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Will a DSP fix my volume control? Volume too high at start & too low past halfway

hal

Ready to race!
Location
Bahrain
Found an article describing the voltage measuring method of setting gain: http://knowledge.sonicelectronix.co...-amplifier-gains-using-a-digital-multi-meter/

This is the part I was not quite grasping:



My 4 channel puts out 63 watts x4 @ 4 ohms (per birth cert). 63*4=252 Square root of 252=15.87v And I need to run a sine wave test tone of ~1000hz to see if I reach that voltage. I may just run a sweep and look for the peak.

Reading further on a few other forums, I need to do this test with a load on the amp (speaker and meter connected at the same time). I can check both ways.

I was thinking since the speakers are rated less than the amp delivers then maybe it's better to use the speaker rated power (20w) which would mean around 8.9v? I'm not sure why I calculated it at 12.6v that day, maybe because I combined both channels (40w).

I think the oem speakers are normally very efficient so they should be loud enough with little power. If they're rated at 20w rms I would stick to that instead of setting gain to the maximum the amp outputs. You CAN blow them up by sending more power than they are rated for (but then we are discussing rms and no one knows what the max power rating is so the chance of blowing them up while setting up the gain is more than when actually playing them).

100hz test tone for woofers works well. 1000hz is a bit too high I think. I would really avoid trying to set the tweeters using any test tones (people usually use 5khz but there it's a lot easier to blow tweeters this way).

One thing to note is I believe both oem woofers and tweeters are wired in parallel. So theoretically that means an 8ohm load (if the tweeters are also 4ohm). So maybe around 16v would still be fine (I'm just guessing here).
 

nkresho

suck, squish, bang, blow
Location
Pittsburgh
Car(s)
2022 Q3
OK, got more metrics to support the issue.

I installed the lc7i and a set of focal 165a1 components.

I set my gains using a DMM and ohms law. I needed 15.36vAC on the fronts, and decided on 40w, or 12.65vAC at the rears (still stock)

I ran a 1000hz test tone on a loop to set it all up.

Then, I logged AC voltage at all volume levels.

Here's what I got:

Volume Voltage (AC)
+30------15.3 (100% volume)
+29------15.3
+28------15.3
+27------15.3
+26------15.3
+25------15.3
+24------15.3
+23------15.3
+22------15.3 (3/4 volume)
+21------15.3
+20------15.3 (2/3 volume)
+19------14.6
+18------12.9
+17------11.5
+16------10.2
+15------8.0 (1/2 volume)
+14------6.3
+13------4.9
+12------3.8
+11------3.0
+10------2.0 (1/3 volume)
+9-------1.3
+8-------0.9
+7-------0.5 (1/4 volume)
+6-------0.3
+5-------0.1
+4-------0.0
+3-------0.0
+2-------0.0
+1-------0.0
0--------0.0

So this pretty much confirms my original issue. While I originally stated that above 1/2 it has peaked, it's actually 2/3.

Any setting, over volume 20, adds no additional volume, perceptible or measurable.
 
Last edited:

hal

Ready to race!
Location
Bahrain
It's equally puzzling why from 0 to 4 there is also no change in volume.

Out of curiosity, have you tried to measure the voltage from the headunit itself at the quadlock connector? And then compare that to what the amp receives?

Also perhaps measure the voltage with a 100hz tone.
 

nkresho

suck, squish, bang, blow
Location
Pittsburgh
Car(s)
2022 Q3
I think both issues are due to the sensitivity of my meter. It only goes as low as 1/10th vAC.

0-4 the steps are very audible. It is just too low a voltage to read.

I think the head unit signal might still be too low to read, but I can give it a try.
 
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