I plan to go to separate L/R eq in the next two weeks. I could shoot some white noise...
So did a lot of measures yesterday. Realized I had a door open I wanted closed. Remeasured. Found out one of my speaker cables was half out. Quit. Came back, remeasured. L/R PEQ worse than Single PEQ. Realized in all the toe moves lately, one of my speakers ended up 1.5" too far forward and 1" too close to the side wall. Tape measure.
Things went well today. But you don't get as many measures as planned.
First, white noise at 70db and a sweep at the same system volume. White noise smoothed 1/12, sweep 1/24, just to show the pattern before the next measurement set.
Speakers roll off starting at 40hz, the dip just north of 40hz is from the measurement position.
So... Looks the same except with a well planned room gain. I did think long and hard about these speakers for my room.
Ok, now for white noise at 60db, 65, 70, and 75, 1/24 smoothing (enough to show things and be legible). 60db yellow, 65 green, 70 red, 75 blue. Tight on 20-200.
Start by looking at the peak at around 72hz, that's a pure room mode, nothing the floor does to it.
Next look at the peak at 30hz and the dip at 44hz. At 30hz, bimodal at 60db, green super peak as the floor kicks in at 65db, then pulled back down at 70db, then back to bimodal at 75db.
At 60db, room modes are not yet in full force, but the floor is bouncing a bit. At 65db the floor is bouncing (pulls towards 30), at 70db the room mode is kicked in strongly, pulling things back towards that 32hz or so room mode. Why is the peak lower? Because other floor frequencies suck up some energy at that point, draining 30hz a bit (look at what 120 hz does). At 75db the floor and room mode are back in balance. Above this SPL, 30hz will continue to spike relative to 32hz and grow quickly.
For 44hz, note the peak pop up at 75db. I don't know how that can happen if it is not floor related. Room mode pulls down 44hz at 65-70db, floor mode spikes up at 75db.
Next, look around 120hz. One peak, bimodal, one, bimodal. That's another indication of a floor mode and room mode interacting. Note that the two bimodal peaks are the ones for measures with the highest SPL at 30hz.
At higher spl, up from the 75db measure, the peak just above 50hz will slide up to 60hz, and then 60hz will spike up, at which point 30hz will be way up, as will all sorts of things 80-125, depending on specific volume. 80hz-125hz shows a lot of odd shifts. But 30-60-120 definitely show floor effects, and at +5db over the highest on the graphs shown I'll get a 95 peak. Likely 90hz floor and 100hz heating ducts.
Lots of odd things happen in this range, so if I went with different cut points for my 5db jumps, we might see some other things happen. If I ditched the smoothing or went 1/48 we could see lots more happen, but it would be very hard to read. I think this series does show HOW the floor and room modes interact in a few places, so, I think it should help show what happens in my very lively room.
Oh, I did move the mic to see how 30hz acted through the room. Hand held, poor measures, but I was thinking that 30hz is pretty stable, 32hz is not, and then my cat shut down REW before I saved anything. Yes, yesterday was a cursed day for measuring in this house, that's for sure.
So, I have floor modes from a bouncy floor that are close to room modes, and they interact in complex ways at different volumes. Or so I see it.