Coytee Posted January 4, 2007 Share Posted January 4, 2007 I know that somewhere is the golden rule of room dimensions. What I'm further wondering about is a bit more detail. If the room is for example 15x20x9 (just making up for a reference point since I don't know the golden rules) My understanding is, you don't want parallel walls/ceiling. Would it be sufficient to taper the side walls say 12" over the course of the 15'? (15' in front and 14' in back) Would a 6" taper be suffient to keep the parallel issues at bay? How dramatic must you taper to eliminate any issues? For the ceiling, would a 12" slope be enough over the distance of the room? Why I'm asking... Talked to wife last night and she's looking to do some redesigns of our existing house. I said wasn't too interested in that, but if she wanted to start some blueprint ideas for a NEXT house, I might talk. If this were to happen, then I'd have the proverbial "clean sheet" to start with and could make the room any dimension/shape I want so I'm looking for some simple ideas that won't cost anything, yet might contribute greatly to minimizing issues. In a perfect world, envision building the room for 5 Khorns (or cough, Jubilees) 3 across the front, 2 on rear. The two in front, doubling for 2-ch duty. What are some built in enhancements you can do to the room at the initial construction phase? Quote Link to comment Share on other sites More sharing options...
damonrpayne Posted January 4, 2007 Share Posted January 4, 2007 High ceilings are nice, the golden mean ratios are based on a multiple of the ceiling height. I believe the golden means are rooms likely to give you an even distribution of room modes based on the standard room mode calculations. Non paralell walls are ideal but I chose not to do that in my room to make it easier for me to build. Quote Link to comment Share on other sites More sharing options...
Coytee Posted January 4, 2007 Author Share Posted January 4, 2007 Building an uneven room would come pretty natural to me! [] Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 4, 2007 Share Posted January 4, 2007 lol I believe the rule of thumb is 1 inch for every foot. So a room that is 15 feet long will be 30 inches narrower in the front (15 inches from each side wall). The ceiling will be 15" shorter. The ceiling works out well because you'll usually have a second row of elevated seating in a dedicated room. If you take a look at some studios, you'll notice that the front part of the walls are splayed even more...usually to allow the speaker to be flushmounted and aimed directly at the main listening position. I'm not sure how that would work out with the Jubilee / KHorn. For the front center, I would build out a false wall so that it can be flush mounted behind the screen. Will you be considering the option of a subwoofer? When you splay the walls you often end up with some free unused space behind the wall - which would make for a killer "Infinite Baffle". I know you're satisfied with the Jubilee bass response, but the costs for such a design would be minimal. For oh about $3k your Jubes would be panting to keep up [] Flushmounting the equipment rack in the false wall is also a very clean looking thing to do. And if you build out the wall far enough, then you'll have room to access everything from the rear too. This is extremely important for the tweeker / lazy person. Along those lines, another thing I've seen done is to have all the walls be "modular panels" in that any section of wall can easily be removed and replaced with another panel. So instead of painted drywall, it's usually fabric covered boards with a few screws for mounting. I've only seen it twice and it was done in low lit environments. It gave a column feeling to all the walls and made changing things behind the wall incredibly easier. It also makes acoustical treatment easier to experiment with too. I'm not sure what the cost differences were though - but to make it look as good as it did had to be expensive. I think it looks cooler than normal painted drywall though - and it doesn't have the same distracting reflection sheen issues when watching movies. Of course, it makes the room look like a dedicated HT - not sure if that's the look you're going for or not. Quote Link to comment Share on other sites More sharing options...
damonrpayne Posted January 4, 2007 Share Posted January 4, 2007 I second the value of the rear-accessible equipment rack. Not only to aid laziness and tweaking, but sometimes you have to be an acrobat with super-wrist-strength to plug in stubborn RCA cables. Quote Link to comment Share on other sites More sharing options...
gaspr Posted January 4, 2007 Share Posted January 4, 2007 If you are really serious about this, why not talk to some experts.... like maybe the Russ Berger Design Group. Edit...I messed up the link somehow...www.rbdg.com Quote Link to comment Share on other sites More sharing options...
Hemihorn Posted January 4, 2007 Share Posted January 4, 2007 This site is a wealth of good information it also has a room calculator. If you need any more information post again I have a ton of Acoustics Information I will reply. http://www.ethanwiner.com/acoustics.html Quote Link to comment Share on other sites More sharing options...
justin_tx_16 Posted January 5, 2007 Share Posted January 5, 2007 This might also be helpful. http://www.soundwise.org/gethelp/peaksnulls.htm Quote Link to comment Share on other sites More sharing options...
mas Posted January 5, 2007 Share Posted January 5, 2007 Richard, Splaying the walls outward and the ceiling upwards as they extend from front to back is a very good idea. I would suggest an average angle of each wall to be ~5-7 degrees - an easily achieved goal (and one that will be hardly noticeable - in fact, after the room is outfitted with furniture, etc., you may have to point the fact out). And as Doc mentioned, 1" per running foot is a good rule of thumb.The usefulness of the splaying is to minimize the flutter echo that results in reinforced reflections between parallel surfaces. Splaying, while an important feature, will not address room modes (except to make the simple room mode calculator programs even more inaccurate)! You will still need to treat the room modes with bass traps below 200-300Hz. This is true of ANY room. Controlling the LF energy is the first order of business, followed then by the control of reflections. I would recommend measurements be used to design/tune the treatment. Additionally, if you are in the planning and building phase, it is rather easy to incorporate Helmholtz resonator bass traps into the wall junctions and corners based upon measurements so that you actually address the real as opposed to the imagined problems. PM me and I will explain a bit more (and this time I promise to focus on the issue and not get off onto ETn 'folklore'!!! [^o)]) I guess I need to get busy with the Small Room Acoustics thread... Quote Link to comment Share on other sites More sharing options...
Coytee Posted January 5, 2007 Author Share Posted January 5, 2007 and this time I promise to focus on the issue and not get off onto ETn 'folklore'!!! I HAVE heard some rumors about some Sheriff who is still looking for some dude who got away....[] Quote Link to comment Share on other sites More sharing options...
Coytee Posted January 5, 2007 Author Share Posted January 5, 2007 Additionally, if you are in the planning and building phase, it is rather easy to incorporate Helmholtz resonator bass traps into the wall junctions and corners based upon measurements so that you actually address the real as opposed to the imagined problems. THIS is the kind of seed I was looking for. I don't know what you mean by this (incorporating the resonator traps into wall junctions) but now I have time to find out about it and perhaps put it into a plan of action. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted January 7, 2007 Share Posted January 7, 2007 Perhaps this will help http://en.wikipedia.org/wiki/Golden_ratio Quote Link to comment Share on other sites More sharing options...
pauln Posted January 31, 2007 Share Posted January 31, 2007 I've read that tapered walls/ceiling will not work well for controlling the lower frequencies below about 250Hz because the waves will just average across the surface (and it is these lower freqs that you want to control). The Golden Ratios will fix these with the right speaker placement - see the Insights at Cardas.com. The tapered walls/ceiling will reduce "flutter echo" which is the high speed snapping you hear if you clap your hands and hear the sound bouncing quickly between the surfaces back and fourth real fast - but this is better eliminated with surface treatments. The only thing I've seen in terms of special shape for rooms that is considered quite good is if the overall area of cross section increases from front to back. My room is like this - the end with the speakers starts with a 7 foothigh ceiling, but buy the time you get about 1/3 into the room the ceiling is 10 feet. More difficult, but if you can get your side walls to splay out a bit from the front to the back you enjoy a similar advantage. Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 1, 2007 Share Posted February 1, 2007 If only Golden Ratios = good sound... [] No offense Paul, but that Cardas stuff about golden rectangles is totally bogus... [^o)] It wasn't too comforting when they use the wrong words and make up wierd terminology that doesn't really say anything. For example: "A node, or the frequency where speakers and parallel walls interact..." As far as the low frequencies are concerned - the angle of incidence always equals the angle of reflection - it is not frequency dependant...at least classically speaking. Whenever there is a nonperfect reflection (some sound is transmitted through the surface), the angle of reflection changes slightly - but it's still not frequency dependant. And the change in angle is going to change just as much as the difference between parallel and splayed walls (generally speaking - there's minor exceptions to that rule too...I believe it's called "Snell's Law"). That's not to say that splaying walls magically fixes low frequency issues, but the resonant frequencies certainly decay faster... One of the biggest goals of splayed walls is to redirect the first reflections so that they travel further and hopefully bounce off more walls before arriving at the listening position. This increases the ITD, hopefully removing comb-filtering effects within the Haas Window and then setting the beginning stages for achieving a natural semi-reverberant field. At least that's what I'm getting out of the latest acoustics texts I've been reading (thx Mark)... Quote Link to comment Share on other sites More sharing options...
mas Posted February 1, 2007 Share Posted February 1, 2007 Splaying the walls does not resolve room mode/resonance issues as many think...it reduces a phenomena known as flutter echo that occurs between parallel surfaces - in other words, a reflection that repeatedly bounces back and force (is this description OK with Chloe?). Oh, and to answer a question that was raised a while ago (I know by Gil...), traditionally, the use of a "kicker" was used to redirect and break up the reinforcement of the energy that contributed to flutter echo. So, "kicker" refers to a technique for breaking up flutter echo. Room topology, coupled spaces, etc. will determine the room mode/LF resonance issues and these must be trapped. As far as reflections being 'frequency dependent'... The angle of reflection is equal to the angle of incidence for all frequencies (again, for Chloe, what comes in goes out). But, what is frequency dependent is the character of the reflected sound. Due to the characteristics of the incident surface, the spectral content of the reflected sound may be altered. Certain frequencies will not be reflected at unity and will be attenuated more than others. And depending upon the surface, this affect can be quite dramatic. Seems simple, right. It gets a bit more confusing! (And also a reason empirical measurements are so valuable.) Absorption is not purely absorptive. It has an impedance and is reactive. It will absorb certain frequencies, but it acts like a terific reflector to other frequencies. Therefore absorption must be seen as frequency selective! Unfortunately, many erroneously assume much too much for absorptive materials and the result is their over uses and under-effectiveness. Likewise, diffusive materials are also frequency dependent. And before anyone jump in with the poly-cylinders...a 'first generation' application, these structures are not so much a diffusive devices as they are scattering devices. So, what's the difference Chloe may ask? A truly diffusive surface will randomize (diffuse) the reflections while also decreasing their intensity. Poly cylinders do not randomize the reflections; rather they simply reduce their intensity while breaking the original incident wavefront into lower intensity specular (focused) reflections. A good first step to be sure, but the focused specular reflections are audible. As a result, it should be apparent why products such as D'Antonio's Schroeder based RPG systems quickly assumed a prominent position over them upon their release. They allowed the move from a 'half-way' measure to a more ideal application. (And BTW, D'Antonio's newest venture is rather fascinating as well - but more on that in the later reaches of the small room, as it is a variation upon current models...and it will only be available to those with the very big bucks!) Oh, and regards to room dimensions, the goal was simply to avoid reinforcement of room modes where the peaks are coincident. In other words, multiples of a dimension will place the mode peaks at the same spots where they will effectively sum. Thus the goal is to spread the peaks out and around, so that they are more evenly scattered. Thus reducing the problem and making it a bit easier to address. But no, magic dimensions do NOT solve room modes! he only real solution to actually solving room modes is to either have no room or to have no LF energy. See how easy it is!? ...And you might have thought this acoustics stuff was hard! Sounds like I need to get on with the small room stuff as enough folks are asking lots of questions that will be addressed there. Oh, and as I mentioned once before somewhere...Ron Sauros is going to be publishing several papers this season on the absorptive and reflective coefficients of sound scattering surfaces, as their measurements in attempting to provide valid specs for Russ Berger's Space Array and Space Couplers have uncovered, not only major issues with the existing process - a polite way of saying that the heretofore current methodology is not only complete hooey, but much of it was actually done on scale models - and don't even ask me what the hell that means other than that it is flawed at best. But the neat thing is that, in addition to turning the acoustics world upside down once again, we just may get some real useful specs as a result! So stay tuned, as this is what makes acoustics so much fun! Unlike other areas that are pretty well understood and rather boring, acoustics is still undergoing major revision!!! Quote Link to comment Share on other sites More sharing options...
Coytee Posted February 1, 2007 Author Share Posted February 1, 2007 Although Chloe was VERY non approval of me when I just now woke her up... she did indicate to me you do not have anything (yet) to fear from her wrath. We both know however, just how fickle women can be at times so it might serve you well to stay on the straight & narrow. (that last piece of advice was from her) [&] Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted February 2, 2007 Share Posted February 2, 2007 The golden ratio, usually denoted ,expresses the relationship that the sum of two quantities is to thelarger quantity as the larger is to the smaller. The golden ratio isthe following algebraic irrational number with its numerical approximation: The figure of a golden section on the right illustrates the defining geometric relationship. Expressed algebraically: At least since the Renaissance, many artists and architects have proportioned their works to approximate the golden ratioespecially in the form of the golden rectangle, in which the ratio of the longer side to the shorter is the golden ratiobelieving this proportion to be aesthetically pleasing. Mathematicians have studied the golden ratio because of its unique and interesting properties. Other names frequently used for or closely related to the golden ratio are golden section (Latin: sectio aurea), golden mean, golden number, and the Greek letter phi (f).[1][2][3] Other terms encountered include extreme and mean ratio, medial section, divine proportion (Italian: proporzione divina), divine section (Latin: sectio divina), golden proportion, golden cut,[4] and mean of Phidias.[ Quote Link to comment Share on other sites More sharing options...
Arkytype Posted February 7, 2007 Share Posted February 7, 2007 Trey or Roy might confirm this but I seem to remember that when PWK built the new listening room (late '70s?), all the walls were non-parallel but the corners were built with right angles for the Klipschorns. I don't think it is the listening room next to the lab but the one with the old theater seats. I've done one commercial application (TV audio suite) with splayed walls and the room "sounds" quite good. I think the splay was one foot per twenty feet. There are a couple of issues to consider with non-rectangular rooms. If the angle is too extreme, furniture or equipment racks might not fit well. The other issue is that while you can easily and accurately compute room modes for rectangular spaces, I don't think there is a program out there that will compute room modes for non-orthoganal walls. I'd rather deal with known modal frequencies and SPL vs.distance. Chasing and damping reinforced bass modes can be an exercise in frustration. Lee Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 7, 2007 Share Posted February 7, 2007 The other issue is that while you can easily and accurately compute room modes for rectangular spaces, I don't think there is a program out there that will compute room modes for non-orthoganal walls. I'd rather deal with known modal frequencies and SPL vs.distance. Chasing and damping reinforced bass modes can be an exercise in frustration. That's what measuring is for...and you can do it for under $150. It will yield results much more accurate than any kind of predictions will entail. Quote Link to comment Share on other sites More sharing options...
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