DSP1124 altered my phase

1772 Views 9 Replies 6 Participants Last post by PoorSignal, Apr 1, 2010

PoorSignal

Discussion Starter · Mar 8, 2010

Hi guys, I did back to back test with a coupler to bypass the unit physically
I had a reasonbly good response with no null without the dsp1124 in the loop. (Sub + L R)
Same test, once I added the DSP there is a null around 85hz and it is sharp. (No filters)

I know this is a timing issue, and I adjusted the subwoofer distance by 1 feet further to compensate, but this didn't help, I even tried adding 2 ft, 2.5 ft, or no addition. The void is still there more or less. Moving the phase knob just moved the null spot

However, after I EQ'd my sub on its own, the graph with sub + L R does not have any nulls anymore. I probably took away my 55hz peak that caused the null together with the L, R. But as I said above, without the BFD I don't have that NULL.

So as long as the EQ'd result was OK, do you think everything is good? It just means I just can't run the unit in bypass mode unless I wanted to listen to a void.

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PoorSignal

Discussion Starter · #3 · Mar 8, 2010

The main reason I am using it is to implement a house curve. I also noticed the BFD gave the sub about couple DB more. It obviously changes the time the sub fires, so these factors alone might have caused the phase null.

Like I said everything looks good when integrated and EQ'd. Graph don't lie, right?

here is the final result

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PoorSignal

Discussion Starter · #6 · Mar 9, 2010

It sounds fine. But it just bugs me.

I tried turning the phase of the sub 180 but it didn't work to remove it, only change it.
Don't know if I reverse the phase at the receiver might work different.

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PoorSignal

Discussion Starter · #8 · Mar 9, 2010

OK I have done some more tests..
without the DSP1124, the null happens at phase 0
with the DSP1124, the null is at phase 180 (bypass mode), so it is indeed flipped around 180.

It would seem I should leave it at phase 0 then. However after equalizing I get no null only if I leave the knob at 180, so there it is. Once I leave 180 the null gets bigger and deeper.

So that is the final setting.

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PoorSignal

Discussion Starter · #10 · Apr 1, 2010

Well, I can't remember which way, but I think REW graphs has the final say, nulls are created by phase and timing in the wrong time so that they cancel each other. The DSP added some delay obviously so it changes something.

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