Ok....as some of you know I just installed a new alpine9815 headunit....it sounds pretty good but I'd like to have some highs on it. The stereo shop set it up so that my stock amp is still running the stock speakers. The head unit is a high powered 60X4....where is all this power going if the stock amp is running? Can I tap into the HU speaker leads to hook up my tweeters without overloading the deck? Help please! Thank you!

Not a good idea. The factory amp has built-in crossovers for each driver in the system. If you attempt to bypass those crossovers you may fry your tweets. If you can't get the sound you like using all the tone controls and other capabilities of that deck, you may be ready for a full redo on your system.

Jay

When I replaced factory HU in my non-HK '93 325i with an Alpine 7894, the door mids and tweets definitely had much more output - plenty of highs. The HU was connected with speaker outputs going to the factory amp inputs.

After then installing 6x9's in the rear deck, I bypassed the factory amp, running HU power directly to them, while running the front 3-ways through the factory amp with its internal crossovers. There is no obvious front-rear volume difference (fade is centered after adjusting the time delays) at my listening levels.

The benefit to the amp bypass was to eliminate the bass boost to the 6x9's coming from the factory amp.

I may try 3-way passive crossovers for the fronts, and get rid of the amp altogether, if I determine that my front mids are not just over-sized tweeters.

thanks for the replies, what I meant was that I know that Alpine HU is feeding the factory amp with it's speaker leads right? The thing is that the HU has 60x4 worth of power thats not being used. It's only sending a signal to the factory amp just like when using high level inputs for an aftermarket amp. I want to know if I can tap tweeters into the Alpines speaker leads without overloading the deck. I can always hook up a crossover between the tweeter.

Actually it's only 27x4 watts RMS (versus about 15 watts RMS for the factory amp). Nice, but not much difference.

My point about the amp bypass in the rear and no fade bias was that the power difference isn't apparent, at least not with my speaker set.

I don't want to bypass the stock amp, just wanna add tweeters using the decks power, but can I?, since the leads are sending a signal to run the stock amp...

Originally posted by dfrost
Actually it's only 27x4 watts RMS (versus about 15 watts RMS for the factory amp). Nice, but not much difference.

My point about the amp bypass in the rear and no fade bias was that the power difference isn't apparent, at least not with my speaker set.

27 watts RMS may not sound like much compared to the advertised 60 watts (peak). But, it's almost twice the power of the stock amp. The standard rule of thumb is that a doubling of power will give you a 3dB increase in output.

Jay

Originally posted by slickyv
I don't want to bypass the stock amp, just wanna add tweeters using the decks power, but can I?, since the leads are sending a signal to run the stock amp...

I'm not sure, but I'd be leary of trying this. You may present a difficult resistance load to the deck. This could cause problems for the deck. If you want to add additional tweeters, you cound use the deck's preouts and a small amp to power them.

Jay