Right way to set gains on LOC?

Is there a right way to set the gains on my new Line Output Converter (LOC)?  I would like to use a DMM if at all possible and prior to adjusting the gains on my amp, correct?

I don't know if there's a right way or not because it seems that the manufacturers of line output converters keep that info to themselves, or at their most generous are very vague about how to do it.  I used two different brands of LOC's on my sedan install and this is how I set their gains:

I used the same test tone CD that I had prepared for amp gain-setting.  Prepared the system just the same way as if I were going to set amp gain - amp gains to the minimum position and speakers unhooked.  I read the instruction manuals for the amps for how many volts they would take...one was a max of 6 and the other indicated it would take up to 4 volts.  Set the CD on a test tone for the bass amp and LOC and adjusted the deck to maximum clean output (on mine it was about 2/3 of the dial).  Connected the meter to the amp speaker outputs and set it for AC volts.  Adjusted the gains on the LOC until it read 6 volts across the amp output terminals.

For the other amp I played a higher tone and set the voltage at the amp output at as close to 4 volts as I could get, but it wouldn't go there.  I don't know if it was a matter of two types of LOC's or what, but later after listening i tweaked those LOC gains back down a bit and the sound became much improved.

My gut feeling is that it might just be a waste of time using a meter to set LOC gains.  The idea, as I understand it, is to adjust the gains until you achieve maximum signal input which would be maximum voltage input from the deck.  I believe that if you have the amp gains all the way down and the speakers connected you will be able to clearly hear where the test tone stops getting louder.  That would be the maximum input.  The deck will be at maximum clean, but with the amp gain at minimum, the sound will be soft enough that you won't be breaking voice coils and eardrums while doing it.

Then, use the meter when setting gains on the amps if you wish, but of course with the speakers disconnected.

The final tweaking of the LOC should come, though, after extended listening sessions...and this makes it tough for an installer to tweak LOCs in one install session.  I've found, in one case I noted above, that a slight downward tweak of one of my LOC's gains improved the sound noticeably.  You should consider this type of tweaking by ear later - after all is set up.  But if you tweak an LOC gain up, you will have to reset amp gains.

Thank you for the reply... so to get this straight, you take your multimeter and read AC voltage across 1 channel of +/- of the SPEAKERS?  Or one bridged channel? 

I have a 4channel--a pair of front speakers and a subwoofer (which is bridged).

Also, i have a 4-channel LOC, and the manual says to set all gains on the LOC the same, is this also correct?