Stock BOSE Amps: Impedance Matching to 4 Ohm Load
02-26-2009, 09:55 PM
#1
Stock BOSE Amps: Impedance Matching to 4 Ohm Load
Ok, so I got to thinking as I drove into formation today. What are the power ratings, per channel, on the stock BOSE Amps? I want to upgrade the stock speakers, but without gutting everything. If I know the power rating on the stock speakers, why not just do a simple transformer based impedance matching? I mean, it should not really change the load on the amplifier. Find the right ratio of n1/n2 to handle the four ohm aftermarket speaker for the door, and power transfer should remain optimum.
The ONLY negative thing I can see is that the inductance of the transformer might change the overall impedance of the system. Without knowing the magnitude of the amplifier's impedance, I am not sure how this might change frequency response in the time domain. And without all my equipment from ENGR lab, I can't really find out Z, only a DC impedance which would, normally, hide any imaginary component. Bah. Am I over thinking this? Or could this possibly work?
The ONLY negative thing I can see is that the inductance of the transformer might change the overall impedance of the system. Without knowing the magnitude of the amplifier's impedance, I am not sure how this might change frequency response in the time domain. And without all my equipment from ENGR lab, I can't really find out Z, only a DC impedance which would, normally, hide any imaginary component. Bah. Am I over thinking this? Or could this possibly work?
03-05-2009, 06:28 AM
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Bose amp
The bose amp has five outputs. Two drive the rear speakers, which are wired as woofs in parallel with tweeters (caps in series w/ tweeters?). One drives the center speaker. Two drive the fronts. The front tweeters are driven directly by the rear amp, and the front amps use that signal as an input to drive the front woofs. Rube Goldberg would be proud.
With all that having been said, you might do OK replacing the front and rear speakers with component speakers. You might want to check the impedance of the existing speakers with an ohmmeter, just to make sure that they are somewhere in the range of 4 ohms. JL makes nice stuff, but I don't know the sizes that fit in the RX-8.
The bose amp might also have some funny equalization going on to compensate for the bose speakers and/or the vehicle acoustics. Replacing the speakers might create some ugly peaks or valleys in the frequency response.
If anyone has a bose amp setup lying on a bench, I would be interested in characterizing it (gain, input balancing requirements, internal eq pattern, etc.). That might be good for all the folks that are trying to install aftermarket head units, keep alternator whine and hiss down.
With all that having been said, you might do OK replacing the front and rear speakers with component speakers. You might want to check the impedance of the existing speakers with an ohmmeter, just to make sure that they are somewhere in the range of 4 ohms. JL makes nice stuff, but I don't know the sizes that fit in the RX-8.
The bose amp might also have some funny equalization going on to compensate for the bose speakers and/or the vehicle acoustics. Replacing the speakers might create some ugly peaks or valleys in the frequency response.
If anyone has a bose amp setup lying on a bench, I would be interested in characterizing it (gain, input balancing requirements, internal eq pattern, etc.). That might be good for all the folks that are trying to install aftermarket head units, keep alternator whine and hiss down.
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