Home Theater Acoustic Treatment Help Needed

[Mocs123]

After several years of being without a theater, I built version 3 of my theater last summer and got the theater functional, but time constraints and budget over-runs prevented me from putting the finishing touches on like acoustical treatments, and I believe it’s time to remedy that situation. I’m looking for advice on how many panels to purchase and where to hang them.

Let’s start by telling you about my room. The room is 16’x21’x8’ with luxury vinyl plank floor over concrete. Walls are double 5/8” heavyweight drywall with rockwool insulation and the ceiling is 5/8” drywall with pink fiberglass insulation above.

The room has the screen mounted 27” away from the front wall and a “false wall” with the L/C/R and four subs behind the screen. The room has a two-row configuration with three seats in each row and the second row on a 12” riser. The surround and rear-surround speakers are in-wall speakers, and the four Atmos speakers are in-ceiling speakers. I have two layers of Linacoustic duct liner floor to ceiling behind the screen wall that wraps around the corners approximately 18”.

I have 21 Auralex Minifusers for diffusion that are currently unmounted (and unpainted!). I can use them in any configuration, but I was thinking of making a three foot tall and seven foot wide panel with them and mounting it above the rear seats on the back wall, but can use them in another configuration if it treats the room better.

My initial thoughts are in addition to the Minifusers on the rear wall to put Acoustimac absorption panels on the walls – I was thinking four – 2’x4’x2” panels on each side wall as well as a couple of 2’x4’ panels on the ceiling. I have attached a sketch of my planned layout, does that look OK or are there things that I could do to differently to increase effectiveness? Should I make any of the panels 4” bass traps rather than 2” panels? If so which ones? My OCD for symmetry says maybe the ceiling mounted panels but that might not be best.

Also, I am thinking of going with Acoustimac’s Eco-Core insulation as they say it outperforms Roxul or OC703 – Does anyone have any experience with it? Also, my room is a dark gray and I am thinking of going with black panels. Is there any advantage between any of their three fabric options (DMD, Executive, and Suede)?


Thank you so much for your help as I work through the last few touches of my Home Theater!

 

[pozz]

Nice job. It looks great.

To be honest, if you're going to spend this much money on a dedicated room it's best to contact an acoustic consultant. Otherwise, measure the FR, RT60 and ETC at each listening position to get a sense of your requirements. This is absolutely necessary before applying any treatment.

You may want to reconsider the seating positions unless there's a specific reason to have the back three so close to the wall. The bass levels for those seats will be at different levels compared to the front. If you have no room to shift them around, that's ok. It's just something to be aware of and deal with later on.

About the diffusors: thing with them is that they need an effective distance to function, which should be defined by the manufacturer. Otherwise you'll get unexpected lobing/reflection effects that affect intelligibility. I would also ask what the absorption coefficient is if Auralex doesn't already disclose it. I would imagine the graph would show a high Q midrange effectiveness since the Minifuser is a thin membrane, though it's possible that they haven't measured it.

You may also find that the back seats will also have higher/lumpy bass levels due to SBIR.

About the Acoustimac products. I don't have experience with them personally. When looking at fabric types for absorbers, acoustic materials are loosely woven so that they don't impede airflow and don't become reflective too early. You might ask the difference between their DMD and Guilford of Maine (which they also offer, and is a well-known acoustic fabric) and the others they have available.

I looked at the RAL acoustical reports for their 4" "bass trap", specifically for "standard fibreglass & mineral wool", and I have to say that the data is really questionable. Rockwool normally behaves like Owens-Corning or the "Eco-Core" product they advertise (could be denim—I would ask), which is to say a rapid drop in efficiency down below 200Hz or so, depending on thickness. The data reported for the 6" trap is also hard to believe, unless both of them use some sort of membrane in addition to a broadband material.

For the ceiling, if you have vertical space, consider space coupler diffusors below absorbers. Hopefully they won't get in the way of your lighting or projector.

Whatever you end up going with, it's better to go with thick broadband absorbers so that they don't disproportionately affect the midrange, but don't expect any real change below 100Hz. Membrane or Helmholtz absorbers are the way to go there.

And before anyone else jumps in with it: room EQ for bass peaks below the transition frequency will help things along nicely.

 

[Bartl007]

I'm not sure what speakers you're using or the on and off axis response measurements, but that could come in to play with your treatment strategy.

You can ask 10 different acousticians what to do and get 11 different answers. Here are a few ideas, hope it helps:

Second half of this one is the part on placement of treatments

I believe this follows the general recommendations from Gerry Lemay's HAA:

 

[Mocs123]

Thank you both for your responses. I probably didn’t spend as much as you would think, as I was on an extremely tight budget and scoured craigslist, ebay, and audio-classifieds for good deals on equipment (plus I had some from a previous HT room several years ago) and did all the work myself including the HVAC which I had never done before.

I’m not opposed to getting an acoustic consultant though I have no idea what one would cost to come to a rural area nor how to even find out (Google is my friend I guess). I do have a UMIK-1 and REW on my laptop so when I get a day off I need to spend some time reading the tutorials in this forum and figuring out how to use it.

I know having seating on the back wall isn’t ideal, but I had to make some design compromises due to the space I had and the budget. Most of the time it will just be the front row used except for when the kids have friends over.

I don’t have to use the Minifusers if they don’t help the room. I just found a good deal on some used so I picked them up – that’s also why I have an odd amount as I think they were sold in cases of 12. If I use them, I will pack them with some left over Linacoustic I had from the front of the room.

I may end up going with GIK Acoustics now that I’ve done more research. Supposedly they use a denser Rockwool then the others, but their factory is also within driving distance so I could probably save a little bit by picking them up.

I'll have to check out the video's when I'm off on Sunday.

My speakers are the JBL Studio530’s that were tested here (I got them for $280 shipped)

https://www.audiosciencereview.com/forum/index.php?threads/jbl-studio-530-speaker-review.12298/

 

[pozz]

Thank you both for your responses. I probably didn’t spend as much as you would think, as I was on an extremely tight budget and scoured craigslist, ebay, and audio-classifieds for good deals on equipment (plus I had some from a previous HT room several years ago) and did all the work myself including the HVAC which I had never done before.

I’m not opposed to getting an acoustic consultant though I have no idea what one would cost to come to a rural area nor how to even find out (Google is my friend I guess). I do have a UMIK-1 and REW on my laptop so when I get a day off I need to spend some time reading the tutorials in this forum and figuring out how to use it.

I know having seating on the back wall isn’t ideal, but I had to make some design compromises due to the space I had and the budget. Most of the time it will just be the front row used except for when the kids have friends over.

I don’t have to use the Minifusers if they don’t help the room. I just found a good deal on some used so I picked them up – that’s also why I have an odd amount as I think they were sold in cases of 12. If I use them, I will pack them with some left over Linacoustic I had from the front of the room.

I may end up going with GIK Acoustics now that I’ve done more research. Supposedly they use a denser Rockwool then the others, but their factory is also within driving distance so I could probably save a little bit by picking them up.

I'll have to check out the video's when I'm off on Sunday.

My speakers are the JBL Studio530’s that were tested here (I got them for $280 shipped)

https://www.audiosciencereview.com/forum/index.php?threads/jbl-studio-530-speaker-review.12298/

Thanks for shipping in those speakers for review.

As for the acoustic consultant, I wouldn't know who to recommend without doing some research. There's a few I know that do interesting home studio designs but that's about it.

I used the 8" GIK traps with and without membranes and they are pretty good. The build quality wasn't the greatest in my experience case you're going for looks. For real bass traps they have a tuned membrane series, although those are pretty expensive: https://www.gikacoustics.com/product-category/tuned-membrane-bass-traps/

 

[vendyseanjoe]

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