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Sound diffusers - worth the money?

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Sound diffusers - worth the money?

Postby paulsmusic » Wed Jan 23, 2019 8:17 pm

I'm currently planning acoustic treatment for my home studio, which I'll be using for tracking, mixing and mastering. I already have around 10 acoustic panels that I built from an SOS design (foam fronted wooden frames with rockwool lining), but I don't want to deaden the room too much, as I'll be recording acoustic instruments.

Any advice on using diffusers would be greatly appreciated. I have a large bookcase that's filled with flight cases / books etc., which I'm guessing will provide some diffusion, and I also have a large wooden board that I'm considering placing on the floor when I want to record acoustic guitar, to liven the recording up. Will diffusers also liven up the recording? Or do they serve a different purpose?

I've been looking at diffuser prices, which seem to vary quite a lot, and found these on Ebay from Ukraine, which are much cheaper. Any thoughts on whether these are any good? Cheers!

https://www.ebay.co.uk/itm/4pcs-50-50-5 ... 3030852051
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Re: Sound diffusers - worth the money?

Postby Sam Spoons » Wed Jan 23, 2019 8:45 pm

They don't look to me like they'll do much diffusing (apart from being set off the wall) and you could achieve the same effect by facing your absorbers with something like this :-

https://www.diy.com/departments/screening-panel-board-th-6mm-w-610mm-l-1830mm/1696222_BQ.prd

I would say diffusers, to be effective, need to have a pseudo random surface, a bit like your bookcases (which will do the job).
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Re: Sound diffusers - worth the money?

Postby paulsmusic » Wed Jan 23, 2019 9:29 pm

Sam Spoons wrote:They don't look to me like they'll do much diffusing (apart from being set off the wall) and you could achieve the same effect by facing your absorbers with something like this :-

https://www.diy.com/departments/screening-panel-board-th-6mm-w-610mm-l-1830mm/1696222_BQ.prd

I would say diffusers, to be effective, need to have a pseudo random surface, a bit like your bookcases (which will do the job).

Thanks Sam! Will probably just start with the bookcase and see how it goes!
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Re: Sound diffusers - worth the money?

Postby Hugh Robjohns » Wed Jan 23, 2019 9:50 pm

Those panels are similar to the Vicoustic Wavewood design:

https://www.vicoustic.com/product/wavewood

The slotted MDF panel is indeed intended to act as a high-frequency 1D diffuser, supplementing the broadband absorption of the underlying material.

It is easy to over-damp the room at mid and high frequencies with. Road and absorber panels, so that Wavewood panel helps to restore some HF brilliance. We've achieved a similar effect in some Studio SOS visits by gluing old CDs to the from of some foam panels!

A more versatile alternative might be to acquire some MDF sheets and place them on the floor or propped on stands around the guitar area to give a bit more zing to the recording, while leaving the room relatively dead for vocals etc.

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Re: Sound diffusers - worth the money?

Postby paulsmusic » Thu Jan 24, 2019 10:20 am

Thanks for the tips Hugh! I do have the top from a large table that I'd thought about putting on the floor to liven up acoustic guitar recordings. I guess it would be better to place it a few feet from the guitarist so that their feet aren't on it, and also place the mic stands on the carpet so they don't pick up vibrations? (apart from good vibrations!)
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Re: Sound diffusers - worth the money?

Postby Hugh Robjohns » Thu Jan 24, 2019 12:29 pm

paulsmusic wrote:Thanks for the tips Hugh! I do have the top from a large table that I'd thought about putting on the floor to liven up acoustic guitar recordings. I guess it would be better to place it a few feet from the guitarist so that their feet aren't on it, and also place the mic stands on the carpet so they don't pick up vibrations? (apart from good vibrations!)

Yes, foot-tapping on a wooden surface -- while sometimes appropriate -- is usually not required!

But placing (wooden) reflective surfaces under and around an acoustic guitar performance can really add something helpful to the sound picked up by the mics.

If you have the DIY skills and space, you could upgrade your table top by mounting it on a frame with wheels, and fixing 2-inch (or better still, 4-inch) thick foam or mineral wool on one side (covered if necessary) to form a mobile broadband absorber.

You then have a useful studio acoustic screen which gives you options for altering the acoustics -- hard and reflective surface for guitars etc, and dead and non-reflective for placing behind a vocalist or as a gobo for screening spill from guitar amps etc.

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Re: Sound diffusers - worth the money?

Postby paulsmusic » Thu Jan 24, 2019 12:37 pm

That's a great idea - thanks Hugh!
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Re: Sound diffusers - worth the money?

Postby Hugh Robjohns » Thu Jan 24, 2019 12:51 pm

There's lots you could do. Here are a couple of naff pics of the kind of things I had in mind. In both examples you can see that the panels have an absorptive side, and a hard reflective side:

gobo1.jpg
gobo1.jpg (10.09 KiB) Viewed 1122 times

gobo2.jpg
gobo2.jpg (9.34 KiB) Viewed 1122 times


You could also add strips or blocks of wood in different thicknesses to the front of the table to provide some diffusion.

The most important thing, though, is to make sure the stand is totally stable. No one wants a 6-foot gobo toppling on them, or crushing their irreplaceable guitar, just because someone brushed against the gobo as they walked past!!

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Re: Sound diffusers - worth the money?

Postby paulsmusic » Thu Jan 24, 2019 2:23 pm

They look amazing! I could probably adapt some of the panels that I built from one of your SOS designs!
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Re: Sound diffusers - worth the money?

Postby Studio Support Gnome » Sun Jan 27, 2019 5:44 pm

Sam Spoons wrote:They don't look to me like they'll do much diffusing (apart from being set off the wall) and you could achieve the same effect by facing your absorbers with something like this :-

https://www.diy.com/departments/screening-panel-board-th-6mm-w-610mm-l-1830mm/1696222_BQ.prd

I would say diffusers, to be effective, need to have a pseudo random surface, a bit like your bookcases (which will do the job).


That'll be because you don't know about diffusion .

you can make flat diffusors no problem

For example Binary Absorption Diffusors

(See RPG's research, deriving their BAD panels, )

they can by Hybridised as well into curved assemblies, but that's not the point.

Actually providing useful , "nice" diffusion is a mathematical threading of the needle from 1000 miles away/.
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Re: Sound diffusers - worth the money?

Postby Sam Spoons » Sun Jan 27, 2019 6:03 pm

Fair enough SSG :D
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Re: Sound diffusers - worth the money?

Postby Hugh Robjohns » Sun Jan 27, 2019 7:47 pm

To be fair, mention 'diffusor' to most people and they will automatically think of 'skyline' quadratic diffusers -- square arrays of different size blocks:

Image

... or finned diffusers with different size vertical slats.

Image

Few would ever think of flat/slotted diffusers, even though they are quite widely employed.

Image

(These all happen to be Gik products, but similar things are available from many other suppliers, or as DIY solutions)
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Re: Sound diffusers - worth the money?

Postby Random Guitarist » Mon Jan 28, 2019 11:30 pm

Is there much published on the design of slot diffusors?

I have found material on skyline and quadratics but nothing much on slots. A quick peruse of ebay showed some designs with even slot spacing and a couple with a more varied pattern.

Having a small cnc machine in the garage I'm finding making some a very interesting idea . . .
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Re: Sound diffusers - worth the money?

Postby Random Guitarist » Mon Jan 28, 2019 11:49 pm

Also this looks interesting. https://www.theengineer.co.uk/ultra-thin-diffuser-gives-clarity-to-sound/

If I'm understanding the basic premise correctly the new approach could have a 10cm thick panel (effective 9cm trap dpth) with diffusion effective to 200 Hz?

Or do I have that wrong?

Thanks, Grant.
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Re: Sound diffusers - worth the money?

Postby Wonks » Tue Jan 29, 2019 10:04 am

You're correct, though remember that diffusion is not absorption. It's spreading the reflected sound out so it goes in a wide spread of directions, rather than mainly reflecting off in one direction. So it's effectively trying to turn a flutter echo into a smoother, more reverb-like spread of smaller echos.

And in the example given in the article of 75Hz, the panel would still have to be at least 20cm deep, so not that practical for a small studio, where you'd be better off concentrating on bass trapping.
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Re: Sound diffusers - worth the money?

Postby Random Guitarist » Tue Jan 29, 2019 10:14 am

Yep understood.

I only have a small room but have a cloud over my head and treated reflection points, plus a fair bit of bass trapping. I like the idea of panelling some of the walls and if it can be acoustically useful so much the better.

I also like the look of some of these panels a lot, I am shallow.

Thanks, Grant.
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Re: Sound diffusers - worth the money?

Postby Martin Walker » Wed Jan 30, 2019 12:38 pm

Random Guitarist wrote:I only have a small room but have a cloud over my head

Same here, but sometimes it goes away and I feel creative :beamup:


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