Info on the Yamaha JA-6681 compression driver

Interesting, I think I recall measuring it and seeing ~400Hz.

It may depend on the version of the diaphragm involved, some of the foam and foam + goop may come out at different freqs... the one at ~400Hz works fine down to ~250Hz. Fyi.

The voice range, Bruno66 is usually taken as the "telephone" frequencies at minimum, 300-3,000Hz. Wider is better...

_-_-
 
Can anyone see any merit in using one JA6681 in a 140 HZ horn from say 200Hz to 400Hz and another from 400 up to 12k. I am unsure if the complexity of additional crossover points and source points would out way taking a stress of the driver from doing the critical 200 to 40 HZ range?
I suppose I could try it but it means a fair bit of addition fibreglass work, just when I am almost complete.
 

OK Measuring at the horn mouth is a lot different then measuring at 2-3 meters. Do you have anything at a distance with the yamaha in that horn. I have , 150, 180, 220 and 350 flare mid horns and none of them with many different drivers measure close to the bottom end response at 2-3 meters as they do at the mouth. IE a 220 Hz horn is normally good to 500-600 cycles with a 4" diaphragm driver about double the flare rate or more once you get back to where you really listen.

Bass horns are different they normally go lower further back. :p
 
Bruno, sry, but horns are rather big. My biggest is 1 meter in diameter and it reaches 120Hz using a Fane S 8M.
After that I may say **** off, and stop building horns, but I want to try a labhorn-looking hornsub.
To not have horns under 400Hz will sound strange, I have tried it. It sounds ok, but does not compare to have a proper 1m in diameter x 1 m deep midbass horn with a Fane S 8M.

3GGG, yeah, added clarity in the midbass. But it won't reach 200Hz. But close, like bear said. Using a horn that reaches as low this can sound like a tube, you have been warned. But the rewards outweigh the risks.

Bear, I read somewhere you blew a diaphagm. Did you ever manage to repair that diaphragm? If so, how did you do it?
 
Last edited:
I am planning something similar, because I am a little tired of my from-a-pipe-sounding Goto S-150. I must have it lower than everything else for it to blend in, and it does not work at high volumes. Something is still off, but the Yamahas are doing a good job compensating.
 
Rewind, how high in frequency is the Fane useable in your horn?

Bear, yes, I was. Sorry, I will not do it again.


Anyone: How much is the exit slope of the JA-6681B driver?

I have not decided yet. Between 300 and 450Hz. I will probably never decide. Got to love the minidsp. :)

Just look at the cut trough images for the angles, or do like me - shove a pieve of clay in there. Maybe the throat extension needs to go if one is to be a perfectionist.
 
Last edited:
As I understand from the thread Geddes on wg:s most drivers have an exit angle, and it can vary. If this is true, the Yamaha is not unique at all in that respect. B&C is claimed an exit angle of 6.5 degrees, for example.

Are there any parameters for the driver that can be used in a horn response calculator?
 
If you could measure the length of the throat and the input diameter and the exit diameter you could of course determine the angle with basic geometry.

I can measure the input diameter over the weekend, assuming I remember to do it and nothing else happens to keep me otherwise occupied. Oh, I can likely get the length too. Accurately.

Fwiw the exit diameter is just *under* 35mm on the one I measured and not perfectly round either!
 
Last edited:
not necessarily, the wave exiting the driver is generally considered to be flat/planar. so the simulation may simply take this as a given. the expansion of the horn, assuming it does not represent a deviation from the exiting throat of the driver can be simulated from its entry point. afaik.

better simulation software, commercial & expensive will try to model the exact conditions...
 
department of genieous at wrok...

So, i went and measured quickly a bit earlier...
...umm forgot to measure the depth. Great.

anyhow these are the two measurements I took:

25.54mm
34.70mm

The second is very close to what I measured the last time... it's hard
to hit the very lip of the exit, so it is likely a bit bigger around.

You can measure the depth, it's the distance from the mounting face (without the gasket) to the
front most edge of the pole piece (the silver part between the two black parts on the side of the driver).

Sunday the depth can be had.

_-_-
 
Last edited: