what exactly do i need to do to set my gains?

[paintballproam 10+ year member]

I have a alpine mrp-650 amp for my two memphis subs wired at 2 ohms. What exactly do i need to do to set the gains for it? I also have a dmm

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[n2audio 5,000+ posts]

You only NEED your ears and a good CD.

But since you have the DMM you might as well do it that way. Get a 50hz tone at realmofexcursion.com. I'd probably go with the -3dB version.

Use V=sqr(p x r) to get your voltage.

 

[paintballproam 10+ year member]

Use V=sqr(p x r) to get your voltage.

what? and what do i do with the voltage reading?

 

[DidUHearThat? 10+ year member]

what? and what do i do with the voltage reading?

Your trying to reach a target voltage. You calculate the target voltage, based on your impedence and RMS, then dial up the gain until you reach that voltage.

 

[dvrmstrng 5,000+ posts]

voltage = the square root of voltage times resistance

 

[GAM3OVR 5,000+ posts]

I have a alpine mrp-650 amp for my two memphis subs wired at 2 ohms. What exactly do i need to do to set the gains for it? I also have a dmm

Use your ears.

Set gains to dead zero. turn volume on HU about 80%

turn gain until you hear distortion, then back off a click and you're good to go.

Simplest and best way to do it

 

[helotaxi 5,000+ posts]

Use your ears.
Set gains to dead zero. turn volume on HU about 80%

turn gain until you hear distortion, then back off a click and you're good to go.

Simplest and best way to do it

Not a terribly reliable way to go on the subs. The amp will clip on subs before you hear it unless you have really good ears and a re using sine wave to set with. At that point you may as well just unhook the subs and hook up the DMM.

And voltage = sqrt (power x impedance)

 

[DidUHearThat? 10+ year member]

Not a terribly reliable way to go on the subs. The amp will clip on subs before you hear it unless you have really good ears and a re using sine wave to set with. At that point you may as well just unhook the subs and hook up the DMM.
And voltage = sqrt (power x impedance)

My math doesn't work out.

So for a 400 watt RMS amp driving a 2 ohm load, I get (400 x 2) sqrt = 1.412 volts?

That sounds too low?

Edit: Okay I figured out I wasn't using my calculator correctly. It's 28.28 volts.

 

[paintballproam 10+ year member]

ok and what about for speakers?

 

[paintballproam 10+ year member]

Your trying to reach a target voltage. You calculate the target voltage, based on your impedence and RMS, then dial up the gain until you reach that voltage.

so my voltage would be what? If im looking for 600rms at 2ohm?

 

[paintballproam 10+ year member]

ok so i need 34v for the subs?

my hu volume goes to 35, so 80% of that is 28, so i turned the volume to 28, with the SUBWOOFER setting on it at +/- 0

on the amp there is a sub db boost or something like that nd that was turned all the way up, so i turned the gain down to NOM which turned out to be like 18v, then i slowly turned it up, while playing the 50hz -3db @ 28volume untill i got it to read 34v.

Now what about the speakers? what test tone do i need to play on them?

my HU is an Alpine 9847, if i were to turn the SUBWOOFER setting up to 15 (max) what would that do?

 

[Twistid 5,000+ posts]

for this chart, do you measure the imp of the speaker leads going into the amp, or just "what they should be"

so for a dual 2 ohm sub, just go ahead and use 1 ohm ? or actually measure the ohm on the speaker wires while the woofer is mounted in the box and everything?

 

[DidUHearThat? 10+ year member]

ok so i need 34v for the subs?my hu volume goes to 35, so 80% of that is 28, so i turned the volume to 28, with the SUBWOOFER setting on it at +/- 0

on the amp there is a sub db boost or something like that nd that was turned all the way up, so i turned the gain down to NOM which turned out to be like 18v, then i slowly turned it up, while playing the 50hz -3db @ 28volume untill i got it to read 34v.

Now what about the speakers? what test tone do i need to play on them?

my HU is an Alpine 9847, if i were to turn the SUBWOOFER setting up to 15 (max) what would that do?

1 khz tone for the main speakers, assuming your running passive. Same refrence level, -3 db at 28 volume. If your running active you would pick tones in the middle ocatve of thier frequency range.

 

[tis10300 10+ year member]

The easiest way to do it is turn your gains on your amp all the way down....turn the volume up on your deck to about 3/4 playing the 50hz test tone....then turn the gain up in your amp until the voltage stops increasing on your dmm.

 

[L7BASSHEAD 10+ year member]

for this chart, do you measure the imp of the speaker leads going into the amp, or just "what they should be"
so for a dual 2 ohm sub, just go ahead and use 1 ohm ? or actually measure the ohm on the speaker wires while the woofer is mounted in the box and everything?

thats what i was wondering???