What would you treat?

[nicol_verheem]

Hi All.

First time in a long time here. Please pardon the long post.

I recently decided to treat my family room, within reasonable esthetic limits. I would love some suggestions from you all, as this is my first time treating.

I attached .mdat file that included 3 sets of measurements, (1) without any treatment, (2) with bass trap (BT) in right rear corner, and (3) with the BT and Dirac Active Room Treatment enabled, ART did a reasonably good job of smoothing the nulls from room modes in SPL plot, but (obviously) couldn't do much for decay times.

I attach two pics showing the room, taken from the kitchen, which has a 12'x12' opening where the left wall would have been. There is a hallway entrance diagonally in the left rear corner. The room is fairly large, 22x18x10'. The listening position middle of back coach. BTW all dimensions accurate in the Room Sim. I treated the opening to kitchen as room as high absorbance. The room sim off by quite bit tho, I could not figure that out. Wall is drywall with very flat, hard, painted surfaces.

Not shown in the pics is with 2'x8' round bass trap tower that I had in the right rear corner, but as can be seen in the included measurements, the BT did not do a whole lot, except for in the RT decay you can see a little quicker decay in the low frequencies.

Note I can't do anything about speaker placement due to room design (the step in front of TV and the door position). Going from one sub to two had less of an impact than I hoped, probably because they are too close to each other, so basically act as one?

I'm sure if can't convince her of curtains, there are already electric blinds within each window. Unfortunately I didn't measure with them down...

I'm thinking I can get away to treat the rear wall and ceiling, and that should be a good start, possibly even enough. The goal is to make vocals (mostly jazzy music but also TV) clearer. There's bass to spare, and the Dirac ART can stay close to my preferred Harman house curve. So frequency response decent, room decay, not so much.

Spectrogram clearly shows bass lingers, and I need traps. Big ones.

But I also suspect an RT60 decay of up to 700ms between 1-2kHz is problematic. Any thoughts welcome.

I'm thinking lots of absorption. And about as much dispersion. I already have quite a few of the 2'x4' absorbers and 2x4' slatted wood diffuser panels courtesy of GIK's Black Friday sale. But I'm still undecided where to put them and how much of it.

I think absorbers for 1st reflection and just in front and above listening position on ceiling, so basically 4 panels symmetrically around the ceiling light. And then mostly dispersion on rear wall, since I'm 6' away from back, and the wooden slats esthetically pleasing. Any thoughts?

I'm still waiting on the matching wood bass trap for right rear corner. The measurements makes me think they won't be adequate, so I might do one in right front corner too, or try to air gap.

Appreciate any input from the community, and Happy new year!

Thanks in advance!

Cheers
Nicol

 

[ddude003]

Welcome @nicol_verheem, I would think about treating corners, where three surfaces come together floor and/or ceiling... Next is two sides including wall and ceiling wall and floor... I might look at Digital Room Correction to push that hot spot down... Maybe there is a way to adjust ART down there... I'm not an ART user so I don't know what to say there... You might also look into hiding some Mass Loaded Vinyl behind some art or any absorbers you already have...

BTY, beautiful room...

 

[Keith_W]

Happy new year.

This is your RT60 with upper and lower tolerance curves calculated for your room volume (112m^3) and target of 500ms. This tells you what frequencies are within target and what you need to do. You are fortunate in that you probably don't need more bass trapping. It's the freqs above 470Hz that you need to work on, and this is relatively easy. This is "ARC L+R".

The Energy-Time Curve (ETC) shows the decay of sound after the main impulse. I chose "ARC L+R" (I presume you mean ART). Ideally, you want all specular reflections (thinner arrows) to be more than -15dB to your main impulse within the first 20ms (I drew the target in blue). Your "No ARC, No BT, L+R" looks even worse. You can work out where the reflections are coming from by calculating the distance with the speed of sound, d = c * t/1000 (c = speed of sound 1125 ft/s, t = time in milliseconds). Pick any reflection, and it had to travel an extra distance d to reach the microphone.

From your photo, the obvious culprits are your coffee table and the rear wall (behind the listening position). If you really wanted to reduce the reflections, you need to get rid of the coffee table and put something at the rear wall. But you have a gorgeous room there, it would be a real pity to ruin the aesthetics by installing foam.

 

[nicol_verheem]

Happy new year.

View attachment 88921

This is your RT60 with upper and lower tolerance curves calculated for your room volume (112m^3) and target of 500ms. This tells you what frequencies are within target and what you need to do. You are fortunate in that you probably don't need more bass trapping. It's the freqs above 470Hz that you need to work on, and this is relatively easy. This is "ARC L+R".

View attachment 88923

The Energy-Time Curve (ETC) shows the decay of sound after the main impulse. I chose "ARC L+R" (I presume you mean ART). Ideally, you want all specular reflections (thinner arrows) to be more than -15dB to your main impulse within the first 20ms (I drew the target in blue). Your "No ARC, No BT, L+R" looks even worse. You can work out where the reflections are coming from by calculating the distance with the speed of sound, d = c * t/1000 (c = speed of sound 1125 ft/s, t = time in milliseconds). Pick any reflection, and it had to travel an extra distance d to reach the microphone.

From your photo, the obvious culprits are your coffee table and the rear wall (behind the listening position). If you really wanted to reduce the reflections, you need to get rid of the coffee table and put something at the rear wall. But you have a gorgeous room there, it would be a real pity to ruin the aesthetics by installing foam.

Keith, thanks so much for taking the time to do this analysis and to write up your findings! I am now much better informed about what to do. I am curious though about your comments regarding: the coffee table. I was assuming since the reflection from the table has such a small additional delay, it won't be as bothersome as the reflections from the ceiling, which travels a lot further, no? Would you leave ceiling alone then? Also, do you have thoughts about dispersion vs absorption on back wall? Thanks again and in advance.

 

[Keith_W]

Hi Nicol, I suggest you purchase and read Floyd Toole's book to gain an understanding of what those measurements mean, and whether you should absorb or diffuse. Essentially, early reflections are perceptually fused with the main signal and have the effect of smearing the sound if they are early and loud enough - the Haas fusion window. I generally use "no reflection within the first 20ms should be greater than -15dB" as my threshold, but some people think it should be -20dB. Whatever it is, it is evident that your room is too reflective.

I should add that many of those reflections will be coming from your microphone position as well, for e.g. if you used a mini tripod and perched your mic on your sofa, you will see a heck of a lot of early reflections like this. You would be measuring a highly local phenomenon and not your actual room.

Dr. Toole's book says that the optimal RT60 can be obtained with room furnishings alone, albeit at the higher end of tolerance. To push the RT60 into the lower end of tolerance, you will need absorbers and not diffusers. Note that there is some disagreement whether you want to absorb, or how much you should absorb. Some people like Dr. Toole believe that some reflections are necessary to provide ambience. Some others believe that reflections are detrimental to the sound, e.g. Ethan Winer's book. I'm not going to open that can of worms here. All I will say is that from your measurements, it appears as if you have too many reflections. What you choose to do with that information is up to you ... sorry.

 

[nicol_verheem]

Hi Nicol, I suggest you purchase and read Floyd Toole's book to gain an understanding of what those measurements mean, and whether you should absorb or diffuse. Essentially, early reflections are perceptually fused with the main signal and have the effect of smearing the sound if they are early and loud enough - the Haas fusion window. I generally use "no reflection within the first 20ms should be greater than -15dB" as my threshold, but some people think it should be -20dB. Whatever it is, it is evident that your room is too reflective.

I should add that many of those reflections will be coming from your microphone position as well, for e.g. if you used a mini tripod and perched your mic on your sofa, you will see a heck of a lot of early reflections like this. You would be measuring a highly local phenomenon and not your actual room.

Dr. Toole's book says that the optimal RT60 can be obtained with room furnishings alone, albeit at the higher end of tolerance. To push the RT60 into the lower end of tolerance, you will need absorbers and not diffusers. Note that there is some disagreement whether you want to absorb, or how much you should absorb. Some people like Dr. Toole believe that some reflections are necessary to provide ambience. Some others believe that reflections are detrimental to the sound, e.g. Ethan Winer's book. I'm not going to open that can of worms here. All I will say is that from your measurements, it appears as if you have too many reflections. What you choose to do with that information is up to you ... sorry.

Again, really appreciate your effort to write this up, your insightful comments and the references. I'll take a look. Since I have a number of panels, I'll try to mount in such away as to play around and measure differences. I suspect this project might keep me busy a while. My gut feeling was I don't want a dead room, so I got 50/50 diffuse/absorb. FWIW the mic was on a proper mic stand, ear hight. Cheers!

 

[Keith_W]

It's your room, you can do what you want. But if it was me, and if I wanted to preserve my room's aesthetics, I would pull the sofa closer to the speakers. That will have the effect of delaying rear wall reflections. On the rear wall, I would put some bookshelves. You could modify some IKEA bookshelves with some absorbent foam and put indoor pot plants on the shelves to hide the foam.

It looks as if the problem frequencies are 500Hz and up. Foam needs to be 1/8 as thick as the longest wavelength you want to absorb (as a rule of thumb). A 500Hz wavelength is 686mm, so the foam needs to be 86mm (3.4") thick. That is quite achievable in most rooms.

If you want to see the effect of the coffee table, take measurements with and without it and compare the ETC. Use REW's "overlays" for a direct comparison.

 

[ddude003]

+1 for the potted plants... Stands of bamboo in big pots filled with earth... Pot of earth for the lows and the bamboo for diffusion...

 

[nicol_verheem]

+1 for the potted plants... Stands of bamboo in big pots filled with earth... Pot of earth for the lows and the bamboo for diffusion...

Thanks, @ddude003 Sounds like a good plan, I will consult with the plant caregiver