kingomar

hey guys. i have an alpine pdx 4.150 amp powering 4 mid range speakers. i also have an alpine pdx 2.150 amp powering 2 subs. at high volumes, the pdx 4.150 that powers the mid range cuts out. the blue light on top does not change the color and stays lit even as the music cuts off. i checked all the speakers and the grounds, no problems there. funny thing, is the subwoofers and the amp for those do not have such a problem. my question is will a cap help my situation? if so, how big a cap? i always though capacitors were for short bursts of voltage, not for sustained output to midrange speakers. or is it that im just pushing my speakers too much? thanks for your help in advance. i also want to add that there is no dimming of lights or anything like that.

here are the stats on the speakers:

Impedence: 4 Ohms
# • Power Handling Capacity (Peak): 300 Watts
# • Power Handling Capacity (RMS): 100 Watts

the amp:

RMS Power (at 14.4V THD+N,20Hz-20kHz)

* • Per channel into 2 ohms : 150W x 4 (<=1%THD+N)
* • Per channel into 4 ohms : 150W x 4 (<=1%THD+N)
* • Brigded 4 ohms: 300W x 2 (<=1% THD+N)

LexGX

iTrader: (1)

How high do you have the amp powering the speakers turned up? Try turning down the amp and see if it helps. A cap wouldn't really help. It helps if your lights are dimming when your subwoofers are hitting. Other then that, don't waste your money on one.

kingomar

hey thanks for the reply. my gain is currently set at a little less than midway. there are three settings: MIN, NOM, MAX. I am about midway between MIN and NOM.

Billy305

iTrader: (2)

Doesn't sound like a cap will help. All it is is basically a extra battery that holds power for things like when the sub hits a long deep note. When an amp cuts off like that its usually because its getting to hot in my experience.

kingomar

the overheating theory makes sense, but the thing is this happens even when the amp has been off all night and then i turn up the music.

GCOP

How do you have the power distributed to the 2 amps? Also what is your impeadence load on the amp that cuts off?

You are right about the cap, it is for short burst of power, it charges, and dischages rapidly, it will stop "peaks" and "vallys" in your power supply to your amps to give them a steady voltage flow, they are found in use most often with sub amps because they tend to be more power hungry than a mid/high amp, but you can, and INHO should use one in a higher powered system. Put it in line prior to your distribution block in a multiple amp set up. You may not "need" it per se, but it is not going to hurt anything, it will lessen the demand on the cars electrical system, and that is always a good thing.

LOL but back on point, it does not sound like that is what your problem is....

rich001

Try troubleshooting the speakers, disconnect one speaker lead at the amp and play your stereo loud. Keep disconnecting the other speakers until you isolate the speaker that might be shorting out. Sometimes the tinsil leads behind the midrange cone travel too far (when playing loud) and touch metal behind the speaker. Another thing you may try is to reground the PDX-4.150 to another spot and make sure you sand the metal. Trial and error.

kingomar

GCOP, i am currently using the power wires that were there for the stock amplifier. do you think i need to attach it directly to the battery? also, how do i measure the impedance at the speakers when they cut off.

rich001, i will try these suggestions and get back to you.

thanks again.

@lpher

One thing...where did you connect the ground (GND)?

GCOP

You can measure impeadence with an ohm meter. Impeadence is resistance to power. If you have a mulit meter, set it to ohms ( the little horseshoe looking thing) disconnect one speaker wire input from your amp ( I would test the front) left or right see what the meter reads. You should see 4ohms at each corner, it may be a litle more or less, if you see something really low, thats the one that is your problem. Do this with the amp off.

Also I would be inclined to get the power diirectly from your battery, no question. Let us know how it goes.

@lpher

Whoops! Didnt see this earlier...

This is a VERY big no-no The oem wiring isnt capable of handling the power your aftermarket amp requires to function...and im pretty shure this is your (main) problem source.

Personally i wouldnt use a power/groundwire less than 4gauge on that amplifier.

kingomar

thanks @lpher and GCOP. Im gonna switch the power source directly to the battery and ill measure the impedance. i appreciate all the help.

kingomar

hey guys. quick question. i was thinking of doing the big 3 upgrade as well. i took a look under the hood and the alternator is pretty deep in there, probably going to need remove the radiator (beyond my expertise). is this upgrade worth me spending money to have someone do it? also, i can change the battery negative to chassis wire on my own. is it worth just changing that one wire?

hopefully, hooking the amp directly to the battery will help solve this. thanks.

GCOP

start with the power directly from the battery first, that is at least "some" of the problem.

Like @lpher mentioned, just not a good idea to use the OE power source for the amps. You need current, 4AWG is a good suggection, come from the battery, and split it with a distribution block and use 8AWG inputs on the amps, if memory serves, thats what they have. But use the biggest they will accept. Start there first......

kingomar

thanks GCOP. will post as soon as i have a chance to do it. all the help is much appreciated.