file Polarity switch?

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fcaprilli Posted 11 years 10 months ago
#136
Was calibrating my system using Avia...I notice the FF3 doesn't have a way to switch polarity. Presumably it's not deemed necessary - or am I missing something?

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Moderator Posted 11 years 10 months ago
#137
Thanks for your purchase, hope you're excited about the sub's performance.

No, you didn't miss anything, The ForceField subs do not have a polarity switch or phase control. We felt they were unnecessary given today's sophisticated a/v processors - plus the fact that in our experience phase switches and controls are a constant source of confusion, leading to mis-adjustment by the user.

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fcaprilli Posted 11 years 10 months ago
Last edit: 11 years 10 months ago by fcaprilli. info_outline
#138
Thanks. Yes, very happy with the system (got a whole 7.1 set of SS3s plus the FF3). (And my old system was - ahem - Bose - so you can imagine :)

I've now spent a few hours tweaking using the Avia disc and an SPL meter, making sure the levels are correct, speakers are in phase etc. Everything's fine except for one test - the "low frequency pink noise 5 channel pan" - which pans in a circle (L -> C -> R -> RS -> LS). This works fine except for my right surround - as it pans to that speaker, the sound disappears entirely. The onscreen description suggests that one could use the polarity switch on the sub to correct this. (Which is why I asked.)

I know it's not the speaker because I swapped it out with another one and the issue remains.

As I said, all the other tests involving that speaker are fine.

Can you think of any reason why this would be? I've triple checked the wires to make sure it's in phase. The sub is connected via the sub input on the A/V receiver (Harman Kardon AVR 354).

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Moderator Posted 11 years 10 months ago
#139
Thanks for the explanation. Make sure you take readings in multiple locations with your SPL meter to make sure the "problem" is not isolated to one listening position.

It sounds like you've done all the correct sleuthing, although you may want to also swap the LS and RS speaker leads at the receiver just to make sure that the Right Surround (RS) channel doesn't have a problem. Sub phase would not be the issue since all the other channels are OK (so presumable reversing phase would then cause all the other channels to have the problem).

Since it is only that one LOCATION (not speaker, because you swapped them to check this) the next best guess would be, as you mentioned, that the one speaker is wired out of phase (which you indicated it is not, per your checking). After that, all that's left is location, and it would not be unusual for a particular location to have a frequency cancellation not present in other locations. You can try moving that speaker around a bit, if possible. You can also use a room correction system that would address this dip.

But... if the system sounds great, that's all that really matters...

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fcaprilli Posted 11 years 9 months ago
#140
> But... if the system sounds great, that's all that really matters...

You'd think so, wouldn't you? :laugh:

I will try your suggestion - thanks.

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fcaprilli Posted 11 years 9 months ago
#160
So I took your suggestion and switched the wires for the left surround and right surround... and it didn't make a difference! The sound virtually disappears as it pans through the right surround.

Then I thought of something... by default, my HK AVR 354 receiver runs in something called Dolby Pro Logic IIx Movie mode when 7.1 is enabled. I think this takes a 5.1 signal and creates the 2 rear channels out of it.

The Avia disc only deals with 5.1. When I disabled the 2 rear channels, the strange behaviour disappeared.

I guess that means that there's some strange artifact introduced by whatever algorithm it uses to create the extra 2 channels from a 5.1 signal.

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