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      06-10-2007, 11:44 AM   #16
BavDom's Avatar
Drives: 2006 330i
Join Date: Jun 2006
Location: USA

Posts: 1,262
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I saw this in another thread and thought it might be helpful.

By another member:

I too have listened to both Logic 7 and non-Logic 7 systems, I too think they are both disappointing, and I think the center speaker is terrible. I've installed systems in that car with both great imaging and a wide soundstage with no center. It's a gimmick.

I did a system for a client who bought an E60 2004 with L7 (that system has larger underseat woofers). He hated it, and I listened to it for about an hour after work, and so did I. We did an upgrade in his 2007 E60 for $2K which blew away the L7 - it was identical to the system in my post yesterday in an E90. Zapco DC360, single 10", new F door components.

There have been three levels of audio system in the E90.

One has F and R analog balanced preamp signals from the HU to the BMW amp in the trunk, has no I-Drive, and has no R deck speakers.

One has fiber optic from the HU to the amp, and has rear deck speakers.

On has fiber optic from the HU to the amp and is Logic 7.

Why does this matter? Because the BMW amplifier takes the audio signal, divides it up with crossover filters, and equalizes the crap out of it. If the system uses the fiber optic signal (MOST), there is no analog audio gateway, and you have to use the BMW amplifier as a D-to-A converter, and use the analog outputs of the amplifier as the signal for your new amplifier.

If you can grab an analog signal from the HU, before the amplifier, do so - it's clean and flat and unprocessed, and needs no de-processing, no matter what any shop tells you.

The best way to use that signal? The balanced input of a Zapco amplifier, with an interface harness made for the car. (The BMW HU w/analog outputs used in the E90 and E83 has a current protection circuit - it's best to use 100 ohm series resistors when making such a harness.)

Then you don't NEED the DC amp - although I love the processing in the DC amp - and you don't NEED the LC either.

If you have either of the other two systems, there is no analog signal to use other than the speaker-level signals from the amplifier.

What that shop was talking about doing was taking the outputs of the amplifier and running them into the AudioControl LC, using that to attenuate the signals and merge them back together from low and high-pass signals into a full-range signal, then into the Zapco DC amplifier, and using the DC amplifier's internal processing to reverse the effects of the BMW amplifier's processing.

I do this all the time. I wouldn't use the LC - I don't find the BMW crossover points bad in that system, and the only benefit of the LC is to sum the high-pass and low-pass signals together into a full-range signal - but it works, I guess. I prefer a couple of Zapco BTLs and a signal-sense turn-on generator.

But if you examine the pics in my other post on the E90, you can see that the signal coming out of that amp is wildly processed. It looks like a mountain range. This is taken at the speaker wires. There is a huge boost centered at 1K and fairly wide, and there is a lot of peakiness to the bass.

Now, you may say, well, BMW has processed the sound for the interior of the car. And this is partially true. But my experience tells me that the processing is less for the interior of the car, and more an attempt to neutralize the poor electromechnical tendencies of the low-cost speakers which are used.

The value proposition that Harman Industries and Bose have for the OEMs is this: We will keep your per-car bill-of-materials cost as low as possible - we won't spend a bunch of money on speakers - and we will make them sound better than they really are by processing the snot out of them, which does not add anything to the per-unit cost.

Doesn't sound that good.

In order for a shop to do this interface right, they NEED a real-time 1/3 - octave analyzer with a line-level cable and a PC to run Zapco's software. Then you play a pink-noise test track through the OEM HU, and adjust the amp's output to flat, using the 10-band parametric. If you've never used a parametric, they are incredibly powerful tools.

We do it all the time. I've done Zapco interfaces reversing the OEM processing at the speaker level in the E60, the E90, the Audi C5 A6, the Toyota Prius, and more. I've done Zapco amp installs with no OEM de-processing, but using the OEM HU, on the E83 X3, X5, E46 M3, E46 330ci, E39 530i, Acura TSX, Infiniti G35, Mazda MX-5, Audi A3, S4 (B6), A4 (B7), allroad, and some others.

The thing that I like about Zapco amps is that first of all, they are the only amp maker for cars that I know of who will talk about intermodulation distortion (IM or TIM). Their designs don't abuse overall negative feedback and this reduces IM, which is far more harmful to audio signals than THD.

Secondly, they have trub balanced inputs (what they call Symbilink). I use these all the time, either with OEM balanced line signals, with OEM speaker level signals which work on the balanced input, with zapco's BTL resistor attenuator for higher-wattage OEM amplifier signals, or with their RCA-to-balanced transmitter.

Thirdly, the DSP "card" has a 10-band parametric EQ, digital crossover filtering, and digital time correction per channel. If the installer knows what he is doing and has time in the budget to adjust the system, this can really make a huge difference.
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