speakers cutting out at higher volumes

**norcizz** · 12-14-2009, 04:01 PM

alright i just recently installed a new headunit, component speakers in the front doors, and and amp in the trunk. everything was working fine until yesterday i connected the subwoofer, which i received for free along with the amp, just to see how it sounded. sounded good but i took it out until a later day when i felt like installing it properly. later in the day i tried turning up the volume and the front speakers running from the amp are cutting out. then they come back for like a second. and then off again. the rear stock speakers are running off of the headunit so those stay on just fine through all of this. i can listen to it at lower volumes just fine but this is very frustrating. any help would be greatly appreciated. my gear is as follows:

old alpine mrp f257 http://vault.alpine-usa.com/products...M_MRP-F306.PDF
this is bridged to run Polk MOMO MMC6500 components
head unit is an alpine cda-105
and the subwoofer is an old mtx thunder 5000 4 ohm model (only connected for like 5 mins)

**soundman98** · 12-15-2009, 12:02 AM

i think the headunit needs to be ripped out and replaced with a computer

you mentioned that you have bridged both pairs of speakers-- is this presenting a 2 ohm or 4 ohm load on the amp? i think that is the first thing you will need to check-- i have a hunch that is where your problem is..

**norcizz** · 12-15-2009, 02:02 AM

while i dont know of any way to test that, i assume its 4 ohm. im just getting that from the users manual, it says 4 ohm stable in bridged mode. i connected everything like the diagram on there.

**rijndael** · 12-15-2009, 04:04 AM

I agree with Soundman

Originally Posted by soundman98

i think the headunit needs to be ripped out and replaced with a computer

how are your wire connections to both your amp and your speakers? could they be coming loose with the increased vibrations? (i'm referring to both your speaker wire and your amps power and remote lines...)

**bes51659** · 12-15-2009, 04:27 AM

It is probably a protective circuite in the amp that is activated. I agree that speaker impedance is probably too low, but it could be a temperature thing too however unlikely.
Or if load is correct, the amp is defective.

A bit confused about the bridge thing. Maybe you are too? ;-) You are aware that you get 2 ohms when parallelling two 4 ohm speakers?

**Crinos** · 12-15-2009, 05:03 AM

If you know the impedance... You can use this calculator if you are unsure of the math

http://www.bcae1.com/spkrmlti.htm

**Tengis** · 12-15-2009, 05:39 PM

You might have a speaker/sub or something that is shorted. Ive had similar issues when a speaker was on its way out.

**soundman98** · 12-15-2009, 05:56 PM

get a digital multimeter-- if you have a harbor freight store near you, they sell them for about $5. set it to the 200-ohm setting(looks like a horseshoe), remove the speaker wires from the amp, and put the leads from the meter on the wires-- the display should change to a number-- that number is the resistance. if you have more than one speaker connected to the same spots, make sure to keep them twisted to gether as you are testing with the meter.

i agree with most of what has been said-- some amps will not stop working until they overheat, no matter what the resistance is, and some amps will not work with the wrong resistance...

and i just want to put this out there, so you are a little familiar with this stuff:

'most'(there are exceptions) car audio speakers are 4 ohms. look at resistance like different sized water pipes-- the lower the number, the larger the pipe, the more power can flow through faster.

connecting two 4 ohm speakers in series (positive from the amp goes to the first speaker, and the negative is connectied to teh positive of the second speaker, who's nigative lead connects to the negative on the amp) will give you a 8 ohm load.

connecting two 4 ohm speakers in parrallel (positive wires of both speakers are connected together, and go to the positive on the amp, and negative wires on speakers are connected together and connected to the negative on the amp) will give you a 2 ohm load.

also, most speakers are around a certain resistance, so don't worry if 4 ohm speakers measure 3.7 ohms, or 4.3 ohms-- as long as they are near to it, they should be fine. and any speaker that you connect to and the meter shows a very large/small #(either a number below 1 ohm, or higher than 20ohms) will indicate a problem with the speaker.