What could be causing this spike at 60Hz?

[JStewart]

So the new Umik-2 makes DLBC calculate bass levels differently, increasing them by 2dB compared to my old microphone

I agree, the subwoofer level of the Cal done with the UMIK-2 is approx 2dB higher.

The is what originally caught my attention:

So there's a few dB of headroom that's been lost on your fronts and other speakers. You mentioned you had moved a subwoofer, too. The set levels screen above is with the mic at the MLP and since Dirac sets levels based on the average of all measurements, it's possible that the average of the measurements would result in the levels being set as they have been, meaning the subs are not as loud as the fronts in the average vs. louder than the fronts as they are in the set levels screen. (The same could also explain the subs being 2dB louder) It just looks odd to me is all, because I'm having a hard time understanding how an average could result in the subs being approx 7dB quieter in the average of measurements than they are at the MLP. Looking at the individual position measurements for the subs on the Dirac measurements screen may tell you something if it matters to you. But I get that everything appears to be working properly and its probably not worth your time.

 

[FargateOne]

Things to consider:

1. Unplug the laptop from the AC power supply, run on battery
2. Be sure all your equipment is on one run back to the circuit box breaker
3. Temporally remove any power conditioner

Thanks those are best practices followed religiously. since 10 years with the old mic when a couple of weeks ago it give the spike at 60Hz all of a sudden. FTI the miniusb connection on the back of the old mic was on a round plat that we could turn out to open the internal hardware of the mic. The same round base of the umik-2 has now 3 little screws to assure nothing move when we connect the sub cable on the mic.

 

[FargateOne]

So there's a few dB of headroom that's been lost on your fronts and other speakers.

With Umik-1 I always had this 4dB headroom as shownd in #41 first image. I was thinking that I could have the same headroom with Umik-2 but where trims for the satellites and for the subs are reversed...by the same dBs.

You mentioned you had moved a subwoofer, too.

Yes but Umik-1 and Umik-2 results are for the new position of the left sub I spoke of so they are OK to make comparaison.
Before I moved the left sub, the 2 integrated well together with the same polarity.I moved the left sub by not more than 40cm forward. REW alignment tool showed that I needed to reverse the polarity of 1 sub to get thesame best integration I had befor the move. DLBC can't reverse the polarity of one sub only. So to integrate the 2 subs together without reversing 1 polarity DLBC must do something new to give the same DLBC filter you see.Maybe it explains what we see? Either way, the REW measurements show that all seems to work. except maybe for the headroom lost?

 

[JStewart]

If you turn the gains up by a few dB on the sub plate amps and rerun the measurements and calibration you should get the headroom back. Subs should also get a few dB of trim which could possibly help with edge case digital clipping.