Bass traps and diffusers

[Electrobumps]

What are your room dimensions?

It's not a rectangle room the back dimensions are different depths at the rear, Its L13' x W16' x H8.11'. Pretty sure it is floor to ceiling that is the main issue. I have 18" deep 6 x 4' ceiling cloud.

If I put 2 x more of the 18" 2 x 4' one left and one to the right of me on the floor it reduced that null by about 3db. I think I might make two more ceiling traps 4x4' and try some diffusion panels on them. Not sure how to approach the diffusion when on top of a broadband trap.

 

[RoadrunnerOZ]

You’ve probably got floor to ceiling cancellations in the side and front/rear wall top to bottom edge-corners - maybe some corner trapping in your upper side wall to ceiling junctions. I don’t think diffusers are going to help much as they’d need to be pretty deep for the LF dip you have and it’s better to get rid of the cancellation at the mix position by absorption - ceiling corner edge absorbers will solve floor to ceiling and diagonal standing waves across the room

 

[Tubetec]

Glad this topic came up again ,
Ive been thinking of repurposing typical office partitions as wall mounted acoustic absorbers ,
the fabric of the building is largely see through as far as LF is concerned ,
what Im more concerned about is MF,HF reflections off typical sheet rock or plaster board
I havent dissected your typical office partition , but Im fairly sure its a dense sheet of rockwool with a membrane ,and outer textile mounted in a frame , the room walls are parallel ,as is the building convention , mounting the panels at angles , other than parralel helps defusion of standing waves ,movable screens being a better option save the space penalty

 

[RoadrunnerOZ]

A lot of partitions are compressed glass boards with a dress plastic or cloth coating, also like for ceiling panels. I inherited a pile of these partitions from an office building that was being torn down and they were all clip together solidly made double and single U section frames with double sided, fabric covered, high density fibreglass with a central back-board of 16mm MDF and heavy duty glass in frames at the tops of each panel - great for mobile panels as all I had to do was add low slung casters on the partition feet (these came with them 2 per panel, to create free standing offices).

 

[Electrobumps]

I don’t think diffusers are going to help much as they’d need to be pretty deep for the LF dip you have and it’s better to get rid of the cancellation at the mix position by absorption - ceiling corner edge absorbers will solve floor to ceiling and diagonal standing waves across the room

The diffusers will be placed on top of the broadband traps to bring more high end reflection back into the room. Although there is an interesting thread on Gearspace relating to space couplers increasing LF absorption. Others suggest slatted wood, I don't have any knowledge on what size slats of wood will affect absorption and reflection.

I used this calculator to help find my pressure build ups.

 

[RoadrunnerOZ]

The diffusers will be placed on top of the broadband traps to bring more high end reflection back into the room. Although there is an interesting thread on Gearspace relating to space couplers increasing LF absorption. Others suggest slatted wood, I don't have any knowledge on what size slats of wood will affect absorption and reflection.

I used this calculator to help find my pressure build ups.

The Amroc room modes calculator is very handy. The use of slatted absorbers requires a lot of depth to get effective absorption at LF. Perhaps have a look at a Helmholtz:
http://www.mh-audio.nl/Acoustics/HelmholzPanelResonator.html
Far less room space taken for a greater depth of absorption plus the panel reflects HF and as such a diffuser if not blocking the holes in the absorber could be placed in front.

 

[Electrobumps]

To clarify, I'm not looking to absorb any LF with slated absorbers. Perhaps a better way to say it is that I'm looking for a way for my broadband traps to reflect or diffuse higher frequencies back into the room.

I'm only in this room for 4 more months. So want to stick to broadband as my next room will only be used for a few months and I can treat it pretty quickly with what I have already build.

When I move back to the UK and build my room, I'll definitely look into Helmholtz, they get mixed reviews. I'm always interested in them.

I had some success in the past with limp mass absorbers. However it was in a small room and I needed a lot of them.

 

[RoadrunnerOZ]

To clarify, I'm not looking absorb any LF with slated absorbers. Perhaps a better way to say it is that I'm looking for a way for my broadband traps to reflect or diffuse higher frequencies back into the room.

I'm only in this room for 4 more months. So want to stick to broadband as my next room will only be used for a few months

When I move back to the UK and build my room, I'll definitely look into Helmholtz, they get mixed reviews.

I see. The problem with broadband traps is they absorb the wide spectrum and won’t diffuse - I’d not worry so much about the diffusers but get the absorption placement sorted for problem LF cancellation and look at perhaps a back wall diffuser for the HF/MF afterwards.

 

[Electrobumps]

I see. The problem with broadband traps is they absorb the wide spectrum and won’t diffuse - I’d not worry so much about the diffusers but get the absorption placement sorted for problem LF cancellation and look at perhaps a back wall diffuser for the HF/MF afterwards.

i think you miss my point, I fully understand what a broadband trap does. I understand the issue in my room And how I can fix it. The issue I have to much HF absorption already.

There are plenty of broadband traps on the market with front diffusion plates attached.

 

[RoadrunnerOZ]

i think you miss my point again. I fully understand what a broadband trap does.

There are plenty of broadband traps on the market with front diffusion plates attached. View attachment 122526

OK got your point - I realise that you can do both in one but do you need the diffuser at the same location as the LF absorption. The problem I was pointing out is that a broadband trap is just that - broadband and not targeted to a specific range. If you absorb mids and highs along with the LF and add diffusion you will still have absorption where you are maybe just looking for diffusion. Corner trapping for LF problems and side and rear wall diffusion (over the top of, or not, of say rear wall bass traps) to prevent comb filtering of mids and highs would seem to be a more effective treatment of a smaller space so as not to deaden it too much.

 

[pvision]

I was intrigued by the tube trap idea so did a quick search. In the UK you can buy a 6 metre length of 200 mm culvert pipe for £40 - that would make a couple of decent tube traps

The only drawback is transporting it, so best to find a supplier that will deliver

https://www.ebay.co.uk/itm/256231189332

 

[RoadrunnerOZ]

I was intrigued by the tube trap idea so did a quick search. In the UK you can buy a 6 metre length of 200 mm culvert pipe for £40 - that would make a couple of decent tube traps

The only drawback is transporting it, so best to find a supplier that will deliver

https://www.ebay.co.uk/itm/256231189332

That’s the type of pipe we have here - not too expensive and easy to use as there are end-caps, reducers and joiners available and it’s easy to paint. You can make the open end using an end cap with the centre cut out with cloth cover fastened inside - the outside surface is primed and painted with automotive primer and spray top-coat colour and then a clear-coat finish for a really durable finish in any colour.
The liner inside can be 25mm compressed fibreglass with the cloth face facing inwards and the back par-cut in longitudinal slits to allow rolling up to fit inside the tube. For legs on standing traps I use 3 right angled ornamental shelf brackets screwed onto the outside so each outward facing arm becomes a foot - this stabilises the unit by having a wider base footprint plus keeping the open (or closed depending on which way works best) end off the floor and painted in the same colour as the tube look fine. Self adhesive furniture pads on the undersides of the feet prevent the brackets from scratching timber flooring. This tubing is heavy and needs to have a stable base when vertical.
I normally use 250mm (or even 300mm) OD stormwater pipe - 200mm may be a little tricky to line (although rolled up lower density Rockwool could be used to fill a smaller section tube)..