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  Flush mount PA horn for center console

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Author Topic:   Flush mount PA horn for center console
Eagleman posted 06-01-2001 11:12 AM ET (US)   Profile for Eagleman   Send Email to Eagleman  
I'm looking for a flush mount style of PA horn to install in the center of the console of our 22 OUtrage directly behind the forward cooler seat.I'd like to find a quality 20 watt 8 ohmn weather proof speaker that I could use as a PA. Ive looked at a couple that Speco offers but they are either to big (6"x9"x11" deep)or available in the traditional external horn style that doesn't lend itself to a flush mount. I would appreciate some direction. I plan to hook it to my Standard Horizon Spectrum radio that I recently purchased. Thank you
triblet posted 06-01-2001 01:15 PM ET (US)     Profile for triblet  Send Email to triblet     
I have a vague recollection that the Spectrum
takes a 4 ohm PA speaker.

You do want a horn. They are louder than
hi-fi speakers (but sound awful, even to me).

Watch out for compass influence.

And if you come up with a solution, tell us.
I've been wracking my brain on this since i
got Spectrum a year ago.

Chuck

triblet posted 06-03-2001 03:37 PM ET (US)     Profile for triblet  Send Email to triblet     
I checked my manual. The Spectrum does take
a 4 ohn PA speaker, not 8.

Chuck

Whaletosh posted 06-04-2001 08:18 AM ET (US)     Profile for Whaletosh    
You can use an 8 Ohm speaker, you just won't get as much power into it as a 4 ohm speaker. Power is (V*V)/impedance, so from a 12 volt supply the maximum power that can be delivered to an 8 ohm load is 1/2 of what can be delivered to a 4 ohm speaker.

Back in the days of tube amps it was absolutely neccesary to match the impedance of the spaker to the rated output. In order to insure that the current throught the plates of the tube was kept controlled the output transformer needed to be properly loaded. That is why tube amps had different taps for different impedance loads.

Modern solid state amps have minimum load, not a maximum. A solid state amp can be used with no load down to the minimum load. The 4 ohm load that is stated in the Spectrum manual is the minumum load; it is also the recommended load so that one gets the maximum power out to the speaker. You could always run two 8 Ohm speakers in parrallel.

Now, as for PA speakers they are the best for projecting voices for long distances. First they are directional. Second they are louder for a given input level. That is due to their horn loading design. Horn loaded speakers provide acoustical gain for the frequency that they are designed to work in. So, in the design range horn loaded speakers provide gain over and above the electrical gain provided by the amplifier in the radio. PA speakers are designed work in the frequency range of voices; outside of that range and the gain is nill and actually becomes negative. Which is why PA speakers sound reasonably good for voices, but crappy for music. PA speakers have a very narrow frequency response; just the opposite of what is needed for good music reproduction.

So the bottom line is, for use a PA (hailer) speaker go ahead and use an 8 ohm unit. Yo won't harm your Spectrum radio.

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