Phase Reversal

[Martin]

I have an old 2 way BSS crossover (FDS-360) with balanced input XLR's wired pin1:Ground, pin2:Cold, pin3:Hot, and un-balanced outputs wired pin1&2:Ground, pin3:Hot

 

Now everything else in the system (mixer & amps) uses the usual balanced standard of pin1:Ground, pin2:Hot, pin3:Cold.

 

Will it make any difference if I just connect the crossover without swapping any pins, as the input will be in phase with the output. Or should I reverse pins2&3 on all connections to the unit?

[MarkPAman]

No.

If the ins & outs are wired the same, then it really makes no difference if you call it hot or cold. The signal will come out the same way as it went in. :)

[Rob_Beech]

Technically its polarity rather than phase which indicated a shift in time

 

/pedant

[Bobbsy]

Dang...Rob beat me to my morning pedantry about phase/polarity.

 

I've just one caveat to add to Mark's post. It makes no real difference if the old BSS is the only crossover/feed to speakers you're using. However, if you try to mix it with other systems feeding other speakers, the ones through the BSS will be moving with the opposite polarity which could be a problem, perhaps in the future.

 

Bob

[Ben Langfeld]

the ones through the BSS will be moving with the opposite polarity which could be a problem, perhaps in the future.

 

No, surely this would make no difference, as Mark said. If you think about the electronics, at the input, the signal is unbalanced, so the positive wave will be inverted and both waves summed, so you end up with the negative half being processed by the crossover, but then once it gets to the other end of the signal chain, it gets balanced again, and ends up the same regardless.

[Bobbsy]

According to the OP, the inputs are balanced and it's the output that's unbalanced. After the invert/sum process, the unbalanced signal would have to take its information for positive and negative motion (in the speaker drivers eventually) from the input...and since this (we assume) is coming from a conventionally wired XLR output, surely there would be a polarity inversion.

 

...or do I need more caffeine as I was up and packing hours earlier than I'm usually out of bed?

 

Bob

[Ben Langfeld]

Bobbsy, my apologies! Somehow I missed that the output was unbalanced. How odd. This must be old kit.

[mackerr]

I've just one caveat to add to Mark's post. It makes no real difference if the old BSS is the only crossover/feed to speakers you're using. However, if you try to mix it with other systems feeding other speakers, the ones through the BSS will be moving with the opposite polarity which could be a problem, perhaps in the future.

The output signal will be in polarity with the input signal in either case. It doesn't matter that within the electronics of the FDS-360 it might be backward. The real issue is that you have an unbalanced pin 3 hot output. As long as this is going into a balanced input you should have no problems. If however the output of the crossover is driving an unbalanced input there will be a polarity inversion, and you will need an adaptor .

 

Bobbsy, my apologies! Somehow I missed that the output was unbalanced. How odd. This must be old kit.

It's an FDS-360. That would be "old kit". :D

 

Mac

[jamesperrett]

According to the OP, the inputs are balanced and it's the output that's unbalanced. After the invert/sum process, the unbalanced signal would have to take its information for positive and negative motion (in the speaker drivers eventually) from the input...and since this (we assume) is coming from a conventionally wired XLR output, surely there would be a polarity inversion.

 

...or do I need more caffeine as I was up and packing hours earlier than I'm usually out of bed?

 

Bob

 

If you are sending the output of the crossover to a conventionally wired balanced piece of kit with a standard balanced cable then Mark's advice still holds true - the output should still have the same polarity as the input. You'll only get a polarity swap if you use a crossover cable on the output or feed an unbalanced input from the output.

 

Cheers

 

James.

[Martin]

Thanks for all your responses, that all makes sense now. I figured it wouldn't make a difference if everything was balanced, but the unbalanced outputs on the x-over confused the issue. Glad to know I don't need to make up phase polarity changer adaptors as the amps are indeed balanced inputs (wired the usual way). :D

 

Cheers,

 

Martin

[Bobbsy]

the amps are indeed balanced inputs (wired the usual way). :D

 

That indeed makes a difference (for the better) for you. Because of your mention of unbalanced outputs on the x-over I assumed your amps were unbalanced as well.

 

Bob