Stone Walls In Studios/Live Rooms

#1

I have seen a few studios that have one wall that is made of stone, or faux stone, like this... STONE WALL

I love the look of something like this, but does it have any acoustical properties? Like, are you able to measure how something like this would effect the acoustics in a room? It seems like it's hard to control, compared to more common methods, but it looks badass.

This is sort of the idea I was thinking of going with. Build Thread. There are some good clear pictures half way down the page.

#2

It is an interesting and aesthetic solution that I would like to realize.

Personally, but I would prefer it to write someone who knows more than me, I think it would make sense if the use of this solution concerns only the walls that manage the first reflections, specifically for an RFZ I think it can only concern the front part appropriately and correctly inclined with respect to the listening point. I also believe that the result of the reflections that will derive from it will benefit from a scattering effect but ... I'm not sure.

All the best

Lucio

#3

I guess I should mention this would be for a live room. I want this to be the wall behind my drum kit. I want to put a skyline diffuser on the wall behind the kit, but the rest of the wall would be stone. Does the stone help? Hurt? Does it make things more complicated? Or is it just another way of treating the whole wall?

#4

I love the look of something like this, but does it have any acoustical properties?

Definitely it does! Depending on the dimensions of the stones and the depth of protrusion, you can get a rage of acoustic effects. Stone walls are highly reflective, of course, but flat ones with very little depth to them are pretty much specular, while ones that have large stones with angled faces and a lot of depth, are more diffusive. Or rather, they scatter more: diffusion is not the right word here (even though you see it thrown around). Irregular surfaces just scatter sound, which is similar to true diffusion, but not really the same.

So yes, if you wanted to use a stone wall, you certainly could, and you could decide on what you want it to do first, then look for the type of wall that will accomplish that in terms of stone dimensions and faces.

The only issue with having a very large stone wall surface in a studio, is that it might make the room too bright, and could produce unwanted reflections. As with all things acoustic, it's a good idea to balance the size and properties of the various parts of the room, to get the overall result that you are looking for.

I guess I should mention this would be for a live room. I want this to be the wall behind my drum kit. I want to put a skyline diffuser on the wall behind the kit, but the rest of the wall would be stone. Does the stone help? Hurt? Does it make things more complicated? Or is it just another way of treating the whole wall?

Drums can sound great in a room with a stone wall. Depending on how you set up the rum kit in relation to the wall, you can get a nice range of results (assuming that the room is large enough). However, I think you would not need a diffuser on that wall. Especially a skyline, which will produce uneven lobing artifacts out to about ten feet, and probably isn't needed there in any case.

Here's a room I did many years ago, with a stone wall on one side. This is a small isolation booth for tracking instruments, and the client didn't want it to sound small: he wanted it to be bright on one side, and more dead on the other, so we did a stone wall in there:

The first photo is the room under construction, the second is the finished room, and I think they were about to record some acosutic guitar in there right when this photo was taken: not sure.
The wall is small stones, with not much depth to them, so it only scatters high frequencies, while being reflective for mids and lows. There are windows in the room too, and the door has no treatment on it, so the room is quite bright. But walls are steeply splayed in this case, so is the ceiling, and there's plenty of absorption in many other places, so it works well.

In short: stone walls can do nice things, and they sure do look cool! Just choose the right stones for the job...

- Stuart -

#5

Soundman2020 wrote:The only issue with having a very large stone wall surface in a studio, is that it might make the room too bright, and could produce unwanted reflections. As with all things acoustic, it's a good idea to balance the size and properties of the various parts of the room, to get the overall result that you are looking for.

In short: stone walls can do nice things, and they sure do look cool! Just choose the right stones for the job...

- Stuart -

Hey Stuart,

Does it matter if they are real stone or faux stone? Or is it just important that the surface is irregular? ]

As far as the skyline diffuser, I wanted to use it because I like the aesthetics of it. Scroll down about half way on this studio webpage and you'll see what I'm trying to do. Skyline diffuser in the middle of the wall, but instead of cloth covering insulation on the walls, it would be the stone wall around the diffuser.

https://housefoxstudios.com.au/sydney-recording-studio

#6

Jag94 wrote:Source of the post Does it matter if they are real stone or faux stone? Or is it just important that the surface is irregular?

That depends on what you mean by "faux"!

There are some types of very fake "stone" that are basically just molded plastic, colored to look like stone, that are very light weight, thin, hollow, and you can stick them up with any old glue

but there are also others that are thin slices of real stone "veneer" that can be bonded to a backing, usually with thinset mortar or tile adhesive.

The very fake plastic, fiberglass or styrofoam ones aren't a lot of use: they will have some effect, yes, but they won't sound like real stone, for the same reason that tapping (with a small hammer) a tupperware container painted to look like stone, does not sound the same as tapping a real stone of the same size. The "veneer" stones are much better, and still cheaper than doing a "real" stone wall.

As far as the skyline diffuser, I wanted to use it because I like the aesthetics of it.

Ahh yes! The age-old question of aesthetics vs. acoustics! It might seem a bit harsh, but the question you should ask yourself here is: what is most important for your studio? Do you want it to sound as good as it possibly can, and still look good, or do you want it to just look good, with the acoustics not being too important?

There's a LOT of photos all over the internet of studios with rather questionable acoustic "decorations" that look wonderful, but clearly are not doing anything to improve the acoustics of the room, and often are doing the opposite: making them sound worse, even though they look good. Even some supposedly high-end very pro studios with big names on them, sometimes are guilty of doing strange things that don't make any sense, acoustically. The classic case is small bookshelf speakers on top of the console meter bridge in the control room, which is about the worst possible place you could put them, yet you see that all over. The good thing about that, is that the speakers will sound so lousy in that setup that if you can mix something to sound good on those, it should sound good anywhere! (many engineers do, in fact, set up their speakers like that for this specific reason: to see how the ix sounds on a lousy arrangement!). The other classic one, is a Schroeder or skyline diffuser directly behind the client couch, just a few inches back...

But getting back on track here:

The skyline in the photo seems to be some distance behind the drum kit, several feet at least: perhaps ten or even more... but its hard to judge just from the photo how far that is, since it is shot from a very low angle. Also, it is not up against a stone wall!

It seems to be in front of some type of absorber, and has absorbers on both sides, so this is a rather different situation from what you are thinking of. Adding a skyline that is tuned to high mids and highs (such as the one in the photo) on top of a flat stone wall might be an option, and could do something useful for the cymbals and the "snap" of the snare, but putting in front of a deeply textured stone wall, with large level differences, doesn't seem to be very effective. In both cases, the diffuser would hide most of the stone, so it wouldn0t even be visible.

Here's the issue with skyline diffusers (and indeed, most numeric-sequence diffusers):

The diffuser creates patterns of "lobes" up close to the face, and the actual diffuse field does not smooth out to an overall even level until several feet away. At least ten feet, regardless of tuning, and perhaps more if the low cutoff is tuned low enough. As you can see, if you move your head around up close to such a diffuser, you hear different things in different places. For a control room, that's a REALLY bad idea (yet you often see small controls rooms with QRD's on the rear wall... go figure! :shock:

). But for a live room, it MIGHT not be so bad, as long as you understand the issue, and position the instrument and mic carefully to get the effect that you are looking for. For an instrument such as guitar, cello, violin, flute or some such, where most of the sound comes from a small area of the instrument, that's fine. But for a drum kit, the sound comes from different places, all over! So the sound from the crash that hits the diffuser might be lobed in one way as it returns to one of the overhead mics, but the sound form the ride will have a DIFFERENT lobing pattern, and the hi-hat will be different again... as will the snare, splash, rack toms... The only one that won't be changed much, is the kick, and perhaps the floor tom, simply because they are so big, and emit sound from all over.

Here's why this happens: any form of numeric-sequence diffuser (1D, 2D, QRD, PRD, etc) changes the incoming sound in three different ways: time shift, phase shift, and direction shift:

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The incoming wave travels down all of the wells, and bounces off the bottom of each one, then exits again. But the part that hit a deep well takes a longer time to come back, thus it has been "temporally shifted": some parts of the wave came back sooner, others later. This is one form of diffusion. But since the waves coming back out of adjacent wells are shifted in time, they are also shifted in phase relative to each other, which means that they can partially cancel each other out, or reinforce each other, in varying patterns, depending on frequency, well depth, angle of incidence, etc. So phase shift is another form of diffusion. And finally, the interaction of the phase differences also causes some parts of the reflected wave to be steered in different directions form other waves. That's a third form of diffusion, called spatial diffusion. So the wave coming out is very complex, with different parts doing different things, and going in different directions at different times and with different phases. Thus, if you have your ear up close, within a few feet, you will hear different things in different places. Ditto for the mics! These differences do eventually even out, as the wave-front moves away form the diffuser, and at greater distances the wave-front is just plain "diffuse", and sounds roughly the same wherever you listen to it..... or wherever you place the mic in it.

Like I said, this is terrible for control rooms (yet you often see the client couch just a few inches away form a beautiful Schroeder on the back wall! :roll:

), but for a tracking room it MIGHT be OK, as you can put the effect to creative use, if you want to. The effect is subtle, but still interesting, and you can get some nice results with careful use. Or, for those who are not aware of this issue, they can get some pretty disgusting results!

So, it might be OK in your room... or it might not, depending on how you set things up. For a drum it, I'd be skeptical that you can get the entire it sounding fantastic in the mix if the kit is close to the diffuser and the mics are set back a bit to capture some room sound and bleed (which seems to be the case in the photo). On the other hand, if you close-mic the kit, then why bother with a diffuser at all?

I guess I'm not really giving you a concrete answer here, because there are many variables... and live rooms boil down to personal preference and taste. Rather, I'm just letting you know of the potential pitfalls that you should be aware of, when deciding how you want to treat your room.

- Stuart -

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