Searching for matching(?) Subwoofer solution

Mijostyn wrote:

"For the drivers to act as one they can be no farther apart than 1/2 the wavelength of the crossover point."

You do an excellent job of explaining your suggestion, but imo the issue it addresses is not one that a distributed multisub system is concerned with.

With a distributed multisub system, "the drivers acting as one" is definitely NOT the goal. We want each sub to interact with the room very differently from the others, and that is accomplished by spreading them far apart. So not only are there subs more than a half wavelength apart, they will also (almost always) have different path lengths to the listener(s).

Because the ear has very poor time domain response, such that it cannot even detect the presence of bass energy from less than one wavelength, a bit of smearing in the initial arrival times of the different subs is inconsequential. What DOES matter a great deal from a perceptual standpoint is how the notes decay. Since speakers + room = a minimum-phase system at low frequencies, when we have fixed the frequency response we have simultaneously fixed the time-domain response. Imo this is something that a good distributed multisub system does well.

(The ear hears low-frequency ringing quite well, but such ringing is always accompanied by a frequency response peak, and vice-versa. Anywhere in the bass region where there is a peak, whether it originates from a speaker anomaly or a room anomaly, the energy in that region takes longer to decay. It is actually the frequency response peak that we hear, not the ringing - the slow decay - itself. But when we have fixed the one, we have simultaneously fixed the other.)

Duke

Mijostyn wrote: "The statement that the ear (which should be ears) have very poor time domain response is 180 degrees wrong."

You are correct! I did not proofread carefully. Here is what I should have said:

"Because the ear has very poor time domain response AT LOW FREQUNCIES..."

The ear is indeed quite sensitive in the time domain at higher frequencies.

Mijostyn again: "Speakers + Room do not equal a minimum phase system."

Yes they do at low frequencies, which is what I said. This according to Floyd Toole and Earl Geddes. The in-room frequency response tracks the time domain response. The phase behaviors of individual reflections don’t matter when viewed in isolation, but their sum is relevant as it shows up simultaneously in both the in-room frequency response and in-room time domain response. It is the sum that we hear.

Mijostyn: "With the drivers acting as one the bass drum impact will strike the listener in phase with the greatest force resulting in the largest smile. The decay afterwards is of no great significance."

This is what our intuition tells us, and our intuition is wrong.

We literally cannot detect the presence of bass energy from less than one wavelength, which is 22.5 feet at 50 Hz (ballpark resonant frequency of a bass drum). A study was done in which less than one full wavelength of low frequency energy was played over headphones, so there were no room reflections, and it was UNDETECTABLE. And it took MANY cycles before the ear began to register the pitch. By the time your ears BEGINS to hear the impact of that bass drum played over your system, so much time has passed that any minor arrival time differences are inconsequential.

The decay is of enormous consequence because it shows up as a frequency response peak. And this is because speakers + room = a minimum-phase system at low frequencies. If the decay is slow at some frequency then the bass sounds fat because there is a response peak at that frequency.

Mijostyn:  "I know of one person who set up his four subs as I suggested and he thought it made an improvement."

The improvement may not have been for the reasons you suggest.   I strongly suspect that what happened is, the frequency response improved.  The in-room frequency response is what dominates our perception at low frequencies (though the in-room frequency response is merely a manifestation of the in-room time domain response, and vice versa).

Duke