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After years, my Bose / MiniDSP system stopped working a week ago. No sound from front speakers or subwoofer, though oddly the rear speakers worked so at least I could still listen to news / traffic / weather radio...
I dug around in the wiring with a meter and an oscilloscope and it looks like the MiniDSP "Mini DC Isolator" is not passing a proper "AMP TURN ON" signal. It's REM OUT line only goes to about 8 volts, which is no good- so the bose amp doesn't turn on as it should. **I think** hahaha not 100% sure this is what is happening, but FOR SURE that "REM OUT" line on the MiniDSP Mini DC Isolator board only gets to 8 volts, and I think it should be 12 volts.
The MiniDSP "Mini DC Isolator" is still providing cleaned-up 12 volt DC to my MiniDSP but it's not passing a proper TURN ON (REM OUT) signal.
I could get a new MiniDSP "Mini DC Isolator" but they are no longer available from MiniDSP; maybe I can find one someplace else.
In the meantime, I simply plugged the Bose Harness B41 connector which comes from the head unit directly to the Bose amp's socket instead of running through my DIY harness to the MiniDSP. This works but has no EQ; I am content to listen to this in the meantime. If I can get a new MiniDSP "Mini DC Isolator" (or fix the one I have) then I can just connect it all back through the MiniDSP.
@milosz I appreciate the response and the break down. I am looking to take the Hi-level input signal before Bose amp to my Mosconi DSP. I am wondering if the signal going into the Bose amp is full range and not going through a crossover.
The audio signal from the Head Unit does not go through any crossover, but it does go through the bass and treble controls in the head unit. So it is full range left and right audio, but is affected by the tone controls in the head unit.
I assume the rear Left and Right channels are also the same, as they are just split off the front left and right by the fader.
The 4 ohm speakers that I put in the back sound better than the original Bose speakers do - they are 2-way where the Bose were full range - but I really don't use the back speakers unless a backseat passenger requests it; they're also good for hearing the backup sonar warnings, which only come from the back - which makes sense.
The three speakers in the front doors are wired this way:
10 inch door woofer is powered by a separate amplifier in the rear trunk Bose amp, and is crossed over by a 500 Hz low pass filter -it's an active crossover .
The door mounted 3 inch (or is it 4 inch? I forget) driver is crossed over with a 500 Hz high pass active filter in the bose amp and is driven by another amplifier in the Bose chassis.
The sail mounted polycarbonate tweeter (or is it mylar? but anyway it's not a silk soft dome, which would be smoother sounding) is driven off that same amplifier that runs the 3 inch midrange, but has a capacitor in series which crosses it over at 6 dB per octave above about 4,000 or 5,000 Hz. There is no passive low pass in series with the midrange driver - though there SHOULD be, as it rings pretty badly above about 3,000 Hz and causes some issues by producing some sound in the same range as the tweeter. Some people have made improved midrange-to-tweeter crossovers, as discussed earlier in this thread, and they report good results for the $10~$20 spent.
I don't know what the center speaker is getting driven by - surely an amplifier in the Bose trunk-mounted chassis, and it sounds like it is crossed over around 500 Hz also, though I have not measured it.
I am planning on using DSP for an active 3-way setup in the front replacing all of the speakers bypassing internal front signal using a 6 channel amp and leaving the rear as is for my son when he is in the car. I wouldn't need to worry about all of the nuanced crossed points that the Bose system utilizes. It is interesting that the mid-range speaker is designed to play the same frequency above 3k hz in redundancy with the tweeters without any low pass.
As a test, I would have liked to see how much better the OEM system can sound with a proper active setup tune. I am a firm believer that even a crappy system can sound great with a proper tune.
Out of curiosity, which brand speakers did you replace the rears with? And do they clip at all for lack of RMS power from the Bose amp?
I barely remember what I did with those rear speakers. I got Polk drop-in 2-way units, as I recall.
The front midrange driver isn't "designed" to cover the same range as the tweeter, they just cheaped out and didn't include a low-pass filter for the mid. The output of that midrange driver in the treble overlap with the tweeter is ragged and full of energy-storage crap (i.e., ringing) I also suspect that midrange unit suffers from THD issues as you get above 3 kHz.
I looked into replacing the whole business with aftermarket DSP / crossovers / amplifiers / drivers. It really IS the way to go! But I could not find any midrange driver I liked that could fit in the existing opening in the front doors. Ideally one would want a driver that could comfortably go down to 200~300 Hz and those tend to be larger than the Bose driver in that location.
Also, I wasn't really certain I wanted to replace the low-profile shallow 10-inch woofers in the doors with something else. They really do work pretty well down to 50~60 Hz and there aren't a lot of other 10 inch drivers available that will fit.
For the tweeter there are a good many fine choices, which one would match once the midrange driver was selected.
I like the Focal drivers, but they make no midrange driver that would really fit in the door cutout and I didn't want to go down the road of building or modifying the door cards. There are also a number of fine driver choices from SEAS and Scanspeak, as well as Satori - which are usually used in home speakers. And there are now low distortion drivers from Pruifi that might be interesting to look into.
I used to like the drivers made by MB Quart. In fact I built a pair of home transmission-line speakers based around an old 8-inch three way system that they sold ( pictured below ) which sounds really great except those titanium tweeters are a bit "tizzy" on certain material, if I ever get around to it I will replace them with some soft-dome designs like SEAS or Dayton. I used them in an office I have in my warehouse. Their low end is wonderful - nicely extended and very "un-boxy" sounding. The mids are also clean and warm. But, alas, MB Quart doesn't really make anything anymore that I like.
I went with Audiofrog front stage (1", 2.5", 6"). I am going to have to do some fabrication/modification to make all fit them fit but nothing too hard and I don't think it will be a huge undertaking. I also looked for shallow mount 10" woofers to put in but I was more afraid that they won't be very musical and more for moving air. Granted, I would cross it at 300 hz max and the rest would be the mid-range.
I plan on getting all this together and done this summer. I am piecing all together and about to start sound treatment on the doors first. I'll be sure to share as I go along.
06-01-2024, 08:40 PM
Kaput!
