I was finally reinfected with the "audio bug" I thought I had killed. sigh Luckily my demands for integration and maintaining stock look and feel has helped me justify not upgrading my system. Still, the bug persisted and so did my research, and now it looks like it's more possible than I first imagined...

My first goal in upgrading is to obtain a richer sound in my car, which also includes a sub. My second and almost more important goal is to maintain the stock look and feel of the car. That means stock HU, that means being able to use my steering wheel controls, that means not modifying any speaker mounts or locations. I've pretty much given up all hope of having my volume buttons on my steering wheel work with whatever setup I go with. If anyone can tell me that I can keep them, I will cry for joy.

I went by my local Tweeter (formally NOW Audio Video) knowing full well they would quote me an arm and a leg. Walked out with a $3000 quote but a better understanding of the difficulties that lay ahead. I knew Bose was a bi*#$ but geez. Their solution centered around a JL CleanSweep and a JL Stealthbox install under the trunk floor. Already I've decided to scrap the Stealthbox and go with a 4080 box.

It has been recently discovered (not by me) that our Stock HU (at least the 04 coupe) outputs a flat frequency curve, and that our stupid little Bose amp actually EQs it. So this tells me JL CleanSweep is not necessary, only a quality LOC or an amp that accepts speaker level input.

Right now I'm eyeing the AudioControl LC6 for the LOC and the Audison SRx5 for the amp. The Audison takes speaker level inputs, so that leaves me with a question.

With that all being said, and if you haven't clicked away or fallen asleep or found some place that I am terribly wrong in my logic...

My questions:

1.) Is there a benefit to using a LOC and feeding an amp with the line level RCA rather than using an amp that takes speaker level inputs?

2.) Can I "split" a speaker level input before it gets to the Bose amp, so I could feed a LOC or an amp (or both) to run a sub? This way I could phase in a sub while still using my stock sound system. Ultimately I'd remove the bose amp all together, but this way I could implement my system in stages (aftermarket amp + sub first, then aftermarket speakers later), which also helps the wallet.

3.) I'm fuzzy on the component thing. I realize that amps look for X amount of resistance on an output channel, most cases 2 or 4 ohms. If the front left, for example, "speaker" is really a tweeter and a woofer component set, do I get a tweeter at 2 ohms and a woofer at 2 ohms to load the channel on the amp at 4 ohms? Or is there some more graceful way that this is accomidated? Also, how do I allow the full range of freqs. to the component set, but only highs to tweets and mids to woofer? I think crossovers do this but I don't really understand.

4.) The rear of the car has 4 speakers. Can I run both rear lefts on the same channel and both rear rights on the same channel? Could I treat these the same way as I would treat component sets?

Thanks for the read, any help, and dealing with the newb.

 

1) I haven't tested that myself...

2) Definitely, just keep the Bose amp connected, and splice into the wires coming into it from the head unit. I'm doing that, too.

3) For a 4ohm comp set, it's going to be 4ohm tweeters and 4ohm woofers. It's not a simple series or parallel connection in the crossover - it's a a filter network that allows the comp set to appear as a single speaker to the amplifier. It'll allow only highs to reach the tweeter, and lows to reach the woofer. You can think of it as putting a high pass filter before the tweeter, and a low pass before the woofer, with the same cutoff frequency.

4) In principle, yes, this would work. But it might be better to just do one of the two, b/c the front speakers are more important. I would chose rear deck rather than sides b/c they're farther away and the path length differences from either front seating position are a lot smaller. I think the mounting holes might be deeper, too.

I have the Audiocontrol LC6, too. It does the job... Good luck and don't forget the pics once it's installed

 

You can keep your steering wheel controls with the PAC steering interface. No start crying. :P

 

Not sure if I read it correctly, but adding an amp to the stock system will still allow you to use the steering wheel controls. Just add an LOC before the BOSE amp, and run the amps off that. This way, you will have full use of your steering wheel controls and stock HU. If you went with an aftermarket HU, you can get a PAC unit which will interface with the steering wheel controls. Yeah, the comps are designed to trick the amp into seeing one 4 ohm or one 2 ohm load (depending on the advertised resistance of the comp set). The crossovers take care of the rest (splitting the frequencies). Some do a better job than others. As far as your last question. You can do it, but a couple of things: if you are adding two sets of 4ohm speakers on to one channel, you will be running a 2 ohm load (if wired in parallel). So make sure your amp can handle down to a 2 ohm load. The other thing is you might encounter phasing/lobing issues (which I won't get into detail). The best thing is to focus most of your attention to the front comps, and use one set of rear speakers for FILL ONLY. When you are at a concert, the music comes from the front, not from all around you, and especially not from the rear. Subs don't matter because the frequencies are non-directional, which means that you can't tell where they are coming from; therefore you can put the sub virtually anywhere. My opinion is do an excellent set of comps in the front, and a good set of coaxials in the rear (and NOT 6x9's)--round speakers are the best. If you have a standard 4 channel amp, do a 3:1 gain overlap in the front, and a 2:1 gain overlap in the rear. If you have something like a JL 450/4, the front channels get 150watts each, and the rears only get 75watts (so you can just set BOTH to a 2:1 or 3:1).

 

I'm in a similar situation to amthar. Right now I'm just looking at replacing the front components. On the theory that there are no stupid questions...

When you guys say tap into the speaker wires how is that accomplished? For the front speaks on my 03 the wires are 12 (left front door speaker), 13 (left front tweet), 14 (right front door speaker), 15 (right front tweet). Already I have four wires for a 2 ch amp. Do I "Y" them together to an RCA connector, to line driver, to amp?

Is there a good website for basic audio installs? I know I can save dollars if I do it myself so I'd like to learn. Rather spend the money on good stuff!

 

First in reply to geeman, I don't understand your question. Can you try rephrasing it or explain it a little more? I'd really like to help you, just don't get the question.
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As far as the steering wheel controls go, it is possible that removing the stock Bose amp but keeping the stock Bose HU will render them useless, PAC adapter or no PAC adapter. The theory is that the Bose amp is an "intelligent" amp vs. a "dumb" amp. By that I mean that when you press the "VOL UP" on your HU or on the steering wheel, the HU is not increasing the volume. Instead, it's sending a VOL UP command to the Bose amp, which increases the volume. If you remove this amp you still have the HU outputting a VOL UP command, but nothing there to receive/understand the signal and increase the volume.

Along the same logic, you would probably lose your Bass, Treble and possibly your balance & fade controls on the HU. Because these are being controlled by the amp.

geeman posted this yesterday:

"Intelligent" Amp Theory
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I now understand the component/crossover setup, thanks!

Anyone know a reason that I should run my speaker level inputs into a LOC (like the AudioControl one) vs. an amp with speaker level inputs?

If I'm running a LOC that has an optional remote control for bass gain and I'm running an amp with an optional remove bass gain, which one would I use? I would assume the LOC's output is fixed and I would use the amp's remote gain to adjust bass. Then again I probably shouldn't be adjusting it anyways, just match it and leave it.

I've read that if I want to upgrade my rear deck for fill, I should use 6.5 instead of 6x9 for many reasons, but one of the more interesting reasons is it creates a pathway for bass being produced from a sub in the trunk to make it's way into the cabin of the car, which (at least on the coupe, don't know if this is true for a sedan) is fairly sealed. Anyone with thoughts on this in particular? I already know the theory of round speaker vs. oval and SQ etc etc.

 

LOL...that's funny...and completely wrong. The HU controls the volume. There is a potentiometer in it, and if you look at any of the wiring schematics, you can see this. I have tested the stock HU with an oscilloscope, and the HU doesn't clip until vol 28. The voltage output by the HU is very minimal, because the BOSE amp does the rest of the work. Bass, treble, etc all work afterward. The amp amplifies, nothing more. I agree. I leave the 6x9s empty to allow the bass to travel into the cabin. I find in my sedan that alot more bass flows through when I open the pass-through.

 

As far as your LOC question, it really depends on the amp/HU. The LOC can create a better signal to noise ratio, because it allows the amp to do most of the amplifying of the signal. When you use speaker level inputs, you are already getting an amplified signal that can have more distortion. In the case of the G35, it really shouldn't matter too much because the HU puts out a low voltage signal to begin with, but the LOC can increase the signal strength to allow for a better S/N ratio. As far as the gains on the LOC and the Bass boost on the amp, the bass boost on the amp is usually centered around a certain frequency. If you use it, it will boost that one frequency, but on the LOC, it will boost the entire sub range. Neither the LOC gain nor the bass boost should be substituted for the gains on the actual amp that matches your signal voltage to the amps output.

 

Technically, LOCs are passive devices that have no line amplification function - their function on speaker wires is to REDUCE the amplitude. Their function on preamp wires is usually to block DC or to convert balanced differential to single-ended. Both are usually done passively and result in a loss of signal.

I think you're referring to the line driver section of the LC6 - which is a separate square in the block diagram. Most LOC's don't have a line driver in them.

 

So you're saying that people who say the signal coming out of the HU is flat are wrong? And that a CleanSweep would be necessary?

 

No, not at all. I am saying that is a possibility, but certainly not affecting bass/treble/volume. I wouldn't doubt if the amp does some EQ functions. I don't have an RTA, so I couldn't analyze the signal coming from the HU/amp, however, I wouldn't doubt if it were mostly flat. This might be part of the reason that the signal doesn't clip until vol 28 on my scope. In response to el_duderino: I also agree with you. They are passive devices, however, many offer built in transistors that can increase voltage. David Navone's for instance has this function. It can increase voltage up to 9 volts per channel. But it also regulates excessive voltage from high inputs (not sure about the LC6-never used one). I would love to see an RTA graph coming from our HU, but from what I have heard, there is still EQing that needs to be done after installation of an LOC. I myself haven't EQ'd it. I think it could use some, but for now it is fine for me. I have dropped alot of cash already into my system. And I speak from experience when I say that the HU controls aren't affected. I am using my stock HU now with a LOC tapped BEFORE the Bose amp, and I still have use of the volume and bass/treble/fade/balance/etc.

 

This is as simple as I can put it: how do I physically "tap" into the speaker wire for each side?

For the front speakers there are two wires per side, one for the door speaker and one for the tweeter. On a 2 ch amp you obviously have just two inputs (L/R). How can I run two left wires (door/tweet) into one left input on the new amp. Do I connect them to one RCA plug or am I totally off base?

Sorry this is so basic but that's what I'm envisioning has to happen.

 

My understanding is that the OEM HU sends F and R full-range signals to a multi-channel amp with a built-in electronic crossover filter network. By the time any signals get out of the amp, they've been molested mightily.

I don't know if the tweeters get their own amp channels or not. But let's assume it's a five-channel amp and that the tweeters share a channel with the F door mids. Based on what people have been doing with LOCs on the amp outputs, I suspect that the F door mids get all the highs there are.

The sub channel should be derived from internally mixing the F and R input signals (so that you have a sub signal regardless of fader position).

The F channels have the sub bass filtered out below a certain point

The R channels have the sub bass filtered out below a certain point.

The sub channel has the highs filtered out above a certain point.

There is no channel out of the OEM amp in this configuration that has a full-range signal.

You either need to be OK with the Bose crossover points, or you need to "sum" the signals back together (screwing up your OEM fader function), or...

You need to NOT grab the outputs of the amp, which have been EQ'd and crossover filtered and groped every which way... and instead grab the outputs of the head unit, which are the INPUTS to the amp.

I wrote an article on the BMW X5 audio system that might cover this a bit... has some diagrams too.

http://www.x5world.com/showthread.php?t=3896

 

The Navone unit I have used is the NE-7V (also sold by Soundgate). It says it can have 9V out... but I've cracked this thing open and never seen a transistor in it - just transformers, resistors, caps, and a big stereo pot. Perhaps there's another model of which I'm not aware.

IMO, the EQ'ing "needed" after installation of the LOC depends on the response curve of the LOC and the input impedance of the amp.

You can cause an overall frequency response tilt through connecting a source with an output impedance too far in one direction, with an amp whose input impedance is too far the other direction.

Also, when you take multiple LOC's and "mix" their outputs (like a Front highpass and a sub to get a full-range signal, for example), you get phase cancellation in the stopbands of the crossovers, and the response gets a bit wacky, and in need of eq'ing.

 

Yes, you need to grab the outputs of the HU, not the amp. These are located in the trunk of the vehicle before the amp. When you do this, there are 8 wires...two for each channel. You need to run new speaker wire to the doors. Even on the factory system, the tweeter is run in parallel with the output of the amp (pretty sure on that one...haven't looked at it in a while).