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      03-08-2009, 05:03 PM   #5
Technic
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Drives: 2015 320i
Join Date: Apr 2005
Location: Ft Lauderdale, Florida

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Quote:
Originally Posted by 808MGuy View Post
Even if you're setting line driver gains or DSP input gains instead of amp gains, you still need a baseline input signal to set them with which would be the output of the HU. I assume you'd have the same problem with the premium sound system and the BitOne. You'd have to set a baseline reference level for the BitOne to De-EQ and set its input gains. What did you use as your baseline?
That's different from what you are asking for... the amp gains are irrelevant in setting the bit one input level for calibration/de-EQ when using either the low or high level inputs. In my particular case, once I went thru the bit one calibration set up that was it with my OEM volume. I'm not using the bit one DRC remote nor any Master volume, just the OEM volume. The bit one max output level is 4V, so it matches prefectly the PDX input level just for the front and rear speakers; the underseat subs cannot be set for the full 4V output for the reasons already stated, so I make up that deficiency by increasing the PDX gain of those channels only up to the point that I cannot hear any bass pops/distortion up to my max volume.

Your max volume (because there is no way of measuring that in our OEM systems) is set by you, so it can be higher or lower than mine. In my case I just play certain bass notes or certain heavy bass songs and crank the volume up to a level that I consider enough and then I listen for any pops/distortion. If any pop is heard then I lower the gain until I don't hear it any more. With a processor this can be done in too many ways, output level, EQ or even crossover type and not adjust the gains at all at any volume. So there is no one single correct way of adjusting gains.

Regardless of using a processor/line driver or not, the amp gains are normally adjusted either based on how high you can turn the volume up without distortion (by ear) and then adjusting the gains to just below that distortion threshold or by following the JL Audio more technical process of measuring amp output voltages (page 10, http://mobile.jlaudio.com/pdfs/14997.pdf).

The great thing about the BMW OEM HU/CCC/CIC is that the analog outputs are 5V differential. So it could be possible to just leave the gains at minimum if those outputs are connected directly to an amp that have a max input level in the 4-5V range.