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#1
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
Hello everyone,
After I installed a single Rel subwoofer into my system I realized that it would be in phase with one speaker and not with the other. I explain: My room is just a bit more then 4000 cubic-feet, L shaped. I set the subwoofer into the left corner behind the left speaker (Unfortunately this is the only option I have). So, I measured the frequency response of each front speakers with an real-time analyzer and I found out that when the phase of the subwoofer is set to 0 the right speaker's mid-bass frequencies decrease the output considerably. When I switch the sub's phase to 180 the left speaker's mid bass portion is sucked in. I checked the wiring, all matches red-to red, black to black. I thought... maybe I should reverse the polarity of one of the mains to even up with the sub, but that would screw up the phase between the two mains. Is there any solution? Is the distance between sub and mains the cause of this phase 'disparity"? Any input would be greatly appreciated. Thank you. |
#2
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
On Nov 12, 6:52 pm, fid wrote:
After I installed a single Rel subwoofer into my system I realized that it would be in phase with one speaker and not with the other. What you are writing is that your satellite speakers are out of phase with each other? Otherwise, how could the SW be out of phase with one- or-the-other and *not* both? A couple of questions: a) Does the SW have an internal crossover such that it does not feed full-spectrum to the satellites? This would seem pretty obvious, but I have to ask. b) Have you tried (temporarily) placing the SW somewhere else and measuring the results? Perhaps equi-distant and similar attitude towards both satellites? You may be getting "cancellation waves" for lack of a better term - which makes no sense if there is a good crossover in the SW. *IF* there is a crossover and *IF* it is adjustable, raise the cut-off frequency to the satellites and see if that does not solve your problem. One last problem that is unusual but certainly possible especially in rooms with hard parallel surfaces. Are you aware of the concept of a "standing wave"? Try setting your speakers asymetrically about the room and remeasuring. You may have to try various configurations before you determine what gives you the best results. But, keep in mind your initial statement as-written is questionable, as properly connected speakers will always be in phase with each other, all things being equal (no deliberate alterations made). Peter Wieck Wyncote, PA |
#3
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
I'd like to mention also that the odd thing is that the Relsubwoofer's
crossoveris set to 22hz. why would it affect the mid bass? |
#4
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
Peter Wieck wrote:
On Nov 12, 6:52 pm, fid wrote: After I installed a single Rel subwoofer into my system I realized that it would be in phase with one speaker and not with the other. What you are writing is that your satellite speakers are out of phase with each other? Otherwise, how could the SW be out of phase with one- or-the-other and *not* both? A couple of questions: a) Does the SW have an internal crossover such that it does not feed full-spectrum to the satellites? This would seem pretty obvious, but I have to ask. b) Have you tried (temporarily) placing the SW somewhere else and measuring the results? Perhaps equi-distant and similar attitude towards both satellites? You may be getting "cancellation waves" for lack of a better term - which makes no sense if there is a good crossover in the SW. *IF* there is a crossover and *IF* it is adjustable, raise the cut-off frequency to the satellites and see if that does not solve your problem. One last problem that is unusual but certainly possible especially in rooms with hard parallel surfaces. Are you aware of the concept of a "standing wave"? Try setting your speakers asymetrically about the room and remeasuring. You may have to try various configurations before you determine what gives you the best results. But, keep in mind your initial statement as-written is questionable, as properly connected speakers will always be in phase with each other, all things being equal (no deliberate alterations made). Peter Wieck Wyncote, PA first off thank you for your reply. I must apologize for not being specific in my question. the two main speakers are full range, five drivers floorstanders, rated to 22hz. the rel stadium III subwoofer is connected with the typical neutrik cable. in paralel (high level?), the crossover setting is 22hz, which is what bugs me... the reason I have the sub is to complement only the last octave of the sound spectrum. I still get this strange mid bass suckuout problem in one of the two speakers whenever the sub is activated and dependently from the phase setting, 0 or 180, the L or R speakers will be affected. the mains are in phase with each other. I checked the connections several times. unfortunately the system is located in an L shaped living room. one speaker seats in the corner with the sub behind, and the other speakeris in the open, meaning that it does not have a side wall and associated reflections. just the wall behind. I cannot move speakers around, they are heavy and the living room is saturated with objects and furniture. my question is: why the subwoofer appears to be in phase with one speaker only -while the two mains are in phase with each other? Is phase problrem directly proportional to the distance between sub and speakres? I say that because one speaker is definitely closer to the sub then the other. however I could easily live with this "problem", I would like to understand why that happens. thank you. also I must apologize for my english. |
#5
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
Your english is just fine - better than most anyway.
Please note the interpolations. You may need to try some temporary measures to eliminate some possibilities even if you do not find a complete solution. I must apologize for not being specific in my question. the two main speakers are full range, five drivers floorstanders, rated to 22hz. the rel stadium III subwoofer is connected with the typical neutrik cable. in paralel (high level?), the crossover setting is 22hz, which is what bugs me... the reason I have the sub is to complement only the last octave of the sound spectrum. I still get this strange mid bass suckuout problem in one of the two speakers whenever the sub is activated and dependently from the phase setting, 0 or 180, the L or R speakers will be affected. This really does sound like you are getting cancellation waves. What happens is that the output from one speaker cancels the output from another - almost as if you were to have two different individuals wave a loose rope between them different frequencies. It is possible that the distance between the two speakers and their distance from the SW is some multiple of those midrange frequencies that are being cancelled, which would also explain the R/L phenomenon. the mains are in phase with each other. I checked the connections several times. OK - that has been established. However, is there something about the internal crossovers within the speakers that affect the phasing? Are the mids set up differently than the woofers? What brand of speakers are these? I know that the AR9, for example, had side-firing woofers - something like this is important to know when setting up the speakers. unfortunately the system is located in an L shaped living room. one speaker seats in the corner with the sub behind, and the other speakeris in the open, meaning that it does not have a side wall and associated reflections. just the wall behind. I cannot move speakers around, they are heavy and the living room is saturated with objects and furniture. This will be a problem. True full-range, standard driver speakers absolutely *DO NOT* like corners, and all sorts of crazy thing happen when they are forced into one. This could also be the cause of a standing wave that would explain what is happening to you. my question is: why the subwoofer appears to be in phase with one speaker only -while the two mains are in phase with each other? Is phase problrem directly proportional to the distance between sub and speakres? I say that because one speaker is definitely closer to the sub then the other. See "standing wave" above. http://www.asc-hifi.com/articles/ht2.htm http://www.psaudio.com/articles/settingupastereo.asp There is a lot of good information out there on standing waves, and a lot of bad information as well. Suffice it to say that you need to understand what they are and what they mean, you *do not* have to go out and purchase a bunch of expensive tripe to deal with them. That can be done with some clever care on your part. however I could easily live with this "problem", I would like to understand why that happens. *TEMPORARILY*, you may need to experiment with speaker placement. See if placing the SW in the middle of the floor, for instance, about 1/3 - 2/3 between the main speakers, and at least 4 woofer-diameters in front of them, firing away from them does not alter the response or cure the problem. Try moving (again temporarily) the speaker out of the corner and try moving both away from the back wall (by at least one woofer diameter). All of these things are to determine whether you have an electrical problem (phasing) or a placement problem (cancellation/standing waves). There are ways to deal with wave issues, but they may be disruptive to your decorating. As a complete aside, you are not by any means the first person to deal with this issue. One of the major pioneers in speaker design and contributors to the audio world, Roy Allison, designed an entire line of speakers in recognition of real-world placement problems. A brief article on it may be found he http://www.stereophile.com/interview...ur/index2.html He and Edgar Villchur worked together for years at AR. Good luck and let us know. Peter Wieck Wyncote, PA |
#6
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
fid wrote:
I must apologize for not being specific in my question. the two main speakers are full range, five drivers floorstanders, rated to 22hz. the rel stadium III subwoofer is connected with the typical neutrik cable. in paralel (high level?), the crossover setting is 22hz, which is what bugs me... the reason I have the sub is to complement only the last octave of the sound spectrum. I still get this strange mid bass suckuout problem in one of the two speakers whenever the sub is activated and dependently from the phase setting, 0 or 180, the L or R speakers will be affected. the mains are in phase with each other. I checked the connections several times. unfortunately the system is located in an L shaped living room. one speaker seats in the corner with the sub behind, and the other speakeris in the open, meaning that it does not have a side wall and associated reflections. just the wall behind. I cannot move speakers around, they are heavy and the living room is saturated with objects and furniture. my question is: why the subwoofer appears to be in phase with one speaker only -while the two mains are in phase with each other? Is phase problrem directly proportional to the distance between sub and speakres? I say that because one speaker is definitely closer to the sub then the other. however I could easily live with this "problem", I would like to understand why that happens. aside from positioning the equal distance from your L/R front speakers, you might want to consider running 2 subs; see: http://www.harman.com/wp/pdf/multsubs.pdf bill |
#7
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
fid writes:
Hello everyone, After I installed a single Rel subwoofer into my system I realized that it would be in phase with one speaker and not with the other. I explain: My room is just a bit more then 4000 cubic-feet, L shaped. I set the subwoofer into the left corner behind the left speaker (Unfortunately this is the only option I have). So, I measured the frequency response of each front speakers with an real-time analyzer and I found out that when the phase of the subwoofer is set to 0 the right speaker's mid-bass frequencies decrease the output considerably. When I switch the sub's phase to 180 the left speaker's mid bass portion is sucked in. I checked the wiring, all matches red-to red, black to black. I thought... maybe I should reverse the polarity of one of the mains to even up with the sub, but that would screw up the phase between the two mains. Is there any solution? Is the distance between sub and mains the cause of this phase 'disparity"? Any input would be greatly appreciated. Thank you. You didn't mention what the cutoff frequency is of the subwoofer's crossover. Is it 80 Hz? 120 Hz? 200 Hz? The wavelength of a frequency f is about 1100 / f [ft]. So if the highest frequency in your subwoofer's output is 100 Hz the wavelength is about 10 feet. At that frequency, a distance difference of 5 feet will correspond to 180 degrees out of phase. Of course it's not black-and-white either - a distance difference of 4 feet will attenuate the signal somewhat but not completely (theoretically). So, if you're getting unwanted cancellations in the "mid-frequencies" I'd say the best thing you could do is lower the crossover frequency of the sub, down to maybe 60 to 80 Hz. -- % Randy Yates % "She has an IQ of 1001, she has a jumpsuit %% Fuquay-Varina, NC % on, and she's also a telephone." %%% 919-577-9882 % %%%% % 'Yours Truly, 2095', *Time*, ELO http://www.digitalsignallabs.com |
#8
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
fid wrote:
I'd like to mention also that the odd thing is that the Relsubwoofer's crossoveris set to 22hz. why would it affect the mid bass? You would be better off if you set the cutoff of your main speakers above 100 Hz and fill in with the sub. Keep in mind that the crossovers are NOT a sharp cut off. At 12dB/octave there is still considerable energy at several octaves away from the crossover. Your phase problems are because of the distance between the speakers. ---MIKE--- In the White Mountains of New Hampshire (44° 15' N - Elevation 1580') |
#9
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
fid writes:
Peter Wieck wrote: On Nov 12, 6:52 pm, fid wrote: After I installed a single Rel subwoofer into my system I realized that it would be in phase with one speaker and not with the other. What you are writing is that your satellite speakers are out of phase with each other? Otherwise, how could the SW be out of phase with one- or-the-other and *not* both? A couple of questions: a) Does the SW have an internal crossover such that it does not feed full-spectrum to the satellites? This would seem pretty obvious, but I have to ask. b) Have you tried (temporarily) placing the SW somewhere else and measuring the results? Perhaps equi-distant and similar attitude towards both satellites? You may be getting "cancellation waves" for lack of a better term - which makes no sense if there is a good crossover in the SW. *IF* there is a crossover and *IF* it is adjustable, raise the cut-off frequency to the satellites and see if that does not solve your problem. One last problem that is unusual but certainly possible especially in rooms with hard parallel surfaces. Are you aware of the concept of a "standing wave"? Try setting your speakers asymetrically about the room and remeasuring. You may have to try various configurations before you determine what gives you the best results. But, keep in mind your initial statement as-written is questionable, as properly connected speakers will always be in phase with each other, all things being equal (no deliberate alterations made). Peter Wieck Wyncote, PA first off thank you for your reply. I must apologize for not being specific in my question. the two main speakers are full range, five drivers floorstanders, rated to 22hz. the rel stadium III subwoofer is connected with the typical neutrik cable. in paralel (high level?), the crossover setting is 22hz, which is what bugs me... the reason I have the sub is to complement only the last octave of the sound spectrum. I still get this strange mid bass suckuout problem in one of the two speakers whenever the sub is activated and dependently from the phase setting, 0 or 180, the L or R speakers will be affected. the mains are in phase with each other. I checked the connections several times. unfortunately the system is located in an L shaped living room. one speaker seats in the corner with the sub behind, and the other speakeris in the open, meaning that it does not have a side wall and associated reflections. just the wall behind. I cannot move speakers around, they are heavy and the living room is saturated with objects and furniture. my question is: why the subwoofer appears to be in phase with one speaker only -while the two mains are in phase with each other? Is phase problrem directly proportional to the distance between sub and speakres? I say that because one speaker is definitely closer to the sub then the other. however I could easily live with this "problem", I would like to understand why that happens. thank you. also I must apologize for my english. Mike's point about the crossover slope being 12 dB/octave is very relevent, although I'm not sure we can conclude that is the slope of the Stadium IIIs' crossover. I would also add that this problem is exacerbated if you have the level of the sub pumped up so that "0 dB" of the sub is higher than "0 dB" of your mains. Regardless of where your level is now, reducing it is sure to improve the cnacellation problem, but of course it will reduce the low bass energy as well. You mention the furniture and speaker weight problems, but just in case you've got a conceptual error, ideally all the speakers should be positioned at the same distance from the listening position. The distance from the sub to the mains is not what's important - rather, the difference in distance between sub-to-listener and mains-to-listener. This difference should ideally be 0. I see only two alternatives: 1) rearrange things so that the speakers all lie at the same radius from the listener, or 2) add a crossover system that will roll off your mains and or your sub (or both) more agressively. -- % Randy Yates % "The dreamer, the unwoken fool - %% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..." %%% 919-577-9882 % %%%% % 'Eldorado Overture', *Eldorado*, ELO http://www.digitalsignallabs.com |
#10
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
Thank you for your replies and suggestions. Finally I start to
understand something... They are indeed side-firing woofers -Vienna Acoustics Mahlers. These woofers work in the range from 70hz all the way down to 22hz. They are set as full range just like Rel suggests, high level crossed over at 22Hz just to increase of the last octave. For what I understand from the manual the speakers and the sub work simultaneously to reproduce sound from the crossover point down. This way is preferable to me because the sub is working in both high level and low level in the same time. Having one of the speakers in the corner with its woofer facing outside, it fires directly to the sub and the sidewall. That created a number of problems as I mentioned before. Now, I reversed the speakers with the woofers facing each other, and it appears that the two speakers, measured individually, have a similar (not quite the same ...but it is an improvement) frequency response. However, that reversing created another problem with is a decrease of energy in the range of 80hz. I do have a pair of quality Audiocontrol mono equalizers that through them I boost that frequency a little. But the reason I installed these two EQ in the first place was to tame an enormous peak at 31hz and 40 hz. I lowered the slides of the EQ all the way to cut down that peak, and still it is a bit more that I would like, but without the EQ would have been too much. Obviously I have standing waves bigger than I can handle. If I increase the sub level even at the lowest crossover setting it will increase proportionally also those peaks. I understand that moving the speakers around would change things, but my living room is cluttered, that's why I need to learn alternatives, if there are any. I never thought that this hobby would drain so much energy... Thanks again for your help. |
#11
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
In article , fid
wrote: Thank you for your replies and suggestions. Finally I start to understand something... snip Obviously I have standing waves bigger than I can handle. If I increase the sub level even at the lowest crossover setting it will increase proportionally also those peaks. I understand that moving the speakers around would change things, but my living room is cluttered, that's why I need to learn alternatives, if there are any. The bass energy in a room is much harder to tame than treble, and increasing it by using sub-woofers makes room dynamics more critical. IMO the best way to tame resonant frequencies (either reinforcements or cancellations) is by shifting speakers and furniture. Standing waves depend on the shape and size of the room as well as the use of large furniture to break them up or absorb bass. Sound in general does not respond well to speakers in corners, this gives great reinforcement to bass frequencies. I prefer to block the corners with chairs, book cases, etc. As sound leaves a speaker, it spreads out depending on the frequency. High treble beams almost straight out in a narrow path, often only 10 or 15 degrees wide. Lower bass goes around corners easily and will leave the vicinity of the speaker in almost 360 degrees. So putting your speakers in the corner reinforces the bass up to 4 times with reinforced frequencies dependent on the distance to the side and rear walls (as well as to the floor and ceiling). There used to be a good computer program (BestPlace) that calculated all these reinforcements. Taming the bass, and the reflections of all frequencies from flat hard surfaces, does mean rearranging, but changing room acoustics does make for dramatic differences. Have fun. Greg |
#12
Posted to rec.audio.high-end
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Subwoofer in phase ...with only one speaker
On Nov 17, 8:56 pm, Greg Wormald wrote:
In article , fid wrote: Thank you for your replies and suggestions. Finally I start to understand something... snip Obviously I have standing waves bigger than I can handle. If I increase the sub level even at the lowest crossover setting it will increase proportionally also those peaks. I understand that moving the speakers around would change things, but my living room is cluttered, that's why I need to learn alternatives, if there are any. The bass energy in a room is much harder to tame than treble, and increasing it by using sub-woofers makes room dynamics more critical. IMO the best way to tame resonant frequencies (either reinforcements or cancellations) is by shifting speakers and furniture. Standing waves depend on the shape and size of the room as well as the use of large furniture to break them up or absorb bass. Sound in general does not respond well to speakers in corners, this gives great reinforcement to bass frequencies. I prefer to block the corners with chairs, book cases, etc. As sound leaves a speaker, it spreads out depending on the frequency. High treble beams almost straight out in a narrow path, often only 10 or 15 degrees wide. Lower bass goes around corners easily and will leave the vicinity of the speaker in almost 360 degrees. So putting your speakers in the corner reinforces the bass up to 4 times with reinforced frequencies dependent on the distance to the side and rear walls (as well as to the floor and ceiling). There used to be a good computer program (BestPlace) that calculated all these reinforcements. Taming the bass, and the reflections of all frequencies from flat hard surfaces, does mean rearranging, but changing room acoustics does make for dramatic differences. Have fun. Greg Greg: All good stuff. Fid: There is one quick-and-dirty expedient you can try to help focus on the direct causes of your problem without ripping your room apart. Obtain a square piece of 3/4" (20mm) plywood or MDF with its main dimension about 1.25 x the diameter of the main speaker woofers. Line both sides of it with either a deep-pile carpet or a dense foam rubber. Make it on a stand so that you can put it somewhere and it will stand vertically without additional support. Place it at several points adjacent to your SW or main-speaker woofers or between them and see how/if anything changes. It is just a baffle to break up the sound waves and give you an idea of what is going on. Best of luck with it. You may have to defer to the Decorator Entity in your household and beg for a Dispensation to get things moved about. Been there, done that. A pair of AR9 speakers went by the wayside as they simply *did not fit* into the room in such a way as to be tolerable for listening. The pair of 3as fit nicely but are of a very different nature. Peter Wieck Wyncote, PA |
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