First, the equipment I have is:

HU: Alpine CDA-9807
Front speakers: alpine 6.5" comps - spr-17s amped by mrv-t320
Rear Speakers: alpine type r 6.5" coax
Sub: 10W6v2 (in a custom fiberglass box built exactly to JL specs)
Amp: 500/1v2 amplifier

To correctly set I see that JL says the following
1.) make (or use their tone cd) a 50 hz tone CD recorded at -0dB (which I did using a tone generating program then using Adobe Soundbooth to amplify it to the -0dB level since it came from the tone generating program out at -12.04dB)
2.) Disconnect all speakers from the source unit
3.) Play the 50hz tone CD at 3/4 source unit volume
4.) set the amplifier input sensitivity so that a multimeter reading of the output is 31.6 volts.

My alpine CDA-9807 goes up to level 35, so I set the level of the head unit at 27 (3/4 level of the max) and then set the amplifier to 31.6 volts. Well when I did this, I could say I was less than impressed. The volume of the sub seemed minimal. I was looking for a sub and amp that wouldnt be to loud and would sound very nice. This low volume didnt sound too nice...or at least as nice as it should for that price tag. I did some reading online and people said "for loudness, the 10w6v2 wasn't a good choice". But surely the sub has to be louder than what it is now in my car (could barely tell a difference with it on and off in many songs).

Well I figured that it is impossible for me to ever turn the level of the head unit to 35, so I backed the calculation of the 3/4 down to a level of 30 (which make the 3/4 level to 22) and set the voltage of the amp to 31.6v. Now the sub is sounding more like I was thinking; plenty of volume while providing a very clean bass sound. One more note to give is I dont have bass boost on; to me it sound better with out it turned on.

Is backing this calculation sound level down so the amp has more output like I did a good or bad idea? I will never reach a volume level 30, and even level 22-23 is the loudest i will ever go. I would just like a few opinions since this is the first JL amp I have set and I dont have a scope to check graphically for distortion. Also, if others have this same problem, this post might help them set their inputs correctly.

 

It will not hurt anything.

What kind of box is the sub in?

What type of box?
What is it constructed of?
What is the net volume?
What is port volume, [if the box is vented] and what kind of port, [round square or slot]?
Is the box internally braced?

The output of a sub has more to do with the box then how the amp is "set up". 94

 

Its a sealed fiberglass box. the base, back and part of the side is 3/4" MDF. I glassed the inside of the box with plenty of glass to make sure its plenty thick/strong (im confident if i smacked the fiberglass sides with a hammer, it might make a little surface scratch).

You might have seen a post on this forum with the picture but if not, this is the construction of it. The glass doesnt look too thick on the very edge but everything was thickened up:




When I calculated the 3/4 volume based off of the 35 volume level, the sub didn't sound like it should (not very much volume at all). I realized if the amp was "turned up" more, it would sound perfect. Thats where I got the idea to back down the max level to volume 30 (even that point i will never reach) and re-calculated the 3/4 volume. Now I think the sub is at a perfect volume level; not too loud and the sound quality is right on.

 

What is the gross volume of the box?

Are you using the Alpine HUs internal amp to drive the rear speakers?

If so, did you wire the HUs 12V constant, [yellow] lead directly to batt. and add a ground from the chassis of the HU to the cars chassis?

If not, you may be limiting the amount of current the HU needs, the stock power, [12V constant] and ground was not designed to supply current to a "high power" aftermarked HU.

However, if it's working, don't fix it. 94