setting gain and bass boost the right way

i was told to set the sub out to 0. no boost ever. start with the gain very low, 1/4 or so.
set the heads volume to around 75% volume. play a tone or music with bass and slowly turn the gain up till it starts to sound bad then back off the gain a fuzz.

 

o-scope, test tones and a DMM

 

sorry, i have never set one with a dmm. i do it by ear.

 

To figure out what voltage you should set the gains to, multiply the RMS power of the amplifiers output by the impedance of the speaker, then find the square root of that number. If you are using an amplifier that has an RMS rating of more than your speaker(s) can handle/rated for, then use the RMS rating of the speaker (instead of the RMS of the amplifier) to determine the voltage to set your amp to. This is also referred to as gaining down.

Gain Setting Equation
Voltage of the output = sqrt(RMS Power X impedance of the speaker)
Example
Say the amp provides 100WRMS into a 4 ohm speaker:

Voltage = sqrt(100W X 4 ohms)
Voltage = sqrt(400W*ohms)
Voltage = 20V

Again, that was only an example, use the ratings of your amp to figure that out.
Setting the Gain(s)
To set the gain(s), you need two things:
1. A DMM (digital multi-meter) that is capable of measuring AC voltage (needs to be able to measure up to a range of 200V).
2. A test tone CD to use to set the gains at the correct setting.
Now, to set the gain(s):
1. Start the vehicle, and pop the test tone CD in the head unit.
2. DO NOT hook up the sub(s) or speaker(s) to the amplifier while doing this, just leave the outputs unused at this time.
3. Now, time to set up the head unit.
a. If the loudest you listen to your music at on a regular basis is 22/35 with bass @ +3 and treble @ 0 with MX (or any other sound processor) on, use those settings. NEVER turn the headunit above 3/4 of the maximum volume.
b. Remember to have the car turned on.
c. If you want to use bass boost on a sub amp, set it prior to setting the gains on the amp and use the center frequency of the bass boost (45 Hz for most amps) as your test tone.
d. Please remember that if you have a subwoofer volume control on the headunit and/or a bass knob for the amplifier, set it to the maximum before you set the gains on the sub amp.
4. Take the leads from the DMM and but them on the outputs from the amp.
5. Set the gain so that the outputs of the amplifier equal the voltage you found above. This is a MUST.

 

here's a good link. it has a video on it too.

http://www.icixsound.com/vb/showthread.php?t=27819&highlight=Setting+gain