Audio experts, bridging a solid state amp?

[scottmandue]

I work with some industrial/commercial rack mount audio amps, many of them you can flip a switch or add some jumpers to bridge a stereo amp into a mono.

Long story short, my little car has two speakers in the door and no more room to add any other speakers, but the head unit (in dash stereo) has front/back speaker output.

Would connecting the front/back channels together (to increase power output) be more that the little transistor inside the head unit and or the front/back fader circuitry can handle?

IF this could be done (Big if!)

Should it be done in series (positive to speaker, positive/negative from front/back connected, negative to speaker, done per side left/right).

Or parallel (both positives and both negatives connected together to speaker, per side left/right).

I'm pretty sure a wimpy little car stereo could not handle this... however I am wasting two channels of a four channels amp if it could be done.

Thanks in advance.

[rick-l]

I am not an audio expert but to bridge two amplifiers one input has to be the inverse of the other so you can't just hook the two outputs together across the speakers.

[jpk]

As Rick says, it's not quite a simple as wiring things together. There are differences in how the input signal needs to be presented to each amp.

Here's how to wire it; you see that input A gets the 0 phase signal, input B sees that same signal 180 degrees out of phase (inverse signal) That phase reversal is done by the transformer. The problem is that you likely will not have the splitter transformer built into the input stage of the head unit amplifier.



Most external power amps for car audio will have a bridge mode, but it's pretty rare to see it in the head units.

[scottmandue]

Got it... yeah, I figured I might be expecting to much from a inexpensive car head unit.

Thanks for the replies!

[Willem Fick]

A splitter transformer is a very inefficient way of doing this, and a solution using an operational amplifier chip is far better. It is something you can build yourself for very little money from only a few basic electronics components.

Go have a look at this site for a brief overview of how it is done as well as some design and construction help.

[KFC911]

I use the "switch" for bridging my primary home amplifiers to mono (1000 watts each, bi-amped vertically)...for the 911, I bridge the L/R into a single out GHL muffler. I like the results of both.

Hope this helps

[scottmandue]

Just to update, bridging doesn't seem to be the way to go with a cheap little car stereo.

I did find that parts-express sells inexpensive high pass and low pass passive crossovers. So I'm thinking of installing high pass filers on the front channel to the tweeters in the doors and low pass filters on the rear channel to the 6.5" speakers in the doors.