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PostPosted: Wed Mar 10, 2004 5:31 pm 
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Aaron, I'm almost at a loss as to where to start here - it would make more sense to me if you could explain just what is actually confusing you as far as sequence is concerned - just generally, your soffits will be angled so they can be free-standing once they're attached to the center wall section between them - although with the angles you've shown I'm not sure how you'd mount the speakers themselves without having them in direct contact with the soffits. Maybe if you tilted the entire soffit frame from floor up, in one straight line? Does barefoot's design help here at all?

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=718

For best isolation, the ceiling should hang inside the walls off RC - are you planning to extend the ceiing that's on RC to the inner leaf of your outer walls, or stop it at the splayed walls? The latter will give better isolation between rooms, since there will be no flanking thru the ceilng wallboard beyond where the wallboard stops. If that's what you're planning, then the last thing to put up is the RC and ceiling wallboard - leave 1/4" gap between the splayed walls and the ceiling, push foam backer rod into the crack (recessed by 1/4")after pulling any spacers, then caulk.

I already answered your #2 in Ozzie's wall thread -

3 - One way to do your splayed walls would be to build bass hangers for behind them, use 1/2" wallboard (sheetrock) for all but the top foot, then use 703 for the top foot (cloth covered, batts wrapped in plastic painter's drop cloth or non-biodegradable garbage bags) - this would turn your splay areas into usable bass trapping by having the 703 at the high pressure point, and using the hangers to further disperse/absorb. Either way, wood 2x4 and sheet rock is fine.

4 - yes, just don't allow the flooring to short out between floor and wall- you can put the flooring on, cover with drop cloths, then drywall (gap at bottom, caulked after) - if you're nervous about messing up the flooring, it can go in last - in that case, your hermetic seal would be the one between the subfloor and drywall - then, depending on what type moulding you want at the floor/wall junction, just leave a narrow gap between edge of flooring and drywall and mount your moulding to the wall but spaced a small amount up from the floor. These are your inner splayed walls, so won't be critical to be hermetically sealed, just NOT hard contact between floor and wall.

5 - Personally I would NOT install any carpet in a studio - there are some really nice area rugs that I would prefer - they can be added or removed to change acoustics for a part of the "final tweek" phase, they can be rolled up out of the way when moving equipment around, and they can be sent out for cleaning or replaced with a different one should someone screw one up. Plus, rolling them carefully and removing them from the studio BEFORE cleaning them cuts down on airborne dust.

6 - you're right, this IS personal - it's also a budget decision - you can spend anywhere from $5 a yard for cheap vinyl, up to several hundred for hand laid teak, zebra wood, etc -

7 - Your inner splayed walls should be isolated from the envelope to minimise flanking and compromise of the outer envelope (inner and outer non-splayed walls) - this would be a good place for some of those custom sway brackets to support the tops of the splayed walls.

8 - I need some further clarification on this one - your ceiling on RC, if I remember correctly, is going to be your inner leaf between upstairs? If so, then it needs to be contiguous to the perimeter's inner leaf. This could get tricky...

9 - Neither. All rated wall assemblies assume that the first layer of wallboard is PERPENDICULAR to the RC, then successive layers parallel to the RC. If your ceiling is higher than 8 feet, use 12 foot sheetrock so no splices are necessary. If your particular RC has a wide enough fastening surface (at least 1-1/2" you can carefully set the height of the center row so that your horizontal second layer of wallboard "splits the difference", just like fastening two sheets of plywood to the same stud. If you're uncomfortable with that, put up two pieces at that 4' height. Just be sure to use a marking system (masking tape, for example) that will still be visible after the first course is up, so you know exactly where your fastening surfaces are located.

As to your AC questions, I'm really limited on this - I know some of the theory, but have no practical experience whatever. Your best bet would be to entice Rod Gervais to chime in here. You may have to PM him (he's a member here, and one of my co-moderators over at RO -

Let me know if you need more clarification on any of this... Steve


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PostPosted: Wed Mar 10, 2004 6:20 pm 
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Here's what I'm referring to on the ceiling...


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PostPosted: Wed Mar 10, 2004 7:09 pm 
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As far as the sequence I'm referring to, I'm trying to figure out at what point of the construction needs to go where?

Here's what I'm thinking...

1. Frame outer walls, insulate, RC and hang 2 layers of 5/8" drywall. (This way the entire wall is completely isolated from what's outside the CR.)
2. RC the entire ceiling of the control room area all the way to the outer wall (inside leaf). This means the area behind the splayed walls as well as the ceiling area behind where the front soffit wall is, will be one solid ceiling (technically, with the exception of where I have to manuever around the beam). (complete isolation from upstairs & no holes for leakage).
3. The splayed walls, and front soffit wall area will reside within "The Room", Inside the outer wall, subfloor, and drywalled ceiling.
4. BTW, the ceiling will hang "INSIDE" of the walls.
5. What the heck is "Foam Backer Rod"???????? :?
6. I do plan to angle the front soffit wall. Haven't decided how or what to do here yet. Haven't decide how big a hole I want for future monitors. This is a little baffling. Barefoot mentioned making a big enough soffit to change monitors as I wanted or needed to, but???? :?
7. As far as angling the front soffit wall, I could angle from floor to ceiling. It would be easier to contstruct I would think.
8. I also have a design change as of this last week (although it's been in my mind since I drew it originally and somewhat planned for it). Where the window area is off to the left of the control room, I'm recessing the wall back to allow for a 2" machine to slide in. I posted a question on the other thread in design about 2" machine dimensions. ???
9. Your answer to # 7 didn't make sense. :? Maybe I didn't be specific enough. This relates to the sequence.
10. In reference to Q#8...Also a sequence issue. If the ceiling is done as in drawing 2 I just posted, how do I attach the splayed wall at the ceiling area since the ceiling drywall will be already installed? Construction adhesive?
11. As far as your Answer to #11, that's what I was trying to get at. I was planning on the first layer to be Perpendicular (vertical), but was concerned about the second layer when it runs parallel (horizontal) to the RC. Just trying to figure this stuff out....and do it right. :)

Thanks Steve!!

As always, I appreciate the input. :D :D :D :mrgreen:

Aaron


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PostPosted: Thu Mar 11, 2004 4:01 pm 
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Forgot to mention...small delimma...

My supplier for the Roxul is out of the 3" AFB. They do have lots of 1 1/2".

Is there or will there be a major acoustical issue or measureable difference by using 2 pieces of 1 1/2" to aquire the 3" needed in the walls???

Thanks,

Aaron


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PostPosted: Fri Mar 26, 2004 5:02 am 
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Aaron, now that we're (sorta) back up, please let me know what you still need answered - I'll try to catch up by tomorrow nite... Steve


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PostPosted: Sat Mar 27, 2004 12:41 pm 
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Good to see the site back up.

Ok, here we go...Some of them I've already gotten answers to and I'll post.

The last post on the insulation, I contacted Roxul to ask about the frequency/acoustical properties of using 2 pieces of 1 1/2" vs. 3". They said it will have the same properties as having the 3".

I still have some curiosities of the ceiling, but I think for ease of installation, as well as isolation, the entire ceiling in the control room will be put up before installing the inner splayed walls.

Now the question comes as to how should I connect the framing of the inner splayed and front soffit wall to the ceiling? Use construction adhesive? The bottom won't be a problem, as it will attach to the floor.

Anyone know of a good/cheap place to buy Pergo flooring?

I also was having a difficult time trying to figure out how to enclose the steel beam, but I think I've got that resolved for now. I'll post a drawing when I get around to it.

I've also learned that RC1 comes in different gauges. For the ceiling, if you're putting up 2 layers of 5/8" drywall, be sure to use 20 guage. 25 is too light to support the weight. I was told this from my supplier. And I sure don't want a 1000 lbs of drywall falling down on me or the gear.

That's it for the moment.

Thanks,

Aaron


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PostPosted: Tue Mar 30, 2004 2:58 pm 
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Had a few minutes to draw this up. Here's how I intend to enclose the steel beam that runs through the control room...


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PostPosted: Tue Mar 30, 2004 9:35 pm 
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Should work fine, Aaron - I'm printing out your previous Q list and will try to find time tonight (last graveyard shift) to catch up... Steve


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PostPosted: Sat Apr 03, 2004 4:16 pm 
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OK, lets see what we can cover here –

CR ceiling – I agree you should extend the ceiling past the splayed walls – it should go to your actual inner envelope walls, to complete the envelope for sound control (not acoustics)

Attaching the soffit/front walls to ceiling – I'm not sure how to handle this without compromising your envelope. I think maybe the best way would be to mark where your RC's for the ceiling are located, so you could run some long screws thru the top plates and into the RC where the wall and the RC intersect. A 6" wall only needs a little over ¼" of gap at the top in order to be able to tip it into place without hanging up on the ceiling, so you could tip up, put ¼ ply spacer along the top, screw into the intersecting RC's (thru the ceiling layers) and caulk on both sides of the top plates. I know this would break the inner leaf, but the combination of the caulk and the insulation above the ceiling wallboard would make it tight enough not to matter. The bulk of your splays' support will be the fact that they meet each other at angles, and will be attached to each other from floor to ceiling.

Foam backer rod is usually found with weather stripping products – it is just closed cell foam in the shape of a dowel. Comes in different diameters, and is used to cut down on the amount of caulk required for larger cracks. It keeps the caulk from having to bridge such a large area, so the caulk doesn't sag enough to fail.

" I do plan to angle the front soffit wall. Haven't decided how or what to do here yet. Haven't decide how big a hole I want for future monitors. This is a little baffling. Barefoot mentioned making a big enough soffit to change monitors as I wanted or needed to, but????" –

The main thing with soffits is that they have a very narrow gap around the speaker box at the baffle, and that the speakers don't have hard contact with the fronts. By building the actual boxes larger, you can build different "inserts" for the actual front baffle to accomodate different sized speakers. If you do free-standing stands that sit behind the soffits (see Barefoot's pix), the portion that the speakers sits on could be made adjustable to fit different sized boxes.

Genelec has some useful info on soffit mounting on their site –

http://www.genelec.com/support/soffit.php


Sorry this took so long, when we get usable weather here there are always more things to do than there is time/energy to do them... Steve


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PostPosted: Sat Apr 03, 2004 4:55 pm 
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Being from the NW myself, I completely understand the "make use of..." statement.

I also posted a question on the acoustics forum about hangers, etc. Barefoot added some comments. Perhaps you may know of some links or diagrams on some different construction and mounting techniques.

In looking at barefoot's diagram of soffit mounting, this looks kind of like a stand or really it looked more like a 3rd framed wall inside the soffit wall. Are there some additional diagrams on a thread somewhere I can get a better idea of what you're mentioning here?

I finally got the AC guy out to look around. Hadn't heard back from him yet on the quote :?

Thanks for all your help Steve.


Aaron


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PostPosted: Tue Apr 06, 2004 6:41 am 
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Here is a basic way to do hangers, I'd vary thickness within a trap area for wider range.

Soffits, stands - what is it you're not clear on, maybe I can help...

And you're welcome, your thread has undoubtedly helped LOTS of people, judging from the view count... Steve


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PostPosted: Wed Apr 07, 2004 2:27 am 
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Hey Steve,

OK, I'm posting a drawing now of how do I or how should hang the acoustic hanger


BTW, I agree. I realize this topic originally started out as the "Floating Floor" thread, but it has also begun to really take on the shape of a complete section, covering all aspects of the entire construction process. At some point, I may go back to the first page and edit a post (if possible) and create links that will jump through the entire thread in relation to the different topics that we have covered here. Especially since we are at the end of page 13 now, just about to go to page 14 in the next post or two. What do you think?

Aaron


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Last edited by Aaronw on Wed Apr 07, 2004 4:07 am, edited 1 time in total.

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PostPosted: Wed Apr 07, 2004 4:06 am 
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Also, here's another drawing in reference to what I was asking about the inner frame of the soffit stand. Also, looking at the Barefoots design, it doesn't show a completely sealed box. Is the opening of the speaker soffit just open all around? I was originally under the impression that you were to build a "Box" that the speaker was to fit into. But looking at barefoots design, that's not the case.

Now, another question in reference to the front soffit design. Should the entire front wall/soffit wall be solid from floor to ceiling? Or, should there be an air gap, port, or 703 scenario to be used either on top or bottom of the soffit wall?

Looking at John's drawing on SAE: http://www.saecollege.de/reference_material/index.html (under construction/speakers...3rd drawing down), and this almost contradicts what Barefoot has drawn up, or maybe there just isn't as much detail on John's drawing or vise versa. But it does show utilizing the space for bass trapping.

So I'm a little bit at a loss in direction here...

Thanks,

Aaron


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PostPosted: Thu Apr 08, 2004 8:58 am 
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OK, you're getting into places that might be better handled by Barefoot or John - I'll give you my opinions, and try to "rate" each one as to how sure I am and why, but if either John or Thomas argues a point, odds are they're right... Now that we have some "ground rules", and since this also encompasses Construction, here goes -

First, NEVER hang anything with any degree of mass from a resiliently mounted ceiling - its purpose is to isolate, and as such it can only do that if it is properly "sprung" - in other words, a spring (the RC in this case) is ONLY a spring if it is NOT near the ends of its travel. We need to choose things like spacing of RC, gauge (thickness) of the RC, and amount of weight of drywall hung on the RC, in order to optimise this spring function. Hanging heavy MDF from such a ceiling will only screw up those parameters. It would ALSO cause any vibrations induced into the hanger to travel through the suspension device (chain, wire, whatever) and weaken the isolation factor at that point.

That being said, I would tend to build a separate free-standing frame (it could be anchored to the floor, but NOT any sprung wall panels) kind of like a large drum gong stand, and hang the hangers from that using either multi-strand vinyl-coated cable and cable clamps, or chain. You might build something like a miniature "gazebo" frame, with 4 posts and a pair of "ceiling joists" left to right, then put 2x4's spaced at right angles to the long joists, lined up to support two points on each hanger. If you offset each hanger in a herringbone pattern within their cavity, the framing for this "hanger hanger" could get kind of tricky.

If you can't envision this from my description, I'll try to do a sketch - it may take a while (what's new :? )

"looking at the Barefoots design, it doesn't show a completely sealed box." - This one, I'm about 98% sure of -
Using normal (not "naked" drivers) speakers in their own box, if those speakers are NOT soffit, or flush, mounted here's what happens -

for higher than about 300 hZ, sound tends to be directional but it will diffract at the edge of the baffle (the front plane of the speaker box) and "wrap around" somewhat. This can contribute to early reflection problems depending on positioning of the speakers relative to things like consoles, meter bridges and close walls. Some nearfields have their front baffles radiused (rounded edges) to minimise this. Also, setting this type of speaker right on the bridge often worsens early reflections off the console due to the fairly steep angle between speaker and console surface, which often ends up "aiming" these early reflections right at the ears of the mix person. Placing nearfields on stands behind the bridge changes this angle to a shallower one, and may "re-aim" these reflections UNDER your ears and to the rear wall. (a good thing)

For lower than around 300 hZ, sound becomes more omnidirectional so for a free-standing speaker, it will now radiate "full circle", otherwise known as "4 pi space" - Since about half of the lower frequencies are "getting away" (not coming directly to the listener), manufacturers of free-standing speakers build in a 6 dB boost in low frequencies to compensate for this problem. Some better nearfields have a "space selector" switch that lets you decide on the response based on positioning of the speaker relative to boundaries, others don't.

Properly mounting speakers (in their own boxes) in a properly sized baffle extension, forces the lows to radiate in only the forward half of the space, boosting the LF response by about 6 dB and making that internal compensating network (used for free-standing situations) un-necessary.

In order to work well, a baffle extension (the flat area around a soffited speaker) needs to be massive so it doesn't add coloration to the sound (sympathetic vibrations) and it needs to be large enough to force the lowest frequency the speaker reproduces to only radiate FORWARD.

Barefoot put forth a comment on this size requirement some time back, and I've never been able to find it again - something to the effect of a minimum distance (in all directions, but NOT centered)from the woofer of 4 or 5 woofer diameters for a minimum baffle size. As I interpreted that statement, it would mean a baffle that extends FLAT in the EXACT same plane as the front of the speaker box for at least 4 times the woofer diameter in all 4 directions. IOW, if you had speakers with 8" woofers, the baffle should be flat for at least 32" in a radius from the woofer, but assymetrical (more flat space on successive sides, so that any artifacts from the edge of the extended baffle do NOT reinforce each other at the same frequency)

Having splayed walls encroach on this minimum baffle size has the effect of creating a "horn", which tends to directionalize the sound field from the speaker and shrink the "sweet spot" -

Increasing the height (and subsequent downward angle) of soffited speakers tends to increase the likelihood of early reflection problems from bridge and console, so should be kept to a minimum. If the situation allows, you're better off NOT tilting the monitors at all, and putting them with the HF drivers at ear height. Practical considerations (windows, nearfields, etc) tend to force mains to be mounted higher and canted. Just be aware of the problems this can bring up.

Because of the HF diffraction problem, the area where the speaker box baffle ends and the extended (soffit) baffle begins needs to be controlled. First, the speaker needs to be EXACTLY flush with the soffit - not ahead or behind. Second, the gap between the baffle extension and the speaker baffle needs to be kept to a minimum (diffraction) - Barefoot has recommended less than 3/16" if memory serves. The speaker box should NOT touch the baffle extension to avoid exciting the baffle extension un-necessarily.

Loose-fill insulation placed in the gap around the speaker finishes controlling the edge-diffraction effects - if the speaker is in a larger box, the area around the speaker box should be filled with insulation to keep cavity resonances from causing problems.

However, this "soffit box" isn't necessary to the operation of flush mounting - if you could somehow "levitate" the soffit wall so it touches NOTHING, and is hermetically sealed to the speaker box (flush) without touching the speaker box, that would meet all the necessary criteria. Unfortunately, this isn't Camelot :cry:

So, if you were to build massive baffle extensions (soffits, or flush mounts, same thing for this discussion) and then mount your speakers on isolated stands in such a way that they maintained front surfaces in one plane, with the speaker boxes having a small enough gap between them and the soffit face, that woould work.

Now, if you plan on utilizing John's integral bass trapping, things change.

There is a phenomenon of some ported speakers, when pushed near their limits, to reach a high enough air velocity through their ports to cause the air movement to become audible - the term I've seen is "port chuff" - called that because that's the sound you hear when it's happening. It comes on fairly rapidly, because the noise generated by moving air is proportional to somewhere between the 4th and 5th POWER of velocity, so a slight increase in air velocity through the ports would cause a large change in perceived sound level.

Because of possibility of the "chuff" phenomenon extending to other ported enclosures, and because of the non-hermetic seal around speaker boxes (insulation), building a bass trap into a speaker soffit would probably need to be done differently than just a soffit WITHOUT a bass trap incorporated. In this case, a sealed outer box (sealed to the soffit) might be necessary to keep the "port" around the speaker box from exhibiting this "port chuff" problem.

OTOH, if a soffit were to have integral bass trapping with HANGERS incorporated, the hangers might lessen air currents enough to negate the need for a sealed box around the speaker.

Another problem with a sealed box around the speaker is finding a good way to isolate vibration from speaker to the sealed box - remember we're trying to keep the speaker from vibrating the baffle extension, so that part needs to stay decoupled.

As to porting an integral soffit/bass trap, keep in mind that maximum sound pressure occurs at boundaries/corners, so one way to do this would be to leave an opening to the plenum at floor or ceiling level, use hangers inside, and then cover the port with 703 or rockwool in 3 to 4" - since that location would NOT be a reflection problem, you could go with higher than normal density (say 6-10 PCF instead of 3 PCF) - That would lower the effective cutoff frequency of the trap somewhat.

As to the drawing on the SAE site, I think it's mostly the difference in detail level. However, from what Barefoot says about baffle sizes, you would want to continue the plane of the speaker front further away from the woofer before changing the angle of that plane, which would shrink the available space for a trap below the speaker. This could still work if you have enough depth behind the soffit to continue its angle clear to the floor (or nearly) and still get enough volume of space behind the soffit wall for a good bass trap.

Also, the SAE drawing shows no decoupling between the speaker and the soffit box, which would be necessary.

John, Thomas, any thoughts? (assuming you get a free WEEK to read this...) Steve


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PostPosted: Thu Apr 08, 2004 10:30 am 
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I think I just had an orgasm. :shock:


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