Feedback through speakers from amp.

[jazza15]

I bought a Powervox 2800W 4ch amp off ebay to replace my 400 or so watt one as it was buggered.
I have a 500w 12" sub and previously had 2x 160w 6x9's.
The amp is meant to put out 700w per channel. This is all in peak wattage.
So i had the sub on one channel and the 2 6x9's on another and I was getting feedback through the 6x9's. It was a sort of buzzing sound that increases with RPM.
When I had the sub hooked up by its self (because the noise through the 6x9's was too annoying) there was still some buzzing/feedback. I don't know if it still comes through the subs when the 6x9's are hooked up, but it probably does.
I tried multiple configurations (6x9's across 1 or 2 channels and with the sub channel - worse).
I just got a pair of 300w sony 6x9's and hooked them up this morning and it may have dulled it down a bit, but it is still there.
I have tried turing the gain down, but the problem is still there, just quieter because the speaker volume is quieter.
My latest idea is to look at speaker wiring, otherwise I may be looking at getting a less powerful amp?

[HCVP]

Well first off the way you've said you've wired it is a little confusing.

You say you had the sub running of one channel? If your running it off one channel, then presumably you would be getting either the left or right signal only. You need to bridge 2 of the channels together, to form one single channel, to drive the sub.
Next, i would assume because you haven't mentioned any tuning other than gain adjustments, that your sub will be running on full pass, as would the 6x9's, so you would be getting unwanted sound frequencies coming from your sub.
The power of the amp has nothing at all to do with it, in fact without going into detail, it's impossible to have too much power, so it's not a case of the amps power output as questioned in the last sentence.

I would have to do some research on that amp in particular and find out what HPF/LPF options it has, and if infact it can be bridged across 2 channels, at which point if you haven't had any luck, i could do up some type of diagram for you on how you should have it wired up, and you could go from there.

If everything is wired up correctly, it could be a simple case of some noise interference, which we could look at, but first let's get the wiring side sorted out, and make sure it's all correct.

[HCVP]

Ok, after a quick search, it seems that your amp does not offer any selectable High, or Low pass filter options.
Also from what i can see, it can only be bridged to run in 2 channel mode, so you are unable to run both a set of speakers, and a sub from this amp.

So from what i can see you only have one option, and that is to either run 4 individual speakers from the amp, i.e 2 front, and 2 rear, or bridge the amp to 2 channel configuration and use it to power a single set of speakers.(yes i know that is 2 options)
Your sub will have to be powered of a seperate amp, preferably a mono block.
Are you running an aftermarket head unit, if so, what type, model ect?

[jazza15]

Not really keen on hooking up another amp, even though i still have my old one lying around.
Would adjusting the bass setting possibly help this as it could act like a LPF/HPF? - bit of a long shot there.
It's good to hear that the amp can't be too powerful for the speakers.
And i'm assuming you mean that the sub needs to be bridged across 2 channels, ie 3 & 4 for it to function properly.

[HCVP]

If you look at the RMS power, rather than the peak power, you'll see that the amp itself is infact underpowered, even for basic duties.70 watts rms per channel (feel free to take a bit off that number) is most likely less than what your 6x9's would have been rated for input anyway.

Yes how how you explained the bridging procedure for the sub wiring is correct, but i wouldn't reccomend trying that with the current amp you have.

No, adjusting your treble, or bass settings, will not help the situation.A low pass filter is required to cut frequencies off above a certain point from being sent through to your sub.As it now, however you have connected it, it is acting as a full range speaker, playing all the frequencies, rather than just the bass as it was intended.

An additional amp is required to run your sub, there are no easy or cheap way's around it.Unless, what is your other amp you said you have lying around?

To save yourself this sort of trouble in the future, post up any questions you may have, and there are many people on here that can help you out with the right advice.

[D3CID3R]

So i had the sub on one channel and the 2 6x9's on another and I was getting feedback through the 6x9's. It was a sort of buzzing sound that increases with RPM.

Grab a bit of wire and run it from the shield of the RCA Input ( the outer part of the female RCA connector) and the put the plug back in, then run the other end to the wire to the ground of the amp

In saying this, im assuming you ran the power for the amp and the signal cabling down the same side of the car.. which is kind of a no no

Hope I could Help
D3CID3R

[jazza15]

In saying this, im assuming you ran the power for the amp and the signal cabling down the same side of the car.. which is kind of a no no

I didn't instal the original amp. But surprisingly, no. it was done correctly, with power and RCA on seperate sides of the car.

My old amp sitting around is a Power acoustik PA-400 amp, with channel 3&4 cutting out, which is why i 'upgraded'.

So I have definetely learned my lesson about Peak and RMS Music Power. I thought it was just like voltage in electronics, where RMS is proportionate to Peak, just divide by sqrt(2). It has to do with the resistance of the speaker as well in car audio doesn't it?

Anyway, i found this crossover to use as a LPF. Would it work as a much more practical (meaning I don't have to run 2 amps) and cost effective solution? http://cgi.ebay.com.au/NEW-SUBWOOFER...item563aac1997
Also the sub is 500w Peak i think, so would the maximum RMS output be sufficient for the sub? so I won't be losing out on power?

[HCVP]

That crossover has a fixed point of 120hz, which is a bit high, ideally you would wanting something around 80 hz. I couldn't say whether adding a passive crossover between the sub and amp would work, however i would assume it would.For the price it could be worth a try.

You still have the problem though of the amp not being suitable for what you are wanting to do with it, which is running both a set of speakers, and your sub.It's just not made for that.

[jazza15]

You still have the problem though of the amp not being suitable for what you are wanting to do with it, which is running both a set of speakers, and your sub.It's just not made for that.

I'm not fully understanding what you mean by that.
is that power wise?
Also, say i decide to not use the sub, did you say that i could bridge the 6x9's across 1&2 and 3&4 per speaker. the 300w sony's.

I was just thinking, if i keep the sub, I could just screw the old amp to the box. Could I just hook the amp up in series with my other amp?
That doesn't sound like too bad of a system then.

[HCVP]

The amp in question is not suitable because it is a 4 channel amp, which does not have the capability, unlike some others, to bridge 2 channel's to form one, to drive a sub.
For a 4 channel amp to be able to do this, it must also have selectable high and low pass filters, so that you can ensure that the sub, and the full range speakers, recieve only the correct frequencies.

You would need to refer to the owner's manual about bridging the amp to 2 channel mode, to drive a single pair of speakers.From the pictures i've seen on this amp, there are no markings of any type, to indicate which channels must be bridged.

[jazza15]

So going back to what I suggested earlier, that crossover would fix the problem (despite 120 being a bit higher than 50 -80hz)?
The ad says that it is bridgable (across 1&2 and 3&4) as these channels are controlled together respectively.

Had a look at the manual and it is pretty useless. Don't think it is even for my specific model.

Otherwise, if that doesn't work and I bridge the 6x9's on the new amp, can I hook my old amp up in series with my new amp?
And what would I do about the RCA's because then I have run out of ports!

[HCVP]

I've had a close look at the pictures of the amp you have, and there are no markings on the speaker output terminals to indicate that it can be bridged.It also only states a bridged power output in 2 channel mode.

What you are trying to do with this amp, is like trying to put a CD into a tape deck, it's not going to happen.

If you do not have enough pre-out's for you RCA's, then you will need to use RCA splitters.

You have two 4 channel amplifiers, none of which are designed to run a subwoofer, let alone a subwoofer and a set of speakers.Unless your other amp is capable of bridging 2 of it's channels to form a single (mono) channel, then there is no way you are going to achieve the outcome you are after.

You need the right amp for the right situation.

[jazza15]

ok so i gather from what you are saying that the new amp is not going to run the sub properly, even with that crossover thing from ebay. it would be like cutting the cd to fit into the tape deck, it's still not a tape.
my old amp has the high/full/low filter switch for 1&2 and 3&4, so does that mean it can run a sub from it? using splitters for the rca's which i will no doubt need help with later down the track if it can be done.
thanks for your help so far, things are starting to make much more sense.
I'm gunna d/c the sub tomorrow, don't think i have tried that combination yet!

[detox_nath83]

you are picking up some interference(Noise) from somewhere and as u stated buzzing increases with RPM its your alternator causing it....
or u have a lead crossing over a power lead somewhere and it is picking up interference and putting it to the speakers.
u can either install a noise surpressor on the alternator and getting a better earth for the amp... i had this when i changed over amps when i blew one... so i installed a noise surpressor on the alternator and the noise dissapeared...(Basically it is a capacitor one lead goes to 12v at alternator and the other is earthed..... look in to interference/noise surpressors for a better understanding or Click Here
Goodluck

[HCVP]

ok so i gather from what you are saying that the new amp is not going to run the sub properly, even with that crossover thing from ebay. it would be like cutting the cd to fit into the tape deck, it's still not a tape.
my old amp has the high/full/low filter switch for 1&2 and 3&4, so does that mean it can run a sub from it? using splitters for the rca's which i will no doubt need help with later down the track if it can be done.
thanks for your help so far, things are starting to make much more sense.
I'm gunna d/c the sub tomorrow, don't think i have tried that combination yet!

Yes, as you will see with your other amp, you can bridge to of the channels, and switch on the low pass filter, this will eliminate any high frequencies from going to the sub.Connect your sub to this amp, and you 6x9's to the other amp.You will have 2 channels being not used, which you could use to amplify another set of speakers, such as your front speakers, or rear, depending on which set you choose to connect to your other amp.(Allthough you did say that 2 of the channels on the amp were playing up? if so then use the 2 good ones)

[jazza15]

ok and could i bridge the 6x9's on the new amp yeah?
As for the interference, it is there even when i turn the volume all the way down to zero. the buzzing is there even without sound.
I noticed that the 6x9 speaker wires are tied to the power cord, but the buzzing also comes through the sub.
Could the RCA's cause it as well, or should I just be heading straight into noise suppression/proper grounding?

[detox_nath83]

yeah.. if u can still hear it when the speakers are turned down (no noise) and it is still getting a signal from the interference the buzzing etc your have... it is picking up the alternator. so it could be audio leads crossing power leads, well any 12 volt source in the looms etc..
alternator whine is caused by a ground loop...so isolating the noise from alternator will stop your troubles
it could be your RCA's being say if they are cheap ones and are not shielded properly would pick up interference
i would make sure u have propper grounding and look into installing noise suppression as well bud.... check this out ---------->http://www.termpro.com/articles/noise.html
goodluck man

[HCVP]

Have you been playing around plugging, and unplugging things while the stereo is on? You have have blown an RCA fuse within the head unit.

[Tasmaniak]

I bought a Powervox 2800W 4ch amp off ebay to replace my 400 or so watt one as it was buggered.
I have a 500w 12" sub and previously had 2x 160w 6x9's.
The amp is meant to put out 700w per channel. This is all in peak wattage.
So i had the sub on one channel and the 2 6x9's on another and I was getting feedback through the 6x9's. It was a sort of buzzing sound that increases with RPM.
When I had the sub hooked up by its self (because the noise through the 6x9's was too annoying) there was still some buzzing/feedback. I don't know if it still comes through the subs when the 6x9's are hooked up, but it probably does.
I tried multiple configurations (6x9's across 1 or 2 channels and with the sub channel - worse).
I just got a pair of 300w sony 6x9's and hooked them up this morning and it may have dulled it down a bit, but it is still there.
I have tried turing the gain down, but the problem is still there, just quieter because the speaker volume is quieter.
My latest idea is to look at speaker wiring, otherwise I may be looking at getting a less powerful amp?

Hmm

I bought a Powervox 2800W 4ch amp off ebay to replace my 400 or so watt one as it was buggered.
I have a 500w 12" sub and previously had 2x 160w 6x9's.
The amp is meant to put out 700w per channel. This is all in peak wattage.
So i had the sub on one channel and the 2 6x9's on another and I was getting feedback through the 6x9's. It was a sort of buzzing sound that increases with RPM.
When I had the sub hooked up by its self (because the noise through the 6x9's was too annoying) there was still some buzzing/feedback. I don't know if it still comes through the subs when the 6x9's are hooked up, but it probably does.

I bought a Powervox 2800W 4ch amp off ebay to replace my 400 or so watt one as it was buggered.

Almost

I bought a Powervox 2800W 4ch amp off ebay

Powervox

Jackpot. Problem solved. Sorry mate.

[jazza15]

lol, you put a bit of effort into that one tasmaniak.
I don't think i have blown any RCA fuses as it was like that when i first turned it on/used it.
The power supply/rca leads are the same ones that i had on my previous amp, so there shouldn't be anything wrong with that aspect, having said that "Powervox" is a different amp that reacts differently to my old one.
So i guess i should be chcking ymearth, i think it was a pretty thin wire, bolted to the body under the seat, not the best earth, but i guess it previously did the job.

[D3CID3R]

sand off some paint around the bolt just to rule out the earth

[D3CID3R]

Car Stereo Noise problem, Pls Help

[jazza15]

sand off some paint around the bolt just to rule out the earth

Scratched the paint off well around the earth, hasn't really improved it. the earth is under the back rest on the back seat just above the wheel arch. I noticed that through the wholes for the bolts that hold the back rest on is under the car, so is my next step to drill a whole for the earth to bolt to the rear cradle, or would a better earth not completely fix the actual problem?
I also tried disconnecting the RCA's for the sub, which did not stop the buzzing through the 6x9's.

What next?

[HCVP]

What type of aftermarket head unit are you using?

How long is your earth wire, and what gauge is it?

A quick and easy way to find out if it's the amps fault, would be to briiefly connect another one, and see if the problem persist's.If it dosen't then it's just your amp.

There's a reason why you can buy a brand new 4 channel amp with 16,000 jiggawatts for 70 bucks.

[jazza15]

Pioneer head unit. On a side note, why can you adjust the hz for the sub from the headunit. i can choose from 50, 80 and i think 100hz for the sub. How does that work?
The earth wire is the same guage as the power wire - thick.
Amp is defs at fault, never had this problem with my old amp, just unplugged old amp and unscrewed it, screwed in new amp and plugged it in just the same way. Was hoping that because it had so many jiggawatts of power that i'd have to do something differently, which is why I originally though that the speakers were just underpowered for the imense power from this beast of a thing lol.
The warranty is 90 days on the thing, I think I may be just inside of that so hopefully I can get my money back for it... or an exhange?