AudioCircle
Industry Circles => GIK Acoustics => Topic started by: Atexanathome on 29 Mar 2012, 02:56 pm
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I finally got a dedicated stereo room, but when I checked out my frequency response with a Radio Shack meter, I had an 18 dB peak at 50 Hz. I purchased some GIK traps, four Tri-Corner traps behind the speakers, and a GIK 244 and Monster Bass trap behind the listening chair. I also have an Echo Buster at each first reflection point.
I just got an OmniMic, but I still have the huge 50Hz peak at the same level. As far as I can tell, the main effect of the room treatments was to roll off treble above 10 kHz and produce a suckout between 70 Hz and 110 HZ.
Do I have to go to dipole bass to fix this? The room is 10.5'X10.5'X8'. The speakers are Joseph RM33Si.
The nice thing is, the bass is only down 3-6 dB at 20Hz. At 83-85 dB at the listening position, it looks like 2nd harmonic is only about 2% at 20Hz. Not bad for 8" woofers.
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Post a picture of your room, along with the location of the mic, speakers, etc...
Calculate your modes from 10.5X10.5X8, unfortunately a square room. There are calculators online, or even as a sticky in the acoustics circle, such as Harmon Room Mode Calculator.
Post your frequency response plot on whatever piece of a software you are using. If you can include a waterfall/decay plot(s) that would help.
The Omnimic I am assuming is calibrated.
Without the above information, it becomes very difficult to advise.
Best,
Anand.
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Where are you seated in the room?
Have you looked at the decay times pre and post treatment? That's another thing that treatment will do.
The square shape isn't helping and the 70Hz issue is likely a ceiling reflection issue that hasn't been addressed.
Bryan
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You have the width and depth both working against you as they both have the same resonant frequency. So it is no surprise you have a major peak.
The Bob Gold site confirms this:
http://www.bobgolds.com/Mode/RoomModes.htm
Did you try offsetting the speakers and your seat so you are not exactly in the center of any wall? I am 6 inches to the right of center and 62% back from the front wall to try and stay out of room mode collisions.
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Okay, great minds think alike and in the same space-time continuum!
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Post a picture of your room, along with the location of the mic, speakers, etc...
Calculate your modes from 10.5X10.5X8, unfortunately a square room. There are calculators online, or even as a sticky in the acoustics circle, such as Harmon Room Mode Calculator.
Post your frequency response plot on whatever piece of a software you are using. If you can include a waterfall/decay plot(s) that would help.
The Omnimic I am assuming is calibrated.
Hello,
I used a calibrated Omnimic to get the curves below.
(http://www.audiocircle.com/image.php?id=60309)
(http://www.audiocircle.com/image.php?id=60310)
(http://www.audiocircle.com/image.php?id=60311)
(http://www.audiocircle.com/image.php?id=60312)
(http://www.audiocircle.com/image.php?id=60313)
Without the above information, it becomes very difficult to advise.
Best,
Anand.
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Where are you seated in the room?
Have you looked at the decay times pre and post treatment? That's another thing that treatment will do.
The square shape isn't helping and the 70Hz issue is likely a ceiling reflection issue that hasn't been addressed.
Bryan
Hello Bryan,
Here are some photos of the room. The last three are a little out of date.
(http://www.audiocircle.com/image.php?id=60314)
(http://www.audiocircle.com/image.php?id=60315)
(http://www.audiocircle.com/image.php?id=60316)
(http://www.audiocircle.com/image.php?id=60317)
(http://www.audiocircle.com/image.php?id=60318)
(http://www.audiocircle.com/image.php?id=60319)
Thanks
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Hey! Somebody else with Omnimic! I will be interested to see what feedback you get. I'm still trying to figure out what some of the measurements really mean. :scratch:
A couple of questions. With regard to the last two graphs, I'm guessing that those are the left and right channel frequency responses. If correct, what settings were you using? (1/3 octave thru 1/96 are available).
I noticed the picture shows your microphone mounted above the listening chair pointing down - how did you decide on this position? I ask because I know with mine, pointing it directly at the speakers and moving it just a few inches or changing the angle slightly can effect the readings. I try to place mine as close to my head's position as possible and pointing straight forward. Not sure if there is a recommended orientation, so I'm guessing.
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Hmm,I thought mikes and meters were suppose to face straight up towards the ceiling.
at least that's what I've read on other sites,now whether it makes a difference I 'm not sure.
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Hey! Somebody else with Omnimic! I will be interested to see what feedback you get. I'm still trying to figure out what some of the measurements really mean. :scratch:
A couple of questions. With regard to the last two graphs, I'm guessing that those are the left and right channel frequency responses. If correct, what settings were you using? (1/3 octave thru 1/96 are available).
I noticed the picture shows your microphone mounted above the listening chair pointing down - how did you decide on this position? I ask because I know with mine, pointing it directly at the speakers and moving it just a few inches or changing the angle slightly can effect the readings. I try to place mine as close to my head's position as possible and pointing straight forward. Not sure if there is a recommended orientation, so I'm guessing.
I tilted the mic down to get the tip approximately where my head is while listening. If I use the big tripo, the mic sticks out forward of that position.
The two frequency response curves are in stereo. The difference is the All and Blended settings. I don't see big differences in mono.
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Looks to me like you're pretty far back in the room and the Monsters are a bit high. Can either of those change?
Bryan
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Just a guess but arent the speakers way to big for the room maybe.
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18dbs yikes I thought my room was bad at 10db peak. I tried lots of things, bass traps, moving speakers, moving seat. Not much helped until I put in a high pass filter set at 60hz to my mains and ran my subs 40hz on down. Got a pretty smooth curve now
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The only way I've ever been able to tame the resonances that occur in a small square room is to set it up on the diagonal.
Nothing else works nearly as well, IME.
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brm has it right - you definitely need to have an asymmetrical arrangement. shift both speakers to the right about 6"-12" or so. then, pull the right speaker out about 6"-12" or so further from the wall than the left speaker. then adjust speaker toe-in, and relocate the listening chair for your "triangle". this should help quite a bit.
another option to consider would be to relocate the whole system so that the room is "diamond" oriented. in your pic #3, that corner would be the center spot, you could put your electronics there, and your speakers would be flanking the gear. note that even w/the diamond layout, slight asymmetry as per the first layout, will likely still be beneficial.
examples stolen from another thread, w/similar issues. room is not exactly like yours, but it will give you the idea:
showing asymmetrical layout:
(http://www.audiocircle.com/image.php?id=51523)
showing diamond layout:
(http://www.audiocircle.com/image.php?id=51522)
doug s.
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I would prefer the diamond layout. While it is not symmetric to the length and width, it is at least putting the speakers symmetric left to right with regard to the side walls so their gain and reflections will be pretty much the same and we don't run into issues with the image 'pulling' to one side as frequency shifts into and out of the boundary related phase reinforcements and cancellations.
This all assumes that we can't tweak normal seating position and speaker positions. Sometimes, one can deliberately generate a counteracting null from the wall behind the speakers that will help to offset the peak from the room width.
Bryan
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I would prefer the diamond layout. While it is not symmetric to the length and width, it is at least putting the speakers symmetric left to right with regard to the side walls so their gain and reflections will be pretty much the same and we don't run into issues with the image 'pulling' to one side as frequency shifts into and out of the boundary related phase reinforcements and cancellations.
This all assumes that we can't tweak normal seating position and speaker positions. Sometimes, one can deliberately generate a counteracting null from the wall behind the speakers that will help to offset the peak from the room width.
Bryan
the whole idea in a room of this type, is to purposely try to prewent side wall gain/reflections from being the same. imaging issues can be addressed w/absorbtion/diffusion panels. in this case, asymmetry is your friend. even w/the diamond layout, i would try to have it slightly asymmetrical. of course, you can always experiment...
another option would be to add a subwoofer or even two subs. while i know this is counter-intuitive to want sub(s) in a small room, if placed in different locations, they will smooth out the low end response.
doug s.
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I think you miss my point doug. We want to keep the LISTENER from being in the center or any modal area of the length or width of the room. A subwoofer array, yes, that can be set up asymmetrically. The mains should be set up symmetrically to the boundaries. Now, should they be symmetric to the front and sides at the same reflection distance to each other? No. But the pair to the front and the pair to the side walls should be the same or you'll never get a stable image.
The diamond layout shown above does what I'm talking about. The other one does not.
In addition, when you use multiple subs in an asymmetric fashion, as I said, that can work very well. The problem is reality. Where in a 10.5' square room is one going to put 3-4 3-4 cu ft boxes where they don't possibly cause other boundary interactions or reflections from cabinet tops in the mids and highs - not to mention simply being able to walk around the room reasonably?
Bryan
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bryan, i understand what you are saying. but, it has been my experience that, in a compromised room - like one as small as 10.5x10.5 - it is better to set up asymmetrically, to even out room nodes, then to worry about image stability. while i understand you want the listener out of any node areas, it is good to reduce the nodes, regardless of where the listener is. you can get a stable image by being somewhat nearfield, and by absorbing 1st reflection points. this has been my experience and that of others. is it perfect? no; hard to get perfection in a wery small room; everything will be somewhat of a compromise.
regarding subs; i think one or two smaller subs - could be 2cu-ft or less - would be more than sufficient. you're not looking for ultimate sub-20hz response, only enough to smooth out room nodes. this is one case where i would allow the mains to run full-range, instead of crossing them to the subs, to allow for more sources of the low frequencies...
ymmv,
doug s.
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bryan, i understand what you are saying. but, it has been my experience that, in a compromised room - like one as small as 10.5x10.5 - it is better to set up asymmetrically, to even out room nodes, then to worry about image stability. while i understand you want the listener out of any node areas, it is good to reduce the nodes, regardless of where the listener is. you can get a stable image by being somewhat nearfield, and by absorbing 1st reflection points. this has been my experience and that of others. is it perfect? no; hard to get perfection in a wery small room; everything will be somewhat of a compromise.
regarding subs; i think one or two smaller subs - could be 2cu-ft or less - would be more than sufficient. you're not looking for ultimate sub-20hz response, only enough to smooth out room nodes. this is one case where i would allow the mains to run full-range, instead of crossing them to the subs, to allow for more sources of the low frequencies...
ymmv,
doug s.
I have a pair of Velodyne HGS-10 subs and an XM-9 crossover. I'm trying to avoid using them if possible. I was trying to simplify the system and get away from the complexity I had with a combined HT/music system.
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I would prefer the diamond layout. While it is not symmetric to the length and width, it is at least putting the speakers symmetric left to right with regard to the side walls so their gain and reflections will be pretty much the same and we don't run into issues with the image 'pulling' to one side as frequency shifts into and out of the boundary related phase reinforcements and cancellations.
This all assumes that we can't tweak normal seating position and speaker positions. Sometimes, one can deliberately generate a counteracting null from the wall behind the speakers that will help to offset the peak from the room width.
Bryan
I'll trying moving the chair back in 6" increments. At 18" back the chair back is against the trap.
I noticed before that small changes have a big effect. The exact center of the room gives the smoothest resonse, though the 20 Hz level drops quite a bit. I listen to a lot of organ muusic, so some bumping up of the low bass is not all bad.
The Josephs are not the best for near-field use. Too bad, they were great in my old, larger, room.I think I might need to go with 1-meter listening distance and coax speakers. I thought about GR Research Super-V's for near field. It would look strange, like the world's biggest pair of headphones.
I can drop the traps about 8" before they cover an outlet I need.
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I have a pair of Velodyne HGS-10 subs and an XM-9 crossover. I'm trying to avoid using them if possible. I was trying to simplify the system and get away from the complexity I had with a combined HT/music system.
then simply try the relocation suggestions.
if you do wanna try your subs, (i definitely would, w/the issues you are having), while i normally believe using an active x-over w/subs is best, as it frees your main amps/speakers from seeing the lowest frequencies, in your case i would simply run the subs w/their own low-pass filters set to ~70hz, and run your speakers full-range. two reasons - 1st, your speakers' woofers are already crossed over low - 125hz - and using the marchand won't really improve their performance much. 2nd, you want low end from multiple locations in your room, to help smooth out the response. the only "added complexity" would be connecting the subs to your preamp, and plugging them in to 120vac wall outlets.
doug s.
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look at the measured frequency response plot of your speakers, according to s'phile. large peak - ~5db - right about 40-50hz. mebbe it would be beneficial to use your xm9m w/your subs, set at 50hz, and w/the damping pot turned down... :scratch:
(http://www.stereophile.com/images/archivesart/jos333fig3.jpg)
doug s.
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Well there you go. Always good to look at the speaker data too.....
Nice catch Doug.
Bryan
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I'll trying moving the chair back in 6" increments. At 18" back the chair back is against the trap.
I noticed before that small changes have a big effect. The exact center of the room gives the smoothest resonse, though the 20 Hz level drops quite a bit. I listen to a lot of organ muusic, so some bumping up of the low bass is not all bad.
The Josephs are not the best for near-field use. Too bad, they were great in my old, larger, room.I think I might need to go with 1-meter listening distance and coax speakers. I thought about GR Research Super-V's for near field. It would look strange, like the world's biggest pair of headphones.
I can drop the traps about 8" before they cover an outlet I need.
if you are wanting to try different speakers, i'd suggest getting in touch with a/c vendor aj in fla, and querying him about his sam1 speakers. at retail $1300, they might be yust the ticket for you. they are a monitor, w/built-in powered 8" woofer and passive kef coax driver. search a/c; they have gotten raves from all who have heard them.
one big a/c thread; (i understand that aj is doing some updates to the speaker, so a new one might be even better?):
http://www.audiocircle.com/index.php?topic=97955.0
website:
http://soundfieldaudio.net/
doug s.
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one last comment - first things i would try, would be re-arranging the system per my earlier suggestions. like bryan, i also believe that the diamond set-up has the best chance of success in a small room, because the walls adjacent to the speakers have less interaction at the diagonal, and you have more space behind you at the listening position. (we may disagree as to whether or not it would be best to have a symmetrical vs a-symmetrical layout, but it's easy enough to try either way.) but, simple cocking of the system per my first suggestion is obviously a lot easier to try, than setting up a diamond layout, which would inwolve completely re-arranging your room.
and, it would also be easy to try using your subs. looking for different speakers would be a last resort, if you can't get what you already have to work for you...
keep us posted w/your findings.
doug s.
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I hope all works for you . But im sticking with those speaks are way to big for that space.
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I hope all works for you . But im sticking with those speaks are way to big for that space.
it's not that the size of the speakers themselves are too big - it's the size of their bass bump at 50hz that is too big...
doug s.
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I didn't read the whole thread... sorry... but has plugging the ports been tried/suggested?
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Doug, win, lose, or draw . .
What an effort by you :thumb: :beer: :notworthy:, sincerely!
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one last comment - first things i would try, would be re-arranging the system per my earlier suggestions. like bryan, i also believe that the diamond set-up has the best chance of success in a small room, because the walls adjacent to the speakers have less interaction at the diagonal, and you have more space behind you at the listening position. (we may disagree as to whether or not it would be best to have a symmetrical vs a-symmetrical layout, but it's easy enough to try either way.) but, simple cocking of the system per my first suggestion is obviously a lot easier to try, than setting up a diamond layout, which would inwolve completely re-arranging your room.
and, it would also be easy to try using your subs. looking for different speakers would be a last resort, if you can't get what you already have to work for you...
keep us posted w/your findings.
doug s.
Hello Doug,
Thanks for the suggestions. I'd been thinking about trying the subs with crossover, but I only have 60, 80, and 100 Hz modules at the moment. Rotating everything was also considered, but I was too lazy to move the 60 lb amps, the Equitech, the LP cabinet, etc. I guess I'll have to get with it, maybe after turkey season is over.
I have to use the closet door and keep it clear because my guns are in there. At least the Omnimic makes it easy to get curves, and I'm sure they are more accurate than the RS meter.
I'll try these suggestions before going with all dipole speakers. These speakers were great in my old great room. it was over 23' long, with a cathedral ceiling, and it was part of an L-shaped space that included the dining/kitchen area.
The space was actually a little too big for the speakers;I used the subs for HT work, and I blew 4 plate amps and a driver over a seven year period. Respons with the Josephs alone was good, no 50Hz peak to speak of, and they were down -3dB at 31.5Hz, -6 dB at 25 Hz, and -10 dB at 20 Hz. I did have a big suckout at the listening position at around 60 Hz. I guess the room always has the last word, eh?
Thanks,
Jon Davis
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I didn't read the whole thread... sorry... but has plugging the ports been tried/suggested?
might be worth a try; according to s'phile, the port also has a peak at ~50hz.
doug s.
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jon d., doing the 1st asymmetrical layout won't take much re-arranging; that is certainly worth a shot at minimum. and using the marchand w/a 60hz module will also be worth trying, as it will certainly lower any peak at 50hz...
good luck,
doug s.,
awaiting some fresh wild turkey meat. :green:
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The Marchand also has a trimmer pot which allows +/- 4dB at the crossover frequency. :thumb:
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The Marchand also has a trimmer pot which allows +/- 4dB at the crossover frequency. :thumb:
yup; that's why i said earlier:
"mebbe it would be beneficial to use your xm9m w/your subs, set at 50hz, and w/the damping pot turned down..." 8)
it would likely still help even w/a 60hz x-over point...
doug s.
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might be worth a try; according to s'phile, the port also has a peak at ~50hz.
doug s.
I tried the subs, in an asymmetric arrangement, and there is definitely a difference. I'm sensitive to noise, and the HGS-10's make a low growling noise whenver they're on. It wasn't audible in my old room, but it's almost a problem here.
The good news is that the response is significantly better, as shown below. I see +/- 6 dB from 20 Hz to 15 kHz and +/- 3 dB from 165 Hz to 14 kHz, which is as high as I can hear.
The 20 -30 Hz region is always a problem because of all the LF noise from the kaolin plants in the area. I see a background of -55 dB in this region all the time.
I still see a peak at around 140 Hz, but maybe I can tweak the seating position a little more. I need to do some more listening tests, but the curve does look smoother.
Thanks for all the suggestions. I may not get to turkey hunt again until I can get rid of this kidney stone that put me in the hospital yesterday.
By the way, anyone who calls himself an audiophile needs an Omnimic. It's the best accessory I've ever purchased, and I've purchased a lot!
(http://www.audiocircle.com/image.php?id=60662)
(http://www.audiocircle.com/image.php?id=60663)
(http://www.audiocircle.com/image.php?id=60664)
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cool, glad it is coming together for you. curious - are the rm33's asymmetrical, or yust the subs? rm33's run full range, or w/marchand? still have a decent soundstage? try the diamond layout yet?
sorry to hear about the kidney stone - i have fortunately never had the pleasure, but a buddy of mine has been thru that, and he said the pain is excruciating. :o hope it passes soon! :wink:
doug s.
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cool, glad it is coming together for you. curious - are the rm33's asymmetrical, or yust the subs? rm33's run full range, or w/marchand? still have a decent soundstage? try the diamond layout yet?
sorry to hear about the kidney stone - i have fortunately never had the pleasure, but a buddy of mine has been thru that, and he said the pain is excruciating. :o hope it passes soon! :wink:
doug s.
I left the mains in place, but I put one sub inboard and behind, and the other is outboard and even with the front of the right speaker. I'm using the 60Hz crossover at 24 dB/octave. I've got the highs dropped down about 10 dB and the low outputs dropped 4 dB, but that will change when I start using my Odyssey Stratos monos again. I've been playing with a newly refurbished Dynaco ST-150, so the gain will probably be different.
Soundstage seems strangely moved forward. I'm not moving the mains until the crisis passes and my body improves;those things weigh close to 90 lb with the feet on.
No one has commented on the decay curves; are they good, bad or ugly?
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not surprising that yust adding the subs, and having them in different locations, would offer improvements. did you try w/o the marchand, letting the rm33's run full range? even tho they have a bass bump, it would be curious to know what effect there would be, w/four different bass sources loading the room.
i am not sure exactly what those decay curves are indicating, so it is hard for me to comment... :scratch:
doug s.