fix for low volume from rear speakers when installing aftermarket head unit

[chamilun]

First post. I've never seen this idea anywhere, so thought I'd share.

So I found this out the hard way: when you install an aftermarket head unit (non-Bose), the front speakers are powered from the new head unit. The rear speakers are fed from the pre-amp outs. The stock head unit has 10 volt pre-outs, so if you install something with even 4volt outputs, its still way low.

You can purchase the enfig adapter thats about $99 and will fix the issue.

Or you can do what I did.

The key is purchasing a unit that has a subwoofer line-out and allows the subwoofer level to be controlled and have full range outputs.

I installed a Kenwood DPX-500BT. It has pre-outs for front, rear, and Sub. So, install whole things per usual. Then hookup the rear speakers to the sub out. You'll have to crank the subwoofer almost to max, and keep it at default setting for 'full' range output. Volia. Works good. You do lose fader control, but you can adjust the rears manually using the sub level output.

Hope this helps someone.


As a sidenote, I hooked into fuse 5 which comes on in key pos 2, but not 1. I am yet to find a fuse that is switched to ACC or key position 1. Anyone point me to specifically which fuse is switched to position 1, I'd greatly appreciate. The red wire coming off the speedo cluster...Im not sure which one its switched for.

[walky_talky20]

I don't think the idea of "key position 1" actually exists.

Traditionally, Audi's only really have 3 positions: OFF, RUN, and START. With the middle position being "sloppy". Yes, the blower motor may come on first, then you turn a bit further and the dash lights come on. All of that mess is the same position, at least on my B5. This is in sharp contrast to other manufacturers who have 4 or sometimes 5 positions.

Looking at the wiring diagram for a B6, everything looks the same. There are only the regular, traditional Audi outputs from the ignition switch: 15, 75 and 50. There's a couple other lines for the OFF position and whether the key is physically inserted, but that's pretty much it. The 15 circuit is hot in "RUN" and "START". The 75 circuit is hot in "RUN" only. And the 50 circuit is hot in "START" only.

But maybe I'm wrong. Do you have a definitive, position in between OFF and RUN? And what happens in that position?

[Matt Devo]

The stock head unit has 10 volt pre-outs, so if you install something with even 4volt outputs, its still way low.

you seem to misunderstand the purpose of higher voltage pre-outputs: increased signal/noise ratio - it has nothing to do with the output volume. The stock head units actually have a lower pre-out voltage (<1.5V) than most aftermarket head units, not higher.

[chamilun]

you seem to misunderstand the purpose of higher voltage pre-outputs: increased signal/noise ratio - it has nothing to do with the output volume. The stock head units actually have a lower pre-out voltage (<1.5V) than most aftermarket head units, not higher.

I was not making a statement, only repeating what the guy (michael?) from Enfig puts in his posts.

Regardless, just trying to help the many others who run into this 'problem'

[chamilun]

I don't think the idea of "key position 1" actually exists.

Traditionally, Audi's only really have 3 positions: OFF, RUN, and START. With the middle position being "sloppy". Yes, the blower motor may come on first, then you turn a bit further and the dash lights come on. All of that mess is the same position, at least on my B5. This is in sharp contrast to other manufacturers who have 4 or sometimes 5 positions.

Looking at the wiring diagram for a B6, everything looks the same. There are only the regular, traditional Audi outputs from the ignition switch: 15, 75 and 50. There's a couple other lines for the OFF position and whether the key is physically inserted, but that's pretty much it. The 15 circuit is hot in "RUN" and "START". The 75 circuit is hot in "RUN" only. And the 50 circuit is hot in "START" only.

But maybe I'm wrong. Do you have a definitive, position in between OFF and RUN? And what happens in that position?

position 1 is where you turn off the car, but the key is not in the out, ready to be removed position, and the radio should stay on (in usual setups). Yes, there is a definitive position 1. I'll look and see what is turning on in pos. 1. I know the a/c blower may not turn on until 2, but cant remember

[Matt Devo]

I was not making a statement, only repeating what the guy (michael?) from Enfig puts in his posts.

Regardless, just trying to help the many others who run into this 'problem'

regardless, it's incorrect, and it's a statement when you repeat it without attibution. And your "solution" loses fader control and the use of the dedicated subwoofer output.

The most cost-effective-and-not-completely-shitty fix is to use a high/low adapter on the rear speaker-level outputs of the new head unit and connect that to the rear amp inputs. The real fix is to not use the crappy stock amp at all, but use a decent 4-ch amp for all the speakers.

[chamilun]

regardless, it's incorrect, and it's a statement when you repeat it without attibution. And your "solution" loses fader control and the use of the dedicated subwoofer output.

The most cost-effective-and-not-completely-shitty fix is to use a high/low adapter on the rear speaker-level outputs of the new head unit and connect that to the rear amp inputs. The real fix is to not use the crappy stock amp at all, but use a decent 4-ch amp for all the speakers.

youre a real prick arent u. my post mentions everything you point out. perhaps enfig can defend their statement. Regardless, my solution works. you could also use a line driver on the preout.

just trying to help but instead get another insecure internet troll.,,please tell me youre a teenager.

since youre so intelligent, perhaps you could share which fuse is switched?

[Matt Devo]

First post. I've never seen this idea anywhere, so thought I'd share.

So I found this out the hard way: when you install an aftermarket head unit (non-Bose), the front speakers are powered from the new head unit. The rear speakers are fed from the pre-amp outs. The stock head unit has 10 volt pre-outs, so if you install something with even 4volt outputs, its still way low.

You can purchase the enfig adapter thats about $99 and will fix the issue.

Or you can do what I did.

The key is purchasing a unit that has a subwoofer line-out and allows the subwoofer level to be controlled and have full range outputs.

I installed a Kenwood DPX-500BT. It has pre-outs for front, rear, and Sub. So, install whole things per usual. Then hookup the rear speakers to the sub out. You'll have to crank the subwoofer almost to max, and keep it at default setting for 'full' range output. Volia. Works good. You do lose fader control, but you can adjust the rears manually using the sub level output.

Hope this helps someone.


As a sidenote, I hooked into fuse 5 which comes on in key pos 2, but not 1. I am yet to find a fuse that is switched to ACC or key position 1. Anyone point me to specifically which fuse is switched to position 1, I'd greatly appreciate. The red wire coming off the speedo cluster...Im not sure which one its switched for.

youre a real prick arent u. my post mentions everything you point out. perhaps enfig can defend their statement. Regardless, my solution works. you could also use a line driver on the preout.

just trying to help but instead get another insecure internet troll.,,please tell me youre a teenager.

since youre so intelligent, perhaps you could share which fuse is switched?

I'll let your first post speak for itself. I see none of the info I posted in it - only incorrect, contradictory info.

And I'm not a prick, I just have a thing about people posting factually incorrect information. Call me weird that way. If you don't think correcting posts with demonstrably false information is helpful, that's your opinion, but I'm willing to be it's the minority one.

If I had to guess, you either misunderstood Enfig's explanation, or they were being lazy in explaining it. Either way, most stock Audi head units use 1.5v pre-outs. I went out to my garage, fed my head unit a 1kHz sine wave, and measured the output with a DMM before posting.

The fuses in the panel on the driver knee bolster are either accessory switched or always on, there's no in between.

[walky_talky20]

position 1 is where you turn off the car, but the key is not in the out, ready to be removed position, and the radio should stay on (in usual setups). Yes, there is a definitive position 1. I'll look and see what is turning on in pos. 1. I know the a/c blower may not turn on until 2, but cant remember

Post a video of turning your key. Maybe I'm wrong as I do not own a B6, but I don't think there is actually an "indexed" position in between OFF and RUN. As I explained before, there are a few sets of contacts for the RUN position, so there may be different make/break points in the rotation for different equipment groups. For example, you may be able to turn the key back enough to kill the engine, but keep the headlights on. This is just the slop of those contact sets not making/breaking at the same time. I'm pretty sure you will still only have 1 "indexed" position. By that I mean that if you removed the battery from your car and just turned the key back and forth you wouldn't feel 2 distinct positions. You just feel OFF, RUN and the spring-loaded START position. But feel free to prove me wrong on that.

If there is a particular piece of equipment that turns on/off with the key in a certain way that you like, you could certainly use that to trigger your amplifier or whatever you want to do.

[chamilun]

that seems to be the case: either switched or constant 12v. if i find something ill post back

now on to fixing poor radio reception...

[daverdfw]

I added a Hi-Low adapter, and it fixed my audio in the rear speakers. For like $15

[ultrasport3.0]

Hey Matt -
You seem to have quite a bit more knowledge about the audi audio system. Have a few questions for you along the lines of this thread.
I have a 04 A4 with Symphany II and the Bose speakers. I am installing a Pioneer Avic 8000NEX and some other goodies. But for now going to leave the stock Bose speakers/amp(s)

Bear with me on the prices and details. There is a technical audio/electrical question coming.
I have been told by Christian at Enfig that running the RCA preamp outputs on my new HU will result in alternator whine, popping, poor volume and that I need to add their Enfig RWH-AUD2-HILO http://enfigcarstereo.com/ENFIG_RWH_AUD2_HILO.html for $99 which supposedly takes the RCA preamp outputs and boosts them to the factory 8v (this is what he said. not me).

BUT instead of getting the $89 wiring harness + the $99 'magic box' as they call it. I should get the Enfig SRWH-AUD2-HILO http://enfigcarstereo.com/ENFIG_SRWH_AUD2_HILO.html for $114. This AUD2-HILO 'total solution' he mentions takes the speaker line out and then lowers it to a preamp line level of 8v (again this is what he says).

OKAY>..lol so questions
1) Is is 'better' to us the HU 4v preamp outputs and then add some sort of device to adjust them to match what the Bose amps want. And what is that ... that they want... Do i boost the 4v to 8v as Enfig rep says? Does this mystery product they sell even do that? I know you said it would actually need to be lowered to 1.5v . . . .

2) Is there any reason why it is better to use the speaker line outs and then us a Hi -Lo to convert it to a line-level of xxx volts (what v am i actually after here? 1.5? 4? 8? )

3) These devices sold at Enfig seem to contradict the advice they give about what is being raised or lowered.... are any worth getting or do you feel there is a better option using this new HU and retaking the stock Bose speakers/amps

Thank you and forgive any ignorance in not knowing the technical side of audio installation.

[Matt Devo]

Since you have the Bose setup, all speakers are being driven from the Bose amp, so the low rear/sub issue shouldn't concern you.

I'd install the AVIC without any of the extras (you can always add them later if really needed), and feed the Bose amp the preamp outputs from the AVIC. If you have alternator whine, you can always just ground the HU separately - that's an easy fix. I'm not aware of any issues with aftermarket HUs and the factory Bose setup, but I haven't done any myself; most of the installs I've done have either been with the non-Bose system, or replacing/bypassing the Bose amp.

[KiwiWhirly]

How do I know what speakers I have etc? I have a rear amp. As of.now I have no head unit. Audi a4 b7 2007