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4-Channel Amp Wired to 1 Sub Continually Overheats

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NeverPetABurningDog

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Hello friends.

My amp and sub setup in my trunk works well except that the amp overheats regularly. It's a 4-channel amp, so I have two options for wiring the sub: bridged and unbridged. When it's unbridged, it's weak but it doesn't overheat as much. When it's bridged it sounds awesome but overheats after a few minutes, depending on the temperature outside. At first I thought that the ground wasn't good enough, so I moved it to the one of the bolts on the rear strut tower and sanded down every surface until shiny metal. I also cut the ground wire down to 18" or less. It still overheats. Maybe I need a higher gauge wire? I went to this audio shop and this guy told me to try switching the sub from channels 1 and 2 bridged to channels 3 and 4 bridged. So I did. Not sure what it did. I also might need to tune the setup more accurately, but I don't know that that has much to do with overheating issues.

My car (95 Civic if you're wondering) came wired by the previous owner for a subwoofer. 4 gauge power wire from the battery to the trunk, 4 gauge ground, and a remote wire and RCA cables from the radio to the trunk. Power and ground are both OFC. Back in April, I got a used amp and a sub and put it in my trunk. I don't know much about audio/electrical, but I'll list what I know about my setup below:

The amp I got is a PlanetAudio 4-channel amp (I know it's meant for speakers, but it at least works for the sub and I got it for $50). Here it is.

The sub is a Pioneer. Don't know the model number, but the reading on the multimeter at the terminals tells me it's a 4-ohm sub. It's a single voice-coil subwoofer.

What I don't understand is what bridging does to the impedance of the circuit. From my understanding, you want to match the impedance as close as you possibly can. So, if my amp is 4 ohms, I want a 4 ohm speaker to match it. Does bridging channels 1 and 2 put the impedance at 2 ohms and make it unstable? Or does running the sub on 1 channel put it at 8 ohms and make it more stable? I don't quite understand. 

Another quick few things. I have no money, but I still appreciate advice like "get a new amp" or "get a fan to blow air on it" even though I won't be able to follow through with it until I pay for college. Advice concerning the wiring will be much more valuable to me.

Thanks for the help, guys.

Click to read more...
 
NeverPetABurningDog said:
Hello friends.

My amp and sub setup in my trunk works well except that the amp overheats regularly. It's a 4-channel amp, so I have two options for wiring the sub: bridged and unbridged. When it's unbridged, it's weak but it doesn't overheat as much. When it's bridged it sounds awesome but overheats after a few minutes, depending on the temperature outside. At first I thought that the ground wasn't good enough, so I moved it to the one of the bolts on the rear strut tower and sanded down every surface until shiny metal. I also cut the ground wire down to 18" or less. It still overheats. Maybe I need a higher gauge wire? I went to this audio shop and this guy told me to try switching the sub from channels 1 and 2 bridged to channels 3 and 4 bridged. So I did. Not sure what it did. I also might need to tune the setup more accurately, but I don't know that that has much to do with overheating issues.

My car (95 Civic if you're wondering) came wired by the previous owner for a subwoofer. 4 gauge power wire from the battery to the trunk, 4 gauge ground, and a remote wire and RCA cables from the radio to the trunk. Power and ground are both OFC. Back in April, I got a used amp and a sub and put it in my trunk. I don't know much about audio/electrical, but I'll list what I know about my setup below:

The amp I got is a PlanetAudio 4-channel amp (I know it's meant for speakers, but it at least works for the sub and I got it for $50). Here it is.

The sub is a Pioneer. Don't know the model number, but the reading on the multimeter at the terminals tells me it's a 4-ohm sub. It's a single voice-coil subwoofer.

What I don't understand is what bridging does to the impedance of the circuit. From my understanding, you want to match the impedance as close as you possibly can. So, if my amp is 4 ohms, I want a 4 ohm speaker to match it. Does bridging channels 1 and 2 put the impedance at 2 ohms and make it unstable? Or does running the sub on 1 channel put it at 8 ohms and make it more stable? I don't quite understand. 

Another quick few things. I have no money, but I still appreciate advice like "get a new amp" or "get a fan to blow air on it" even though I won't be able to follow through with it until I pay for college. Advice concerning the wiring will be much more valuable to me.

Thanks for the help, guys.
Click to expand...
Assuming you're only using 2 channels of the amp what you're doing should not be causing any significant problems.

Any standard 4 ch can be used with two channels bridged to power a 4 ohm sub.

So what's the problem?  My guess is that you simply have a low quality amp that's not responding well to being run at its minimum impedance.

The only other thing I can think of would be to make sure the amp has room to breathe.

 
n2audio said:
Assuming you're only using 2 channels of the amp what you're doing should not be causing any significant problems.

 Any standard 4 ch can be used with two channels bridged to power a 4 ohm sub.

So what's the problem?  My guess is that you simply have a low quality amp that's not responding well to being run at its minimum impedance.

 The only other thing I can think of would be to make sure the amp has room to breathe.
Click to expand...
The quality could be it. It's a PlanetAudio mosfet amp (I don't know what mosfet means or if PlanetAudio is high quality or not but there ya go).

The problem is that it goes into protect mode because it gets so hot. 

What does bridging/unbridging do to the impedance? I notice I have much less heat production when I don't bridge channels 1 and 2, and rather just put it to channel 1, though the sub is considerably weaker. Does the unbridging change the impedance of the sub or the amp so that the amp puts less power out?

As for breathing room, it's mounted on its side, so it should have room enough I believe. I'll attach a picture below.

UuxbHJ6ualdz9S2vQsxfqyJY-HCfj7lE9xOM2TV6MgrO1IAE6keQLf_qoW1CjEZYOJBNWzXvLQNnNV9a4EtNZgoUagzgCNu5TYaxbDueOkNmRIrj1W2kcmbxRaU5-JLZcrvK4sEZQohYm3pFTZNCj-XcS9HgaSKfxVONt1vfbo9_3_Snu_Qwwfz5S5kBYKwcM1cF4UMvbmeaDZP9Z29-5EDJCFw2Rz0xPXz-fpS5mM4GAxYNDD5S4ir8rO2Y-EoIn2rq_BIFtgUmgSM-G3RKp0cG0XAVWtgRy7mYnHy1uKEO9vJWhKKWuLOlJQpbnkII-BnMgY81pi5zFFy_gF9GVdf4KyBmm7YtQYoNHRHJK8VRYwpjHkCBwqxiNLR98w9FvALl3k8AZoUPC7cURPlJJW2COnMH1TkJNo4fHSpCdNNUZRdtMlENmzk5xm8DfBcmY_Bd9gdyKSG8Qap8qel2T288MnOgnT22ZTnvvedUIV0BY3mLRLPUIj8t3Whj8icPgs0139sJL8HKhWSjMkJuPtGW9oCQa8nP5H9n9ArHRUPPWQMP8aDLJu5EohYbdV3isYxhQI1ZNSeIiSo1YZlpieTPMKIzV1NSSRgz0UrwyHjA9oINry0tdkUjyLyCBGI=w1774-h1064-no


 
Last edited by a moderator:
I personally wouldn't bridge a 4 channel amp to run on a sub. You're just overworking that $50 amp. You need more clean power my friend. There's so many options out there these days in getting a decent mono block amp for super cheap, take advantage of it. I know you don't wanna hear this but I predict that 4 channel will not last very long in this condition. You're wired at 4 ohm with very little power, I mean come on.. you can't really expect much from that. Your wiring is fine. 4 gauge OFC should be more than plenty.

 
blazian87 said:
I know you don't wanna hear this but I predict that 4 channel will not last very long in this condition.
Click to expand...
Nah man, I appreciate the help. It's better to hear it now than to destroy it without knowing anything. Many questions:

blazian87 said:
You're just overworking that $50 amp.
Click to expand...
Could you elaborate on what you mean by 'overworking?'

blazian87 said:
I personally wouldn't bridge a 4 channel amp to run on a sub.
Click to expand...
Why wouldn't you personally use a 4 channel amp for a sub?

blazian87 said:
You need more clean power my friend.
Click to expand...
And what do you mean 'clean power?'

blazian87 said:
You're wired at 4 ohm with very little power, I mean come on.. you can't really expect much from that.
Click to expand...
What do you mean too little power? You said my wires were fine, what else can I do?

blazian87 said:
There's so many options out there these days in getting a decent mono block amp for super cheap, take advantage of it.
Click to expand...
 Also where is it that I can look for a mono block amp for cheap?

Sorry for so many questions, I don't really know anything in the grand scheme of aftermarket car audio. Or anything for that matter. I'm generally curious about all this stuff.

Again, I appreciate the help. I would just be helplessly frustrated without guys like you.

 
NeverPetABurningDog said:
Nah man, I appreciate the help. It's better to hear it now than to destroy it without knowing anything. Many questions:

Could you elaborate on what you mean by 'overworking?'

Why wouldn't you personally use a 4 channel amp for a sub?

And what do you mean 'clean power?'

What do you mean too little power? You said my wires were fine, what else can I do?

 Also where is it that I can look for a mono block amp for cheap?

Sorry for so many questions, I don't really know anything in the grand scheme of aftermarket car audio. Or anything for that matter. I'm generally curious about all this stuff.

Again, I appreciate the help. I would just be helplessly frustrated without guys like you.
Click to expand...
I'll try to answer the best I can. You already know a 4 ch amp is meant for speakers so it just doesn't make sense to use it for sub duties. The main reason this doesn't work is because of the lack of wattage that's going into your speaker. Planet audio is known to be a cheap brand that likely does less than rated. There's nothing wrong with cheap budget amps but the fact that this amp is rated at 50w x 4 @ 4ohms, so can you guess how much that translates to in the real world? With a single voice coil 4 ohm, you're pretty much stuck with 4 ohm load. When the speaker actually plays music, the impedance will rise higher than that and likely only end up being about half the power you think it is. When you bridge 2 channels together, you're basically opening up all pathways to allow both channels to work as one big voltage rail. You might think it's a good idea because it effectively doubles your power. The downside is that this creates way more heat and if your gains are set too high, it can eventually cause it to fail over time from excess heat. This is very inefficient because the other 2 channels are being unused which is a complete waste. So on paper you have 1 channel giving you 50w and bridging it with channel 2 will give you 100w. Either way you're still underpowering the sub. This is one of the easiest ways to blow your amp or sub or both. Whichever model pioneer you have, it would be happier with more headroom. Something like 500w or even a 300w mono amp will already make a huge difference in output and clarity. You don't want to run an amp at full power at all times, this just creates excess heat and premature fail. The bigger amp you have, the less work it has to do for the same output. Check out bigblank69's youtube channel, he has a bunch of dyno amp tests on a bunch of popular budget amps. If you look around the classified section often or look on craigslist or online ads, you can sometimes find some hidden gems around. I helped a friend find a used oldschool DD audio 1200w @ 1 ohm for $80 locally from classified section on this site. Helped another friend find a used Boss audio amp I saw on bigblank69's dyno tests that did a legit 1300w @ 1 ohm for about $100 shipped on amazon. It's hard to find good power at 4 ohm for cheap so getting a dual 2 ohm sub is the most cost effective way to get more power for cheap.

So you said you had 4 gauge OFC for power and ground. That is more than good enough for anything up to 1200w so swapping them will make no difference in your case. Making your ground shorter will help with resistance but it won't make a difference in preventing your amp to protect.

Here's a simple analogy... It's kinda like having 4 glasses of milk half full vs 1 overflowing glass of milk while the other 3 glasses are sitting there doing nothing. Same concept with 2 overflowing and 2 empty glasses. Screw all that and get a tall glass with as much milk as you please and never let it overflow. Or like have you ever used a vacuum at home when running all your high powered electronics? or run your heater and computer simultaneously for a long period of time? This is pretty much what happens when your amp goes to protect.

 
Could be as simple as a gain problem on the amp. ie gain turned up too high. Try turning it down some and see how it does. Hows the amp get signal? Aftermarket radio or line out converter? If a line out converter, then the gain on it could be too high as well.

I have ran subs on 4ch amps many times. Usually doesnt pose a problem. When your broke, and only have 1 amp, gotta use it the best you can lol.

 
turn down the gain. if its not loud enough for you then too bad, thats what you are stuck with. If its overheating then its incorrect gain settings.  You shoulda gotten a cheap cca kit instead and sold that amp to buy a proper subwoofer amp with the money saved.

 
blazian87 said:
I'll try to answer the best I can. You already know a 4 ch amp is meant for speakers so it just doesn't make sense to use it for sub duties. The main reason this doesn't work is because of the lack of wattage that's going into your speaker. Planet audio is known to be a cheap brand that likely does less than rated. There's nothing wrong with cheap budget amps but the fact that this amp is rated at 50w x 4 @ 4ohms, so can you guess how much that translates to in the real world? With a single voice coil 4 ohm, you're pretty much stuck with 4 ohm load. When the speaker actually plays music, the impedance will rise higher than that and likely only end up being about half the power you think it is. When you bridge 2 channels together, you're basically opening up all pathways to allow both channels to work as one big voltage rail. You might think it's a good idea because it effectively doubles your power. The downside is that this creates way more heat and if your gains are set too high, it can eventually cause it to fail over time from excess heat. This is very inefficient because the other 2 channels are being unused which is a complete waste. So on paper you have 1 channel giving you 50w and bridging it with channel 2 will give you 100w. Either way you're still underpowering the sub. This is one of the easiest ways to blow your amp or sub or both. Whichever model pioneer you have, it would be happier with more headroom. Something like 500w or even a 300w mono amp will already make a huge difference in output and clarity. You don't want to run an amp at full power at all times, this just creates excess heat and premature fail. The bigger amp you have, the less work it has to do for the same output. Check out bigblank69's youtube channel, he has a bunch of dyno amp tests on a bunch of popular budget amps. If you look around the classified section often or look on craigslist or online ads, you can sometimes find some hidden gems around. I helped a friend find a used oldschool DD audio 1200w @ 1 ohm for $80 locally from classified section on this site. Helped another friend find a used Boss audio amp I saw on bigblank69's dyno tests that did a legit 1300w @ 1 ohm for about $100 shipped on amazon. It's hard to find good power at 4 ohm for cheap so getting a dual 2 ohm sub is the most cost effective way to get more power for cheap.

So you said you had 4 gauge OFC for power and ground. That is more than good enough for anything up to 1200w so swapping them will make no difference in your case. Making your ground shorter will help with resistance but it won't make a difference in preventing your amp to protect.

Here's a simple analogy... It's kinda like having 4 glasses of milk half full vs 1 overflowing glass of milk while the other 3 glasses are sitting there doing nothing. Same concept with 2 overflowing and 2 empty glasses. Screw all that and get a tall glass with as much milk as you please and never let it overflow. Or like have you ever used a vacuum at home when running all your high powered electronics? or run your heater and computer simultaneously for a long period of time? This is pretty much what happens when your amp goes to protect.
Click to expand...
My amp's actually at 100w, but your point totally still stands. Could you recommend some good amp brands for me? Also, is it easy to swap subs? Cause I have my sub box bolted into my trunk, so I'd like to keep it there if possible, but I know you can remove the sub from the box. I think what I'll do is keep the 4 channel amp for when (if) I upgrade my speakers and I'll find a cheap sub amp to mount on the other side of the trunk. Do you recommend a 1 channel or a 2 channel amp? And thanks again for all the advice.

 
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NeverPetABurningDog

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