John Sayers' Recording Studio Design Forum Archive

So having spent another week reading extensively here, and researching my situation:

* No tuned / panel traps. Just absorption. I've read countless places here that my room is too small for those, and that's fine by me.
* If I've interpreted my REW correctly (big IF) it seems that my big 99hz null is SBIR. There's a big change in the phase graph at that point. I guess it either comes from the ceiling or the floor.

My next steps will probably be:
* Panels on the first reflection points on the side walls
* Hard-backed cloud
* Add plastic covering to some of the absorption I've already done.

I have a couple of points I'm not quite sure on.

Side Wall Panels
60cm x 120cm panels. These could be 100mm thick, and spaced away 100mm from the wall. I've read this recommended in other threads.
Or: they could simply be 200mm thick. Do I get more bang for my buck by making them thicker?
I'm guessing these shouldn't be covered in plastic, as we don't want anything reflecting from here.

Ceiling cloud
From reading here I understand the key points should be:
* 15mm ply hard back
* at least 12deg angle (lower edge toward front wall, higher edge towards rear wall)
* Fixed to the ceiling joists theatre rigging style - with closed-loop bolts, no open hooks - rated for 10x the weight.
* 100mm absorption on underside covered by thin plastic then fabric
* more absorption on the top.

I'm unsure about:
* The angle. Steeper than 12deg is fine - should I go steeper if possible?
* I have plenty of RW45 offcuts. I could bag them up and stuff them above the cloud to make it almost like a superchunk up there if this is advantageous.
* As I have such a small room, I could extend this cloud all the way to the front wall. it would span the gap between the two front corner superchunks. Is this a good idea, or should I make a superchunk for the front wall top edge, and have the cloud smaller.

Plastic coverings
* I've read to use the thin plastic that painters use for drop-cloths
* I'm guessing I should cover the whole back wall absorption with this.
* And the cloud
* I don't know whether to cover the front wall superchunks with plastic?
* I quite like the idea of putting some wide slats up (spaced far enough apart to avoid becoming tuned resonators). Are these necessary as well as the plastic? Maybe we won't know til testing with the plastic.

That's where I've got to so far.
I've not read anything that contradicts this (I think!!!!) but maybe my plans could be tweaked. Any ideas very welcome.

Owen

Here's a sketchup of the cloud idea. And here with the addition of rockwool off-cuts in polythene bags, stuffed up and hidden away above the cloud, if that is effective in any way.
I've got loads of off-cuts, I could pretty much fill that space I think.

Just a wee nudge for this one.

Looks like I’ve got a bit of non-fatherhood time this weekend, and even a willing helper / rockwool-cuttter in my songwriting partner, so I’m planning to get make some progress on the treatment building.

My panels and cloud plans seem sound from what I can work out, but any problems that might be spotted by those in the know would be brilliant, before I start cutting wood and drilling holes

Do some ray tracing and check the angle of your cloud. Use the cloud to deflect sound into your back wall, that would be the goal.

Greg

Gregwor wrote:Do some ray tracing and check the angle of your cloud. Use the cloud to deflect sound into your back wall, that would be the goal.

Greg

Cheers - will do.
I’ve just been reading your posts about ray-tracing in sketchup. Looks like that’ll be a learning process (as everything in sketchup is!)

I should have some time in hand to do that, as the angle of the cloud is less critical to work out right now it think, as i can change it easily enough by adjusting the chain length later.
It’s more the general design and principles of the cloud and panels that I want to check, before the power tools come out and I start getting all excited.

* If I've interpreted my REW correctly (big IF) it seems that my big 99hz null is SBIR. There's a big change in the phase graph at that point. I guess it either comes from the ceiling or the floor.

Probably floor bounce. That's a fairly common situation, even in pro studios. You can check if that's the case by piling up some thick absorption in the floor between the speakers and the mic. If the dip goes away, then that's very likely what it was. If it doesn't, then I'd suspect rear wall.

60cm x 120cm panels. These could be 100mm thick, and spaced away 100mm from the wall. I've read this recommended in other threads.

:thu;

Or: they could simply be 200mm thick. Do I get more bang for my buck by making them thicker?

Usually, yes. They will then act down to much lower frequencies, assuming that the angle of incidence isn't too high, but even then you'd probably get a good boost in overall low frequency absorption... especially if you leave the edges of the panel open to the room, or mostly open.

* 15mm ply hard back

Minimum! It doesn't have to be ply: MDF and OSB are fine too.

* at least 12deg angle (lower edge toward front wall, higher edge towards rear wall)

As Greg said, you'd need to ray trace to find out if that is enough, but it does not NEED to be 12°: it's not for flutter echo, and even if you did have a flutter echo problem, the absorption below the hard back would take care of that.

* Fixed to the ceiling joists theatre rigging style - with closed-loop bolts, no open hooks - rated for 10x the weight.

* 100mm absorption on underside covered by thin plastic then fabric
* more absorption on the top.

* The angle. Steeper than 12deg is fine - should I go steeper if possible?

12° is already pretty steep. Going too steep with a large cloud can make the room looks strange. Another option (if you do need a very large angle) is to have two or three smaller clouds, or even to have panels as part of the cloud that are angled more than the cloud itself.

* I have plenty of RW45 offcuts. I could bag them up and stuff them above the cloud to make it almost like a superchunk up there if this is advantageous.

Save that for your speaker soffits (assuming you are going to soffit-mount...)

* As I have such a small room, I could extend this cloud all the way to the front wall. it would span the gap between the two front corner superchunks.

Not necessary, and it might look strange. As long as it covers most of the area between the speakers and the desk, that's fine. If you really like making clouds, then you could put another one at a flatter angle above the mix position.

* I'm guessing I should cover the whole back wall absorption with this.

Maybe, but be careful. Plastic is technically a "foil", and it does have a certain tuning effect. If you cover a large area with the same thickness of plastic, then you create a large area that reflects one range of frequencies very well, and absorbs another range very well. That can color the sound of the room. You might need to vary the thickness, or the coverage area, or both.

* I don't know whether to cover the front wall superchunks with plastic?

Probably not necessary, but you could if you are worried about fibers.

* I quite like the idea of putting some wide slats up (spaced far enough apart to avoid becoming tuned resonators). Are these necessary as well as the plastic? Maybe we won't know til testing with the plastic.

I'm not sure if yo are following the "Room Tuning" thread, but it might be really interesting for you: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368

Here's a sketchup of the cloud idea.

I would split that in half horizontally into two clouds: One running at a larger angle between the speakers and toward the desk, the other mostly above the desk at a smaller angle.

And here with the addition of rockwool off-cuts in polythene bags, stuffed up and hidden away above the cloud, if that is effective in any way.
I've got loads of off-cuts, I could pretty much fill that space I think.

It's worth a try, as long as you don't pack the off-cuts in the bags too tightly. You don't want to compress them too much.

- Stuart -

Thanks Stuart - all really helpful.

Soundman2020 wrote:

RKML wrote:Or: they could simply be 200mm thick. Do I get more bang for my buck by making them thicker?

Usually, yes. They will then act down to much lower frequencies, assuming that the angle of incidence isn't too high, but even then you'd probably get a good boost in overall low frequency absorption... especially if you leave the edges of the panel open to the room, or mostly open.

Cool - I've done this.

Plastic is technically a "foil", and it does have a certain tuning effect. If you cover a large area with the same thickness of plastic, then you create a large area that reflects one range of frequencies very well, and absorbs another range very well. That can color the sound of the room. You might need to vary the thickness, or the coverage area, or both.

I'm not sure if yo are following the "Room Tuning" thread, but it might be really interesting for you: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368

Ah - really interesting - thanks. I'll read that thread thoroughly. Had a look at it before - but its becoming really relevant now - the plastic thickness and coverage topic.

I would split that in half horizontally into two clouds: One running at a larger angle between the speakers and toward the desk, the other mostly above the desk at a smaller angle.

So I've had a go at the ray-tracing, and I think I'm getting the maths / angles right. (Thanks Greg, for your posts on this - it's a tricky learning process in Sketchup.)
I'm not sure I'm quite getting the concept right though.
I was under the impression that the purpose was to fire the reflections past the engineer, and into the back wall.
However I go about it though, I always have reflections hitting the mix engineer's head.
In this sketch, the cloud above the engineer is at 6deg, and the cloud above the speakers is all the way at 24deg, and it still doesn't seem to be steep enough. Am I missing something here?
It seems like, to get all the reflections from the above-speaker cloud to miss the mix engineer, the cloud would almost have to be 45deg, or more, with the bottom edge almost touching the speakers.
I don't mind building that, if that is what works, it just seems like I must have this wrong?

Cheers,

Owen

Even with this one - the above-speaker cloud is at 38deg, the poor old mix guy takes it in the face.
I've got to be getting something wrong here?

Even with this one - the above-speaker cloud is at 38deg, the poor old mix guy takes it in the face.

It makes you realize how much easier designing a room would be with a really tall ceiling hey?

I FINALLY got my angles worked out how I like them. I will try and post pictures on my thread tomorrow. The trick is trying to make it look good while still functioning. If I remember correctly, I had to have 2 separate angles before hitting my main "flat-ish" ceiling. I also had to move my mix position to somewhere around 33% of the room depth. That was mostly due to the side wall issue, but it might help you with your ceiling issue. I've read Stuart write several times that getting wall and ceiling angles right takes a lot of tweaking and time. I suppose it's somewhat of a juggling act between a handful of factors (speaker position in the bezel in relation not only to the soffit wall but the side walls and front room corners, soffit wall angle, soffit wing angle, head position - depth within the room, entire front deflective surface wall depth from your front inner leaf, then of course your ceiling. Beyond that, you have to consider furniture positions in relation to your mixing space and whether or not you will have room to have a guitarist or pianist able to track their parts at your side. I could keep going, but obviously, being able to sort this out on a computer before building it sure is handy!

Keep tweaking things and I'm sure it will come together for you. You're on the homestretch!

Greg

Cheers Greg, I really appreciate the encouragement.

Gregwor wrote:
It makes you realize how much easier designing a room would be with a really tall ceiling hey?

Yeah - I can see doing this that 90% of my trouble here is just that I have a tiny room.

Gregwor wrote:I FINALLY got my angles worked out how I like them. I will try and post pictures on my thread tomorrow. The trick is trying to make it look good while still functioning. If I remember correctly, I had to have 2 separate angles before hitting my main "flat-ish" ceiling

Yeah, I'd like to see that if you get a chance. That would be great.
It'll be interesting to see other ways of getting round the problem.

Gregwor wrote:obviously, being able to sort this out on a computer before building it sure is handy!

Yeah, and I'm starting to get there with Sketchup. It's certainly 'quirky'.
90% intuitive and 10% infuriating. I've worked out how to lock the protractor on the incident angle using the shift key now. There was some colourful Welsh language swearing floating through the air in my house up until that point...

I have spotted somewhere that I'm gong wrong though I think. I have my ray trace in sketchup reflecting off the lower edge of the cloud, the rockwool. This isn't right though is it? The sound wave will be reflecting off the plywood.
If I change the ray trace to reflect that, it actually makes a difference. The extra 10cm height gets pretty much all the sound shooting over the engineer's head if I stick with the 38deg angle.
It's pretty crazy steep, but I'll tweak a bit more to see if I can get it looking a little slicker.

I'll definitely be waiting for a 'yes you're on the right track' from Stuart before I start cutting wood though....

Gregwor wrote: Keep tweaking things and I'm sure it will come together for you. You're on the homestretch!

Greg

Cheers!! Fingers crossed...

The sound wave will be reflecting off the plywood.

Correct.

I am working on my design right now. I'm trying to overcome newly discovered issues with my conduit now that I physically have the DB2 conduit in hand. I'll update my post once I sort this crap out.

Greg

The sound wave will be reflecting off the plywood.

I really hate to throw yet another complexity into the mix, but there's another issue at play here. Yes, LOW frequencies will be affected mostly by the hard back of the cloud, but HIGH frequencies hitting the face of the insulation at high angles of incidence are rather likely to reflect off that face, to a certain extent... The impedance change occurs at the interface between the air and the insulation.

Then there's the issue of speaker dispersion: no studio monitor puts out all frequencies equally at all angles: the vast majority tend to focus the highs in a tightish "beam" covering up to maybe 20°, 30°, 40° (depends on the speaker), with the mids hitting a wider angle than that, maybe 50°, 60°, 70° off axis, and the lows wrapping all the way around, of course.

So: you need to look at your speaker's dispersion pattern vertically, to see what frequencies are going to be hitting your cloud, and your side-wall panels (if you have any), then based on that, try to figure out if that sound is going to be bouncing off the face of the insulation, or the hard back. From the steep angles that I see on your images, I'd suspect that it's mostly low-mids that are going to be hitting the front module, so consider the hard back....

Then to REALLY complicate the issue, consider that the lower the frequency, the less sound acts like rays in any case, and the more like a shotgun blast, spreading out as a broadly angled reflection, not a specular reflection, and attenuated by the insulation anyway... and also starting out at a lower intensity to begin with, because it is off-axis....

So yeah, it can get complex if you REALLY want to get into all the nitty gritty! details!

Sorry to dump all this stuff on you suddenly like that! And it's probably not really necessary to go jumping it all of that, unless you are build a really high precision room, but it's food for thought...

- Stuart -

Soundman2020 wrote:

The sound wave will be reflecting off the plywood.

I really hate to throw yet another complexity into the mix, but there's another issue at play here. Yes, LOW frequencies will be affected mostly by the hard back of the cloud, but HIGH frequencies hitting the face of the insulation at high angles of incidence are rather likely to reflect off that face, to a certain extent... The impedance change occurs at the interface between the air and the insulation.

Then there's the issue of speaker dispersion: no studio monitor puts out all frequencies equally at all angles: the vast majority tend to focus the highs in a tightish "beam" covering up to maybe 20°, 30°, 40° (depends on the speaker), with the mids hitting a wider angle than that, maybe 50°, 60°, 70° off axis, and the lows wrapping all the way around, of course.

So: you need to look at your speaker's dispersion pattern vertically, to see what frequencies are going to be hitting your cloud, and your side-wall panels (if you have any), then based on that, try to figure out if that sound is going to be bouncing off the face of the insulation, or the hard back. From the steep angles that I see on your images, I'd suspect that it's mostly low-mids that are going to be hitting the front module, so consider the hard back....

Thanks!
I'll dig out the Neumann KH120 dispersion patterns if I can find them online. It's the lows that I'm worried about far more than the highs right now.
My waterfall below 150hz looks like the Petronas Towers.
We'll see if any of that is coming from the ceiling.
I'm starting to get a bit despondent as the 50hz flab in there is enormous, and the 99hz null goes right down. I'm going to get the cloud up this week, and bass trap the front wall top corner with a superchunk, but I feel like I'm running out of options after that.

Soundman2020 wrote:
Then to REALLY complicate the issue, consider that the lower the frequency, the less sound acts like rays in any case, and the more like a shotgun blast, spreading out as a broadly angled reflection, not a specular reflection, and attenuated by the insulation anyway... and also starting out at a lower intensity to begin with, because it is off-axis....

So yeah, it can get complex if you REALLY want to get into all the nitty gritty! details!

Sorry to dump all this stuff on you suddenly like that! And it's probably not really necessary to go jumping it all of that, unless you are build a really high precision room, but it's food for thought...

- Stuart -

No worries! I'm hear to learn. I've spent the last month trying to envisage the sound in my room and understanding what its doing. Every bit of knowledge helps. I think my room has 0% chance of becoming a high precision room unfortunately. The size and the dimensions are against me.
My ambition is purely to make it a functioning room at the moment (falling sadly short of the ideals of your signature!)

I may be getting somewhere with this.

This is my first design that seems to have mostly worked. Almost all the direct sound goes over the mix position, although the 10deg vertical signal is still being reflected at the sound guy.
The front panel is at 30deg, the 2nd panel is at 12deg
This diagram only shows the plywood, not the rockwool treatment that will go onto it.

(The front corner superchunk bass traps are missing from this diagram - sketch error)

Here's my 2nd design, with the addition of a further panel at 50deg. This design sends everything including 10deg vertical signal over the engineer's head. The 2nd design is going to be testing my engineering / carpentry skills, but I'm up for having a crack at it if it's the right way to go.

If Stu or Greg has a minute, I'd love to know if either of these designs is getting close to the mark.
Am I over complicating things with the 2nd design? I don't know how much reward I get for the extra complexity involved - I don't want to go chasing diminishing returns. On the other hand - if it's sensible, I'll get on the case.

Thanks all, as always!

Owen

Ummm... Are you SURE you are doing your reflections correctly??? It doesn't look like it from those diagrams!

Key point: "Angle of reflection = angle of incidence", using the SURFACE NORMAL as the reference axis. Are you SURE you are creating your surface normals correctly? And that you are reflecting in the correct plane, around that surface normal?

This one, for example, is clearly very wrong:
The reflection on that one should be going nearly parallel to the ceiling! Roughly in line with your uppermost panel...




- Stuart -