Nathan advises that the four or more subwoofers “swarm“ concept works best when the subwoofers can be placed approximately equidistant from the listening position. My listening room will not allow for this because my listening position will be only a few feet in front of the rear wall.
I hope you don't mind me replying. I make a four-piece subwoofer system called the Swarm.
The basic idea of course is to spread the multiple subs around the room in a manner that smooths the in-room frequency response. The premise is that the in-room response smoothness is what matters the most. Let me explain:
At low frequencies speakers + room = a "minimum phase" system, which means that the frequency response and the time-domain response track one another. So, fix one and you have fixed the other. Bass traps improve the time-domain response directly and therefore indirectly improve the frequency response. A distributed multisub system improves the frequency response (throughout the room typically) and therefore indirectly improves the time-domain response.
Intuitively it would seem that having the arrival time be the same at the listening position for all four subs (implying equidistant placement) would be the ideal. In my opinion higher priority should be given to in-room smoothness. So this is where I disagree with Nathan Funk (though I agree with pretty much everything else he said).
You see, the ear/brain system has very poor time-domain resolution at low frequencies, such that minor differences in arrival time are inconsequential in and of themselves. The ear is incapable of even detecting the presence of bass energy from less than one wavelength, and from 80 Hz to 20 Hz we're talking about wavelengths from 14 feet to 56 feet long. So arrival time differences that correspond to a small fraction of a wavelength are not going to make an audible difference, as long as the blend with the main speakers is good.
But what the ear/brain system IS very good at is, hearing differences in sound pressure level in the bass region. This is revealed by looking at a set of equal-loudness curves, which bunch up south of 100 Hz. A 5 or 6 dB difference at 40 Hz can be as big a change in perceived loudness as a 10 dB change a 1 kHz. This is why we can hear the bass so much better when we turn the master volume up.
When we have in-room peaks, two bad things are going on: First, those peaks stick out like sore thumbs even worse than we might think from eyeballing the curve, because of the ear's heightened sensitivity to SPL differences in the bass region. Second, those peaks decay into inaudibility SLOWER than the the rest of the bass region, and therefore blur subsequent notes and degrade clarity (resulting in "boomy", "muddy", or "slow" bass).
The good news is, when we improve the in-room frequency response (simultaneously improving the time-domain response), the subjective improvement tends to be greater than we'd expect based on eyeballing the before-and-after curves. In my experience, improvements in in-room smoothness pay unexpectedly large subjective dividends.
Now there is a bit more to my Swarm setup suggestions than simply spreading four subs around the room. I suggest using the phase control settings and/or the polarity of the individual subwoofers, as well as possibly plugging some or all of the ports on the individual subs, along with pretty much anything else that is reasonable feasible and improves the in-room bass smoothness.
In other words, I consider the in-room bass response smoothness (including smoothness of integration with the main speakers) to be the thing that matters most because it lies in the domain that we hear the best. And I subordinate pretty much every other consideration in its pursuit, including the simultaneous arrival-time one would theoretically get with equidistant placement.
Mind if I indulge in an anecdote? At RMAF 2018 we had a veteran cable manufacturer spend a fair amount of time in our room. He has literally decades of experience with audio shows. We played his reference recording, of "Fanfare for the Common Man", which I think was the same version as on Wilson Audio's demo disc. Anyway he said it was the most natural-sounding reproduction of those tympani he had ever heard, and he was including a lot of big names (in a lot of big rooms) when he made that statement. "That's what a tympani sounds like" he said, and then went into detail about what he was hearing that corresponded with hearing tympani live. The Swarm in that room was not set up with any consideration given to synchronizing the arrival times; on the contrary, the placement was deliberately asymmetrical and we had the left-hand pair of subs in phase quadrature (shifted 90 degrees) relative to the right-hand pair of subs.
? Besides what does low sensitivity and high power consumption have to with integration?
