[Atexanathome]

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.

[poseidonsvoice]

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.

[bpape]

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

[Big Red Machine]

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.

[Big Red Machine]

Okay, great minds think alike and in the same space-time continuum!

[Atexanathome]

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.













Without the above information, it becomes very difficult to advise.

Best,
Anand.

[Atexanathome]

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.









 




Thanks

[SoCalWJS]

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. 

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.

[drummermitchell]

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.

[Atexanathome]

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. 

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.

[bpape]

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

[bummrush]

Just a guess but arent the speakers way to big for the room maybe.

[pelliott321]

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 

[Jim Smith]

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.

[doug s.]

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:


showing diamond layout:


doug s.

[bpape]

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

[doug s.]

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.

[bpape]

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

[doug s.]

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.

[Atexanathome]

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.