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I recently replaced my stock deck with a Pioneer DEH-4600MP, left the stock speakers intact, and put my 11 year old profile 250W x 2 Amp with an 11 year old kenwood box containing 2 x 10" subs, 2 mids and 2 tweets.
The stuff is very very old, but still sounds ok for now.

However, if I turn it up fairly loud, everything dims when the subs hit.
I don't think this old hunk of junk amp should be pulling enough power to cause this to happen.

The car is an 04 Civic Special Edition.

A few weeks after I purchased the car from the dealer it started making a strange vibrating whining noise whenever I came to a stop and it was idling.
The guys at the honda dealer said they weren't sure where it was coming from and replaced the power steering pump. The noise went away for a day or so, but I think it was probably just a coincidence. The noise came back the next day and is noticeable whenever I am sitting at an idle.
After putting in this new deck and noticing the lights dim, I'm thinking perhaps the noise is the alternator.... I don't know much about full size cars, being more of an RC junkie, am I on the right track here? Should I take it back and get them to check the alternator, or is it normal for my lights to dim like this in this car? My old car never had this problem with a virtually identical stereo setup.

 
Rep Power: 328

It depends on the amp draw of the amp honeslty. I've had 1000 watt plus setups not cause any noticable dimming in my civic when I had it, but I put a different amp in there that was power hungry and significantly less wattage yet the lights dimmed. I'd still get them to double check everything just to be safe. From there, you might want to try upgrading the big 3 wires, putting a better battery, maybe a higher output alternator (I'd do this last) or you may want to try a cap. I don't like caps, but in some instances they help with dimming issues.

 
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Guess I'll take it in to have the alternator checked.... Turning the AC on before I installed this deck had the same effect, noticeable drop in RPM and lights dimming.

On a side note, I have some SPL55g 5.25" speakers collecting dust here, is it possible to mount them in the front doors, or do I have to buy new 6.5" ones?

 
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I believe the front doors were suppose to be fitted with 5.25's but i shoved 6.5"s in my 2001 Civic Sedan if this helps...

 
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its made for 6.5"s but with some work anything will fit

 
Rep Power: 337

what size power wire are you using to go from your battery to the profile amplifier?

 
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upgrade the amps ground and alternator. if the lights still dim upgrade to a bigger cca battery, dont waste ur money on a cap. they will help stop the dimming but they also drop the voltage tot eh amp which means it will be weaker making the sound quiter. so double check ur grounds and upgrade if u need to with the power ur runnin 4gauge wire will be fine but if u plan to upgrade in the future bigger will work and will be less work in the future. also a bigger battery will help the alternator from whining cause it cant keep up with the ampers bein drawn. so bigger battery perferablly over 1200cca and bigger ground that are directly on the frame not the seat belt things or lil pieces of metal in the trunk, frame only. depending on the class of amp a good way to know the current it draws is the fuses on the amp, alot of cheaper amps claim 1000watt but only have 60amp fuse, but theres class ab amps that draw alot more but in return they have better sound.