First let me say that I have just found this website today and I am in heaven!! Thank you for such a great resource as home recording continues to expand.
I was very excited to read John Sayers' sticky post: Small studio in 3D. This studio layout is almost exactly what I need because of my size limitations.
It is probably ignorance on my part but can someone explain the specific materials used on the walls?
* Because of the rear wall color being gray, does this imply that the entire wall is covered in cloth? Also, what does "black cloth" mean, aside from the obvious color? Is the there an acoustic absorption difference?
* What particular wood type/thickness is recommended for the speaker fronts?
Thanks sincerely,
Richard
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Hmm, just posted above and I appear as guest?? My browser must have logged me out while writing the post. Sorry
Question about John Sayers "small studio" post
Originally posted at johnlsayers.com, topic 19321.
Hi Richard, and welcome! :)
Yeah, there's a bug on the forum software someplace, that we haven't figured out yet... :( We are working on it! But I fixed your post now, so it is actually "you" who wrote itHmm, just posted above and I appear as guest?? My browser must have logged me out while writing the post. Sorry
We kinda like it here too! :)First let me say that I have just found this website today and I am in heaven!!
If you open the "Layers" menu in SketchUp, you can turn on and off each type of material, to see which parts of the model are affected.It is probably ignorance on my part but can someone explain the specific materials used on the walls?
Right. And behind that cloth is a thick layer of acoustic absorption, such as OC-703, or many other types of fiberglass, or even mineral wool insulation. That is the usual way of doing the rear wall of a small studio, and especially one that follows the RFZ design concept. Small rooms need lots of bass trapping, and the smaller they are the more they need. It is common to have large bass traps in the rear vertical corners (which is what you are seeing in that design), and also to have the rest of the rear wall fully absorbent.* Because of the rear wall color being gray, does this imply that the entire wall is covered in cloth?
Nope! Just plain old black fabric, from your favorite manufacturer. the only restriction is that it has to be "breathable", in the sense that you can hold a piece tightly over your nose and mouth, and breathe normally without noticing much additional resistance. If you are struggling to breath, or gasping for breath, or turning blue as you writhe on the floor, then that's not the right type of cloth... :) The purpose of that cloth is aesthetic, not acoustic. It is to hide the ugly insulation behind it. Typical fabrics used in acoustics are a bit translucent; you can see through the weave under the right lighting conditions: So the extra layer of matte black cloth behind it, helps to block your view of the "ugly stuff" while also not affecting the acoustic properties of the treatment. That's why it has to be breathable: so air (and therefore sound) can move through it very freely.Also, what does "black cloth" mean, aside from the obvious color? Is the there an acoustic absorption difference?
Typical are OSB, MDF or plywood. It has to be THICK! And heavy. Some people do their soffits in concrete, brick or stone.... But typically for a modest home studio, it will be two layers of 5/8" or 3/4" plywood. Don't forget that John isn't showing all the details in that model! It's just a guideline, or template, that you can use as the basis for yours, and complete the details yourself. - Stuart -What particular wood type/thickness is recommended for the speaker fronts?
Thank you so much for the quick reply, and the helpful advice! Using the layers window as you suggested, was a real help.
Another question:
The design has a mix room and a recording room. If the recording room were eliminated, could the entire space (11'x19') be modified to create a better mix room? I've tried to research into the baffling topic of room modes but still don't have a clear understanding. I just know that the rule of thumb is "the bigger the space, the better the sound." Please understand that I'm not asking for an updated .skp file (although that woud be lovely), I would like someone to explain the pros or cons to using the entire 11'x19' space for mixing.
Thanks sincerely,
Richard
Yeah, it is a bit mind-boggling at first, isn't it? OK, it works something like this: Modes are just a natural consequence of sound happening in a room that has walls around it. In other words, all rooms have modes! There is no getting around that, no mater how big or small the room is. Every room that has walls, also has modes. So what is a mode? It's just a path that a sound wave can take around the room, and arrive back at its starting point in phase with itself, and going the same direction. In other words, as it takes the second trip around the room, it will follow the exact same route it took the first time, and will be in phase with itself ever inch of the way: And the same thing will happen on the third trip around the room. And the forth. And the five thousand one hundred and twenty seventh. And.... So if the original note that caused the wave happens to be playing still, coming out of the speaker, on every single trip around the room the wave is adding just a bit more energy to that, so over time (milliseconds!) the sound swells, and grows, and grows some more. Even worse, since there is now energy following that path around the room so very nicely, when the speaker STOPS playing that note (and maybe goes silent, or plays another note), that original note carries on running around the same path as it always did, "resonating" for a looooong time, until it slowly decays away, either due to the normal attenuation of the air it is passing through, or due to acoustic treatment on the walls that it is hitting as it bounces around the room. That, of course, is the reason why you cannot use EQ to "kill" a mode: once the speaker stops making it, the EQ can do nothing more, yet the energy still carries on around the roooooommmmmm...... Modes are also called "standing waves", because if you could somehow see the pattern of pressure peaks and nulls in the room, they are stationary: they don't move. The peak is always in the exact same spot in the room, and so is the null. Actually, "standing wave" is a bit confusing, because it leads you to think that the sound energy itself is standing still and not moving! That isn't true, of course: the energy is still rushing around the room madly at 343 meters per second, just like it always did: it is just the location within he room where the pressure peak occurs that "stands", not the sound itself. The simplest form of a standing wave, or room mode, is when you have two parallel walls a certain distance apart. Any sound wave whose wavelength fits exactly between those two walls (round trip), will form a standing wave. In other words, if the half-wave length of the wave fits between two walls, then it will be a standing wave. So for example, if your walls are exactly 3.4 meters apart, then a tone of 50Hz will cause a standing wave. Why? Because the speed of sound is 340 meters per second.... A 1Hz tone will have a wavelength of 340 meters, a 10 Hz tone is 34.0m and a 100Hz tone is 3.4 m. But actually, a 100 Hz tone would fit in TWICE (it's the half-wave we need, remember? The wave has to make half a trip to the other wall, then half a trip back again) so the fundamental resonant frequency is the tone at half the frequency (one octave down) which is 50 Hz. So for a room with walls 3.4 meters apart, you will get a standing wave at 50Hz, as well as all the harmonics of 50Hz: There will be another mode at 100Hz, then 150, then 200, etc. all the way up the scale. Any time a note plays at any of those frequencies, the mode will be "triggered" or "excited", and the room will ring loudly, and long. Even after you stop playing that note, the ringing will carry on for a few (hundred) milliseconds, dying away slowly. Obviously, that's not a good situation: In that case, the room is lying to you! The sound stopped, but the room is telling you that it didn't stop. Not good. OK, but what happens in this hypothetical room if you then play a tone at 58Hz? Or 41 Hz? Or any other note that is NOT a multiple of fifty? What happens then, is: nothing. Nothing at all. The speaker plays it, you hear it, end of story. When the speaker stops, so does the note. No ringing. No amplification. Nothing at all happens, except that you hear all those other notes perfectly. It's just the ones that excite the mode, that are causing you trouble. So you figure "Great! Ill just move my walls further apart, and the mode will go away!" Ummm... no it won't... it will just move to a different frequency. Let's say you decide to put your walls 4.3 meters apart, instead of 3.4. Wonderful! You no longer have a mode at 50Hz! Congratulations! Your fundamental mode is now at 40 Hz. And instead of having harmonics at 100, 150, 200, 250, etc as you did before, they are now at 80, 120, 160, 200, etc. So basically you changed nothing, except to move the whole modal response down the scale a bit. In other words, you cannot get rid of modes by moving walls! All you do is change the mode to a different frequency. But it gets more interesting! So far we have been looking at a room with just two walls. Rooms normally have six walls (3 sets in parallel). For this, we'll consider that the "ceiling" and "floor" are just walls turned on their sides: it makes it easier to explain, and sound waves don't care about "up" and "down" anyway... :) So let's look at a more normal room: the front and back walls are as above, 4.3 meters apart. the side walls are as before that, 3.4 meters apart. And let's say that the top and bottom walls ("ceiling" and "floor") are 2.15 meters apart. So now you have a fundamental mode for "room length" at 40 Hz, a fundamental mode for "width" at 50 Hz, and a fundamental mode for "height" at 80 Hz. But wait a sec! The first harmonic of 40 Hz (length) is also 80 Hz! So the modes for the length and height will all be in the same place on the spectrum and we'll have DOUBLE the problem! If you play an 80 Hz tone now, then you'll be triggering TWO modes, instead of just one! You'll be hitting the first height mode, and the second length mode, so the reverberation will be much stronger, and last much longer. Bad, bad bad... Oh but something else just happened! The 8th harmonic of height is 200 Hz, and the 3rd harmonic of length is 200 Hz, and the 4th harmonic of width is also 200 Hz.! Dammit, they all line up!!! That means that if you play a 200 Hz tone in there, you'll be triggering THREE modes at once, not just one or two! So the result will be many times louder again, and the "ringing" will last many times longer again.... :( What to do? Ahhh! That's the secret: Move the walls just a bit, so the modes no longer line up. Remember, you can control what frequency the modes occur at, by moving the walls closer together or further apart. So if you are smart, you can figure out distances that cause the modes to NOT line up: put each pair of walls at different and unrelated distances, to get different frequencies, and you solve this "double" and "triple" mode thingy. Simple! So that's what "room ratios" are all about: it is finding a set of dimensions that forces the room modes to NOT be at the same frequency, and in fact to be spread around the spectrum evenly and smoothly. In the best case, you would have exactly one mode for every single frequency on the spectrum, and all modes would ring exactly the same level, and last exactly the same time. That perfect world doesn't exist, so the best we can do is to spread the modes around evenly and smoothly: Not too far apart, and not too close together. Thus, the never.ending hunt for the "golden" ratio, which also doesn't exist. There are a bunch of good ones, yes, but none is perfect. So, just when you thought it was all clear, here's a curve ball to throw you entirely off base again: Modes don't just occur between two parallel walls. The can also occur between FOUR walls, and also between all SIX walls! :shock: Remember, a mode is just a path around the room that allows a wave to get back to its starting point heading in the exact same direction, and in phase with itself. There are simple paths back and forth between two walls, and those are called "axial" modes: the wave hits the wall head-on, then bounces straight back the other way down the axis of the room, hits the far wall, returns.... Rinse. repeat... Those modes run along the axes of the room, so they are called "axial modes". But there are other paths around the room too, where the waves don't hit the walls head-on: They hit at an angle, a sort of glancing blow, then they head off on a tangent, in another direction. Ahh! So they go off on a tangent? Then we'll call them "tangential" modes. They hit four out of six walls as they go around the room. And then there are some really super, extra tangential ones that run off on major oblique paths, smashing into all six walls before they get back home and start again. And you guessed it, because they follow such oblique paths, we'll call them "oblique" modes. So there are three different types of mode: axials (two walls), tangentials (four walls) and obliques (six walls). Now since it is so complicated to talk about "the second tangential mode that hits the front wall, the back wall, the floor and the ceiling", smart people invented an easy-to-understand shorthand method: they refer to modes by a 3-digit number with commas in between, where the first digit is the room length, the second is room width, and the third is room height. So the (1,0,0) mode is the fist axial mode in the length direction, the (0,0,3) mode is the 3rd axial mode in the height direction, and the (4,0,5) mode is a tangential mode related to the 4th harmonic of the length and the fifth harmonic of the height. Any mode notation that has only one number in it (the others are zeros) is an axial mode. If it has two numbers, it is tangential. And if it has 3 numbers, it is oblique. So you can tell very quickly by looking, which surfaces of the room are involved: if the middle number is not zero, then the side walls are involved. If the last number is not zero then the ceiling and floor are involved, and if the first number is not zero then the front and back walls are involved. This is useful when figuring out how to TREAT a mode. Obviously, if you do a room test and find out that you have a big issue with the 3,0,0 mode, then putting treatment on the ceiling is totally useless! That's an axial mode that only touches the front and back walls: it never goes anywhere near the ceiling, so there is zilch you can do up there to treat that mode. You could ONLY treat that on the front and back walls (or in the corners associated with those walls). Ditto for the 0,1,1 mode; that one only touches the ceiling, floor and side walls, so it won't ever "see" any treatment you lay out for it on the back wall, for example. Of course, if your problem happens to be an oblique mode, you are lucky, because you can treat it anywhere! Not only that, but obliques are 3dB down from tangentials, which in turn are 3dB down from axials. OK, so how does all that work in practice, and how the hell is it related to the question that you actually asked? :) Just a bit more, and we'll get there... OK, so the goal is to have lots of modes at all frequencies, so the room sounds more or less the same no matter what note you play, right? Should be simple, right? .... Nope. Not so simple. It would be simple if we humans could only hear tones above 1 Khz, but since we hear down to 20 Hz, it ain't simple at all!!! Imagine this: You play that famous 50Hz tone in a room that measures 3m by 2.5m by 2m high. What happens? Nothing! There are no modes down that low in such a room. The lowest mode for that room is 57.4 Hz, so NOTHING you play lower than that can ever trigger a mode, because there are no modes! The room has no "modal support" below 57.4 Hz. In fact, for such a room, there are no modes at all in the entire bottom octave of the musical scale. Not one single mode. So much for wanting to have several modes for every note! It should be clear that the room has to be a lot bigger in order to have a mode for every note. In fact, it has to be at least 8.6 m long to be able to support even ONE mode down at 20 Hz. That's 28 feet long.... In fact, about the smallest size a room can be and be guaranteed of having at least two modes for every note on the musical scale, is about 12m long, 10m wide, and 9m high... That's 40 feet long, 32 feet wide, 29 feet high. Changing light bulbs in the ceiling of a 30-foot high control room would be a real pain! So, to answer your basic underlying question: is a big room better than a small one, modally? Answer: yes, it is. At the one extreme end, small rooms (like broom closets) cannot have any modal support at all for the lower end of the scale, while really large (hangers for 747) rooms can have perfect modal support for the entire spectrum, with multiple modes even at the lowest notes. That said, I'm not so sure I'd like to record a rock band in a 747 hanger.... :) To answer your other question: does it make sense to make the room bigger in order to get a better modal spread? Yes it does. However, the room has to be gigantic if you want perfect modal response. Fortunately, that isn't necessary... Fortunately, we can treat rooms acoustically to "damp" the modes. Remember, we can't make modes go away, since they are a natural consequence of room dimensions, and energy bouncing around the room. Hmmmm, but wait a sec: we can't change the mode, but maybe we can do something about that "bouncing" part! For example, we could put something that absorbs sound on the walls, exactly where the energy hits it! Yeah! We can absorb the hell out of the energy part way along the path, so it never gets back to the start, and can't go around again! Yeah! That's the ticket! Except of course, it isn't that easy. In order to effectively absorb absolutely all of the energy in a standing wave, you would have to have hugely thick absorption that is 100% perfect at absorbing sound: There is no such material! Nothing absorbs sound perfectly. Not even the entire planet. So we are out of luck on that one. But there are some materials that do a reasonably decent job of absorbing, and we don't actually need to suck up all the energy on the first bounce. We can let it go around a couple of times, absorbing a bit on each bounce, so we can control the decay time of each mode: make it die away at the rate we want. That's what bass traps do: they are deep, large, fibrous, and can suck up a bunch of energy each time the wave goes past. Put enough of them in the right places, and you can damp ALL the modes to a reasonable decay time. Bingo! Done! Finally! :) But that still doesn't fully answer your question: Is it better to leave one room out in order to get a better ratio in the only remaining room? The only answer I can give you is "it depends". You are sure gonna hate me for that, after making you read all the above waffling, but that's the plain truth. You'll have to spend some time playing around with a room mode calculator (Bob Golds' Andy Mel's, etc), plugging in numbers for the largest size control room you could get if there were TWO rooms, and compare that to the largest size it could be if it was just one big room. In general, yes, a big room is going to perform better than a small room, but with a long thin space like that, you will very likely find that there are a few pretty good ratios you could use for the two-room scenario, and not many at all for the single room, scenario. It might turn out the the best ratio for the one-room is actually worse the best ratios for the two-room scenario. And of course, it might be the other way around: you have to go through the process, and see what comes up. RPG used to sell a neat little piece of software that would do that for you, called "room optimizer", but they dropped it a while ago. You could enter the largest possible dimensions available for each axis, and it would run through thousands of possible ratios, nudging walls here and there, to come up with the very best possible ratio, given those dimensions. It's a pity they don't have it any more: it was neat. So now you have to do it by hand.... There's also the practical aspect: do you need that other room? For example, I find it really hard and annoying to try to record drums in the same room where I'm sitting with my speakers: In the CR, I need to hear each mic all by itself coming over my speakers, and with no bleed at all from the room where the drums are. If the drums are with me in the same room, it is major big-time hard for me to do. Maybe that doesn't bother you, but I need two rooms. There's also the issue of budget: two rooms is much more expensive than one. Do you want to spend that extra, or not? There might also be physical limitations. For example, no possible place to put a door into the other room. etc. It's not just the room ratio that matters. Like most things with studio design, it's a juggling game. You have to compromise all over, and come up with the best set of "goods" and "bads" that fit YOUR way of working. In fact, if it was JUST the ratio you were worried about, I'd say forget it! Ratios are not the be-all and and-all of studio design. Ratios are one of many useful tools, but not even very high on the list. There's no need at all to sacrifice practicality, functionality, and comfort just to get a good ratio! Ratios just aren't that important. If I had to choose between one room or two on the sole basis of ratios, I'd go with two every time, no question about it! Its the other factors that matter more, not the ratio. :) - Stuart -I've tried to research into the baffling topic of room modes but still don't have a clear understanding.
Wow Stuart! You need to write a book...or go catch your breath. :D That post was VERY helpful!! The science of room modes is becoming more and more clear.
I have a 12'x50' floor space available for building my home studio. I'll play around with the ratios that "Handbook fir Sound Engineers" recommends. When I get a Sketchup file done, I'll uploaded it for comments and suggestions.
Thanks again for all the HELPFUL advice!
People keep telling me that! One of these days I might actually decide to do it.... :)Wow Stuart! You need to write a book...
:thu:Thanks again for all the HELPFUL advice!
I'm looking forwards to seeing that. - Stuart -When I get a Sketchup file done, I'll uploaded it for comments and suggestions.
I'm still working on my control room design in sketchup but I'll be posting it soon.
Due to the space available, I'm designing a 129.6"x163"x102" (WxLxH) room based on ratios listed in the Sound Engineers Handbook:
Design #2
W=1.28 x H
L=1.54 x H
Do these ratios only work for solid wall construction, or can I use fully absorbent (cloth covered) back wall like the one in John's studio design?
Solid walls. All room ratios are measured to the solid, massive, rigid boundary of the room, since that is what the sound waves "see" as the limit of their travels. In other words, measure to the surfaces that you would see as you stand inside the room after you just finished building it, but before putting any acoustic treatment in it at all. It's the same with John's designs too: the cloth "walls" you see are not really walls at all; they are just frames with fabric on them that hide the treatment behind. That treatment, and the fabric, are "inside" the room, not outside it, and there is still a hard, solid, rigid, massive boundary wall behind the treatment, which is what John would have used when doing his calculations. So use those dimensions in your calculations. This calculator might help you too: http://www.bobgolds.com/Mode/RoomModes.htm just plug in your numbers, and it does all the work for you. - Stuart -Do these ratios only work for solid wall construction, or can I use fully absorbent (cloth covered) back wall like the one in John's studio design?
I understand. I've been behind a mixing console for years but I've never had the "privilege" of designing my own studio. I love sound and I'm thrilled to be learning more about it through this forum! Thanks Stuart
:thu: That's what this forum is here for! To help guys like you as much as possible. :)
If you don't already have them, then I'd suggest two books that are really helpful for home studio builders: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais.
- Stuart -
Stuart,
I thought that I would add to this thread as you gave a very good explanation on modes and the approach around trying to "solve" for the best performance. It seems that for an existing structure, that you are going to want to minimize the changes you would physically need to do. But, what I am struggling with when using bobgolds mode calculation tool, is what am I optimizing for and how much is sufficient?
For example, there are the R. Walker ratios, to get to the three "passes"
Then there is the Bonello curve and to create a monotonically smooth curve - for example, if it is not continuously increasing, but only dips by half a division on the vertical axis, is this good enough.
How smooth is smooth enough and how does that impact sound quality, and then ultimately get you close enough so you can mitigate any of the remaining issues through other room treatments (bass traps, etc).
Craig O
Great question, Craig!
Basically, you are trying to optimize everything at once! :)
But the most important in my opinion is the three BBC tests. If you fail one of those, then you will have a problematic room that may not be usable at all, or it might need large amounts of treatment to make it usable. So first fix "fails" on those three.
Then, once you are passing all of those, then take a look at where the first dozen or so modes fall on the "keyboard", and try to adjust the room dimensions to get a good spread there, with the modes not too close together (not on the same note), and also not too far apart (hopefully not more than 3 or 4 keys apart, at the very low end).
Finally, take a look at the Bonello chart, to make sure that you don't have the dreaded "dip" at some point, and that the curve is reasonably smooth: What that is actually telling you, is how many modes you have in each one-third octave band, so you want to see a steady geometric rise, with progressively more modes in each higher band. In fact, if you do the first two parts right, then the Bonello chart will automatically be pretty smooth, without dips.
Yes, for small rooms it's a juggling game, where you are trying to optimize a bunch of things at once. And the best advice I can give you is: Don't go crazy here! You do NOT need to tweak and nudge your room dimensions by fractions of an inch / millimeters, trying to find the "perfect ratio"! There is no such thing. all you really need to do is to make sure you are far away from the "bad" ratios (passing all 3 BBC tests ensures that) and that you are close to one of the "good" ratios. That's it. The rest can be taken care of with treatment.
- Stuart -
Stuart,
Thanks, this helps to frame the process of attacking this. It sounds like solving 50 equations with three variables (L, W, H) ... oops, I meant four, the fourth being budget/sanity. :D
Solving for the BBC numbers appears pretty straightforward, although I have to admit, I really don't understand what I am solving. The technical paper linked to the site was a little tough to comprehend for me. But for my room, which is neatly a box at the moment (24ft x 22ft 8in x 8ft or 7.32m x 6.91m x 2.44m) and failing two of the three BBC parameters, could be made to pass the BBC test by moving one wall 4 feet (20ft x 22ft 8in x 8ft or 6.1m x 6.91m x 2.44m). This seems to really make sense as in the current state we have a room height that is exactly one third the room length. So changing that to some other value makes sense. And on the budget/sanity parameter I have created a small closet for storage and can get all the cases, cable storage, etc neatly put away. Now we are are at three passes for the BBC test.
Now for the modes! Fortunately, with your explanation, and with a sine wave generator called my trusty old Yamaha DX7, I am "hear" the offending frequencies (at least in the lower octave) for my CURRENT room dimensions (24ft x 22ft 8in x 8ft or 7.32m x 6.91m x 2.44m).
When I interpret the results of the room mode calculator produces, and evaluate using the sine wave and my ears, I want to get some "feel" for this so I can have some intelligence as I try to optimize things. It seems like the dark green lines (negative) are manageable. I have a lot of dark green lines in some proximity of each other, but even with that, they don't sound like they are "jumping" out in the room. For example this series of lines and listening at the frequencies around it.
Frequency hz Spacing % Wavelength 1/2 Wavelength 1/4 Wavelength p q r Mode
141.1 1.1 8'0" 4'0" 2'0" 3 4 1 Oblique
141.3 0.1 7'12" 3'12" 1'12" 0 0 2 Axial
141.3 0 7'12" 3'12" 1'12" 6 0 0 Axial
143.2 1.3 7'11" 3'11" 1'12" 0 5 1 Tangential
143.2 0 7'11" 3'11" 1'12" 1 0 2 Tangential
143.2 0 7'11" 3'11" 1'12" 3 5 0 Tangential
143.4 0.1 7'11" 3'11" 1'12" 0 1 2 Tangential
143.4 0 7'11" 3'11" 1'12" 6 1 0 Tangential
Then looking at the light green lines (0 to 1 warning level) when they are grouped together are problematic. When I listen here, that frequency band really pops out and you can hear that peak. So would this be considered a set of frequencies I MUST "tame" by moving around the room dimensions. When I listen, it sounds like this would be really tough to tame with any type of room treatment.
Frequency hz Spacing % Wavelength 1/2 Wavelength 1/4 Wavelength p q r Mode
47.1 27.1 23'12" 11'12" 5'12" 2 0 0 Axial
49.8 5.4 22'8" 11'4" 5'8" 0 2 0 Axial
53.3 6.5 21'2" 10'7" 5'4" 2 1 0 Tangential
55.1 3.2 20'6" 10'3" 5'2" 1 2 0 Tangential
Then I have the single yellow lines (1 to 2 warning level), they almost sound like as long as they are not grouped with other light green or yellow lines, then you could manage to EQ them (one frequency is pretty low so my speakers is not producing a lot of energy down there so I might be mistaken on this assumption).
So the strategy becomes (I guess I am becoming that manual version of the RPG software you mention) ...
1. Kill all the red lines (I am fortunate that I don't have these, so can't imagine how they would sound).
2. Break up the GROUPS of light greens and yellows
Is "typical" room treatment, bass traps, etc able to deal with a set of light green lines as long as they are a semi-tone apart? My goal being to minimize the amount of changes (like moving walls) so the cost is minimizes. But at the same time not be so pound wise and penny foolish and and not make a change and then have to do a ton of room treatments downstream to get it to sound great.
Thanks in advance,
Craig
Now after some time of tweaking and looking at some of the options in the room. Let know your thoughts on if I am on the right track here.
First, I got it to pass all of the BBC tests.
Then I tried moving around all the parameters, based on some of the guidance on the site, to constrain the height of the ceiling to be fixed since that is only 8 feet high and also tough to change.
Then after some tweaking, I ended up coming back to leaving one wall where it is and then moving another wall in by 3.5 feet. So the resulting dimensions came to, 20.5 feet x 22.67 feet x 8 feet. With this I seem to have maximized the separation of the modes with the exception of two at 55 Hz.
The Bonello curve is attached. And as you can see it is not monotonically increasing, but it also doesn't have big dips (of course dip size is relative), and so is that a sufficient degree of smoothness to achieve the potential for great sound.
So it comes back to the question of, with the resulting "warts" is the room characteristics be tamed with sonic treatments in the room, things like bass traps, etc.
Thanks in Advance,
Craig
Those are basically just critical tests for relationships between room dimensions, that's all. Having a "fail" there indicates that your room has a relationship between dimensions that is known to be poor, acoustically. That's what the L, W, and H are in those equations. So failing the BBC rule that says "l < 3h & w < 3h" just means that either the length is more than three times the height, or the width is more than three times the height: both of those cause a "fail", because the room is just plain too long for the height. If you look at the room ratio for your room (right above the 3 BBC tests), you'll get the message. For your room, it says "Room Ratio: 1 : 2.83 : 3", so there's the issue: it is too long for the height. because the last number (Length) is three times the first number (Height).although I have to admit, I really don't understand what I am solving.
Yup! so you are failing TWICE in that very sense! Firstly as above: the room is just too long (more than 3 times height), and secondly because there's a direct mathematical relationship ("no integer multiple within 5%: Fail (ratio3 = ratio1 * 3)". So making the room shorter, or higher, will solve that issue.This seems to really make sense as in the current state we have a room height that is exactly one third the room length.
You might not be listening at the correct location in the room to hear them! :) another curve ball to add to your juggling match... Room modes are standing waves, meaning that the pressure peaks and nulls fall at very specific fixed locations within the room. If you are not standing in one of those peaks or nulls, then you won't notice too much of an increase in sound level, and since you are just playing sine sweeps, you also won't notice the long decay of those modes, since that will be masked somewhat by the sound of the next higher frequency. In other words, the modes are still there, but your method for detecting them is flawed! You will be able to hear some of them, for sure, since there is some type of modal activity going on for pretty much every possible location in the room. But you won't necessarily be hearing the ones that matter. Setting up your speakers and measurement mic correctly in the room, then running the REW software, will reveal all of the secrets of the room.but even with that, they don't sound like they are "jumping" out in the room.
Yup! three modes lined up right on top of each other, and two of them are axials: your second height axial lines up with your 6th length axial, spot on, because the room is 3 times longer than it is high. So there's a major issue right there...141.1 1.1 8'0" 4'0" 2'0" 3 4 1 Oblique 141.3 0.1 7'12" 3'12" 1'12" 0 0 2 Axial 141.3 0 7'12" 3'12" 1'12" 6 0 0 Axial
Congratulations! That's pretty hard to accomplish, but you managed to line up FIVE tangential modes exactly on top of each other! :shock: :!: :) I'd have to try pretty hard to do better than that! 8) OK, so that's another major issue, and it turns out to be almost exactly lined up with the triple issue mentioned above! So in reality, you have a grand total of EIGHT modes sitting on the very same frequency! Fortunately the frequency is fairly high, and there are many other modes nearby, so that's not too bad. BUT! Those are the SECOND order modes, and the REAL problem is with their first-order siblings, one octave lower:143.2 1.3 7'11" 3'11" 1'12" 0 5 1 Tangential 143.2 0 7'11" 3'11" 1'12" 1 0 2 Tangential 143.2 0 7'11" 3'11" 1'12" 3 5 0 Tangential 143.4 0.1 7'11" 3'11" 1'12" 0 1 2 Tangential 143.4 0 7'11" 3'11" 1'12" 6 1 0 Tangential
That's your real problem here: 6 modes all lined up: 3 axials and 3 tangentials, at a low frequency. I hope you don't plan to play too much bass guitar in there! :)70.6 hz 2.9% 4.88 : 2.44 : 1.22 (0,0,1 Axial) 70.6 hz 0% 4.88 : 2.44 : 1.22 (3,0,0 Axial) 74.4 hz 5.1% 4.63 : 2.31 : 1.16 (1,0,1 Tangential) 74.8 hz 0.5% 4.6 : 2.3 : 1.15 (0,1,1 Tangential) 74.8 hz 0% 4.6 : 2.3 : 1.15 (0,3,0 Axial) 74.8 hz 0% 4.6 : 2.3 : 1.15 (3,1,0 Tangential)
Right. And you are likely hearing both sets of issues at the same time: sine they are spaced exactly one octave apart (musically), you won't be able to easily distinguish them individually, due to the psycho-acoustical masking effect, so it will just sound like one huge puddle of mud.When I listen here, that frequency band really pops out and you can hear that peak.
Yup! No doubt about that.When I listen, it sounds like this would be really tough to tame with any type of room treatment.
Something basically like that, yes, but the basic problem here is that your ceiling height is way too low for the other two dimensions: is there any chance you can make your ceiling higher? Failing that, I'd suggest make your room quite a bit smaller, so that the length and width are more proportional to the height. For that height, the closes dimensions I found that make sense are 5.50 m long, 4.38m wide, and 2.44 high. Plug those in and see what you get. Also, here's another calculator that's a bit more intuitive, and also does auralization: http://amroc.andymel.eu/ The graph on the right showing the "Bolt Area" is rather important: That shows a graph of all possible ratios of width to length (where height is "1"), and the outlined shape in the middle shows the only area that is useful for high-quality studios. Your current ratio is way off the right edge of the page! The one I give above puts you just barely inside the Bolt area, at the top right tip. Food for though.....So the strategy becomes...
What room treatment does is to smooth out the acoustical deficiencies of the room, by damping resonance and possibly diffusing sound, to get the overall frequency response and decay profile within the generally accepted parameters for both: Treatment is also a trade-off (another set of things to juggle! :) You don't want to over-do it, making the room too "dead" and uncomfortable to work in, or too unbalanced (which was the issue with the original LEDE concept of room design, 30 or so years ago). Small rooms need huge amounts of bass trapping, but it has to be done in such a way that it doesn't kill the highs. Diffusion can help, but only in rooms that are large enough to support it, and only when tuned as needed for the room. etc. Unfortunately, it's nowhere near as easy as just trying to hit a few colored lines on a graph! :) If it was that easy, I'd be out of a job.... :)Is "typical" room treatment, bass traps, etc able to deal with a set of light green lines as long as they are a semi-tone apart?
:) :lol: 8) :horse: :shot: Hmmmm.... That's the goal that many studio builders start out with, but it's the one that is least often met. In fact, I'd say that "budget" is the single parameter that NEVER gets met in studio building! You can hit all of your technical parameters reasonably well in most rooms, but budget? Nope. You can never hit that one. In your "juggle" of all the others, that's the ball that hits the floor first, and it usually has to stay there, because as soon as you bend down to pick it up, all the other balls fly off at impossible trajectories, making it impossible to catch them, ever again.... :) :shot:My goal being to minimize the amount of changes (like moving walls) so the cost is minimizes.
Right! And don't forget that treatment does not make room modes go away: that's impossible, since modes are a direct consequence of the room walls existing: All that treatment can do is to damp the ringing of those modes to get it under control. But there's one more packet of balls that you need to open up and add to your juggle: Isolation. The room dimensions you have right now are your outer leaf, before you isolate the room. They will all shrink down a bit, and they amount o "shrinkage" depends on the amount of isolation that you need for your room, which you haven't mentioned yet. I'd suggest starting your own thread for your studio design/build project (and posting a link back to this thread for reference purposes), and laying out all the goals, specifications, and other details you can think of, including the amount of isolation you need, then we can carry on moving forward in that thread, so we don't end up taking over this one. - Stuart -But at the same time not be so pound wise and penny foolish and and not make a change and then have to do a ton of room treatments downstream to get it to sound great