NEW Basement Studio Design in New York. Looking for advice

Hello All - I am have been poking around this site for years and have finally decided to become a member and seek advice on my upcoming new studio build. Basic Info: - Basement has 7'-0" ceilings. - Dimensions of the overall basement are 28'-10" by 23'-9" with a (3) 2x8 beams (ORANGE) sitting on vertical poles/columns (RED) down the center (lengthwise).- - There are also 2 additional poles/columns off-center. - I have (2) 18" subs in boxes that are 29" W x 28"D x 25" H - Main monitors are Urie 813. boxes are 36"H x 31"W x 22" D - Desk is an Argosy and is shown pretty close to scale in the drawing. (I am trying to swap out the two desk mounted racks with with ones that are about 6" lower and no flat top) The room is going to be used for mixing hip hop and reggae and pop mostly, and occasional rock bands. So accurate low end monitoring is a must! Isolation to the house above is important, My sister going to be living upstairs and want to be able to play fairly loud late at night while she is sleeping. WALLS: The outer leaf/soundproof wall I colored the framing BROWN. anything not colored brown is part of the soffit/internal room construction. I plan on building the walls with 2 layers of gypsum on the INSIDE of the framing (2-leaf system with this BROWN wall being 1 leaf) ). CEILING: The ceiling (which is NOT shown on the drawing) will be built the same way. I plan on attaching the NEW ceiling joists to the top of the NEW walls - they will have to run parallel to the existing floor joists to maximize height and perpendicular to the ORANGE beam shown. - I don't plan on using any resilient channel from the exiting joist for the new ceiling. For the second "leaf" I plan on "beefing" up the existing ceiling with the method I found on here; glueing 2 layers of gypsum, and furring strips to secure to the bottom of the existing sub-floor and beams, making the 2-leaf system between studio and upstairs. DrumRoom and VocalBooth will both be built the same way as the control room walls - creating the 2-leafs between them. There will also be a small bathroom crammed in under the stairs an whatever is left near the goal booth will be the "hang out" room. Utilities will go in the other remaining space. Finished Control Room Dimensions: H=6'10" x W=17'-6" x D=10'-11" My main concerns are this: 1) FLANKING/COUPLING: In order to maximize space, I had to push back the speakers - now they are very close to the existing poles/columns. My concern is how much flanking/coupling will occur between the subwoofers and the existing RED columns?? Also, is there any structural issues with putting those massive 18" air-moving subs right in between the poles? I mean, if I WANTED to demolish the whole house with speakers - thats where I'd put them lol. Also, the Urie 813 mains are right next to the poles. Although the poles are actually located WITHIN the control room this way - I should be able to have my wall/leaf still be solid around them, and apply some soft caulk where the gypsum is cut out around the poles. So the main concern is really flanking to the existing Columns/Poles. not DIRECTLY - but within a few inches of air. Also, indirectly through the concrete basement floor, within a few inches. 2) SOFFIT SIZE: My soffits are starting to getting sort of thin with this design as well - I dont know if this is too much of a concern. The doorway to enter the studio is right where the Sketchup Man is standing and there is basically only a 5" wall right up against the speaker which is its "soffit" 3) TRUE ISOLATION TO UPSTAIRS: Now when it comes to "beefing up" the ceiling, without question I am going to do the areas above the Control Room and LiveRoom. The area designated as 'hang-out" room, I'm not really concerned about sound leaking into there. However, it would seem that I need to "beef up" the ENTIRE existing ceiling in order to really have a true 2-leaf system - otherwise sound would find a way through a non "beefed-up" ceiling, or even through a single leaf off there is any small hole in the existing floor anywhere. ANy responses or other suggestion/tips would be greatly appreciated!!!!!

ROOMS LABELED AND LATEST SKETCHUP FILE!

JPEGS HERE

Hi " richroyc", and welcome! :)

Main monitors are Urie 813.

I think you mean "Urei" not "Urie"? But those things are monsters! I wouldn't use them in such a small room. Don't you have something more suitable?

My sister going to be living upstairs and want to be able to play fairly loud late at night while she is sleeping.

You need to put some numbers to that. You can't plug in "fairly loud" and "sleeping sister" to the equations that predict isolation! You need actual decibel estimates of "How loud will you be" and "How quite does that have to be outside". Subtract the small one form the big one, and the answer is "How much isolation you need".

I plan on "beefing" up the existing ceiling with the method I found on here; glueing 2 layers of gypsum, and furring strips to secure to the bottom of the existing sub-floor and beams,

I think you mis-understood that! The layers of drywall should NOT be glued to each other, nor to the existing sub-floor above you. Rather, they should be held in place by cleats nailed sideways into the joists, and carefully sealed all around the edges with acoustic caulk. Gluing alone is not only dangerous and not even allowed by building code, but also a bad idea acoustically.

DrumRoom and VocalBooth will both be built the same way as the control room walls

Drum Room? As in live acoustic drums? And "Sleeping Sister" is right up stairs, just above that subfloor? OK, so you need major isolation here. Drums are loud, easily hitting 110 dBC. "Sleeping sister" is quite, and probably needs less than 40 dBC to remain "sleeping", rather than "yelling". That's a MAJOR undertaking. That's about 70 dB isoaltion!!! :shock: pretty much the limit you can expect from a very carefully designed, very carefully built isolation system. 70 dB is roughly the flanking limit for a typical house, unless you take same major (as in "expensive and complicated") steps. All of a sudden, this is looking to be a lot bigger project than you were imagining.

Finished Control Room Dimensions: H=6'10" x W=17'-6" x D=10'-11"

That's a REALLY low ceiling, and a very small space, especially considering the gigantic monitors you want to use. I'd really suggest that you might want to rethink that. The room ratio is also not so good, at 1 : 1.59 : 2.56. That's outside the Bolt area. In addition, your diagram shows that you have the room set up "sideways", which would be a major mistake for such large speakers. They should be facing down the longest axis of the room, not across the shortest one. With only 11 feet total distance between front wall and back wall, your mix position would have to be about 4'6" from the front wall, and thus only 5'6" from the rear wall: that puts the reflections from the rear wall at about 11ms, which is well within the Haas time. Not a happy picture, if you hope to get a clear sound-stage with excellent stereo imaging. And with an Argosy desk, I don't see you being able to get so close to the front to start with! From your diagram, it looks like your head is either right at the 50% mark (worst possible location in the room, for modal response), or actually even closer to the rear wall than the front wall! :shock: Bad idea: lots of psycho-acoustic smearing or your directional clues going on there. You also seem to have your speakers mounted up high and tilted down, which only makes matters worse, and increases first order reflections of the console/desk. I would make the room much bigger, and turn it 90°, so the speakers are firing down the long way. And put the door some place where it wont be messing with your acoustics, too.

My concern is how much flanking/coupling will occur between the subwoofers and the existing RED columns??

Probably not a lot, depending on what those columns are made of, but still plenty to blow away your hopes of 70 dB isolation. You'd likely have to soffit around those, to keep them outside of the wall cavity. I had to do that once for a place in Canada. It's a pain, but it worked OK.

Also, is there any structural issues with putting those massive 18" air-moving subs right in between the poles?

Unlikely. There's actually not a lot of energy in a sound wave. It's unlikely that you'd be putting out much more than about one watt per square meter of actual acoustic energy: not even enough to warm your coffee. It SOUNDS plenty loud, yeah, and you might be ´pumping several hundred watts into those beasts, but in real energy terms not much is coming out. Speakers are very, very inefficient at turning electrical power into sound power. You need very, very large surface area and major amounts of power before you can start literally "lifting the roof".

Although the poles are actually located WITHIN the control room this way

Ummm... nope! Sorry. That can't happen. If they are inside your control room, then you have no isolation. You are basically limited to way, way less than what you need. The poles have to be outside of the control room: either in the MSM cavity, or better still, isolated from that cavity by soffiting around them.

My soffits are starting to getting sort of thin with this design as well - I dont know if this is too much of a concern.

Yep, it is. Soffits have to be massively rigid, and have very thick, heavy, massive front baffles. The larger and more powerful the speaker is, then larger, thicker and more rigid the soffit needs to be.

The doorway to enter the studio is right where the Sketchup Man is standing and there is basically only a 5" wall right up against the speaker which is its "soffit"

Your speakers are nearly 3 feet wide (31"). Adding 5" isn't notably useful. Ideally a soffit should add substantial area around the speaker, hopefully at least twice as wide as the speaker. Take a look at how 813's are normally soffit-mounted: there's stacks of real estate around them.

it would seem that I need to "beef up" the ENTIRE existing ceiling in order to really have a true 2-leaf system - otherwise sound would find a way through a non "beefed-up" ceiling, or even through a single leaf off there is any small hole in the existing floor anywhere.

Correct. And since you need huge amounts of isolation ("Live drums" - "Sleeping sister"), you will need huge amounts of mass to beef up that floor, plus a very large air gap... which basically means that you'd never be able to record drums in there anyway. There needs to be a large distance between your overhead mics and the ceiling above to avoid reflections, phasing, comb filtering, and all the other nasties associated with nearby boundaries. with a 7 foot ceiling, you already can't do that, but by the time you have enough air gap and mass to get the isolation you need, your ceiling will be down way lower than 7'. More like 6'. There simply is no way to get good overhead mic'ing like that. If you need to track drums, then I'd look for another place to do that. I just don't see it happening with such a low ceiling, and a need for major big-time isolation. How about building a stand-alone drum booth out in the back yard? Or maybe taking out the basement floor, digging down another couple of feet, then pouring a new slab down there?

JPEGS HERE

I only see one leaf in those. Where's the other leaf? Sorry I don't have good news for you here: I'm sure you didn't want to hear all of that! But that's what you came here for, really: to get an honest opinion on your prospects for achieving what you want. Unfortunately, the prospects aren't so good. That's not to say that you can't use the space you have: you sure can! If its the only space you have, then that certainly is better than having no space at all. But if that's the case, then you have to lower your sights, and aim for a more modest outcome. Major isolation such as tracking live hip-hop and pop drums right under "sleeping sister" is just not going to happen, realistically. You can get good isolation, but unless your sister is very tolerant, or stone deaf, she's not going to be happy about the results. And neither are your customers going to be amazed by the clarity of your drum tracking: with OH mics just inches from the ceiling, that isn't going to happen either. Ditto for the control room: 30 year old monster vintage speakers that are way too large for the room, and beautiful desk that is way too large for the room, a low ceiling, short axis aiming, and untenable mix position, do not bode well. Yeah, you likely can work to a certain extent in such an environment, but it won't be anywhere close to world-class, and your mixes are not going to translate well. Sorry to be the bearer of bad tidings, but that's the reality of your situation, the way I see it. - Stuart -

Stuart - thank you so much for the in-depth reply! I was hoping you would chime in! Lol yes I mean Urei, they are not knock-offs like my Rolecks watch lol. I had a feeling I would have to rotate the room 90 degrees (the long way). Here's why I originally oriented the room this way - I work at another basement studio that has 18" subs, Urei 813's and same height ceilings, and the room is also oriented the wide way. It's the reggae artists Shaggy's home studio. Most of his his hit songs were mixed in that room, and the room sounds phenomenal. And I really like the wide orientation of the room. The oversized speakers just work in that room - For this reason I am somewhat stubborn about keeping the big 813's (and the 18" subs) as part of the design (although I'm sure you are correct; they are oversized for the room). I'll quote the producer who works over at that other studio "there's always a volume knob" lol. I attached a photo of that studio - this is before they put the Urei's in. Its the pic with the Control 24 in the board. Redesign: However, I do understand the logic in orienting the room the long way - So I'll digress on a wide room and sketch up an new design with the room rotated 90 degrees and I'll try to eliminate most of these issues, I'll keep the columns OUTSIDE the control room walls. Low Ceilings: Yes I know my ceilings are VERY low - and financially I don't think digging into the foundation will be feasible. I am well aware of the drum overhead issues as I deal with them now in a drum room that has 6'2" ceilings!!! I always tell my clients to track drums in another studio and bring the tracks back but I DO like having the option close by, and I also like to have a place to jam with friends. Drum tracking is last on my list of things I need this studio to be able to do, but mixing is the top of the list. Speaker tilt: I did originally have the speakers tilted down about 5 degrees but after realizing how low they are, it doesn't make sense, they will stay straight. (along vertical axis) A few things to clarify regarding isolation to upstairs; 1) Tracking drums will have to occur while my sister is not sleeping. This is not an issue drums tracking is less than 1% of the work I do. 2) Using the 18" Subs and Urei's may have to be limited to when my sister is not sleeping (I have NS-10's for near fields and late night stuff) A few questions: 1) Ceiling beef-up" for beefing up the ceiling, is there anything that goes in between the existing subfloor and the gypsum? just firmly held in place by the cleats and caulked around edges? no air space correct? the air space will be below the gyspum layers (in the depth of the existing joists) and above the new ceiling. 2) Room Ratio - I guess I did something wrong but I thought I was at the 1 x 1:62 x 2.62 golden ratio? 3) Soffit construction: I still have a lot of research to do on here before I go posting tons of questions. But my main confusion is this: Do I decouple the speakers from the front soffit wall? Is this achieved by building a very heavy (possibly concrete) speaker stands, and then building the soffit, close but not touching the speaker or stand? My confusion comes from seeing many pictures of Urei 813 mounted in soffits, but there is space underneath them. Obviously there is no stand. (see photo and this link - http://www.malvicinodg.com/wp-content/u ... tudios.jpg 4) Air Gap and MSM above ceiling: I was planning of installing the new ceiling as high as possible to the bottom of the existing joists. I achieved this in my current studio drum room by running the ceiling support beams parallel to the existing floor joists, but up in between them. (See sketch) this should give me about 7" air gap. The new ceiling is 1/2" below the joist. What kind of isolation can I expect with this? (note: I'd be using 2 layers of 5/8" gypsum for both "beef-up" and new ceiling. Do I need to have less "beef-up" in order to match the mass of the new ceiling to the existing floor? for example: 1 layer of gypsum + subfloor = mass of new ceiling? This design was incomplete and really only showed the control room with no indication of where the other walls would be. I'll make sure I give a clearer picture on the next sketch up file. I have more questions regarding why the existing column/Poles cant be inside the control room but I wont get into that now since with the new design I will try to keep the poles out of the control room. No news is bad news as long as I get it BEFORE I build anything lol. You should see my current setup - talk about face-palm (I have the Urei's free standing in a smaller room lol.) Thanks again Stuart you advice is priceless!! I also attached a pic of my current set-up. I really wanted to get away from those Urei's being so close to eaachother. If you open the Photos in a new tab they will not be upside down - Mike

See attached jpeg's of the new layout. I oriented the room lengthwise. There were a few other things I added, I show the doors and a bathroom. There are also existing waste lines that I have to avoid there will be a new waste line for the new bathroom. They are shown in orange. They lead to a waste trap that the plumber told me needs to be accessible - so I built the wall around that and will put in an access door. Questions regarding Room Dimensions: 1) Bolt Area - I don't know where I got those other ratios from (its the internet so it must be right?) but I see now how to use the Bolt area chart. My question is; are all areas withing the chart good? In other words - if I am closer to the center of the Bolt Area, is that better than being right near the edge (but still within) the acceptable area? I am just trying to maximize my room size. 2) Low Freq Mode Chart (Trevor Cox 2004) I am also trying to be within one of the dark spots on this chart. My question here is also how important is it to be to one of hose dark areas (areas with the least modal imbalances). I know I will be doing a fair amount of bass trapping so I am just wondering how important this chart is. The room size also become an issue if I follow it too closely. 3) Sacrifice/Trade-Off: Its seems impossible to achieve a Bolt Ratio room AND a 38% listening position. If I make the room longer, I can be sitting towards the front 38%, but then my room is outside Bolt Area. If I make the room withing Bolt area - I am sitting at around 50% :( - Which is more important? 4) If Soffit front wall is massive - where is room dimension measured from? Do I take my Bolt Area measurement from the front soffit wall? Or from the "shell" outer control room wall, behind the speakers? There is about a 3'-2" difference. 5) any suggestions with walls, angles, room orientation etc… i will need a camera feed to the vocal booth with this setup - I have room to mount a nice flat screen in between the mains since there is not window.

Hello All! Just an overall update - I've started demolition in the basement (there was an old bar and some areas had 3/8" gypsum on the underside of the floor joists - typical basement ceiling finish stuff) not too much bad stuff up there as far as holes/bad subfloor, pipes - or even electrical wires) There are SOME plumbing pipes which I was already aware of that need re-routed and I have already met a plumber there for an estimate. Structural engineer also gave me the go-ahead to add 2 layers of 5/8" for "beef-up" wherever it needs. I am adding a dormer on to this house which will allow me to remove the washer and dryer from the basement, and put it upstairs - clearing up precious studio space. So I'm pretty busy planning and hiring people for that as well. I am having my 100 AMP existing electrical box (which is basically fully packed with breakers) upgraded to a 200 AMP service with plenty of spare breaker spots for new studio stuff. So now onto the questions: So there are some areas where my outer leaf wall will be angled. My understanding is that this outer leaf wall should extend all the way up to the existing subfloor (with beef up added) - which is also part of the outer leaf - creating an airtight seal between wall and ceiling. I've attached a photo of my latest sketch up design. The new inner leaf walls and ceiling will not be touching the existing floor joists or subfloor in anyway. This is how I plan on supporting the new ceiling: Is this the right idea for the ceiling? Can I reduce the 1" space to even less? a 1/2" taller ceiling would help me in my situation (7'-0" bottom of existing floor joist). 1/2" space would leave me with 4-3/4" total airspace between the 2 leaves. So the question is: Where the outer leaf wall is angled - and it goes all the way up to the existing subfloor - what sort of treatment should I do? See this attached sketch illustrating what I mean. In the sketch I suggested using backer rod and acoustic caulk along the top where the wall meets the subfloor - and also around the existing floor joists. I guess I'll have to notch the gypsum on and angle instead of straight, since the wall is angled. Is this the right idea for the outer leaf wall? There's also the question of what to fasten the vertical 2x4 studs to. See the backside of that same outer leaf wall: Does this wall need a top plate? In other words a horizontally run 2x4 like the inner leaf walls? I'm assuming I don't want to screw through the "beef-up" and into the subfloor. Or can I just screw the vertical 2x4's into the existing floor joists? Come to think of it - I guess this issue will be throughout the whole outer leaf and not just on the angled portions. I am just trying to visualize what will actually happen here and how to support the top of the outer leaf - both where it run parallel to the existing joists, and where it runs perpendicular to the existing joists. The picture is not 100% clear for me yet To fully realize the new ceiling there is also the large support beam that runs the length of my basement. This is going to end up pretty much in the middle/back of my control room. You can see them running in the center horizontally in the first photo. I will have to build the ceiling around that. Here is what I had in mind for that: At the walls: At the vertical columns (there are 2 in the control rom): And heres what I was planning for the regular part of the ceiling where there are no columns: Any help would be greatly appreciated - I am really happy with this current design/layout despite there being COLUMNS and a BEAM...IN the Control Room. I like the big size room and I'm hoping I'm not making any major errors here with the planning. Thanks in advance anyone who can help. My next post will have a potential major serious problem to address but I need a picture to accompany the question so I will wait until I have that. I have a feeling it may be more of a local code type of question so that why I am scared….. One thing at a time...

Ok - I was just over at the house for a few hours doing some clean up and more demolition. Here are 2 photos of the underside of the existing subfloor: Question - am I screwed?!?!? All those angled boards that make up the subfloor are probably tongue and groove - but do they require calking/plastering? Also there is the issue of the many many many many NAILS coming through. I'll hardly be able to firmly press the "beef up" layers to that! I'm assuming I can't just go and hammer those nails through as they are fastening the floor in place, plus I'd push up the flooring on top of that.. I'm thinking I'll need to hammer them all as flat as possible? Any suggestions? Thanks in advance - Mike

ANOTHER UPDATE!! So I heard back from the structural engineer. I can remove the 2 pole that are in the center of my control room!!!! That is great news. I will have to replace the existing wood beams with a steel I-Beam. This also has the added benefit of it being able to be flush with the floor joists. I have options as far as the new steel beam. 1) staying with an 8" height, it would be a W8x58 (pretty massive). This would allow the entire ceiling to basically be flush at 7'-0" OR 2) W12x30 (more manageable). This is a 12" tall I-Beam. The top is flushed up with the floor joists - so the bottom will hang down 4". Much better than the current 7.5" inches the beam comes down to now. Apparently the 12" beam is cheaper (materials) and the labor is also supposedly easier but I'm not sure how much different it is then the 8" beam. This has actually become my most urgent and pressing matter now because I need to choose the beam size immediately so I can have that added to the plans and filed with the building dept. I realize this is not the place to get cost estimates for construction work. But does any one have any idea how much the cost difference is? Or even the overall cost? I am willing to spend up to about $4000 to get these damn poles/columns removed - but if it gets more than that, I may just decide to live with the poles/columns. In the meantime I'm going to get some estimates for the beams and the installation, but if anyone has any experience or think its a bad idea to proceed with the steel beam - please let me know!

Hi All, slight bump here and a few more questions. Its been ages since I've been on here - the house I bought (which is getting the studio in the basement) is taking way longer than expected to move into. Still a lot o work to be done. But its moving along and so I am back to the drafting board trying to get all my ducks in a row. Right now I am waiting to get these 2 lally column removed to I can have an open floor. I will be putting in a steel flush header hopefully in the next 2 weeks. My main question at this time is regarding the ceiling beef up. For the most part I am very luck that the ceiling has no pipes, wires or other obstructions to get in the way of the "beef up" and I've also consulted my structural engineer who approved the use of up to 2 layers of 5/8" gypsum - although I plan on only using 1 layer. In the photo you may be able to see several nails sticking down, presumably the ones used to fasten down the subfloor. I began using an end cutting plier to cut the end of the nails off so I would be able to install the 5/8" gysum flush to the subfloor. I only got a small amount done and I thought - IS THIS OK?!?!?! Will I be loosening the subfloor in some way by doing this? Ive also attached a photo of the latest layout that I've been working on. This is about the 16th arrangement/design I've had - completely scrapped all the others. I know there are some issues with the shape of the room - somewhere else I've read the it is bad to have the rear of the room narrower that the front - creates some sort of compression effect or something. I was wondering if anyone had any suggestion regarding the shape/layout of this design. I'm focusing on the control room at this time. Any advice wold be greatly appreciated! Thanks

Right now I am waiting to get these 2 lally column removed to I can have an open floor. I will be putting in a steel flush header hopefully in the next 2 weeks.

Cool! Don't forget to post photos of how they do that! It's always interesting to see structural engineering at work. I had to do something similar for a studio Canada a while back.

I began using an end cutting plier to cut the end of the nails off so I would be able to install the 5/8" gysum flush to the subfloor.

:shock: :!: :cop: Nope! Don't do that! There's a reason why the poke through. Cutting them off is not a good idea. Instead, use think planks of sytrofoam (or any other closed-cell foam) pressed over the nails, then put your "beef" over that. Get styrofoam that is just a bit thicker than the length of the nails.

IS THIS OK?!?!?!

Nope!

Will I be loosening the subfloor in some way by doing this?

yep!

somewhere else I've read the it is bad to have the rear of the room narrower that the front - creates some sort of compression effect or something.

Yep!

I was wondering if anyone had any suggestion regarding the shape/layout of this design. I'm focusing on the control room at this time.

Why do you need to narrow it down at the back? Could you flip the CR 180° so it faces the other way, to avoid that? Could you turn it 90° ans swap places with the drum booth to avoid that? - Stuart -

Stuart!! wow that was fast! Thanks so much - you just saved me a lot of work! and more importantly now I know the right way to do it ! God I love this forum. The reason for the odd room shape - or at least the reason it narrows at one end - is because of the existing lally columns (shown in red). However - it doesn't NEED to be set up the way it is - on other words - i could flip it 180 degrees. I guess I went with this way because of the vibe/seemed natural - but knowing now about this compression effect things - I could work up a design with everything 180. I suppose I could do a 90 a swap it with the drum room - but that room is much smaller. I know I show the drumset in there - and there will be times I have drums going on in there - but the rums are mostly for jamming purposes with friends - not really to record. Although that does occasionally happen. Mostly I'll be cutting vocals in that room and the main thing I want out of this studio is a great sounding control room. I don't know if you remember Stuart, but I stubbornly insisted upon keeping my Urei 813's as my soffit mounted mains (paired with a (2) 18" subwoofers :shock: ) - so a small(er) control room may not cut it.

I'm also posting this really quickly hoping your may still be poking around the forum Stuart - normally I would wait to fully formulate the idea before asking a question - but maybe you can stop me before I go to far in the wrong direction. I'm working on a soffit design: The ornage-ish boxes around the speaker are going to be 3/4" MDF (2 layers) lined with soborthane (5mm) on theinside, The boxes will be sitting on soborthane or neoprene pads which sit in the concrete CMU blocks. Any suggestion regarding this? The light colored wood framing (front wall)will not be touching the MDF boxes or speakers. I am NOT planning on tilting the speakers forward at all. Height to the center of the speaker box is roughly 4'-8" ( the tweeter/dual concentric speaker is on the bottom - subwoofer on top) so they are low enough. The tweeter will be aiming right at my head while seated. My question mainly are about the whole concept. Are these MDF boxes all it takes to direct/restrict the sound-field to a half-dome (180)? Or does the actual soft wall do some of that? I guess I'm confused about two seemingly contradictory things - I know the front soffit wall - the one flush with the speakers - should be massive and rigid. However some of the designs I see on here, directly behind a thin piece of "bezel" wood there seems to be insualtion inside of framing (open to the back behind that of filled with more insulation). Is the just deadening whatever the MDF boxes don't isolate? I guess I'm having trouble figuring out what areas to "seal" off - if any in around the beck of this soffire wall? any advice?

Additionally - I am NOT planning on venting these speakers in any way - I have tried numerous times to contact JBL (who I think is who to ask nowadays) about weather these need to be vented since the manual says nothing about it - but they have not responded. In my current setup I am using the Urei 813's not soffit mounted just standing in th room on wood framed I made. I have a temperature gun - one of those little handheld laserbeam ones. I aim it at the speaker box before I start a session (powers amps off) and then again after I used for about 10 hours straight. No difference. The boxes are cold always. Cold to the touch. However - I am EXTREMELY prove to changing my opinion based on what I read on here so if this is really really stupid - please let me know, and I will VENT. But for now lets assume I don't need to vent these speakers - Can that help me in some way with the design? Could I just box tightly around the speakers and the use the whole area behind the framing for trapping/treatment?

See photo of the Urei 813: That rectangular cut out is open to the inside - a front port. But it also may help with the heat venting? You can see how far away the drivers are from any exterior surface. Even the back of the boxes stay cold. Any access for maintenance is by just taking off the speaker basket and you have a big 15" hole for access to the inside. So - to vent or not to vent?

As far as the soffit design - I was planning on doing something very similar to this thread: viewtopic.php?f=10&t=17200&hilit=french+cleat&start=45 What I cant figure out is what is sealed off since the center portion of his wall does not have the same layers of gypsum that the speakers walls do.

As far as the soffit design - I was planning on doing something very similar to this thread:

To be honest, I would not use that as a good example of well-designed soffits. There are several issues with the design, both of the soffits and also of the room itself, as noted in that thread.

What I cant figure out is what is sealed off since the center portion of his wall does not have the same layers of gypsum that the speakers walls do.

The soffits do not have to be sealed air-tight. Yes, they do need to be enclosed all around, but you have to punch huge holes in them to provide ventilation airflow for the speakers anyway, so there's no need to seal them hermetically. I normally just build a "box" all around each one, as deep as necessary to fit the speaker in comfortably, then leave the center section between the soffits for absorption, or some other treatment. - Stuart -

Thanks again Stuart, I think a while you back you had mentioned that you had design that may work in my situation, something you had done previously I think I messaged you about it . I was not planning on venting these Urei 813's :shock: . I went on a rant last night but in my previous posts I explained why - however I trust you advice on this so if I NEED to go vented I will. Assuming I do not need to vent these, I still am having some trouble understanding the concept of the soffit, mostly because of a difference I see in the builds (John's and Barefoot's design) and the story/method that John described about how they used to test speakers by burying them in the ground. When burying something in the ground - I fully understand that this would not only eliminate reflections from behind the speaker - but also FORCE the sound to only radiate from the front. A true half dome. But these soffit designs seem to only paying attention to the PLANE right around the face of the speaker. In many cases these don't even seem to be THAt massive and rigid - I believe Johns design only calls for 5/8" plywood and a timber finish. I do understand that this helps. But is this really FORCING the speaker to only radiate forward? Isn't the speaker still radiating sound from the rear but we are just not hearing it since it is being absorbed and blocked by the soffit face? Is everything going on behind this soffit wall basically a tree falling in the forest and nobody is there to hear it? I am trying to visualize a wall built entirely out of concrete , a solid wall, with the only openings being the exact size of the speaker so they sit flush. Assuming no ventilation is required - would'nt this be the best design? I realize that this eliminates the possibility of using some sections of the front wall as bass trapping - but Wouldn't this most closely simulate a speaker being buried in the ground? In this hypothetical scenario - would there be a need for any sort of trapping, insulation or treatment whatsoever BEHIND this wall? In my current design, my speakers are not angled down at all, so it actually may be feasible to build a wall entirely out of concrete blocks, or maybe at least 2 large sections of the wall? I guess this is not really a specific question but I feel like I am at the verge of understanding the soffit design concepts and it's bugging me that I am still so confused about so many things. I also am wondering about the very small space that would result after putting soborthane pads underneath a speaker to decouple it from the box it sits it. Although this is only a very small space, isnt some of the sound from the bottom of the speaker box escaping forward?

The ornage-ish boxes around the speaker are going to be 3/4" MDF (2 layers) lined with soborthane (5mm) on the inside,

That wont work... :) Sorbothane is great stuff (the best, actually), but that's not the way to use it. You need to carefully calculate the load that your speaker will place on the Sorbothane, calculate the correct deflection, and then check the resonant frequency and other parameters to make sure that the speaker really is floating inside the box. I can guarantee that it won't turn out to be a 5mm thick lining all around! It will probably be just a few small pads at strategic points on each side of the speaker. Doing the calculations takes time, and care. If you don't do it right, then the speaker won't float: it will be coupled to the box, and therefore to the soffit structure... I just did a design for floating speakers this way for one of my customers, so I still have all the details fresh in my head. You will need thick Sorbothane, 50 durometer Shore 00, in several small pads.

The boxes will be sitting on soborthane or neoprene pads

See if this rings a bell: If you do that, you will have a mass (the speaker) resting on a spring (the sorbothane inside the box) resting on a mass (the box itself) resting on another spring (the sorbothane between the box and the concrete blocks) testing on another mass (the concrete blocks). So you will have a Mass-spring-Mass-spring-Mass system... :) In other words, that is the exact same situation as a 3-leaf wall. Unless you design it very, very carefully, you will end up with poor isolation in low frequencies... It can be done (I know, because I just did it for my customer), but there's a lot of math and careful design involved. You need to tune BOTH systems lower than you would for either by itself, then check that the COMBINED resonance is still below the lowest frequency of concern (at least an octave below the cut-off), an that both F+ an F- are still below that point.

Are these MDF boxes all it takes to direct/restrict the sound-field to a half-dome (180)?

The boxes that surround the actual speaker do very little, acoustically. Their sole purpose is to hold the speakers in place. Period. What redirects the sound is the very large, flat, massive and rigid front baffles on the soffits. You don't show those at all in your diagram, so it's impossible to see if you are doing them correctly or not. Please add those to your model, and show the images again, so we can see if you are doing it right. Without front baffles, you don't have a soffit mount.

Or does the actual soft wall do some of that?

What do you mean by "soft wall"? There is no soft wall in a correctly designed soffit mount.

I know the front soffit wall - the one flush with the speakers - should be massive and rigid.

Correct.

However some of the designs I see on here, directly behind a thin piece of "bezel" wood there seems to be insualtion inside of framing (open to the back behind that of filled with more insulation).

I'm not sure which design you are talking about. Do you have a link to that? It's hard to discuss something that you can't see! :)

I guess I'm having trouble figuring out what areas to "seal" off -

The interior of the soffit does not need to be sealed. Indeed, it cannot be sealed, because there needs to be ventilation air flow up past the rear of the speaker (yes, there NEEDS to be that). Those speakers are sucking up a few hundred watts of electrical power, and concerting 99% of it heat. That heat needs to be removed. If there is no ventilation, the speakers will keel over and die, very soon. Speakers are NOT designed to be used without ventilation around them. If you are in doubt as to how much ventilation they need, ask the manufacturer.

I am NOT planning on venting these speakers in any way -

:shock: :!: :ahh: You must have lots of money to spare then, to buy new ones every few months, as the old ones burn out... :) Your speakers are rated to absorb 200 watts of electrical power, continuous. Only about one watt of acoustic power comes out. The rest goes into heat. Enclosing those speakers inside a wooden box is almost the same as enclosing two 100w electric incandescent light bulbs in a box...

The boxes are cold always. Cold to the touch.

That's because right now all of the excess heat is radiated out through the cabinet walls. That's a very large surface area. When your speakers are soffit-mounted the way you want to do it, the cabinet surface area available for cooling will be zero. The laws of physics are immutable: if you pump 75 watts of power into that speaker, then 75 watts must come out. One half of a watt of acoustic power, and 74.5 watts of heat. That heat has to go somewhere!

Could I just box tightly around the speakers and the use the whole area behind the framing for trapping/treatment?

Yes you can, except for the small volume that you need for the ventilation path. That can be done with "chicken wire" that you shape to create a "chimney" for the air flow, around the back of the speaker cabinet.

So - to vent or not to vent?

You MIGHT be able to get away with not venting, but why run the risk? It is so easy to create the vents you need, there is no acoustic penalty, there is no aesthetic penalty, the cost is practically nothing... Why risk damaging your speakers, when there is no need to? What is the basic reason you have for NOT wanting to ventilate? I really can't think of any valid reasons at all! - Stuart -

Stuart!!! Thanks a million. you've convinced me - I SHALL VENT! These are really big boxes so I understand that the heat is dissipating over a large area which is why I cant detect it by hand or even temperature gun.

What is the basic reason you have for NOT wanting to ventilate? I really can't think of any valid reasons at all!

I guess I just was/am still not fully understanding the concepts and thought completely sealed would be better. Additionally thought it may be a little easier to build without the vent. But when you explain it that way it doesn't really seem like too much and better safe than sorry. Oh and being stubborn too did I mention that? lol - But I digress - I SHALL VENT

I just did a design for floating speakers this way for one of my customers, so I still have all the details fresh in my head. You will need thick Sorbothane, 50 durometer Shore 00, in several small pads.

Amazing, thanks again. I'll double check my weight loads, etc.. before I actually build but this is great info.

So you will have a Mass-spring-Mass-spring-Mass system

Ok so I will definitely NOT being lining the box AND doing the pads (M-S-M-S-M), I'll just stick to (1) layer of properly compressed "S"

What redirects the sound is the very large, flat, massive and rigid front baffles on the soffits. You don't show those at all in your diagram, so it's impossible to see if you are doing them correctly or not. Please add those to your model, and show the images again, so we can see if you are doing it right. Without front baffles, you don't have a soffit mount.

I posted that design up too early, I haven't even got to the front wall material yet although I was pondering 2 layers 5/8" with a finish wood over that. I have like 3 designs going at once - another one the whole wall is built out of CMU blocks. Another design has a corner control room design. Stuart (or anyone who knows speakers). I think the answer to this question will help me understand the whole soffit design thing. How does a speaker radiate sound 360 degrees? (see photo) please excuse my HORRIBLE quick sketch I think the answer to this will help me understand HOW the sound field is restricted to 180 degrees through soffit mounting. As a side note - I do understand the concept of edge diffraction and SBIR. It's more the concept of "Acoustical Loading" that I am struggling with

Quote: However some of the designs I see on here, directly behind a thin piece of "bezel" wood there seems to be insualtion inside of framing (open to the back behind that of filled with more insulation). I'm not sure which design you are talking about. Do you have a link to that? It's hard to discuss something that you can't see! :)

As far as the other designs - I was basically referring something like this: link here: viewtopic.php?f=12&t=18061&start=30 Or John's design: link here: viewtopic.php?f=1&t=16515&view=next there's loosely packed insulation behind the wall, sometime I see hanging bass traps there too. Are these helping with the control rooms acoustics or are these helping damp down the sound emitting from the rear of the speaker? This is why I really need help with my question regarding HOW a speaker emits sound. Does it come FROM the rear? Also I am not seeing the "massive" front wall. 5/8" plywood and timber finish? If the box that goes around the speaker (assume made of 5/8" plywood) does little to block sound (and is for mounting purposes mostly), then how is this 5/8" plywood with timber finish blocking it? I also understand that the acoustic hangers BELOW the shelf in Johns design ARE for the Control Room acoustics, its mostly the stuff above I'm wondering about. I've also seen some actual construction photos that show similar which I'll try to locate, but this is basically what I was referring too. This is from "Somewhere" Studios I believe John designed. Although unfinished - you can see the speaker is almost already entirely flush with the front of the box meaning the Bezel - or "massive" front wall is only going to be millimeters thick. This guy used 2 layers of 3/4" MDF for the front walls - seems reasonable to me - but It's also what I suggested making my speaker boxes out of which Stuart mentioned does very little for sound blocking. Is this "massive" enough. There also a bezel he adds made of wood which I'm assuming is also 1-1/2" thick but he doesn't indicate that. This guy's "massive" walls seem to be made out of FABRIC?!?! :shock: link here: viewtopic.php?f=10&t=9156&start=285 Im not saying all of these are right or the same concept but a lot of these builds, even ones that seem to have no budgetary constraint, confuse me when it comes to the soffit walls. I'm following everything - and then when it comes to the soffit I'm scratching my head like WHY?!?! Just to be clear - I have no issues just following the Sayer's or Barefoot design completely, although I know my situation (every situation) is unique and needs fine tuning. But instead of just "doing" it - I'd much rather UNDERSTAND it! - Mike

Stuart!!! Thanks a million. you've convinced me - I SHALL VENT!

:thu:

Amazing, thanks again. I'll double check my weight loads, etc.. before I actually build but this is great info.

Sorbothane provide a calculator app for figuring that out, but you do need to understand how it works, and what the numbers mean.

Ok so I will definitely NOT being lining the box AND doing the pads (M-S-M-S-M),

Well, you can if you really want to, but it does have to be calculated with care, like any other 3-leaf system.

How does a speaker radiate sound 360 degrees? (see photo) please excuse my HORRIBLE quick sketch

A bit of both, actually! There will certainly be some very low frequency vibrations induced in the cabinet itself, simply due to the motion of the drivers. That's a fair amount of mass moving backwards and forwards, and Newton's laws talk all about action and reaction... if the driver shoves the cone forwards, then the cone shoves the driver backwards, and since one of them is attached to the box, then some of that energy is transmitted into the box. The moving parts of the cone only weigh a few grams, and the box weighs several kilograms, so the effect is not huge to start with, but at high power levels, yes, there is some radiation going on from the cabinet itself due to this. Also due to the massive pressure changes going in inside, which are attempting to make the entire cabinet "breathe" or "pump". Hence, the need for a massive, rigid surround, to minimize all of the above. But most of the "backwards radiation" effect comes from edge diffraction, and the simple fact that, for wavelengths larger than the smallest dimensions of the box, the entire speaker acts as a point source anyway. The simple act of the cone pushing large volumes of air forwards and backwards induces the same motion in the surrounding air. Sort of. It's a bit more complex than that, but that gives you a neat mental picture of what is going on. Another way to look at it is that each wave appears to emanate from the center of the cone and spread out as a sphere in all directions, for all wavelengths larger than the smallest dimension of the baffle. From that point of view, part of each wave appears to be spreading across the speaker baffle "sideways", starting in the middle and running outwards, across the face of the baffle. And when it reaches the edge of the baffle, due to the sudden change in impedance, the wave appears to "wrap around the side" of the speaker, and continue spreading out towards the back. And a soffit mount deals with ALL of these issues! The "muddy" energy being radiated by the cabinet itself is firstly contained within the soffit by the enclosure box around the cabinet, and is also greatly damped by the resilient mount in the Barefeoot design, as well as being damped even more by the large quantities of porous absorption inside the box. Any residual energy is even further contained by the front baffle of the soffit: it can't get out that way at all. Secondly, the front baffle of the soffit prevents the motion of the cone from causing motion in the air to the sides of the speaker, for obvious reasons. Third, the wavefronts that appear to be expanding outwards across the front panel of the cabinet, never reach the "edge", because the front baffle of the soffit is a continuation of that, and the walls of the room are a continuation of the soffit: Those waves cannot "wrap around" behind any more, because there is no place that they can ever get "behind" any more. For the same reason, there is no edge diffraction: there is no edge! This is the reason for the 6 dB bass boost that you get from soffit mounting: For all frequencies where the wavelength was shorter than the dimensions of the cabinet, half of the energy wrapped around behind and went backwards, while the other half went forwards. And since "half of the power" is the same as a 6 dB reduction in power, the manufacturer had to boost the bass power by 6 dB to balance the power levels again. With the soffit, that is no longer necessary, because ALL of the energy is now going forwards, at all frequencies. None of it is going backwards (except for the small amount from the actual cabinet vibration, which isn't very much).

I think the answer to this will help me understand HOW the sound field is restricted to 180 degrees through soffit mounting.

I hope so!

As far as the other designs - I was basically referring something like this:

I would not do the first one, for several reasons. Not a good design. The second one is much better.

there's loosely packed insulation behind the wall, sometime I see hanging bass traps there too.

Don't think of it as a wall. Yes, in reality it sort of is a wall, but as far as the speaker is concerned, it is an infinite baffle and an enclosure and a rigid / resilient mount. The area behind the speaker is normally divided into sections, as well: there's the main section, where the speaker itself is, then the bass trap section down below, and perhaps also another bass trap section up above.

I see hanging bass traps there too. Are these helping with the control rooms acoustics or are these helping damp down the sound emitting from the rear of the speaker?

Room acoustics. Technically, those are in the room corners, which is a real good place to put bass traps. There's a large opening at the bottom of the soffit baffle, into the room, so that the hangers are exposed to the room air.

This is why I really need help with my question regarding HOW a speaker emits sound. Does it come FROM the rear?

Not really: it wraps around from the front, mostly. There IS some emission from the rear, but very little. (Different for the case of rear-ported speakers, of course...).

Also I am not seeing the "massive" front wall. 5/8" plywood and timber finish?

An inch and a quarter of solid wood isn't massive enough? That's around 20 to 25kg/m2...

f the box that goes around the speaker (assume made of 5/8" plywood) does little to block sound (and is for mounting purposes mostly),

It is in direct contact with the speaker cabinet (in the Sayers design) so it transmits then energy quite efficiently... but there isn't much energy there! That is structure-borne energy, not air-borne energy. The front baffle is dealing with air-borne sound, not structure-borne sound.

I also understand that the acoustic hangers BELOW the shelf in Johns design ARE for the Control Room acoustics, its mostly the stuff above I'm wondering about.

The stuff inside the soffit itself (above the shelf) is mostly for damping of the sound inside the soffit cavity, some of which comes from the speaker vibrations, and some of which comes from it just being a tuned cavity. Think of it this way: the soffit is just a giant speaker cabinet, and like all speaker cabinets, it needs internal damping.

Although unfinished - you can see the speaker is almost already entirely flush with the front of the box meaning the Bezel - or "massive" front wall is only going to be millimeters thick.

Ummmm not really! That's an Adam A7, A7X, or A8X. Here's a view from a different angle... There's at least an inch and a half there, from the point where the bevel ends on the speaker cabinet, to the front face. That's a lot of wood. Plus a few more mm probably: the top edge of the bevel seems to be sticking out a bit in that photo...

This guy used 2 layers of 3/4" MDF for the front walls - seems reasonable to me

Yep!

but It's also what I suggested making my speaker boxes out of which Stuart mentioned does very little for sound blocking.

I think you misunderstood what I said: I said the enclosure box around the speaker cabinet does very little to stop the sound wrapping around from the front to the back.... But that's NOT the same as what the front baffle of the soffit is doing. Very different things....

This guy's "massive" walls seem to be made out of FABRIC?!?!

Then it ain't a soffit! :)

Just to be clear - I have no issues just following the Sayer's or Barefoot design completely, although I know my situation (every situation) is unique and needs fine tuning. But instead of just "doing" it - I'd much rather UNDERSTAND it!

I can't take the credit for John's design! That's all his work. I have done soffits based on both John's philosophy, and also on Thomas's philosophy. Both work. Of course, I do add a bit of my own ingenuity in both cases.... :) - Stuart -

STUART!!!!! THANK YOU SO SO MUCH!!! Amazing response - this has helped me immensely!! Hopefully I'll have time to work on my sketchup model tonight and this weekend so I can move forward with a soffit design now that I have a better understanding of whats going on. I already have a few new questions formulating in my head but I just wanted to get this THANK YOU out there now since it may be a few days until I post a new sketch and new questions and pictures. Construction update: I just made the decision to go with an "almost" completely flush header in the basement. Originally I had it planned as a 12" tall I-beam that is flush to the subfloor (would have protruded 4 inches down). Instead, I am going with an 8" tall I-Beam which will be flush with the subfloor AND the bottom of the existing floor joists. I'll be sure to post pics of this too - I think I may have the temporary support walls built this week or next in preparation. - Mike

:thu: That's what we are here fore! :) - Stuart -

Hey Stuart (or anyone else if you can help) I have one quick question: Do you know if I would be able to use these Sorbothane Stud Mounts? JPEG here in case the attachment doesn't work Urei 813 = 176 lbs (1) 4' x 8' x 3/4" MDF = 96 lbs Based on the proposaed size of my MDF boxes - each layer is approx. 172.25 lbs) Therefore Urei 813 + (1) Layer of MDF Box = 348.25 lbs/ea If I was to use 2 layers of MDF box then approx = 520.5 lbs/ea I think up to here my math is correct. THEN Using the Sorbothane Part number I selected - I chose to divide my combined weight (348 lbs) by the MIDDLE number in the RATED LOAD of the stud-mount (20-40 lbs). IS THIS RIGHT?!?! So 348 LBS/30 LBS Based on that it looks like I'd need (11) pads if I go with one layer of MDF Box or (17) pads if I go with two layer MDF Box. (again I'm not sure if this math is correct) The reason I want to use these threaded stud mounts is to eliminate the need for a strap (like in barefoots design) or coupling to the front wall in close proximity to the speaker. I was hoping that by using these stud mounts - I could ensure that the MDF boxes don't "shimmy" out of place from vibrating over time - and also ensure that the boxes don't get knocked even by a 1/16" of an inch for any reason, ruining the decoupling from soffit face. I don't know if any of this logic is correct so please let me know. Here a shot of the current soffit design I've been working on. I am stuck because I need to know the thickness of the pads to use. I plan on putting these stud-mount pads between the concrete stands and the MDF boxes. This way I could fasten them and prevent any horizonal movement (beyond the pads deflection) while still de-coupling. 1) Shown is (2) layers of MDF Box but I haven't decided on (2) or (1) yet. Any advice is appreciated. 2) Now the piece of 3/4" plywood that would be the "shelf" in Johns design (the piece that separates the top and bottom portion of the inner soffit) would NOT be touching the concrete stand. Again my thought on this is decoupling, although I do realize that the speaker is already decoupled from the concrete stand so maybe this is not necessary. I show a 1/16" gap between the wood and concrete. If this IS a good idea..then should I caulk or backer-rod this gap? 3) Air Vent for cooling is shown as approx. 3" dia. Let me know if I need to go bigger. Also I only show it on the bottom of the box - I know it needs it on top too. 4) How much airspace behind speaker inside the MDF Box? - Right now I have about 3 or 3-1/2" 5) I also show a 1/16" gap around the front plane of the soffit framing and the MDF box is flush with the framing. The speaker protrudes out of the box 1-1/2" to allow for 2 layers of 3/4" ply or MDF. This can be easily adjusted (in the design) depending on the materials used if someone has a better suggestion of what to make this "massive" front wall out of. This last shot is where the Sorbothane stud-mount Pads would go (in between MDF box and Conc stand). I couldnt figure out how to point out the area in Sketchup but hopefully you can see the gap wherer the pad would go. A few notes: 1) I know my MDF box is incomplete I left those 2 sides off so we can see inside. 2) Obviously the front wall material is also not shown as I haven't really decided what to use yet!! 3) Obviously the internal soffit framing is not complete either yet - kinda caught up at this point. Hey wait a sec - that was NOT 1 quick question :shock: one slight edit here - i attached another photo to clarify that the "shelf" is not sitting on the conc stand - some of the previous pics look that way. The stand actually sits up a bit higher that the height of the shelf - this pic is exaggerated but it clears that up: Am I on the right TRACK here?!? another update I may as well include in this same post: 2 options for the soffit face wall. OPTION 1 (smaller size soffit but flush with subwoofers): OPTION 2 (larger soffit face - creates strange "shelf" area above subwoofers, smaller area to mount a flatscreen TV.): Last question is regarding DOORS!! (I know that sort of came out of left field) In Rod's book he details a SINGLE door that goes between both leaf walls. Instead of the typical double door (1-in each leaf) method. Is this ACCEPTABLE?!? Not a MAJOR issue - but if I can have 1 heavy duty door - it would allow me to put the entrance to the control room right at the bottom of the stairs and swing INTO the control room. If 1 NEED a 2 door assembly - then I CANNOT have my entrance at the bottom of the stairs.

Ok so that last post was kind of all over the place, I'm going to try to simplify my main problems and questions: 1) Sorbothane stud-mounts (part no: 0510350-50-10). Are these ok to use under the speaker or speaker box? 2) Is a (2) door assembly REQUIRED through a 2 leaf wall system? Is the single heavy duty door detailed in Rod's book acceptable? What are the downsides if any? 3) Does the inner soffit "Shelf" (in my case not supporting anything, just separating the top and bottom halves of soffit) need to be de-coupled from the concrete stand? 4) Is a 3" dia. air vent opening sufficient in the speaker box? Is 3-1/2" open space in the rear of the box sufficient? 5) I am thinking of using (2) layers of 5/8" plywood for the inner soffit walls (shelf, bottom and side). This was just to roughly match the front soffit wall which I'm thinking will be (2) layers of 5/8" MDF or maybe (1) layer 5/8" MDF, (1) layer 3/8" MDF and then a 1/4" finish wood. The reasoning for "beefing" up the layers beyond John's design was because these speakers are just larger than most of the design's on here that I am basing this off. As a side note I realize there are a few 3-leaf situations going on here - and I don't know how the equation for a 3-leaf works out - but I'm assuming that increasing "d" (or the airspace) would also help lowering the res. freq. in that equation, just as it does in the 2-leaf equation. There seems to be a significant amount of airspace between the leaves. Is this correct? 6) This brings me to the next question regarding isolation. If I'm doing the math correctly then the weakest point should be where the air gap is 8" and between two NEW studio walls made of (2) layers 5/8" drywall. This works out to be about 49.6Hz I think. I tried messing around with the formula increasing the gap by an inch or two and also adding a layer of 3/8" plywood. Adding 1" air gap - while completely free - only brings me to about 47Hz. (2) layers of 3/8" plywood (1 on each leaf) - while losing about the same amount of space - and cost way more money - brings me to about 44.8Hz - not too shabby. Adding an inch air gap on top of that I'm down to 42.7Hz. If I calculate between a (2) layer 5/8" wall and a concrete wall (8" gap) which I DONT know the surface density of (I couldn't figure out how to get kg/m^3 to kg/m^2) - but I plugged in 72 kg/m^2 as a guess. This gave me 37Hz. I would assume that these areas would give better isolation. I am slightly confused however because I thought I remember reading that having the 2-leafs being different masses is bad. I know there is a 3-leaf situation going on as well between the 2-new leafs and the concrete wall - basically the area where the couch is shown. But again the airspace is very large there, and I don't know the formula. So this question is 2 parts: a) I know the system is only as good as the weakest point - BUT, is my isolation to OUTDOORS, going to be better than my isolation BETWEEN two new studio walls? Since all of the leaf(s) between the outdoors are around 37Hz, (except for the 3-leaf thing going on in the couch room) and between new walls it's 49.6Hz?? b) WOULD a layer of 3/8" plywood going down as the first layer - be sufficient enough support to use to fasten the subsequent layers of 5/8" drywall? I did this years ago in my current studio - used a layer of plywood first - making it very easy to attach layers afterwords (and basically anything on the walls afterwords for that matter) since everywhere is "screwable". However it was only (1) layer of 1/2" gypsum on top and I didn't know WHAT I was doing at the time. 7) In John design, an illustrated in this pic, there is an offset, approx. 3-1/2" deep, just BELOW the face of the soffit, where the soffit is offset and the plywood layers are on the INSIDE of the soffit. Would this cause a point of diffraction? I know he puts the rigid insulation there to treat reflections off the console, but is this the lesser of two evils? Would it be possible to keep the rigid flush face all the way down to 12" above finished floor? In the case that case you still want to treat console reflections, you could add rigid insulation to the face of that - although now it would not be flush. To me it seems that having a soft surface protruding is better than a 3-1/2" offset in the rigid face? See below for illustration. Option #1 Johns basic design with offset rigid surface: Option # 2 Rigid surface is flush - console treatment protrudes out: #8 Lastly - just want an overall idea if this current soffit design is going ok. I tried to maximize the size of soffit face. I also remember reading that the speaker should not be dead-center of the soffit face, so I chose to extend the soffit only a certain amount. This reduces the size of the strange "shelf-thingy" created above the subwoofers, although it is still there somewhat. - I AM wondering if I should box in around the top of the subwoofers or just leave it open to above and filled with insulation. The subs are not in there tightly at all, there's a few inches in between them and on the sides as well. Also not sure if this front section needs a massive wall at all - or should I just cover this section with fabric to leave it open to the room for bass trapping/treatment? No insulation is shown - or isolator pads yet since I'm not sure what to use. The RIGHT speaker and soffit is the one we are looking at, once I finalize that side I'll copy it over to the left - that is why the left side is incomplete.