Bass isn't pounding like it used too...

Systems

Okay here's my situtation. Before I took my car in for maintenance, my bass was hitting pretty hard. After my car comes out of maintenance, bass was barely hitting at all. Question is what would cause that? I can't go back to the dealer to tell them to fix it because 1) the sub system still works but just doesn't hit hard at all and 2) I'm in San Jose and the dealer I took it to is in Santa Barbara (289 miles apart).

Specs:
2 x Polk/MOMO MM12 (the sub and enclosure)
1 x Polk/MOMO C500.1

I thought it might have been the amp that just blew out. I tried replacing it with two brand new C500.1s and both had the same results. I checked my wiring and it's fine. I checked the subs to see if there was any damage but from what I could see, they seemed alright.

Some things I thought that might be wrong is the head unit, my battery (not feeding enough power to the amp), or the power wiring. Anybody have any thoughts? I really miss the bass...

Thanks.

MacLeod

Hmmm...thats a strange one.

A couple longshots but if your head unit has a sub output make sure they didnt somehow turn it down.

It may be possible they knocked the wires loose on one of the subs and wired it back out of phase. That would kill your bass.

If you have a friend with a sub box thats easily removed, you may want to stick it in your car and make sure its not your subs that have stopped working.

The gain on the amp may have gotten turned down.

Get a voltmeter and check the voltage at the amp to make sure its not a voltage problem.

If your subs are in the trunk of your car maybe they got moved around some and are now in a spot where they get a lot of cancellation.

Try some of these and also give us a more detailed description of your install and that may give us some more clues.

neomagus00

from the very limited info we've got, i vote HU. i've had to replace a faceplate that i burned out when i jumped my car without switching off the HU's power line :eek: (i was listening to too much music with the car off ). perhaps the dealer did something to the electrical system that caused a damaging surge?

i'd say try swapping the subs if you can, first, then if that doesn't work or you can't, try the HU. (after you've tried mac's other suggestions, naturally)

Systems

Thanks for the info.

Answers to MacLeod:
- My headunit is configured exactly the way it was before my system died. Checked out output settings and they were fine.
- I flipped my subs upside down to see if that was the case. The wires are still firmly attached to the posts.
- I have a remote gain so the amp is set to max but when I crank up the gain, it doesn't produce that much gain.
- Subs are held in place. I have L-brackets drilled into my trunk to prevent them from moving around.

I haven't tried measuring voltage and stuff. I don't have a voltmeter that can handle that much current. Do I need a voltmeter that can accept 30A or can I just use any voltmeter?

Answer to neomagus00:
I don't know if this produces the same output as the head unit (input impedence-wise) but what I did was I took my laptop and plugged in from the headphone (3.5mm jack) to the RCA (L and R) and got the same results. BUT! It did sound a tiny bit better. But again, I'm thinking this might not be a good way to test this because I'm not sure of the sound card's output impedence compared to the headunits.

I was planning to goto a stereo shop to see if they can help me out but I don't want to spend the money (considering I just did a major maintenance) so I thought I give a shot here. But anymore input will be helpful. Thanks again guys!

TrappedUnder Ice

What did the shop do too the vehicle. Too me....sounds like a voltatge/current issue. If no other perameters changed...the main thing that could cause that would be a reduction in voltage or current too the amp. If they did a tune up....you may not be getting the same juice...and this could be the problem.

also.... battery could be going out. What kind is it. If it has a bad cell...you wont get the voltage you normally were getting if you are exceeding your Alts current potential also.

Wait...I know... Put a cap on there...see if that helps

neomagus00

okay, ignore that last line... but did i understand correctly when you sad you had your gain turned all the way up? because if you do, it is very likely they've been blown up.

Jstas

Ummm, while these are all good ideas, before zI go replacing ANY gear at all, I would start checking the areas where the mechanics were working. I took a vehicle in for service to have a transmission replaced. To do so, they had to tear apart the dash board and center console. When they returned the dash to its original position, they pinched a wire and grounded out the wire. It caused the left side speakers to cut out and the dash lights to go away when the headlights were turned on.

Check the work and make sure nothing is pinched or grounded out before you go replacing anything.

Systems

It's just a regular tune up done by a Mazda dealership (maybe THATS the problem). My car hit 120k miles so it's one of those larger tune ups. My car is a '98 Mazda Millenia. The alternator in my car is a 90A alternator so that shouldn't be a problem correct?

The battery I have is "old." I haven't changed it in a long time. It's an Energizer I believe but yeah, it's been a long time since I have changed it.

For the gain, the gain setting on the amp is at max becasue I have that remote that's connected to it (the one that comes with the C500.1). The Remote Bass control though is like maybe 1/8 circle away from min. As I stated previously, I have bought two other C500.1 amps and have gotten the same results.

Thanks.

MacLeod

Originally posted by nOrbX187

- I have a remote gain so the amp is set to max but when I crank up the gain, it doesn't produce that much gain.

This jumped out at me as well. If you have the gain on the amp all the way up then its clipping quite regularly regardless what the remote gain is set at cause its the one on the amp that counts. When an amp clips it sends out a signal about twice the wattage the amp is rated at (in this case over 1000 watts) and as you can imagine, kills speakers. The mechanics might have been playing with the stereo and turned it up too loud. Its likely it damaged one or more of the subs by either building up too much heat or over extending the suspension.

If you have a friend that has subs that can be easily removed? If so you should stick them in there just for a test and see if they work fine. If so then you know its your subs.

Systems

For the remote gain part, the Polk manual says that if you have the remote gain installed, set the gain on the amp to max. Here's from the manual:

"1 Remote Bass Gain Module Jack
Accepts telephone jack input connection from the remote bass gain module. Set GAIN (8) to max when using the remote."

That was how I had it set when it was working before.

As for damaging the subs, the MM12s are rated at 500RMS each (4 ohm impedence, 1000W max peak). The amp only puts out 500W x 1 @ 2 ohms so that would be only 250W to each sub. That's half of what the subs can handle. So if the mechanics were messing around with my sound system, the amp should've blown first.

spwuinmk67

Rated and actual power aren't always the same, the amp probably puts out closer to 600x1. And if they played with the remote gain control, they could've turned it up past clipping, which could blow them, even if the amp only puts out 600...

Systems

Those ****... Although, one thing I do have a sub gain setting on the head unit. I forgot about that cause I leave it at default. The Kenwood head unit I have, I can change the rear preout to sub preout. Then it gives me an option to increase the SW Level.

So it is possible for a weaker amp to blow out higher rated subs? Will Polk Audio cover that under warranty? Man, if they don't... Damn mechanics...

So I guess I should go buy a sub and try it out?

MacLeod

If the manual says to turn the gain to max then youre doing right.

When a 500 watt amp clips, itll send out a signal in the neighborhood of about 1000 watts! That amp actually puts out 600 watts so a clipped signal would be somewhere around 1200 watts (at over 10% THD).

Say you had a 100 watt amp on those 500 watt subs, you could clip it til the cows come home but the clipped signal wouldnt be much more than 200 watts which is well below the handling of the 500 watt sub so it would be fine. It would sound like **** but would be fine.