Questions about using Glass Sliding Doors (CR to ISO)

I have a few quick questions regarding the possible use of dual sliding glass doors between a CR and adjacent ISO booths. I 'm a novice in the midst of the research and design phase of new studio in Montreal. The budget is very tight, and now I am focusing in on the door and window requirements for our draft floorplans. After reading many many threads here, and looking at Mr. Sayers' superb floorplans and completed studios, I often see symetically placed sets of dual sliding glass doors used for access and visibility between the CR and iso booths located on both sides of the CR. While glass sliders are not a mandatory feature in our proposed floorplan, they would certainly be preferred (over dual solid doors and windows), but only if we could still achieve acceptably good isolation. In my part of Canada, neither contractors nor building supply companies have been able to provide us with any real acoustic performance data on the vast majority of their sliding glass door products. Even their manufacturers' websites don't seem to offer much in the way of data. I realize that if I had the money, I would certainly order specially designed "Acoustic Sliding Glass Doors" with proven STC specs, but I just don't have a high enough budget for those at this stage. I realize that a wall's isolation ability is only as good as it's weakest point! My questions are simply...... What is the approx. STC rating of dual generic sliding glass doors?? Will dual sets of off-the-shelve (Home Depot or similiar) patio style sliding glass doors (angeled apart!), acoustically sealed within dual steel framed high STC "double" walls, be sufficient to effectively block sonic leakage (drums, guitar amps, vocals) from adjacent non-floated ISO booths? Are there any specific features or suggested minimum glass/frame specs that I should look for when shopping for these sliding glass doors? Is there perhaps any method of modifying or improving these off-the-shelve sliders or their components for improved results?? Anyone out there happen to know a source in Canada for higher rated STC sliding glass doors at somewhat reasonable prices?? Ron Montreal, CANADA

Well, I guess the first question is this- how much isolation are you going to need? In defense of sliding glass patio doors, bear this in mind- while they haven't been designed to stop sound from passing thru, they have been designed to keep AIR from passing thru. The attention to detail to keep their thermal performance as high as possible will help a little bit with their sonic properties. When companies make a high-quality sliding door or window, the attention to detail goes into the air-tight seal around the edges- which is just where you want it. Obviously, having a specialty acoustic door would be better. But any company that makes an acoustic door is probably NOT going to make it a slider. So back to the original question. Yes, the doors will be the weakest point. But will they be strong enough for you? I mean, isolation between control and tracking rooms is important, but having more isolation than a pair of sliding glass doors (installed properly) isnt usually necessary. Having isolation from the outside world is usually much more critical- but you probably won't have sliding glass doors on your outside walls. Its just one of the choices you'll have to make in your design. If you think you need more isolation than a slider will give you, then make them swing doors. This may not have helped you do much but think... but that's the intention. You've asked us a question we can't really answer for you.

Thanks Dymaxian, Your comments are very helpful, and may help lead me to answer my own questions. One manufacturer, Anderson Windows, sent me an Email yesterday with some good basic data for their sliding glass doors. It seems that their standard Series 200 and Series 400 PVC enclosed double pane glass patio doors have ratings of between 22 and 31 STC. Assuming I find a local manufacturer with similiar specs on their sliding glass doors, and we properly install & seal them into each of the adjacent (double) wall frames, I now suspect they will offer enough isolation bewteen the CR and the adjacent iso booths on both sides. I would still appreciate any hints or suggestions on how to modify the doors, seals or tracks in order to improve their actual STC capabilities, and also invite any suggestions as far as other brands or specifications or special features that we should look for when selecting these patio door units (Argon gas?, special lamination?, TRUTH rollers?, minimum glass specs?). - RON Montreal

Travelreview wrote:

One manufacturer, Anderson Windows, sent me an Email yesterday with some good basic data for their sliding glass doors. It seems that their standard Series 200 and Series 400 PVC enclosed double pane glass patio doors have ratings of between 22 and 31 STC.

Yup, they sure will - but for your purposes that is just about useless. 1st - STC ratings are basically in the area of the human voice - and are useless for the purposes of determining low frequency isolation. You will be luck to get any isolation at all below 500hz...... 2nd - putting in 2 of them is not going to double the numbers........ in fact - you will be luck if you get even an additional 4 or 5 db in reduction. The problem being that adding the additional door (under the best conditions) NEVER doubles the isolation - the next being that you will in fact be creating a 4 leaf system - and the location of those 2 innner leafs actually lowers your STC rating compared to the same mass on the outside faces.

Assuming I find a local manufacturer with similiar specs on their sliding glass doors, and we properly install & seal them into each of the adjacent (double) wall frames, I now suspect they will offer enough isolation bewteen the CR and the adjacent iso booths on both sides.

Ron, not by a near shot........... Picture a singer - putting out somewhere around 95db (and that's not pushing his/her vocal chords) - your 27db reduction is going to leave you with 68db bleeding into your room... that's above the level of a normal conversation taking place....... Personally I wouldn't go to this place........... Rod

In what little research I've started and asking questions to window people, is that windows (such as sliding windows or thermal pane type of house windows), if you get the one's filled w/ Argon gas, it apparently helps to reduce sound. So I've been told...whether this is true or not...??? Aaron

Thanks to all of you that helped me decide not to use the proposed sliding glass door between the CR and adjacent ISO areas. Based on the straight-forward advice of Mr. Rod Gervais, I have decided to alter our draft floorplans and forget about using patio doors alltogether. I have yet not done all the research, but perhaps using double solid core wood doors and building adjacent double 3' x 4' laminated glass windows of differing thickness and angle would be a better way to achive both access as well as visability between the CR and the ISOs and Live Room. The only other idea I have would be using double commercial steel doors with massive glass inserts, but I suspect that they may not assure enough isolation and TL. As far as the Argon gas helping any reduce sound leakage, I don't have any real answers, but the Argon filled patio doors that I finally got specs on only had 2 db higher STC spec listed above an almost identical door from the same local manufacturer. Seems like rather a small increase for the 25% higher cost. Any comments or suggestions are always welcome! Ron Charles Montreal

Ron, You really won't gain anything with commercial steel doors......... in fact - they are generally not as good at the lower frequencies than solid core wood doors. (unless you are speaking professional quality isolating doors at 3 grand a pop) Here's a detail I have used in professional studios - one door - don't need the 2nd one with this system - and they work just fine. A bit more expensive than just a standard solid core door - but a hell of a lot less money than professional quality doors......

Thanks so much Mr. Gervais, I will be utilizing your superb CR door solution once I have a chance to source the parts needed and have my contractor look it over. I have just posted a new draft floorplan on the design forum for the newly located 4400 sq. ft. raw space I wish to rent beginning September. I am sure my novice design has plenty of errors in both form and function, but at least it's a starting point. I am always looking for better ideas from those of you that have much more knowledge and experience than me! Please feel free (if you have the time!) to offer any suggestions or advice on my new draft studio floorplan (NOW POSTED AT... http://www.johnlsayers.com/phpBB2/viewtopic.php?t=1840 ) As usual, I would certainly appreciate any and all advice as to corrections and modifications and redesigns that may assist in creating a better recording environment. I have about 2 months to get this design complete and begin a month or so of construction using a licenced contractor and our own slave labour. Thanks in advance for your help and advice.... Ron Charles Montreal, CANADA [removed]

hey all, just my 2 cents, and i hate when it goes against the stream here but.... I have put sliding doors in the last three rooms I have built. i use Pella Doors from home Depot. Double insulated. I install two at an angle. I have not had one problem or one client wish I had put in a real solid core door system. The last studio was a drum iso room off the control room. With a full on session (Hard Rock) yes you can hear the drums if you turn down the monitors all the way. And yes only monitoring at 85db you can not hear anything. I have been so happy with the results, I no longer even consider using the more labor intense Solid Core Door system. You can not have a conversation with someone on the other side of the glass, You can not hear a singer, you can not hear a guitar cab unless on about 8. Bass, there is a little bleed, about the same as the drums coming through. And on drums, you really only hear the kick and snare. no hats, cymbols, or toms. Each of us look for our best solution. this is mine. maybe you want total isolation, but I have worked in some pretty big facilities with pretty big doors and had the same isolation properties. so, once again, this is my 2 cents and what has worked for me. jai

Aaronw wrote:

In what little research I've started and asking questions to window people, is that windows (such as sliding windows or thermal pane type of house windows), if you get the one's filled w/ Argon gas, it apparently helps to reduce sound. So I've been told...whether this is true or not...??? Aaron

Hello Aaron, Just info: No it doesn't really. It changes the TL curve gaining somewhat in mid and highs but makes the mass-spring more explicit. This means that it in fact for music it's worse. A general problem of all pre-made double glazing is the small cavity. Kind regards Eric

Hi all, Two months ago I installed the Pella doors that are available from Menards, Lowes, and Home Depot. The doors were installed with the method that John Sayers recommended, and Michael Jones gave me some very good tips on the "area between the 2 doors". I along with EVERYBODY that has been at my studio throughout the construction, have been IMPRESSED and AMAZED as to how well the doors have worked!! And, just a quick note to all at these "studio forums". Read, read, ask questions, and read some more. My studio is working out FAR better that I had thought. ALL this is due to the experience, guidance and help from Eric, S. Foster, Steve(knightfly), Rod and John. Thanks to ALL!!! Tom Durso First Bass Audio

Thank you for clearing that up for me Eric. Now I know. :) Thanks, Aaron

Just as another example, I know of a fellow with an Home Theatre who built a doorway with sliding glass doors and wooden french doors behind them. At least part of his motivation was aesthetics, and the fact that due to some steps blocking he was unable to have a normal hinged door so he needed a sliding one. I understand that the isolation he gets with the sliding glass doors is unexpectidly more than sufficient for his needs and he never closes the french doors. I've asked him to perform a TL loss test, but he hasn't done it yet.

I'm using a "commerical" sliding glass door (ie. STC like and other testing that keep water (read air) from entering). 3/8", air, then 1/4" laminated glass as I recall (handle different frequencies). I overlapped the inside molding around the door by [1-1/2"] to block light on the top and sides.

Here is a link to the picture http://www.avsforum.com/avs-vb/attachme ... fullpage=1 And a link to text with the link to the picture: http://www.avsforum.com/avs-vb/showthre ... ost3167490 But of course, without multi-frequency TL numbers, and a description of what his 'needs' are -- i.e. does everyone within 1km of the home enter the Home Theatre while it's playing -- this is just a photograph.

I found this quote, but I'll be hanged if I can find the "method that John Sayers recommended", and I really can't figure out how to construct these sliders from Michael's short description. I've done the search and read the posts...does anyone recall any posts with a little more detail? I also remember seeing a drawing. Thanks for the help. Phil

fbars wrote:

Hi all, Two months ago I installed the Pella doors that are available from Menards, Lowes, and Home Depot. The doors were installed with the method that John Sayers recommended, and Michael Jones gave me some very good tips on the "area between the 2 doors". I along with EVERYBODY that has been at my studio throughout the construction, have been IMPRESSED and AMAZED as to how well the doors have worked!! And, just a quick note to all at these "studio forums". Read, read, ask questions, and read some more. My studio is working out FAR better that I had thought. ALL this is due to the experience, guidance and help from Eric, S. Foster, Steve(knightfly), Rod and John. Thanks to ALL!!! Tom Durso First Bass Audio

http://www.johnlsayers.com/phpBB2/viewt ... ght=#11495 http://www.johnlsayers.com/phpBB2/viewt ... ight=#8632 These are the two threads I found on doors with comments from Michael, not sure where else to look... Steve

Mr. Desart, I am very curious about what you said about the Argon. Can you explain a little more? Like Ron said, I too have been convinced that Argon makes a better sound insulation. Perhaps I have the physics wrong. In the information (perhaps misleading?) I've gathered, the isolation works like this (I am explaining the very basics for those who do not know about the details): The perfect barrier against sound penetration is a vaccuum, since no air molecules can bounce around from one glass plate to the next. But a vaccuum suffers from air pressure trying to break in all the time; eventually, the window will spring a leak and air will get in there. Filling the void with Argon (as I understood it), is similar to a vaccuum effect because Argon molecules are NOT elastic in their interactive properties, as oxygen clearly is. Consequent to this would be a non-interactive (inert) gas between the plates, serving to increase isolation, as well as prevent air from breaking in. It sounded almost as if you were hinting that Argon is more elastic than air? Will you elaborate? Thanks, Eric Bragg

Some puzzlement and some cost comparisons. Most inexpensive sliding glass doors have tempered glass...2 layers of glass with an air space. In another post, it was stated that installing 2 of them would constitute a 4-leaf system. Is that really true? Is there enough air space in there to make that a true statement? If so, it would seem that unless you have an enormous budget, sliding glass doors are out of the question. The cheapest laminated sliding glass door I can find is $1400 plus shipping. The manufacturere says: just put that at an angle to a regular 2-pane sliding glass door. Doesn't that constitute a 3-leaf system? This is driving me a little buggy. Any help is appreciated. Phil

$1400????? Where are you looking? You can get an Anderson one for around $500.

I'd love it if that were the case. Can you give me a link to a place that provides a SINGLE GLASS PANE in an Anderson sliding door? Anderson doors here at Home Depot cost $700, and they ALL have double panes. I've been looking for weeks...all single panes are special order and really expensive. Maybe the doors you use have double panes and work well? That's really what I'm trying to find out. Most all posters on this forum have said that by using 2 double-pane sliding glass doors, you loose some STC, especially in lower frequencies.

Home Depot has them. Anderson Narrowline and Perma-Sheild series. Even the Frenchwood series is under $1000. The most expensive doors I found are Pella. I have found a number of sliding glass doors at my local home stores like HD, Lowes, etc under $1000 with dual panes.

Right...those are also the ones available here. The point of my post is that this forum consistently says: "DOUBLE PANE BAD...SINGLE PANE GOOD." All of those doors you mentioned are double pane. Do you get good results using double pane doors? I've been led to believe by this forum that doubling up double pane windows is a bad idea.

I'm going to stick my neck out here. I believe the moderators may not agree, but here's what I understand about 3+ layer boundaries: 1) Certainly, for a given density, if you can push all the mass into the outermost boundaries, and make the innermost boundary as light as possible, you have the best results. This is because reflection happens when a wavefront, traversing a material of given density, strikes a boundary of a different density, some of the energy penetrates, some reflects. The amount of reflected energy depends upon the differenc in mass between the two materials. Concrete and air are VERY diverse in density, so whether the wave was originally in air, or originally in concrete, at the boundary, most of the energy is reflected. 2) If you have 3 massive leaves, especially the same thicknesses and separated by the same distance, most of the energy that penetrates the first two leaves is going to be of a certain set of frequency and energy characteristics. As it so happens, the 3rd leaf, being equidistant and equal mass and width serves to filter exactly the same frequencies as the first two leaves. Therfore, those breakthrough wavefronts now striking that third surface will no more be stopped by the next layer. Common sense tells you that SOME energy HAS to be lost in the third leaf; however, because of the particular size and rigidity, the third boundary will resonate at the same frequency as the first two, and the airspace between, being the same depth, acting as an identicle plenum, ALSO traps most strongly every odd multiple of 1/4 wavelength. I.e. 1/4, 3/4, 1-1/4, 1-3/4, etc. [With insulation in those cavities, the plenum effect is flattened, meaning that the 1/4 wavelength is trapped less completely, but the surrounding frequencies are better filtered. This is the same as lowering the 'Q' setting on an E.Q.] So most of the energy passing through the first pair of leaves will also penetrate the third. 3) If the characteristics of the inner layer are different than the outer layers, and if the distance between the layers is offset, I dare say that the loss will be much stronger, yes, even in the third layered system. One example is an inner layer which is more resilient than the outer layers. This inner layer will serve to block transmission AND move along with the wavefront, thereby dissipating some of the energy as heat. 4) The very outer layers should be the most dense. They should also be different thicknesses. Again, this is because they will each resonate at different frequencies as a result: which frequencies one layer cannot block, the other (hopefully) will. Also, the widest gap between these two boundaries allows for blockage of lower frequencies - the wider, the better. 5) In this case, you have glass. Mass manufacturers build most doors with two glass panes, the same thickness, and they are practically right next to each other. If you removed one pane, you will probably not notice much of a difference, because of the tiny space, and both glass panes are parallel (I believe this was Eric Desart's hottest point). However, that doesn't mean that if you put that pane back in, you'd get an overall gain in noise! That's not what he said. He said the EFFECT is different, because it is likely that the gas particles inside will literally be excited by certain frequencies (lower ones), and MAY even transmit them better. In fact, most frequencies will be blocked more, but the overall effect is not much improvement .... there IS more mass, so there WILL be more overall frequency loss. If you were to REPLACE the ONE piece of glass with one twice as thick, THEN you've made better progress. Or you can remove one of these panes and replace it with plexiglas, which is less dense, but has different frequency characteristics and is ... resilient. I wouldn't claim this will get you the amount of gain worth the effort, but it would be worth a lab test (if anybody knows of one). 6) If you are looking for lowest cost and easiest application, you MAY consider getting the double paned stuff at a certain thickness and as a whole, consider this as one boundary. Then get another mass-produced door, double paned, but at a different glass thickness and at a different spacing (which may or may not make any difference in this case, because the spacing is so darned close). Then install these two doors at an angle such that the glass panes between the doors are not parallel. 7) Probably, the biggest challenge is going to be preventing leakage around the edge of these movable doors. I think THIS will be a bigger problem, really, than how much energy you can stop by the glass.

Carl, Thanks very much for that thoughtful answer, and for taking the time. Makes a lot of sense to me. I can get a Jen-Weld sliding door for $375. Then, maybe use one of the more expensive Anderson doors if the glass is thicker. I'm also having a local glass shop give me a quote on a laminated sliding glass door. My setup is such that it's much easier to have a door between the CR and the recording room, and we can certainly baffle off the louder sound sources if the sliding doors don't do all that I expect. I just didn't want to spend $2800 for a pair of them and get mediocre results, so this helps a lot. Best, Phil

Gentlemen, I would call your attention back to the transmission loss page here - http://www.domesticsoundproofing.co.uk/tloss.htm specifically the 40 and 63 dB partitions, again - I know the distances are not the same as far as between the two pairs of leaves, left and right; still, the frequencies that would be least controlled are governed by the m-a-m resonance (and somewhat the critical frequencies) of each pair of leaves in a 4-leaf boundary, right? In the case of a 6mm glass pair, separated by 10 mm air space, the m-a-m resonance for a 1meter x 2 meter panel is around 219 hZ, with its critical frequency @ 2200 - this means that those two frequencies are the weaker points in general. The TL curve for the above glass pair is already weak at its resonance, which is right there in "drum territory" - if you put a second double leaf in that's near that frequency, you have even weaker TL in that range, and when you COMBINE that condition with marginal seals (which will ALSO manifest as a loss of TL at LOW frequencies more than mids/highs) I personally see it as asking for trouble. Outa time, I'll think about this more in the absence of Eric's availabilit... Steve

Nice website referral, Steve. There's a book I'm looking at called, "Noise Control for Engineers" (Lord Gatley Evensen) which I used way back in college. It's got the same diagram for transmission loss in panels. The lower 1/3 frequencies (resonance controlled) were also referred to as "Region 1" frequencies by acoustic engineers. Mass controlled were referred to as "Region 2", and coincidence controlled as "Region 3". I have a note in the book from the professor's declaration that this diagram is a bit outdated. Apparently, as of 1995, anyway, there were 5 frequency regions, each needing separate treatment. The link below is from that data, in layman's terms (without all the calculus). It seems to go well with what you just explained. Only trouble is, I have no access to any new diagram, just text, which I suppose doesn't present much more (if any) new information. It's less spectacular without all the math! The rest of the information in the link you provided is the pretty much the same as what I have. www.FountainSquareHouse.com/FreqClass.html