Problems with new treated Control Room...Please Help! (freq graph inside)

[jkung]

I just moved into my new studio. I also treated it with many bass traps- 21 to be exact. I have super chunks in the front two corners.

Dimensions of the room are plotted on the layout jpg. i am really having a problem in the low freqs of the room. As i said i have almost every corner covered including ceiling wall corners. when you speak in the room there is virtually no echo.

thanks for all the help.

[jhbrandt]

Kong,

Your room has double modal incidences. It is your dimensions that are messing with the LF. Standing wave issues. It's obvious that your trapping is helping, but not enough. I guessed at the ceiling height - what is it?

Can you post some pictures?

Cheers,
John

[Glenn Kuras]

Also how did you make the bass traps?

[bpape]

Please describe where the monitors and your seating are located.

Treating all the corners is great for decay time but many of the frequency response issues you're seeing may be from areas other than corners (SBIR issues behind monitors, height related modal issues, cancellations off the rear wall, etc.)

Bryan

[jkung]

first off, thank you for all the responses.

@John- The height of the room is 9.5 ft.

@Glenn- The bass traps are made of fiberglass insulation material i found here in china. You may not remember but you actually helped me build them! You answered many a question about my traps and i thank you for that

@Bryan- the monitors are the yellow boxes in my layout diagram above. currently i have been moving them around to alleviate the problem but to no avail. They are at the corners of my mixing desk so i have only moved them back and forth. when tested, the speakers were about 12 inches away from the wall.. my sitting position is 4.5 feet from that same back wall i will put up photos very soon of the situation


As I understand it, modal issues with a room cannot be fixed unless i install a new wall to alleviate it correct? If i change the orientation of my setup so i was facing a corner would that do anything?

[bpape]

Corner orientation in that room is going to do very little to help. You're pretty close to the front wall with your head for that given length.

Modal problems can be at least partially addressed by:

- Sitting where modal problems are the fewest, or at a minimum, where they can be addressed easily given the room layout.

- Damping surfaces which are causing the constructive and destructive combining of waves.

Bryan

[jkung]

@Bryan- Is there any way for me to test where the modal problems are the fewest? Should i try the 38% rule? Same question to which surfaces are causing the constructive and destructive combining of waves?


Here are some photos of the room... the opposite wall is covered with even more traps..

[bpape]

38% is a theoretical optimum assuming a perfectly rectangular, empty, perfectly rigid room. In the real world, you would usually end up between 33 and 38%. The nook in the rear will add it's own little flavor to the response.

The easiest way IMO is to place the speakers in the corners to maximially excite the room modes then experiment with placement front to back at ear level to find the smoothest response. Then start working on the monitor position assuming that listening position.

You're not set in stone at that place but it will be close unless you can't resolve boundary issues there pre-treatment.

Bryan

[jkung]

don't really know how to read this but it might help...

[jkung]

@Bryan- to clarify, you mean have two people move the monitors from the absolute corners while i sit in the mix position and move away from the backwall? after finding the optimal wall position (y-axis) have them move inwards away from the side walls (x-axis)?


if i were to add a wall of diffusers in the back would this help? or is this a structural issue with the only solution being building another wall or just floating the room?

thanks again

i feel like my baby is sick and the doctors don't know what to do....

[SAC]

Originally Posted by jkung

if i were to add a wall of diffusers in the back would this help? or is this a structural issue with the only solution being building another wall or just floating the room?

...

i feel like my baby is sick and the doctors don't know what to do....

One solution refers to structural issues that address only sound transmission/isolation issues while failing to moderate internal room response, while the diametrically opposed alternative is a method which is useless to address sound isolation/transmission issues and only effects the internal room response. Two TOTALLY different issues.

And neither of them will address modal issues!

I might suggest that takes a bit more when going to the doctor than to just walk in say "it hurts" and expect the doctor to psychically assess the causes, let alone the solution.

Bryan has suggested accurate measurements in order to accurately assess the modal behavior, while John has suggested that what bass trapping is present it may be insufficient to moderate the modal behavior.

I would suggest completing the measurements and then assess the amount and location of the bass trapping (and possibly your listening position), as I suspect that you in large measure have been provided the best course of action that will lead to a better result.

[jkung]

Hey Sac

Thanks for the response. To clarify, my main goal is to create a good recording monitoring environment and to moderate internal room response. Isolation is not that big of an issue as i have no neighbors.

Secondly, I can take some more accurate measurements as well. I very new to learning modes and acoustics but i have been reading up about it. Using the mirror technique i have positioned the traps in all the first reflection points. Thank you for being patient with me.

If both of the previous solutions would not address the modal issues, would it be futile for me to add bass trapping or treatment? I might be confused as to modes vs internal room response. For example, if I built out the walls so it was an entire wall of acoustic treatment, would i alleviate most of the problems in the room? If this is the case, I am willing to do that to all the walls and floor if needed.

Basically i am asking what can i do to save my room...

Thank you again for all the replies. I know you guys are just here to help and it is MUCH appreciated

[bpape]

Sorry for the confusion. I was referring to moving your seating position to find the best response with the speakers in the corners and causing the most modal problems. Once you've identified the 'least bad' seating location, then you can begin to work on placing the monitors properly.

This approach allows you to understand what issues are not resolved by seating location and what you can do to the response via monitor location - and what needs to be addressed specifically via treatment.

Bryan

[jhbrandt]

Kong,

It is the distance from the front wall to the bathroom wall and the distance between the side walls create your standing wave double incidences. Beginning at 102.73Hz, 103.08Hz, 118.70Hz, 128.41Hz, 141.51Hz, 171.21Hz... Etc.

My recommendations:

Start with your mix position 100 inches from the front wall. Place your speakers so that the front of the speakers are 38 inches from the wall (62 inches from you). Space them apart by 71.5 inches. This will give you your equilateral triangle mix setup. Panels should be placed on the side walls, centered 42 inches away from the mix position. - ideally this panel should be 48 inches wide for a large RFZ. A panel overhead should be positioned, centered, 42 inches away from the mix position.

You really need to either; 1) get a smaller desk, or 2) angle your desk so that the speakers on the stands behind the desk do not reflect into the mix position. Tilting the desk so that it slopes towards the engineer will help. You can use a mirror laid on the desk to help with this.

You definitely will need more trapping. Get some more panels up in the wall/ceiling corners and the floor/wall corner in front of the mix position will help greatly.

Cheers,
John

[jkung]

I hate to resurrect this old thread but I am just not happy with my room still. I have effectively doubled the trapping and moved my monitors and listening position as suggested so kindly above...

However, I still hear too many obvious peaks and nulls as I walk around the room. These modal issues are driving me insane. If I were to move the back wall or remove it completely would this help? Would this change in dimension alleviate the standing wave double incidences?

Again, THANK YOU SO MUCH EVERYONE

[boggy]

Originally Posted by jkung

.........However, I still hear too many obvious peaks and nulls as I walk around the room. These modal issues are driving me insane. If I were to move the back wall or remove it completely would this help? Would this change in dimension alleviate the standing wave double incidences?
......

It's not really possible to get a homogenous and same low mid and bass response in every place in the room with acoustic treatment based on couple of modular bass traps. This isn't always possible even with custom built acoustic treatment, with wooden frames and much more absorption.

With carefully choosen speaker placement and listening position (or "'least bad' seating location", like bpape said) you can minimize influence of some room modes, but only at listening position... not anywhere else...

Try to get as best as possible response at listening position only... nothing more.

Good luck!

Bogic

[Jens Eklund]

http://www.gearslutz.com/board/6507362-post2.html
Room Measurement After Consulting Gearslutz
Velocity based vs. pressure based absorbers
Porous Absorber Calculator V1.58

[DanDan]

jkunk, are you having audible problems or are you disappointed with your measurements?
The measurements don't look useful. Single speaker drive for full range response is not good, the waterfall ends too soon.
Try single speaker measurements. Export the IR as a WAV and post it here so that we can look into it.
http://www.gearslutz.com/board/studi...er-v2-1-a.html

You room is nicely big. It is unlikely you will have serious problems here.
Are the walls plasterboard or concrete?
You have traps at apparently random places. If you move them all to places where they can do some work, they will.
Have you tried moving your speakers extremely close to the front wall?. At half room height?
Have you tried them in the nulls of the second side mode. i.e. at 1/3 and 2/3 width?
Also take a look a the Desktop Reflection Revealed Thread.

DD

[jkung]

@boggy yeah i can understand that only the listening position will be the sweet spot however it is pretty extreme. thanks for the response

@dandan i am more unhappy with the sound of the place and how the mixes translate. bass is almost non existent in the listening position currently yet at the back of the room, the bass is almost too much. I will do an impulse response asap to show everyone. i have placed the treatment at all first reflection points as well as every corner. I will have to do some more speaker placement experimenting this afternoon. thanks again

@jens thanks reading...