Well, I must say this...if you have never set your amp gains with a DMM, you should start. The difference in sound is night and day! I dont think I will ever set gains by ear in the future. I was so excited with the outcome that I figured I'd share my experience with the rest of you. It wasnt as straightforward as the write-up in this forum indicates, but it was not much variation from it either. You will see where I had to switch up a little bit as I explain what I did. So...here goes....

First, the reason I wanted to set my gains with a DMM is because with the Infinity 62.11i speakers being pushed by a PBR300x2, they were drowning out the sound of the 4 each TS-D 6x9s that I have in the bags. I mean, it was to the point that if I turned the radio all the way up, the infinitys would be so loud as to where you didnt even know the 6x9s were there. That prompted me to go back into the fairing and adjust the amp. The amp that I have pushing the 6x9s is a JL Audio XD400/4. It doesnt put out a ton of power (only 75 watts rms), but it also doesnt tax the charging system at all and it is a very efficient and cool running amp.

So, after disconnecting the speakers and downloading the test tone, I figured the best way to perform this adjustment was using bluetooth because thats pretty much the only way I listen to my music thru the aftermarket radio. Once I got my bluetooth connection established, I figured I would just touch the amp channel with speaker wires to make sure I was getting sound. BAD IDEA!! That test tone is almost like listening to someone scrape their fingernails along a chalkboard. It is not something you want to push thru to your speakers. Luckily for me, it was just a brief second (literally) to confirm sound. I think if I had left them connected for like 5 seconds or so, I surely wouldve busted a speaker....so dont fool around with that test tone.

Now comes the part where things got different. The only amp I adjusted was the JL for the rears. I didnt touch the PBR because the fronts are right on the edge of distortion at speed and I think that it's gains are set perfectly. When I went to hook up the multimeter to the speaker out on the amp channel one, I was only reading 13 volts. This would explain why the pioneers were getting drowned out by the infinitys. As I am turning the gain adjuster and watching the volts on the DMM, I ended up going all the way to the max and only getting 22 volts, when it should have been 26 (actually 25.8). At this point, I knew something was wrong.

At this point, I turned the gain all the way back down very slowly and noticed that as I turned the gain back down, the voltage would drop down to about 7 and then shoot back up to 22 once I reached about 3/4 of the gain setting. This is where I deviated. I took the DMM and instead of hooking it to the first channel, I hooked it to the "bridged" positive and negative. This ended up being the positive (+) on channel 1 and the negative (-) on channel two. The way the XD400 is set up is that there is a gain control for the front (channel 1 and 2) and rear (channel 3 and 4). I treated each one of these as if they were a two channel amp.

This is when I was able to get the voltage to climb to 26. When it peaked at 26, the gain was not even at halfway. This is what was different from the instructions that are in this forum. Had I left the gain turned all the way up and hooked a speaker to it, I wouldve probably destroyed that speaker. But, by hooking the DMM up to the "bridged" portion, I was able to get everything set perfectly.

Once I got the front and rear channels set at 26, I hooked the speakers back up. AMAZING is all I can say about the difference in sound between the pre and post DMM gain setting. At this point, I went ahead and played my music. Now before, i would be able to go to full volume on the radio and still not have enough coming from the rear. Now, since I set the gains at 3/4 volume (30 out of 40 on my stereo), I can turn the volume up to about 35 before it gets to the point to where its just too damn loud. The speakers dont have any distortion at that level (or at 40...I had to go full blast to try), but the sound becomes so ear piercing, you almost want to just turn it off.

Once I began playing my music (hip hop and r&b), I just had to make a small adjustment to increase the gains from the starting point. I think I only went up on the gains about a 1/16th of an inch before I started to hear a little distortion. I then went into the radio settings and adjusted my bass a little more because the pioneers needed to have a little more thump.

Overall, I am beyond impressed with the results of the DMM adjustments. By setting the amp by DMM, I can tell that when the music is turned all the way to the max, the speakers are right at the edge of distortion, but they never cross that line. I think that is the perfect way to be. Thanks to all who have made recommendations and I hope that I am able to help some people out who may run into something similar to what I did with the individual channels.

 

I've always just set my gains at 3/4, always sounds good. If I was gonna get technical I'd hook up a scope, but without one 3/4 gain has always sounded just fine. As always, YMMV, IMO, etc.

Edit... I've always tuned by ear, and it always seems to wind up at 3/4 gain!

 

What is your gain setting on the PBR300X2 driving the Infinity's?

 

Can you post how you came up with 25.8vAC?

I would have thought it should have been:

Square Root of (150*4)
=24.5 vAC

Maybe this little difference doesn't matter.

Cheers,
Chris

 

Nice write up!
Out of curiosity, what frequency test tone did you use?

 

Setting gains with a DMM….

Stock HK HU - bass / treble settings to 0 and volume @ 13 bars

Using the 1000hz test tone

Amp - PBRx2
122x2@ 4 ohms
187x2@ 2 ohms

Speakers - Infinity Kappa 62.11i
5-75W-RMS

Formula:

75wx2 = 150 (SQ) = 12.2VAC
122wx4 = 488 (SQ) = 22.09 VAC
187wx2 = 374 (SQ) = 19.3VAC

which one should I be using?

thanks,

V

 

I didnt do anything to the gains on the PBR because they already sounded perfect at speed. I adjusted that by ear and did the JL audio by DMM.

 

I used the test tone that is in the sticky part of this forum on setting gains. I just downloaded the tone to my phone and played it bluetooth thru my radio.

 

I would have to go home and get my sheet that I used to come up with it. It didnt matter anyways because that was just a starting point. I had to go up a little bit on the gains after using the dmm method because it still was not enough power going to the pioneers.

 

Can you tell me what gain you set on the PBR and if you're happy with it? Are you in AP for crossover setting? Thanks.