Reversing polarity in SDA's

nspindel

I'm about to get my modded Squeezebox 3 back from boldercable tomorrow. As part of the mod, they remove an op-amp from the analog path. In the stock Squeezebox, the signal is inverted as it passes through this opamp. As per boldercable, removing this opamp requires reversing the polarity of the speaker cables to get the correct phase. Would doing this cause any problems in my SDA 2B TL's?

hoosier21

yes, don't do it.

nspindel

Would you mind explaining your answer? Just wondering what the downside of doing this will be, as I need to find some way to change polarity.

Ricardo

SDA's need the negative posts connected to a common ground amp; if you reverse the polarity, you'll brake this, and you might even damage something. You'll make the positive posts "common".

No problem in having the phase inverted at the source. I had a preamp that did this and the manual said that the wires had to be inverted to the speakers. For my SDA's I didn't do it and sounded great. What's important is absolute phase.

engtaz

Smoked tweeter and/or frozen mids and for real good luck fried amp amondin.

engtaz

nspindel

Ok, I'll check it out, thanks.

Joe08867

If you reverse the polarity the drivers pull in for bass instead of push out. This will cause the drivers to bottom out and will more then likely damage if not kill them. Let alone tweeters that will go up in smoke and an SDA crossover that will S the bed in no time.

Clear enough!!

John in MA

He's talking about reversing the polarity to correct for the incoming signal's polarity already being reversed. The speakers, physically, would act normally. There's also nothing special about the crossover that would go bang.

The problem, and the reason you shouldn't reverse the polarity, is what Ricardo said. SDA speakers use the negative speaker terminals as the other conductor of the SDA cable's circuit. That's why you can't use them with floating-ground or bridged amps. If you reverse the speaker wires you’ll be tying the positive terminals together, and I doubt any amp would handle that very well.

If you need to reverse polarity, do it before the power amp. Make some interconnects with the connections swapped you can use with the Squeezebox.

Joe08867

That is why I said the crossover would go boom. It would be the fuse between the linked positive terminals.

It isn't a good idea.

nspindel

Yes, enough said, I'm definitely not going to be doing this between the amp and speakers. As Ricardo said, the two speakers are still in relative phase with each other, so I'm questioning whether there is any audible difference. I got the Squeezebox back yesterday - it still needs mega break-in, but sounds ok as is. I'll re-assess after a few hundred hours of break-in time.

Thanks for all the advice.