New Guy

[voice of the theater]

Maybe (one of) these will help?

http://www.altecpro.com/pdfs/vintage...%20Speaker.pdf

http://www.altecpro.com/pdfs/vintage...%20Speaker.pdf

http://www.altecpro.com/pdfs/vintage...%20Speaker.pdf

[Greg_M]

I've got those and all though they have a couple items, they don't have the Thiele/Small info I am looking for.

But thanks for the effort

[voice of the theater]

This should help....

Thiele/Small Parameters for Altec LF Loudspeakers

[Cal Weldon]

This should help....

Thiele/Small Parameters for Altec LF Loudspeakers

No 421A's there. A bit tricky to dig up.

[voice of the theater]

No 421A's there. A bit tricky to dig up.

You're right--they are conspicuously absent.... I'm saving the chart to my hard drive anyways--a nice resource to have....

[Cal Weldon]

Here's what Ron measured his 421A's at:

Re - 4 ohms
Fs - 38 hz
Qms - 4
Qts -.3
Qes - .33
Zmax - 52 ohms
Le - .49 mH
Vas - 8.5 cu ft
Eff - 3.86 %
Sens - 97.8 db/watt/1 m

If yours is an 8 ohm it may be an older version?

[Greg_M]

Here's what Ron measured his 421A's at:

Re - 4 ohms
Fs - 38 hz
Qms - 4
Qts -.3
Qes - .33
Zmax - 52 ohms
Le - .49 mH
Vas - 8.5 cu ft
Eff - 3.86 %
Sens - 97.8 db/watt/1 m

If yours is an 8 ohm it may be an older version?

From the numbers on the basket (etc) I believe it's a 70ish model
Thanks for those numbers

[Old Guy]

Just a couple addendum's I think the 421a was absent since it was discontinued years before the list.

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

If reconed, current parts are closer to the 8hII.

Suggestion? Post to CL to see if there is a neighborhood geek who may be able to measure yours. Some guys would do it just for the fun of it.

[Greg_M]

Just a couple addendum's I think the 421a was absent since it was discontinued years before the list.

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

If reconed, current parts are closer to the 8hII.

Suggestion? Post to CL to see if there is a neighborhood geek who may be able to measure yours. Some guys would do it just for the fun of it.

Thanks for that.
I'll have to call my recone guy and see if he can do it or know someone

[Greg_M]

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