The Bose amp is inside the center console.

The inputs from the OE source unit to the amp are balanced full-range, but they do not change with volume, and if you want to retain OE volume and fader controls, you need to use the speaker-level outputs of the Bose amp.

The 3x3 Matrix for this car when retaining the Bose amp is: Speaker-level high-power, Fixed equalization, partial-range with usable crossover frequency (about 80 Hz).

There are front and rear high-pass-filtered output channels, a center channel, a sub channel, and rear D-pillar surround channels.

Here is the electrical signal output of the Bose amp to the F door midwoofers and tweeters, with a pink noise signal (does not change appreciably with volume).



Here is the electrical output of the sub channel:






I don't have a pic of the center channel, but the profile of the bandpass looks like the sub channel , but centered on about 800 Hertz.

I have upgraded the F door high-pass channels and the sub channel. The rears and the D-pillar speakers I have left in place on the Bose amp. The center channel output was powering a modified aftermarket 4" speaker. It only received midrange, so a 2-way speaker is a waste - a simple midrange is fine, but the less efficient the better.


Here is the electrical output to the front doors after de-processing (remember, pink noise is random, so there is a bit of randomness in here which is not averaging out with the settings as they are). I wasn't worried about the LF subsonic filter, as I was using a single 8" as the sub. I could have addressed it if I had a 15" in the back







Verified interface with this vehicle:

I have used the Zapco DC amplifers with BTL attenuator adapters (R and C both removed), so the Zapco DSP-6 could also be used with BTL adapters. The Zapco DC DSP 10-band parametric EQ is well capable of reversing the Bose EQ and of shifting the crossover point slightly (and nudging the subsonic filter slightly if needed). I did not use the Zapco crossover filters - leaving the Bose crossover filters in place and boosting in the stopband a bit was sufficient.

The RF 360.2 has also been used with good results by others, but I can't speak to it.

The HU has an output for every channel out of the amp, and another for PRT (which if I remember correctly was the nav voice/Bluetooth audio signal). If bypassing the amp, you would need to mix in the bt/nav voice (maybe a bitone?) to retain that functionality. I don't know of another way (use the inputs of an MS-8?)

Note:

The crossover "frequency" was an estimation. A two-way crossover filter, such as from a subwoofer to a midwoofer, is actually two filters: a "high-pass" that takes out low notes, and a "low-pass" which takes out high notes.

While it seems that these two filters would always be at matching frequencies, they don't have to be, and many systems use either gapping crossover frequencies or overlapping crossover frequencies.

It is also useful to remember that there is audible output from a speaker past the crossover frequency. The sounds a crossover filter lets pass are called the passband, and the notes it attenuates are called the stopband (a little deceiving, as they aren't stopped cold).

In Pic 1, you can see a peak at 63, so the highpass crossover freq is very low, and could be interpreted to be just a subsonic filter.

In Pic 2, there is a peak at 50, and the strong rolloff starts after 63. (These are odd and surprising xover settings for an OEM system with 6.5" in the door and 8" in the consiole, yes.)

In pic 3, I "moved" the highpass xover point by using the active xover in the amp and setting it to 80. That added additional filtering.

In Pic 4, I "moved" the lowpass by boosting with the amp's EQ in the stop band. Those notes adjacent to the OE crossover frequency were attenuated but not missing, so boosting them with an EQ let me shift the xover point slightly. This would not work for moving the crossover point more than an octave or so, maybe less, but it's a useful technique in the low range, where the difference between 50 and 75 is only half an octave, and so a 24 db/octave crossover filter has still only attenuated the adjacent notes by 12dB tops. It raises the noise level (not engine noise, noise floor - "hiss") slightly in the affected range, but that is inaudible with a subwoofer and causes far fewer problems than a summing module does around the crossover point.

(This also usually requires a parametric EQ. which has user-definable boost-cut center freq, boost/cut in dB, AND "Q", or aspect ratio of the bump/dip you create. When you need a narrow bump, you need a high "Q" setting, and parametrics are invaluable for this and other reasons).