may have had some beneficial effect(s) at the very highest freqs...

_-_-bear

 

[traskutis]

I already removed the foam as it was fooling the voice coil gap. And yes there is a layer of felt.

So any foam will do ?

 

[bear]

I meant I don't like foam, in case I was unclear...

_-_-bear

 

[traskutis]

yamaha ja6681b for sale

I have listed my yamaha ja6681b's for sale if anyone interested:

http://www.diyaudio.com/forums/swap-meet/172996-fs-yamaha-ja6681b-1-4-compression-drivers.html

 

[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

 

[anubisgrau]

what is the difference between meyer sound 1401A and 1401B versions?

also, is meyer driver unsuitable for home use due to a foam damping? is it audibly inferior to yamaha 6681 driver?

 

[anubisgrau]

There's occasionally MEYER SOUND drivers for sale - MS-1401 in A, B or M variables.

Apparently A and B are based upon 6681 and M is entirely different (based on Radian 750).

I'm wondering if MEYER mods make these versions less desirable for home use and if not, what would be the version to go - A or B?

Thanks

 

[triode_al]

Is it really a same unit? I am considering buying a MS1401, and look for the low frequency and soft roll-off of the Yamaha's.

• I understand the diaphragms don't fit because otherwise it would be possible to use a MS1401 diaphr on a Yamaha 6681.

so this just confuses me. Meyer looks more like stage business but I need it in house not in the field.
albert

 

[Radian]

Meyer Sound MS1401a has the exact same diaphragm then the Yamaha
Ja-6618b because it is the very driver and they also purchased the diaphragms
from Yamaha.
Meyer has just put two foam blocks in them and sometimes used a coating.
Both can be removed.

Radian