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post #1 of 13 Old 12-10-2011, 07:38 PM - Thread Starter
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I'll admit, I've been out of the car audio scene for a long time. When I purchased my Impreza, 6+ years ago, I had gone more towards performance parts/autocross than audio... anyways.

I have a 4 channel Alpine amp that I bought a couple months after I bought the car - along with 4 way Pioneer 6.5" in the front doors and Alpine 6.5" in the back. (It's a half assed system... Pioneers focus more on the higher end freq of the sound and the Alpines in the rear deck provide lower/midbass) -- and I do not have a sub with this setup. Can't stand trunk rattle and also didn't want the added weight.

Anyways; tonight on my way home from work there was a mild pop through all four channels - then the sound cut out - and then sound came back. All in all, the total experience lasted about 1 second. When the music came back on everything seemed fine. I wasn't playing the system loud, hardly audible actually but tonight when I was cruising around town I noticed that it seemed like the music was ... diluted? For lack of a better word. Almost like it was watered down, hardly any midbass but the highs were there. I spent about 20 minutes diagnosing and scratching my head - and realizing that I have no idea wtf happened. I'm thinking it's an issue with the amp... but I'm on a very tight budget right now and before I go messing around and buying stuff I don't need I was hoping to get some feedback from some people on here to see what you guys think.

So, thoughts?

tl;dr - watered down/diluted bass/midbass sound from all four speakers in my car after a one second pop/loss of sound/audio coming back. Need suggestions on cause.

Thanks for reading.
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post #2 of 13 Old 12-10-2011, 11:03 PM
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Something shorted, simply broke or if you're lucky just got loose. Time to troubleshoot.
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post #3 of 13 Old 12-11-2011, 05:50 AM - Thread Starter
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Wires to the amp are fine, as well as to the speakers. I'm going to pull the HU and see what's going on but I'm leaning more towards the amp. It still clips at the same volume if I turn it up louder; but the sound is the same throughout. Volume increases but blargh.
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post #4 of 13 Old 12-12-2011, 08:51 AM - Thread Starter
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HU and wiring is fine... I guess a better way to describe the problem is it seems like the amp is running at half the power as before the pop/etc.
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post #5 of 13 Old 12-22-2011, 11:28 AM - Thread Starter
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So just an update... I've checked all speaker wiring, wiring to HU, wiring to amp, levels, settings in HU and nada... still sounds like there's a filter on any frequency below 80 or 60hz. Both HPF are set to off though... Gain for front and rear channels set to nominal (0)... thinking it's the amp. If I increase the gain for either set of channels the volume gets louder, and I can see the drivers working - but still that damn filtered sound.

Anyone else have any thoughts before I start replacing 'ish?

Edit: For what it's worth - the amp is an Alpine MRP-F240.
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post #6 of 13 Old 12-22-2011, 12:08 PM
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Try connecting the radio/deck directly to the speakers, thus eliminating the amp. If all sounds good then you found the problem. Good luck.

I current have an amp in which one channel sometimes does what you described, thankfully I've a spare amp (old install, different car) so I'm going to swap that in this weekend. At first I thought it was a speaker or wiring issue because if you slammed the door the speaker would sound fine again. So I pulled the door panel off and checked... nope all wires are still tight.

My equipment list is here. Playstation Network ID = jmii ...that's JM roman numeral 2
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post #7 of 13 Old 12-22-2011, 12:10 PM - Thread Starter
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Haha... I'll admit, when I installed the HU I was being lazy, since I had no intention of using the oem wiring or speaker outputs of the HU, I didn't bother merging them in the harness. At the time, I thought I was being efficient since I had already run my own wiring throughout the car and to the amp... needless to say, I feel like an idiot now. Maybe I'll break out a rubber mallet and tap on the amp in a couple different spots to see if that helps at all. It's under my passenger seat so all I have to is move the seat up.
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post #8 of 13 Old 12-22-2011, 12:24 PM - Thread Starter
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Another thing, it's only on channels 3 & 4 -- I realized I enabled the HPF when I initially installed the amp. When I switched it off, channels 1 & 2 were unaffected by this issue.
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post #9 of 13 Old 12-22-2011, 12:35 PM - Thread Starter
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Quote:
Originally Posted by JMII View Post

Try connecting the radio/deck directly to the speakers, thus eliminating the amp. If all sounds good then you found the problem. Good luck.

I current have an amp in which one channel sometimes does what you described, thankfully I've a spare amp (old install, different car) so I'm going to swap that in this weekend. At first I thought it was a speaker or wiring issue because if you slammed the door the speaker would sound fine again. So I pulled the door panel off and checked... nope all wires are still tight.

By the way - as I was giving my issue more thought - it sounds like yours could be a loose ground? Just thought I'd throw that out there.
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post #10 of 13 Old 12-23-2011, 09:37 AM
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Quote:
Originally Posted by loft View Post

By the way - as I was giving my issue more thought - it sounds like yours could be a loose ground? Just thought I'd throw that out there.

That only effects one channel? No... if the ground was loose the whole amp would shut down. This is 4 channel amp too, and only 1 channel cuts out randomly. I tested by swapping the speaker outputs and the problem always stays in this one particular channel. Before it cuts out its proceeded by a some static so I'm sure something internal in the amp is messed up. This low budget amp has been in the back of my truck for nearly 10 years so failure at this point would be acceptable in my book

The amp you got its a good one, so I'd be surprised if something inside died... but hey you never know. I wonder if the HPF is stuck "on" somehow. While the amp is off you might want to flip the switch (to low-pass) then turn everything back on in an effort to determine if the electronic crossover still works.

My equipment list is here. Playstation Network ID = jmii ...that's JM roman numeral 2
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post #11 of 13 Old 12-23-2011, 02:38 PM - Thread Starter
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Quote:
Originally Posted by JMII View Post

That only effects one channel? No... if the ground was loose the whole amp would shut down. This is 4 channel amp too, and only 1 channel cuts out randomly. I tested by swapping the speaker outputs and the problem always stays in this one particular channel. Before it cuts out its proceeded by a some static so I'm sure something internal in the amp is messed up. This low budget amp has been in the back of my truck for nearly 10 years so failure at this point would be acceptable in my book

The amp you got its a good one, so I'd be surprised if something inside died... but hey you never know. I wonder if the HPF is stuck "on" somehow. While the amp is off you might want to flip the switch (to low-pass) then turn everything back on in an effort to determine if the electronic crossover still works.

Ahh my bad, was thinking subwoofer for some reason.

The amp is/was great! I got it new from a friend who was in competitions so I didn't pay retail, but I definitely got my money's worth either way. I've had it for several years (can't think of exactly how long) but I'm going to try that tomorrow before the whole Christmas celebrating stuff begins. I also brought a rubber mallet home from work to thump on it a couple times (not hard)... but now that I think about it, I doubt there are any relays/etc to get stuck inside the amp... who knows. If it's dead/dying then I guess it won't matter much.
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post #12 of 13 Old 12-27-2011, 09:23 AM
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I swapped out my amp this weekend... the new one (Kicker ZX350.4) works perfectly and its louder/cleaner then the broken amp despite being rated at 100 watts weaker. If you shake the old amp you can hear rattling around inside the case so I'm guessing something semi-important came off the mother board. So maybe it could have been fixed, but like I said it was 10 years old so no surprise to see it finally die. Plus it wasn't the highest quality unit to being with.

My equipment list is here. Playstation Network ID = jmii ...that's JM roman numeral 2
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post #13 of 13 Old 12-27-2011, 12:44 PM - Thread Starter
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Quote:
Originally Posted by JMII View Post

I swapped out my amp this weekend... the new one (Kicker ZX350.4) works perfectly and its louder/cleaner then the broken amp despite being rated at 100 watts weaker. If you shake the old amp you can hear rattling around inside the case so I'm guessing something semi-important came off the mother board. So maybe it could have been fixed, but like I said it was 10 years old so no surprise to see it finally die. Plus it wasn't the highest quality unit to being with.

Nice! I swapped my wiring and the rear speakers play fine now... but I'm not going to leave it like this. Just waiting until next paycheck to order a replacement.
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