So in order to fix a burst pipe, I had to cut a big honking hole in the wall right behind my equipment rack. I didn't really expect such an activity to affect the sound quality of my system -- not in the least. But I distinctly noticed two effects.
The first effect I'm fairly sure was entirely psychoacoustic. My eyes kept drifting over to this open wound in my wall and -- wouldn't you know it -- so did the soundstage. Images that previously were perfectly centered seemed to drag over to the right by a foot. The second effect was suspiciously feasible. My room has always had a giant 40Hz hump, one that is impossible to mitigate via speaker placement. I've come to expect this lumpy bass response, and my ears have eq'd it out. I no longer hear it. My Anthem MRX 300 receiver uses its own built-in software to smooth out that hump, and as a result, when I'm watching movies my system feels bass-shy and I have to resist the urge to bump up the sub level. After I'd opened up that wall and subsequently re-installed my system, I hadn't thought much about bass response, being mostly disconcerted by the drag to the right of the soundstage. A week later the Nordost Tyr 2 cables arrived, and I stripped the system down once more in order to insert them. I took this opportunity to sweep, dust, and then dress the cables into a semblance of order. Cleanliness, godliness, and so forth.
Jon Baker of Nordost had arranged to visit a few days after the arrival of the cables in order to ensure that all was well with them and the system within which they were residing. Part of my clean-and-tidy efforts were aimed at getting my room ready for his visit -- I'm proud of my system (as are, I'd imagine, many audiophiles) and want to show it off to its best effect.
As he laid his hands on my system, in his best Southern-Baptist manner, Jon proclaimed all was well, and we got down to the real business -- music listening. Jon is a great listener, and has an encyclopedic memory for music. Once I found out that we both have a soft spot for Talk Talk and Cocteau Twins, it seemed as though we were practically related.
Looking askance at the gaping wound in the wall right behind my turntable, Jon asked me if perhaps there might be a better way to control bass resonances, the import being that maybe the fiberglass-filled cavity could be acting as a bass trap. Initially I laughed politely at his joke, but after he had left, I began to wonder. That bass hump didn't feel quite so profound, and it dawned on me that the cavity might actually be doing something to the acoustics of my room.
Out came my old XP computer and the Anthem microphone that came with my MRX 300 receiver, and I ran a series of Anthem Room Correction sweeps to measure the room response. As you can see by comparing the response from a previous measurement (above) to the fresh measurement of my right speaker (below), which is closest to the cavity, the lower end of the hump at around 30Hz is nipped off a bit. It's not ideal -- it would be way better if the peak at 40Hz was tamed a bit, but that's not the point. I've no intention of leaving that hole open. But that said, if the net effect of that hole were to actually trim the hump right at 40Hz, I might have considered simply covering it over with some nice fabric.
Room acoustics management via gaping holes in drywall. Who would have thought?
Jason Thorpe
Contributor, SoundStage!