Setting gain with multimeter issues

[Jay's ranger]

I just installed a skar audio rp1200.1 amp and a skar svr 12 in a ported box. The sub has an rms of 800 watts at 1 ohm and the amp 1200 rms at 1 ohm. With my head units volume at 90% using a 40 hz test tone Spotify, I am having trouble getting the required voltage of 28.28 according to the formula of square root of rms x ohm. I put the remote base control knob at 1/2 and with the lpf at 100 hz the gain is past 3/4 max to get close to 28.28 volts. Is this normal? Sorry to sound clueless but this is my first sub/amp install and I want it to be right.

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[5t4y_50L0]

Disconnect subs from amp
75% HU volume
Gain at 0 and bass knobs maxed out
HP lowest point to the left
LP maxed out
40 Hz -5 DB or -10 or 0
Turn your gain up till you hit required voltage
Double check the clip light is not out up...
Then set you crossovers accordingly, 40 Hz tuned enclosure would have 80 Hz LP and 30 HP

Some songs will clip but just turn the bass knob down a little. Don't panic if it clips on a specific song, its an indicator not a ticking time bomb, just turn it down.

 

[Jay's ranger]

Disconnect subs from amp
75% HU volume
Gain at 0 and bass knobs maxed out
HP lowest point to the left
LP maxed out
40 Hz -5 DB or -10 or 0
Turn your gain up till you hit required voltage
Double check the clip light is not out up...
Then set you crossovers accordingly, 40 Hz tuned enclosure would have 80 Hz LP and 30 HP

Some songs will clip but just turn the bass knob down a little. Don't panic if it clips on a specific song, its an indicator not a ticking time bomb, just turn it down.

Thank you!!

 

[Jay's ranger]

Disconnect subs from amp
75% HU volume
Gain at 0 and bass knobs maxed out
HP lowest point to the left
LP maxed out
40 Hz -5 DB or -10 or 0
Turn your gain up till you hit required voltage
Double check the clip light is not out up...
Then set you crossovers accordingly, 40 Hz tuned enclosure would have 80 Hz LP and 30 HP

Some songs will clip but just turn the bass knob down a little. Don't panic if it clips on a specific song, its an indicator not a ticking time bomb, just turn it down.

With this the gain ended up a little over 1/2 way, with no clipping light with just shy of 28.15 volts

 

[5t4y_50L0]

Try a zero DB, and understand if the clip lights not on then your in the range of clean signal, especially at 75% volume level. Don't worry about getting exact on the DMM, but only close.

 

[Jay's ranger]

Try a zero DB, and understand if the clip lights not on then your in the range of clean signal, especially at 75% volume level. Don't worry about getting exact on the DMM, but only close.

The test tone I used was 40hz 0db

 

[ThxOne Premium Member]

I'd like to help as well. If you aren't able to get the voltage at the terminals of the amp the input may be too low. Meaning, you may need to turn the head unit up more. Some head units are able to output their max voltage at max volume. Like my Kenwood eXcelons... max voltage at max volume, undistorted. At like 3/4 volume they would output like 2v at the RCA's.

What head unit are you using and how are you running the signal to the sub amp?

 

[Jay's ranger]

I'd like to help as well. If you aren't able to get the voltage at the terminals of the amp the input may be too low. Meaning, you may need to turn the head unit up more. Some head units are able to output their max voltage at max volume. Like my Kenwood eXcelons... max voltage at max volume, undistorted. At like 3/4 volume they would output like 2v at the RCA's.

What head unit are you using and how are you running the signal to the sub amp?

It is an alpine UTE-73BT head unit, running ofc recoil brand rca cables that came in the amp install kit. Pretty sure the head unit has 2v preamp output. So if the pre out voltage is lower than required for the amp , that would explain needing the gain to be turned up more? Would this harm the sub or amp as long as the clipping lite never comes on? As it is currently set I am at 28.15 volts with 75% volume , with the gain up past halfway.

 

[ThxOne Premium Member]

Yeah, I read the specs and I don't see it listing the output voltage of the RCA outs. I did see that you can set the sub level to +15db.

Lower voltage RCA just means yes, turn the gain up more. You are correct. As long as it is not clipping the amp will not be hurt and is designed to have the gain turned up... it's adjustable because not all head units output the same voltage.

Make all EQ's flat.
Disconnect the bass knob from the amp.
Cross it over where you like (80hz) is a good start.
If this were me, I would send a -10db 40hz tone to the amp and set the gain at the output terminals from there.
Lower the head unit volume.
Reconnect the bass knob.

Tell how it hits.

 

[fa5chups]

I'd like to help as well. If you aren't able to get the voltage at the terminals of the amp the input may be too low. Meaning, you may need to turn the head unit up more. Some head units are able to output their max voltage at max volume. Like my Kenwood eXcelons... max voltage at max volume, undistorted. At like 3/4 volume they would output like 2v at the RCA's.

What head unit are you using and how are you running the signal to the sub amp?

ive got a kenwood excelon dmx709s, what should i set my gains at?

 

[ThxOne Premium Member]

ive got a kenwood excelon dmx709s, what should i set my gains at?

Hey I also have that head unit!!! If all your EQ and sound settings are centered and flat, you will get NO DISTORTION from your RCA's at full volume. So crank up the Kenwood then set your gains. Your RCA's are 4v at full volume by the way.

 

[fa5chups]

Hey I also have that head unit!!! If all your EQ and sound settings are centered and flat, you will get NO DISTORTION from your RCA's at full volume. So crank up the Kenwood then set your gains. Your RCA's are 4v at full volume by the way.

Seriously? I’ve messed with my eq since I’m not on a dsp yet, right now it’s tuned for 29/30v vol, in this case should I re try at 35/40 volume

 

[ThxOne Premium Member]

Seriously? I’ve messed with my eq since I’m not on a dsp yet, right now it’s tuned for 29/30v vol, in this case should I re try at 35/40 volume

Flat EQ. No Kenwood enhancements at all. Everything flat. Full tilt at 40. There is NO distortion from the RCA's.

 

[ThxOne Premium Member]

HOLD UP... I was WRONG!!! I forgot, it outputs 5v at volume 40. It is an eXcelon.

 

[chillin 10+ year member]

Gain can also be thought of as a voltage matcher. Your amp just says min and max, but many will have a couple numbers at the min and max. Here's a pic of a Salt 8k. If you're head unit puts out 6v, you would have the gain set at the lowest setting. If the head unit only puts out 0.2v, you'd be able to put the amp at max gain. For most, it's somewhere in-between.