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Acoustic treatment advice - critique my room!


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Any thoughts on my proposed design/approach? The big question I have is how to measure the effectiveness of the treatment. My frequency response (post Anthem ARC correction) is pretty good so what will I be looking for to know my money has been invested well? RT60 time in REW or anything else?

 

Any experience with these diffusers (measurements show it’s supposed to work down to 150Hz) ? This is what I’m considering for my rear wall.

https://soundacoustics.com.au/product/acoustic-foam-panels/hybrid-absorber-diffuser-ha600-75/
 

This is what I’m leaning towards for my DIY absorbers - 580mm (W) x 1100mm (H) x 100mm (thick):

https://higginsinsulation.com.au/custom-polyester/polyester-acoustic-insulation-batts/

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I would stay away from those diffusers - not that they won't work but they are just soooo expensive as you will need quite a few of them.

Be easier and cheaper to make a pine frame and bend some MDF into it !!

 

That Higgins stuff looks great though - would like some for my room but they don't ship to WA :(

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2 hours ago, OzJustin said:

Any thoughts on my proposed design/approach? The big question I have is how to measure the effectiveness of the treatment. My frequency response (post Anthem ARC correction) is pretty good so what will I be looking for to know my money has been invested well? RT60 time in REW or anything else?

Yes. I’d run post ARC measurements using a calibrated mic in REW and look at frequency response, your step response, decay plots and waterfalls in the sub 500 Hz ranges. 
 

this will help you see where you have room related reflection issues, whether you need to do more work in ARC and also help plot your next steps in terms of room treatment options

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8 hours ago, niterida said:

I would stay away from those diffusers - not that they won't work but they are just soooo expensive as you will need quite a few of them.

Be easier and cheaper to make a pine frame and bend some MDF into it !!

 

That Higgins stuff looks great though - would like some for my room but they don't ship to WA :(

With those diffusers, I was only planning on two inside each rear corner. Two of them is only $140 (plus $20 postage) and will cover approx 60 x 120cm which I’m guessing will be sufficient. The DIY absorbers (60 x 150cm)  I’m planning should be about $80 each and then I’d have to buy and bend the MDF into it with a groove inside each side of the pine frame. So only a slight price difference and the Sound Acoustics ones have measurements to back up the performance.

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On 21/09/2021 at 4:32 PM, OzJustin said:

With those diffusers, I was only planning on two inside each rear corner. Two of them is only $140 (plus $20 postage) and will cover approx 60 x 120cm which I’m guessing will be sufficient. The DIY absorbers (60 x 150cm)  I’m planning should be about $80 each and then I’d have to buy and bend the MDF into it with a groove inside each side of the pine frame. So only a slight price difference and the Sound Acoustics ones have measurements to back up the performance.

I am no expert and most of what I think I know about Diffusers and absorbers is that Diffusers go on walls and low freq absorbers go across the corners.

So are you trying to use these as absorbers ? I know it says they work and gives specs but I seriously doubt they do much (if anything) in the way of real world absorption and certainly nothing in the lower frequencies.

The DIY absorbers will be far superior IMUEO (In My UnEducated Opinion)

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On 21/09/2021 at 8:36 AM, OzJustin said:

Any experience with these diffusers (measurements show it’s supposed to work down to 150Hz) ? This is what I’m considering for my rear wall.

https://soundacoustics.com.au/product/acoustic-foam-panels/hybrid-absorber-diffuser-ha600-75/

I've not tried them, but worth a go to keep some high frequencies in the room...and based on what they say on their site, the membrane improves the low freq absorption, which makes sense.

 

On 21/09/2021 at 9:45 AM, niterida said:

I would stay away from those diffusers - not that they won't work but they are just soooo expensive as you will need quite a few of them.

 

On 21/09/2021 at 6:32 PM, OzJustin said:

With those diffusers, I was only planning on two inside each rear corner.

you may need more than 2, and to think about where you place diffusion/what you want the diffusion for...

If it is just to keep treble in the room as you add more absorption, then these will do that with some diffusion added (a good thing)

 

On 21/09/2021 at 9:45 AM, niterida said:

Be easier and cheaper to make a pine frame and bend some MDF into it !!

I'd be somewhat cautious of this approach

On 21/09/2021 at 6:32 PM, OzJustin said:

and the Sound Acoustics ones have measurements to back up the performance.

^this - there's been at least some R&D and measurements done.

Bending a piece of MDF would provide some diffusion, but how will that membrane interact with the absorption behind?

How thick does the MDF need to be to work with the absorption behind?

 

In the DIY world, placing a plywood/MDF membrane over absorption would generally require the trap to be sealed to create a "pressure" trap rather than a "velocity trap"...

...and unfortunately the porous absorber calculator site appears to have been hacked and wants to sell you pharmaceuticals :(

 

In this case the manufacturer has done a bunch of work and provided measurements - and they're not ridiculously expensive to try a few...

 

If you did want to DIY some diffusion over absorption I would recommend placing slats over the absorption in a 1D "Binary Amplitude Diffusor" (BAD) pattern.

The amount of diffusion is low, but they're easy to DIY and keep treble in the room - I'm happy to put more info on BAD panels into this thread, or you can PM me if interested.

 

IMHO applying slats over absorption in a BAD pattern is an excellent approach to bringing treble back into the room during the process of adding enough absorption to manage the bass in the room.

 

On 21/09/2021 at 8:36 AM, OzJustin said:

This is what I’m leaning towards for my DIY absorbers - 580mm (W) x 1100mm (H) x 100mm (thick):

https://higginsinsulation.com.au/custom-polyester/polyester-acoustic-insulation-batts/

If you want to manage bass in your room under 200Hz with absorption then 580mm (W) x 1100mm (H) x 100mm (thick) absorption is way too small/thin.

 

Absorption needs to be big and thick to manage bass under 200Hz

Absorption needs to be truly massive to manage bass under 150Hz

 

How much absorption you need will depend on your room, how rigid it is acoustically, whether your room bass issues can be assisted/ameliorated with speaker/sub placement etc.

I'm glad I don't have an acoustically rigid room - my room is lightly constructed and all the low bass leaks out, which helps "in room" acoustics, but the family and neighbours hear all of the leakage :(

 

I run 3 layers of 75mm Acoustisorb3 in my traps - so 225mm deep - they work fine with some EQ below 150Hz.

 

I'm pretty happy with the bass performance in my room - clean tight and dry - my room and system supports turning the bass up when the mood takes me...and my family and neighbours are amazingly tolerant :)

 

My reverb times aren't amazing, but loads of absorption cleans up >150Hz incredibly well - room treatment is the best "bang for buck" improvement I've made to my system.

 

Mike

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@almikel - Thanks very much for the advice Mike.

 

Just to clarify a few things. From what I can see of my post ARC correction, my biggest area to tame is 20 - 300Hz (and predominantly 50-200Hz). The curves for all of my speakers are generally pretty flat from 300 - 5k Hz. I've got a PDF of my calibrated results earlier in the thread.

My above acoustic treatment design, which incorporates absorbers and diffusers selectively throughout the room, is based on the 'Home Theater Gurus' tutorial on youtube where they suggest the best 'bang for your buck' is absorbers at the first reflection points on the side walls and then a combo of absorbers and diffusers in the rear of the room to improve spacial characteristics in the room. For the DIY absorbers, I was looking to use the 100mm thick Higgins polyester, noting that it's unlikely to absorb anything below 200Hz. The Sound Acoustics diffusers that I'm considering for the rear inside corners apparently absorb down to 150Hz so could tame some of my apparent problem area. Then I'm looking at a deep bass trap in my study area with a DIY absorber (probably using 4-5 deep sheets of the Higgins polyester to create an absorber of 400-500mm deep with at least a 1.5m air gap behind. I could also add a 300mm deep trap in the back right corner with a 300mm air gap behind down the track, but I don't want to go too crazy on the acoustic treatment since I'm not confident in what it will achieve. I've read enough to make myself dangerous but not enough to have any real idea what I'm doing! Does my approach sound reasonable?

The Tontine Acoustisorb 3 batts look interesting but upon further googling it looks like Tontine was acquired and is now sold as Polymax. Hard to keep track of the companies and what is reputable! Seeing that you're in Brisbane, dare I ask where you source your materials?

 

I've read a little on the BAD panels but certainly wouldn't turn down more info if you're happy to share it. I've considered adding a diffusion scatter plate onto the front of my DIY absorbers to turn them into hybrid absorber/diffusers but I haven't found anywhere that makes plates (binary sequence pattern) similar to GIK Acoustics.  https://www.gikacoustics.com/product-category/alpha-series/

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