What's the easiest way to set the delays for each sub? I think I can connect a mic directly up to the DCX (according to the manual) and have it automagically set the delays right? Or can REW do this as well... and should I use REW to do it instead?
I had some variability when I tried to use the DCX internal utility to set speaker delays so I have more confidence using REW measurements to set the delays in my system.
I see from JohnM’s comment that using the physical distance is pretty easy and reliable. If I am thinking correctly, a measurement error of 6" with an 80 Hz XO is only about 13° phase error so that is very good.
Some of us enjoy using REW to tune our system however so I will share how I set the delay up acoustically using REW.
I have 2 SWs at about 11' and 24' from the LP and. Instead of a 13' delay (per the physical measurements) I found a 14.9' delay using REW. The procedure was:
> Set the REW preferences for loopback timing reference.
> Measure each SW separately with the mic at the LP.
> Overlay the 2 IR’s and find the offset to the initial (or the largest) peaks.
> Set the delay of the closer SW per the offset and then re-measure it.
> The IR’s should now overlay closely, but one can zoom in and fine tune the timing if desired.
That setting should work well for those 2 SW positions (you can do additional SWs similarly).
Here are my 2 SW IR’s without any delay.
Here they with a 14.9’ delay on the closer speaker.
It is then tempting to then offset the final IR measurements by the same amount to place the 2 individual IRs near 0 ms. In that way the relative phase can be compared in the overlay window. In practice it can be difficult to interpret the phase correctly due to multipath interference, but with some experience it is possible. That discussion is beyond the scope here and is not really needed for good results.
With JohnM’s comment I just tried a 13’ delay per the physical distance and also got good results. I would not be able to clearly show in the measurements that one was better than the other. I just decided to stay with the original 14.9 ft delay as the IR overlay and the phase chart seemed to be slightly better and my physical distance measurements are a little questionable.
I don't think I want to take advantage of any of the EQ features of the DCX because I don't want to double EQ. Thoughts on that?
I have had issues trying to use Audyssey MultEQ XT on top of my REW / DCX EQ setup. In that case Audyssey usually applies a 9 dB boost around my normal cutoff frequency, but it does not always do it. Subsonic is not place where I want or need excessive boost! I believe this result may be very dependent on my particular setup, i.e., SWs, room acoustics, and mic positions. I sometimes obtained more reasonable results with XT however! Audyssey XT32 may be more reliable, but I have no experience with it.
My experience suggests that it may be better to use either Audyssey or manual EQ, but not run Audyssey on top of a Manual EQ. Others may have different experience, but I am much more confident using REW and manual EQ. Also, I can also experiment with different house curves and XO timing.