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DRPA+ inverse phase on all outputs
milpool29
Posts: 8
Hi guys. I haven't seen anything that addresses this issue on the forum yet. So thanks in advance for any advice.
My DRPA+ sends an inverse phase signal out of all 6 inputs. I know this because I used a Galaxy Cricket to check phase at all points in my signal chain. Phase is correct coming out of the boards (Mackie and Soundcraft), but reversed coming out of the DRPA+. That inverse phase continues through the snake, amps (Crowns and QSCs) and speakers (JBL 4732's and 4732A's).
The aux mixes (which obviously do not pass through the DRPA+) are all in correct phase, all the way out to the Yamaha monitors (via the same snake, and similar amps).
Since there is no phase flipping control on the DRPA+ (other than incremental delay changes)... what is the best way to address this?
I was hoping to just reverse pins 2 and 3 on the cables that connect the board to the DRPA+ inputs. But I am concerned that sending an inverse phase signal into the DRPA+ would create some weird processing issues. I'm also not convinced that it would even come out with the phase corrected.
I could reverse pins 2 and 3 on my out put cables. But I move this DRPA+ between a few different rigs, and that would require having a lot of reverse phase cables. And I would rather avoid that.
Any advise is eagerly welcomed! Thank you!
My DRPA+ sends an inverse phase signal out of all 6 inputs. I know this because I used a Galaxy Cricket to check phase at all points in my signal chain. Phase is correct coming out of the boards (Mackie and Soundcraft), but reversed coming out of the DRPA+. That inverse phase continues through the snake, amps (Crowns and QSCs) and speakers (JBL 4732's and 4732A's).
The aux mixes (which obviously do not pass through the DRPA+) are all in correct phase, all the way out to the Yamaha monitors (via the same snake, and similar amps).
Since there is no phase flipping control on the DRPA+ (other than incremental delay changes)... what is the best way to address this?
I was hoping to just reverse pins 2 and 3 on the cables that connect the board to the DRPA+ inputs. But I am concerned that sending an inverse phase signal into the DRPA+ would create some weird processing issues. I'm also not convinced that it would even come out with the phase corrected.
I could reverse pins 2 and 3 on my out put cables. But I move this DRPA+ between a few different rigs, and that would require having a lot of reverse phase cables. And I would rather avoid that.
Any advise is eagerly welcomed! Thank you!
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Do Crickets detect partial phase changes (say 5, 20, 40 degrees) and indicate as "OUT" of phase? The x-over slopes will alter phase (as I understand it). Set up an output with no filters applied ("Out to Out"), and see if the phase is corrected. Do you have access to another x-over of any kind? If it acts the same, that may be just the way it is.
As far as making phase reversing cables, make some 6" cables that stay with the DRPA+. They make pass thru barrels that reverse phase cheaper than you can build them.
DRA
PS - Report back your finding.
Other crossover types offer differing phase relationships that a phase checker ( + or - ) isn't going to be able to distinguish between, so it's going to default to one or the other. So absolute phase and polarity are not the same...especially where crossovers are concerned.
DRA
I will report my findings. Thank you!
While I do buy the possibility of certain filter combinations showing a negative reading on a polarity popper, I don't buy the likelihood of all six outputs inverted at the same time. I have a DR 260 and run a popper at every setup......I have never seen an inverted polarity reading that wasn't caused by a setting I made or a wiring mistake.
Thanks Dennis. Glad to hear that someone else has tried this. It seems odd to me too. I'm hoping to get the time for another measurement this weekend.
I don't think it is a wiring issue, unless it is an internal wiring issue on the DRPA+. I get the green light (in phase reading) on the output from the mixers, and from the cables that connect the mixers to the DRPA+. I've tried multiple XLR cables coming directly out of the DRPA+, and always get red lights.
You used the phrase "inverted", which to me suggests 180° out of phase. And that was my original assumption, and reason for posting here. Hence the questions about reversing pins 2 and 3. But someone else suggested that it may only be a few degrees out of phase... just enough to get a red light on the Cricket. I can't find any specs to know what the tolerance is on the Cricket. Maybe it only needs to be +/- 10° to display a red light? I don't know.
So this begs a question for you Dennis. When you get an inverted reading, and it is not a wiring mistake... what do you do to correct it? Adjust filters? Or adjust delays to compensate? Thanks!
The only issues I have are with wiring mistakes or accidently toggling the polarity switch (which I have in the DR 260).
If I run into one horn that is inverted in a system that has four horns, I will look for a wiring mistake. If I find all horns inverted, I will assume it is on purpose and will leave it as is.
Then I tested again, with a crossover, and all of the outputs appeared out of phase again. The signal was kinda low, so I decided to turn up the gain on the incoming polarity pop. Oddly... the HF and MF outs started reading in phase. ??? I don't know, maybe I needed to exceed a noise floor or something. I had previously been testing at a relatively low gain (just enough to show some signal lights on the DRPA+). But turning it up to make it read a modest -20db to -10db seemed to correct it. I guess I didn't expect the phase to be altered by dynamics. Does what happened make sense to anyone?
The LF outs, however, stayed out of phase no matter what the gain was. So I reversed pins 2 and 3 on the cables that go into the sub amps, and finally, the phase signal coming out of the LF outputs on the DRPA+ were corrected. And the subs were operating in phase too. Additionally, I put some kick drum through them, and verified that the cone was moving forward. I should note that I had previously verified correct polarity in the sub cabs. They passed an in phase signal when plugging the Cricket directly into them. They were only operating out of phase when receiving a signal from the DRPA+.
I understand that LF may sometimes benefit from a polarity inversion. But I don't necessarily feel comfortable with what I did. It sounds good, and measures correctly. I half expected to see a few db gain increase by making the inversion, but that was not the case. I'm hoping you guys can confirm what I am reporting, or at least give me a heads up. Thanks for following this thread. I am very grateful for your wisdom.
Randy
Hey Bob! I didn't see your post until after I composed my results reply. I look very forward to fiddling with the O-scope, and working on some time alignment settings with you.
I haven't had these issues with mids and highs but I have to turn up the subs for an accurate read and I don't think it is unusual to do so.
Flipping the polarity on the outputs is treating the symptom rather than the problem
I couldn't agree more. I'm just not sure how to correct the "problem". I measured the sub output at 103-104db while testing polarity. How loud should it be before I get an accurate reading? Thanks again! I'm glad that you have been through this before.
Yikes...........no where near 104dB. Maybe if your system was aligned with a program like SMAART using alignment delay that is supplied in the DRPA+, the polarity reading would reverse
Thanks to everyone who replied. All of your advice gave me good ideas to work with. I'll post results of any time alignment adjustments I make. But that may be a while. October/November is festival season in Southern Arizona, and my spare time is fleeting!