[bmwnubie]

I been wanting USB mp3 player for a long time in my car. I have a new Kenwood HU and the metra 70-9003 harness. I know I need an amp with at least 5 channels. I don't have BMW Assist, No bluetooth, No phone, No iDrive.

Can I remove the Logic7 amp and connect the OEM speaker wires to the new 5 channel amp? Is there a harness for that?

I know I need to keep the OEM head unit for software updates, but that can be put in later. Don't want to spend extra money yet...just want the new head unit to work for right now.

[ctuna]

Its a 9 channel amp your replacing
You could use the speaker wiring to run a new amp to
the speakers .
You will have to run the pre out from the head unit to the
trunk.
Helix 82 dsp has 8 channels and dsp.
Sounds like you are aware of the side effects.
Don't think there is a harness you may be able to modify
a Technic harness or maybe he can sell you the amp connector.

https://www.bmwgm5.com/Logic7_E90_91_92_93.htm

http://www.e90post.com/forums/showthread.php?t=138949

[bmwnubie]

Thank you for that, especially the first link.

[bmwnubie]

So, I decided to wire it up without buying an aftermarket amplifier just yet.

I removed the undercarpet in the trunk and see that I been driving with a missing MULF all along. However there are two sets of bundled wires there.

It's very basic indeed. All I have is Logic7, 13 speakers.

I wired up the Kenwood stereo to the factory speakers using the speaker level wires to the OEM speaker wires in the trunk. Got fronts and rear deck speakers working, but no rear door speakers, didn't wire that up.

I used RCA plugs from Kenwood PreOut left and right subs to the OEM Subwoofer wires in the trunk. Had to cut the RCA plug off and wired up the center plug + to Red/White, and outer wire as negative to Brown/Yellow. But I have no subwoofer sound at all. Checked the subwoofer settings in the Kenwood and it is on. Shouldn't it work?

[ctuna]

I think most aftermarket head units only give you
4 amplified channels . Since you are bypassing the amp
You can only run the front doors and floors with one channel
assigned to each . The out signal from the Head Unit for Bass
is likely a preamp level signal and not amplified.
Usually all the rca's have only pre amp signals not amped
signals check your Hu specs.

You have a maximum of 4 speaker location you can amp since
you only have 4 amplified channels.

[6spdcoupe]

Originally Posted by bmwnubie

So, I decided to wire it up without buying an aftermarket amplifier just yet.

I removed the undercarpet in the trunk and see that I been driving with a missing MULF all along. However there are two sets of bundled wires there.

It's very basic indeed. All I have is Logic7, 13 speakers.

I wired up the Kenwood stereo to the factory speakers using the speaker level wires to the OEM speaker wires in the trunk. Got fronts and rear deck speakers working, but no rear door speakers, didn't wire that up.

I used RCA plugs from Kenwood PreOut left and right subs to the OEM Subwoofer wires in the trunk. Had to cut the RCA plug off and wired up the center plug + to Red/White, and outer wire as negative to Brown/Yellow. But I have no subwoofer sound at all. Checked the subwoofer settings in the Kenwood and it is on. Shouldn't it work?

No. The preouts are as they sound- preout (or 'pre-amp') level to an amplifier. There is not adequate power to move really any speaker. You need an amplifier connected to those or rewire rears to the underseats, although the latter would not equate to good results.

[bmw325i]

You should use the connects 2 harness instead. It has the switched 12 volt wire and does steering wheel controls.

I don't have either set of rear speakers installed. My rear channels are used for midbass to the underseat speakers, front for the mids and tweets, and the sub channel for my trunk subs.

Without an amp it won't sound very good since most headunits only put out around 20 watts when you use the high level outputs. I ran a 6 channel rca cable to the trunk and cut off the amp connector from Technics logic 7 harness.

[bmwnubie]

Today I got me the Boss Amp 4 channel R1004. The underseat subwoofers working now. Sounds alot better. However, there is alot of noise. Need better grounding? Or is it from the 9-conductor wire I used? There was some noise before, but now it's louder and stranger after hooking the amp.

[bmw325i]

Originally Posted by bmwnubie

Today I got me the Boss Amp 4 channel R1004. The underseat subwoofers working now. Sounds alot better. However, there is alot of noise. Need better grounding? Or is it from the 9-conductor wire I used? There was some noise before, but now it's louder and stranger after hooking the amp.

What did you use 9 conductor wire for?

Boss amps aren't very high quality. I wouldn't be surprised if the amp is the source of the noise. Make sure the amp is grounded properly and your rca cables are routed away from the power cable. I ran my rca cables on the driver side because the main power wire is on the passenger side of the car.

[ctuna]

Did you use the RCA low level signal to feed it.
The amp that is. You want to avoid speaker out levels
as much as possible with an aftermarket amp..
Did you set the input gain levels or is that possible ?
Also what 325 said about amp quality.
Doesn't look like there is any way to eq the channels
on that amp.
most of the better amps have eq for sets of channels.

[6spdcoupe]

Originally Posted by bmwnubie

Today I got me the Boss Amp 4 channel R1004. The underseat subwoofers working now. Sounds alot better. However, there is alot of noise. Need better grounding? Or is it from the 9-conductor wire I used? There was some noise before, but now it's louder and stranger after hooking the amp.

It is likely something gone wrong with the initial install and now the amp is amplifying it. Although I wouldn't be surprised if the amp is also causing more harm than good.

[6spdcoupe]

Originally Posted by bmw325i

What did you use 9 conductor wire for?

Boss amps aren't very high quality. I wouldn't be surprised if the amp is the source of the noise. Make sure the amp is grounded properly and your rca cables are routed away from the power cable. I ran my rca cables on the driver side because the main power wire is on the passenger side of the car.

Probably ran all of his speaker leads with a 9 conductor- EIA colors and remote turn on in one. Not uncommon really.

You know the whole RCA/power wire needing to be on opposite sides is really a myth though, right ?

[6spdcoupe]

Originally Posted by ctuna

Did you use the RCA low level signal to feed it.
The amp that is. You want to avoid speaker out levels
as much as possible with an aftermarket amp..
Did you set the input gain levels or is that possible ?
Also what 325 said about amp quality.
Doesn't look like there is any way to eq the channels
on that amp.
most of the better amps have eq for sets of channels.

In this case, sure, but otherwise why do you want to avoid speaker level outs ?

Damn, my amps don't have any eq bands ! Hell, nothing but level.

[ctuna]

Yes but you have a DSP 6speed

The common knowledge is speaker level out distort more
and have more noise and why would use and amp to drive
another amp.(unless you had no other reasonable choice.)

[6spdcoupe]

Originally Posted by ctuna

Yes but you have a DSP 6speed

I do, yes. Most commonly though amplifier will not have any eq bands. Closest thing would be a 'bass boost' otherwise just crossovers.

[6spdcoupe]

Originally Posted by ctuna

Yes but you have a DSP 6speed

The common knowledge is speaker level out distort more
and have more noise and why would use and amp to drive
another amp.(unless you had no other reasonable choice.)

Common knowledge is severely flawed. The ONLY difference between 'speaker level' and 'RCA level' is voltage. One may reach clipping a bit earlier but will have a much more robust signal coming from it prior.

Ever see '4V preout' on an aftermarket deck ? It's AC current, just the same as RCA level. Only difference is the amount of it. They're both signal, they're measured in voltage/current.

[ctuna]

The common amps have at least a simple crossover
the mid range ones that most of us use.

Why blow more power before the final stage.

[6spdcoupe]

Originally Posted by ctuna

The commn amps have at least a simple crossover
the midrange ones that most of us use.

Yes, absolutely, a crossover. Not an eq though. There is quite a substantial difference there bud.

[ctuna]

Looks like the r1004 has no crossover
therefore no way to do any crossover setup between
the under seats and doors.
Sorry about the loose definition of crossover and eq.

[6spdcoupe]

Originally Posted by ctuna

Sorry about the loose definition of crossover and eq.

No worries. I know you knew what you meant but others may not.

[bmwnubie]

If I remove the RCA connection from HU to AMP, noise is gone. HU is using the 9-conductor speaker wires. I bought the Ground Isolation (Metra) and it does nothing, noise still there. I moved the amp and removed all loose wires near the amp that don't need to be there in the trunk. After that, noise is reduced. I also removed some paint from the grounding spot. I might have to find a better grounding post to get rid of it totally, or solder (weld) it the ground wire into the car.

ctuna,

I have crossover settings for the subwoofer in the Head Unit. I set to 100Hz.

[ctuna]

do you have a subwoofer I thought you only had
stock speakers and you were running one set of channels
to the doors and the other to the floors.