BMW E46 10-channel HIFI Amplifier
So I took apart my stock stereo amp. I was amazed
that it's actually a true 10 channel amp. Each speaker in the car is individually
driven by its own amplifier and actively crossed-over. There are no passive
crossovers anywhere.
BMW 8 368 230
UTLOEWE HIGH-POWER
Here is the inside with the cover removed.
The Amp uses five stereo single chip amplifiers. Three of the TDA7375, 2x35W (into 4 Ohms) amplifiers and two of the TDA8563Q, 2x40W (into 2 Ohms) amplifiers.
Front Tweeters - 35 Watts (4 Ohms)
Front Midrange - 35 Watts (4 Ohms)
Front Woofer - 40 Watts (2 Ohms)
Rear Door Midrange - 35 Watts (4 Ohms)
Rear Deck Woofer - 40 Watts (2 Ohms)
After doing a lot of bench testing and reverse
engineering I have figured out most of the amp.
The front channels have a high pass filter at the differential to single ended
input circuit which limits the low end to 23.6 Hz with a -6dB/octave slope.
This is good in a way, it eliminates the low low end which the speakers can't
reproduce anyway which will make it easier on the amplifier chips and lower
overall distortion. The front woofer outputs goes from 23.6 Hz imposed by the
input filter all the way up to 430 Hz. At 430Hz the fall off is -12dB/octave.
For eq'ing the designers added two notch filters on the woofer output channel.
One notch filter is at 190 Hz and the other is at 550 Hz. The 550 Hz notch is
after the 430 Hz low pass filter which makes the roll off even steeper than
-12dB/octave. Next is the mid-range output. It goes from 1.25 kHz to 5.35 kHz
with -12dB/octave slopes on both ends. Notice that the woofer starts rolling
off at 430 Hz, but, the midrange doesn't start coming in until 1.25kHz. There
is a 820 Hz hole in there. Ok, now the tweeters. They start at 6kHz with a -12dB/octave
slope. The components in this filter were not chosen for flat response. For
some reason therefore there is a 0.5 dB bump just above the 6kHz crossover point.
Again there is a hole between the two outputs. Midrange rolls off at 5.25kHz,
but, the tweeter doesn't start until 6kHz. In the plot below I have normallized
the outputs so they appear
Amplifier Connections for 10 speaker system (not HK)
X605 | Description | Wire Size and Color |
5 | Fuse 41 - 30A | 2.5 RT/GN |
38 | RADLV+, Left Front Input+ | 0.75 Yellow/Red |
30 | RADLV-, Left Front Input- | 0.75 Brown/OR |
9 | RADRV+, Right Front Input+ | 0.75 Blue/Red |
17 | RADRV-, Right Front Input- | 0.75 Brown/OR |
37 | RADLH+, Left Rear Input+ | 0.75 Yellow/Black |
29 | RADLH-, Left Rear Input- | 0.75 Brown/OR |
8 | RADRH+, Right Rear Input+ | 0.75 Blue/White |
16 | RADRH- Right Rear Input- | 0.75 Brown/OR |
26 | GROUND | 2.5 Brown |
10 | ANTENNA | 0.5 White |
33 | HLV+, Left Front Tweeter+ | 0.5 Yellow/Red |
34 | HLV-, Left Front Tweeter- | 0.5 Yellow/Brown |
40 | MLV+, Left Front Mid-Range+ | 0.5 White |
39 | MLV-, Left Front Mid-Range- | 0.5 Blue/White |
4 | TLV+, Left Front+ | 1.5 Blue/White |
3 | TLV-, Left Front- | 1.5 Blue/Brown |
31 | MTHL+, Left Mid-Range+ | 0.5 Yellow/Black |
32 | MTHL-, Left Mid-Range- | 0.5 Yellow/Brown |
2 | LH+, Left Rear+ | 1.5 Yellow |
1 | LH-, Left Rear- | 1.5 Brown |
11 | HRV+, Right Front Tweeter+ | 0.5 Blue/Black |
12 | HRV-, Right Front Tweeter- | 0.5 Blue/Brown |
42 | MRV+, Right Front Mid-Range+ | 0.5 Green |
41 | MRV-, Right Front Mid-Range- | 0.5 Blue/Green |
23 | TRV+, Right Front+ | 1.5 Blue/Red |
22 | TRV-, Right Front- | 1.5 Blue/Brown |
13 | MTHR+, Right Mid-Range+ | 0.5 Yellow |
21 | MTHR-, Right Mid-Range- | 0.5 Blue/Yellow |
25 | RH+, Right Rear+ | 1.5 Blue |
24 | RH-, Right Rear- | 1.5 Brown |
HLV and MLV are coming off the amplifier chip to the far left (TDA7375)
TLV and LH are coming off the amplifier chip 2nd from the left (TDA8563Q)
MTHL & MTHR are coming off the amplifier chip in the middle (TDA7375)
RH & TRV are coming off the amplifer chip 2nd from the right (TDA8563Q)
MRV and HRV are coming off the amplifier chip on the far right (TDA7375)