[jimbop]

I want to try some diffusion in the back of my room, but would like to experiment with something simple before spending the time and effort on building something complex. Any suggestions?

JD

[HAL]

Book shelves with staggard book binding depths work pretty well for a back wall diffusor.  It needs to be a lot of books and/or magazines. 

[rajacat]

Indoor plants in front of or on the back wall.

-Roy

[jimbop]

Thanks for the replies. The diffusors will need to be portable. They will go in front of a fireplace in one back corner and a glass door on the other side.

I've experimented with absorption in these back corners. It definitely helps with the soundstage but it dulls the sound. I'm prepared to build some diffusors, but (as I said) I don't want to build anything serious until I've had a chance to experiment a bit.

[richidoo]

Spend time research what type of diffusion you really want and are capable of building, then just build it with good materials. I don't see how else you're gonna be able to hear it without building it first?

You can't just fart around with simple designs and cheapo materials because each of those will drastically affect the performance of the diffusor. hard dense materials and proper design are required for you to hear what it will really sound like. For all the labor it takes to build a complex diffusor might as well do it as a final version the first time.

If you are making a vertical phase grate type you can glue together pieces of foam insulation board cut to each grate's depth and glue them together. But foam is too soft and light to reflect lower frequencies and the cut end is too grainy for high freqs, so it is not ideal material. But it might be easy because you can cut it with razor. I don't know how expensive that stuff is. They sell it home center.

[Ethan Winer]

You can't just fart around with simple designs and cheapo materials because each of those will drastically affect the performance of the diffusor.

I agree with this. Trying a bookcase with staggered books or CD cases is not at all like trying a real QRD diffusor.

--Ethan

[TitaniumTroy]

I would try a modular bookcase, you know the kind with one foot multiple cubes. Then fill it with large ceramic, or glass cylinder or orb shaped dust collectors. This idea came from a pretty smart guy over at the Audio Annex forum.

[Glenn Kuras]

You  may want to do some reading on diffusion to fully understand why book cases and something like plants will not work.
http://www.gikacoustics.com/news_011509.html


Glenn Kuras
GIK Acoustics

[Pez]

Get a couple of these:



They are designed with an asymmetry that breaks up soundwaves very efficiently. The carpeting on it prevents defraction and rarefaction. Couple warnings, they are ugly and heavy. Also if you own a cat, for some damn reason they refuse to stay away from them! Drives me nut, but I use one in my system it seems to do the trick.

[zybar]

Get a couple of these:



They are designed with an asymmetry that breaks up soundwaves very efficiently. The carpeting on it prevents defraction and rarefaction. Couple warnings, they are ugly and heavy. Also if you own a cat, for some damn reason they refuse to stay away from them! Drives me nut, but I use one in my system it seems to do the trick.

Can't see how that is going to really do anything, but would love to hear from the experts. 

Ethan, Glenn, Bryan, or other experts, any comments?

George

[Pez]

[zybar]

No problem...just looking to see some truth dispensed.   

George

[Pez]

Come on you know you can't get a straight answer on this from an acoustics expert it's long been known that the Cat tree industry is the single biggest threat to the audio diffuser makers.

[bpape]

You crack me up Pez. 

ANYTHIING that has HARD surfaces and is irregular will scatter waves based on it's size vs wavelengths in question.  This is not the same as diffusion which scatters evenly both in space and in time.  Sure - some things will act better than a hard surface in terms of pure slap echo but may cause other problems in the process.

Books are effectively slightly absorbent - the exact opposite of diffusive.  Cat tree - well, it's certainly random but is again covered in soft material that is absorptive, the opposite of diffuse.  The whole point of diffusion is to scatter sound in time and in space but without losing energy in the process.

Want something cheap?  Bend a piece of plywood, put a brace under the center of it and tack the 2 edges to the wall, forming a shape similar to a poly.  Fill the rear with insulation to stop it from ringing and to provide a slight amount of lower end control.  Frequencies absorbed - pure guess.  Variables include width, depth, and thickness/density of the plywood.  Shallower spaces and thinner wood move frequency up. Deeper space and thicker lowers frequency but at the expense of efficiency per square foot in terms of absorption.

Bryan

[PLMONROE]

Indoor plants in front of or on the back wall.

-Roy

Roy is right. For "quick and dirty" take a lesson from some of the shows.  Go to Walmart, Hobby Lobby, Michaels, or wherever and get some artificial (plastic) plants. They won't match commercial treatments but work well, give you flexibility, and can look great!

Paul 

[Ethan Winer]

Can't see how that is going to really do anything, but would love to hear from the experts.

I took that as a joke, George. But you're right - that's not a diffusor because it absorbs mid and high frequency waves more than it scatters them. This might be a better diffusor (sans cat):



--Ethan

[bpape]

I dunno - the cat looks pretty random to me 

[nwboater]

Want something cheap?  Bend a piece of plywood, put a brace under the center of it and tack the 2 edges to the wall, forming a shape similar to a poly.  Fill the rear with insulation to stop it from ringing and to provide a slight amount of lower end control.  Frequencies absorbed - pure guess.  Variables include width, depth, and thickness/density of the plywood.  Shallower spaces and thinner wood move frequency up. Deeper space and thicker lowers frequency but at the expense of efficiency per square foot in terms of absorption.

Bryan

There's a fellow on the Klipsch Forum - artto - who years ago put lots of diffusion in his Klipschorn room using large Masonite panels as Bryan described. I believe he did later add some absorbent material behind the panels.

He claims to have an incredibly realistic sounding room, and much larger sounding than the room actually is.

Rod

[jk@home]

OK we're talking temporary here, right? As in just getting a quick idea of reflection vs absorption, left up for a few days or so?

How about (large) bubble wrap...

http://www.starboxes.com/bubble-wrap.aspx?gclid=CJCqy8iE76cCFRphgwod8lTzZA

taped on to foam attic channel...

http://www.homedepot.com/buy/building-materials/insulation/22-in-x-48-in-durovent-attic-ventilation-system-20977.html

Blue taped to the walls, or just leaning up against.

What ya think?

[Ethan Winer]

What ya think?

That's not likely to do much useful, and it certainly won't be a diffusor.

--Ethan