New Guy

[GM]

If the 421 is original would suggest using the 8H specs, Same cone but higher temp coil.

Agreed, averaged measured specs of mine and another's pair from way back when, so probably off a bit from a more recent re-cone, especially if not done correctly with a factory kit:

GM [Greg M also on some forums]

[GM]

I think the Xmax is maybe off by a decimal place.
0.05" is a bit under 1/16"

Not really, it's a MI driver designed to euphonically distort and no doubt at least one reason why you liked it so much for guitar picking.............. For HIFI/HT though, this makes it anything but an accurate reproducer unless set up to severely limit excursion. Ditto damping its alum dust cap to limit its beaming/shrill excess HF response.

Then again, IME, prosound musicians tend to prefer more 'colorful' [distorted] home systems, so may be the ideal driver for yours.

GM

[VolvoHeretic]

Ditto damping its alum dust cap to limit its beaming/shrill excess HF response.
GM

They make something called velvet in a spray can, I wonder how that would work for dampening the dust cap? (edit; I was thinking of using it on the insides of my piezo super tweeters.)

http://www.nwepaints.co.uk/acatalog/..._Aerosols.html

[GM]

Don't know, but for sure not as easily removed as rubber cement. WRT piezo damping, I use modeling clay.

GM

[Old Guy]

Count me as anti-recommending the velvet.

I install 4 inch felt domes over my 421's 3 inch aluminum ones. Slight added mass also will lower FS just a hair which is beneficial.

Brad puts a vented paper dome on his to accomplish the same thing. Idea is to kill the overtones from the dome.