Amp shutting off for a couple seconds at a time at mid-high volume

[Curtis Laudenslayer]

Warning: Lengthy explanations ahead.

2001 Pontiac Grand Prix

My system was installed by best buy, i lack the know-how to do it myself so sorry if i need a lot of explaining.

I have a JL Audio 250/1 Amp with a Diamond 12 inch ported sub. I do not know the specs of the sub because i got it as a present from a friend. (It was his old setup and he knows alot about this stuff so i assume the amp and sub are fully compatible)

After best buy installed it, the setup has been working flawlessly for over 2 years (apart from needing a battery replacement over a year ago, but the previous battery was the original one, so i think its understandable)

Starting about a month ago, i noticed my sub will cut out for a couple seconds at a time when i have it at mid to high volume. I took a look at the amp while this was happening and i saw that the LED light for the amp would turn off for the couple of seconds.
(The problem happens whether i have it running for a long time or if i have just started up the car, so its not overheating)
I looked online for the manual to the amp and it stated:

There is only one condition that will shut
down an undamaged 250/1 completely…
If battery voltage drops below 10 volts, the entire
amplifier will shut itself off.The green “Power”
indicator on the top of the amplifier will turn off
when this occurs.The amplifier will turn back on
when voltage climbs back above 10 volts... If this is happening in
your system, have your charging system inspected to
make sure it is working properly. A 0.5 or 1.0 Farad
rapid-discharge capacitor connected in parallel to
the amplifier power connections may minimize
these short duration voltage dips in many systems
that are having this problem.
For information on troubleshooting this
amplifier, refer to Appendix D

Then in appendix D...

“MY AMPLIFIER SHUTS OFF ONCE IN A WHILE, USUALLY AT HIGHER VOLUMES”
Check your voltage source and grounding point.The R.I.P.S. power
supply is rated to operate with source voltages between
11 - 14.5V. Shutdown problems at higher levels can occur
when the charging system voltage drops below 10-volts.These
dips can be of very short duration making them extremely
difficult to detect with a common DC voltmeter.To ensure
proper voltage, inspect all wiring and termination points. It is
also a good idea to improve the vehicle’s factory ground wire
and termination point.

So i checked my grounding wires, they are both extremely tight and attached to metal where the paint has been scraped off.
Since the sub plays perfectly well when the volume was below the certain volume it takes for a big sub hit to cut out the amp, i figured it was an electrical problem and needed a capacitor as the manual stated.

So i took it to best buy and had the guy check it out just to see what he would say.
He said he checked the fuses and wiring and it was all good.
He checked the voltage of the amp, and he said it wasnt dropping below the threshold. (which is troubling to me)
He said he hooked up another sub with the same wiring and blasted it, and he said that sub worked fine.
His conclusion was that my sub must be dying.
He explained that as the sub hits big, something inside it might be loose causing it to shut off.
I read somewhere that a sub short circuit could cause an amp to go into protect mode, so this might make sense? but...

My worries: I think the amp could be getting insufficient power for such a brief moment that he didn't detect it (As the manual states this could happen) And that the sub he hooked up to test just didnt pull enough power to shut down the amp as my sub does. Which would mean i just need a capacitor.

My question:
Do you guys think my sub is faulty or is my amp starving for power?

I will do my best to give any information needed! Thank you so much for any help
I just don't want to waste money on something that isn't broken and wont fix the problem.

 

[mymutter]

basically, if it worked fine with another sub, then it's the sub. I would ask to borrow a friends sub to double check (in an enclosure, not free air). If it does not shut down the amplifier, then yes, you have a bad wind on the voice coil, which is very very rare. they usually just burn themselves out when this happens.

if you did not mention that it worked fine with another sub (or the best buy guy said it), then I would be thinking voltage as well.

Do not get a cap, a capacitor is not a fix, they are not meant to keep voltage from dropping below 10, they are meant to provide the power needed for the 1/4 second it takes for your battery to begin the chemical reaction to supply the power requested. That is it. If you don't have the power in the first place, a cap will not help you. I would have a shop check out your charging system. specifically your alternator.

 

[Curtis Laudenslayer]

basically, if it worked fine with another sub, then it's the sub. I would ask to borrow a friends sub to double check (in an enclosure, not free air). If it does not shut down the amplifier, then yes, you have a bad wind on the voice coil, which is very very rare. they usually just burn themselves out when this happens.

if you did not mention that it worked fine with another sub (or the best buy guy said it), then I would be thinking voltage as well.

Do not get a cap, a capacitor is not a fix, they are not meant to keep voltage from dropping below 10, they are meant to provide the power needed for the 1/4 second it takes for your battery to begin the chemical reaction to supply the power requested. That is it. If you don't have the power in the first place, a cap will not help you. I would have a shop check out your charging system. specifically your alternator.

Thank you for this info. If i were to check another sub myself, it should be the same RMS as well correct?

 

[mymutter]

Most subs of decent construction will take the power for short times without any issues, I mean, you do not want to test with a 20 dollar speaker, so use some common sense.

If you have the ability to download test tones, try your current subwoofer at lower volumes with a 20 - 25 HZ tone, this will get the sub moving the most if can at lower volumes and see if that does it.

Or, even better,
go to harbor freight and buy a 10 dollar volt meter, and test the resistance of the subwoofer. (put it on the omega symbol) and then report back what you get. Do not move the sub when you do this and make sure that there is no vibration getting to the speaker. You can do this off just the wires, or if the enclosure has a speaker input you can do it off of that. report back with that number!

 

[Curtis Laudenslayer]

Most subs of decent construction will take the power for short times without any issues, I mean, you do not want to test with a 20 dollar speaker, so use some common sense.

If you have the ability to download test tones, try your current subwoofer at lower volumes with a 20 - 25 HZ tone, this will get the sub moving the most if can at lower volumes and see if that does it.

Or, even better,
go to harbor freight and buy a 10 dollar volt meter, and test the resistance of the subwoofer. (put it on the omega symbol) and then report back what you get. Do not move the sub when you do this and make sure that there is no vibration getting to the speaker. You can do this off just the wires, or if the enclosure has a speaker input you can do it off of that. report back with that number!

Ill do that today and report back, thanks again

 

[Curtis Laudenslayer]

Alright i measured 2.2 on the resistance, the omega symbol.
(i had it on a stable flat surface and everything)

More info:
the bass boost dial on the amp has been set around 25-30%
and the stereo settings that i have been using have all been for no extra bass boost because i read that it could distort it and give less quality. So EQ was flat, bass boost was zero, and loudness was off.
the max volume on my headset was 60, i wouldnt blast past 45.
So i dont think i was pushing it too hard?
when the problem started to occur, the sub would cut out anywhere from 38-42 volume depending on the song.

i tried the test tones they were pretty quiet so the cutout volume was pretty high.
i didnt go past 55 volume cuz i was scared lol.

20hz the amp shut off at around 50 volume
30hz didnt shut off
40hz shut off at 48
50hz shut off at 54
60hz shut off at 47
above 60hz it didnt shut off.

prolly too much information but i hope this helps lol.

 

[Karadjgne]

Your sub is what's known as burnt. There are coils inside the magnet that react to the frequency and amplitude of the signal sent by the amp. The higher the amplitude (volume) the further the coils travel through the magnet, both up and down according to the frequency (Hz) in either a positive or negative manner. (Hz is a alternating current - AC). It's entirely possible that either due to distortion, physical shifting of the cone, over heating due to extended high amperage or damage through frequencies below the range capability of the sub etc, that one or more of the Rings on the outer coil has lost some of its protective coating. When this happens, (and it's usually on the uppermost coils, closest to the cone) no sound differences will be noticed until the sub receives high enough amperage to drive the cone deep enough to come into contact with the bare rings, creating a dead short, which travels back to the amp without the amperage and voltage resistance usually seen from the subs resistance.

All this means is the sub is burned, time to replace it.

 

[Curtis Laudenslayer]

Cool thanks, sounds like u know what ur talking about haha
plus i got the sub used, and ive had it for over 2 years.

So when i buy another sub, im looking for a 2 ohm correct?
because i measured 2.2 resistance on mine?

and 250 rms to match the amp
and same size to match the box which is 12 inch.

Then i should be able to swap out the subs from the box and plug and play relatively easily?

 

[mymutter]

yes, it should be very easy to swap out the sub. 2.2 ohms is reasonably. Probably a dual 4 ohm sub,

Make sure the replacement sub will work in the same enclosure. (most will) so if you are running a sealed 1.25 cubic foot box, make sure that's the recommended space for the new subwoofer (or if you have a ported box) to get the best performance out of it.

 

[Karadjgne]

I used to install car audio professionally, so yeah, I have a clue lol. There's a couple things to look for in a new sub. Quality, well that's a no brainer heh, also since you have a box already, look for a sub with close to matching stats. Every sub has different particulars, from cone stiffness, to resonant frequencies and these stats are what sets the box dimentions. A kicker solo basic sounds great in 1.25cu.ft, but crap out in 2.0cu.ft, where cerwin Vega is the opposite. Most importantly though, look for low end limitations. I've seen expensive 12's that wouldn't hit below 60Hz, and yet my old, cheap pioneer 12's would hit anything down to 18Hz. 50-60Hz is the 'slap in your face' bass frequency range and if the subs struggle with that, they really aren't worth the money unless used as fillers for an 18"

 

[Curtis Laudenslayer]

After a lot of thinking, i decided to upgrade my amp and sub
went with rockford 12 inch 600w rms ported sub with the enclosure to match
and rockford 750w rms monoblock amp. Both running at 1 ohm

$400 for both on amazon, im excited

im hoping my stock 105 amp alternator and 800 cranking amp battery can handle it?
cuz i will be running 1000w rms total it looks like. should be fine haha

 

[Karadjgne]

Looks good. I'd do a 'dead battery' test pretty soon. That's where you turn on the tunes at a decent volume with the car off and time how long it takes until the battery will no longer power the sub. That'll be well past the time needed to be able to crank your motor, so if you kill the battery in 1 hr, figure you have a safe limit of 1/2 hr before you need to worry about jumper cables.