I recently did some measurements to verify the automatic phase settings chosen by GLM between my 8331 and 7350. What I discovered was quite disappointing from my point of view.
The "phase shift" in the 7350 (and probably 7360 etc.) actually is a simple delay. It only adds about 0.5ms per 15 degree step. And since it's not possible to add negative delay, the steps -15 till -165 add even more delay. From 0 degree..90..180=-180..-90..-15 it's adding up to 12ms. Of course for the exact crossover frequency this will result in the desired phase shift and maximum addition. You can hear this during calibration. But that's about all it does. And two things keep me worrying here:
1. if your sub is slightly behind and all you would need is a minor delay of your main monitor, then the attempt to correct it with a phase shift of -15 degrees in the sub results in a delay of 12ms. This is in phase, but a complete cycle too late compared to your mains. I guess people who buy the 8331 and 8341 love their excellent timing and transparency. I cannot imagine anybody wants to ruin this on purpose.
2. even if the crossover frequency is in phase with the added delay, due to the added cycle we now have comb filtering below and above that crossover frequency. Due to the steep filters this is not very audible, but still, why ruining your frequency response around the crossover frequency? The 8331 is a master piece of engineering, and then the crossover is treated with such disrespect?!
Well, I went on even further and tried to fix the problem by adjusting the necessary delay inside the 8331. I added 3.1ms while both 8331 and 7350 were standing exactly next to each other. Then they were perfectly aligned to each other at 80Hz. But now there is an even bigger problem: while the Low Pass in the subs hasn't changed its polarity at the crossover frequency, the 8331 have a 180 degree phase shift when you add the High Pass Filter. This means even if they are both perfectly time aligned, there is also a perfect cancellation at 80Hz. Even worse than what we got before.
This leads to my question: why is there no polarity switch for the subs? Especially knowing that the built-in crossover design of the 8331 makes this absolutely necessary! The 180 degree setting in the phase settings only adds delay, but does not invert the audio signal.
A simple button would solve a lot of the before mentioned problems. And then users could at least setup their speakers manually, getting perfect results.
Anybody from Genelec who can advise here?
I have been very happy with the sound of the 8331 so far, but without a proper sub integration this makes me quite unhappy with my investment. I hope for a quick firmware update.