Gradual yet drastic decrease in amp output

[digitalrust]

Nothing about my system has changed in years yet my amp goes into protect mode more and more often. I am trying to figure out the cause. Deteriorating.. battery? speaker? amp?

The deterioration has been very slow and gradual (i.e. imperceivable day-to-day), but a few weeks ago I listened to some albums I hadn't heard in a while and realized so much of the low end is missing. The amp can hardly handle deep lows anymore.

I checked the voltage at the amp, very low. Found corrosion on the positive terminal, cleaned it up. Lightly sanded contact points. Amp output did increase drastically.. but it didn't last. It's still an improvement, but I don't understand how its performance can drop overnight.

I want you to tell me that the cause is my 3-year-old battery. However, I was under the impression that power depends more on the alternator than the battery itself.

So then my next guess would be lowering impedance on an aging sub (unfortunately I don't have a reference measurement) which would be too taxing on the amp (I bridged 2 channels). I'm hoping this is not the case.

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[honkyg 10+ year member]

what amplifier?

(in for potential bait thread)

 

[digitalrust]

what amplifier?

A second-hand powerbass asa 600.4 which has served me well for 6-7 years.

It's specifically audio with really low bass (say, below 30hz) that I can't get any decent reproduction on (except at very low volumes ofc, but sometimes not enough to overcome freeway road noise). The amp goes into protect mode.

My battery was last measured to put out 597 CCA of a rated 850. They say this calls for replacement, but my car has no problems starting in a cold winter climate. Which is generally where I would draw the line.

 

[audiobaun 5,000+ posts]

You can test your voltage at a car auto parts store such as Orileys, Auto Zone Ect. for free with a DMM see where your voltage is sitting and then at idle.Its best to check the batt in the morning before you drive and sitting over night.Its best to pull an alternator and have it bench tested rather than in the vehicle as well.You can even pull the battery and have them place a charge on it for a few hours and see if it holds or takes a charge within limitations. Thats FREE as well.Id recommend getting the BIG 3 done if you havent already done so.the stock wiring charging the battery is always bare minimum sized and is weaker than having the Big 3 to keep your voltage up for the demand.An AGM battery is really a nice to have under the hood as well.Id start there at the least

 

[audiobaun 5,000+ posts]

What vehicle and what does your supply consist of for the amplifier,and ohm load are you running?I guessing @ 2 ohms mono?/Bridged mono? Sounds like you may be starving for power.. As Ive always stated ,,It takes power to make power. Starvation can damage an amplifier eventually,sometimes instantly.(Ive experienced both as well as bad new batts and damaging HO alts in the process) One hell of an expensive lesson that was well over $1k to get it figured out.(Optimus Red Tops that Ill never buy again)

 

[digitalrust]

You can test your voltage at a car auto parts store such as Orileys, Auto Zone Ect. for free with a DMM see where your voltage is sitting and then at idle.Its best to check the batt in the morning before you drive and sitting over night.Its best to pull an alternator and have it bench tested rather than in the vehicle as well.You can even pull the battery and have them place a charge on it for a few hours and see if it holds or takes a charge within limitations. Thats FREE as well.Id recommend getting the BIG 3 done if you havent already done so.the stock wiring charging the battery is always bare minimum sized and is weaker than having the Big 3 to keep your voltage up for the demand.An AGM battery is really a nice to have under the hood as well.Id start there at the least

Engine off - 11.99V between battery posts

Idle - 14.30V between battery posts. 14.27V @ amp.

I've been considering the Big3 but the system used to be fine for my purposes. So at the moment I'm more interested in figuring out which part of the system has degraded.

What vehicle and what does your supply consist of for the amplifier,and ohm load are you running?I guessing @ 2 ohms mono?/Bridged mono? Sounds like you may be starving for power.. As Ive always stated ,,It takes power to make power. Starvation can damage an amplifier eventually,sometimes instantly.(Ive experienced both as well as bad new batts and damaging HO alts in the process) One hell of an expensive lesson that was well over $1k to get it figured out.(Optimus Red Tops that Ill never buy again)

2011 Crown Vic P71, these have a pretty decent alternator to power police equipment (130A if memory serves me right).

2 channels bridged, mono. The sub itself measures ~3.8 ohms of resistance (with no load, so I'm not sure if it means much). When I push on the cone, the reading jumps around a lot.

I'm pretty certain you're correct about it being starved for power. But this same setup worked for years, and maybe only over the last 6 months really gone downhill.

 

[JohnKuthe]

Nothing about my system has changed in years yet my amp goes into protect mode more and more often. I am trying to figure out the cause. Deteriorating.. battery? speaker? amp?
The deterioration has been very slow and gradual (i.e. imperceivable day-to-day), but a few weeks ago I listened to some albums I hadn't heard in a while and realized so much of the low end is missing. The amp can hardly handle deep lows anymore.

I checked the voltage at the amp, very low. Found corrosion on the positive terminal, cleaned it up. Lightly sanded contact points. Amp output did increase drastically.. but it didn't last. It's still an improvement, but I don't understand how its performance can drop overnight.

I want you to tell me that the cause is my 3-year-old battery. However, I was under the impression that power depends more on the alternator than the battery itself.

So then my next guess would be lowering impedance on an aging sub (unfortunately I don't have a reference measurement) which would be too taxing on the amp (I bridged 2 channels). I'm hoping this is not the case.

ENTROPY strikes again!!

Especially in high powered systems!!

John Kuthe...

 

[tymoto21 10+ year member]

I would guess a bad connection

Check all power connections and ground connections

Measure voltage at the amp when playing higher volume

 

[Jeffdachef 5,000+ posts]

doesnt matter if you have a good alt or not. If your battery is taking a sh*t or if your wire is internally corroded or burnt up, sh*t will eventually fail.

 

[honkyg 10+ year member]

take some pics of your wiring front to back, ya never know, someone might see a problem you missed.