Re: Double Coil speakers

VMI <VMI@xxxxxxxxxxx> wrote:
I came across a repair lately (Fame Powerpack 10) where a Speaker has
been used with a double coil, driven by two amps consisting of another
two amps placed in bridge mode.
The amps went and the speaker with them (or visa versa).
The unit is total loss as a new one is allmost the same price as the
spare parts plus repair work.

So I started to look around on the web but couldn't find much.
I'm interested in knowing:
1. Why use a speaker with double coils.

There are basically two times you will see this:

1. For cheap home stereo subwoofers. If the system is using a passive
crossover, you basically use the left-low and right-low outputs from
the crossover to drive the speaker. This is done because it's cheap.

2. Sometimes you will see 8" full-range drivers with dual voice coils
for public safety applications. They will have an emergency PA system
that is electrically isolated from the main building PA system.

2. How to use this speaker (push pull mode - one coil in phase, the
other in opposite phase)

No, both should be in phase. Put them in series or in parallel to
get whatever impedance you want.

3. Can you use only one coil.

Yes, but you get only half the power handling.

4. Manufacturers of these speaker chassis.

Just about every one of the consumer subwoofer outfits in Hong Kong
and Taiwan make this crap. Take a look in the Parts Express catalogue
and you'll see a bunch of them.

Odds are the guy that designed the box you were looking at used the thing
because he got a good deal on it, not for any engineering reason.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
.

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