[R-390] Speaker connections

Mon, 4 Mar 2002 13:23:55 -0800

A 70.2 volt line transformer will act as a 500 ohm-to-voice coil transformer
at 10 watts.  For general purposes, such transformers are suitable for
transforming a 500 ohm audio output to a lower impedance such as with a 4 or
8 or 16 ohm speaker.

Simply, a transformer simply performs conversion, based on the ratio of
primary to secondary turns, from one impedance to another.   Since power is
a combination of voltage and current, you are using the transformer to
convert a ratio of some voltage and current (higher voltage, lower current
at 500 ohms impedance) to another ratio (lower voltage and higher current at
speaker voice-coil impedance) with a minimum loss of power (best match).  In
this case, the 70.2 volt line is the primary of the transformer.  The
primary (or in some transformers, the secondary) may be tapped in a series
of wattage specifications, which is a simple way of setting individual
speaker volume when a number of speakers are connected together in a public
address system.  You, of course, want the loudest setting.

Such transformers can have taps on the primary winding (70.2 volt) or
secondary (speaker voice-coil).  Some have taps on both primary and
secondary.  Many of the transformers have wattage specifications, just
choose the highest wattage terminals.

If you are not sure which terminals to use, connect the R-390 to the "line"
or 70.2 volt terminals, and experiment by testing for which ever terminals
sound best with the speaker you have.  Since more power is needed at low
frequencies, listen for best "lows" and maximum volume from the speaker.

73 de Bill, AB6MT
[email protected]

----- Original Message -----
From: "Mel Williams" <[email protected]>
To: <[email protected]>
Sent: Monday, March 04, 2002 12:26 PM
Subject: [R-390] Speaker connections

> I think I saw an article on one of the R-390 links/lists that showed how
to
> use a 70v line transformer from Radio Shack to connect a speaker to the
> unit. Could someone please direct me to this information  if it does
exist.
> Thanks,   Mel Williams
>
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