The next step after the new slab goes in will be beefing up the walls and framing out the treatment walls, ceiling, and front wall. I've attached an image of my monitors that I will install in the front wall; they measure 33" wide, 24" high and 14" deep. The two LF drivers are 10". These monitors are incredibly heavy, like trying to lift 4 concrete blocks at once.
Anyway, this got me thinking that not only would it be a good idea to increase the strength of the front wall for obvious reasons but it might also be worth trying to increase the width of the baffles. In my current design, the baffles are 5' wide, which gives only gives 28" baffle extension shared either side of the speaker cabinets.
I was thinking logically that even though it would be impossible to build a truly infinite baffle perhaps the next best thing given the restrictions of the size of my room would be to make the baffles at least as wide as the 1/4 wavelength of the lowest frequency that the speakers can generate. Of course, they will go down to 20hz and perhaps beyond, but they are rated at 38hz - 20khz +-2db, so I'll aim for 38hz. This means the baffles should be about 7.5 feet wide, which is doable with a little tweaking.
My question for you guys is, do you think it's worth it or would my original 5' baffles be more than wide enough? I am aiming for the best that I can achieve, and I know bigger baffles are better, so my gut tells me to go for it, what do you think?
Studio build in Wales, UK...again!
Originally posted at johnlsayers.com, topic 21409.
To answer your question, here is a copy/paste from a post Stuart replied to at one point: 1) The speakers should not go in the corner, nor on the line that divides the corner. In other words, if your walls intersect at 90°, then draw a line out from each corner at 45°, and stay away from that: don't put your speaker exactly on that line, since it implies that you'll be getting the same artifacts from the side walls as from the front wall. Put your speakers either outside or inside of those lines. More commonly you'll want your speakers "inside" those lines (more towards the center line of the room). 2) The "38% of room depth rule" is not a rule, but it is a useful guideline for a starting point. You'll generally want to have your listening position a bit closer to the front wall than that location, but do be aware that you might be getting into problematic SBIR territory there. (You can treat that, to a certain extent). 3) Keep the mix position away from 25% and 50% of room depth, and try to stay between about 32% and 44% 4) You can angle your speakers differently than the "textbook" 30° angle: Anything in the range 25° to about 35° will work well under most circumstances. 5) Keep the speakers as far apart as possible, while not violating rules 1 and 4. 6) Keep the mix position at a good distance from the speakers, within the range of about 1m to about 5m. Further away is usually better. 7) Don't put the speakers at 25% of the room width: that's a modal null for some frequencies, and a peak for others. Try something more like 28% to 34%. 8 ) Make the front baffle of your soffit as wide and tall as you can, within reason. The width should be at least three times the diameter of your low frequency driver. In other words, if you have a speaker with an 8" woofer, then you want the soffit baffle to be at least 24" (60cm) wide. Wider is better. 9) Do not put your speaker in the middle of the soffit baffle: Offset in both directions. In other words, the distances from the acoustic center of the speaker to each edge of the baffle should be very different, by at least 20%. So for example if your speaker axis is 30cm from one side of the baffle, it should be more than 36cm from the other side, less than 24cm from the bottom edge, and more than 44cm from the top edge. (Rough distances, for illustration only...). Larger differences are generally better. 10) Make the baffle as massively heavy as you can, and as rigid as you can. 11) Make the structure inside the soffit (the framing that holds the baffle and speaker in place) as rigid and massive as you can. 12) Mount the speaker inside an enclosure box that is either a very tight fit, in order to keep the speaker rigidly fixed in place, or mount it on suitable rubber pads, to completely decouple it from the the box. Carefully choose the properties and dimensions of that rubber, to make sure the speaker is still decoupled down to at least one octave below the speaker's low cut-off frequency. 13) Take into account that speakers need a lot of space behind them for cooling, and a path through the soffit for cooling air to flow. 14) Rear-ported speakers need special attention: Do not overload the rear port, acoustically, with an enclosure box that is too small, or un-ventilated, or un-damped. 15) Damp the hell out of the soffit interior! Fill it entirely with suitable damping if you want, except for the cooling path. ------- Here are a few questions for you: - what brand and model are those speakers? - what do the dispersion charts look like for them? --> can they be mounted vertically and can that center module be flipped upside down? - are you SURE you want those speakers? I know Stuart hates the NS10's, but with a sub woofer, I love mine. It might be easier to design around and mount those with a removable baffle allowing you to easily change your speakers out in the future. GregMy question for you guys is, do you think it's worth it or would my original 5' baffles be more than wide enough? I am aiming for the best that I can achieve, and I know bigger baffles are better, so my gut tells me to go for it, what do you think?
Hi Greg thanks for your reply. The speakers are made by Quested, they are custom made and yes I will definitely be using them. For what it's worth, I also enjoy using the NS10Ms! But I will not be flush mounting them instead of the Questeds - The Questeds are incredibly honest, clear and flat within +-2db throughout the frequency range. I don't know if you've ever used ATC100SCMs? I've used them extensively and almost got some instead, they are similar to Quested, but the I prefer the Quested. Yes the HF & MF baffle can be rotated, but only 180 degrees, so these speakers need to be installed horizontally. The dispersion is wide, but I do not have charts, off the top of my head the full dispersion is 120 degrees. They also recommend the ears be 80 - 100cm from the tip of the axis crossing, but I may struggle to manage that unless I compromise my RFZ, so I'm aiming for about 60cm. I actually used the same quote from Stuart earlier on in this thread and that is the criteria I've been using throughout my design. I originally decided on 60" for the width of my front baffles based on the 3x LF driver guideline based on Stuart's advice, since I have 2 LF drivers per speaker that would be 60" or 5'. However, Stuart also mentioned that on speakers that have 2 LF drivers far apart (such as mine) the width should be greater, if possible. He also mentions in other threads that he prefers to use the total width of the monitor including the cabinet x3 as a guide, so that would mean my baffles should be 8.25' wide. Now, I could manage that if it was essential, it would just make it a little more challenging. While consulting with another studio designer he mentioned I could base the width of my front baffles on the length of the quarter wavelength of the lowest frequency rated for the monitor, so this is why I am now considering front baffles of 7.5' in length. I know that bigger is better, I am just wondering will it be substantially better if I use a 7.5' (or larger) compared with 5' (or smaller) baffle design? If you look at some rooms designed by John, or Wes, or Tom Hidley you can see that they use baffle designs which are definitely smaller than they should be based on the above criteria. Now, this could be due to room restraints or cost, or other aspects that I don't know about. However, it seems that a lot of them are purposely designed with a smaller baffle, so this leads me to wonder why? These guys all know what they are doing and so they wouldn't have simply overlooked this seemingly vital aspect of the design. Take Wes for example, he's a perfectionist and yet his baffles are more often than not too narrow based on the above criteria even when the rooms are designed from the ground up. Wes uses very large 30-degree soffit wings which are actually side walls, they extend all the way from the edge of the baffles to beyond the ears in the mix position. This is to create a true RFZ design, and if you ray trace one of his rooms you will see how far back the RFZ extends. Perhaps this is the reason the baffles are narrower so that he can accommodate these long, angled side walls, and perhaps that is more important in the overall sound than a wider baffle would be? Thoughts? So I am weighing up larger baffles and a smaller RFZ vs smaller RFZ and larger baffles. Related to this point - are soffit wings considered counting towards the overall width of the baffle extension?To answer your question, here is a copy/paste from a post Stuart replied to at one point: 1) The speakers should not go in the corner, nor on the line that divides the corner. In other words, if your walls intersect at 90°, then draw a line out from each corner at 45°, and stay away from that: don't put your speaker exactly on that line, since it implies that you'll be getting the same artifacts from the side walls as from the front wall. Put your speakers either outside or inside of those lines. More commonly you'll want your speakers "inside" those lines (more towards the center line of the room). 2) The "38% of room depth rule" is not a rule, but it is a useful guideline for a starting point. You'll generally want to have your listening position a bit closer to the front wall than that location, but do be aware that you might be getting into problematic SBIR territory there. (You can treat that, to a certain extent). 3) Keep the mix position away from 25% and 50% of room depth, and try to stay between about 32% and 44% 4) You can angle your speakers differently than the "textbook" 30° angle: Anything in the range 25° to about 35° will work well under most circumstances. 5) Keep the speakers as far apart as possible, while not violating rules 1 and 4. 6) Keep the mix position at a good distance from the speakers, within the range of about 1m to about 5m. Further away is usually better. 7) Don't put the speakers at 25% of the room width: that's a modal null for some frequencies, and a peak for others. Try something more like 28% to 34%. 8 ) Make the front baffle of your soffit as wide and tall as you can, within reason. The width should be at least three times the diameter of your low frequency driver. In other words, if you have a speaker with an 8" woofer, then you want the soffit baffle to be at least 24" (60cm) wide. Wider is better. 9) Do not put your speaker in the middle of the soffit baffle: Offset in both directions. In other words, the distances from the acoustic center of the speaker to each edge of the baffle should be very different, by at least 20%. So for example if your speaker axis is 30cm from one side of the baffle, it should be more than 36cm from the other side, less than 24cm from the bottom edge, and more than 44cm from the top edge. (Rough distances, for illustration only...). Larger differences are generally better. 10) Make the baffle as massively heavy as you can, and as rigid as you can. 11) Make the structure inside the soffit (the framing that holds the baffle and speaker in place) as rigid and massive as you can. 12) Mount the speaker inside an enclosure box that is either a very tight fit, in order to keep the speaker rigidly fixed in place, or mount it on suitable rubber pads, to completely decouple it from the the box. Carefully choose the properties and dimensions of that rubber, to make sure the speaker is still decoupled down to at least one octave below the speaker's low cut-off frequency. 13) Take into account that speakers need a lot of space behind them for cooling, and a path through the soffit for cooling air to flow. 14) Rear-ported speakers need special attention: Do not overload the rear port, acoustically, with an enclosure box that is too small, or un-ventilated, or un-damped. 15) Damp the hell out of the soffit interior! Fill it entirely with suitable damping if you want, except for the cooling path. ------- Here are a few questions for you: - what brand and model are those speakers? - what do the dispersion charts look like for them? --> can they be mounted vertically and can that center module be flipped upside down? - are you SURE you want those speakers? I know Stuart hates the NS10's, but with a sub woofer, I love mine. It might be easier to design around and mount those with a removable baffle allowing you to easily change your speakers out in the future. GregMy question for you guys is, do you think it's worth it or would my original 5' baffles be more than wide enough? I am aiming for the best that I can achieve, and I know bigger baffles are better, so my gut tells me to go for it, what do you think?
What you are actually battling with here, is the baffle step response issue. The "baffle step" refers to the point in the spectrum where the front baffle of your speaker or soffit stops being large with respect to the wavelength. That's the point where the "power imbalance" starts. Above that frequency, all of the energy is projected forwards, "beaming" out in a cone, while below that frequency the wave "wraps around" behind the speaker as well, in a sphere, so half of the energy goes backwards while the other half goes forward. In other words, above the baffle step, all of the POWER goes forward, while below it, only half of the POWER goes forward while the other half goes backward. Thus, there is a power imbalance of 6 dB: the level going forward drops by 6 dB below the baffle step response frequency.
This is why bi-amped speakers generally have much larger amps on the woofer: to make up for the "lost" 6 dB that doesn't go where the power from the tweeter goes. In simpler active, as well as passive, speakers, there's a cross-over that attenuates the highs by 6 dB, to "correct" the power imbalance, and in both cases the amount of power correction can usually be adjusted by a switch or knob, based on the location of the speaker in the room: seldom is the actual final power imbalance as big as the 6dB theoretical, once you take the room into account.
But the "baffle step" is still there in other ways too! It's not just power imbalance (which can be corrected). There's also the issue of edge diffraction, SBIR and other problems, all of which are related to the dimensions of the speaker cabinet or the soffit. And therefore are also related to the "baffle step response".
Given the "baffle STEP" name, you'd think that if you look at a graph of the speaker response, there's a sudden sharp "step" in the power curve, exactly where the wavelength coincides with the width of the cabinet. But that's far from the truth! In reality, there's a gentle curve that covers the 6 dB range, with the center point of that curve being at the "baffle step" frequency. The range of the curve covers two octaves each way (so four octaves in total). The frequency at the center point of that curve is at 115824/W, where W is the width of the baffle in millimeters (or f=4560/W where the width is in inches). That's the point where it is 3 dB down from the pure "beaming" level, and 3 dB up from the pure "wrap around" behavior.
But that equation only applies to the speaker when it is tested in a true free field! In other words, no room around it, or in an anechoic chamber. the REAL response in a real-world room will never be a perfect "6dB-drop-over-four-octaves" curve, since the room itself affects the response. However, what's important about that equation is that it still does mark the center frequency of the region where all of the baffle-related problems occur! It's not important to know if the power imbalance is 2dB or 6 dB, or 3.78516 dB, or whatever. What's important is WHERE the change takes place, because that also marks the point where all the other problems occur too.
And that brings us to the purpose of the soffit: it isn't magic. All it does is to move that dreaded "baffle step" point down to a lower frequency: Ideally, it would move it off the bottom end of the scale completely, so low that it is totally outside of the audible range. But in reality, you'd need a HUGE room to do that... so big that it would sound bad in numerous other ways, and also be absolutely impractical. Do the math: to get the baffle step response mid point down to 5 Hz (two octaves below 20 Hz, so no part of the curve is in the audible spectrum), you'd need a baffle that is 1140 inches wide! :shock: So, each of your baffles would need to be 95 feet wide, plus a decent area between them... implying a room about 250 feet wide, and therefore about 400 feet long, and maybe 300 feet high... just a little large for a typical home studio, perhaps! Doesn't quite fit in the average garage or basement... or 747 hanger, either!
In other words, no matter what we do in room design, it will be a big compromise with respect to theoretical perfection. But it's not as bad as you'd think. Your current speakers are 33" wide, implying a baffle step response of 138 Hz, so the effect extends upwards to 552 Hz and downwards to 34 Hz. If you make your soffit baffles 6 feet wide, then the baffle step point would be at 63 Hz, with the curve rising up to 250 Hz, and falling down to 16 Hz. So it would still be twice as good as it is at present, since it lower the point by more than an octave.
If you did go to 7' 6", then you'd get the mid point at 51 Hz, top end at 202 Hz, bottom point at 13 Hz.
If you go to 8' 3" wide, then you'd have 46 Hz mid point, 184 Hz top, 12 Hz bottom.
But, as I've said before, it's not just the power imbalance that we are interested in! That can easily be adjusted electronically, so it isn't even an issue, really. What matters a lot more, is the other effects: SBIR, edge diffraction, etc. You are ALSO driving those down the spectrum, and in fact eliminating some of them entirely, if you design your baffle correctly.
The reason I recommend 3x speaker width (plus speaker), is because it will drop the baffle step by two octaves! That's all. Plain and simple. It's not a magic number. Nothing esoteric here. For most small speakers, that puts the baffle step end point way below the bottom end anyway, and the mid point far down. If you can only go 2x speaker width, that doesn't mean it wont work! It just means your baffle step only went down a bit more htan one octave which is still pretty good, and very useful.
Well... that's another approach, a different "rule of thumb", but I prefer to use the actual equation for baffle step response.While consulting with another studio designer he mentioned I could base the width of my front baffles on the length of the quarter wavelength of the lowest frequency rated for the monitor,
Like I said: there's no way that you could possibly build a truly complete baffle that pushes the entire curve off the low end, so anything that anyone does is compromise! It really is that simple.If you look at some rooms designed by John, or Wes, or Tom Hidley you can see that they use baffle designs which are definitely smaller than they should be based on the above criteria.
Right! Studio design is nothing more than juggling an never-ending series of compromises, to compromise the compromises with the other compromises, and arrive at the best compromise of compromises, ... hopefully.Now, this could be due to room restraints or cost, or other aspects that I don't know about.
See above: it is impossible to make it "big enough", ever, no matter what you do, so make it as big as practical, then do other things to the room to reduce the effects of the "imperfect compromises".However, it seems that a lot of them are purposely designed with a smaller baffle, so this leads me to wonder why?
Not really! you missed out on the key point here...and yet his baffles are more often than not too narrow based on the above criteria
Bingo! :) There you have your answer.... Those wings ARE the baffle! They extend the baffle. There's no law that says the baffle has to be flat forever, out to infinity...uses very large 30-degree soffit wings which are actually side walls, they extend all the way from the edge of the baffles to beyond the ears in the mix position.
Partly, yes, but they are ALSO integral to the soffits... and therefore are part of the baffle. Measure those TOGETHER WITH the actual "baffle", then do the above calculations, to see why those rooms sound so good. I do the exact same thing in all of my rooms: Take a look at the corner control room thread, and you'll see that, in reality, the soffits extend all the way to the rear walls! The sliding glass doors on each side of his room are part of the baffle too!... it's not just the actual baffle that you see around the speaker itself. That's a small room, so I used every trick in the book to force the response to where I wanted it. If you check that thread soon, over the next few days, we'll be posting the final REW graphs, showing the end outcome after everything we did, and I'll challenge you to find any trace of the baffle step response, or SBIR, or edge difraction on those graphs! :)This is to create a true RFZ design,
That's part of it, sort of, but the baffles are not really "narrower" at all, when you consider that the wings ARE the baffle as well... Make the actual speaker baffle as big as it can be, reasonably, then AT THE SAME TIME shape the RFZ with the wings to be as big as it can be.... the resolve the conflict that these two approaches will create, by blending the soffit into the wings, even if that means reducing the apparent width of the "baffle" itself. But do be careful with all this: you are also creating an inverse wave-guide shape like that, so you need to take care with that too... And don't forget vertical: your ceiling is also part of this whole deal, and so is your cloud... assuming it is hard-backed.... (I seem to be giving away all my secrets today... it must be Christmas or something! :) ) - Stuart -Perhaps this is the reason the baffles are narrower so that he can accommodate these long, angled side walls,
Wow, that's what I call an answer to a question! Thank-you for my early Christmas present Stuart, very generous of you :D I now know not only the 'how' but also the 'why' behind determining the widths of baffles, which is something I had found...well, baffling... for a while. If you don't mind, I am in need of a couple of clarifications... - In regards to the soffit wings also being part of the baffle, surely the middle section between the two 'actual baffles' would also be considered part of the baffle? So, really half of the middle section, the part around the speaker itself plus the wing would all make up one 'infinite' baffle per speaker? In that case, the baffle could end up being very wide indeed, thus lowering that baffle step considerably. I must ask then, at what point does a baffle stop being a baffle and simply a side wall? What I mean is, if there's nothing to say a baffle must be continuously flat forever then surely a side wall should be considered part of the baffle?...if it were hard and rigid...but then I suppose that may cause unwanted reflections depending on the angle of those side walls. - Regarding offsetting the speaker in the baffle by at least 5/8 or 2/5 or 20% I am assuming this applies only to the 'actual' baffle around the speaker itself? Otherwise, surely the soffit wing would induce this offset automatically? Now, assuming it does only apply to the 'actual' baffle, is there a preferred wider and narrower side or is it not important? For example, should the speaker be offset closer to the soffit wing, or closer to the middle section? I see most of the time the speaker is closer to the middle section as opposed to the soffit wing, is there a reason for this? The only reason I can think of is if a wider and longer spread is wanted then the speaker should be closer to the soffit wing, and vice versa, but is there a more important reason for doing so that I am not aware of? - Lastly, I think it's important to mention that my monitors are actually tri-amped. I have an active crossover unit and 3 power amps, the HF and MF drivers have their own channels and the LF drivers share a channel per monitor. So that will help to balance the power once I figure out how to set it properly. PaulWhat you are actually battling with here, is the baffle step response issue. The "baffle step" refers to the point in the spectrum where the front baffle of your speaker or soffit stops being large with respect to the wavelength. That's the point where the "power imbalance" starts. Above that frequency, all of the energy is projected forwards, "beaming" out in a cone, while below that frequency the wave "wraps around" behind the speaker as well, in a sphere, so half of the energy goes backwards while the other half goes forward. In other words, above the baffle step, all of the POWER goes forward, while below it, only half of the POWER goes forward while the other half goes backward. Thus, there is a power imbalance of 6 dB: the level going forward drops by 6 dB below the baffle step response frequency. This is why bi-amped speakers generally have much larger amps on the woofer: to make up for the "lost" 6 dB that doesn't go where the power from the tweeter goes. In simpler active, as well as passive, speakers, there's a cross-over that attenuates the highs by 6 dB, to "correct" the power imbalance, and in both cases the amount of power correction can usually be adjusted by a switch or knob, based on the location of the speaker in the room: seldom is the actual final power imbalance as big as the 6dB theoretical, once you take the room into account. But the "baffle step" is still there in other ways too! It's not just power imbalance (which can be corrected). There's also the issue of edge diffraction, SBIR and other problems, all of which are related to the dimensions of the speaker cabinet or the soffit. And therefore are also related to the "baffle step response". Given the "baffle STEP" name, you'd think that if you look at a graph of the speaker response, there's a sudden sharp "step" in the power curve, exactly where the wavelength coincides with the width of the cabinet. But that's far from the truth! In reality, there's a gentle curve that covers the 6 dB range, with the center point of that curve being at the "baffle step" frequency. The range of the curve covers two octaves each way (so four octaves in total). The frequency at the center point of that curve is at 115824/W, where W is the width of the baffle in millimeters (or f=4560/W where the width is in inches). That's the point where it is 3 dB down from the pure "beaming" level, and 3 dB up from the pure "wrap around" behavior. But that equation only applies to the speaker when it is tested in a true free field! In other words, no room around it, or in an anechoic chamber. the REAL response in a real-world room will never be a perfect "6dB-drop-over-four-octaves" curve, since the room itself affects the response. However, what's important about that equation is that it still does mark the center frequency of the region where all of the baffle-related problems occur! It's not important to know if the power imbalance is 2dB or 6 dB, or 3.78516 dB, or whatever. What's important is WHERE the change takes place, because that also marks the point where all the other problems occur too. And that brings us to the purpose of the soffit: it isn't magic. All it does is to move that dreaded "baffle step" point down to a lower frequency: Ideally, it would move it off the bottom end of the scale completely, so low that it is totally outside of the audible range. But in reality, you'd need a HUGE room to do that... so big that it would sound bad in numerous other ways, and also be absolutely impractical. Do the math: to get the baffle step response mid point down to 5 Hz (two octaves below 20 Hz, so no part of the curve is in the audible spectrum), you'd need a baffle that is 1140 inches wide! :shock: So, each of your baffles would need to be 95 feet wide, plus a decent area between them... implying a room about 250 feet wide, and therefore about 400 feet long, and maybe 300 feet high... just a little large for a typical home studio, perhaps! Doesn't quite fit in the average garage or basement... or 747 hanger, either! In other words, no matter what we do in room design, it will be a big compromise with respect to theoretical perfection. But it's not as bad as you'd think. Your current speakers are 33" wide, implying a baffle step response of 138 Hz, so the effect extends upwards to 552 Hz and downwards to 34 Hz. If you make your soffit baffles 6 feet wide, then the baffle step point would be at 63 Hz, with the curve rising up to 250 Hz, and falling down to 16 Hz. So it would still be twice as good as it is at present, since it lower the point by more than an octave. If you did go to 7' 6", then you'd get the mid point at 51 Hz, top end at 202 Hz, bottom point at 13 Hz. If you go to 8' 3" wide, then you'd have 46 Hz mid point, 184 Hz top, 12 Hz bottom. But, as I've said before, it's not just the power imbalance that we are interested in! That can easily be adjusted electronically, so it isn't even an issue, really. What matters a lot more, is the other effects: SBIR, edge diffraction, etc. You are ALSO driving those down the spectrum, and in fact eliminating some of them entirely, if you design your baffle correctly. The reason I recommend 3x speaker width (plus speaker), is because it will drop the baffle step by two octaves! That's all. Plain and simple. It's not a magic number. Nothing esoteric here. For most small speakers, that puts the baffle step end point way below the bottom end anyway, and the mid point far down. If you can only go 2x speaker width, that doesn't mean it wont work! It just means your baffle step only went down a bit more htan one octave which is still pretty good, and very useful.Well... that's another approach, a different "rule of thumb", but I prefer to use the actual equation for baffle step response.While consulting with another studio designer he mentioned I could base the width of my front baffles on the length of the quarter wavelength of the lowest frequency rated for the monitor,Like I said: there's no way that you could possibly build a truly complete baffle that pushes the entire curve off the low end, so anything that anyone does is compromise! It really is that simple.If you look at some rooms designed by John, or Wes, or Tom Hidley you can see that they use baffle designs which are definitely smaller than they should be based on the above criteria.Right! Studio design is nothing more than juggling an never-ending series of compromises, to compromise the compromises with the other compromises, and arrive at the best compromise of compromises, ... hopefully.Now, this could be due to room restraints or cost, or other aspects that I don't know about.See above: it is impossible to make it "big enough", ever, no matter what you do, so make it as big as practical, then do other things to the room to reduce the effects of the "imperfect compromises".However, it seems that a lot of them are purposely designed with a smaller baffle, so this leads me to wonder why?Not really! you missed out on the key point here...and yet his baffles are more often than not too narrow based on the above criteriaBingo! :) There you have your answer.... Those wings ARE the baffle! They extend the baffle. There's no law that says the baffle has to be flat forever, out to infinity...uses very large 30-degree soffit wings which are actually side walls, they extend all the way from the edge of the baffles to beyond the ears in the mix position.Partly, yes, but they are ALSO integral to the soffits... and therefore are part of the baffle. Measure those TOGETHER WITH the actual "baffle", then do the above calculations, to see why those rooms sound so good. I do the exact same thing in all of my rooms: Take a look at the corner control room thread, and you'll see that, in reality, the soffits extend all the way to the rear walls! The sliding glass doors on each side of his room are part of the baffle too!... it's not just the actual baffle that you see around the speaker itself. That's a small room, so I used every trick in the book to force the response to where I wanted it. If you check that thread soon, over the next few days, we'll be posting the final REW graphs, showing the end outcome after everything we did, and I'll challenge you to find any trace of the baffle step response, or SBIR, or edge difraction on those graphs! :)This is to create a true RFZ design,That's part of it, sort of, but the baffles are not really "narrower" at all, when you consider that the wings ARE the baffle as well... Make the actual speaker baffle as big as it can be, reasonably, then AT THE SAME TIME shape the RFZ with the wings to be as big as it can be.... the resolve the conflict that these two approaches will create, by blending the soffit into the wings, even if that means reducing the apparent width of the "baffle" itself. But do be careful with all this: you are also creating an inverse wave-guide shape like that, so you need to take care with that too... And don't forget vertical: your ceiling is also part of this whole deal, and so is your cloud... assuming it is hard-backed.... (I seem to be giving away all my secrets today... it must be Christmas or something! :) ) - Stuart -Perhaps this is the reason the baffles are narrower so that he can accommodate these long, angled side walls,
That's the most important point! If you know the "why", then you can make more intelligent decisions about your build, rather than just following a recipe blindly.I now know not only the 'how' but also the 'why' behind determining the widths of baffles,
Exactly! That's why you see the entire front end of many studios as one solid surface, wall-to-wall. So in fact, the left soffit is also part of the right soffit, to a certain extent. I have my reasons for sometimes breaking that continuity a bit with the center section, recessing it a bit (as you can see in Steve's room for example), but it's still a solid surface... sort of! :) (not all my secrets!).surely the middle section between the two 'actual baffles' would also be considered part of the baffle?
If you build it as one complete, unbroken surface, then you can also include the opposite soffit, and the opposite wing... :)So, really half of the middle section, the part around the speaker itself plus the wing would all make up one 'infinite' baffle per speaker?
Yup!In that case, the baffle could end up being very wide indeed, thus lowering that baffle step considerably.
As soon as it stops being a baffle! :) Sounds cryptic, but it's that simple. As soon as there is a major discontinuity in it, such as a large change in angle, or a break, or an absorption panel, or a diffuser, or a slot wall, or anything else where the surface is no longer contiguous solid, massive, and rigid. Of course, the further you get away from the speaker, the lower the effect is, since air attenuates sound anyway, plus we are talking about wavefronts that are expanding hemispherically (into half space) with the accompanying decrease in amplitude with distance, plus the grazing angle (from one point of view, the wave-front is going out at 90°, directly across the surface of the baffle), plus the impedance issue, plus a whole bunch of other things... So there really isn't much point in trying to make a 20-foot wide baffle, even if you could.I must ask then, at what point does a baffle stop being a baffle and simply a side wall?
As long as there is no large change n angle or other discontinuity between the baffle and the wall, yes. If there's a sudden change in direction (eg, a 90° corner, or even a 45° angle), then that's a different story. Take a close look at the room above: there's only a small change in angle between the soffit baffle itself, and the sliding glass doors... it's only 9° different, so not really an issue. But I would not consider the rear wall part of the baffle, since there's a 96° angle back there. No large changes in continuity. But there's another issue here to complicate your calculations: Sound is 3D, not 2D, and the baffle step response also happens in the vertical direction, not just horizontal! And it's the SHORTEST dimension that sets the actual response. So even if you could make your baffle 20 feet wide, you can't make it 20 feet tall! However tall it is, that's what sets the stage here. And while you might be able to angle your side walls in slight increments to increase the apparent width of the baffle, it's hard to do that with the floor! :) Your speakers are maybe 4 feet above the floor, and perhaps 5 or 6 feet below the ceiling, if you are lucky, and the floor and ceiling are usually at very large angles to the baffle: typically 90°. So you definitely have baffle-step issue in the vertical direction, even though you might have "eliminated" it in the horizontal direction. In other words, there's not really much benefit to making your baffle a whole lot wider than your floor-to-ceiling height. There's certainly no harm in doing that, and it can have otter positive benefits, but it's not going to gain you a lot, from the point of view of baffle step response. Still very good for edge diffraction, SBIR, and other phase related issues, but not a huge effect on baffle step.... and once again, baffle step can be corrected easily, electronically.What I mean is, if there's nothing to say a baffle must be continuously flat forever then surely a side wall should be considered part of the baffle?
Yup... compromises, compromises, juggle, juggle....but then I suppose that may cause unwanted reflections depending on the angle of those side walls.
Right. Because it is that immediate hard, flat surface that can cause some types of "lobing". Once again, it's not a huge issue, but still worth dealing with. And once again, sound is 3D, not 2D, so off-centering the vertical direction is important too.- Regarding offsetting the speaker in the baffle by at least 5/8 or 2/5 or 20% I am assuming this applies only to the 'actual' baffle around the speaker itself?
That is usually dictated by the room geometry: where the mix position is, the angles, distances, etc. Whichever way works out better for the speaker/listening position geometry is what you want.is there a preferred wider and narrower side or is it not important? For example, should the speaker be offset closer to the soffit wing, or closer to the middle section?
Yup! :) See above: room geometry. You'll usually find that if you move them outwards, they'll be too far apart to aim at the mix position, without having to put a very large angle on the soffit, which also has it's consequences. And that "20%" rule is not written in stone either! If you have to move the speaker a bit right or left to make things fit, that's fine.... compromises, compromises, juggle, juggle.... 8)but is there a more important reason for doing so that I am not aware of?
That's part of the final room tuning process. It's great that you have them on separate amps, as that gives you more flexibility in tuning, but it also multiplies the complications.... Not trying to scare you, but tuning three-way crossovers and three amps on each side, is very complicated! Not for the feint of heart... It's hard enough to do it with just a pair of active speakers and a sub... - Stuart -- Lastly, I think it's important to mention that my monitors are actually tri-amped. I have an active crossover unit and 3 power amps, 1 separate amp channel per driver. So that will help to balance the power once I figure out how to set it properly.
Okay, got it! Thanks a lot for clearing that up for me, I’ll tweak my current design with those thoughts in mind and see if I can get my baffles. On a different note, I was thinking today that I could potentially use 12mm cement fiber boards on the outside of my OSB layer which is battling the weather though it is holding up well the cemboard would also be offset to the seams of the osb layer, rather than beef up my osb internally. The weight of the cemboards are about 14kg/m2 as opposed to the drywall which is about 12, but I was going to install 2 beef up layers of drywall as opposed to just one layer of cemboard. The cemboard is about twice the price of the drywall but I would have the advantage of not having to cut in between the studs, it would protect my osb layer and I could always install 1 beef up layer of drywall internally if I needed to. My question is, has anyone used the cemboard externally without a top layer of siding? If I paint the cemboard with a weatherproofing paint and seal all of the joints before hand then I believe it will withstand the rain.That's the most important point! If you know the "why", then you can make more intelligent decisions about your build, rather than just following a recipe blindly.I now know not only the 'how' but also the 'why' behind determining the widths of baffles,Exactly! That's why you see the entire front end of many studios as one solid surface, wall-to-wall. So in fact, the left soffit is also part of the right soffit, to a certain extent. I have my reasons for sometimes breaking that continuity a bit with the center section, recessing it a bit (as you can see in Steve's room), but it's still a solid surface... sort of! :) (not all my secrets!).surely the middle section between the two 'actual baffles' would also be considered part of the baffle?If you build it as one complete, unbroken surface, then you can also include the opposite soffit, and the opposite wing... :)So, really half of the middle section, the part around the speaker itself plus the wing would all make up one 'infinite' baffle per speaker?Yup!In that case, the baffle could end up being very wide indeed, thus lowering that baffle step considerably.As soon as it stops being a baffle! :) Sounds cryptic, but it's that simple. As soon as there is a major discontinuity in it, such as a large change in angle, or a break, or an absorption panel, or a diffuser, or a slot wall, or anything else where the surface is no longer contiguous solid, massive, and rigid. Of course, the further you get away from the speaker, the lower the effect is, since air attenuates sound anyway, plus we are talking about wavefronts that are expanding hemispherically (into half space) with the accompanying decrease in amplitude with distance, plus the grazing angle (from one point of view, the wave-front is going out at 90°, directly across the surface of the baffle), plus the impedance issue, plus a whole bunch of other things... So there really isn't much point in trying to make a 20-foot wide baffle, even if you could.I must ask then, at what point does a baffle stop being a baffle and simply a side wall?As long as there is no large change n angle or other discontinuity between the baffle and the wall, yes. If there's a sudden change in direction (eg, a 90° corner, or even a 45° angle), then that's a different story. Take a close look at that room above: there's only a small change in angle between the soffit baffle itself, and the sliding glass doors... it's only 9° different, so not really an issue. But I would not consider the rear wall part of the baffle, since there's a 96° angle back there. No large changes in continuity. But there's another issue here to complicate your calculations: Sound is 3D, not 2D, and the baffle step response also happens in the vertical direction, not just horizontal! And it's the SHORTEST dimension that sets the actual response. So even if you could make your baffle 20 feet wide, you can't make it 20 feet tall! However tall it is, that's what sets the stage here. And while you might be able to angle your side walls in slight increments to increase the apparent width of the baffle, it's hard to do that with the floor! :) Your speakers are maybe 4 feet above the floor, and perhaps 5 or 6 feet below the ceiling, if you are lucky, and the floor and ceiling are usually at very large angles to the baffle: typically 90°. So you definitely have baffle-step issue in the vertical direction, even though you might have "eliminated" it in the horizontal direction. In other words, there's not really much benefit to making your baffle a whole lot wider than your floor-to-ceiling height. There's certainly no harm in doing that, and it can have otter positive benefits, but it's not going to gain you a lot, from the point of view of baffle step response. Still very good for edge diffraction, SBIR, and other phase related issues, but not a huge effect on baffle step.... and once again, baffle step can be corrected easily, electronically.What I mean is, if there's nothing to say a baffle must be continuously flat forever then surely a side wall should be considered part of the baffle?Yup... compromises, compromises, juggle, juggle....but then I suppose that may cause unwanted reflections depending on the angle of those side walls.Right. Because it is that immediate hard, flat surface that can cause some types of "lobing". Once again, it's not a huge issue, but still worth dealing with. And once again, sound is 3D, not 2D, so off-centering the vertical direction is important too.- Regarding offsetting the speaker in the baffle by at least 5/8 or 2/5 or 20% I am assuming this applies only to the 'actual' baffle around the speaker itself?That is usually dictated by the room geometry: where the mix position is, the angles, distances, etc. Whichever way works out better for the speaker/listening position geometry is what you want.is there a preferred wider and narrower side or is it not important? For example, should the speaker be offset closer to the soffit wing, or closer to the middle section?Yup! :) See above: room geometry. You'll usually find that if you move them outwards, they'll be too far apart to aim at the mix position, without having to put a very large angle on the soffit, which also has it's consequences. And that "20%" rule is not written in stone either! If you have to move the speaker a bit right or left to make things fit, that's fine.... compromises, compromises, juggle, juggle.... 8)but is there a more important reason for doing so that I am not aware of?That's part of the final room tuning process. It's great that you have them on separate amps, as that gives you more flexibility in tuning, but it also multiplies the complications.... Not trying to scare you, but tuning three-way crossovers and three amps on each side, is very complicated! Not for the feint of heart... It's hard enough to do it with just a pair of active speakers and a sub... - Stuart -- Lastly, I think it's important to mention that my monitors are actually tri-amped. I have an active crossover unit and 3 power amps, 1 separate amp channel per driver. So that will help to balance the power once I figure out how to set it properly.
I have another related question, I've used the search function but cannot find exactly what I'm looking for:
Would a beefed up wall perform slightly worse/better/the same as a conventional wall of the same materials?
E.g.
2x 5/8" drywall - 3/4" OSB - studs
VS
3/4" OSB - studs - 2x 5/8" drywall between studs
The beefed up wall would have less mass due to the studs breaking up the drywall, and the drywall panels would be smaller which would make their resonance higher too, correct? However, the drywall pieces would be less rigidly secured to the frame which would have more of a dampening effect, correct?
I am just guessing here but would love to know the answer!
I haven't and am not sure how the board would hold up without siding.My question is, has anyone used the cemboard externally without a top layer of siding? If I paint the cemboard with a weatherproofing paint and seal all of the joints before hand then I believe it will withstand the rain.
I think you answered your own question here: ---Conventional--- Pros: - Easy to build. - Larger gap between leaves. Cons: - Fixing the layers of sheathing requires a typical screw schedule which means the green glue effects are hindered. - Unless you have the ability to add this mass during initial construction, it is probably impossible to add mass this way. ---Beefed Up--- Pros: - The added drywall is pretty much floating on green glue which maximizes it's effect - It allows us to "easily" add mass to completed construction. - With several stages of caulking, it's pretty much guaranteed to not have any voids! Cons: - Time consuming, annoying, expensive (backer rod/caulk). - More material (cleats, backer rod, caulk.) - The surface density of the studs at the equivalent depth of the beef up drywall is the weak link here. So, in conclusion, this is bringing up a good point regarding the lack of mass at the studs. Off the top of my head, I think dimensional lumber is about half the mass of drywall. So, I wonder if we should be running full lengths of 1.5" thick cleat along the stud/joist and drywall joint. Thanks for pointing this out. GregWould a beefed up wall perform slightly worse/better/the same as a conventional wall of the same materials?
Thanks Greg, you’ve confirmed my thinking. If I do decide to beef up instead of use cement board then that’s exactly what I will do anyway, use a baton that frames the entire bay, nailed to the stud and seal behind and around. I saw this done on a build that Rod consulted and designed over at dark pine studios. After talking to max the owner he confirmed excellent results using this method. It also guarantees you have a solid seal at the weakest points of the wall.I haven't and am not sure how the board would hold up without siding.My question is, has anyone used the cemboard externally without a top layer of siding? If I paint the cemboard with a weatherproofing paint and seal all of the joints before hand then I believe it will withstand the rain.I think you answered your own question here: ---Conventional--- Pros: - Easy to build. - Larger gap between leaves. Cons: - Fixing the layers of sheathing requires a typical screw schedule which means the green glue effects are hindered. - Unless you have the ability to add this mass during initial construction, it is probably impossible to add mass this way. ---Beefed Up--- Pros: - The added drywall is pretty much floating on green glue which maximizes it's effect - It allows us to "easily" add mass to completed construction. - With several stages of caulking, it's pretty much guaranteed to not have any voids! Cons: - Time consuming, annoying, expensive (backer rod/caulk). - More material (cleats, backer rod, caulk.) - The surface density of the studs at the equivalent depth of the beef up drywall is the weak link here. So, in conclusion, this is bringing up a good point regarding the lack of mass at the studs. Off the top of my head, I think dimensional lumber is about half the mass of drywall. So, I wonder if we should be running full lengths of 1.5" thick cleat along the stud/joist and drywall joint. Thanks for pointing this out. GregWould a beefed up wall perform slightly worse/better/the same as a conventional wall of the same materials?
Your other comments are spot on, but this is one that comes up occasionally, and needs clarifying. The absolute density if drywall is around 680 kg/m3 (give or take a big margin), so the SURFACE density of a 5/8" panel, which is 16mm thick (roughly) is about 680 x 0.016 = 10.88 kg/m2. Call it 11 kg/m2 for simplicity. So if you have three layers of drywall as your leaf, then that would be about 33 kg/m2. The absolute density of typical wood studs is around 750 kg/m3 and a 2x4 stud is 89mm thick (3 1/2"), so the SURFACE density of that stud, seen edge on, is 750 x 0.089 = 66.75 kg/m2. Call it 66 for simplicity. In other words, your average stud has the same surface density as SIX layers of 5/8" drywall. :shock: :!: Surprising, but true. So, if you have the situation of a strange wall, where there's two layers of 5/8" on the studs all across the wall, plus another two layers of "beef up" in between the studs, then for the parts of the leaf of the stud bays, in between the studs, you have four layers = 44 kg/m2, and for the parts over the studs you only have two layers (22 kg/m2), but you also have the stud itself, which is equivalent to 6 layers (66 kg/m2), so you actually have EIGHT layers where the studs are, or 88 kg/m2. So the parts where the studs are is TWICE as good as the bays between the studs. So in reality, the studs are not the wink link in the wall: they are the STRONG link in the wall: the "weak link" is the part where there is only drywall with no studs behind it, even though there's 4 layers of drywall there.... Yet another of the very many non-intuitive things about designing and building studios.... And to add another interesting fact to the mix: the density of caulk is around 1600 kg/m2, a bit more than twice the density of drywall, so you only really need to have half the thickness of each sheet of drywall caulked to get the SAME surface density.... which is why it is fine to have backer rod in half the depth of the joints, and the other half filled with caulk. Or you can fill the complete depth with caulk if you feel like it, in which case your joints are TWICE as dense as your drywall leaf... and that's a good thing! (This only applies to colored caulk: clear caulk is less dense, since it has no pigments, and the pigments provide a lot of the mass [about 40%]... so only use black, gray, white, or colored caulk for sealing your joints, not clear caulk....) - Stuart -- The surface density of the studs at the equivalent depth of the beef up drywall is the weak link here.
Thanks for clarifying this! For some reason I thought they were half that of drywall. Another value to add to the vault! GregThe absolute density of typical wood studs is around 750 kg/m3
It depends on the species of wood, of course: Poplar is around 520, while oak is around 850. Spruce is 450. Pine is anywhere between 400 and 700. Maple is around 750. Hardboard is more like 1000, and balsa is around 170. A very broad range. I use 700 for "generic" wood where I live, but for the USA it would probably be better to go a bit lower: call it 600, to be safe.
- Stuart -
So if I’ve understood correctly, a beefed up wall will perform better than a conventionally built wall the same materials, despite the sheets being cut smaller to fit between the studs even at low frequencies? For some reason I thought the resonance would be higher if the sheets were made smaller (say 2’ wide x 8’ long vs 4’ wide x 8’ long).
If that’s the case then would it be fair to say that it’s ALWAYS preferable to build the walls in a beefed up manner if time and expense is not an issue?
You are thinking of the natural resonant frequency of a panel in a free field. That is not related to the MSM resonance of the wall. The only factors that affect the MSM resonance of the wall, are: 1) the surface densities of the two leaves; 2) the depth of the air cavity between them, and 3) the damping (insulation) in that air cavity.For some reason I thought the resonance would be higher if the sheets were made smaller (say 2’ wide x 8’ long vs 4’ wide x 8’ long).
Sort of but not really! There's no free lunch. If you add layers of drywall between the studs, then you are also reducing the depth of the air cavity between the leaves.... - Stuart -If that’s the case then would it be fair to say that it’s ALWAYS preferable to build the walls in a beefed up manner if time and expense is not an issue?
Ah I see! Okay that makes sense now. Regarding reducing the air space between the two leaves - apart from in the case of an inside out wall where you would be increasing the space between the leaves. Yes the internal room size would be decreased slightly, but if it is a new build and you have already designed it with that in mind then it seems like a good thing to do. Thank you Greg and StuartYou are thinking of the natural resonant frequency of a panel in a free field. That is not related to the MSM resonance of the wall. The only factors that affect the MSM resonance of the wall, are: 1) the surface densities of the two leaves; 2) the depth of the air cavity between them, and 3) the damping (insulation) in that air cavity.For some reason I thought the resonance would be higher if the sheets were made smaller (say 2’ wide x 8’ long vs 4’ wide x 8’ long).Sort of but not really! There's no free lunch. If you add layers of drywall between the studs, then you are also reducing the depth of the air cavity between the leaves.... - Stuart -If that’s the case then would it be fair to say that it’s ALWAYS preferable to build the walls in a beefed up manner if time and expense is not an issue?
Hey Guys, hope you all had a great Christmas and enjoying the holidays!
I have a question about the best way to implement inside out ceiling modules.
I understand the framing - a strong skeleton is made from the joists (or in my case, the rafters) with 2x8, 2x10 or even 2x12 (depending on span) then the modules made from 2x4 frames are inserted into the bays. My question is concerning the layers; if on a beefed up wall the drywall layers should not be screwed directly to the OSB but held in with cleats, then is the same not true for the ceiling modules?
If using cleats also applies to the ceiling modules then how does one do it with more than one layer of drywall without the first layer falling down? I can imagine managing to use cleats with a single drywall layer - the frame which has OSB attached to the back would be installed into the bay first, then the drywall would be propped up in place and sealed around the perimeter and then the cleats are screwed into the frame to press the drywall layer up against the OSB. But trying to do that with 2 layers would not only be a nightmare but also even more dangerous.
If we are not concerned with using a cleat system for the ceiling modules and we simply screw the drywall to the backside of the OSB, and then lift the modules into place, then why bother using cleats on the walls? One could simply screw the drywall to the OSB around the perimeter of the bays.
What's the answer?
Paul
After writing my last post, I realised there's a simple (if not a little tedious) way to do it (see image)
This could be done either by building separate modules or by building it straight into the bays between the rafters/joists.
Paul
You seem to be missing the point of inside-out ceilings! You build the modules ON THE FLOOR!...
So, you make a frame from 2x4's laying down on the floor, then you put as many layers of OSB, MDF, drywall, or whatever else you feel like using ON TOP OF that frame while it is STILL SITTING ON THE FLOOR, then you raise the entire module up through the joist backbone, and bolt / nail / screw it in place.
Simple!
- Stuart -
I understand that perfectly well Stuart, if you re-read my post (the one before last) you will see what I'm asking. I was asking in my post about fixing the drywall layers. It is advised on a beefed up wall NOT to screw the drywall directly to the OSB (or whatever that wall is made from) - so why would this not also be true for the ceiling? If you make modules then you are cutting down big sheets of drywall into smaller sections and then fixing those directly to the supporting structure - so what's the difference? Why would it apply to walls but not ceilings?...You seem to be missing the point of inside-out ceilings! You build the modules ON THE FLOOR!... So, you make a frame from 2x4's laying down on the floor, then you put as many layers of OSB, MDF, drywall, or whatever else you feel like using ON TOP OF that frame while it is STILL SITTING ON THE FLOOR, then you raise the entire module up through the joist backbone, and bolt / nail / screw it in place. Simple! - Stuart -
I don't understand your reasoning for wanting to build like that, when it is so much easier to build the normal way. Maybe you could explain WHY you want to beef up between the joists, instead of just putting the drywall on top.
- Stuart -
I'm sorry for not explaining this very well Stuart, let's see if I can clear up what I mean... I agree it is much easier, just as it would be much easier to screw the drywall directly to the OSB or outer most layer of any wall that you want to beef up rather than use cleats, and yet that is not recommended. The reason being, as far as I can remember is that it is better to not have a rigid connection between the layers. There's quite a few threads where you mention this is a big no no. I am just wondering why it is okay for a ceiling but not a wall. If you build modules, then all of the layers will be connected together rigidly to the module frame. So why is that not a big no no? Remember, I am building my inner leaf first, and my inner leaf is also inside out, which means my inner ceiling is also my temporary roof at the moment. This means my outer most OSB layer is already in situ, with felt on top of it, all supported by the rafters, ridge and walls. I cannot put drywall layers on top of that, but I can still build modules in the normal way and insert them between my rafters. Or I can use cleats if it is better. PaulI don't understand your reasoning for wanting to build like that, when it is so much easier to build the normal way. Maybe you could explain WHY you want to beef up between the joists, instead of just putting the drywall on top. - Stuart -
I'm still not understanding your reasoning, and I think you still are not understanding the way an inside-out ceiling is supposed to be built, normally.
You start with the inner-leaf walls:
Then you put up the backbone and nothing else....
Then you build the module down on the ground, starting with just a 2x4 frame:
Then you put the layers of sheathing ON TOP OF the frame: ALL of the layers:
(In this case, there's a layer of OSB first, then two layers of drywall)
Each layer is nailed into the frame exactly the same as for a normal ceiling, or a normal wall: The nails go through into the joists, around the perimeter, but NOT in the field. Nobody is saying that you have to nail or screw the drywall into the OSB, in the field between the framing! You ONLY nail (or screw) the drywall around the edges, exactly as you would for any wall, or for a normal ceiling.
Then you raise the modules up into place, between the backbone members:
The above is shown without the rim boards in place, for clarity. Here's how it will actually appear with the rim boards:
And that's it!
There is no need to beef-up from below, which is what you are showing in your diagram!
If your modules are already in place, then take them down, put the drywall on top, and raise them again. You can set them at whatever height you need within the backbone such that you get enough clearance on top, between this leaf and the outer-leaf.
No they will not, if you build them correctly! They will be built exactly the same as any other ceiling, with the layers of drywall all nailed into the FRAME, and NOT nailed of screwed in the field between framing members.If you build modules, then all of the layers will be connected together rigidly to the module frame
Right! So after you get your outer-leaf on, then you will take down those inner-leaf modules, rework them with drywall on top, then raise them up again.This means my outer most OSB layer is already in situ,
Fine! Then do that! Take down your temporary "ceiling/roof" once you get the final outer-leaf roof in place, then build your modules in the normal way (see above), and raise them into place. Building a studio is already complicated enough: there's no need to complicate it even more unnecessarily, by beefing up modules from below when it would be so much easier to just take them down and rebuild them properly. - Stuart -but I can still build modules in the normal way and insert them between my rafters.
Thanks Stuart, I completely understand how the modules are supposed to be constructed, and your descriptions and images confirmed that. The question I had was about the best way to fix the layers to the frame. you answered the question by pointing out that the panels are fastened to the frame and not in the field, which I was also aware of, however, I wrongly thought that it would be undesireable due to the panels being cut down smaller and therefore stiffer, rather than in a normal wall where the panels are larger and have more flex. Clearly this doesn’t matter in this case. Though I still have not quite managed to convey how my structure is built at present, i got the answer I needed! Just for future clarification: I do not have any ceiling modules in place, I simply have a frame with rafters and a ridge and walls. The osb is fixed to the outside of the entire frame including the roof. That osb is my roof, which is felted. PaulI'm still not understanding your reasoning, and I think you still are not understanding the way an inside-out ceiling is supposed to be built, normally. You start with the inner-leaf walls: Then you put up the backbone and nothing else.... Then you build the module down on the ground, starting with just a 2x4 frame: Then you put the layers of sheathing ON TOP OF the frame: ALL of the layers: (In this case, there's a layer of OSB first, then two layers of drywall) Each layer is nailed into the frame exactly the same as for a normal ceiling, or a normal wall: The nails go through into the joists, around the perimeter, but NOT in the field. Nobody is saying that you have to nail or screw the drywall into the OSB, in the field between the framing! You ONLY nail (or screw) the drywall around the edges, exactly as you would for any wall, or for a normal ceiling. Then you raise the modules up into place, between the backbone members: The above is shown without the rim boards in place, for clarity. Here's how it will actually appear with the rim boards: And that's it! There is no need to beef-up from below, which is what you are showing in your diagram! If your modules are already in place, then take them down, put the drywall on top, and raise them again. You can set them at whatever height you need within the backbone such that you get enough clearance on top, between this leaf and the outer-leaf.No they will not, if you build them correctly! They will be built exactly the same as any other ceiling, with the layers of drywall all nailed into the FRAME, and NOT nailed of screwed in the field between framing members.If you build modules, then all of the layers will be connected together rigidly to the module frameRight! So after you get your outer-leaf on, then you will take down those inner-leaf modules, rework them with drywall on top, then raise them up again.This means my outer most OSB layer is already in situ,Fine! Then do that! Take down your temporary "ceiling/roof" once you get the final outer-leaf roof in place, then build your modules in the normal way (see above), and raise them into place. Building a studio is already complicated enough: there's no need to complicate it even more unnecessarily, by beefing up modules from below when it would be so much easier to just take them down and rebuild them properly. - Stuart -but I can still build modules in the normal way and insert them between my rafters.
It's about time I got round to designing my HVAC system properly.
I've been putting it off because I lack so much understanding on the subject, there's a fair amount of threads that cover this subject but either the info is conflicting or the math just goes right over my head, I am a mere simpleton when it comes to this. So this is going to be a real challenge for me and I need to ask you guys for a lot of help as well as patience.
For now, let's just concentrate on the control room ventilation until I have grasped the basics:
I'll have a mini-split AC unit and I would like to install an HRV for ventilation, which will be located in my lobby. The outer leaf of my control room will make up one of the walls to this lobby. I would then have a silencer box for the supply and return going in and out of the control room. The ducting and silencer boxes for my inner leaf are going to be inside my room, hidden within soffits or in the ceiling space. My inner leaf has a vaulted ceiling where I am going to install hangers and other treatment which will all be covered with fabric and possibly an angled cloud. So there's plenty of space up there for the ducting. The silencer boxes can go high up on my gable end within a soffit or hidden amongst the treatment there and the plan is to have the 2 boxes basically on top of each other, with neoprene in between them, supported on top of the framing of my hanger trap on the rear wall.
Now I have a few questions:
1. I've drawn up some ideas for the control room, blue being my supply of fresh air and red being my returns. Would some of these ideas work? If so, which of these locations would be best for my return ducts?
2. I would like to have 2 supply and 2 return ducts so I've designed a silencer box that splits into 2. I've drawn up what I had in mind, would something like this work well?
3. I know I need a silencer box for both the supply and return on both leaves, (4 boxes) but do I also need a box for each vent?
4. Do the silencer boxes need to have the same equivalent amount of mass as my walls?
5. I am thinking I should use flex duct in the cavity between my 2 leaves, to join between the outer and inner silencer boxes, and then could I use round PVC pipe for the ducting inside the room?
Once I've figured this out I'll need to ask how to work out what size ducting I need as well as the size of the boxes themselves. Now I'm off to learn more about HRVs and how much air needs to be supplied to my room...
Paul