Home Speaker Asylum

General speaker questions for audio and home theater.

[ Follow Ups ] Thread: [ Display  All  Email ] [ Speaker Asylum ]
[ Alert Moderator ]

Long-winded reply to, ah... your reply to my... um... reply

Richard,

Thanks for taking the time and energy to answer. I'll only comment on a few areas, but brevity isn't one of my gifts.

Duke wrote: "But as we all know, changing the location of a subwoofer has clearly audible and even dramatic effect. The reason it does is the path-length-induced peak and dip pattern that I've described (and which Roy Allison described long before me, but he focused on the reflections off the wall closest to the speaker whereas I'm assuming the subwoofer starts out up against that wall)."

Richard BNG replied: "Not true. Subs tend to be located near walls, or no more than a few feet from walls. This is too close to affect 14 feet and longer wavelengths? Well ... it wouldn't be a good idea to locate two subs so their drivers were 4 feet from the side walls, 4 feet from the front walls, and 8 feet apart. That could cause a deep narrow null."

Duke comments: I must have communicated poorly. In assuming that the subs are placed close to one wall, I'm ignoring the reflection off of that wall. It's the reflection off the other walls - in particular the wall on the other side of the listener - that I originally wrote about. Those walls are plenty far enough away to affect 14 foot wavelengths.

* * * *

Duke wrote: "I believe one key to good subwoofer integration with the main speakers is generating a low frequency sound field that is similar to that generated by the main speakers at higher frequencies."

Richard BNG replied: "Impossible. Bass is omnidirectional. Sound gets more directional as the frequencies rise."

Duke comments: Actually the directionality of sound is related to a combination of factors, wavelength being one of them. It is quite possible to have a directional woofer and an omnidirectional tweeter. The soundfield is a combination of direct and reverberant energy. At midrange and high frequencies, we don't get audibly significant room-induced requency response anomalies (though we do get speaker-induced ones that carry over into the room). If the speakers are flat in the midrange and treble, the combination of direct and reverberant sound will not measure flat but the peaks and dips will be close enough together that they won't be audibly apparent. The asymmetrical subwoofer placement I suggest will result in dissimilar peak-and-dip patterns, and the closer the peak-and-dip spacing the less audible individual peaks and dips are because the ear integrates the sound within roughly 1/3 octave wide bandwidths (called "critical bands"). I'd have to put on my thinking cap to explain this psychoacoustic phenomena, but will do so if it would be of benefit to you.

* * * *

Duke wrote: "Scattered multiple subs addresses this. Given that the ear is very poor at judging the direction of a low frequency sound source without upper freqency cues (hence the steep crossover), and that the ear is obviously pretty good at hearing large peaks and dips in bass energy, I place the higher priority on getting the soundfield right."

Richard BNG replies: "I wish scattered multiple subwoofers smoothed the bass response. The soundfield is never right if there are any bass peaks +3 to +6dB from standing waves (because +6dB can means a bass note fundamental tone sounds twice as loud as the bass musician intended!) Add in a null or two and you hear a different bassline than the musician intended in our small rooms (compared to listening to headphones or listening to speakers or a live bass musician in a nightclunb or auditorium.) Very large home listening rooms tend to have reasonably accurate basslines unless the ceiling is under 10 feet tall."

Duke comments: Scattered multiple subs helps audibly. The reason the bass is reasonably accurate in very large rooms is in part because the peaks and dips are spaced close enough together that they don't have serious audible consequence. That's exactly what I'm doing with scattered multiple subs, but in smaller rooms.

* * * *

Richard wrote: "The oddest thing about people experimenting with multiple subwoofers is they tend to place all the subwoofers on the floor where they fully excite the very important floor-to-ceiling standing wave (70 Hz. in 8 foot tall rooms, and I'm assuming the sub has full output at 70Hz). There are theoretical advantages with four subwoofers (left floor, left ceiling, right floor, right ceiling) if the ceiling doesn't rattle from the bass (it will) and the wife doesn't send you to the funny farm (she will) and you can afford FOUR subwoofers."

Duke comments: I absolutely agree! This is an example of exactly the principle I'm advocating. I only spoke about scattering the subwoofers within the horizontal plane, but they should be scattered in the vertical plane as well. Ideally, at least one sub should be located above the centerline height of the room (over 4 feet off the gound in an 8-foot room).

I could point you to comments made by people who have heard a scattered multiple subwoofer system, but it would be somewhat self-promitional.

Best regards,

Duke

This post is made possible by the generous support of people like you and our sponsors:
  Signature Sound   [ Signature Sound Lounge ]

Follow Ups Full Thread
Follow Ups
You can not post to an archived thread.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]