looking for help on flattening frequency response

[frequentseas]

Hi Everyone,

Based on the number of traps I've built and the way I've arranged them I was hoping for a bit better results in my room. I hope some of you can give me some more ideas. Some of my specific concerns along with room details and specs are listed in the paragraph below. Let me know if anymore info would be helpful. Thanks for reading. The people on this forum have been great.

I've just noticed, I will move the one speaker so that it's the same distance off the front wall as the other (see mixing setup pic below). Mixing symmetry is tough because my desk/window is close to the entrance.

The concerns I have are as follows:
-What should be my next move to flatten out my low end response?
-Will beefing up all of the traps to 6” of Roxul SnS with equivalent air-space behind really change that much?
-What can I expect in terms of frequency response performance for a room with my dimensions? +/- 10dB? +/- 7 dB?
-From the information I’ve given you below is there anything you think I have overlooked?

Here is some information along with pictures and diagrams of how I've set up the room.

Room dimensions / Mixing Position:
-I will refer to front of the room as where the monitors are and back where the sewing gear is.
- Room dimensions: see dimensions picture. None of the walls are splayed or angled on purpose.
- There's a gap between ceiling traps for the light fixture it is 2 - 3 feet wide.
- Window is angled down towards the floor at about 7deg.
- My speaker response (mic placed inches from woofer speaker) was very smooth and flat no more than +/- 3dB from 40Hz up.

Bass Trapping:
- With such a small room my original intent was to keep traps fairly thin and very close to drywall behind them.
- All traps made of 3” thick Roxul Safe N Sound covered with burlap in 1 x 4 frames.
- The (facing) front left and (facing) back left, which is covered by a free standing trap, superchunks are hardly that. They’re very shallow due to the closet door and entrance door proximity.
- Ceiling trap frames are pretty much against the ceiling drywall. They sag a lot though (about 2” sag at 6” out from the frame and more towards the center) – I’m assuming this should count as air space for trapping.
- The Front left first reflection (for RFZ) wall trap is currently 6" out from the wall
- The Front right first reflection (for RFZ) wall trap is currently free standing on a lean about 6" out from the wall at the bottom and touching the wall at the top of the frame.

Pictures:
"Room Dimensions"


"Mixing Position Set Up"


"Facing front of the listening room"


"Facing the back of the listening room"


"Entrance to the front of the listening room"

[frequentseas]

Edits:
- The Front right Superchuck is the one that's "hardly that" the front left superchunk is "indeed that".
- The free standing front right wall trap (For first reflection) can only be seen in the entrance picture.
-The picture facing the front of the Listening room should be the one below.

Hopefully i caught everything ...it's after midnight though!


"Facing the front of the Listening Room"

[frequentseas]

...Edit #2 .. of course .. the room frequency response plot...

[Soundman2020]

You have a basic and probably serious symmetry issue at the front of the room. With that angled "entrance" area right next to your speaker, that is going to mess up your stereo image. Is there any way you can turn the room around, so that it faces the other way, since the other end of the room seems to be much more symmetric?

Questions:

1) What problems are you hearing in the room?
2) What is your floor made of?
3) Are your speakers decoupled from the stands?
4) Have you measured the current room response? If so, please post the graphs.

Will beefing up all of the traps to 6” of Roxul SnS with equivalent air-space behind really change that much?

It might, yes. Greater thickness gives you better trapping in the low end. So does a large air gap behind.

- With such a small room my original intent was to keep traps fairly thin and very close to drywall behind them.

Unfortunately, that's the opposite of what you need! The traps should be deep and thick, and a good air gap also helps.

- All traps made of 3” thick Roxul Safe N Sound covered with burlap in 1 x 4 frames.

The insulation is fine, but needs to be thicker. And you need more of them

That's a small room, so you need lots of bass trapping, but you don't have much more space to do it!

- Stuart -

[frequentseas]

Is there any way you can turn the room around, so that it faces the other way, since the other end of the room seems to be much more symmetric?

Yes. Or I can tear down the wall and build another to make it symmetric.... something i overlooked with my greed for room space!

1) What problems are you hearing in the room?

In comparison to listening to a mix in the car, the mix in the room sounds very hollow. I could also describe it as muddy.

2) What is your floor made of?

Laminate. Underneath is a thin foam underlayment. Under that is a 6"concrete slab.

) Are your speakers decoupled from the stands?

In addtion to some thin foam on the speaker plane and thin rubber shoes on the floor, no. I was thinking about this today ... thought I'd enclose some rockwool in wood frame that would fit the speaker or speaker shoe .. which ever turned out more stable when the rockwool compressed under the weight.

4) Have you measured the current room response? If so, please post the graphs.

Yes. I was intent on doing it in post #1 but it took me a couple edits to realize I forgot.

Thanks for the quick response... I'm taking work holidays to make some headway on this and my wife's not liking it!

Cheers,

Sam.

[frequentseas]

Is there any way you can turn the room around, so that it faces the other way, since the other end of the room seems to be much more symmetric?

Yes. Or I can tear down the wall and build another to make it symmetric.... something i overlooked with my greed for room space!

It's been so long I almost forgot what the drywall looks like behind the back right superchunk.

It actually takes a jog as shown in the pic. below. Do you think its still a good idea to flip the room around?


"Room dimensions revised"

[frequentseas]

Since my last post I've added a wall (same construction as other walls) on wheels that fits tight into the angled area to improve symmetry (test not shown ...but I did run some tests that showed it worked well).

I've also beefed up both ceiling traps to a total thickness of 6". All other traps shown are also 6" of Roxul Safe n Sound .

The two RFZ traps I had on opposite sides of the wall running floor to ceiling length wise have been replaced by two traps on each wall running lengthwise along the wall. This was to allow the ceiling trap to be lowered as it doesn't fit past teh RFZ traps becase they stick out from the walls so much.

I added traps that sit infront of the two superchunks at the rear because the superchunks weren't very deep.

All traps shown have an air gap of 4 - 8 inches behind them. The ceiling traps can be adjusted at one end to angle down creating a much larger air gap.

I placed some carpet under the speaker stands to provide a bit of isolation between stand and floor ( I could do better .. it was just something quick).

A comparison of the before and after frequency response 40 - 200 Hz+ is shown below.

Any idea about why the response ramps up so much and drops like crazy at around 70 - 90 Hz? I thought it was because my traps were too thin and didn't have any airspace behind them. That doesn't seem to be the case. Would the sunken window in pic#4 play a part in that.

Instead of two massive ceiling traps which hang well below the wall-ceiling corners like I have done should i put traps in the wall ceilling corners and just have smaller ceiling traps?

Any help would be much appreciated.

Thanks,

Sam.



Frequency reponse comparison (before:purple, after:green)


Front of Control Room.


Back of Control Room.


Sunken window on wall about 8 feet from front wall and opposite wall of door entrance.

[frequentseas]

I thought I'd save you some time by posting some of the room modes(see below). The modes at 62 and 77/78 are on either side of the peak frequency in the plot.

The Harman mode calculator (the one i used for the data below) also indicates i have a tangential mode at 73 Hz .. this is right inline with peak in the plot.

The room mode analysis seems to explain the peak .. but why the quick drop down to 90 Hz??
I'm guessing it's the absorbtion properties of the wool starting to take effect as the absorbtion data almost doubles from 125 to 250 Hz.

Here are the questions I had from the previous post:
-Instead of two massive ceiling traps which hang well below the wall-ceiling corners like I have done should i put traps in the wall ceilling corners and just have smaller ceiling traps?
- Any idea about why the response ramps up so much and drops like crazy at around 70 - 90 Hz?
- Any other comments? Observations?

Cheers,

Sam.


Axial Standing Waves
Enter room dimensions: 1st 2nd 3rd 4th
Height: 7 ft -3 in 78Hz 156Hz 234Hz 312Hz

Width: 9 ft -2 in 62Hz 123Hz 185Hz 247Hz
Length: 14 ft -9 in 38Hz 77Hz 115Hz 153Hz
Speed of sound: 1130.0 Feet per second Default = 1130.0 (344M sec.)
Room volume = 980 Cubic feet

[AVare]

First thought is the mic is in a null at those frequencies.

Andre

[frequentseas]

Andre, good call!

I did about a dozen measurements in and around the listening position moving the measurement mic by a foot or less. Before when I did measurements of various spots I was moving the mic by about 2 feet at a time.

I was able to achieve the improvement shown below. The response at the old mixing position is shown in purple and the improved mixing position is shown in blue.

I'm pretty happy with these results (about +/- 10dB) considering the size of the room and that this is just a hobby for me. From what I think I remember from checking out the results from other comparable small rooms +/- 10dB was a good starting point.

Thanks a tonne,

Sam.



LowFrequency(40-200Hz): Old Mixing Position(purple), Better Position (blue)


FullSpectrum(40-20,000Hz): Old Mixing Position(purple), Better Position (blue)

[AVare]

Congratulations. You are correct in staing that +- 10 dB is very good, especially for such a small room.

Andre