Re: Well, THAT's Not Gonna Fucking Work!
P.S. Smaart thinks the delay on both should be one sample more, i.e. 0.75msec, but I liked one sample less. In neither case does the HF phase flatten out as one would expect.
Just tested one of my DriveRackPa units out.
It inverts polarity for LF, MF, and HF from input to output, as with your interface, the phase line with a hard wire is basically flat, but in the case of the DRPA, all the outputs are about 180 degrees off.
Smaart AutoSM sets latency as 1.52ms for LF, 1.50ms for HF.
Latency in three way mode is 1.52ms for LF, MF, and 1.50ms HF.
The LF and MF traces look identical.
Smaart latency increments (.02ms) are not small enough to flatten the phase trace out, my M-Audio interface trace, the purple one that shows about -34 at 16K, flips to +120 when .02 is added as a delay.
Using the Mac in /out, no interface still resulted in a HF phase drift, though IIRC not quite as much as with the M-Audio. Andy (on the old LAB) verified that with a straight wire in/out with his Mac too.
The difference between the Low/Mid/High phase trace on the DRPA seem to be the result of a tiny delay range difference, unlike your DRPA +, which looks hosed.
This was a learning experience for me, I was unaware all the DRPA outputs were inverted, and I had never realized that the filters still affected phase even when switched “out”.
I don’t know what DBX did in the “+” version to (re) invert the HF (making it “sorta normal”), perhaps they threw in a few filter caps to eliminate the “shotgun” sound the DRPA made when power is lost when it is still in use, the funky HF phase response looks kind of like some (bad) passive filter.
That said, as Phil said “If the effect in the trace was a consequence of DC blocking capacitors, it would show up in the magnitude response”, and the magnitude response looks good. If they can't get the in/out polarity correct, who knows what else they can mess up.
As an aside, I had to invert the polarity on my HF drivers when I was using DC protection caps on the HF drivers in my system, when I eliminated them polarity went back to normal, and delay time matched the physical path length difference more closely.
Well, back to my electric boat project (using the Electric Paddle, more than 3 dB more efficient and faster than trolling motors) where I only have to worry about battery polarity, not phase...
Art
