What happens when an amp is not 2-ohm stable?

[CrArC]

This is a question out of curiosity since I'm getting an amp that can handle it anyway, but...

I have a set of twin 12" subs in a sealed cabinet that are wired in a 2-ohm configuration. Just switched from a single 12" sub at 4 ohms. The amp I'm running them off is a cheap eBay jobby (shoot me, I know) that has 6 channels and claims 1000w for the sub. No sign of "RMS" so I'd say "more like 50, pfft" except it HAS proven incredibly powerful and more than thrashes a 600w kenwood I was previously using to drive my bass.

So these new subs are happily tearing my car to shreds but if I REALLY crank it - and we're talking up to the head unit's limits - then on some bass hits (often of higher frequency) the amp will cut out. It's also getting a damn-sight hotter than it ever used to. I'm assuming this is indicative of an amp that can't really handle a 2-ohm load as I'm checking the car's voltage and thanks to a beefier battery it isn't dropping below about 12 volts. I know this amp will run down to nearly ten from past experience (and crapper batteries, haha).

What do you make of this? a monoblock is on the way to replace it since I never use 5 of the 6 channels (kenwood is dealing with the rest quite nicely) and this amp is mahoosive. Nothing has burst into flames yet, I will just keep it lower until the new amp arrives.

 

[Donut Boi]

could be cable? what size wire you running? might not be gettin the amps it needs i know lowering a amp down to 2ohm make it use alot more power (amps)

Tom

 

[CrArC]

Yeah I had considered that, as I'm running 10 gauge on a 60A fuse at the moment I took the car's electrical system voltage from the cigarette lighter socket; I could re-test across the terminals on the amp and see if it's any more accurate. Current is a little harder to measure as my multimeter came off eBay and it's not made for measuring such a mahoosive draw, haha. I find it odd it only does it on higher frequency bass hits (take it lower and it will go nuts) but I figure they are harder for the amp to produce and draw more juice.

 

[chaos]

as I'm running 10 gauge on a 60A fuse at the moment

Are you insane? That's 4awg territory. Sort it as a matter of urgency - that is a ticking bomb waiting to go off.

Take the power supply directly from the battery. The fag lighter wiring is designed to what you'd expect it to do - take the current that the lighter needs ONLY - not that plus a potential 60A!

 

[volxstu]

It sounds like your cheapo amp actually has some very good Automatic cutout facilities. It sounds like when you turn the HU to full volume then the signal that it is sending is Distorted or Clipping as they say. (This is where the Peaks and Troughs of the wave are cut short) Anyway the amp is protecting itself from being damaged by dirty beats.

 

[CrArC]

Are you insane? That's 4awg territory. Sort it as a matter of urgency - that is a ticking bomb waiting to go off.

Take the power supply directly from the battery. The fag lighter wiring is designed to what you'd expect it to do - take the current that the lighter needs ONLY - not that plus a potential 60A!

Sorry I wrote that out wrong; I'm not running the amp off the cigarette lighter!!! I meant I'm taking voltage measurements from the socket. the amps are all wired to the battery in the nice, normal, non-set-fire-to-your-car way.

 

[chaos]

Sorry I wrote that out wrong; I'm not running the amp off the cigarette lighter!!! I meant I'm taking voltage measurements from the socket. the amps are all wired to the battery in the nice, normal, non-set-fire-to-your-car way.

Good

Just sort out the wiring otherwise you could still set fire to the car.

 

[CrArC]

It sounds like your cheapo amp actually has some very good Automatic cutout facilities. It sounds like when you turn the HU to full volume then the signal that it is sending is Distorted or Clipping as they say. (This is where the Peaks and Troughs of the wave are cut short) Anyway the amp is protecting itself from being damaged by dirty beats.

Yeah have to give whoever designed it credit for bothering. I don't think it's a clipping/distortion from HU issue: bear in mind this amp was more than happy to run on the old sub as hard as I liked... and I wouldn't be able to put up with poor sound quality anyhow

 

[CrArC]

Good

Just sort out the wiring otherwise you could still set fire to the car.

Yeah I do want an excuse to make myself get better wires in there. I was under the impression though that 10awg was appropriate for up to 60A current draw? The amp is not drawing that much, I know that.

 

[volxstu]

Yeah have to give whoever designed it credit for bothering. I don't think it's a clipping/distortion from HU issue: bear in mind this amp was more than happy to run on the old sub as hard as I liked... and I wouldn't be able to put up with poor sound quality anyhow

Yes but i dont think that i have ever heard a HU that can go to full volume without any distortion whatsoever, they arent made to go as high as they can go. You should set your sound system to be at its optimum at about 2/3's of the HU volume.
I know that this shouldnt be a wiring problem as i have a very similar problem with the Components in my car as if i put the volume up too loud the tweeters cut out and im sure that this is due to the Gain or the Frequency filter being set wrong as i have put the bass up on the HU therfore the problem is within the HU but can be sorted by fine tuning the Amp. Havnt bothered to do anything about it tho because it only happens at extreme volumes and the whole system is being ripped out and starting again due to a change of plans.
Kicker 15" L7 Anyone:slayer:

 

[chaos]

Yeah I do want an excuse to make myself get better wires in there. I was under the impression though that 10awg was appropriate for up to 60A current draw? The amp is not drawing that much, I know that.

No, it's good for roughly a third of that, assuming a run of 4 - 5m

 

[Donut Boi]

10AWG is rated at 60amp but thats at peak so you dont wont to be running 60 amps threw it all the time, as it will get hot and may melt the plastic covering cousing it to short out and cause a fire . I would recommend a 40amp fuse for 10AWG. Thats about 200watt RMS Whic pulls around 30/35amp mark. So if you wont to go higher on the RMS your goin to need to get yourself some better wire. 4AWG is rated to about 150/160 amps so you could put about 1000watt of RMS threw it with a 150amp fuse

Rember This Is RMS not Peak So you may wont to go bigger on the wire size to cover the Peak

If This Helps You Give Me A Thanks

 

[chaos]

10AWG is rated at 60amp but thats at peak so you dont wont to be running 60 amps threw it all the time, as it will get hot and may melt the plastic covering cousing it to short out and cause a fire . I would recommend a 40amp fuse for 10AWG. Thats about 200watt RMS Whic pulls around 30/35amp mark. So if you wont to go higher on the RMS your goin to need to get yourself some better wire. 4AWG is rated to about 150/160 amps so you could put about 1000watt of RMS threw it with a 150amp fuse

Rember This Is RMS not Peak So you may wont to go bigger on the wire size to cover the Peak

If This Helps You Give Me A Thanks

No, no, no. Don't go off the wattages (RMS or otherwise) - go off what current the amp can draw. Yes they're related but looking at what current an amp can safely pull is the more accurate way of doing it (you have to take amp efficiency into account which you probably would have to estimate if you go by power). Of course the amp won't pull 'maximum' current with music, but a 10awg wire will burn if subjected to a 60A current for long enough. Don't forget, a 60A fuse doesn't blow just because it sees 60.1A.

Have a look at www.bcae1.com sections 14 and 16. Personally I would use slightly lower fuse ratings than what is suggested there to be safe. I also would never put more than 80A through a run of 4awg - I remember seeing a max fuse rating of 80A for a run of 4awg somewhere else on the net but I can't remember where.

If in doubt, double check. It's a lot cheaper than fixing a car with fire damage.

 

[Donut Boi]

No, no, no. Don't go off the wattages (RMS or otherwise) - go off what current the amp can draw. Yes they're related but looking at what current an amp can safely pull is the more accurate way of doing it (you have to take amp efficiency into account which you probably would have to estimate if you go by power). Of course the amp won't pull 'maximum' current with music, but a 10awg wire will burn if subjected to a 60A current for long enough. Don't forget, a 60A fuse doesn't blow just because it sees 60.1A.

Have a look at www.bcae1.com sections 14 and 16. Personally I would use slightly lower fuse ratings than what is suggested there to be safe. I also would never put more than 80A through a run of 4awg - I remember seeing a max fuse rating of 80A for a run of 4awg somewhere else on the net but I can't remember where.

If in doubt, double check. It's a lot cheaper than fixing a car with fire damage.

I was just going on general rule of tumb m8, as all amps have diffrent "safty" draw currents. I was just trying to give a general overview about the diffrent "Wattage" ("Current" ("Amps"))to cable sizeing etc

 

[chaos]

I was just going on general rule of tumb m8, as all amps have diffrent "safty" draw currents. I was just trying to give a general overview about the diffrent "Wattage" ("Current" ("Amps"))to cable sizeing etc

That's why you go off what current your amp can pull. However, it doesn't matter what current an amp can safely pull - it depends if the cable leading to that amp can take the current. You will run a serious risk of having a fire if you put a 60A fuse on a run of 10awg; there's a good chance that the cable insulation will melt before the fuse will blow. The fuse in a power wire is to protect that wire from burning.

 

[Donut Boi]

That's why you go off what current your amp can pull. However, it doesn't matter what current an amp can safely pull - it depends if the cable leading to that amp can take the current. You will run a serious risk of having a fire if you put a 60A fuse on a run of 10awg; there's a good chance that the cable insulation will melt before the fuse will blow. The fuse in a power wire is to protect that wire from burning.

well thats the idea of the post to work out what wire gage is needs for what amps, hence relating it to wattage, and saying what cable will take what amps (current) i was trying to help on what size cable is needed

 

[chaos]

well thats the idea of the post to work out what wire gage is needs for what amps, hence relating it to wattage, and saying what cable will take what amps (current) i was trying to help on what size cable is needed

Yes, I realise that . However, the apparent suggestion of putting 60A through a run of 10awg is just plain daft.

 

[Donut Boi]

Yes, I realise that . However, the apparent suggestion of putting 60A through a run of 10awg is just plain daft.

i did not suggest putting a 60Amp fuse in 10AWG i recommened a 40Amp read my post

 

[chaos]

i did not suggest putting a 60Amp fuse in 10AWG i recommened a 40Amp read my post

Hence why I used the word 'apparent'. After reading it over a couple of times I understood what you meant. However, someone else might get the wrong end of the stick.

40A is still too much for a run of 10awg. Personally I would only run half of that as a maximum.

 

[Donut Boi]

Hence why I used the word 'apparent'. After reading it over a couple of times I understood what you meant. However, someone else might get the wrong end of the stick.

40A is still too much for a run of 10awg. Personally I would only run half of that as a maximum.

sorry im dyslexic so i find it hard to put things into words, i understand this may make my posts harder to read but im sure if you took your time to read the post you can make sence of it