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PostPosted: Mon Dec 25, 2017 6:56 am 
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Location: St. Albert, Alberta, Canada
For better viewing and communication, I'd like to have the couch in my control room on a raised floor. A few thoughts I had were:

- Build it to prevent it from becoming a resonant chamber.
- Ideally I'd like to have HVAC run through it, but then it will for sure resonate and I'd have to put my HVAC silencer down stream further so that's probably out of the question.
-The floor underneath is radiant heated concrete and I'd like a nice warm floor for the people sitting there as it gets really cold where I live in the winter. Having HVAC in it would maybe allow more heat to go through the material into their feet, but again, that's probably not possible right?

After cruising the forums, I couldn't find any good threads on this particular area of design. Any help would be appreciated.

Thanks!

Greg

*edit - I'm starting to sketch up my CR and ISO room layout so it's far from done/correct, but I just threw a quick couch platform on there to show what I'm talking about.


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PostPosted: Mon Dec 25, 2017 9:19 am 
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Location: Santiago, Chile
Quote:
I'd like to have the couch in my control room on a raised floor. A few thoughts I had were:

- Build it to prevent it from becoming a resonant chamber.
Right! I've done a few rooms like that, with a riser at the rear. Here's one of them: viewtopic.php?f=2&t=20471 If you go to the actual website, there's more photos of the actual build sequence, where you can see the riser under construction, and also complete. Basically, the entire rear half of the room is raised by several inches, and yes, it was a challenge to design that so that it would not cause unwanted resonances. In fact, the entire riser is tuned to act mostly as a bass trap. Your concern is very real, and requires careful design.

Quote:
- Ideally I'd like to have HVAC run through it,
I would try to avoid that. I usually try to keep all of the HVAC stuff up high, at the wall tops or in the ceiling, for several reasons. Running HVAC under your floor would be possible, but then you would not be able to use the riser space for treatment. And if you plan to have a silencer box inside the riser, the space will have to be very high: probably two steps up, instead of one, to be able to fit in a usable silencer.

But if you planned to just run the HVAC air through the underfloor area to warm it, that would not be a good idea, and actually wouldn't work very well. See below....

Quote:
Having HVAC in it would maybe allow more heat to go through the material into their feet, but again, that's probably not possible right?
Not really, and not really: "Not really" that it would warm their feet, and "Not really" that it would be possible. It won't warm their feet for a simple reason: thermal mass. The deck of your riser will need to be built up from several layers of dense materials, then covered with an acoustic underlay, then the final finish floor. It would take quite a while to heat that lot up, especially considering that the acoustic underlay is also very effective as thermal insulation... If you just ran warm air under the floor, it would be a looooonnnnngggggg time before the low level heat managed to become noticeable on top.

A better plan would be to have a some other type of heating at floor level, perhaps something that gently blows warm air across the floor surface: some type of fan heater, or baseboard heater with a fan in it, maybe?

Quote:
After cruising the forums, I couldn't find any good threads on this particular area of design. Any help would be appreciated.
I can't really share the details of the sofa riser floors that I have designed, since all of them have been done for paying customers, for their specific studios. But the general principle that I use is to NOT float it (that would be a major mistake), avoid having all the joist bays the same size (volume), put plenty of damping in the bays, and bore large holes in the joists to acoustically couple the bays at certain frequencies, so you can get your bass-trap effect.

Quote:
I'm starting to sketch up my CR and ISO room layout so it's far from done/correct,
Are you planning on building an NER design? That0s what it looks like, with that shaped room... I'm not a big fan of those, since they waste an awful lot of space due to all the splayed walls, and building them practically requires a master carpenter, to get all this finicky angles right! It's complicated to do that. I'm not sure if you've ever tried to rip a stud at an angle of 21.3° and end up with the broad side exactly 2-9/16" wide (for example), but if you can't do that with your eyes closed and one hand tied behind your back, then it's probably best not to even try! :) (I know I can't do it!)

I'd suggest modifying your design for an RFZ style room: there are still angled walls, yes, but they waste a lot less space, there's fewer of them (only four, instead of twelve!), and the angles are a lot easier to do. Commonly, just 30° and 10°, or something simple like that. It's still not a walk in the park to build, but it's MUCH easier. If you look around the forum, you'll se taht many forum members have built their rooms like that, successfully. I'm not aware of one single forum member who has built a NER style room by themselves, such as you show.

Quote:
I just threw a quick couch platform on there to show what I'm talking about.
Correct, but you also seem to have a QRD or PRD diffuser on the rear wall, and from the looks of it, it is tuned pretty low. I'm not sure if you are aware, but the guys that very literally "wrote the book" on these types of diffusers, Cox and D'Antonio (https://www.amazon.com/Acoustic-Absorbe ... 0415471745), do not recommend that setup at all. They did all the research and came up with the mathematical models that describe how this type of diffuser works, and they recommend that there should be a distance of at least 10 feet (aprox. 3m), between the face of the diffuser and the ears of anybody in the room that needs to do critical listening. They also say that there should be 3 full wavelengths of the longest wave for the tuning (the low cutoff frequency for the device), and later they revised that to 7 full wavelength. So depending on how yours is tuned, you need a MINIMUM of ten feet between the diffuser and the sofa, and maybe MORE than ten feet if the "7 waves" rule for the low cutoff is greater than 10 feet.

The reason is simple: those devices cause "lobing" in teh diffuse sound field, close to the device. You have to be far away in order to allow space for the lobing to smooth over and become imperceptible. The lobing occurs in frequency, phase, timing, and intensity, and looks something like this:

Attachment:
QRD-Diffusion-lobing--pattern-graph-SML-ENH.PNG


So, even though you do often see photos of supposedly high end studios with QRD's on the rear wall, just inches away from the couch, it's a mistake if you plan to have people doing critical listening there. If the couch is just for WAGs to crash on, or have a chat while the engineer and producer work their magic at the console, then that's fine. But if you'll have people back there that are involved in making decisions about the mix, then it's a mistake.

- Stuart -


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