NEW Basement Studio Design in New York. Looking for advice

The span is a little less than 11'-0". About 10'-8". I believe the number I came up with was around 13psf for the load

:thu: OK, that sounds about right. It looked like a longer span in the photos. Optical illusion, I guess.

Independently?

Right. The layers of a leaf act both together, as a single mass, and also independently.

I don't think I am following? Did I do ALL MY WALLS WRONG TOO? I screwed the gypsum to the OSB? they are 100% directly fastened to eachother rigidly.

You should only use screws (or nails) into the STUDS (or joists). Yes, the screws on the drywall will also go through the OSB, then into the studs, but you don't ever screw only into the OSB where there is no stud behind. If you screwed the drywall into the OSB away from the studs, then that's not so good. It's the same as gluing the layers together. Screwing or gluing two panels solidly together will make them act as one, with one single coincidence dip frequency taht will be LOWER than the individual coincidence dips for each panel by itself, and the bend/flex characteristics will also be different from having the panels separate. In almost all cases, this is not good for sound attenuation. When the panels are only attached to the studs, with broad open areas between them, even though the faces are in contact they can still move independently, with the layers sort of "sliding past" each other if necessary, especially with the case of bending waves, but also with plain old flexing waves. To understand with a simple practical illustration: pick up any paperback book that you happen to have on hand, and firmly grip the spine in one hand and the opposite edge in the other hand, pressing the pages together tightly. Now bend the entire book, so that the front bends towards you, then away from you, then towards you again. Not what happens to the pages in the middle of the book: they slide past each other as the "flexing wave" moves through the book. In effect, that's what happens to the layers in a leaf on the wall as sound waves cause it to flex, just on a smaller scale. The friction between layers adds to the isolation, since it removes some of the flexing and bending energy. And that's what Green Glue helps with: it damps that "sliding" action, since it is viscous, so it removes even more of the energy than friction alone would. But if you rigidly attach the layers to each other with screws out in the "field" of the sheathing, then that action cannot happen, and the two layers act more like a single, solid, rigid block, with a lower coincidence dip. This is the same reason why windows should be laminated glass, which is two thinner panes of glass with a flexible PVB bonding layer between them. That allows the two panes to flex and bend independently, as well as together, and the interlayer absorbs some of the flexing/bending energy. That's why laminate glass has superior isolation to what you'd get from a single solid glass pane of the same thickness.

I did NOT use green glue. Is green glue REQIURED?

No, it's not required. Not at all. It helps, yes, since it puts a damper on several types of resonance that happen in the wall sheathing, but it is not NECESSARY to get good isolation from a wall. It's just an extra boost for low frequency isolation. It works, yes, but it's expensive. So it's a cost/benefit thing: If you absolutely must have the best possible low frequency isolation, then it is worthwhile using Green Glue. But if you don't absolutely need that extra boost, and can't afford the extra cost, then that's OK. The wall won't isolate quite as well as it would have WITH the Green Glue, but it also won't be terrible! You can get roughly the same boost as Green Glue would give you, by simply adding one more layer of drywall. So basically: It's nice to have if you can afford it and can justify the cost, but is not required. Not by any means.

Why can I not have the gypsum screwed into the osb? I though the whole point was to make a massive leaf?

Yes, you certainly do need the mass! But mass is only one aspect of how walls isolate. There are four main aspects: Mass, spring, resilience, and damping. And there are five regions of the spectrum where each of those has a different role, with some being dominant in one area and others dominant in other area. For frequencies BELOW the MSM resonance of the wall, resilience rules. Down that low, it is the key aspect. The walls "breath", like a balloon inflating and deflating, in sympathy with the sound pressure. You want the wall to be flexible and resilient but also damped for very those low frequencies, since that's the major mechanism that is removing energy from the waves. Around MSM resonance, mass, spring and damping matter most, with resilience being less important. Between MSM and coincidence, mass matters most (although the others do still play a role: just reduced). At coincidence, we get back to resilience and damping. Above coincidence, it's mostly mass again. There's a LOT going on in a wall to get you good isolation at all frequencies. Imagine how hard that wall is working when you have a deep sub-sonic thump from the kick, plus the bass guitar doing things around MSM, the keboards fleshing out the middle, the electric guitar smashing into coincidence, and the cymbals screeching through the top end... all at once! The wall is doing all sorts of stuff together to isolate all that, and of course, there's also interaction between them: the ultra-low flexing of the wall has the bending wave from the bass riding on it, with the mids and highs superimposed on that... so each panel of the wall is vibrating in several different modes at the same time... It gets complex!

I've been on here for 3 years and I dont even know how to build a wall!

It's not that bad! You have built them quite well... maybe not optimally, but certainly not bad!

I thought the reason I used cleats for the "beef-up" was so that I didn't risk putting a nail through the sub-floor or pushing up any floor finishes above?

Not really: it's mostly to keep the panels acting separately. If it weren't for that, you could just use shorter screws...

I just want to know if I missed something major and I'm doing all my walls wrong too?

I'm not 100% clear on how you did those: if you ONLY put screws through the drywall where the studs are, then that's great! But if you ALSO put ADDITINAL screws through the drywall and into the OSB at locations where there are NO studs behind, then that might be a problem... The magnitude of that potential problem is hard to predict...

Ok yes 10% is a significant amount, I guess I was thinking the MSM system had more to do with Volume of the cavity.

Actually, not really! there's no parameter in the MSM equations for volume. Only for depth. There's only three variables that you can change in the equation: the mass of the leaves, the distance between them (depth of the cavity), and the damping factor (given by the insulation). The volume of the cavity does not come into it, for MSM. Here's the actual equation: f0 = C [ (m1 + m2) / (m1 x m2 x d)]^0.5 Where: C=constant (60 if the cavity is empty, 43 if you fill it with suitable insulation) m1=mass of first leaf (kg/m^2) m2 mass of second leaf (kg/m^2) d=depth of cavity (m) That's it. No volume.

but when you look at the cubic volume of the overhead cavity, we are talking like less than 1%?

Right, but not relevant! :)

Just a visual glance at one of the bays you can see that it's about 99% filled, not 90% filled.

And that's a good thing! But that is "damping factor" in the equation, not "cavity depth"...

Either way, this point makes a lot of sense so I think I will be increasing the gap in the control room.

One way you could do that is to simple drop the "modules" down an inch. Instead of having the bottom face of your module flush with the bottom of the joists, they would be an inch lower. That still gives you an inch and a half of contact between module frame sides and the joists, which is fine. Yeah, that means the bottom edge would be an inch lower, which might not be so pretty... but I'm assuming you'll be covering those modules with fabric of some type, so you could just paint the bottom face of the joists black, and that can look nice up there.

As far as the reduced isolation I'm starting to lose track of all the many many many places where I have settled for (slight loss in isolation) over and over again. Single doors, less MSM distance than I would have liked, AC openings, electrical conduits, no green glue...... I'm wondering if I'll have any isolation at all once these slight losses add up to a big loss in isolation

How much isolation are you shooting for? What's your "number"? (in decibels) If you really suspect that you aren't going to get there, then you can always add another layer of drywall to all of your inner leaf. If you do that on your ceiling you should re-check with your engineer, but from what you said above, there seems to be enough margin to handle the extra load (the walls are not a problem from that point of view). There are solutions... :) - Stuart -

Stuart! Thank you immensely for the in-depth and extremely informative reply! Totally makes sense now about the wall panels being independent and "sliding" past each other as part of their isolation. I shall use the cleats! For the walls, yes I landed the screws on the studs (or at least that was the goal, there was no real way to check behind to see if I missed slightly). I didn't put any screws in between the studs just to the OSB (at least not intentionally). Dropping the modules seems like a great solution!

here's no parameter in the MSM equations for volume. Only for depth.

Gotcha - I was always wondering about that - In a previous post I even had proposed a sealed "chimney" to increase the cavity volume, but now I see that would not make any difference. I have a few more questions I am fleshing out before I post on here, but just wanted to say thanks right away since you replied so fast!

For the walls, yes I landed the screws on the studs (or at least that was the goal, there was no real way to check behind to see if I missed slightly). I didn't put any screws in between the studs just to the OSB (at least not intentionally).

Then you should be good! :thu: - Stuart -

Just a slight update regarding the ceiling modules. So I took some measurements. Here is the gap between existing and new ceiling. It's actually about 3/4" in almost all areas. There however definitely are some spots that are as narrow as 1/4". I think in addition to the floor joist not being 100% level, the new ceiling grid is actually slightly deflecting downwards under its own weight, making the gap larger the farther away from the wall. If I do a pull-up on the ceiling joists, I can visually see the ceiling deflect down even more. I'm thinking that once all the modules are in, there would be similar weight deflecting the ceiling downwards, making the gap larger than it currently is. Does this make sense? Obvious, around the perimeter, the gap would stay where it is, but towards the middle of the span it would be increased? Also, see photos of how the (1) module is currently installed (still need to redo/add cleats). In order to have the top flush, I actually recessed the module into the framing slightly about 1/4" So if i was to bring the module down flush with the bottom, that should give me the overall 1" gap. At least this would be the case in MOST areas. Then, factoring in the deflection that will happen on the new ceiling, that gap may even be more than 1" Let me know if this makes sense. Flush bottoms for the modules and framing would be the easiest to deal with anyway. Side note: The existing floor joists are 1-3/4" wide by 7-1/2" tall.

the new ceiling grid is actually slightly deflecting downwards under its own weight,

By how much? Is it the same amount as you factored in when doing the span calculations? If it is greater than the factor you got with the span calculations, then that could bs a sign of overloading. If it is less, then you are fine. But it's important to check.

If I do a pull-up on the ceiling joists, I can visually see the ceiling deflect down even more. I'm thinking that once all the modules are in, there would be similar weight deflecting the ceiling downwards, making the gap larger than it currently is. Does this make sense?

Yes, but once again, the deflection must be what it is supposed to be! If you are seeing a large deflection with just you hanging on it, that might be a cause for concern. Your weight is negligible compared to the weight of the entire ceiling...

So if i was to bring the module down flush with the bottom, that should give me the overall 1" gap.

I would still bring the modules down more. The bigger the gap, the better, and you do need to get insulation in the gap without having to compress it so much that it bridges. - Stuart -

Hey I'm back! I know I've been MIA for a while, just got busy with life stuff. So here's an update I currently building the silencer boxes, here a few photos: The "shelves" inside the boxes are fastened using these small angle clips with 5/8" screws. You can see them in the shadow in the first pic (no screws in them yet) The insulation was attached using some 3M spray adhesive and then fastened with 1-1/4" screws with big washers, just barely compressing the insulation, just so the washer is not loose. EDIT/UPDATE: THIS POST WAS WAY TOO LONG - I HAVE SHORTENED IT TO JUST THE 2 ACTUAL QUESTIONS I HAVE: Question 1: Can/Should I use SC-175 acoustic sealant on the inside of the box to seal the edges of the duct liner insulation? (SEE PHOTOS) This is to prevent fibers from coming loose into the air-stream over time. Normally, in metal duct, this is achieved with the use of what is called "nosing" which is just an additional piece of metal that covers the exposed edges of insulation. Question 2: Back to Door Frames for a minute - I know that MLV has very few practical uses - however I am still deciding exactly how to do my door frames. As of now I am going with rods "THROUGH-FRAME" which couples the leaves together. I don't like that. So I am wondering If I can go with the following idea: This would only require a VERY MINIMAL amount of MLV - maybe a 3" wide strip all around the door. Maybe 2 layers if deemed necessary? Would this be one of the few good uses of MLV? You guys think this would work?

Hey Rich, Decided to check out your thread questions for fun. I didn't do any caulking in my silencer boxes, though I can't say its a bad idea. Too late for me now. Everything seems fine here. Of course without sending any dust off for analysis, who knows? I didn't use fender washers on them either which is kinda dumb in hindsight. What was I thinking? :lol: I'm wondering how come there aren't 2 doors in your wall design? I don't have a need to cover the gaps between my walls because I have a door on each wall. The space between the 2 doors becomes part of the decoupling space and so no isolation is necessary. Not doing a door on each wall?

Hey Stadank!!! Thanks for checking it out!

I'm wondering how come there aren't 2 doors in your wall design?

:cry: Unfortunately, I don't have the room to put 2 doors. If you look at the door to enter the studio at the bottom of the stairs, there no way to have a door swing out because the stairs are in the way. That right there limited me to go with the single heavy duty door design. Since I was already doing (1) single door - I figured I may as well do both that way :? I COULD use a 2-door system between the control room and the live room (Its actually not too late to do that), but I don't know how much that would help my overall isolation since I'm already forced to do the (1) single door. If (for example) I lose 5dB of isolation by using a singe door - does that mean I'll lose 10dB if i use (2)? I also really like the idea of an artist not having to do anything other than push 1 door open to get into the booth, and having it close and seal on its own. There's always the need to go back into the booth and fix a line, ya know, lots of traffic between the control room and booth. As of now - this is what I'm planning (from Rod's book) This is so counterintuitive to me that I'm trying to find a better way. With the MLV, I'm hoping to have the continuous mass, while also decoupling the walls. P.s. your silencer boxes look great and your doors look AMAZING!

there no way to have a door swing out because the stairs are in the way.

So get rid of the stairs then! Overrated. Just jump. :shot: :mrgreen: Any chance you could fit two half-doors in there, that meet in the middle, for the second door? It won't be as good as two complete doors, of course, but much better than just one. Having just one door puts a heavy limit on what you can achieve, with isolation. Mass-law is not your friend. Also, I normally have at least three studs on each side of a door frame: Those doors are HEAVY! You need lots of good, rigid support at the back, to keep things straight and plumb. Also use at least three noggins in the first bay out to each side, then two in the next bay, and then down to one for al the others. So instead of being 48" OC (vertically) in the first bay, they will be more like 18" OC, then maybe 24" in the second, etc. Frame the hell out of doorways and windows!.

If (for example) I lose 5dB of isolation by using a singe door - does that mean I'll lose 10dB if i use (2)?

You'll lose a LOT more than 5 dB by having only a single door! Your isolation is limited by mass law: TL = 14.5 log Ms + 23 dB (where: Ms = Surface Mass in lb/ft2 ) Do the math: I think you won't like what you see. You need ginormous amounts of mass to get decent isolation. You seem to be aiming for about 50 dB isolation with your walls, so turn the mass-law equation around and see how much mass you need on your door to reach 50 dB... :) :wink:

I COULD use a 2-door system between the control room and the live room (Its actually not too late to do that), but I don't know how much that would help my overall isolation

IT would do wonders for the isolation between CR and LR, for sure! Your "single-door" dilemma is only between the CR and the outside world, and has no real effect on the isolation of the LR.

This is so counterintuitive to me that I'm trying to find a better way. With the MLV, I'm hoping to have the continuous mass, while also decoupling the walls.

I would not use MLV for that: it's too heavy and not flexible enough for good isolation, plus it's a bitch to work with: tears easily, hard to seal, etc. I would suggest Sobrbothane sheet, but that's going to be REAL expensive! - Stuart -

Stuart! :yahoo: Hey!

Any chance you could fit two half-doors in there, that meet in the middle, for the second door?

Do you mean something like a french door?

IT would do wonders for the isolation between CR and LR, for sure! Your "single-door" dilemma is only between the CR and the outside world, and has no real effect on the isolation of the LR.

Its mainly isolation to the outside world (sister lives upstairs) that is my main concern. I really am mostly tracking vocals, so losing a bit of isolation between live room and controls is not too much of a concern. I do have drums in there, but rarely if ever record them, just there because my band comes over to jam in that room. I wouldn't mind having 2 doors at the bottom of the stairs if I could fit it. I'll do some measurement and sketchuping to see if this french door thing fits at the bottom of the stairs. Great suggestion Stuart!

Also, I normally have at least three studs on each side of a door frame: Those doors are HEAVY! You need lots of good, rigid support at the back, to keep things straight and plumb. Also use at least three noggins in the first bay out to each side, then two in the next bay, and then down to one for al the others. So instead of being 48" OC (vertically) in the first bay, they will be more like 18" OC, then maybe 24" in the second, etc. Frame the hell out of doorways and windows!.

Gotcha! thanks I was unaware about the extra noggins, thank you!!

I would suggest Sobrbothane sheet, but that's going to be REAL expensive!

I'll look into pricing up Sorbothane - although I don't actually need a lot of it - I guess it sort of depends on how its sold (sheets/rolls?) I'm assuming they don't sell it in 3" wide strips lol. I

Well you got a response from the man, so I'm gonna leave that right there.. :lol: That is a vexing situation though. I feel for ya.... :-?

Stuart! :yahoo: Hey!

It's been a while! Glad to see you back again!! :thu:

Do you mean something like a french door?

That's the general idea, yes.

I really am mostly tracking vocals, so losing a bit of isolation between live room and controls is not too much of a concern.

Not worried about sound from the speakers in the CR getting into the LR mics? :)

I wouldn't mind having 2 doors at the bottom of the stairs if I could fit it. I'll do some measurement and sketchuping to see if this french door thing fits at the bottom of the stairs. Great suggestion Stuart!

:thu: That's what you are paying so much for! Cool ideas like this... :)

I'll look into pricing up Sorbothane - although I don't actually need a lot of it - I guess it sort of depends on how its sold (sheets/rolls?) I'm assuming they don't sell it in 3" wide strips lol.

They sell it in sheets, up to 24" by 24" IIRC, but you can certainly cut it into strips with a sharp knife. But do be prepared for "sticker shock". - Stuart -

Wow - it's been almost a year since my last post! :shock: I have been making a lot of progress with my build - but as usual, it's taking way longer and more expensive than I expected. I sort of ran out of the money I had saved aside for the build, and essentially had to start saving up again (or just spending money as soon as I got it). i did manage to get most of the high price items out of the way (bathroom is finished, A/C Unit is purchased and installed (not connected yet thought). I still have to get doors, glass, fabric, insulation for treatment, TONS still left and money to spend - but at least none of those items cost $3,500 each (I'm looking at you A/C Unit) Aside from that, the weekends are the only time I have to actually work on the build....so its been slow. One major issue is that almost ALL of the progress photos I took with my good camera - are GONE! I let my sister borrow the camera and the SD card went missing so I lost all of my photos :cen: I do have photos I took on my phone but I was mostly documenting the build with the good camera. I guess I haven't had too many particular pressing issues, which is why I haven't been on here as much, but it looks like I am at a point where I will need some advice again soon. I have tons of questions but this post will mainly be a build update from what little photos I do have. I'll try to stay chronological. Framing Control Room Progress: Earlier in the build I had removed some support columns and installed a massive I- Beam to free up floor space. To support the long span of the control room ceiling (and due to the fact i had to run my new CJ's parallel to existing floor joists) - I also had to install (2) smaller I-Beams. So there are (3) I-Beams running down the middle of the control room. The large one is part of the house (and outer leaf) while the (2) smaller ones are not coupled to the outer leaf at all, and are supported from the inner leaf walls. To support the beams I had to install 4x4's directly underneath where the beams would sit in the wall framing, essentially creating these beam pockets. Framing for Beams (4x4's): Smaller Steel Beams (packed out with 2x4's): The ceiling is essentially 2 halfs - the front half is supported by the inner leaf wall in the front of the room (as normal) but the other end of the ceiling rests on this steel beam. The same goes for the back half of the ceiling, one end is supported by the rear wall - the other rests on the beam. The 2x6 joists are tied into the steel beam using joist hangers. Here's what I plan for the finished look of the beams - I had this gap in between (I'm sure I could have used this for acoustic treatment, but I went for aesthetics instead) Gap between beams: I decided to go with some backlighting LED type of thing. Here it is with temporarily testing some LED strips up there so I can get an idea: pretty cool yeah? here's another view of the mostly completed control room ceiling with the steel beams: one interesting thing is that one of the 4x4's meant to support the steel beam - could not be placed directly underneath beam because of the door opening (you can see this on my sketchup) What I needed to do was re-do my door header - and instead of 2x6's with 1/2 plywood in between - I used a 1/2" thick steel plate. So my door header is (2) 2x6's with a steel plate sandwiched in between. Here's a shot of the Booth - shows some progress on the conduits as well: and here is my gf celebrating the conduits being done: Also did the laminate flooring!!!!!! Here's the Air Hanlder (still needs to be connected ducts, refrigerant and electric) only thing done is the hot water coil and that metal base on the bottom with the corcular cut out is a custom piece I had fabricated to support the unit and double as a plenum box (the units inlet is on the bottom) Another big thing i got done was the concrete speaker stands!! this is me sitting on the bottom piece of mdf that will be the speaker boxes. all the holes were lined up with the Sorbothane pads. aaand here is my gf celebrating the concrete stand being done lol: Can anyone confirm if these attached photos are right side up? On my phone there are all correct, on desktop they are not

Ok so it looks like I need to go back and re-do that last post :cen: All my pics got flipped again - I forgot that constantly happens one here. I've run out of time at the moment so I'll have to fix it later. Here is the most recent pic taken just the other day - it wouldn't fit in the last post:

Another big thing i got done was the concrete speaker stands!!

What speakers are you planning to put on those? Something pretty huge, by the looks of it. And massively heavy, too: with seventeen 1" studs, that would be about right for floating a speaker that weighs around 300 pounds, minimum, and perhaps as much as around 1300 pounds, depending on what duro rating they are... I'm fascinated to see what your plans are.

this is me sitting on the bottom piece of mdf that will be the speaker boxes. all the holes were lined up with the Sorbothane pads.

Not sure if I understand you correctly, but if you are saying there will be even more Sorbothane in your system, then be careful with that! If you have rubber pads under the speaker itself inside the enclosure box, and also rubber pads under the enclosure box (on top of your CMU stands), that's the same as a three-leaf system. It can work, but it's much harder to tune, and of course the final resonant frequency is higher than for either the F+ or F-by itself, and higher than what a SDoF system would have been. If that's what you are talking about, then there's some rather complex math needed to figure all of that out. - Stuart -

Stuart!! It's been a while! Great to hear from you! Yes the speakers are extremely large they are Urei 813's. I believe the speakers plus the mdf boxes came to around 520 lbs each. You actually helped me do the calculations on how many of those pads to use. They are Duro 50 and with the 17 pads they are at 22% deflection. There is no additional sorbothane planned in the system, just the pads you see in the photos. The mdf boxes will be built snugly/tightly around the speakers. I was not planning on having any rubber between the actual speaker and the mdf box. I am hoping this is not a mistake, I got the advice to do that from this site as well. Here are some screen grabs from a previous post showing this.

Been reading your thread with interest. Did you ever make a decision on the roller latches for the door? I was considering the exact same thing. I figured two of those, plus the closer should keep the door held snug against the seals. I also need to figure out how to lock my outer door. I'd rather not simply attach a hasp and padlock.

Hey ZSXI! Thanks for checking out the thread!! For the doors I am planning on using the roller latches + auto door closer with a pull bar handle. I have seen the roller latches used before at another studio I work at occasionally and they seem to be okay. Maybe you could use an external deadbolt for your door? It's also not extremely nice looking, but better than a hasp and padlock - they probably make nice-looking ones as well.

actually come to think of it - I think those deadbolts are always installed inside the apartment because the screws are accessible to anyone who may want to break in...... :(

Hmm, that's true. I'm looking into electromagnetic options. It would just have to be "foolproof" in the sense that a person could not become locked in. Also it would need some kind of battery backup so the intruder can't just shut the power off. My breaker panel will be there right next to the door.

Hi, just noticed your thread! It's looking good. You could use a deadbolt with a thumb turn on the inside for your external door. Something like this The thumb turn means you can unlock from the inside without a key, which is required in alot of places for fire safety reasons. Dan

Yes the speakers are extremely large they are Urei 813's. I believe the speakers plus the mdf boxes came to around 520 lbs each. You actually helped me do the calculations on how many of those pads to use. They are Duro 50 and with the 17 pads they are at 22% deflection.

You are so right! Man, that was something like 5 YEARS ago, and I had completely forgotten about that. Yeah, now I remember.

There is no additional sorbothane planned in the system, just the pads you see in the photos.

Hmmm.... Way back then, I did mention to you that there are also lateral forces acting on your speaker: as the cone slams forwards and backwards, moving all that air around, the speaker also wants to slide backwards and forwards: action and reaction. The pads you have are fine for vibration in the vertical direction (up and down), but not so much for the other two directions: side to side, and forwards/backwards. The speaker will be moving and vibrating in all three directions, not just up and down. And since your speaker is large, tall, and top-heavy, it will probably end up "rocking" back and forth a little bit, on top of the pads you have. You should have some method for dealing with the vibrations in those directions too. I have developed a proprietary method for doing that for my clients, when I design their soffits, but that's not something I hand out in public. But it's not hard to figure out: you just need Sorbothane pads on the other 5 sides of your speaker, not just under it. And since those other pads don't have to support the weight of the speaker (just deal with the vibration), you won't need as many of them, and they can be smaller.

The mdf boxes will be built snugly/tightly around the speakers. I was not planning on having any rubber between the actual speaker and the mdf box. I am hoping this is not a mistake, I got the advice to do that from this site as well.

There's two basic methods for soffit-mounting speakers, and you might be confusing them. One method is the way I do it, which completely "floats" the speaker inside the soffit such that it can vibrate freely in all directions without transferring any of that to the soffit structure. The other method (which John prefers) is to hold the speaker so rigidly that it cannot move, and therefore cannot transfer vibrations into the soffit structure. You seem to be combining both into one! But you can't do that... It looks like you might need to update your soffit design a bit... - Stuart -

[quote]There's two basic methods for soffit-mounting speakers, and you might be confusing them. One method is the way I do it, which completely "floats" the speaker inside the soffit such that it can vibrate freely in all directions without transferring any of that to the soffit structure. The other method (which John prefers) is to hold the speaker so rigidly that it cannot move, and therefore cannot transfer vibrations into the soffit structure. You seem to be combining both into one! But you can't do that.../quote] So I was basically planning on the first method you mentioned. The plan was also to have the mdf box rigidly attached to the speakers. However the mdf box AND speaker together is completely "floated" inside the soffit. That mdf box doesn't touch anything except the pads.The only real purpose of the mdf box was so that I did not have to drill holes on the underside actual Urie speakers bottoms. So essentially, the mdf and speakers are vibrating together as one. I understand that speakers are designed a certain way (weights, dimensions, materials, etc..) to achieve a certain sound, and that adding the mdf may effect that design. But I just needed a way to fasten the speakers to the pads underneath. I am hoping that I didn't mess something up with this design. It is definitely not too late to change the design slightly, (i.e. completely eliminate the mdf box, screw a few holes on the underside of the Urei box, and re-calculate the proper amount of sorbothane pads now that it is lighter). However, the blocks are already there, so that part can't really change - and the mdf board is already cut to into pieces ready to become boxes sop that would be sort of a waste of money since I can.t really use it elsewhere. I would assume that with Johns method of mounting a speaker so rigidly that the actual speaker box doesn't move at all, would also have a similar effect as adding weight? For the lateral movement of the speakers, those pads I am using are not just flat pads - they are called stud mounts, and they have a threaded piece sticking out each side maybe 1/2" or so, something like this: This should prevent any lateral movement cause by normal operation of the speaker (vibration). However you are definitely correct that these could be tipped over if you just press on the side. Its something I was planning on being cautious about during the construction of the soffit walls, once the walls are built around the speakers, there will be no access for anyone to be able to push the speaker as it will be inside the wall. I guess someone could technicality push the front of the speaker BACK into the soffit, but I think what would happen there is that before the box could tip over, the top would hit the top of the soffit face. I'm aiming at getting somewhere less than 1/4" between the speaker and the soffit face. You had actually told me to private message you about this proprietary method you are talking about all those years back but you never responded! :( Let me know if you think I'm on the right path or headed to disaster!

The only real purpose of the mdf box was so that I did not have to drill holes on the underside actual Urie speakers bottoms. So essentially, the mdf and speakers are vibrating together as one.

That's fine! Some people do it that way. It also has the advantage of adding mass to the speaker cabinet itself, which is a good thing.

I understand that speakers are designed a certain way (weights, dimensions, materials, etc..) to achieve a certain sound, and that adding the mdf may effect that design.

999 times out of a thousand (invented statistic, but you get the point...), that will IMPROVE the sound. Speaker manufacturers go to great pains to make their cabinets as rigid and massive as they can, but there are practical limits... such as shipping costs, for example: A speaker with a 6" thick concrete case around it would be great, but the shipping might be a little steep. Probably not too many buyers, either: Nobody wants to have to hire Chunk Norris AND Arnold Schwarzenegger, just to lift the speaker out of the box, and onto the desk! (Which then collapses under the weight... :) ) Silly analogy! :oops: Anyway, just wanted to relieve your concerns that adding mass and rigidity to the box might change things in a bad way: it wont. It will either be neutral, or good. I'm betting on "good".

I am hoping that I didn't mess something up with this design.

It's fine! It will work. But I still would suggest considering pads around that, to keep it all happy...

However, the blocks are already there, so that part can't really change - and the mdf board is already cut to into pieces ready to become boxes sop that would be sort of a waste of money since I can.t really use it elsewhere.

The blocks are fine! No problem. Might even be over-kill, but it's a hell of a solid, massive base! There's no need to do anything to that. My concern here is that, with a large powerful speaker like that, there's quite a bit of mass slamming around inside the box, which in turn can potentially cause the box to want to move forwards and backwards on top of the pads. Those Sorbothane studs you have are designed to support the weight of the speaker, acting vertically downwards, and to deal with any vibration in that direction. That's what they are tuned for, and that's what they will do. But if there are lateral forces acting side-to-side, or front-back, those pads are not going to be able to deal with that correctly, because the speaker is so tall. At low volumes, it's not going to be an issue, but when you turn it up to eleven, there's a lot of inertia going on inside, with the woofer mechanism chugging away merrily: action/reaction. There mass moving at high speed, the suddenly reversing direction and going back the other way, then repeating the cycle, ad infinitum. However, since the bottom of the cabinet is restrained by the studs, but the top is free to move, there's a potential for that inertial mass thumping away, to cause the entire speaker to rock back and forth on top of the pads. This might not actually be a real issue, in your case! So don't sweat it too much. Do some testing first, and see if you even have a problem. If you do, then we can figure out solutions. If not, then you can sleep soundly again. So set up one speaker completely, turn it up to eleven, play lots of bass-heavy music, and see if the speaker actually does "rock" at some frequencies. Also run some pure sine test tones through the speaker at high power, and ramp up the frequency slowly, so see if there's any type of strange resonance that might cause it to "rock" at one specific frequency. I don't want to scare you and say that you definitely will have this issue, and it will make your sound terrible, and tear your room apart! I don't like scare-mongering... There's just a potential for this to happen. Your speakers are so massive already that the effect might be negligible. It can be an issue with smaller, light speakers run at high power, but yours might be heavy enough to not even be bothered.

I would assume that with Johns method of mounting a speaker so rigidly that the actual speaker box doesn't move at all, would also have a similar effect as adding weight?

Yes... sort of! But with a speaker that large, it would be an "interesting" exercise... :)

For the lateral movement of the speakers, those pads I am using are not just flat pads - they are called stud mounts, and they have a threaded piece sticking out each side maybe 1/2" or so, something like this:

I'm familiar with those, yes. I have used that exact thing for HVAC compressor isolation mounts, and other things. And I've actually seen one case where the pads worked fine for up-and-down motion of the compressor, isolating perfectly during normal operation, but they were totally shredded and torn to bits, dumping the compressor down onto the mounting brackets, when they failed during start-up, due to the lateral forces acting on them as the compressor spun up to speed... At very low speeds, the compressor speed ramped up through the resonant frequency of the pads, and at that specific frequency there was enough vibration in all directions to rip the Sorbothane to pieces. Not the fault of the rubber, of course! The fault of the design. You should take other precautions if the isolation mounts will ever experience vibration at their natural resonant frequency, due to the amplification of the forces. Now, don't worry! That's NOT going to happen with your speakers! They are not HVAC compressors, and they'll never be producing frequencies in the resonance range, that could provide such destructive vibration. But it does illustrate the point that there are OTHER forces acting on those studs, not just gravity and vertical vibration.

This should prevent any lateral movement cause by normal operation of the speaker (vibration).

Mmmmm.... maybe not! See above.

However you are definitely correct that these could be tipped over if you just press on the side.

Red flag!

once the walls are built around the speakers, there will be no access for anyone to be able to push the speaker as it will be inside the wall.

Maybe people can't get in there, but other forces could... have you ever seen the massive air pressure changes that a large speaker cone can produce inside a box?

I'm aiming at getting somewhere less than 1/4" between the speaker and the soffit face.

That's side-to-side, but what about front-back motion? There's nothing to stop the speaker moving in that direction... and it's quite possible that a real person COULD push on the front face of the speaker, forcing it backwards into the soffit. Either by accident, or on purpose.... I always try to get that gap down to 5mm, then use 6mm high flexibility closed-cell foam all around the edge, to get the air-tight seal. You don't want air huffing and puffing though that gap, as the woofer woofs...

You had actually told me to private message you about this proprietary method you are talking about all those years back but you never responded!

That's weird! I really don't recall seeing that at all! Sorry about that.... Try again, if you feel up to it... :) - Stuart -

Also run some pure sine test tones through the speaker at high power, and ramp up the frequency slowly, so see if there's any type of strange resonance that might cause it to "rock" at one specific frequency.

:shock: :shock: :shock:

I don't want to scare you and say that you definitely will have this issue, and it will make your sound terrible, and tear your room apart! I don't like scare-mongering... There's just a potential for this to happen. Your speakers are so massive already that the effect might be negligible. It can be an issue with smaller, light speakers run at high power, but yours might be heavy enough to not even be bothered.

Attention to every single detail is why I come here. I'll set everything up one one side and run some tests as you mentioned as see how it looks. I'm hoping the fact that I'm using a crossover may help a bit since I'm only sending 80Hz and above to these speakers.

That's weird! I really don't recall seeing that at all! Sorry about that.... Try again, if you feel up to it... :)

No worries, I will def shoot you another message I know you're a busy man Stu!!! I do have one quick question. Should I put this insulation in here or no? It's just 703 - I cut it thin enough to account for the 22% deflection so that the insulation won't be compressed at all. I figured it easier to just do this and take a photo rather than design or describe it - so if it's wrong I can just remove it.