Rotel amp speaker output backwards????

[JimP]

I'm running a Rotel RMB1095 and RB991 in a 7.1 home theater configuration.

I was bored this afternoon and thought I'd check the wires going into my speakers to see what the voltage would read on a low impedance voltmeter.

To my surprise I found that the reading indicated that several, but not all of my speakers were wired where they should have been getting reverse polarity(hot side read negative). So the gears start turning in my head to try to figure this out. I have speaker wires going under carpet, through walls via junction boxes and I never felt all that comfortable in the way that speaker wire is marked. I use a heavy grade speaker wire from Radio shack. (o.k., you can stop laughing).

Then I though I'd check the polarity on the back of the amplifiers. Some read correct and some were reversed. Both on the RB991 were reversed and only a couple on the RB1095 were reversed while the others were o.k.

It would seem, if anything, they would all be one way or the other. Am I missing something or is it possible that they were wired wrong from the factory??

I've rewired the speakers such that the hot side would connect to the positive side of the speaker. I wish I could say that I hear a huge difference, but I don't. If anything, its slight and I'm not so sure that I haven't been fooling with it so much that I'm having a hard time telling what's imagined and what's real.

I'd appreciate one of our Rotel experts shedding light on this.


Jim

[sprout]

I believe there is an addendum to this on the Rotel site ops:

sprout

[sprout]

mmm the only one I can see quickly is for the 1080, which you do not have

http://www.rotel.com/support/pdfs/manuals/rb1080-addendum.pdf

bet you will have a few people busy now though :B

sprout

[sprout]

Main thing I would say is use a decent set up disc for checking phases.

If it were just stereo it would not matter as long as each speaker had the same going to it.

i.e It can have +/- reversed providing this is done on the second speaker.

HOWEVER

In multi channel setups it is vital!

You may say have two stereo pairs each as above, but wired opposite i.e one pair reversed, one pair not.
As just playing stereo each would be fine.
But when in multi, one pair will be moving forward while the other pair backwards. Out of phase :E

You also have phasing between all speakers as well of course, including the centre, rears, side rears & sub, depending on your setup

Cheers

sprout

[JimP]

Thanks for responding guys.

I think the Avia disk has a phase test for a 5.1 system. I also have the DVE disk, which may be 6.1. Does anyone know about a 7.1?? Or maybe change out the interconnects for the rear center channel (which is on the RB991) for the phase test.

We've got a hurricane heading this way (central Alabama, USA) so if you don't hear from me for a few days, its not that I've lost interest. Guess I'll be hugging the 1095 as it would make a good anchor. lol

[Marcel B]

The THX test on many DVD's (eg Star wars ep 1 and 2 ) contains a phase test for 7.

Marcel B

[RACER4551]

I have been wondering if my 1095 was wired incorrectly,because the other day i had a friend over and he has great hearing and said my left front speaker was out of phase.I thought he was nuts,so i put my avia disk in and went to the front speaker phase test and sure enough it was.He told me to swap the inputs on the speaker and rerun the phase test,i did and the phase is now correct.I just could not beleive it,i doubled checked all the wires just to make sure.Is it the amp or could it be the bi-wire speaker wire thats incorrect.The bi-wire is four connections at the speaker and two at the amp end.I suppose i could check it with a multi meter.Just has me wondering now.

[JimP]

Racer

It looks like my original conclusion was incorrect. Apparantly, you can't use a volt meter to check polarity on an amplifier's speaker output.

I went back and reran the phase test and the wiring at the amp is ok.

Regarding your biwire, I'd check with a ohm meter to see what goes where.

[lvhung]

Dear JIMP
Is there any difference between 991 & 1095 in sound quality ?

[bigburner]

Regarding the RB-1080 polarity issue, is the manual incorrect or is the amp labelled incorrectly?

[JimP]

Dear JIMP
Is there any difference between 991 & 1095 in sound quality ?

I believe that the 991 sounds slightly more musical than the 1095. The 1095 is no slouch, but for 2 channel stereo, I'd prefer the 991.

[rnoble]

Regarding the RB-1080 polarity issue, is the manual incorrect or is the amp labelled incorrectly?

I think this is a valid question bigburner, as the addendum appears to be in the manual section and not in the technical announcements/updates section. Which would suggest to me that it's just a print error however if one looks at the back panel drawing section its also drawn wrong. Can someone with a 1080 confirm the position of the terminals on their unit?