What size fuse to put on power cable

[serth]

Hi guys,

So I've been having a nightmare trying to sort out the sound system in my car. My basic setup is a Vibe Black Air b12 1800w sub with built in amp, with vibe black air 4s in both front and back standard speaker fittings. I have recently bought a (you guessed it!) Vibe Stereo 4 1200w Amp which is currently powering my speakers.

However, when I turn the volume up high, the Amp cuts out and the 'protected' light comes on. I was told it was something to do with the Earth? I currently have it earthed to the brake light earth (which works fine on my sub, on the other side). I have sanded off any paint to expose bare metal but this still didn't help. So I took out the back seat and put the earth to some bare metal, but this didn't do anything at all.

So I am beginning to think it is the power cable, or the lack of power. I had a 4awg fused cable running from the battery to a splitter in the boot, which then became 2 x 8awg cables, one for the sub's amp, and one for the speaker's amp.

By process of elimination, I'm guessing that not enough power can travel down these 8 awg cables when I crank the volume, resulting in the amp cutting out (although the sub has never cut out). So I have bought another 4awg cable to run the amp on its own (however, when i connect the 4awg power cable straight into the amp, it still cuts out at higher volumes).

My problem is that I don't know what size fuse to put on this new 4 awg cable to stop my amp from frying... I figured it was something to do with the power consumption of the amp but I'm not too sure.

Any help or other suggestions would be greatly appreciated... I've managed to blow the splitting terminal today resulting in just speakers or just sub, which isn't ideal.

Thanks in advance

Click to read more...

 

[Timmy13091 10+ year member]

Hi guys,
So I've been having a nightmare trying to sort out the sound system in my car. My basic setup is a Vibe Black Air b12 1800w sub with built in amp, with vibe black air 4s in both front and back standard speaker fittings. I have recently bought a (you guessed it!) Vibe Stereo 4 1200w Amp which is currently powering my speakers.

However, when I turn the volume up high, the Amp cuts out and the 'protected' light comes on. I was told it was something to do with the Earth? I currently have it earthed to the brake light earth (which works fine on my sub, on the other side). I have sanded off any paint to expose bare metal but this still didn't help. So I took out the back seat and put the earth to some bare metal, but this didn't do anything at all.

So I am beginning to think it is the power cable, or the lack of power. I had a 4awg fused cable running from the battery to a splitter in the boot, which then became 2 x 8awg cables, one for the sub's amp, and one for the speaker's amp.

By process of elimination, I'm guessing that not enough power can travel down these 8 awg cables when I crank the volume, resulting in the amp cutting out (although the sub has never cut out). So I have bought another 4awg cable to run the amp on its own (however, when i connect the 4awg power cable straight into the amp, it still cuts out at higher volumes).

My problem is that I don't know what size fuse to put on this new 4 awg cable to stop my amp from frying... I figured it was something to do with the power consumption of the amp but I'm not too sure.

Any help or other suggestions would be greatly appreciated... I've managed to blow the splitting terminal today resulting in just speakers or just sub, which isn't ideal.

Thanks in advance

Ground to frame!

 

[ace_800 5,000+ posts]

Well that Vibe Black Air b12 does 550rms and 8ga is good up to about 600-700rms without problems if its under 10', which yours probably is since your running 4ga until the splitter. You've probably got your gains on the built in amp up too high and you are clipping which makes the amp go into protect.

 

[serth]

Thanks guys for your replies

ace_800: The cable that i am running (the 4awg) is about 5m long (so around 16.5ft) and the 8 guage coming out of the splitter is only about 2 or 3 feet long so that shouldnt be a problem. I will adjust the gain later to see if that makes a difference. By clipping, i assume you mean cutting out? And are you talking about the sub's built in amp or the vibe amp?

The sub amp has a little control panel wired in from the front dashboard where i can adjust the gain/frequency, or did you mean adjust the gain on the speakers vibe amp?

The sub has never cut out, its always the speakers.

Timmy13091: i cant access any frame and i don't have a clue how to attach the cable to it!

 

[ace_800 5,000+ posts]

Thanks guys for your replies
ace_800: The cable that i am running (the 4awg) is about 5m long (so around 16.5ft) and the 8 guage coming out of the splitter is only about 2 or 3 feet long so that shouldnt be a problem. I will adjust the gain later to see if that makes a difference. By clipping, i assume you mean cutting out? And are you talking about the sub's built in amp or the vibe amp?

The sub amp has a little control panel wired in from the front dashboard where i can adjust the gain/frequency, or did you mean adjust the gain on the speakers vibe amp?

The sub has never cut out, its always the speakers.

Timmy13091: i cant access any frame and i don't have a clue how to attach the cable to it!

Yes the speakers cutting out. If the amp is going into protection then you are most likely clipping it. Turn the gains down on the amp that is cutting out. And if you can't get the the frame, then find a solid metal point that is connected to the body and/or frame of the car and selftap a screw into it for a ground.

 

[serth]

ace_800: You are a life saver! Why didn't i think of that before now! There i was prepared to spend a shed load of money on fixing it, thinking i'd blown the amp etc. Thank you very much man, much appreciated!

 

[Timmy13091 10+ year member]

ace_800: You are a life saver! Why didn't i think of that before now! There i was prepared to spend a shed load of money on fixing it, thinking i'd blown the amp etc. Thank you very much man, much appreciated!

Best bet would be under your rear seat and ya I always pay the ten bucks get my amp tuned at local shop no meter ... But whatever's clever but do those two things you'll be fine good luck

 

---------- Post added at 03:28 PM ---------- Previous post was at 03:28 PM ----------

 

At local shop because I have no meter...****