Speaker (-) signal question

**moahdib** · 10-17-2004, 07:56 AM

This may sound like a dumb question...
I recently got the starlogic 5.1 usb sound card and while checking out the connections etc, I noticed that all the negative signal for front, rear, sub and center are all the same. i.e. they are from one continuous output.

I don't know THAT much about speakers but I thought each speaker ground should be independently connected to divide the audio respectively into 5.1 channels.

Any experts out there?

**rickyaswell** · 10-17-2004, 08:45 AM

I think you will find that they share the - but the positive are different thats why a stereo plug has only 3 connections 2 + for each channel 1 - they share.
Make sure you wire your speakers the same way around, even if you swap the + - around it will still work but will not sound as good as your speakers wont be working in sync.

**Nic** · 10-17-2004, 10:52 AM

Originally Posted by rickyaswell

I think you will find that they share the - but the positive are different thats why a stereo plug has only 3 connections 2 + for each channel 1 - they share.
Make sure you wire your speakers the same way around, even if you swap the + - around it will still work but will not sound as good as your speakers wont be working in sync.

correct...

**moahdib** · 10-17-2004, 05:17 PM

hmm so on a regular car audio headunit all speakers share the same negative signal??
how about amps? Doesn't make sense to me why they get separated for each speaker...probably for insulation from noise?

**Gifted1** · 10-17-2004, 05:28 PM

That’s right... internally; all amps generally share a common ground. Normally there is a positive and a negative per channel for ease of installation. The consequence of wiring a speaker opposite of the other speaker on that channel would be that the signals would be 180 degrees out of phase with each other. The resultant sound degradation would vary depending on the particular passage of music, and on speaker placement.

**Jailer** · 10-17-2004, 07:39 PM

Originally Posted by Gifted1

That’s right... internally; all amps generally share a common ground.

Not necessarily, low power head units generally will be common ground, high power head units and amplifiers will almost always have separate negatives for the speakers (they may or may not be commoned inside the amp, but there will be separate connectors on the outside) due to each channel having it's own amplification. If it has separate grounds use them, wiring all the negatives of a high power amplifier together at best will result in the amplifier not working and at worst result in fried outputs on the amp. Now, that being said, if you only have one negative connection for the speakers don't worry about it, connect all the speaker negatives to it and it should work fine.

**moahdib** · 10-17-2004, 11:35 PM

My car stock radio which outputs 5.1 channel ( front, rear, center and sub) to the amp, doesn't have common negative signals on any of the channels.
I am trying to use relays to switch the audio from my PC and the car radio. The starlogic has common negative signal.

The signal coming out of the radio is low power, I checked the AC voltage and doesn't go past 1VAC at max volume.

I am already using 2x 4PDT relays, if i wire everything separate its gonna be another 4PDT. haha, thats a LOT of wires to connect...

Well if the amp takes all those - signals from the radio and makes them all common i shouldn't have a problem in combining all those signals into one connection on the relay.

**turbocad6** · 10-25-2004, 05:51 PM

NOTE: while all of the neg.s may be from one point source in the head unit/ sound card or whatever, DON'T make the mistake of thinking that they are the same as a normal ground! alot of the times these are a "floating" grounds & connecting them to a chassis ground will either damage the equiptment or at least create ground loops that will introduce noise into your system.... Also note that if you reversed ALL of the speaker wires at the same time, the end result would be exactly the same as if they were all correct, it only affects the sound when they aren't all wired the same, if you had two speakers & one had it's wires reversed it would put them "out of phase" with each other, (180 degrees)one speaker would be traveling in while the other travels out. the difference is barely noticable if at all in the upper freq.'s, but would affect the bass tremendously. to confirm whether a pair of speakers are "in phase" with each other you could simply reverse the leads to one of them, the bass will either be much better or much worse, obviously the more bass is the correct way & would mean that they are "in phase" with each other....

**Nic** · 10-25-2004, 10:20 PM

Originally Posted by Jailer

Not necessarily, low power head units generally will be common ground, high power head units and amplifiers will almost always have separate negatives for the speakers (they may or may not be commoned inside the amp, but there will be separate connectors on the outside) due to each channel having it's own amplification. If it has separate grounds use them, wiring all the negatives of a high power amplifier together at best will result in the amplifier not working and at worst result in fried outputs on the amp. Now, that being said, if you only have one negative connection for the speakers don't worry about it, connect all the speaker negatives to it and it should work fine.

what?