LR speaker hissing after sub install

[Jeff]

Hey all you stereo wizards out there...

I installed an OEM sub today (purchased off ebay for about $200 ), and now my left rear speaker (same side as the sub) hisses. It's a Boston Acoustics RX87 I installed last summer, and has been fine up to now. The right rear sounds fine. When I power up the head unit (Alpine CDA-7894) there's no hissing, but it ramps up after a couple of seconds, and is constant no matter what the volume (all the way down, balance all the way to the right, fader all the way to the front, etc.) or input (radio or disc.) Anyone have a thought as to what might be the cause? I can't tell, but does the sub ramp up in volume like that? Could it possibly be interference from the sub?

Thanks in advance for any input.

[GOLDMEMBER]

maybe a bad ground, not sure why its only affecting the left channel..

[GR8FLPT]

How is it wired, I belive the OEM sub uses the high level output form the stock radio & converts it internally in the amp in the box.
Where is box grounded? you may need to run a 2nd ground to back of radio. try disconnecting inputs to sub & see if it goes away.

If it does then there is a gnd difference between deck & sub amp. if noise is still there, then try a different power source like a battery thats not connected to your car. (I use a power supply), just had an install this weekend that was having wierd problems with the the stock electrical system. External power source can help toruble shooting faster.

[Jeff]

Originally posted by GOLDMEMBER
maybe a bad ground, not sure why its only affecting the left channel..

Thanks. That's what I'm thinking, too. I'll have to do some investigating.

[Jeff]

Originally posted by GR8FLPT
How is it wired, I belive the OEM sub uses the high level output form the stock radio & converts it internally in the amp in the box.
Where is box grounded? you may need to run a 2nd ground to back of radio. try disconnecting inputs to sub & see if it goes away.

If it does then there is a gnd difference between deck & sub amp. if noise is still there, then try a different power source like a battery thats not connected to your car. (I use a power supply), just had an install this weekend that was having wierd problems with the the stock electrical system. External power source can help toruble shooting faster.

I used the stock wiring and followed the directions completely (maybe that's my problem ) The unit is grounded at the back, behind the sub, and also to the back of the head unit (again, per instructions.) The ground wires are part of the loom that comes with the sub.

I like the second power supply idea. I'll try that in my troubleshooting. Thanks for the tip.

As for the sound, I'm really happy with the added oomph the sub provides. I may not win any contests with it, but I've got greatly improved sound, and I don't sacrifice any (well, not much) cargo space. I can fit my hockey back back there and still have great bass.

[GR8FLPT]

Your running an after market deck right? Are you running high level in or rca in? Try pulling deck out of dash & disconnecting gnd at deck, could be a gnd loop to where sub is gnded.

[Jeff]

Yes, I've got an Alpine deck. The sub is connected with the OEM wiring, which plugs into the stock connectors. I'll try disconnecting the deck-side ground, and see if that helps. Thanks.

[GR8FLPT]

Originally posted by Jeff
Yes, I've got an Alpine deck. The sub is connected with the OEM wiring, which plugs into the stock connectors. I'll try disconnecting the deck-side ground, and see if that helps. Thanks.

So then you are using deck power to the amp right? Maybe its a gnd issue between the deck & the amp. If you have an ohmeter, measure neg speaker output to chassis of deck. If it reads 0 ohms or close to it, its a common gnd deck. then due so on amp input wires. You might be able to get away with just using the positive wires from the alpine & gnding the amp signal to the deck chassis. But be very careful, you could fry one or the other or both if you hook it up wrong!
It would be easier for me if it was in front of me. Another problem is you could introduce engine noise.
Adding aftermarket to stock amplified systems has always been a pain in the a$$ as far as I can remember.

[Jeff]

So then you are using deck power to the amp right?

Well, no. There's a seperate power wire (with an inline fuse) that comes from the loom and is spliced into the hot lead of the cig. lighter (blue-black wire, according to the instructions). I think that powers the sub's amp. There's a remote power-on wire in the connector, too. That gets its power from the "Remote" wire of the Alpine, although I had to share it with my other remote amp (a Kenwood which drives the front speakers only.)

I'm GR8FL for your attention to my problem. I can understand what you mean by

It would be easier for me if it was in front of me.

I'm going to try some isolating tomorrow or the next day to see what I can find. I'll let you know. But for now, forget about it. Relax, have a Bud!!

Thanks again.

[Jeff]

Well, I finally found the time (after lots of real work, then a Disney World vacation) today to check into things. I traced the hiss to the aftermarket connector used to connect the aftermarket head unit to the sub wiring harness. I moved the left rear + wire a little and the hissing stopped. Moved it back, the hissing started again. So I taped the wires in a position where they all work, and put everything back. It sounds good now, so I'll monitor it for a while and see what happens.

Thanks all for your help! PTE is the best!