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w00dy 13th October 2004 09:50 PM

componnent crossover question
I have a small 2 seater car and a sony headunit. I have a set of polk dx 5-1/4 components to install in the doors. My sony deck has front and rear stereo outputs. Is it possible to combine the front and rear signals to power these components? I want to get more power to them.
I have thought about trying to bridge the front and rear Left for one side, and front and rear right for the other side, but I don't think headunits can do that, so I'd probably fry something.
I have also thought about taking apart the crossovers and using the high frequency cutoff for the midbasses and connect it to the rear speaker wires (from the headunit) and then use the front speaker lines to power the tweeters (with low frequency cutoff from the crossovers, of course.) My behind the door speakers suck, so I want all of my power to go to the components in the doors.
Is this feasable? anyone tried it? I'm not afraid to solder/de-solder stuff and have some understanding of ac/dc circuits.

maylar 14th October 2004 05:59 PM

No, you can't do that.

Head units are already bridged internally. You can't get any more power combining front and rear channels together.

Separating the tweet/mid won't give you more power either. Each part only works over the frequency it covers. Doesn't matter if they're on separate channels or not.

Buy an amplifier.

w00dy 14th October 2004 08:13 PM

I might be asking the same question: If I disconnect my rear speakers will the fron ones get more power?

Mikett 14th October 2004 08:32 PM

Sorry to disagree with maylar, but you have hit upon an excellent idea and one that is routinely done with 5 channel amplifiers. Furthermore, professional PA setups use the strategy you use.
There are many benefits. Overdriving the midbass will not cause your fragile tweeters to burn out. The harmonic distortion caused by overdriving is less audible when HF rolloff is applied. The tweeters, driven by their dedicated amplifier will provide tremendous headroom and dynamics.
In addition to the above it also allows the trimming of the tweeter level via the fader.
The only issue is that your low end/ bass will be a bit shy. Do consider a subwoofer down the road. Even a single 8" will help tremendously.

About the bridging, your HU outputs are likely already bridged.

SupraGuy 14th October 2004 10:40 PM

The idea that has the most merit (to me) is to separate the woofer and tweeter, however, since the main limiting factor is the amplifier power, any benefit of doing this is of limited use.

The problem is that the amplifier is still receiving, and ampifying a full range signal. Since (typically) head unit amplifiers are bridged already, there is no way to get more power. There's also no way to get to the pre-amp signal and do your crossover there. This is a case where you are far better off getting an outboard amplifier.

All that being said, you can still benefit from doing things that way. Since the amplifiers will see less power dissipation (Resistance climbs in blocked frequencies) they'll run cooler and should produce improved sound. This could be important considering the typical lousy distortion numbers that head unit amps have.

And I still would just leave the rear channels unconnected for myself. :D

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