Thoughts on Acoustic Treatment please

[DownUnderGazza]

I'm moving into a new rental home and would appreciate some thoughts on how best to acoustically treat this room.

Attached are photos of the previous tenants setup, but I suspect I'll end up doing much the same.
I'll be using MiniDSP Dirac 2x2 pre-amp to process things.

My initial thoughts would be some 2m high 100mm / 4" deep panels behind the couch.
Perhaps a mix of absorption and diffusion.

Anyway, any thoughts would be appreciated.

 

[alex-z]

Can you use another room? All that glass is doing you zero favours.

At minimum I would install 4" absorbers to cover the glass behind the TV when in use. Plus 4" panels on the ceiling.

Seating has to come forward. I would personally do 6" absorption on the back wall for bass management mixed with proper quadratic diffusion.

 

[ebslo]

I would take care of SBIR and LBIR first. So yes, your 4" absorbers behind the couch would be good for LBIR, but they need to cover the area directly behind where peoples' heads will be, not up high on the wall; this probably requires pulling the sofa out a few inches. For SBIR, I would use 4" to 6" free-standing panels over the first reflection area of the front "wall", so probably from directly behind the speakers extending a couple feet towards the TV. The panels behind the speakers ideally would be as close as possible to the speaker (leaving a little gap to make sure they don't touch), but if those speakers have a rear port you may need to leave a bit more space. Actually, the panels don't need to come all the way down since the drivers are high in the towers, so if you can find freestanding panels where the panel is raised to above the port but below the drivers then it could be placed ideally.

 

[Thomas_A]

I would change place of Sofa and Hifi. And use damping panels behind speakers. Use diffuser blinds/curtains in window.

 

[Frgirard]

Can you use another room? All that glass is doing you zero favours.

At minimum I would install 4" absorbers to cover the glass behind the TV when in use. Plus 4" panels on the ceiling.

Seating has to come forward. I would personally do 6" absorption on the back wall for bass management mixed with proper quadratic diffusion.

The glass is not a specific issue. It is a wall with a value of stiffness and a resonance frequency.
Behind the TV, it's a good place.
The glass on the side wall like a plasterboard wall generate reflections, standing wave.

Depending on the type of window mounting, it can help absorb the bass but can make noise when vibrating.

In my case, my big windows is a good bass trap at 40 Hz.

Put panels of 4" behind the couch is a weird idea. The wall behind the couch is under the mode 1.0.0
4" works only above 500 Hz. Totally useless

 

[Trell]

Put panels of 4" behind the couch is a weird idea. The wall behind the couch is under the mode 1.0.0
4" works only above 500 Hz. Totally useless

Depends on the manufacturer and what the panels are constructed of.

4” panels have useful absorption to perhaps 125 Hz or so mounted to the wall. A large part of the backwall should be covered. Better with thicker panels and/or with an air gap, though. Corners could have straddling panels for better below 100Hz performance.

As an example have a look at tables in the following article from realtraps:

RealTraps - Product Test Data

 

[alex-z]

The glass is not a specific issue. It is a wall with a value of stiffness and a resonance frequency.
Behind the TV, it's a good place.
The glass on the side wall like a plasterboard wall generate reflections, standing wave.

Depending on the type of window mounting, it can help absorb the bass but can make noise when vibrating.

In my case, my big windows is a good bass trap at 40 Hz.

Put panels of 4" behind the couch is a weird idea. The wall behind the couch is under the mode 1.0.0
4" works only above 500 Hz. Totally useless

Have you ever listened to an untreated room with that much glass? It rings at high frequencies and not at low frequencies. Plasterboard reflects sound as well, but it has a much higher damping factor, so it stops releasing energy back into the room much faster.

Also, you can't think solely in terms of room modes, decay times matter a great deal. I recommended 6" behind the couch, which will have a significant impact on the 100-250Hz mid-bass region. 140mm mineral wool with 8000 Pa.s/m2 flow resistivity and a 50mm air gap has .5 absorption coefficient at 100Hz and .85 at 250Hz.

 

[MCH]

Hello all, newbie here. I was thinking as well on doing some very minor treatment in my livingroom so did some brief online research and my initial takeaways from what i read were to take care first of the first reflections (side walls, ceiling) and bass traps, and that the back wall (behind the listener) was by far not so important. I see people here discussing about treating the wall behid the couch. Is this because in the case of the OP is the easiest to do, because the couch is very close to the wall, or are my assumptions wrong and the back wall is as important as the others? Thank you.

 

[Thomas_A]

I would not suggest to add damping on the wall behind the couch. Paintings, other irregular decorations, or if there is a window there, deep blinds. I suggest to use damping at and around the speakers, a thick carpet and a coffe table in front of the sofa. Side-walls also decorated with paintings or irregular objects. Use a fabric based sofa, pillows and soft headrests as in the picture above.

 

[ebslo]

I see people here discussing about treating the wall behid the couch. Is this because in the case of the OP is the easiest to do, because the couch is very close to the wall, or are my assumptions wrong and the back wall is as important as the others? Thank you.

Because the couch is close so the wall. Common advice is to put the listening position farther from back wall, in which case the back wall first reflection isn't nearly as important. But if you have to put couch against the wall then the back wall first reflection will be higher level, earlier, and the first (strongest) cancellation frequency will be in the upper bass or lower midrange instead of in the sub bass.

 

[MCH]

Because the couch is close so the wall. Common advice is to put the listening position farther from back wall, in which case the back wall first reflection isn't nearly as important. But if you have to put couch against the wall then the back wall first reflection will be higher level, earlier, and the first (strongest) cancellation frequency will be in the upper bass or lower midrange instead of in the sub bass.

I see, I might reconsider this option then... thanks!

 

[Thomas_A]

I sit close to the wall but have neck rests on the sofa. There is a cancelation dip around 600-700 Hz which I believe is the wall effect. However, with the neck rests, this dip is flattened out.

 

[DownUnderGazza]

Really appreciating everyone's help and suggestions. Many thanks

 

[Larry B. Larabee]

Does anyone know what approximate range of frequencies would be affected by the 2’x4’ x 4” hunks of rockwool held together by 2 hefty garbage bags propped up in the front corners of my room?

thanks

 

[alex-z]

Does anyone know what approximate range of frequencies would be affected by the 2’x4’ x 4” hunks of rockwool held together by 2 hefty garbage bags propped up in the front corners of my room?

thanks

Porous Absorber Calculator

4" mineral wool is actually 3.5", 89mm.

For flow resistivity, look at the datasheet for your specific type of mineral wool. If the stuff you have is flexible building insulation, 8000-10000 Pa.s/m2 is a good bet.

Punching in those numbers, expect .5 absorption coefficient at 250Hz. Adding an air gap between the absorption and walls improves that significantly, 3.5" air gap yields .5 absorption at 140Hz instead.

The high frequency absorption will depend on the material you cover the mineral wool with.

 

[Hipper]

Have we seen this room before? It looks familiar. If we did perhaps our advice wasn't good enough and the previous tenant had to leave!!!

If you do get panels you could get decorative ones which can have your photographs or art work on them.

 

[Larry B. Larabee]

Porous Absorber Calculator

4" mineral wool is actually 3.5", 89mm.

For flow resistivity, look at the datasheet for your specific type of mineral wool. If the stuff you have is flexible building insulation, 8000-10000 Pa.s/m2 is a good bet.

Punching in those numbers, expect .5 absorption coefficient at 250Hz. Adding an air gap between the absorption and walls improves that significantly, 3.5" air gap yields .5 absorption at 140Hz instead.

The high frequency absorption will depend on the material you cover the mineral wool with.

Thanks Alex, this is interesting.
What estimated level of attenuation per .5 AC?
The air gap moves the freq. of AC (this is handy) what is the Q factor, typically, assuming resistivity numbers you mentioned.
Two birds with one stone for the covering material, or is there interaction between the materials that reduces effectiveness at each of the frequency ranges?
Do you have an easier to use source for making calculations, the one provided is too messy for me.
thanks

 

[DownUnderGazza]

Have we seen this room before? It looks familiar. If we did perhaps our advice wasn't good enough and the previous tenant had to leave!!!

If you do get panels you could get decorative ones which can have your photographs or art work on them.

Haha, not from me anyway!
Signed up for this place barely a week ago, so all new to me.
Good idea on the decorative panels tho. Cheers