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I'm close to dialing in a pair of powered subs & have a question regarding the Phase of the subs.Both subs are about 5' behind my speakers, in the corners of the room, directly behind the speakers. To me they sound great in this location, much more of a 3-d effect and the subs disappear. With the subs just behind the speakers the performance was OK...but i like the corner spots best.
They have been in this location for about a week, and the subs are a month old. last night i flipped the phase from 0 degrees to 180 degrees and a big, big change occurred. the subs completely disappeared, the bass output seems to be less YET the 3-D effect is huge now. imaging, separation & the scary airy effect is REALLY wild now.
from what i've read, setting the subs out of phase is important if the listener or the speaks are far from the subs. Is 5' away considered far? from my chair the speakers are 10' from me & the subs are about 15' away.
and, is what i'm hearing when i go from 0 to 180 what is supposed to happen?
With them at 180 i get the feeling like more deep bass should be present...but the overall effect is much more interesting this way. The chest thumping went way down, but the imaging improved 10 fold.
With them at 0 degrees, they sound like subs i've had before. With them @ 180, its really wild but NOT in a party boom-boom way. Its a musical/audiophile 'come see the symphony in my L/R' effect.
With the subs @ 180 degrees, there is NO center image. everything & everyone has its own spot on stage. With them at 0 degrees, the lead singer is almost always directly in front of me. Not knowing squat, i've always figured there shouldn't be a direct center musician...but until last night I had not heard a presentation like this.
sorry for the babble, hard to explain this stuff sometimes...
Follow Ups:
When i 1st purchased these subs, Pual Grzybek told me to install cable jumpers between the positive sp terminals of both channels on each subs amp...i never did that. last night i had time & cut up 2 small lengths of anti-cable and began bending them into place. Installing these & setting both subs back in phase has made a huge difference. I judge all speaker posts now by their ability to hold 2 loops of bare solid core 12ga. anti-cable securely! not an easy task...I think the change i heard when switching both subs out of phase was simply a reduction in bass...I was listening to the main speakers alone & forgot how good they sounded. Plus the recent addition of a mapleshade 4" platform under my TT is still new & wild.
Once i move in a few months i will get a Behringer DEQX & calibration mics for sure. For now, the simplicity is working & having the subs a few feet behind the speakers (in each corner) works the best.
the budget subs I bought are badass - with a little tweaking. At some point i'll get better ones when the budget allows, but at least this way i'm not out major $ but i've got incredible sound. All i want different now is a remote control that controls both subs...that would be a dreamy.
thanks again you guys!!!!
Male vocals rarely get below 80Hz.Subwoofers usually sound their best when you hear absolutely no male vocals through them when the other speakers are turned off.
Subwoofers usually sound better when they are near the main speakers (or closer to your ears) rather than many feet behind the main speakers.
You may want to experiment with lower crossover frequency settings and placing your subs next to, or behind, the main speakers.
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Richard BassNut Greene
Subjective Audiophile 2007
Due to distance your subs lag 128 degrees at 80Hz and 64 degrees at 40Hz.Minimum-phase low-pass functions have phase lag and high-pass functions phase lead. This holds whether the functions come from electrical or mechanical effects - phase lead increases with decreasing frequency from every loud speaker driver + enclosure combination in the world. An electronic all-pass filter can compensate for this with phase lag that decreases with increasing frequency).
IOW, phase inversion could put your mains and subs back in phase or out of phase where they have overlap. You really need to measure.
If you really want your sub-woofers and main speakers to integrate well you need complimentary acoustic cross-over slopes (magnitude and phase).
Having read both of your posts and assuming that you are not feeding your main speakers through a high-pass filter (i.e. they are allowed to reproduce the full spectrum of the input signal), I would say you are attempting the impossible.The problem is that the Thiels I'm sure reproduce flat to at least 40 Hz and somewhere between 40 and 50 Hz is your primary room resonance, which can add 10 dB or even more to the response. And the low pass on your subs is limited to 50 hz and above. The reason that REL gets away with this kind of a setup (i.e. running the mains full range, rather than through a high pass filter) is that the REL low pass adjusts all the way down into the 20Hz range. Most other subs can only be used this way with small standmount speakers, almost none of which develop significant output below 50 Hz.
There is no other brand of sub that I know of that does this, other than the Velodyne digital drives, which have a built-in parametric equalizer.
So, by flipping the polarity switches on your subs, you are alternating between destructive interference in the 40-50 Hz bandwidth, which will suppress the perceived bass level in that frequency band, or additive bass there which will probably be overwhelming (unless you throttle the subs way back).
Having the subs 180 degrees out of phase with each other is a real bad idea; so don't even consider it. Better to give them away than do that.
My suggestion would be to buy a Behringer digital RTA/Equalizer (they're only a few hundred dollars) including the calibrated microphone. (The Bass Nut gave me that idea several years ago.) If you're patient, one will come up for sale on Audiogon (which is where I got mine). This will allow you to match your subs (in-phase with the mains, please) to the bass output of your main speakers and it will compensate for the room resonance. The most that you may have to do is move the Thiels farther away from walls, etc. to reduce their bass output in the critical 40-50Hz region, since the Behringer will not be equalizing the drive to the Thiels, but only to the subs.
The Bheringer unit is a stereo unit, so you can equalize for each subwoofer separately, to account for the difference in placement. With the calibrated microphone, the whole operation is automatic and takes just a few minutes.
I have one of these, and it is money very well spent.
Velodyne sells a similar unit that is much easier to use than the Behringer, but also is more expensive (around $700) and is single-channel.
I was thinking of one of those for my own room. A friend of mine picked one up and I got a tour of it. It worked great. If it is single channel, I guess it is off my list. I feed stereo input into the sub.After trying the Velodyne, I measured my family room's response just using Arta, and was surprised at the large 40Hz bump. My speakers, at the time, had an F3 of just about 40Hz in room. I am now experimenting with on-wall speakers but these only go down to about 55Hz.
For what it's worth, my active sealed B&W sub can be crossed over down to 40Hz which helps out some. I cross mine over at 45Hz at the moment but equalization is necessary here.
n/t
I like how it worked in my friend's setup. I was going to check it out more closely next time I came by anyway.
excellent post. the main speaks are running full bore, you are correct.I have thought about getting a Behringer eq but hated the idea of having a digital piece when i mainly listen to vinyl. But you're suggestion is to have it for the subs only...that is doable. is there a specific model?
i would not ever run them out of phase of one another. both switches are set one way or another. both give quite a difft effect.
The floorstanders are away from all walls, a benefit to having a G shaped room - the heel of the L is bumped back 6'...forming a G and the 4th corner in the room (where 1 sub is) is only 7' long and at a 45 deg angle. highrise condo.
they probably go below 50hz, but i can set them up with spikes & they growl much lower. with 'em unspiked, on the carpet & way out in into the room they don't play very low...but sound dope.
still have to read other responses, but thanks for the time spent.
Audio-video logic is selling the Velodyne product at a discount -- $600.00 Link: http://cls.audiogon.com/cgi-bin/cls.pl?misceqal&1179166638Other link below is to the current Behringer product, which lists at $380. You'll have to buy the calibrated microphone and a long cable; I believe Behringer sells both.
IIRC, I bought the predecessor product used on audiogon for about $200, including the microphone and cable.
The calibration is not perfect because, for calibration purposes, you have to insert the equalizer in the signal path between the preamp and main amp as well as between the preamp and the subs. Then, once you operate, you take the equalizer out of the path between the preamp and main amp. If you don't want to leave the equalizer in the signal path for your main amp, and you want to be more precise in your equalization, you can equalize maunally, using a CD with pink noise on it as a sound source and the equalizer's RTA to adjust for a flat output into the room.
The phase switch is there to help you minimise any cancellation at frequencies covered by both the sub and the main speakers. The correct position is whichever is the louder.Sub settings are tricky, however, and crossover frequency and gain settings also affect the result. In the manual for my REL, it states that people tend to set crossover frequencies too high and the gain setting too low. I definitely did both of those in my early days with the REL in my audio system.
It's hard to give advice as to what should be the correct frequency because it depends on whether you're running the main speakers full range with the sub blending in under them, or using an active crossover setup of some kind to split frequencies between the sub and the mains. The gain setting depends on the decision between those 2 options also, if they are options for you. In some systems/with some subs you don't have a choice and it will have to be one or the other.
I think there's something wrong when you have the subs 180 degrees out of phase. Singers are usually centred in the soundstage, not always but it is definitely the usual presentation for singers. If you're losing that on all recordings then soemthing isn't right. That would indicate that since you lose that but like other things more when the subs are out of phase, then either phase setting is going to be a compromise and the best result may be somewhere between them. Some subs do provide a complete 360 degree phase adjustment and that is definitely better than a simple in/out of phase switch which is all that my sub has. When what you have is a choice between 2 options, with each having different strengths and weaknesses, you pick the one which suits you best overall. There's really no other choice.
You may find that you can get better results with one sub in phase and the other out of phase. Room asymmetries and other things can certainly affect that. Try putting one sub back in phase and see what that does, then swap it out of phase and put the other out of phase. You really have 4 options here: both subs in phase, both out, A in phase and B out, and A out of phase and B in. Go for whatever sounds best overall.
But do try lowering the crossover setting and playing with the gain also.
You are probably getting some cancellation at the overlap of the speakers and the sub. The lowered bass in this region is bringing out the other frequencies which may have been masked. Do you have a way to measure your bass response?My guess is that your sub is actually a tad loud or crossed over too high so the dip from the out of phase condition is fixing that issue.
My rule of thumb is that the setting where there is the most bass is where the speakers and subs are the closest in phase so this is the one I choose.
You may need to just keep the sub in phase, lower the subwoofer's crossover frequency, and possibly adjust the subwoofer level.
My next guess is that Richard BrassNut Green may come in and shred my input to pieces but that's OK as he said he would wrap his next post in bacon before shoving it down my throat. :)
Bill
thanks Schu,
I think you are onto something.... the lowest x-over point for these subs is 50HZ. i'm pretty sure my floorstanding thiels go lower, but they are just sitting on carpet & don't seem to produce the really low freq's this way.i've been trying to figure out if there's cancellation somewhere, but to my ears the entire presentation is spot on.
i don't have a way to measure it, but do know a guy with an RTA & mics if worse comes to worse. maybe i should just get a rat shack db meter & download a test CD?
well, since i can't lower the x-over frequency more, i won't lose sleep over it.
In summation, changing the Phase changes everything. More deep bass at 0 degrees but way more 3-D wildness at 180 degrees. At 0 degrees, the subs shake the floor a bit. At 180 degrees the cabinets barely vibe even though the driver acts the same, same exceursion.
to some this may seem like a preference issue, but its not.
My room is treated, and to my surprise the budget acoustic kit does not seem to be overpowered by the subs whatsoever. i don't listen at high spl's though, which is probably the real test.
neither sub is turned up more than 30% of volume. With the phase in either position, turning up past that point sounds bad, doesn't integrate as well.
RBG, please chime in if you are available...
If you use the Radio Shack meter, I heard from somebody that it is 3db down at 30Hz but rather flat until around 2Khz.You can download WinIsd which does have a tone generator built in.
Bill
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