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Originally Posted by Constantin85
How can i modify the radio unit?
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You need to pick up the audio signal pre-out stage, this has been discussed at length on this and other forums and is pretty straight forward, just do a google search for either "BM54 RCA" or "BM53 RCA"
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I heard that the original nav radio not only lowers the volume, it also cut's off frequencies lower than 40hz at high volume,
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No....
The nav unit does not, I repeat, does not have anything to do with the audio output (from the radio) to the speakers from the cd changer, radio or tape.
The nav unit provides a mono output for nav instruction into the radio ONLY.
The radio module detects when a nav instruction is being made and then switches internally to accept the nav input, it then mixes the nav input with the source output and you hear the nav instruction combined with the source (radio, tape or cd etc).
This is interrupt driven and while you can get a dip in volume (this is adjustable via the set menu BTW), it does not change or modify the freqs that are being passed by the radio module.
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so an audiocontrol lc2i line out converter wouldn't help with it's accubass feature.
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Cant help with this.
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Originally in my harman kardon setup, there is a dedicated wires for subwoofer coming from the radio unit to HK amplifier then from HK amp to factory subwoofers.
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Correct, the HK amp accepts the audio output from the radio module as speaker level (and at full frequency).
It then gets input into the HK amp as front and rear.
The amp then chops up the signals (via filters) and then passes the correct freqs to the correct speakers, keeping the fronts and rears separate (as the fronts carry the phone and nav outputs (from the radio)).
The Sub out is chopped from the rears and amp'd, then passed to the small hk sub amp as mono and at full volume and with lower pass filtering.
The sub amp then uses the speed sensor info to control the volume of the sub in relation to the volume output via the hk amp and radio module.
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I tapped into the wires prior HK amp, took off the factory subwoofers, installed aftermarket amp and sub.
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OK, this should work.
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I was searching for an alternative and tho the Dynavin and it's clone look good, they both have technical issues, specially the sound quality is considerably worse than the original unit.
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Agreed, they are rubbish.
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Other aftermarket units like pioneer have huge advantage over sound quality and i would consider one, but they look much worse than the original when installed in the car.
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Again I agree.
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If i could modify the original nav radio unit to stop it's factory setting of rolling off bass i'd be more than happy.
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I'm not saying you are wrong but, I dont remember this as happing on mine when I ran the speaker level out.
I run the OEM nav, I have a modded bm54 (you have the bm53 in the US), it has upgraded amps and RCA outputs, however I use the RCA outs to run my system.
I use an Intravee and Alpine DSP PXA-100 (ai-net) connected to my rockford fosgate amp, to fully control the audio output from audio source (ipod in my case).
It gives full control over all the speakers and freqs (as you would expect from a DSP), and it also allows full adjustment via the OEM screen.
See here
[E46] Add an Alpine DSP to an e46 and have the OEM DSP menu [pic heavy] - The M3cutters - UK BMW M3 Group Forum
The DSP also allows a Sub to be used and I run the Kenwood stereo sub system, (enabled by the hk button up front).
I run my DSP in parametric mode as I can fine tune it perfectly, I have so much base, I hardly need to power the sub at all.
HTH