I have a room issue which is not serious but I'm struggling to get a handle on the cause. The situation is that I have a pair of Magneplanar Tympani speakers, which each provide a sound source approximately 4 feet wide by 6 feet tall, so there is no single location for each speaker which can be identified as the "source". Each of the 3 panels on each side covers a different portion of the frequency range, some overlapping, others not (the system is tri-amplified). The room is small enough that I also don't have much of a choice about where they are placed. I've moved them around as much as I can, but they are where they are and it's not going to change much. They are crossed over to a Dayton sub at 63 Hz.
The problem is that I have a few large nulls in the response between 150-250 Hz, likely due to room size and LP location. Most of the response irregularities yield readily to EQ and panel position, leaving only these. I have attempted to simulate the room in REW, but the problem is that the speakers are too wide to simulate, and even the portion which covers the frequency range in question for each speaker is about 3 feet by 6 feet. So the room simulation of the speakers doesn't match the actual room very well. It seems that the nulls somewhat relate to the distance between the perceived midpoints of the low/mid panels for each speaker, but again, this distance isn't going to change so I can't alter it. Moving the measurement mic causes the nulls to appear at different frequencies to some extent; however, I've done the moving mic measurement average, and it actually tends to accentuate the major null at 140-160 Hz over a traverse, rather than smooth it out as you might hope. Moving the LP forward or to the rear doesn't seem to help with the major null; moving to either side puts me far enough off axis that it starts to impair the stereo image. So it does seem to be a real phenomenon and not an artifact of measurement.
Up till now I've been ignoring it because it subjectively seems to be minor and doesn't impair the enjoyment of music. But I'd like to try to address it if I can. I have another null near the upper crossover frequency (1300 Hz) which seems to be an interaction between the individual panels, so I wouldn't be surprised if this is another similar effect. But without being able to simulate the room/speaker situation, I'm only making slow progress.
I've attached the mdat file of a nominal measurement (which should include the room sim), a MMM RTA capture, and a picture of the speakers (not quite the current positioning) to give a sense of my environment. You can see that the RTA of both speakers together exhibits the 150 Hz null, while it's only hinted at in the swept measurements. The speakers are definitely in phase electrically, which is why I'm suspecting some kind of inter-panel cancellation effect, reason unknown.
The problem is that I have a few large nulls in the response between 150-250 Hz, likely due to room size and LP location. Most of the response irregularities yield readily to EQ and panel position, leaving only these. I have attempted to simulate the room in REW, but the problem is that the speakers are too wide to simulate, and even the portion which covers the frequency range in question for each speaker is about 3 feet by 6 feet. So the room simulation of the speakers doesn't match the actual room very well. It seems that the nulls somewhat relate to the distance between the perceived midpoints of the low/mid panels for each speaker, but again, this distance isn't going to change so I can't alter it. Moving the measurement mic causes the nulls to appear at different frequencies to some extent; however, I've done the moving mic measurement average, and it actually tends to accentuate the major null at 140-160 Hz over a traverse, rather than smooth it out as you might hope. Moving the LP forward or to the rear doesn't seem to help with the major null; moving to either side puts me far enough off axis that it starts to impair the stereo image. So it does seem to be a real phenomenon and not an artifact of measurement.
Up till now I've been ignoring it because it subjectively seems to be minor and doesn't impair the enjoyment of music. But I'd like to try to address it if I can. I have another null near the upper crossover frequency (1300 Hz) which seems to be an interaction between the individual panels, so I wouldn't be surprised if this is another similar effect. But without being able to simulate the room/speaker situation, I'm only making slow progress.
I've attached the mdat file of a nominal measurement (which should include the room sim), a MMM RTA capture, and a picture of the speakers (not quite the current positioning) to give a sense of my environment. You can see that the RTA of both speakers together exhibits the 150 Hz null, while it's only hinted at in the swept measurements. The speakers are definitely in phase electrically, which is why I'm suspecting some kind of inter-panel cancellation effect, reason unknown.
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