Do I need a sound diffuser? How much sound treatment is too much?

Alexxxx

Suspended
Hi all,

I am wondering if sound diffuser will improve my room acoustics? I have done a bit of sound treatment to the room already, and not sure if I've done too much or not enough.

Basic description of the room:
  • 4.2x2.9m room with 2.7m ceiling height
  • seating is 1/3 of the room length from the back wall
  • 12mm underlay with super thick and heavy shag-like carpet
  • Minimal furniture: 3 seater sofa, av-rack (against the back wall). 2 side tables (either side of the sofa), 1 lamp
  • Door is in right back corner of the room

Here is a quick summary of the acoustic treatment I've done so far:
  • 1st speaker reflection points treated with either 2" acoustic panels or 1.5" acoustic foam
  • Back wall at ear level (0.9m tall) is covered with 1.5" acoustic foam
  • 4" acoustic foam bass traps floor to ceiling on the corners of the back wall (left and right)

As part of light treatment I have also insulated 2" thick velvet frames with with rockwool. These frames are located on the left & right wall at the front and on the ceiling 1/2-1" gap. They are there to absorb the reflected light and are 1.2m wide.

Here is what i'm thinking of doing:
  • Sound diffuser at the back wall
  • Sound diffuser abouve the seating area
  • Bass trap on the floor on the front wall
  • Bass trap on the floor and ceiling at the back wall

Will be glad to hear any thoughts / suggestions.

Thanks,
Alex
 

Kingchin

Active Member
Hi all,

I am wondering if sound diffuser will improve my room acoustics? I have done a bit of sound treatment to the room already, and not sure if I've done too much or not enough.

Basic description of the room:
  • 4.2x2.9m room with 2.7m ceiling height
  • seating is 1/3 of the room length from the back wall
  • 12mm underlay with super thick and heavy shag-like carpet
  • Minimal furniture: 3 seater sofa, av-rack (against the back wall). 2 side tables (either side of the sofa), 1 lamp
  • Door is in right back corner of the room

Here is a quick summary of the acoustic treatment I've done so far:
  • 1st speaker reflection points treated with either 2" acoustic panels or 1.5" acoustic foam
  • Back wall at ear level (0.9m tall) is covered with 1.5" acoustic foam
  • 4" acoustic foam bass traps floor to ceiling on the corners of the back wall (left and right)

As part of light treatment I have also insulated 2" thick velvet frames with with rockwool. These frames are located on the left & right wall at the front and on the ceiling 1/2-1" gap. They are there to absorb the reflected light and are 1.2m wide.

Here is what i'm thinking of doing:
  • Sound diffuser at the back wall
  • Sound diffuser abouve the seating area
  • Bass trap on the floor on the front wall
  • Bass trap on the floor and ceiling at the back wall

Will be glad to hear any thoughts / suggestions.

Thanks,
Alex
Sounds like you have a decent room with carpet, minimal furnishings and some acoustic treatment already in place. Your plan seems good for some diffusers on the back wall as long as you have enough of a gap between the seating position sofa and the back wall.

I would also experiment with some diffusers on the side walls in between the the absorbers you already have in place. Diffusion done right in small rooms can open up the sound make the room feel bigger. Some pictures of the room currently would give people a better idea of how much room treatment is currently covering the room. Too much acoustic treatment can be bad, 30% (sometimes less) is usually enough to keep a good balance.

I've only just recently started my journey of room treatments researched and planned for my specific room. Absorption panels at the reflection points it is recommended to use ones with at least 4 inches depth. Others on the forum will have more knowledge and experience of the various room treatments available, able to offer you more advice.
 
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Alexxxx

Suspended
Sounds like you have a decent room with carpet, minimal furnishings and some acoustic treatment already in place.
Thanks, much appreciated.

I’ll attach some photos later on for reference.
 

Alexxxx

Suspended
I’ve uploaded some pics below to show what I’ve done so far.
 

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Kingchin

Active Member
I’ve uploaded some pics below to show what I’ve done so far.
Nice wee setup. Looking at your pictures the first thing i would personally do is replace the thin acoustic foam tiles between the back wall rear speakers. With a couple of thicker (ideally 4inch depth) mineral wool acoustic absorption panels. It will dampen the rear wall reflections from the front left & right, centre speakers much better.

The ceiling looks good well done with a cloud absorption panel already in place. Diffusion could be possibly done on the back wall higher up. But the side walls the left wall probably wouldn't be any benefit because the sofa is so close to the left side wall. You need a bit of space between the sitting position and diffusers for them to be beneficial.

I do think the side walls would benefit from a couple more acoustic absorption panels (again ideally 4inch depth) on each side wall to dampen more side reflections. But those movie pictures nice looking by the way are in awkward positions to place more acoustic absorption panels. GIK acoustics and some other acoustic companies offer free advice on placement of room treatments and where they should ideally go.

Absorption panels unlike diffusers can be easily done DIY cheaply if your handy. Lot's of YouTube tutorial videos showing how to make them yourself. A good place to start learning about room acoustics is from the recent Audioholics home cinema room treatment video series. With Anthony Grimani one of the best room acousticians in the world. You don't have to follow their exact layout as everyone's room is different. But if you get the basics right the rest should follow.
 
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Kingchin

Active Member
I will say diffusion panels aren't cheap to buy, to get very good quality it all adds up, I spent £264 on just two GIK acoustics PolyFusor panels. Plus another £1200 on 5 diffusers, 4 hybrid absorbers/diffusers from other acoustic room treatment companies.

Still waiting on most of them coming as some were a custom order with some custom colour changes finishes to go with my room decor.

Here's one of my GIK acoustics PolyFusor panels on my side wall. It's a polycylindrical sound diffuser and absorber merged into a single unit.
IMG_20210408_165413.jpg

IMG_20210408_165347.jpg
 
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Scion

Standard Member
The risk of too much sound treatment is normally associated with absorption rather than diffusion. Too much absorption of mid range and high end is possible if you cover too much surface area but that doesn't seem to be the case in your room. However it is very difficult to absorb too much low end bass, so again very unlikely in your room. So the question for you becomes why are you focused on diffusion? You never mentioned a particular issue you're trying to resolve; so my thinking would be to first analyze your room's acoustics before you spend any money. REW is a free software package to help pin down any issues. For example, look at your frequency response to see if your problem is on the low end, it usually is in small/mid size rooms. Or look at the waterfall graph to see if some frequencies have a very long decay (again usually a low end room mode). You can also look at ETC graph to determine if reflections are an issue and where they come from.

Specifically, diffusion won't make a noticeable difference to any low end issues. Nor will any foam placed in the corners, even though that is where bass treatments work best. If you find problems on the low end with REW (or similar package) you could try moving the sub's position to smooth out any room modes. You could also buy or build dedicated bass traps for the corners. I built six and they made a huge difference in my room.

So short answer, identify any problems in your room before you start spending money on sound treatment 'solutions'
 

Alexxxx

Suspended
Thanks everyone, I will look into this.
 

Paul7777x

Distinguished Member
I’d seriously consider measuring your room with REW. I’d bet a fair sum that you have a frequency response somewhat all over the place.

And I’d also suggest you remove all of the room treatment and simply run Dirac again without it.

It is exceptionally difficult to get room treatment done well without the necessary maths and measuring.

Dirac will get you 90% of the way there and a little time tweaking the response will get you the rest.
 

Kingchin

Active Member
Buying a microphone and downloading free REW Room EQ Wizard on a laptop would be good. To get a rough idea of how the frequency response is in your own room and identifying any problems. For low frequencies standing waves peaks and nulls you won't be able to get rid of them unless you have a massive commercial cinema size room. But with multiple subs positioned correctly you will be able to locate a main seating position that is outside of some or most of the peaks and nulls.

Room correction EQ it will have a more audible improvement for the low frequencies roughly 250Hz-300Hz and under. Most subwoofers these days have room correction EQ built in to help smooth out the bass. Once you get smoother bass our perception of the other sounds sound better. The mids and treble sound clearer and the overall sound becomes more natural. For frequencies above the 300Hz electronic room correction Dirac Live, Trinnov, RoomPerfect etc. Won't make anywhere near as big a difference as acoustic room treatments.

As for the previous comment that it's exceptionally difficult get room treatment done well without the necessary maths and measuring. That's incorrect, it's relatively simple and in fact much easier than using room correction (bar the simple to use and mostly unaltering RoomPerfect) which can do more harm than good unless you know what your doing. ie you would need the spinorama data of your specific speakers to get the most out of room correction above 250Hz. And how many people actually have that spinorama data information, probably close to zero. Or have the high technical knowledge to know what to do with it. Doing it manually you need a professionally calibrated microphone which can cost anywhere from £3000 to £40,000.
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Forgetting corner bass traps for the subwoofers, room treatment in the first and secondary reflection points won't fix the low frequency response and room bass issues. But it's very easy to implement even for a novice and will definitely make a audible improvement in the sound quality. By damping a little of the lows, some mids and diffusing scattering some mids and highs. Reducing the sound bouncing from wall to wall. It translates into you hearing more of the sound from the speakers than the sound from the room. A good company will show specs of the absorbtion and scattering frequency range, it doesn't take rocket science to then pick acoustic panels that will work well based on those.
 
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Kingchin

Active Member
I’d seriously consider measuring your room with REW. I’d bet a fair sum that you have a frequency response somewhat all over the place.

And I’d also suggest you remove all of the room treatment and simply run Dirac again without it.

It is exceptionally difficult to get room treatment done well without the necessary maths and measuring.

Dirac will get you 90% of the way there and a little time tweaking the response will get you the rest.
Dude you have been trolling spewing crap misinformation on various threads about room correction, Dirac Live making room treatment redundant 🤦🏾‍♂️
PicsArt_04-28-03.49.05.jpg

You personally don't like acoustic room treatments but the fact is that commercial cinemas all use a combination of acoustic treatment and a little room correction. They use room treatment because it makes a audible difference improvement to the sound we hear from our ears.

Even Terry from Pursuit Perfect System YouTube channel who's a die hard Dirac Live user for many years implements a combination of room treatments and room correction. He uses acoustic room treatments in both his home cinema room and stereo room at his house. Because room treatments work, improve the sound quality.

Avforums also mention at the start of any room correction articles that the room itself will have the greatest effect on the sound from your speakers.
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Kingchin

Active Member
Thanks, much appreciated.

I’ll attach some photos later on for reference.
Sorry I apologise at least for myself for us two derailing you're thread. Anyway don't get rid of your acoustic treatment (apart from maybe the tiny corner foam traps which won't do anything for the subwoofer bass)

Acoustic room treatment is used by all commercial cinemas because it actually improves the sound quality of the room. It enhances the mids and highs plus brings the reverb time down greatly.

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Though room correction does have merit if you have WAF or problems with the speakers and subwoofers. Around 300Hz-250Hz and below room correction can improve those bass frequencies from your speakers.
 
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