The sound of diffusion

[Ethan Winer]

Folks,

I wasn't sure which section to post this, but hopefully it's okay here.

A lot of people have never had a chance to try diffusion, to compare how it sounds versus absorption or a bare wall. So yesterday my partner Doug and I made a short video showing exactly this. To amplify the effects we put the microphone and an acoustic guitar 6 inches away from a bare wall, diffusion, and absorption. This makes it very easy to hear exactly how each surface type sounds. We also recorded the microphone and guitar out in my large live room away from all surfaces (except the wood floor). This new video is near the bottom of the list on my company's Videos page:

RealTraps - Videos

--Ethan

[Drumsound]

That's pretty interesting to hear. Thanks Ethan.

How would they sound over the mix position?

[u b k]

fascinating. i like the diffusion and the 6" from the bare wall equally. the diffusion is, well, it's diffuse. the bare wall has more of an immediacy, a punch which i assume is the wicked fast early reflections.

absorption was horrendous, in-the-room was bad as well.

cool video!


gregoire
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ubk
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[True North]

Very cool, thanks for posting the test Ethan

The diffusor clearly sounded best to my ears.

[gainreduction]

That's fascinating.

Cool to be able to (sort of) A/B room treatment methods.

Diffusion is the clear winner in my book. Absorbtion was muddy and lifeless in comparison.

Ethan, how deep must the diffuser be to be effective way down the freq spectrum ?

Are those diffusers combined with absorbtion or is it diffusion only ?

Cool video, thanx for the effort.

[jayfrigo]

And generally speaking, diffusion will only get better with some distance from it. It gets more even and uniformly distributed with greater than 6" distance. Neat idea for a video, but of course, keep in mind the limitations of such a demonstration. A stereo recording might be more telling than a mono recording. Still, great way to give a first impression to those without experience hearing diffusion.

[jahala]

In the example, diffusion sounded best overall. But I think a well planned blend of diffusion, absorption and reflection is the key to any good, natural sounding room.

- J.

[SpiderM69]

Interesting video. What I couldn't tell is, is the mic pointed at the wall/diffusor/absorber, or at the guitar? It appears the mic is angled towards the wall, as is the guitar.

What are you using as an absorber? That could say a lot about what frequencies are being attenuated most.

To answer the question in the video, I don't know what sounds the most natural because I wasn't in the room. Which do you think sounds the most natural?

The diffuser had the most lows and highs, midrange sounded more prominent with the bare wall, according to the speakers I was using (not studio monitors).

I also wonder how much the wood floor influences. Meaning, for those of us with home studios that are carpeted, is a diffusor really going to make that much difference? I recently bought a chair mat with wood laminate, and that made a big difference. I have my doubts that diffusion will do much good if your room's carpeted. But then again, this is High End Forum, isn't it .

[greatgreatriver]

The dolls made me scared - first I thought it was real people but they didn't move to the music so I was forced to think again and after a while the camera zoomed in on the dolls and I could see it was not real people.

[666666]

Interesting. Each example has a different eq shape... the various surfaces are absorbing / reflecting different frequencies.

Indeed the foam has sucked away any trace of pleasing upper frequencies. The eq shape is warped and unflattering. This is the least natural sound, and quite poor.

The bare wall example is quite bold, thick mid-range, decent highs (though a little sloppy due to the slap), this may actually be somewhat flattering to that instrument depending on the context, but I'd be concerned about possible phase issues, plus you may not want such a defined room slap depending on what you're doing. Not too bad though... but may be way worse with a different source or with a slightly different mic position. It IS a bit honky, but again, I could hear this working depending on the mix / situation.

The diffussor example... interesting. More highs than I'd expect. Plenty of tight low end. Mid-range is not too strong, has a bit of a "scooped out" character, but this may be an exaggerated perception after hearing the mid-range heavy bare wall example. Overall pretty clean and tight, quite natual sounding.

Which sample sounds most "natural"?... that's a bit tough... I'd say the diffusor example does, followed closely by the bare wall. This is subjective since it depends on how one "hears" a guitar like that. A lot of people are used to hearing a guitar near a bare wall (like when they're practicing in their small practice room), so the bare wall example might almost seem more "natural" for some. But, you surely hear the slap from the wall in that example... so if by "natural" we mean "guitar only with no outside interferance", then the diffusor example surely wins.

Hard to judge if the eq response in the diffusor example is "true" to the instrument itself... we could not know unless we were there hearing the guitar in the room from different positions, up close, farther away, etc.

I am impressed at the upper end response of the diffusors though compared to the absorber. This example clearly shows that if you need to treat a room like that, a diffusor is indeed a way better option than foam. Whether or not the diffusor is sending back an "accurate" signal, it's still better than foam. The diffusor overall is a lot tighter and cleaner than the bare wall too, so... the diffusor wins!

I am wondering though how this test would have gone with a very bass-heavy instrument... I suspect extra bass trapping wound have been needed. Probably would have needed a few regular Real Traps BEHIND the diffusor panels perhaps.

Ethan, I'd be very interested in hearing how your regular Real Traps compare in this same type of test. I am quite curious as to the reflection properties, if any, of the regular Real Traps, and the realistic eq curve they send back into the room. I'm sure there'd be less high-end being sent back than with the diffusors... but... would be really neat to hear.

Tech data, charts, graphs etc are great, but there's nothing like actually hearing stuff... which is why I applaud you for doing these tests and posting... thanks!

[Ethan Winer]

Originally Posted by gainreduction

Ethan, how deep must the diffuser be to be effective way down the freq spectrum ?

The deeper the wells, the lower they diffuse to. But diffusion at bass frequencies is not useful. That requires absorption for best results.

Are those diffusers combined with absorbtion or is it diffusion only ?

Our diffusors are also bass traps, transitioning in the range from 400 to 800 Hz. That's why we call them "the ideal rear wall" on our product description page:

RealTraps - Diffusor

But I didn't post video this to spam the forums! It seemed the best way to let people hear what diffusors "sound like" without actually being in the room with them.

--Ethan

[Ethan Winer]

Steve,

Originally Posted by SpiderM69

What I couldn't tell is, is the mic pointed at the wall/diffusor/absorber, or at the guitar? It appears the mic is angled towards the wall, as is the guitar.

As explained in the text on our Videos page, next to the video links:

"The microphone is an audiotechnica 4033 pointed toward the guitar, and no EQ or other effects were used."

What are you using as an absorber? That could say a lot about what frequencies are being attenuated most.

That's two panels of 703, placed adjacent to be 4 feet wide and 7.5 feet high. Don't get too carried away with the "sound" of absorption because nobody would have any of those surfaces so close to a microphone or sound source. Again, this was done to exaggerate the effect to make it easier to hear.

Which do you think sounds the most natural?

That is the correct question.

Out in the room sounded most natural in person, even if it sounded a bit thin on the video.

for those of us with home studios that are carpeted, is a diffusor really going to make that much difference?

It certainly could. In fact, the main appeal of diffusion is to avoid the boxy sound of comb filtering off a bare wall, but without further deadening the room. Likewise for taming flutter echo without needing absorption. The main drawback of diffusion is it's expensive. Good diffusion costs more than good absorption.

--Ethan

[Ethan Winer]

Originally Posted by 666666

Probably would have needed a few regular Real Traps BEHIND the diffusor panels perhaps.

This is a big feature of our diffusors - they transition to being bass traps below the range they diffuse. But the point of this was to show how the diffusion sounds, and using a bass instrument would have been below the range of effective diffusion.

Ethan, I'd be very interested in hearing how your regular Real Traps compare in this same type of test. I am quite curious as to the reflection properties, if any, of the regular Real Traps, and the realistic eq curve they send back into the room. I'm sure there'd be less high-end being sent back than with the diffusors... but... would be really neat to hear.

That would be tougher to post as an audible example. They do have a very specific curve of absorption versus frequency, but where they don't absorb they simply reflect.

Thanks for all the comments guys. That makes it all worth doing!

--Ethan

[666666]

Thanks Ethan.

Not to stray too far off, but...

Let's say you had a room about 12' X 20' and low ceiling, all sheetrock.... and you place a drum kit right in the middle (drum kit being a source that covers the entire frequency spectrum from ultra lows to ultra highs, high SPLs.

What sonic treatment might you recommend, generally speaking, for the above example, in terms of your products? What percentage of diffusors verses Real Traps bass traps? And of those, what percentage of the walls / ceiling should be covered, 100%, 50%, etc?

I'm just trying to get an idea of how effective the diffusors absorb low-end, and/or how much diffusion makes sense to have in a SMALL room with a loud wide-spectrum source (like drums).

I'm sure there IS an ideal ratio of diffusion to absorption in a case as described above. Or would you stack diffusors on top of bass traps and cover the entire room (so that the ultra lows are absorbed but the upper end is diffused too)? We of course need to address the areas below 400Hz as well as diffuse the upper stuff. I'm sure it gets tricky when dealing with small spaces.

[Mike Caffrey]

Regardless of preference, it's really impressive how big a difference there was and this was fairly low quailty audio, and I was listening on a laptop.


There are times where I ahve recorded with a mic and souce that close to absorbtion - when going for an exageratedly dry vocal.

Some of the dryness came from the absorbtion, but I htink the besst effect was due to mechanically cutting out room reflections.

Do you have any prediction on how it would sound if I had surrounded the vocalist with diffusers to cut out the room sound?

I have one iso room that I use only for for certina things because I don't like the way it resonates on guitar amps. It hadn't really occured to me to line it with diffusion.

What are your expereinces with diffusion in small spaces/iso rooms.

Have you seen the Demeter Silent Speaker Cabinet? I got one when they first came out, but I hated it because of it's resonanace. If that had had diffusion, do you think that would have helped in such a tiny space?

[666666]

Originally Posted by Mike Caffrey

Have you seen the Demeter Silent Speaker Cabinet? I got one when they first came out, but I hated it because of it's resonanace....

I used one once and it just totally did not work. It was impossible to get any kind of decent sound... the space inside the cabinet is just TOO small. I personally don't think any amount of absorption, diffusion etc can ever help that situation (inside the cab)... there's just no space.

All I could achieve with that tiny Demeter cab was a very warped phasey honky boxy sound. Was very unnatural, and just plain yucky. I had not initially perceived it as cabinet resonances, but perhaps that was indeed part of it. Demeter gets an A+ for the concept, but the product is an F- in terms of real-world professional use.

I would sell that Demeter thing if you can, get a REAL speaker cabinet, and surround it with appropriate sonic treatment... which I'd think would be just absorption. I know when I'm close miking a speaker cone, I want a direct cone sound and NOTHING else, no nearby reflection, diffusion, nothing... there should be no waves bouncing back toward that mic, not even diffused waves. If the speaker is cranked and the mic is up close and pointing in, surrounding diffusion may not even be heard by the mic anyway. Distant miking the cab is another story.

[roscoenyc]

Originally Posted by 666666

I used one once and it just totally did not work. It was impossible to get any kind of decent sound... the space inside the cabinet is just TOO small. I personally don't think any amount of absorption, diffusion etc can ever help that situation (inside the cab)... there's just no space.

All I could achieve with that tiny Demeter cab was a very warped phasey honky boxy sound. Was very unnatural, and just plain yucky. I had not initially perceived it as cabinet resonances, but perhaps that was indeed part of it. Demeter gets an A+ for the concept, but the product is an F- in terms of real-world professional use.

I would sell that Demeter thing if you can, get a REAL speaker cabinet, and surround it with appropriate sonic treatment... which I'd think would be just absorption. I know when I'm close miking a speaker cone, I want a direct cone sound and NOTHING else, no nearby reflection, diffusion, nothing... there should be no waves bouncing back toward that mic, not even diffused waves. If the speaker is cranked and the mic is up close and pointing in, surrounding diffusion may not even be heard by the mic anyway. Distant miking the cab is another story.

i have a demeter cabinet. i was using it w low power amp heads for 'guide electric guitars' when cutting tracks. it did sound boxy.

recently i started using it w the Dr Z Trainwreck "Air Brake" attenuator. Whole different ballgame when the box isn't being driven so hard. I wouldn't put a ribbon mic in the demeter cab but a dynamic like a 409 w the Air Brake gets a very usable a close mic guitar sound.

[Ethan Winer]

Originally Posted by 666666

Let's say you had a room about 12' X 20' and low ceiling, all sheetrock.... and you place a drum kit right in the middle

You generally want to avoid being in the exact middle of any room that size because that's a null spot for bass. Even a foot off center is a lot better.

That said, diffusion is best used at least a few feet away from both the microphones and sound source (drums in this case). But even six inches away is a lot better than the same distance to a bare wall. The photo below shows our diffusors put to good use in a drum room.

What sonic treatment might you recommend, generally speaking, for the above example, in terms of your products? What percentage of diffusors verses Real Traps bass traps? And of those, what percentage of the walls / ceiling should be covered, 100%, 50%, etc?

My first question for you has to be "How much are you looking to spend?" I hate to sound like a car salesman! But my advice for someone with $800 is very different than for someone with $8,000. If you're more toward the low side I'd recommend absorption only. If you have the budget for "really good" I'd suggest a mix of bass trapping, diffusion, and absorption. With a low ceiling you mostly want absorption over the drums assuming you're using overhead microphones.

--Ethan

[u b k]

Originally Posted by Ethan Winer

Don't get too carried away with the "sound" of absorption because nobody would have any of those surfaces so close to a microphone or sound source.

isn't that how the se reflection filter and your portable vocal booth are used? aren't they absorbers?


gregoire
del
ubk
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[Mike Caffrey]

Originally Posted by 666666

I used one once and it just totally did not work. It was impossible to get any kind of decent sound... the space inside the cabinet is just TOO small. I personally don't think any amount of absorption, diffusion etc can ever help that situation (inside the cab)... there's just no space.

All I could achieve with that tiny Demeter cab was a very warped phasey honky boxy sound. Was very unnatural, and just plain yucky. I had not initially perceived it as cabinet resonances, but perhaps that was indeed part of it. Demeter gets an A+ for the concept, but the product is an F- in terms of real-world professional use.

I would sell that Demeter thing if you can, get a REAL speaker cabinet, and surround it with appropriate sonic treatment... which I'd think would be just absorption. I know when I'm close miking a speaker cone, I want a direct cone sound and NOTHING else, no nearby reflection, diffusion, nothing... there should be no waves bouncing back toward that mic, not even diffused waves. If the speaker is cranked and the mic is up close and pointing in, surrounding diffusion may not even be heard by the mic anyway. Distant miking the cab is another story.

I sold mine about nine years ago.

[jayfrigo]

Originally Posted by Ethan Winer

The deeper the wells, the lower they diffuse to. But diffusion at bass frequencies is not useful. That requires absorption for best results.

That's a bit too much of a blanket statement for me, but since most here are thinking of small control rooms and project studios and such, and if you're talking about things below 2-300 Hz in that application, it's probably a reasonable thing to say. However, diffusion in the middle hundreds can still be useful in music studio applications, and in large rooms, diffusion at lower frequencies can be quite useful. As the cutoff frequency decreases with the increase of room size, the modal density increases and the need for bass absorption decreases, and indeed in performance halls, you want to keep all the bass you can.

[Glenn Kuras]

Originally Posted by u b k

isn't that how the se reflection filter and your portable vocal booth are used? aren't they absorbers?


gregoire
del
ubk
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Products like those are made to be used out in the room.

[RKrizman]

Great video. I can't believe the difference in sound from the diffusors. However, it seems to be the one track that stands out as different from all the other, to my ears, so I'm wondering if that is the "true" sound of the guitar or if the diffusor is coloring it.

That said, I like it.

-R

[yeloocproducer]

shameless plug... I've got 3 maple diffusors in the classifieds right now (LA area)...

http://www.gearslutz.com/board/gears...empirical.html

back to your regularly scheduled program...

[SpiderM69]

So, Ethan, a few questions.

How would you compare your diffusors to the Auralex SpaceArray, other than the obvious difference of bass trapping included?

For the smaller room version (<6 ft), how much distance is needed for the diffusor to be effective?

Where is the best placement for diffusion for tracking, if you're limited as to the number of diffusors, and you have a small/smaller room? Directly behind the source if vocal? Facing the source for acoustic guitar, stand up bass, etc? Behind the source for drums? Etc. Or is it always where the mic is pointing (if cardiod or fig 8)? I guess a more general way to ask this question is it better for the diffusor to diffuse reflections, or the sound prior to reflection, for tracking?

Thanks,

[Ethan Winer]

Originally Posted by u b k

isn't that how the se reflection filter and your portable vocal booth are used? aren't they absorbers?

LOL, I was waiting for someone to point that out!

Yes, but two points:

1) In the case of our PVB (the SE device isn't really an absorber) it's a necessity, and the only way to get rid of room tone when treating the room correctly isn't an option.

2) When a microphone is used with our PVB, it's generally a cardioid set to point away from the absorption. So the close proximity is less of an issue.

--Ethan

[Ethan Winer]

Originally Posted by jayfrigo

That's a bit too much of a blanket statement for me, but since most here are thinking of small control rooms and project studios and such

Exactly.

[Glenn Kuras]

Originally Posted by RKrizman

Great video. I can't believe the difference in sound from the diffusors. However, it seems to be the one track that stands out as different from all the other, to my ears, so I'm wondering if that is the "true" sound of the guitar or if the diffusor is coloring it.

That said, I like it.

-R

Well with the mic that close to the wall I would say it's not the "true" sound but more of the diffusor. I think it is worth pointing out that I don't think Ethan is trying to be all scientific with this test (Ethan correct me if I am wrong). All Doug (the guy jamming the blues) would need to do is move to the left or right, just a little and the sound would have changed. But I think it is great Ethan went through all of this to show the different sounds.

Glenn

[Ethan Winer]

Originally Posted by SpiderM69

How would you compare your diffusors to the Auralex SpaceArray, other than the obvious difference of bass trapping included?

Our diffusor is 6 inches deep, so it diffuses to a much lower frequency.

For the smaller room version (<6 ft), how much distance is needed for the diffusor to be effective?

This too is a function of the well depth. A good rule of thumb is one foot of distance for each inch of depth. We offer our diffusors in both far and near models. The well depth of the near model is 3 inches, but the overall depth is still 6 inches so there's less diffusion and even more bass trapping.

Where is the best placement for diffusion for tracking, if you're limited as to the number of diffusors, and you have a small/smaller room? Directly behind the source if vocal? Facing the source for acoustic guitar, stand up bass, etc?

It's hard to say without actually being there. For a given number of diffusors you'll do best to put them together on one or more walls, versus one alone on each wall. Then you'd experiment a bit and see what sounds good where in relation to the diffusors. The photo I posted earlier shows a good application of diffusion in a live room.

--Ethan

[Ethan Winer]

Originally Posted by RKrizman

I'm wondering if that is the "true" sound of the guitar or if the diffusor is coloring it.

The truest sound is the guitar out in the room. It's not a great guitar, and the strings are about a year old.

(It also would have helped if I played the guitar rather than my partner. )

There's no question that diffusion only 6 inches away from a microphone and/or instrument colors the sound. The main point is that it colors the sound less than a bare wall, and the coloration is more flattering than a bare wall. That, and it avoids flutter echo and comb filtering but without making the room too dead as can happen with absorption.

--Ethan