Comb Filtering?

Aahh....curse on you, COVID-19, makes everybody screw their everyday life.

8 to 5 now becomes 9 to 3, some are working from home.  With less people everywhere, less traffic in this notoriously horrible traffic city.

15:45 at home, well lots of time (and energy) for tweak.

After a few weeks with new 8 channels processor, CODIA DSP PROJECT 450.8 II , initial rough RTA-ing (1/3rd octave only) & on the road tweaking, it is time to check how much damage done to initial rough RTA/EQ setting.

And this time, with one week installed new TG9, 3.5" fullrange, in place of Wavecor 3.5"

Overall, not so bad after all, with 1/3 octave RTA.  It is time for more precision, starts with Left side (3way front stage).

Some rugged response in low & midrange frequency, wide hump in high 6-10K.  Surely tweaks here and there will smooth everything out. Piece of cake for 6-10K hump, small EQ-ing for midranges.

Around 300Hz.  Hmmm, interesting.  Looks okay with 1/3, but hey.... switching to 1/6 shows some dip and next to it a hump.

Switch to 1/12, then it is confirm OMG, is that comb filtering?  Very narrow and low dip, repeating itself with smaller and smaller increment throughout the RTA graph.

Flip the polarity of the TG9.  It is way way better response with flipped polarity in TG 9.  Also, no eardrum high pressure feeling.

Now this should be similar to Right side.  Nope. Response much much better WITHOUT TG9 polarity flip..... uh oh......

L & R both, TG9 pair only, with L flipped, R not flipped.... immediately shows destructive/lower SPL.  Reconfirm by un-flipping L.. yes... confirmed.  Un-flipped polarity on both L & R TG9 shows them in phase.

With my next to nothing tuning skills & experience, surely this will not rectify in a few minutes.  Tuning session will end soon for today.

DSP only have 0 and 180 phase,  don't have idea to correct it in the DSP, without screwing phase relationship among all speakers.

Last try before session end, is to move out XO freq from around 280 to 320. Nope, it is still there.  However, with 320Hz XO, seems less stress for TG9.

Closing time.... stop that pink noise, change for few familiar recording, quick channel gain match up & quick save.

Another further tweak in queue ......another fun in line.

As for you damn SARS-COV-2, Get LOST quick you creep! And why don't you pick something your own size, eh!

All hearts goes out to all medical professional heroes out there.....Take care & stay healthy.