Alpine/Infinity - Less Bass Then Expected

I've slowly been piecing my system together into a Saturn SC2. I've done other cars in the past, and done them crappy. So with this car I decided to do everything right. But now that I'm done the bass performance just dosn't seem very good. Heres my setup: Alpine CDA-7893 (4v rca outs for front/rear/sub) Infinity 65.3 6.5" 3-ways in both doors and rear deck Infinity 10.5T component tweeters in from doors Alpine MRD-M300 Class-D Mono power amp (150w @ 4ohm, 300w @ 2ohm RMS - actual rating per testing is 340 @ 2ohm @ 14.4) Infinity Refrence 10" Sub (275 RMS) in a Type 1 QLogic box 4 ga wire from battery and ground to distribution blocks, then 8 ga to amp Lightning Audio shielded RCA Lightning Audio 12 ga speaker wire Everything is in phase, amp and reciever both getting enough power. The amp displays the voltage at 14.4 - 14.5 while the motor is running. Sound "quality" is great, crystal clear up to about 18 on my recivers volume (goes to 35), after that I start to get crakling mainly because the deck can't power the speakers. But the bass sucks. Overall it sounds pretty good but it dosn't hit at all. I've played with the crossover settings on both the head and the amp. Right now the head x-over is disabled and the amp is set for 160Hz. Subsonic filter goes from 15 to 50 but I really didn't notice a difference anywhere through the range. Input level is adjustable from 0 to -24Db (it says for .5v - 4v) and I'm using 4v preamps but at -24Db I get no sound so its set for 0db. I've also tried boosting the bass at the head unit, which if I play enough I can get bass that kinda hits but sounds very muddy. So as it sits I just have bass that fills in below the other speakers, which sounds o.k. but is less then I'm looking for. Anyone familiar with this amp or head unit or can tell me what I'm doing wrong. I'll admit I'm not sure on all these settings, I do know that when I put a high pass crossover on my 6.5" speakers set at 120Hz and the lowpass to the sub at 160Hz I noticed that distortion was reduced at higher levels (6.5" don't have to work so hard I imagine). Other then that unless I boost a frequency through the bass boost feature on the head unit I just can't get anything out of it. And as a side note the Alpine's amp display will should voltage, amp draw, and temp. The voltage like I said goes between 14.4 and 14.5 but the amp draw has never changed from 0.8A. This should draw much more then this I would imagine. Thanks for your help, sorry this is so long. Allan.

What you need is an amp to power the speakers so that you can properly utilize the full potential of the HU & the MRD-300.  After that you need to be able to set your system properly to the HU's output and the amp's output. Always have your HU set to 0 for bass & treble along with no BBE or LOUD attenuation.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

Well, next on the list will be a Alpine MRV-F340 in about a month. Thats why I ran the 4ga to the back already with the distribution blocks, in preperation of another amp. I also already ran two more pairs of RCA from the HU back and two pairs of speaker wire (12ga...overkill but I had extra). This weekend I'm going to try playing with the gain settings on the amp. But if anyone has any more suggestions please let me know. Thanks. Allan.

the Infinity subs arent really what you would call hard hitting subs...I am not sure either what you consider hard hitting...after playing around with the Infinity lines, I very quickly came to the conclusion that they are designed precisely for what you described...as a fill in for bass below the frequencies that your mids should be running at...not really there to win any kind of noise competition... how many cubes is the QLogic box? ported or sealed?

The Q-Logic is .60 cubic feet sealed. The Infinity literature recommended a .65 sealed box so I figured this would be a good match. The box is lined with about 1.5" of fiberfill on all sides except the front. It is stapled down on all sides also, makin sure nothing could fall onto the woofer. As for the Alpine amp, no this does not interface directly. I know they do sell a module that will let you control up to 8 of the MRD series amps. In fact when I did the setup for the amp it asks for a ID number to keep them apart. I can't imagine having 8 amps. The infinity does do a great job of filling in the lows, I just think its not as loud as it should be. Also as for the comment on the 0.8 amp draw. I was thinking the exact same thing. The amp has two 25A fuses so lets assume at max power it draws 50A. I'm using a single 4ohm load, so since max is drawn off of a 2ohm load lets say mine will never reach 25A draw (which is prefectly fine by me...). If I turn the amps gain to 0 (from the 0 to -24db range) and my HU's subwoffer boost to +15 (from 0 to +15). I still draw 0.8A. If I trun on my bass boost at say 80Hz and put it up 10Db I get some volume and it hits a bit (although muddy) and it still draws 0.8A. So what I'm going to do tomorrow along with everything else is make sure my ground connection is good where it meets the car. Also I may want to tap a 4ga form the battery to the frame as the Saturns have dual 6ga coming out, one to frame, on to engine block I believe. The positive is direct to battery but I may be limited on ground. Anyway I can test this for sure as I am getting 14.4 volts. Can I put something across the 4ga positive and negative at the distribution blocks to test possible amprage without hurting the cars electrical system? Any other thoguhts appreciated, thanks to those that have replied. Allan

Well, I just ran into a bit of cash so I ordered a Alpine MRV-F340 to power the front and back speakers. Tomorrow morning I'll go through the stuff mentioned above. The ground connect is to a piece of metal behind the rear seats, connected to the rear deck. I'm wondering if it has too much resistance between this piece and all the welds that get to the actual body metal. I have a multimeter so I'll ohm out the connection between the battery ground and the amps ground. If theres a decent amount of resistance I'll either redo the ground connection (sand it down and retighten) or mount it somewhere else. If its good I'll check the power the same way. If both are good I'll check the voltage on my RCA's coming back, the Alpine HU has 4v preamp outs so I'll make sure thats about what there delivering. And then I'll reset up the amp with the suggestions above and see what happens. Once I'm done I'll post again with what I found. Thanks all, Allan.

vseven wrote: The box is lined with about 1.5" of fiberfill on all sides except the front. It is stapled down on all sides also, makin sure nothing could fall onto the woofer.

Take out the staples. Stapling the fiberfill to the side of the box kinda defeats the purpose of having it in the first place. The purpose is to change the way the sound wave bounces/moves in the enclosure. I've always had better results when the fill is loosely placed in an enclosure. Just make sure your ports aren't blocked. If you search on polyfill on this site, you'll find some more of the same answers. Just a thought...Squirrel

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[QUOTE=wvsquirrel] Take out the staples. Stapling the fiberfill to the side of the box kinda defeats the purpose of having it in the first place. [QUOTE] I should have rephrased that. Its stapled, but I kinda made a small hole in the fill, stapled, and recovered. So say the bottom 1/4" - 1/2" is flat, but theres a good 1" of fill above the staples. Its not flat and dosn't look like the staples are even there. Its like if you cut a small slit in carpet and then screwed a screw into the slit so your just catching the bottom edge while the actual carpet seals back around. Good suggestion though, I can see why stapling the stuff flat to the side would be counter productive. Allan