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Old 01-26-2007, 11:30 PM   #5
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Join Date: Sep 2005
Location: Minneapolis/St. Paul, Minnesota, USA
Posts: 3,308
Originally Posted by husker boxster
As always, great information. Thanks.

BTW, I have MY01 with a basic M490 system. I added the rear shelf OEMs a yr ago.

Had I been thinking, I could have answered Q1 myself since I wired the OEMs into the radio and not the amp. Guess I'm excited about actually getting some sound out of this location and my excitment must have "impeded" my brain.

But I have 1 more question. The current setup is parallel. I have not seen any 3.5s with more than 4 ohms. With 2 4 ohm spkrs per side, the parallel formula says I have impedence of 2. The manual says a min of 4 is required. If I do a little snipping and soldering, I get 8 if I turn it into series. I'm assuming that's what I should do, but what are the consequences of leaving it at 2?

I'll hang up and listen to your response.


Part of your issue may be that the existing speakers are not identical. They are a mid-range and a Base speaker. In the wiring of speakers that use passive crossovers the impedance is affected only within the frequencies that the speakers share.

In other words, assume you have a midrange that plays from 150Hz up to 2Khz, and want to add a tweeter that plays from 2.5Khz up to 30Khz, and both are 4 ohm and have crossovers on them that only allow them to play within their ranges, then they will only present a 4 ohm load when wired in parallel, since they do not play within each other's ranges. If you were to then add a second identical midrange with an identical crossover in parallel, the impedance would be 2 Ohms from 150Hz to 2Khz and 4 Ohms from 2.5Khz to 30Khz.

Nominal Impedance is the manufacturer's specification given for the speaker. It is meant to represent the average impedance a speaker presents to an amp. One thing you can do is to wire a resistor into the circuit. Go to a high-end custom stereo shop (or even a Radio Shack) and get the proper resistor to drop the load into the required range. Hope this helps...

Happy Motoring!... Jim'99

Last edited by MNBoxster; 01-26-2007 at 11:33 PM.
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