Goodmans Audiom 80 bass speaker and crossover.

[Patrick Turner]

Anyone know what the LC values are for the crossover point at 750Hz
for this ancient speaker?

TIA,

Patrick Turner.

[John Smith]

There were two models of this 15" speaker Patrick a 40 or 60 cps

John
"Patrick Turner" > wrote in message
...
> Anyone know what the LC values are for the crossover point at 750Hz
> for this ancient speaker?
>
> TIA,
>
> Patrick Turner.
>

[Eeyore]

Patrick Turner wrote:

> Anyone know what the LC values are for the crossover point at 750Hz
> for this ancient speaker?

What kind of crossover do you have in mind ?

Graham

[John Smith]

http://homepages.ihug.co.nz/~allofus/tanex/80.jpg


Some info you you Patrick


"Patrick Turner" > wrote in message
...
> Anyone know what the LC values are for the crossover point at 750Hz
> for this ancient speaker?
>
> TIA,
>
> Patrick Turner.
>

[Patrick Turner]

Eeyore wrote:

> Patrick Turner wrote:
>
> > Anyone know what the LC values are for the crossover point at 750Hz
> > for this ancient speaker?
>
> What kind of crossover do you have in mind ?
>
> Graham

The client of mine who is purchasing two 12" modern speakers
in a single box to replace his original Goodmans 15"
already has the crossover which he said had a bass Xover point at
750Hz.
But he sent me the Goodmans booklet from about 1955
which suggests a Xover point at 950Hz, and second order, designed
for 15ohms.

Unfortunately the IDIOTS at Goodmans failed dismally to
provide accurate information about their products in the information
booklet
which contains descriptions but without details of actual sensitivity,
response contours, impedance plots, and crossover circuitry and whether
there
was any attempt to equalise impedance with say 33uF and 15 ohms
strapped across the drive to make sure the terminal load R seen by
the LC filter would be correctly damped without causing ill effect
because of series resonance shunting without proper R load.

I have measured the response of the two Peerless drivers in a large box I
designed
and found it to be as planned below 300Hz and flatter than the Peerless
data
suggests above 300Hz but with a 6dB hump at 2kHz with rapid roll off
after than,
indicating pretty typical modern large woofer response.
This peak should be tamed with the existing LC filter supplied by
Goodmans in 1955, which should have L = 3.6 mH and C = 7.9uF.
Fo would be 944Hz and the 15ohms + 33uF does equalise the
Peerless in series OK.

My non technical client has not a clue what is actually inside the
Goodmans Xover box.

If I supply the speaker terminated with 33uF + 15 ohms the
resulting 15 ohms Z with a dip to 13.6 ohms at 132 Hz should suit the
existing X-over
and give about the right response, and one which will produce more low
bass than
the original Goodmans, although he may have to use more amplifier power
because the Peerless will have less sensitivity than the Goodmans.

Patrick Turner.