Rear speakers

[Tom Burns]

Hi all,

I just picked up a 2001 740 for a winter beater.
I love the car but have a couple of questions:

1-The rear speakers (just the subwoofers or low frequency drivers) are not working. Where do I start to look? I don't think it is the connection, because the mid/highs work, unless there is a separate line for the subs. Is there an amp/x-over somewhere? Where should I start?

2-While I'm not complaining, the "Accept" nag doesn't come on with my nav. How could that be? Maybe the previous owner installed the no nag chip? Could there be another reason? I don't think he would have left the Valentine interface (which defeats the nav) in the car.

Thanks

[libertylover]

There is a separate amp. On my '93 it's in the trunk, either behind the trim panel that separates the trunk/passenger compartments or up under the parcel shelf with the rear speakers-can't remember which.

Don't anything about the Nav. system.

[Tom Burns]

Thanks. I'll have a look for it. Might be the x-over or low end if it's bi-amped.

[NTB]

2001 740s have 1 - 14 channel amp in the trunk behind the CD changer. AMP has all crossover points also, there are multiple connectors for the speakers, but if one of the connectors had rattled loose you would have also lost some of your other speakers seeing they put multiple speakers per connector.


Not sure on where to tell you to start, sounds like the amp is fried.
Cost at dealership will be around $2000.00. And you cannot just add a diff amp for the subs seeing that the input for the stock amp is balanced line 2 channel, the amp handles everything from volume control to crossover points.

If you want to upgrade and replace the amp there is a way, but it is not easy.

http://www.cardomain.com/memberpage/652272/3

There is a place to start.

[Tom Burns]

Originally Posted by NTB

2001 740s have 1 - 14 channel amp in the trunk behind the CD changer. AMP has all crossover points also, there are multiple connectors for the speakers, but if one of the connectors had rattled loose you would have also lost some of your other speakers seeing they put multiple speakers per connector.


Not sure on where to tell you to start, sounds like the amp is fried.
Cost at dealership will be around $2000.00. And you cannot just add a diff amp for the subs seeing that the input for the stock amp is balanced line 2 channel, the amp handles everything from volume control to crossover points.

If you want to upgrade and replace the amp there is a way, but it is not easy.

http://www.cardomain.com/memberpage/652272/3

There is a place to start.

Thanks for the great info. I was hoping for somethig like "the subs have a separate fuse", but it is what it is. Sounds like the amp is really an integrated amp/dsp since it handles all the control functions too.

I'm in the audio/video field (pro gear), so I understand the concepts. If it does take balanced outputs this just means that the signal lines do not share a common ground with anything else. It's simple enought to know (if wired according to industry standards), what the 3 conductors are. With 14 outputs I doubt that they put more than one speaker per connector, unless it is simply to gang a couple of drivers together. Likely there are 7 left channel and 7 right channel inputs for each speaker type. Once I confirm the speaker connections I should be able to isolate the subs (left/right or maybe they are a mono sub). From there I can see if the problem is with the connection, driver, or amp.

If it's the amp it would be quite simple to add a separare amp for the subs. Interfaces will accept line lever or powered inputs. If the output is non-existent than it is also simple enough to split off the signal from the main input and set a relative level which will then be adjusted from the overall gain (which must still be controlled from the head unit). There is probably a control signal from the head unit for all the dsp settings (maybe a DMX type protocol), but I really doubt that moved every single audio control to the amp (of course, I could be wrong).

The only nightmare scenario would be that all signal arrive from the head unit at a fixed level, and all the controlls including volume are located in the amp/dsp. It's possible but highly unlikely that they took all the circuitry out of the head unit. It would be very expensive to make the volume control a digital potentiometer and send all the control signals to the amp. But, maybe they did.

Anyway, I really appreciate your help in giving me an overview and where to start. If you are interested, I will post my findings with, presumably, more detailed technical information.

Thanks for your response.

Cheers

[jcarey]

Originally Posted by Tom Burns

Thanks for the great info. I was hoping for somethig like "the subs have a separate fuse", but it is what it is. Sounds like the amp is really an integrated amp/dsp since it handles all the control functions too.

I'm in the audio/video field (pro gear), so I understand the concepts. If it does take balanced outputs this just means that the signal lines do not share a common ground with anything else. It's simple enought to know (if wired according to industry standards), what the 3 conductors are. With 14 outputs I doubt that they put more than one speaker per connector, unless it is simply to gang a couple of drivers together. Likely there are 7 left channel and 7 right channel inputs for each speaker type. Once I confirm the speaker connections I should be able to isolate the subs (left/right or maybe they are a mono sub). From there I can see if the problem is with the connection, driver, or amp.

If it's the amp it would be quite simple to add a separare amp for the subs. Interfaces will accept line lever or powered inputs. If the output is non-existent than it is also simple enough to split off the signal from the main input and set a relative level which will then be adjusted from the overall gain (which must still be controlled from the head unit). There is probably a control signal from the head unit for all the dsp settings (maybe a DMX type protocol), but I really doubt that moved every single audio control to the amp (of course, I could be wrong).

The only nightmare scenario would be that all signal arrive from the head unit at a fixed level, and all the controlls including volume are located in the amp/dsp. It's possible but highly unlikely that they took all the circuitry out of the head unit. It would be very expensive to make the volume control a digital potentiometer and send all the control signals to the amp. But, maybe they did.

Anyway, I really appreciate your help in giving me an overview and where to start. If you are interested, I will post my findings with, presumably, more detailed technical information.

Thanks for your response.

Cheers

Tom,
There are three connectors on the DSP/AMP mopdule and one of them is for the 4 subs located in the rear shelf. Here is a pinout of the connectors with wire colors so you can troubleshoot these outputs wiht a voltmeter or a spare speaker if you have one.

X18771: 15pin
Pin / Color
1 / Yellow
2 / Blue/Red
3 / YEllow/Violet
4 / White
5 / Blue/Gray
6 / Brown
7 / Blue/Brown
8 / Red/Green
9 / Brown
10 / Blue/Brown
11 / Yellow/Gray
12 / Blue/Violet
13 / Blue
14 / Blue/White
15 / Brown

X18772: 18 pin
1 / Not used
2 / Black/Brown
3 / Not used
4 / Not used
5 / White/Yellow/Gray
6 / Not used
7 / not used
8 / Brown/Orange
9 / Brown/Orange
10 / Not used
11 / Black/White
12 / Not used
13 / White/Brown
14 / Not used
15 / White/Green
16 / Not used
17 / Blue/Red
18 / Yellow/Red

X18773: 26pin
1 / Yellow/Red
2 / Yellow/Brown
3 / Not used
4 / Blue/Brown
5 / Yellow/White
6 / Not used
7 / Not used
8 / Not used
9 / Blue/White
10 / Yellow/Brown
11 / Blue/Black
12 / Blue/Green
13 / Blue/Red
14 / Yellow/Green
15 / Yellow/Brown
16 / Yellow/Gray
17 / Not used
18 / Not used
19 / Yellow/Black
20 / Not used
21 / Not used
22 / Not used
23 / Not used
24 / Blue/Gray
25 / Blue/Brown
26 / Blue/Brown

[NTB]

Originally Posted by Tom Burns

The only nightmare scenario would be that all signal arrive from the head unit at a fixed level, and all the controlls including volume are located in the amp/dsp. It's possible but highly unlikely that they took all the circuitry out of the head unit. It would be very expensive to make the volume control a digital potentiometer and send all the control signals to the amp. But, maybe they did.

Anyway, I really appreciate your help in giving me an overview and where to start. If you are interested, I will post my findings with, presumably, more detailed technical information.

Thanks for your response.

Cheers

WOW nice to be able to talk to someone who knows whats up.

Well to give you the bad news first, the output of the reciever/tuner unit in the trunk is a fixed level to the amp and is only 2 channels. The amp also takes the spif output from the CD changer. Seeing that the amp is on the I-Bus the reciever/tuner can sence what amp is attached from the factory.

The good news is once you remove the amp from the I-Bus the reciever/tuner changes the output to a variable 4 channel, this also removes the DSP option on the nav screen.

The other problem is you will need a cable from the CD changer to the reciever/tuner seeing that you removed the amp and the CD changer cable that went to the amp. I have the part number if you go this route (they ordered 100 from Germany when i was working on my car seeing that there were zero in the states).

Let me know, and good luck.

[NTB]

http://forums.bimmerforums.com/forum...d.php?t=259519

This might be a better forum to get some answers about the sytem in the car.

[Tom Burns]

[quote=jcarey]Tom,
There are three connectors on the DSP/AMP mopdule and one of them is for the 4 subs located in the rear shelf. Here is a pinout of the connectors with wire colors so you can troubleshoot these outputs wiht a voltmeter or a spare speaker if you have one.
<snip>

Absolutely brilliant! Thank you so much. This is exactly what I needed.

Thanks.