I would measure with your main speakers on as you want the entire system in balance. The mains will cancel/add to some frequencies no matter how carefully we place the speakers and sub(s).
Keep in mind that +6dB voltage does not mean +6dB SPL. These are different concepts and cannot be directly compared. Perhaps start by measure the sub with the SE input, and then measuring the sub with the XLR (with the SE connected to the amps but not on) and set the sub level to match. This will at least give you a baseline.
Elk said
I would measure with your main speakers on as you want the entire system in balance. The mains will cancel/add to some frequencies no matter how carefully we place the speakers and sub(s).
Keep in mind that +6dB voltage does not mean +6dB SPL. These are different concepts and cannot be directly compared. Perhaps start by measure the sub with the SE input, and then measuring the sub with the XLR (with the SE connected to the amps but not on) and set the sub level to match. This will at least give you a baseline.
Elk, thanks for pointing out the Voltage vs. SPL difference. My point was that I risk the subs to be dominant if only one of the subs is brought into the equation during calibration.
The trouble with adjusting the level to match is that I use an xo of 50Hz, meaning that over 50Hz there is little info from the subs and under 40Hz there is little info from the speakers. Since it is open baffle, the room determines the lowest frequency to be reproduced which is about 35Hz. So the band is pretty narrow when trying to find the optimal level, still if the roll off is not extremely steep. It is also a bit difficult to achieve a seamless transition around the xo point, but I think I succeded rather well. No one has ever pointed out suck outs or similar.
Having 3off 12’’ woofers per channel to my disposal in my 45 ft2 attic makes quite an impact down to 20Hz (and I have yet to mention my 15’’ LFE sub in my 7.1 setup)
The trouble with adjusting the level to match is that I use an xo of 50Hz, meaning that over 50Hz there is little info from the subs and under 40Hz there is little info from the speakers. Since it is open baffle, the room determines the lowest frequency to be reproduced which is about 35Hz. So the band is pretty narrow when trying to find the optimal level, still if the roll off is not extremely steep. It is also a bit difficult to achieve a seamless transition around the xo point, but I think I succeded rather well. No one has ever pointed out suck outs or similar.
Why not set a high cross over to start, say 100 Hz, get the dB right with a slow freq sweep (avoids room nodes), then lower the crossover to what sounds best? That should get you most of the way.
The trouble with adjusting the level to match is that I use an xo of 50Hz, meaning that over 50Hz there is little info from the subs and under 40Hz there is little info from the speakers. Since it is open baffle, the room determines the lowest frequency to be reproduced which is about 35Hz. So the band is pretty narrow when trying to find the optimal level, still if the roll off is not extremely steep. It is also a bit difficult to achieve a seamless transition around the xo point, but I think I succeded rather well. No one has ever pointed out suck outs or similar.
Why not set a high cross over to start, say 100 Hz, get the dB right with a slow freq sweep (avoids room nodes), then lower the crossover to what sounds best? That should get you most of the way.
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I think the crossover is at its best setting (from listening tests and measurements), but for the purpose of finding the ideal volume setting, I think your idea is good, canto4me
I see your point with the sweep, even though my room is pretty much treated.
The sweep wil add complexity in getting the correct setting, though (but in the end it might provide a better result overall).
