I think you have a difficult room where the bass traps do not suppress its resonant modes adequately. Wiring the woofers out of phase causes their bass sound waves to cancel each other out, resulting in reducing all your bass sound, including the unwanted resonances. I think you would be better off with a room analysis and an equalizer treatment that specifically reduces the resonant frequencies while leaving the nonresonant frequencies alone. There are systems that do this, like Rives, TacT, or even Behringer.
22 responses Add your response
At least one researcher in the field of subwoofer/room interaction recommends using two subwoofers operated 90 degrees out-of-phase with each other. I have used subs operated 180 degrees out of phase with each other at times. It offends one's notion of order and symmetry but can sound very good.
You may even get in increased sense of spaciousness from the out-of-phase configuration. And the bass isn't reduced as much as you would have thought, is it?
You are right, in that I am satisfied with the amount of bass I am getting in out of phase mode. Also there is considerable more space and dynamics. What nags me is whether or not this is the way to solve the problem. I got this idea from owning a Rel sub where they suggest in hooking up the sub out of phase which may reduce bass boom. By the way I am not currently using the sub in my system. I thought about using an EQ like Rives, but maybe I would get the same results.
What nags me is whether or not this is the way to solve the problem. I got this idea from owning a Rel sub where they suggest in hooking up the sub out of phase which may reduce bass boom.
Of course it is not correct - you are changing the impulse response significantly. This may be why it sounds more spacious...probably more laid back - less distinct on transients or muddy. The inteference pattern that you create will have a null down the center line of the room (if it is symmetric). A better solution would be tone control or PARC or placement further out into the room. Electrostatics are designed to be placed well out in to a room (less bass reinforcement) and therefore it seems likely that ML's will bass heavy if placed up against a wall.
My room dimension is 13x30. I have the speakers set up on the short wall. The speakers are 5 feet out into the room and 2 feet from the side walls. Listening chair is 9 feet from the center plane of the speakers. The floor is concrete with double wall construction. My ceiling slopes from 10 feet to 7 feet from left to right. Carpeted in the seating area bare painted floor in the speaker end. Perhaps then my only solution will be to applied some sort of EQ in the low freq.region. Thanks guys for your input.
Interesting that you find that it sounds better with the woofers out of phase, in as that back in the early '90s, when Stereophile reviewed the Martin Logan Sequel IIs, that they too found that if they wired the woofer out of phase, that it too sounded better.
Thought you might find that interesting.
The ear literally responds slowly at very low frequencies. We cannot hear less than 1 cycle at very low frequencies, and by the time 1 cycle has reached us enough time has elaped that we're past the direct sound and into the reverberant sound. Unfortunately I don't know the (probably fuzzy) cut-off point for this phenomenon. But it can be said that from the standpoint of psychoacoustics, there is no "direct sound" in the deep bass; at least not in the size rooms we typically have at home.
The increase is spaciousness is probably somewhat artificial because very few recordings actually have stereo information below 80 Hz. The ear interprets a low-frequency phase difference at each ear as a sign of very large acoustic space, and that is what is being synthesized by reversing the phase of one of the woofers. Out-of-phase subwoofers placed to the extreme left and right of the listening position will maximize the interaural phase difference and hence the simulated sense of spaciousness. David Griesinger, inventor of the Lexicon processor, advocates this technique.
Shum3s...hold yer horsies fella!! Funny how the obvious escapes most people, but not this here audiophile..no sir. What ya gotta do is move them pesky speakers to the long wall and sit within 18" of the opposite wall. Spread them out real good..10 to 12ft, and bring em out by ear until you achieve the best darn response you can get! Also, sit with yer ears below 36", and treat the front and back walls with acoustic material (natural nor not). You cannot decide where you will sit and place speakers...the room and the speakers decide, otherwise get a Bose radio.
We cannot hear less than 1 cycle at very low frequencies, and by the time 1 cycle has reached us enough time has elaped that we're past the direct sound and into the reverberant sound
I agree fully with that.
I guess what sounds best to your own ears is the right thing to do...
If you are listening to a bass guitar or double bass then I agree that phase has very little to do with the way the notes sound.
However the fact that the bass sounds more spacious with one speaker woofer wired incorrectly seems to me to imply that there is enough energy in the upper bass (perhaps above 80 Hz) to give some rough directional information to the ears - surely this must affect presentation or the way transients sound - like a Kick drum where the slap comes at 4 or 5 Khz and bottom at 60 to 80 HZ?. By this I mean coudl it change the perceotion of fast bass versus slow bass.
I would dig out the Sheffield Labs Drum test Track 1 and check to see which sounds better/more realistic (disregarding the overly heavy bass presentation by using a tone control for example). Just a thought....
Here is and example of the funky relationship between bass mid and treble and the way we perceive instruments
The jargon is an interesting mix of descriptive words to describe how something sounds coupled with the frequencies that are driving that sound. I would be concerned with changing teh way thing sound through incorrect phase....it may not sound that much wrong but it may sound different.
From what I gather from you the experts I should wire the woofer in phase and look into finding what frequencies are giving me trouble; then use some type of EQ to take care of the bass nodes. I wonder if my wife will get me a Rives prac for Christmas? Stay tune, I will let you know how this will all work out. Thanks- Sam
One other comment relative to in-room bass smoothness: Note that fullrange dipoles have smoother in-room bass than monopoles (James M. Kates, "Dipole Loudspeaker Response in Listening Rooms", JAES May 2002). A single dipole may be thought of as two monopoles out of phase with each other. I think there's some merit to the idea of playing around with driver phase in the deep bass region.
The practical issue that I am face with is the fact that when the woofers are out of phase the bass response in my room is very smooth, no bloat. There seems to be greater detail in the upper frequencies. The center fill is very stable and the sound stage seems more open. All in all I like what it does, the question is, if I invest in a Prac, will I end up at the same place i.e. smooth base. Maybe I can demo one to know for sure.
So you've achieved a pleasing speaker coloration. There's a real chance that "correct" bass will not sound as pleasing. If this were the midrange or the highs, I would say that you might become more aware of the coloration as you play more material and you would ultimately become tired of it. This might not be the psychoacoustic conclusion for bass, however. It's an intellectual choice, pleasing coloration or accuracy.
Look, my humor aside...think about it..a 13 by 30 room?? The speakers themselves need at leats 10 t0 12 feet between them. Use the long wall and sit against the opposite side wall..your problems will go away!! Call Terry at Mapleshade for advice or check out the free tweaks section on the web site. Almost all reputable speaker manufacturers will tell you the same thing as I have...long wall, head against opposite wall, treat front and back walls, sit low and spread speakers apart with minimal toe in. You just might find yourself immersed in a complex musical soundscape...of course you may want to listen to someone with less experience. By the way, put the sub on proper spoked or coned feet, face it left or right (not in a corner or down firing) and put it in the plane of the midrange drivers. Use the best cable or IC connection you can and put a good power cord on it of possible. Enjoy!!
I am assuming that BOTH speaker systems are being wired with woofers out of phase.
First, some crossover networks, having a 180 degree phase shift between woofer and tweeter, require that the two drivers be connected with opposite electrical phase. Some other networks having 90 degree phase shift, are "wrong" (electrically) no matter what you do.
If one connection (chosen by the designer) yields flat response through the crossover frequency, then inverting one driver will cause a deep notch at the crossover frequency. (In fact this is the best way to measure the crossover frequency). Perhaps your room has a resonant peak around the X/O frequency, or, more likely, you just don't like that frequency.