Speaker Asylum General speaker questions for audio and home theater.

---

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

---

[ Alert Moderator ]

---

Duke Duke Duke Duke of Earl .... If I charged you for corrections to your posts, I'd be rich!

Posted by Richard BassNut Greene on March 9, 2007 at 09:24:58

In Reply to: No, that's NOT what I'm saying. Average the output of multiple subs at any ONE seat. posted by Duke on March 8, 2007 at 12:56:05:

Richard BNG wrote: "Forget averages -- at every INDIVIDUAL seat the bass frequency response is still uneven no matter how many subwoofers you use (unless every listener gets his own near field subwoofer)."

Duke replies: Still uneven, but definitely improved.

RG
If all the subwoofers are on the floor and their frequency range includes the first-order floor-to-ceiling axial standing wave (71Hz. with 8 foot ceiling, and lower Hz. with taller ceilings), then listener is most likely to hear a bass boom from that room mode = not good.
.
.
.
.

Richard BNG wrote: "The other guy, I forget his name, recommended left-right subwoofers connected out of phase, the last time I read his paper."

Duke replies: Griesinger is the guy, and he recommended left-right subs based on maximizing the interaural phase difference to maximize the psychoacoustic sense of "envelopment". The recommendation of 90 degree out-of-phase operation of one sub was to synthesize envelopment in recordings with monaural bass by maximally de-correlating the in-room low frequencies. I haven't tried it yet but plan to.

RG
This idea has potential for reproducing low frequency room ambience if included in a surround sound recording. Not useful for two-channel audio (where connecting front left front and right front subs in-phase prevents a first-order axial side-wall-to-side-wall standing wave, making bass frequency response more uniform from left to right across a couch.)
.
.
.
.
Richard BNG: "Linkwitz goes for dipole bass which reduces excitation of most room modes -- perhaps the best advice of all for those unwilling to parametrically equalize their subwoofer, or buy a batch of bass traps."

Duke: Now we're on some common ground. I like dipole bass - it tends to be very natural sounding, with excellent pitch definition. The reason for the naturalness of dipoles is not that they excite fewer room modes - you see, the initial figure-8 pattern is immediately swamped by the reflections, so the room modes get excited anyway.

RG
Floor-to-ceiling and side-wall-to-side-wall standing waves get excited about 4.8dB less using dipole subwoofers versus monopole subwoofers. Period.
.
.
.
.
.
You Wrote:
It is rare that owners of dipole speakers are happy with the way a single sub integrates into their system. This is because the output of a single sub in as small room is well correlated, and has a very different "feel" from the dipoles' output which is highly de-correlated in-room.
RG
This is because the dipoles excite many standing waves less than monopole speakers and this causes better quality bass in most rooms.
The monopole sub doesn't have this advantage.
.
.
.
.
Dipole owners are more likely to be happy with two subwoofers than one, this based on my own observations of posts by dipole owners. I believe the reason is improved de-correlation of the bass so that there's less discrepancy between what the subwoofers are doing and what the dipoles are doing. In my opinion the next logical step is scattered multiple subs.

RG
Bass on almost all two-channel recordings is mono -- there is no out-of-phase bass information in the left and right channels.
Bass problems are caused by multiple in-room reflections that may be in-phase or out-of-phase with the direct signal from the subwoofer
.
.
.
.
Richard BNG: "There is no evidence from real rooms that more than one subwoofer in one location is needed for decent bass under 80Hz. (other than SPL requirements that require more than one subwoofer)."

Duke: So why do you use and advocate two subs, if only one is needed?

RG: I use one subwoofer placed behind my left speaker.
That room position is near one main speaker because nearby upper bass output from the main speakers helps make a subwoofer sonically invisible.

The sub is about 7 feet from the front wall and 5 feet from the left wall.

The driver is 4 feet above the floor, for reduced excitation of a strong concrete floor to stiff ceiling standing wave, and aimed at the ceiling for some additional "mechanical" low-pass filtering.

The crossover is 70Hz. & 24dB/octave. The turnover frequency would be lower than 70Hz. if my EPOS ES11 satellite speakers could handle that.

If it were possible to fit two 18 inch diameter 4 foot tall tube subwoofers "in the middle of my living room", then I'd have two.

Just yesterday the wife gave me her annual "You don't know how lucky you are to have a wife who allows you to place two speakers and that phallic symbol subwoofer in the middle of our living room" speech.

My response is the same:
I guess I should buy tiny Blose Acoustimess Sheikers and put all five of them BEHIND the large screen TV set where they sound awful ... like our P-whipped friend xxxxxx's wife makes him do?
.
.
.
.
Richard BNG: "And the closest thing to a bass transient, the slap of a hammer on a kick drum, will not have the best possible sound quality if the two to three drivers in each channel (subwoofer driver, bass driver and mid-range driver ... or subwoofer driver and bass-mid-driver) that reproduce its sound are not located near one another."

Duke: Excellent objection, as intuitively the loss of impact seems obvious. This is the objection that kept me away from trying scattered muliple subs for a long time. In reality, the ear doesn't hear the initial wavefront of a bass signal. In tests where a single bass frequency cycle was presented to listeners, it was difficult to even detect. It takes several cycles for the ear to detect the presence of bass energy, and several more for the ear to correctly hear the pitch. So by the time the ear is detecting bass, the outputs of all subs in the room is being integrated.

RG
Baloney.
The attack of a bass guitar note (the "pluck") and the attack of a kick drum note (the "slap") are in the mid-range frequencies and are reproduced by the bass-mid-driver or mid-range driver.

If the bass note fundamental frequency that follows comes from anywhere but near the bass-mid driver or mid-range driver, then the note will not be reproduced correctly.

If a bass note's fundamental frequency excites a standing wave bass boom, it will be typically be +3 to +6dB louder than the musician intended (+6dB is subjectively twice as loud for bass under 50Hz.), so the note will not be reproduced correctly.
.
.
.
.
The only data I have examining whether or not there is a loss in perceived bass impact from scattering the subs (as opposed to placing them next to the main speakers) is my own listening. I don't like to cite myself as a source and then ask you to take my word on faith alone. Especially given what you've uncovered about my family's rich genetic diversity.

RG
I've been experimenting with one vs. two subwoofers and different subwoofer locations in my room for 20 years.

Here's my conclusion:
One subwoofer parametrically equalized for my seating position sounds better than any one, two or three unequalized subwoofers in any locations I've ever tried.

The results are not even close in my room.

Richard BassNut Greene
Subjective Audiophile 2007

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---