Why is good, deep bass so difficult? - Myths and their Busters

Skanda wrote: "Do sealed speakers integrate better into these rooms?"

It’s ALWAYS a matter of speaker + room, and if the room is contributing a lot of boundary reinforcement, sealed boxes generally result in better synergy. If not, then vented boxes generally result in better synergy. I can go into more detail if you’d like, BUT the specifics ALWAYS matter more than these sort of generalities.

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A lot of different suggestions have come up in this thread, things that have obviously worked for the people who tried them. Because of the ear’s exaggerated sensitivity to small changes in SPL at low frequencies (shown by the bunching up of equal-loudness curves south of 100 Hz), combined with its poor time-domain resolution (which is why we can’t localize the source of very low frequency sine waves), we can infer that the improvements we hear are primarily due to changes in SPL, even if they "sound like" changes in "speed".

At the risk of over-simplifying, and being open to correction on any of these points, some things simply make a bigger difference than others. To set the stage, it’s not uncommon for in-room response across the bass region to have peak-to-dip swings of ballpark 12 dB, or +/- 6 dB. Changes to speaker damping (mechanical or electrical or acoustics) seldom result in more than a 1 dB difference, but in the low bass region that's as audible as a 2 dB change in the mids. Improvements to room acoustic damping (bass trapping) can result in 2 dB or maybe 3 dB reduction of the maximum peak-to-dip swings. EQ is generally good at chopping off the peaks but not so good at filling deep dips, still +/- 3 dB is often feasible, and perhaps better if optimized for a small sweet spot. A distributed multisub system results in smaller and more numerous peaks and dips (which has psychoacoustic benefit), with +/- 3 dB over a wide listening area being reported by many users. Remember, smooth bass = "fast" bass, perceptually.

The good news is, these different approaches are not mutually exclusive. You can start with one and then add another as your piggy bank recovers.

One final implication of the bunching up of the equal-loudness curves south of 100 Hz is, there is subjectively a LOT of room for improvement over the typically poor low frequency response of most speaker/room combinations.

Imo, ime, ymmv, etc.

Duke

gkr7007 wrote: "...I gravitate toward planars and other very fast response speakers."

Planars are subjectively "fast" because they have smoother in-room response than monopoles (even though the actual low-frequency transient response of their diaphragms is often quite poor, certainly not "fast" at all). This smoother in-room response of dipoles arises from the 180 degree phase difference between the backwave and frontwave, which effectively launch in opposite directions. When the frontwave and backwave meet up again, after several bounces off of room surfaces, their phase response is significantly more randomized than would be the case for a monopole speaker’s room bounces. And the sum of highly random-phase bass energy is much smoother than the sum of largely in-phase bass energy. "Decorrelation" is the proper word... decorrelation = smoothness, and is highly desirable in the bass region, and is something big rooms do better than small rooms. Decorrelation is also the advantage that a distributed multisub system offers over a single big sub... same basic mechanism as planars, but set in motion by different means.

As the wavelengths get very long relative to the room dimensions, planars tend towards cancellation because half of their in-room energy is out of phase with the other half, so planars don’t make very good subwoofers unless they are very big and can move a lot of air, and are in a big room.

In general, two intelligently-positioned monopole subs approximate the in-room bass smoothness of a single dipole main speaker. So it takes four intelligently-positioned monopole subs to approximate the in-room smoothness of two dipole mains speakers.

Duke