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Old 10-31-2011, 11:08 AM
DennisCooper!'s Avatar
DennisCooper! DennisCooper! is offline
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Mein Auto: 03 Ex Cop 530d Touring

I think you'd all find the DSP Amplifier is where the 'low level' signals are 'Amplified'. Built into the IC's used, will be the crossover section. In this oem setup, where DSP was optioned when the car was new, the unit that sits in the dashboard does NOT amplify any signals.

So, in order to make aftermarket 4 ohm speakers of which there's hundreds of choices out there work with the OEM DSP amp, you'd need to reverse engineer the DSP amplifier, work out if the crossover occurs before amplification or after that stage, work out how to change the impedance output by perhaps using different IC's etc. You could then work out which frequency band is being outputted upon which wires and the cutoff frequencies used.

I think the DSP option came out in 1997 and it's now late 2011 - in 14 or so years there was extremely little or next to no demand in doing much with E39 audio and especially with wanting to change the DSP amp and then use that to drive better quality speakers. Now that those amplifiers are failing etc there is a small amount of interest in doing things with it. One major stumbling block I see is that the oem DSP amp, also has quite a weedy RMS output level and aftermarket component speakers which are available sound much better when being driven by a much higher RMS output amplifier.

The cost of reverse engineering the DSP amp is hardly worth doing in this respect as I'd expect it to run into 5 figures from the outset.

By far the best solution would be to use a signal summing interface, which takes the outputs from the OEM ampifier and 'sums' them up to a full range, clean and undistorted signal output via RCA's. You can then take those RCA's and if you are so inclined, use an active crossover type audio setup where you can change and try all sorts of crossover frequencies matched to certain speakers and drivers which are known to perform fantastically with sound quality. It'll cost much less, provide a vastly extended quality level to go the signal processor route

If you *must* have oem audio modules, then the only option is the matched set of speakers from BSW which were developed with all the above in mind, which connect as drop in and connected replacements

Cheers, Dennis!
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