Hooking up bridged amp with subwoofer and coaxials.

[danford1]

I have a Sony 4 ch amp. Model XM-GTX6040. The rear outputs can be bridged if using a subwoofer. I had them bridged and the sub worked fine. I unhooked the sub and hooked two 6X9 coaxial's on it. Those worked fine.
So I hooked the sub back up to the bridged terminals and everything works fine. L +, R-.
Is this a common hook up? A left and right coaxial and and a single sub all hooked to the same terminals?
The speakers are 4 ohm. The sub is a single voice coil 4 ohm. Would this be like a 3 ohm load on each channel? The amp is supposed to be good for 2 ohms.
It sounds good with no distortion and doesn't seem to get hot but I only ran it 15 minutes or so.
I like the hook up. Getting 5 channels out of a 4 ch amp.
I guess I should mention. I'm only using half of the amp. I'm using this for the rear speakers so the front speaker portion of the amp is empty.

Thanks.
Danford1

[Perry Babin]

The single 4 ohm woofer would be equivalent to having a two ohm load on each channel. The 6x9s reduce the load impedance further.

This is a workable load if you use passive crossovers but it's not practical for the sub because you have to defeat the electronic crossover which reduces the headroom for the bass. Without passive crossovers (when the electronic crossover isn't being used), you get bass in the 6x9s and highs in the sub which typically doesn't sound very good.

If you're not using the front channels, connect the 6x9s to the front channels and leave the woofer on the rear channels.

[danford1]

I would like to do just that (connect front channels for 6x9 and use rear for subs).
Since I am using the speaker level inputs and only have one set of wires running to the amps inputs, can I hook both the front AND rear inputs of the amp together. Can I simply twist the amps front and rear high level input wires together?
That would be wonderful if I could...
Danford1

[Perry Babin]

I can't find anything that gives the input impedance of the speaker level inputs but from other Sony amplifiers, it appears that connecting the speaker level inputs as you described would be safe.

[danford1]

I think I'll just try it and see if the amp goes into protection or works...
Sometimes you just have to experiment and try things :-)

Danford1