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Old 06-03-2014, 01:26 PM   #1
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Speaker wiring/common ground?

Looking at replacements for original 5.25 inch speakers in my 25ft 89 Excella, and speaker vendor says the trailer's common ground for speakers is not agreeable with newer speakers which are set up for individual grounding. If not rewired, the receiver will overheat and burn up he claims.
Anyone dealt with this, and if so, is there a simple solution?
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Old 06-03-2014, 04:50 PM   #2
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The original speakers use the trailer's electrical 12 volt ground? Only the positive speaker wire goes between the speaker and the source?

If you are just replacing the original speakers and keeping the original receiver (which was using the common trailer ground) I don't see how the receiver would know/care. A speaker is just resistance in the wire, usually 4-8 ohm.

If it was me and the receiver was original, I'd just replace the speakers and wait and see. You might consider posting in a stereo forum, see what they have to say. You could also consider asking a different vendor.
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Old 06-03-2014, 05:04 PM   #3
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Originally Posted by PAL07 View Post
Looking at replacements for original 5.25 inch speakers in my 25ft 89 Excella, and speaker vendor says the trailer's common ground for speakers is not agreeable with newer speakers which are set up for individual grounding. If not rewired, the receiver will overheat and burn up he claims.
Anyone dealt with this, and if so, is there a simple solution?
Speakers don't care, but a newer radio might. I've not seen a radio in a long time that will recommend the negative side of the speaker output be grounded. Not saying it won't work, but it might be a problem with a newer radio.
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Old 06-03-2014, 11:11 PM   #4
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The receiver was replaced two years ago, so I'm dealing with new unit. Now looking to replace original speakers, which apparently share common ground. How will the new receiver respond to commonly grounded speakers?
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Old 06-04-2014, 12:25 AM   #5
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I don't know the '89 excella system but on all of my old 60's and 70's Argosy's and Airstreams, the speakers each had two wires from them and were not common ground. Are you positive that the speaker wires are not a pair for each speaker?
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Old 06-04-2014, 02:45 AM   #6
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Quote:
Originally Posted by PAL07 View Post
... speaker vendor says the trailer's common ground for speakers is not agreeable with newer speakers which are set up for individual grounding. ...
There is no "individual grounding." Neither speaker wire is grounded. There is no connection to the 12V system, ground or otherwise.

Most solid-state (bet you haven't seen that phrase lately) audio amplifiers have floating speaker outputs. That means you have to have two ungrounded wires going separately to each speaker. There is no common connection between the speakers, eg, you can't use three wires for two speakers, like you would for stereo headphones.

All my 70s Airstreams have this method of wiring for the front and rear speakers (8 wires for 4 speakers). I would bet your '89 has the same.

If you ground one side of each speaker (like using the shell as a common ground) you will have connected the floating output of the left and right amplifiers together and they will burn out.

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Old 06-04-2014, 05:27 AM   #7
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I just finished changing out my sound system in a 1986 345 . The speaker wiring neg is the black wire . A good way to figure this out is take a AA battery , take and hook up the speaker wires to speaker , hold one wire to - side of battery the other to + side of battery , if the speaker pulls in the polarity is correct . That tech tip came form the tech form Best Buy . The sound system sounds great but there is a rattle on one side . The speakers mount on the bottom of cabinets and they have a false floor in them , cause of rattle . So going to try using some insulation there to stop rattle .
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Old 06-04-2014, 05:36 AM   #8
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The speaker ground wire goes to the amp-radio not the chassis ground.
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Old 06-05-2014, 07:55 AM   #9
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There is no "individual grounding." Neither speaker wire is grounded. There is no connection to the 12V system, ground or otherwise.

All my 70s Airstreams have this method of wiring for the front and rear speakers (8 wires for 4 speakers). I would bet your '89 has the same.

Zep
That's what I thought. I wonder why the OP's speaker vendor is assuming that his speakers share a common ground. I've always seen 2 wires per speaker and they always went back to the receiver. I've got some pretty old equipment here at the house and nothing shares a common ground.
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Old 06-05-2014, 09:03 AM   #10
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It think you have to go all the way back to when audio equipment had transformer outputs to find negative grounding on the speakers (think tube equipment).
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Old 06-05-2014, 09:21 AM   #11
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You need independent grounds due to the fact most modern head units use discreet MOSFET output devices.
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Old 06-05-2014, 11:21 PM   #12
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SteveH is correct. Back in the day you needed a transformer to keep the B+ voltage off the speaker wires. With solid state amplifiers, the collector voltage is low enough that you can drive the speakers directly, but the outputs (both the + and the -) are floating, eg, they are not connected to ground nor are they at ground potential.

It would be a good thing if we stopped using the term "ground" when what is really meant is "speaker minus." In the old days speaker minus (speaker -) was connected to common ground, but not any more.

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Old 06-05-2014, 11:29 PM   #13
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SteveH is correct. Back in the day you needed a transformer to keep the B+ voltage off the speaker wires. With solid state amplifiers, the collector voltage is low enough that you can drive the speakers directly, but the outputs (both the + and the -) are floating, eg, they are not connected to ground nor are they at ground potential.

It would be a good thing if we stopped using the term "ground" when what is really meant is "speaker minus." In the old days speaker minus (speaker -) was connected to common ground, but not any more.

Zep
Zep: Excellent comments, well stated, thank you
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