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      06-23-2012, 06:31 AM   #1
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mob17's Avatar
United Kingdom

Drives: E92 335D
Join Date: Mar 2012
Location: East Midlands, UK

iTrader: (5)

Guide to level matching, setting amp gains and calibrating MS-8

this is something that taibanl advised me on so credit goes to him.

if you have an MS-8 and some channels are powered by it and some are amped, the amped channels will be limited by the non amped channels. this is a great work around. there are some instructions that are specific to my set up (e.g gains at 11 o'clock) but generally this can be used by most people:

You will do a prelim calibration of MS-8 with gains at the 11 o clock position. (or whatever position is 2v)

When you calibrate ms-8, and you are playing the MS-8 CD, use the hidden menu to find out what volume level gives the OK OK OK display on MS-8...remember it (my car doesn't have a hidden menu so i just remembered 45 clicks)

Set OEM HU at that volume

Go to Test menu of MS-8 (left,right), select pass-thru mode (recommend that you assign your morels (my front mids) to the same OUTPUT channel as the front INPUTS to MS-8)

use pass through mode to play test tone straight to the XD....set the gains according to the JL manual, using a voltmeter

(Dont do this on the bridged center it for the front channels)...for now leave the center channel gain on minimum.

This will be the MAX gain to which the XD can be set..(i still havent done this as most of the ac voltmeters i have used do not have 1khz in their freq range. once i do it, i will mark this on the amp so i know never to go past this)

MS-8 test menu, select output identification. this is sending unfiltered pink noise through individual channels. i used a db app on my iphone called dB Volume, this has a slow response so is good for measuring. Edit: thanks to Kaigoss. Remember to set amp's LP filter for your underseats to 20-30hz above the ms-8 crossover freq. So if its 200hz then set LP filter to 220-230hz. If you can't do this then set the woofer gains so they are 5db louder than the other speakers

find the quietest driver in your system (prob rears/ms-8 powered channels)
turn DOWN the loudest gain to within a few (0-4) dB of rears.
MATCH the center dB, the front dB, and underseat dB from the driver seat, as closely as you can. (adjust gains on XD) attention to the driver's side SPL, pass side will be a bit softer.

re-run MS-8 calibration at -20 to -25 dB. it can be this high as the amped channels are the same "volume" as the OEM rears. Edit: i have found that the best way for me to get the right calibration volume is to use an SPL app, and after level matching in step 5, adjust the ms-8 vol until the pink noise is 50-55db. Remember the ms-8 volume that gives these readings. This will then give you 5 volumes which you can try.

after final calibration, turn up the gains each by the SAME amount. Edit: This only works if you have only your rears on ms-8 power, as this step will attenuate any ms-8 powered channels. Rears don't bother me too much so its ok for me.

I have used the above method and it sounds brilliant. but i could make it even better by getting more efficient 2 ohm speakers for the rears, so i wont have to turn the gains on the amped channels down that much to match the rears, which in effect means after calibration the gains wont need to be turned up.
E92 335D
422bhp 618ft.lbs
Ohlins R&T with custom Swift rears, diff lock plate, monroe upper shock mounts

Last edited by mob17; 09-13-2012 at 03:00 PM.