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Yesterday I picked these up off of craigslist. Back in the 70's a local audio store (audio mart) sold them in several configurations (altec,gauss,ess and ev). Mine have 416-8a's and ess amt tweeters. After opening the cabs I see there is no xover just a cap. Is this the best way or just the cheapest? If the cap is the way to go would I benefit by replacing them with newer higher quality caps? They sound very good now.
Nice surprise ! (416 8a's)
I've used both 12uf and 17uf caps (approx. 1.2k - 1.6k crossover freq.) with 1" dome tweeters (1k-20k freq. response) along with 18" B52 transducers. Not ideal but gave some surprising results.
What value caps with the ESS AMT's ?
(new caps shouldn't hurt)
the caps are 22uf 50v. what is the equation for determining the cap value?
It's a logarithm i think, you need a calculator or table to do it easily/quickly unless you're a math/calculus whiz.Quote:
Originally Posted by badtoby
22uF at 8ohms will give you a knee point of about 900hz, with a 6db slope that to me seems kinda low for an AMT, no?
For my purposes, by far the easiest cap formula to remember is the variant promoted by David Weems ( within his series of DIY speaker books ) .
It returns a cap value in milli-Farads ( uF, sometimes written mF ) .
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His formula(e) ;
(A) 159155 / ( Z * F3 ) = C ( your desired cap value )
(B) Another variant , to find the F3 when knowing "C" & "Z" is ;
159155 / ( C * Z ) = F3 point
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C = Cap value, stated in uF
F3 = desired crossover point ( at the 3 db down point ), stated in Hz or cps
Z = the working AC impedance of the circuit , stated in OHMS
<. EarlK
btw, ( for those who are curious ) , "159155" is derived from this ;
[ 1 / (2*Pi ) ] * 1,000,000.00
Thanks Earl even I can understand that ! Now to copy and paste that formula into a doc. that I can pull up quite easily for future ref. ;) :cool:Quote:
Originally Posted by Earl K
Hey we don't have the Thanks link anymore so here goes !
(Altec Best Thanks Earl K for this useful post) :D
thanks for the info, if my math is right that works out to 900hz . 159155/(22*8)=900hz
Oops Guys,
While the formula I presented is correct , there's a serious mistake in my language usage .
- A "uF" ( or a millionth of a Farad ) is not a "milli" .
- A millionth of anything is a "micro" .
- FWIW; the older terminology for "uF" is MFD , ( which became the "open door" for my brain freeze ) .
Quote:
Originally Posted by me
Sorry for the misdirection <> EarlK
I'm sure Mr.(Joseph) Henry would forgive you Earl K. :D
Wasn't millifarad once used, but now fairly obsolete as we express microfarads into the thousands ?
That's OK Earl the "Thank You "still applies ;)Quote:
Originally Posted by Earl K