Hello,
Based on my limited knowledge of DIYing gain using TrueRTA, what Krayden/bafukie said sounds right.
I also refer to alot of forums etc that talks about trueRTA.
This was what I did:
Check HU volume before clipping. I use a 1kHz sine wave that was produced at 0dB. (if you only play Front, Rear and Sub)
once you get the volume. don't go higher than that.
Then, connect your amps, then adjust the gain at amp side until you can see the signal clips. then, lower it down a notch.
Here is where there are different 'ideas' about it. Some people say use 0dB, some say use lower than that. When I'm lazy, I just use 0dB. when I rajin abit, I use -3dB. This would allow a little bit of clipping, on your amp's output, but not on HU side. Unless the song you're going to listen to has a higher digital ceiling than 0dB.
Some people also say must add dummy load (resistors).
the first time I did this, I used:
60Hz, 0dB for sub, 1kHz for mid and 4kHz for tweet. I was having problem getting proper sine wave on the tweeter side. It turns out I did not set the setting of the software properly.
2nd Time I did this:
Since the gain of the amp was high (more than 12o'clock), I only turn the volume on my HU very low (turn more then it'll be too loud and uncomfortable). Then, I notice alternator whine... so, I reset the setting. Used max volume of HU before clipping, then turn amp gain until clips, or my ear hurts, which ever comes first. :)
The hardware/software I used was:
Laptop
voltage divider
trueRTA software
test tone disc (frequencies at 0dB and -3dB)
Disclaimer: This is just the way I did it. the 3/4 rule is still the easiest to do (no need fancy device etc). I am still also learning...
Connection from amp
Connection to laptop (voltage divider in between)
No clip, 1kHz at volume 55
Clip, 1kHz at volume 58
