Transformers and speakers

COMSYS

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Sep 27, 1998, 3:00:00 AM9/27/98

to

Ok, I know nothing about elctronics. I was wondering if there is a
resource on the web that can tell me about using transformers to step
down the wattage of the speaker signal so that lower wattage speakers
can safely be connected to a higher powered amplifier. I am using a
stereo receiver as a PA, connecting 60 yards of 16 gauge speaker wire,
and a 25 watt/8 ohm PA horn to each channel. The amplifier is rated at
100W/ch. and requires no less than 8 ohm speakers.

Any help with the type of transformer and how to connect it is greatly
appreciated.
-Todd

Ken

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Sep 27, 1998, 3:00:00 AM9/27/98

to tle...@comsysinc.com

You have nothing to worry about. It is safe to use
your 25 watt speakers with a 100w amp as long as
you keep the volume levels down to a reasonble
level. By this I mean as long as you are not hearing
distortion from the speakers they should last for years.

Ken Tyler

Dbowey

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Sep 27, 1998, 3:00:00 AM9/27/98

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There is a "70 volt line" transformer arrangement that does that. The
transformer has taps that permit you to select the amount of drive to the
connected speaker(s), expressed in watts. It permits you to drive some zones
at higher /lower level than speakers in other zones. One source is Radio
Shack. Their 100 W transformer is a special order item, part # RSU 10436475 at
$49.95. For up to 10 W, use part # 32-1031 at $5.99; it's stocked according to
their catalog.

Michael A. Covington

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Sep 27, 1998, 3:00:00 AM9/27/98

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That's only for amplifiers that have a 70-volt output, of course. Otherwise
just use the volume control and don't turn up the volume so high the
speakers rattle.

Dbowey

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Sep 27, 1998, 3:00:00 AM9/27/98

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To get a 70V line arrangement, one has only to use a 100W, 70V line
transformer, reverse connected, tapped at 100W and then distribute the signal
off the 70V line side. No special amplifier is needed.

Ken

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Sep 27, 1998, 3:00:00 AM9/27/98

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Dbowey wrote:

This may be true but I agree with Michael that in this case
driving 25w/8oh pa horns off of a 100w amp it just isn't
necessary. If he keeps the volume knob tuned down and the
speakers are not rattling they should suffer no damage.
You can't say as much for the attending audiance though.

Ken Tyler

Jerry G.

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Sep 27, 1998, 3:00:00 AM9/27/98

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You don't need any transformer. An amp puts out power according to
how high the level is cranked up.

Speaker transformers are for stepping impedance up or down for
speakers, not wattage. You would need one if you wanted to put a 70
volt speaker on an 8 ohm amp for example, or visa-versa. Then the
transformer would require the proper power rating as well. This is
another application altogether...

I would use heavier wire than 16 guage for any speakers... I would
use atleast 12 or 14 to go over 25 feet.

It is distortion in the sound that will realy kill speakers. If you
make the amp so loud that it clips then you will burn the most high
powered speakers because the amp will be putting out some DC component
in the sound...!

--

Jerry Greenberg
http://www.zoom-one.com/electron.htm
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