What kind of driver comes with 4 wires?

[Atilla]

I've got this fairly intact subwoofer that I salvaged. It uses two TDA power amps to drive a speaker, which has not two, but 4 wires connected to the coil inside.

What kind of a beast is this and how does one use it?

[chris661]

Likely a dual voice coil subwoofer.

So, you get increased flexibility for wiring. You can use 2 amplifiers (one hooked up to each coil), or play around with wiring configurations (ie, 2x4ohm coils, you can parallel them to 2 ohm, or series them 8 ohm, depending on what you're after).

[AndrewT]

Hi,
it may be a dual voice coil (DVC) speaker.

Measure the DC resistance of both voice coils (VC).
If they both come out at 1r5 then each VC is 2ohm.
If they both come out at 3r0 then each VC is 4ohm.
They are unlikely to come to 6r0 since 8ohm dual VC are, I think, quite rare.

I advise you keep the VC separate and driven by their own power amps.

If you did want to change the drive method, then I would advise running the VCs in series. This will require a much higher power amplifier to obtain the same SPL from the speaker.

I do not recommend paralleling the VCs.

[Atilla]

Since the board is Ok, I think I'll even keep that the way it is (for now).

I wonder if it's using 1chip+coil for left channel signals and one for right? I have to take a closer look at the board.

Thanks you for enlightening me, I hadn't seen one of those before.

[chris661]

If there's 2 amplifier chips, it's likely that's what they're running.

Andrew, perhaps you could explain why not parallel voice coils? I'm more than a little curious. Still, with a pair of (8ohm per coil) DVC subwoofers, some parallel-ing has to occur when using a single amplifier..........

[Pano]

I ran dual 8s in parallel for years. No problem. Dual 4 ohm would be a bit hard on the amp, tho. Better to use one or put them in series.

And yes Atilla, the dual voice coil is often used for a mono mix of the bass signal.

[chris661]

Yeah, I'm using them as 8ohm total. With a cheap stereo amp bridged, using 4 ohms is asking for trouble...

[AndrewT]

As far as my researches can find, all solid state amplifiers perform better into higher impedance loads.
All 2ohm rated amplifiers can drive a 2r0 load and a 4r0 load and an 8r0 load.
Not all 2ohm rated amplifiers can drive a 2ohm reactive load and some make a poor job of driving a 4ohm reactive load.

As I said earlier dual 8ohm drivers are rare.
Most seem to be dual 4ohm and dual 2ohm.
These two options cover speaker loads of 1ohm to 8ohm and meets the desires of most audio reproducers.

Paralleling a dual 4ohm results in a 2ohm load. Very few amplifiers have been designed to drive this load as well as it is capable of driving a 4ohm load. In other words "don't parallel a dual 4ohm VC speaker".
A pair of 2ohm amplifiers could separately drive the two 4ohm VCs and probably do that quite well.

As for paralleling dual 2ohm for a resulting 1ohm load. Leave that to the CAR Audio fanatics that restrict themselves to 13.8Vdc single supply.

[AndrewT]

Originally Posted by chris661

with a pair of (8ohm per coil) DVC subwoofers, some parallel-ing has to occur when using a single amplifier..........

that is wrong.
The operator has the choice of separate driving or paralleling or series coupling.
That's three options to your mandatory, but erroneous, "has to".

[Pano]

Correct!