John Sayers' Recording Studio Design Forum Archive

... that have them almost to the ceiling and angled down alot where the room is wider than it is deep.

My guess us that the ceiling is not so much of an issue as the floor if it has a lot of absorption, since it won't be creating such deep notches. But if you have a hard surface ceiling, then I wouldn't think it make a lot of difference if the speakers are too close to the ceiling, or too close to the floor.

Logically, the notches in response must be due to the distance between the speaker and the hard surface of the floor. The same would apply to a hard ceiling. Sound waves don't care which way is "up". But if your ceiling is soft and absorbent, then it stands to reason that notch is going to be reduced.

So, I just decided that my ceiling design is up for review (and especially so after watching all of the videos on Ethan's web site). I was originally planning to just put a couple of layers of drywall under the new joists, then add clouds and other treatment as necessary, but now I have decided to build my ceiling "inside out" too, like the walls. So the drywall will go on top of the joists, not underneath, and the space between the rafters will get absorption. It's going to complicate construction painfully, but ... whatever!

It's amazing how much my design keeps on evolving, as I research more and learn more all the time. I am SO glad that I didn't start building yet!

Who was it that said that studio construction is 90% design and 10% construction? I'm starting to believe it.

- Stuart -

I am favoring the inside out construction too. I can always add reflection if I need it through slot resonators. But in the small rooms we are trying to build, control is everything. It seems smart to control then tweak. Hell, I ain't building Blackbird here ya know.

W

Wasn't that Avare's quote?

W

Soundman2020 wrote:
Logically, the notches in response must be due to the distance between the speaker and the hard surface of the floor. The same would apply to a hard ceiling. Sound waves don't care which way is "up". But if your ceiling is soft and absorbent, then it stands to reason that notch is going to be reduced.

I checked with my bud who worked with me and the ceiling was absorbent. I agree with your statement. The speakers were definitely far from the floor thereby minimizing its effects.

W

Sounds like you and I are going to have similar issues with our builds, Wayne!

Do you have a link to your design / build thread? I think I'd look to bookmark it, as I have a feeling I'll be visiting it every now and then!


- Stuart -

Soundman2020 wrote:Reading more on the stuff that Genelec sent me: They did an in-depth survey and analysis of 164 studio control rooms around the world, and came up with very interesting results

You did not reference it or cite it, so I am assuming you are referring to A Survey Study Of In-Situ Stereo And Multi-Channel Monitoring Conditions. Looking at the references I believe you have all the documents.

A point to consider about the notches. There will be notches at the LBIR (my term) frequency because of the distance of the listening position from the floor...

Andre

You did not reference it or cite it,

Oh yeah! Sorry! That's the one. I was so into reading it and absorbing the contents, that I clean forget to mention the title!

Yep, that's it. If you look at the tables with the data on speaker positions, you can extract the percentages I gave above. There's more useful info in there too, on RT60 and frequency response, which I'm taking into account in setting the specs for my design.

- Stuart -

Soundman2020 wrote: There's more useful info in there too, on RT60 and frequency response, which I'm taking into account in setting the specs for my design.

Great! 90%...

Andre

There will be notches at the LBIR (my term) frequency ...

OK, André, I gotta admit it: You got me there! I've been wracking my brains to figure out the "LBIR" acronym, and nothing fits! What on earth does that mean?????

because of the distance of the listening position from the floor...

Yeah, I got that from the Genelec documents and other documents that I picked up along the way. The way I understand it, its a 1/4 wave resonance thing, and both the frequency and "depth" of the notch should go down as you increase the distance from speaker to floor. So at 1.2m you'd expect the first notch to be around 71 Hz, but at 2.2m that would drop to around 39 Hz. (Not that I'm planning on 2.2m! Just an example...)

Is that right, or am I screwed up with my math or my comprehension of what's going on? I'd much rather have a notch at a lower frequency.

- Stuart -

Soundman2020 wrote: OK, André, I gotta admit it: You got me there! I've been wracking my brains to figure out the "LBIR" acronym, and nothing fits! What on earth does that mean?????

Listener Boundary Interference Region. Exactly the same as with speakers. Same principle. Your math in the rest of post is correct.

What I forget to mention is the low frequency absorption effectiveness of absorption at early reflection points. If you look at the absorption of materials at shallower angles, meaning closer to normal incidence, you will see that it really is necessary for the absorbent material to be more like 6 or 8" thick. Yet how often do you read that early reflection point absorption shoould be 4 or even just 2" thick?

Andre

Ahh HA! OK, got it!

And thanks for the tip on the thickness of absorption at my first reflection points. Since I'm planning "inside out" walls, I can easily get 4 inches depth between the studs, and could probably get 6 by "building out" some kind of frame a couple more inches. Would that be good enough?

Also, I've decided to leave the space between the soffits / speakers as dead as possible, as I'm going to need that area to get decent RT60 times, and I've learned that it should improve my stereo image a bit too.

Qiestion: Since that space will be angled to match the soffit angle, I can get about 4 inches depth at the bottom (desktop level) and at least 10 inches at the top (against the ceiling). Should I fill that entire space with rock wool? Or should I just put a 4 inch layer leaning forwards, against the soffits, leaving a triangular wedge of air space behind the insulation? I'm inclined to stuff it totally full of rock wool, with a cloth front on it, to make it as broad band as possible.


- Stuart -

Stuart Wrote:

I'm inclined to stuff it totally full of rock wool, with a cloth front on it, to make it as broad band as possible.

Dude - That's exactly what my guys did. All the detail of the front wall assembly (and everything else) is on my thread.

Regards,

Lou.

Hi Stuart,

Her is the link to my thread; http://www.johnlsayers.com/phpBB2/viewt ... =1&t=11392

I have not been loading in any new designs or anything as of late. I felt the need to peruse the site a lot more and get to know some people. A lot of my questions have been enlightened upon if not answered. I am almost ready to put a solid layout design together. Best use of space has been the issue. Also, how best to account for my ceiling. Your ideas and input would be most welcome, as would anyone one else who wants to contribute.

LBIR, who woulda thunk that could be so important! Thanks Avare!

W

Thought I would share this with you. I was at a holiday party at a friends studio. Their console tech, who hangs out here occasionally, told me about an underlayment made specifically for concrete slabs.

Evidently, it has small protrusions on the bottom resembling "feet". This allows for ventilation and replaces a vapor barrier. In talking with him further, it seems you can glue T&G ply to this and lay hardwood just as you normally would.

Needless to say, I was like wow! As this is certainly a way better solution that framing out a floor, laying in a vapor barrier and using sand or rockwool or whatever. He said it was available at the Home Depot, a US hope products chain.

I will check this out but wanted to let you know as you are building on a slab also. It would really be nice to save 4 or 5 inches in floor to ceiling height!

Don't know any specific product name, but will look into it between now and end of month. Job has me busier than a one arm paper hanger until the holiday.

W

It might be this stuff;
http://www.homedepot.com/webapp/wcs/sto ... 401+503003

Any thoughts on something like this? Is has 5/8" OSB right on it. So, you could nail into it.

W