SME Posted January 23, 2017 Author Report Share Posted January 23, 2017 So lately, I've probably been enjoying my existing system too much and not spending enough time working on my subs. I've continued to make very minor tweaks to the system. The biggest change was to back off on the boost to 190 Hz on the center channel and instead make it ~flat "on-average" across the seats. This is mostly because I often sit off-axis, and it didn't sound so good in those other spots. The excess 190 Hz tended to overwhelm and mask out a lot of detail in voices whose fundamentals hit that spot. It is an acceptable compromise until I extend the baffle. The center still sounds very good, and it's nice to not have the weird feeling (literally) that arose from the build-up of later arriving energy at that frequency. Otherwise, I boosted my sub bass response a bit, giving it a bit of an upward tilt. I think the "first arrival determines tonal balance" concept doesn't apply in the same way to bass because room gain tends to naturally boost even first arrival sub bass in most situations. An anechoically flat speaker will typically run hot in the bass without EQ adjustment, and that's often just the way things are monitored. Instead, I've opted to adjust things by ear, and a few extra dB with some slope up toward the bottom seems to sound better. There is a very clear point where too much low end washes out much of the transient detail. Kick drum might go boom but not really thump, and bass instrument can sometimes go from being punchy and well-defined to indiscernible sludge. If I raise the response to that threshold and then back-off about 0.5 dB, repeating this process for different regions of the response, I get a very solid, satisfying thump with no overhang from most kick drum. Where I've struggled more is with taming the high end. Running the top end flat just doesn't work for my ears and for most others. In fact, it can be very irritating with a lot of content that I think most would regard as being well recorded. What I'm finding is that the shape of the roll-off is to an extent more important than the amount of roll-off involved. Very minute changes to the shape can have a big impact on the sound. At the same time, content is quite variable in overall top octave strength, so I feel that having an adjustable UHF control will be advantages. I recently decided to experiment with a hypothesis that the best roll-off shape will almost approximate the roll-off caused by dissipation of sound as it moves through the air. I was surprised to see that dissipation is actually pretty significant even over short distances for the highest frequencies. After reviewing data of UHF roll-off vs. distance at various humidity levels, I settled on simulating distance roll-off via a single biquad centered at 12750-13000 Hz (higher for greater roll-off amounts) with a Q of 0.5 and gain ranging from 0 to -10 or so, approximately equivalent to roll-offs due to distances ranging from 0 to 20 meters or so. With most content, I seem to do well by about -3 dB or ~6 meters of distance and occasionally opt to push it out to -6 or -10 dB for ~12 meter or ~20 meters of distance. The consequence of adjusting the roll-off while maintaining the constraint of physical realism is is remarkably subtle. It kind of acts like the audible equivalent of a sharpness control. Too much, and the transients have a bit too much bite. Too little, and there is a loss of fine detail as well as crispness. These changes are very subtle, even compared to say boosting 15-20 kHz by 1 dB *without* altering the frequencies below and thus ending up with a physically unrealistic curve. Along these lines, it's very fascinating to me that UHF and very low frequencies can mask one another substantially. For a few hours, I accidentally had 15-20 kHz and up running about 1 dB hotter than I meant to run it, and it caused much of the sub bass to sound very distant and lose almost all of its weight and feeling. But it only happened on certain soundtracks, those with full extension. I was really weirded out until I recognized that it was the UHF that was masking the bass and causing it to diminish. I tried pushing the subs up 3 to 6 dB, and it did nothing for its subjective loudness or power and merely muddied the sound. Without fixing the UHF, there was no helping the bass. Bringing the UHF to proper balance totally fixed the problem completely to my great relief. I have also observed masking in the other direction. When I had some harshness in the UHF, boosting around 45 Hz or so seemed to quell it considerably, even when I couldn't conciously hear any content down there. Psychoacoustics are very weird. Another thing I encountered when playing with UHF response and ending up too hot in parts was a sort of unrealistic hyper-detailed sound. I haven't seen a Darbee before, but I imagine it to be the audio equivalent of turning the Darbee effect up way too high. Upon first impression, the sound is incredibly enhanced, with far more richness and detail than is heard normally, but only upon more careful disciplined listening does it become clear that the sound is completely inaccurate and unrealistic. At this point, I am declaring this experiment a success. The sound seems to have improved by another notch. Cymbals and hats sound absolutely great. Indeed, I'm hearing cymbals emerge in background content of soundtracks where I never heard them before. And there's even less harshness than there was before. For the occasional soundtrack that still "bites" a little, I can easily dial-down the UHF without losing detail or weirding out the tonal balance. Quote Link to comment Share on other sites More sharing options...
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