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chaos.squirrel 20th December 2006 01:43 AM

[Newbie] PA speaker impedance problems
Hey there.
I'm new to the forum, and reasonably new to the world of putting together pa systems.

here's my problem:

I've got some PA Horns, of the type you would expect to see on a (big)Loudhailer/Megaphone/PA Van type thing (I know that's a really vague description, but most of the labels on them have worn off and I'm not that good at identifying speaker shapes etc.)

the Impedance rating on them is 200 Ohm, I can't remember the other specs on them, and don't have them on me right now...

I plugged them into a cheap stereo amp with a 4 - 8 Ohm output Imp (that I wasn't worried about blowing up) and all that came out was really quiet, distorted sound, which was more or less what I expected.

Is there any way of running them off a 4/8/16 Ohm amp?
(they don't have to sound particularly good, just clear enough to be used for talking through...)

Is that a silly question? if it is: sorry.

thanks in advance


imix500 20th December 2006 02:29 AM

Hi, sounds like they are meant to be run on a 70 volt system. Get a matching transformer with enough power handling and you should be fine.

Burnedfingers 20th December 2006 02:46 AM

It sounds like they already have a 70 volt transformer on them with a tap of 25 watts.

imix500 20th December 2006 03:16 AM

Yes, Indeed.

chrispenycate 20th December 2006 10:47 AM

But I bet they're not 200? speakers. They'll have a step-down transformer mounted in them, and if you don't need long cable runs, you can bypass the transformer and commect straight to the driver (though a series capacitor might be a good idea; most of them are seriously unhappy about low frequencies)
Of course, you've got to identify the transformer, and analyse its connections, first.

Burnedfingers 20th December 2006 11:17 AM


Is there any way of running them off a 4/8/16 Ohm amp?
To answer your question... If the speaker has a 70 volt transformer on it. 1.) Get a output transformer or autoformer and hook to output of your amplifier. 2.) Remove the 70 volt transformer on the speaker/horn and hook directly up to the amplifier.

chaos.squirrel 22nd December 2006 07:55 AM

thanks everyone,

I'll do some more research on 70V systems and figure this out.
thanks again


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