HiVi M8A former juncture

[check]

How is it joint the former of HiVi M8A to membrane? Could somebody post some photos? I'm interested in making phaseplug to these speakers.

[y8s]

http://www.swanspeaker.com/product/htm/view.asp?id=80

their product page.

are you planning to cut the center of the cone? there is no dust cover, just a smooth cone.

[check]

Yes, cut the cone center.

[Dr.EM]

I bought one recently, but have installed it now. As far as I remembered it is just like the B3N as shown here:

http://www.zaphaudio.com/audio-speaker18-voicecoil.jpg

With the little aluminium bowl. You may see it briefly in this test before I installed it:

http://www.youtube.com/watch?v=xBhDC6fYI6Q

I expect it'll be hard to cut, its metal and feels cold so I expect you'd need a drill to cut it and even then it probably won't look too pretty (and the driver does look very nice as stock ). Good luck anyhow, I might be able to get a photo of it if you really need.

[check]

If you say the former is stretched like on the Zaph's picture, there is no need for aditional photo.
I can't see a think on video .
I hope I will shift membrane distortion higher. In original estate is distortion horrible, break-up peaking very low on frequency scale.

[augerpro]

I think you may just end up trading one evil for another. While the M8a/n breakup is lowish (it is an 8" afterall!) it is totally pistonic until that point. Better than any other 8" I've seen or tested. I'm not even sure that what you propose to do would actually push the resonance UP, being as you will be reducing the structural stiffness of the cone. And even if it did what would it do to the frequency response below now that it may not be as pistonic?

I would lean more towards trying to use some coating to reduce the ring, although I think HiVi already does this with these woofer. Does it have that sticky coating on the backside of the cone? And anyway the cone is only magnifying the distortion, the root of it is the motor and suspension, which is merely adequate on these woofers. You may have to pick your poison, and either accept the higher distortion spikes or crossover the woofer lower to avoid it.

If you do make these changes, try to do some before and after response/impedance/distortion measurements so we can see the results.

[Dr.EM]

Pretty sure theres no coating on the back of the cone if that helps

[check]

Breakup is in region where is distortion caused mainly by membrane. You can compare HiVi M4N and Dayton RS125, you measured, in CSD, HiVi rings like hell. And Hivi has advantage of wide (in comparison to membrane surface) epoxide former juncture to membrane wich helps to damp it, but still...
And if you compare all metal drivers with phaseplug you can see that breakup position responces to length of path which can the wave travel in membrane. With metal dustcup (Seas L16) or in case of Hivi MXx is more than twice as long (roughly compare diameter to radius).
Coating is prepared and so is measuring hardware.

Sorry for my english.