Speaker Clipping?

HurricaneBob

I finally got some Polk MM's installed in my Jeep, but it sounds terrible, and I can't turn the volume up past 9 (out of 35) without some serious distortion in the speakers.

Here's my set up:

Stock Jeep Head Unit
Spliced into factory wiring to
Audiocontrol LCQ-1
RCA cables to
PPI P900.4 Amp
New speaker wiring (16 gauge) to
MM 6501's (front) and MM 651's (rear)

My initial thought was that it sounded like clipping, but if it was, would the distortion be the same in each speaker?

The front's are worse than the rear, but the front driver's side is significantly worse than the front passenger's side.

Anyone know what's going wrong?

Thanks!

pentoncm

You've got multiple places for potential clipping.

Where is the output set on your line output converter? Max output is 8.5V which is going to be too much for your amp.
Are you boosting any of the bands? If so stop, only cut.
Where are your gains on your amp?

At volume 9 out of 35 is it really loud?

HurricaneBob

I set the eq bands to flat on the LOC and the output is set in the middle of the range.
The gains on the amp are somewhere in the middle as well - it's only a black screw, so it's difficult to tell exactly.

At 9 the volume is decent, but by no means loud - it would be difficult to hear on the highway.

pentoncm

Is the maximized light flashing a bunch when you turn the stereo up?

Try turning down the output on the LOC, while turning up the volume on your deck.

HurricaneBob

i'll give that and try

MacLeod

Sounds like the gains are too high on the amp with the line driver in the LCQ. Halfway is usually the highest youll want to keep your gains at so just turn them down to the 9:00 position.

HurricaneBob

So I turned the gains on the LCQ all the way down, and that has definitely helped, but I'm still getting some distortion in the front driver speaker - it almost sounds like it's bottoming out in the speaker pod.

I haven't had a chance to change any of the settings on the amp yet, but I'm going to try taking the gains down there as well when I get out of work.

Should I be doing anything with the filters on the amp?

Also, I have the cross overs set to 0 db (the other setting is -3 db). Does this make a difference?

Thanks for the help!

MacLeod

The gains on the amp should do the trick. That's what its for, to match the input signal its getting with its output. Leave the other settings on the amp alone. The settings on the crossovers are to attenuate the tweeters. Usually the -3db is the better setting to blend the tweeters in with the mids a little more.

HurricaneBob

Thanks. Will try it tonight and let you know how it goes.

HurricaneBob

I've been working a ton, so I just got around to turning down the gains on the amp.

It definitely sounds better, but it still doesn't sound all that great; although, that could be because I haven't set up the equalization yet. Also, I'm wondering if I turned the gains down too low - when I get to about 22/35 I start to notice some distortion in the tweeters.

One other issue that I've noticed is that once I get to about 22, I notice a sound similar to the clipping coming from the front driver mid - this is the only speaker that does this, so I'm thinking that it could be one of two things:

1. I failed to install the speaker pod correctly and it's vibrating in the dash
2. The speaker is bottoming out in the pod

Anyone have any suggestions?

Thanks!

MacLeod

If you set the gains too low, you wouldn't be getting distortion. You might still have them too high relative to the gains on the LCQ.

Might try turning everything off but the front mids then turn the gain all the way down on the amp then turn the volume up to 75% Then turn up the gain til you hear distortion them back it off a bit. Then set the other gains til they blend with the mids.

HurricaneBob

The gains on both the LCQ and the amp are as low as they can go.

I can't turn the volume up that high because of the mid on the front driver's side - I might disconnecting just that speaker and tuning the others.

Just to make sure I understand:

1. Make sure all gains are at minimum position
2. Turn volume up to 75%
3. Turn up the gains on the amp until there's some distortion, then back it off a bit
4. Tune the gains on the LCQ

Is that it?

Thanks!

MacLeod

I'd try it with the gains on the LCQ down as low as they go then try it.

I don't know dude, it might be worth it to just sell the LCQ and just buy an aftermarket head unit. That would clean up all your problems.

HurricaneBob

That's actually what I've been thinking...

First I'm going to disconnect the one speaker that's been giving me problems and see if I can get the other three working well.

If that doesn't solve it, then I think I need to get the new head unit.