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Square rooms - Is it even possible?
Old 13th November 2009
  #31
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PaulP's Avatar
 

Quote:
Originally Posted by Mesa4x12er View Post
Thanks for the encouragement. All of the bedrooms are squares. The living room is almost square. 14x16. The whole house is a collection of squares. It's not a big house, but it's a classy house. I'll be living alone and it was this or continue renting places which sometimes make it so I can't record at all.
Can you remove a wall between two bedrooms ?

Paul P
Old 13th November 2009
  #32
Gear Nut
 

Mesa,

There are a couple of aspects to your situation that haven't been considered yet, that I think are worth considering:

First, how solid are your walls? If these things are merely one layer of gypsum, the modal problems are not nearly as significant as if you have three layers of gypsum. Much of the bass goes right through the wall with only one layer, and that portion of the bass energy that's going through the wall is not going to be causing any modal build-up.

Next, what is your ceiling dimension? There's a fair chance it's eight feet, and if that's the case, then you've got an excellent ratio between the ceiling dimension and the wall dimensions. That would be 1 : 1.6 between the height and the length dimension, and 1 : 1.58 between the height and the width dimension. In other words, the "Golden Ratio".

Someone has mentioned that you could reduce one of the dimensions by roughly 5% to achieve non-squareness. This is true; it only takes about 5 or 6% to do this, which musically speaking is a semi-tone. But there's a problem with doing that, in this case:

The 1 : 1.6 ratio that exists between the ceiling dimension and (roughly) between the other two dimensions is, in musical terms, a minor 6th. That's good. But if you reduce the minor 6th by a semi-tone (6%), your minor 6th becomes a perfect 5th. That's not so good. In fact, that's very bad. You will have traded a unison for a perfect 5th. That's trading up, for sure, but not by much. A perfect 5th means that the two dimensional resonances will be only one key away from each other, and they will share many common harmonics. You want just the opposite - to spread the harmonics out into many unrelated keys, for musical balance.

The smart thing to do would be to bite the bullet and reduce the width by 12%, which would be a whole step. Now you'd have a diminished 5th ratio (1 : 1.4) between the height and the width. That would mean reducing the width of the room from 12'-8" to 11'-2".

There are those who would argue for keeping the room larger, reasoning that that would make for better acoustics for a room this size. I'm not in that camp. The extra foot and a half may have practical advantages, for sure, but acoustically speaking, at least to my ears, it's always best to have good ratios. I've tried it both ways. The bass is more balanced with good ratios, and as long as you don't shave the longest of your three dimensions, you aren't losing anything on the low end when you trim the room dimension slightly to achieve better ratios. But not everyone can hear it. Like I said at the beginning, with one layer of gypsum, it's a more subtle difference. But it's there.

-Wes
Old 13th November 2009
  #33
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jhbrandt's Avatar
Good point Wes, Thanks...

So I did some more calculations for our friend... Here are the charts from 143" to 134":
http://jhbrandt.net/Helpfiles/143inches.jpg
http://jhbrandt.net/Helpfiles/142inches.jpg
http://jhbrandt.net/Helpfiles/141inches.jpg
http://jhbrandt.net/Helpfiles/140inches.jpg
http://jhbrandt.net/Helpfiles/139inches.jpg
http://jhbrandt.net/Helpfiles/138inches.jpg
http://jhbrandt.net/Helpfiles/137inches.jpg
http://jhbrandt.net/Helpfiles/136inches.jpg
http://jhbrandt.net/Helpfiles/135inches.jpg
http://jhbrandt.net/Helpfiles/134inches.jpg

I still say that you would get the 'best' mode spacing and distrubution by moving the wall in 7 inches.

But like Wes said.. in home construction they only use 1/2" drywall and a good bit of bass passes right through that.. so, you will probably need to do some on-site testing after you choose which way you are going to go.

Wes, I look forward to reading your article on "Architectural & Music Scales in Sound Room Design". thumbsup Very good point. Room ratios are very important in our line of work and the importance of which is something that many people don't understand.

Personally, I tend to look at the table of 'magic' ratios only as a starting point and then design the room based on the best mode response. Usually, like Mesa, we are 'stuck' with certain dimensions. Like I said before, sometimes an inch or two can make all the difference in the world.

OMG, I wish all the studios that I design could be from the ground up.. ~sigh~

Anyway, Mesa, good luck with your room. Let me know how it turns out.
Old 13th November 2009
  #34
Gear Guru
 
Glenn Kuras's Avatar
I can't remember a thread with so many experts chiming in. The poster sure did get his moneys worth on this one. hehhehheh

Wes it is great to see you around. Keep on posting!!!!!!!
Old 13th November 2009
  #35
Gear Guru
Acoustic Party

Indeed Glenn, maybe this is our early Christmas Party........! Cheers.....:-)
I get the impression that Mesa has left the building though.

Also I am adding that word expert to my banned word list.
To put the three in one sentence....
The Titanic was built wrong by professional experts.

Perhaps the biggest point to note here is that there is no consensus appearing. Furthermore if any of us were engaged to treat this job professionally, I believe all of the suggestions made, would have crossed our desks. They are enthusiastic first shots. At the end it would be a system, a balance of factors. I certainly hope so, but I wonder if the audible results would be similar?

Some random points.
Wes, Hi, the ceiling is 9ft. I am hoping Mesa will come back tell us what are the Walls, Floor, Ceiling, made of? Brick would seriously escalate the modal problem in my mind.
If we know the surface material and construction method, plus whether a wall shift or extra wall is on the menu, then we could move toward a consensus, which would be fun.
Irrespective of that info, and irrespective of wall changes, here's my shot at treating this room specifically:-
The most Bass Trapping possible. There are three vertical corners available. Floor to ceiling 32inch wide SuperChunks in the three corners. MegaTraps might be even more powerful, perhaps they have a membrane? Panel Bass Traps at all available ceiling corners. A serious cloud, 3-4 inches thick with a membrane on the ceiling side. Side Reflecting panels, again thick, with membrane to the wall.
Optimise speaker and listening positions by measurement, including height. A substantial couch can have a useful trapping effect, as can large friends in red clothes with a 703 beard.

DD
DD
Old 13th November 2009
  #36
Gear Addict
 
HDJK's Avatar
Quote:
Originally Posted by DanDan View Post
...Floor to ceiling 32inch wide SuperChunks in the three corners. MegaTraps might be even more powerful, perhaps they have a membrane? ...
They do have a membrane (according to Ethan on another forum). I too would like to know which trap would be more effective for bass: superchunks or Realtraps Megatraps?
Old 13th November 2009
  #37
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Also I am adding that word expert to my banned word list.
To put the three in one sentence....
The Titanic was built wrong by professional experts.
Agreed! Maybe a better word is "Acoustic Pros". Though Wes and Avare are in my book "the go to guys". Wes is the guy that come up with the 38% starting point thing.
Old 13th November 2009
  #38
Gear Guru
Who's is bigger

HDJK, unfortunately there is no single figure stat which can compare the power of these traps. Some are linear and some are slightly tuned. The large SSC and Mega are similar in size. They are not in competition with each other or any other products. They are the big guns for big problems. e.g. a small room with brick or concrete walls and floor. It has been said that the Mega has a membrane. A membrane would increase absorption in a broad area, at the expense of some non-linearity. Since we are trying to correct a room non-linearity, this could be exactly the best solution. I think if I had the money I would go Mega. Lots of money and less space, consider the Modex or the 24 inch SSC. If you go SSC, I recommend trying a membrane, a thin sheet of plastic. Measure and listen. If you do this please publish the tests on this forum.
Best, DD
Old 13th November 2009
  #39
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HDJK's Avatar
Thanks
Old 13th November 2009
  #40
Gear Nut
 

So if the ceiling is 9 ft. rather than 8 ft., that changes the calculations. Interestingly, we still have a good ratio between the height dimension and the width dimension (12.66 / 9 = 1.41). The ratio 1 : 1.41 is one of the good ones - a diminished 5th. And we're faced with a similar delimma as before, namely, if we reduce either the width or depth dimension by merely 6% (a semi-tone), we'll create a 1 : 1.33 ratio between that dimension and the height. This ratio ( 1 : 1.33, or a perfect 4th) is also one of the bad ones, although not quite as bad as 1 : 1.5. By instead reducing the width or depth dimension by a full whole step (12%) we can bring that ratio to a major 3rd, or 1 : 1.26, which is one of the very desirable ratios. So if the depth dimension were reduced to 11'-5", you'd have a great set of ratios, namely 1 : 1.26 : 1.41.

Note: as usual, some rounding has been applied for clarity and brevity's sake.

-Wes
Old 14th November 2009
  #41
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Quote:
Originally Posted by jhbrandt View Post
Mesa, I just did some calcs for you....
John
Oh wow man! Thank you so much! I didn't expect anything that specific at all from anyone. I really appreciate it. I have yet to hear this room as the house is being built as we speak. Unfortunately I can't request anything different (such as the 7 in change in wall) as the houses are preset plans from a home builder. Now I just have to get this wall thing figured out.

Quote:
Originally Posted by Glenn Kuras
If you made the false wall of fabric with trapping behind it that would be the best solution.
+1 for your post.
So may rooms, so many problems.
That would work? What type/amount of trapping would I need to put behind it? If this is possible that would be awesome because I'd like to avoid any permanent solutions if possible just because I would like to sell the house at some point!

Quote:
Originally Posted by DanDan
I was intrigued with the wall recommendations so I took a look at it. I have the same conclusion, here's a very cute way to visualise and realise the effects of room dimension changes.
I borrowed this here from knightfly, who posts elsewhere. I hope he doesn't mind. It is very simple but very revealing also. Attachment 143841
So, let's get into this. Mesa some more info please.
What are the walls floor and ceiling made of?
How deep is that slope to the ceiling? Bad enough to prevent installation of a SuperChunk or other Triangles?
Within the context of the rest of the living space, could you shift any of the existing walls?
Best, DD
It's going to be a very typical modern house. Sheet rock/drywall and carpet. No brick or exotic surfaces. The slope I am not 100% sure of. I only saw it once in a model home. Wish I had gotten more specifics about this stuff but I never thought I'd have a group of people actually trying to help me that would ask about it. As far as shifting other walls.. I'm pretty sure that's a no go. All of the rooms are seperated from each other by other rooms (bathrooms etc) that would not allow for any kind of improvement.
Here's the full floorplan. Don't laugh at my little house. :p




Quote:
Originally Posted by andrebrito
Reducing the area by 5 % or splaying the walls is not going to solve this problem. Broadband absorption can tame the entire low frequency range but this is a located problem so tuned absorption is the best way to go...
RPG MODEX is one of the solutions available in the market but a bit expensive
I'll have to check that stuff out. Never heard of it. Thanks.
Old 14th November 2009
  #42
Lives for gear
 

Quote:
Originally Posted by PaulP View Post
Can you remove a wall between two bedrooms ?
Paul P
Unfortunately I don't have any bedrooms next to each other.

Quote:
Originally Posted by Wes Lachot
Mesa,

There are a couple of aspects to your situation that haven't been considered yet, that I think are worth considering:

First, how solid are your walls? If these things are merely one layer of gypsum, the modal problems are not nearly as significant as if you have three layers of gypsum. Much of the bass goes right through the wall with only one layer, and that portion of the bass energy that's going through the wall is not going to be causing any modal build-up.
I'm not sure yet man. I'm pretty sure all stuff like that will be pretty typical. To be honest I'm not even sure what's typical.

Quote:
Next, what is your ceiling dimension? There's a fair chance it's eight feet, and if that's the case, then you've got an excellent ratio between the ceiling dimension and the wall dimensions. That would be 1 : 1.6 between the height and the length dimension, and 1 : 1.58 between the height and the width dimension. In other words, the "Golden Ratio".
I'm pretty sure they said it was 9 feet, but I could be wrong. I'll have to check with them again. They are starting to build the house now. Wish I had written all of this down so I wouldn't have to second guess myself but I never expected anyone to help to the level of needing specifics. Thanks again for that.

Quote:
Someone has mentioned that you could reduce one of the dimensions by roughly 5% to achieve non-squareness. This is true; it only takes about 5 or 6% to do this, which musically speaking is a semi-tone. But there's a problem with doing that, in this case:

The 1 : 1.6 ratio that exists between the ceiling dimension and (roughly) between the other two dimensions is, in musical terms, a minor 6th. That's good. But if you reduce the minor 6th by a semi-tone (6%), your minor 6th becomes a perfect 5th. That's not so good. In fact, that's very bad. You will have traded a unison for a perfect 5th. That's trading up, for sure, but not by much. A perfect 5th means that the two dimensional resonances will be only one key away from each other, and they will share many common harmonics. You want just the opposite - to spread the harmonics out into many unrelated keys, for musical balance.

The smart thing to do would be to bite the bullet and reduce the width by 12%, which would be a whole step. Now you'd have a diminished 5th ratio (1 : 1.4) between the height and the width. That would mean reducing the width of the room from 12'-8" to 11'-2".

There are those who would argue for keeping the room larger, reasoning that that would make for better acoustics for a room this size. I'm not in that camp. The extra foot and a half may have practical advantages, for sure, but acoustically speaking, at least to my ears, it's always best to have good ratios. I've tried it both ways. The bass is more balanced with good ratios, and as long as you don't shave the longest of your three dimensions, you aren't losing anything on the low end when you trim the room dimension slightly to achieve better ratios. But not everyone can hear it. Like I said at the beginning, with one layer of gypsum, it's a more subtle difference. But it's there.

-Wes
Damn man I had no idea we'd be getting into keyss and intervals etc. That pretty much blows my mind. I wouldn't mind shaving off that much of the room if it will make that big of a difference. Tell me though, is there any makeshift way to do this, or do I have to go all out and build an actual wall? Is there anything non-permanent I could do that would work?

Thanks for the help and all that info.
Old 14th November 2009
  #43
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Quote:
Originally Posted by jhbrandt View Post
Good point Wes, Thanks...

So I did some more calculations for our friend... Here are the charts from 143" to 134"......OMG, I wish all the studios that I design could be from the ground up.. ~sigh~

Anyway, Mesa, good luck with your room. Let me know how it turns out.
Thanks again for all the help man. I really do appreciate it. I'll let you know for sure. I've got about 3 months to get it figured out as that's when the house will be done. Can't wait! Thanks to you guys I won't be going in blind. I've learned a lot already.

Quote:
Originally Posted by Glenn Kuras
I can't remember a thread with so many experts chiming in. The poster sure did get his moneys worth on this one.
Wes it is great to see you around. Keep on posting!!!!!!!
I did completley luck out didn't I! I think they all followed you in! Thanks again everyone.

Quote:
Originally Posted by DanDan
Indeed Glenn, maybe this is our early Christmas Party........! Cheers.....:-)
I get the impression that Mesa has left the building though.
I'm still here! Internet went out yesterday at some point and didn't come back until midday today. I definately didn't expect to see all of this! Thanks!
Quote:
Originally Posted by DanDan
Some random points.
Wes, Hi, the ceiling is 9ft. I am hoping Mesa will come back tell us what are the Walls, Floor, Ceiling, made of? Brick would seriously escalate the modal problem in my mind. If we know the surface material and construction method, plus whether a wall shift or extra wall is on the menu, then we could move toward a consensus, which would be fun.
The walls will be typical drywall. Floors will be concrete with a fairly thick pad and carpet. Ceiling is the drywall stuff too. At least I assume it's drywall-esque haha. One of the outside walls bordering that room will be brick. The other is not brick. I think it's a siding type material on the windowed side.
There are definately no walls to take down but I'd be down for trying to build a wall to make a bette situation for myself. If I can make something non-permanent than it's a for sure go. If I have to do a real contractor job type wall then I'll have to see what it'll cost me before I can even know.

Quote:
Originally Posted by DanDan
Irrespective of that info, and irrespective of wall changes, here's my shot at treating this room specifically:-
The most Bass Trapping possible. There are three vertical corners available. Floor to ceiling 32inch wide SuperChunks in the three corners. MegaTraps might be even more powerful, perhaps they have a membrane? Panel Bass Traps at all available ceiling corners. A serious cloud, 3-4 inches thick with a membrane on the ceiling side. Side Reflecting panels, again thick, with membrane to the wall.
Optimise speaker and listening positions by measurement, including height. A substantial couch can have a useful trapping effect, as can large friends in red clothes with a 703 beard.
DD
DD
Hopefully I can still fit in the room with all that treatment! Luckily I already have the large friends with the 703 beards... but they don't usually where red clothes. Should I make them change or is the effect on the low end minimal??
Thanks again man. Much appreciated.
Old 14th November 2009
  #44
Lives for gear
 

Quote:
Originally Posted by Wes Lachot View Post
So if the ceiling is 9 ft. rather than 8 ft., that changes the calculations. Interestingly, we still have a good ratio between the height dimension and the width dimension (12.66 / 9 = 1.41). The ratio 1 : 1.41 is one of the good ones - a diminished 5th. And we're faced with a similar delimma as before, namely, if we reduce either the width or depth dimension by merely 6% (a semi-tone), we'll create a 1 : 1.33 ratio between that dimension and the height. This ratio ( 1 : 1.33, or a perfect 4th) is also one of the bad ones, although not quite as bad as 1 : 1.5. By instead reducing the width or depth dimension by a full whole step (12%) we can bring that ratio to a major 3rd, or 1 : 1.26, which is one of the very desirable ratios. So if the depth dimension were reduced to 11'-5", you'd have a great set of ratios, namely 1 : 1.26 : 1.41.

Note: as usual, some rounding has been applied for clarity and brevity's sake.

-Wes
I'm pretty sure it is 9, but I'm going to check tomorrow with the contractor just to make sure. All of this ratio stuff is so over my head. I had no idea such a small change could change that much about a room. I'll have to read up on some of this.

Thanks again!
Old 14th November 2009
  #45
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avare's Avatar
 

Congratulations on all the great help you are getting. One clarification please. You have written that your walls are typical. Typical what? You are posting to the world. You are receiving advice from three continents. "Typical" does not exist as anything meaningful across the world.

It would also help if you would update your profile to include your location, for obvious reasons from the paragraph above.

Andre
Old 14th November 2009
  #46
Gear Guru
 
Glenn Kuras's Avatar
Quote:
That would work? What type/amount of trapping would I need to put behind it? If this is possible that would be awesome because I'd like to avoid any permanent solutions if possible just because I would like to sell the house at some point!
You can use rigid fiber glass, mineral wool or pack in fluffy fiber glass.
Old 14th November 2009
  #47
Gear Guru
Storm

Mesa, a snowstorm of advice eh. Let's confirm that 9 foot detail in deference to the work put into calcs. Looking at your original diagram, and from your latest post, I am assuming the east wall is brick. Now that I know that, I am joining the recommendation to build a false wall. It is as simple as John described. Wooden stud frame, loosely fill with insulation, layer of plasterboard. It could give you an opportunity to build in some wiring, lights, screens, a fishtank! I don't have the practical experience to recommend any particular ratios, however I have run some of the recommended ones in my calculators here. I am fully convinced that any of the recommended wall shifts would be better than square, much better. In particular Wes final shot looks very good. I am not sure from John's post which wall is moving in and how much. Could you clarify that please John?
It would be great to finish this with a consensus. Wes and John, can we pull this together. Just to be clearly on the one page, are we all thinking this way:-
The speakers should be at the north window wall.
The false wall should be built over the east brick wall.
In this context could I ask you both to consider each others calcs and make your recommendations again?
It would be great if it ends up being the same number.

My thanks to all involved here, most of my work is remedial and construction is simply not on the menu. Thus I have not toyed with dimensions much. This exercise here has convinced me of the strong benefits possible by relatively small dimension changes. All good.

Best, DD

Last edited by DanDan; 14th November 2009 at 05:34 PM.. Reason: Details
Old 15th November 2009
  #48
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Quote:
Originally Posted by avare View Post
Congratulations on all the great help you are getting. One clarification please. You have written that your walls are typical. Typical what? You are posting to the world. You are receiving advice from three continents. "Typical" does not exist as anything meaningful across the world.

It would also help if you would update your profile to include your location, for obvious reasons from the paragraph above.

Andre
Haha yeah I guess you have a point. I'm in Houston, TX. I can't speak for any other continents but the drywall stuff is pretty common in the U.S. Profile updated. Thanks for the heads up!


Quote:
Originally Posted by Glenn Kuras
You can use rigid fiber glass, mineral wool or pack in fluffy fiber glass.
Are we talking about a full wall sized bass trap?



Quote:
Originally Posted by DanDan
Mesa, a snowstorm of advice eh. Let's confirm that 9 foot detail in deference to the work put into calcs. Looking at your original diagram, and from your latest post, I am assuming the east wall is brick. Now that I know that, I am joining the recommendation to build a false wall. It is as simple as John described. Wooden stud frame, loosely fill with insulation, layer of plasterboard. It could give you an opportunity to build in some wiring, lights, screens, a fishtank! I don't have the practical experience to recommend any particular ratios, however I have run some of the recommended ones in my calculators here. I am fully convinced that any of the recommended wall shifts would be better than square, much better. In particular Wes final shot looks very good. I am not sure from John's post which wall is moving in and how much. Could you clarify that please John?
It would be great to finish this with a consensus. Wes and John, can we pull this together. Just to be clearly on the one page, are we all thinking this way:-
The speakers should be at the north window wall.
The false wall should be built over the east brick wall.
In this context could I ask you both to consider each others calcs and make your recommendations again?
It would be great if it ends up being the same number.

My thanks to all involved here, most of my work is remedial and construction is simply not on the menu. Thus I have not toyed with dimensions much. This exercise here has convinced me of the strong benefits possible by relatively small dimension changes. All good.

Best, DD
I know right? I figured I'd get maybe a response or two. Definately not all of this. You guys really are awesome.

Yeah the East wall is brick. The Northern wall with windows is some sort of siding. I tried to get a hold of the builder today but couldn't reach them. I'm going to try again tomorrow but I'm assuming I won't be able to reach them to confirm the ceiling height until Monday unfortunately. I'm thinking a false wall is in my future. heh You guys are great. Thanks!
Old 15th November 2009
  #49
Gear Maniac
 
Marbarbaar's Avatar
 

Quote:
Originally Posted by Rick Sutton View Post
Is it even possible to get a square room, 12.5 x 12 x 9, to sound good for mixing?

Yes, it is not ideal, but it can work. For years I mixed in a 9x12 room.
By the way, 12.5 x 12 is not square. Close, but there is a bit of a difference (to your advantage IMO)
Fascinating (because my room is of similar proportions) How did that work out for you? I take it you used treatment?
Old 15th November 2009
  #50
Gear Nut
 

Quote:
Originally Posted by DanDan View Post
It would be great to finish this with a consensus. Wes and John, can we pull this together. Just to be clearly on the one page, are we all thinking this way:-
The speakers should be at the north window wall.
The false wall should be built over the east brick wall.
In this context could I ask you both to consider each others calcs and make your recommendations again?
It would be great if it ends up being the same number.
Best, DD
Looking at John's numbers, it's clear that at 152" the low frequency modes are horribly bunched up, with wide gaps between resonances. Then in the middle at 143", the gaps are still too large on at the low frequency end of the graph. At the other extreme (134"), the low frequency gaps look pretty good. My estimate of 137" is pretty close to that. So I'd say there's not much compromising that needs to be done to reconcile John's numbers with mine. We could split the difference at 135 1/2" and call it a day. As long as John is cool with my assessment of the situation, of course.

By the way, logarithmic graphs would make all of this even clearer to the eye (and more like it is to the ear). But the linear graphs are doing the job (thanks for those, John).

-Wes
Old 15th November 2009
  #51
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PaulP's Avatar
 

Mesa4x12er, are you saying that the brick is on the outside of the house ? If so I don't
see that it matters, much. I have a feeling some of us have been imagining
the brick on the inside, or I've read things wrong.

Paul P
Old 15th November 2009
  #52
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jhbrandt's Avatar
Quote:
Originally Posted by DanDan View Post
I am fully convinced that any of the recommended wall shifts would be better than square, much better. In particular Wes final shot looks very good. I am not sure from John's post which wall is moving in and how much. Could you clarify that please John?
It would be great to finish this with a consensus. Wes and John, can we pull this together. Just to be clearly on the one page, are we all thinking this way:-
The speakers should be at the north window wall.
The false wall should be built over the east brick wall.
In this context could I ask you both to consider each others calcs and make your recommendations again?
It would be great if it ends up being the same number.
good idea, Dan, Thanks.

Yes and Yes the false wall on the east.

I've read up on Wes's ...Musical Scales in Sound Rooms... and I think we're close. -- (I'm also doing a lot of research and reading papers on Constrained Layer Damping as in Green Glue - of which earlier I was very skeptical. - still a skeptic until I can see the data for below 125Hz - but that's another thread...)

Wes, I'm going to see if I can't add to my spreadsheet calc your 'musical ratios' to see where things fall each time they are calculated.-- I'll post a link on my signature later when I get it finished & uploaded. thumbsup

Okay, my recommendation is to make the room 12' 1" by 12' 10" by 9' which is a ratio of: 1.34 (W) by 1.43 (D) by 1 (H)
The Primary modes will be:
Axial = 44.0 F, 46.8 F#, ,62.8 B Tangential = 64.2 C, 76.7 D# -, 78.3 D# +, Oblique = 89.8 F, 117.8 Bb, 120.9 B -, These are only the primaries mind you...

Not too bad, IMO for a small room. What do you think, Wes?
-- John
Old 15th November 2009
  #53
Gear Nut
 

Quote:
Originally Posted by jhbrandt View Post

Okay, my recommendation is to make the room 12' 1" by 12' 10" by 9' which is a ratio of: 1.34 (W) by 1.43 (D) by 1 (H)
The Primary modes will be:
Axial = 44.0 F, 46.8 F#, ,62.8 B Tangential = 64.2 C, 76.7 D# -, 78.3 D# +, Oblique = 89.8 F, 117.8 Bb, 120.9 B -, These are only the primaries mind you...

Not too bad, IMO for a small room. What do you think, Wes?
-- John
I think it's far better than the original square room. The spacing between the three primary axials could be improved, in my opinion, by moving the F# up to G. That would get rid of the perfect 4th (4 : 3) relationship between the width and the height dimensions. A 4 : 3 relationship means that the 4th harmonic of the width will resonate with the 3rd harmonic of the height, resulting in a double resonance at 188 Hz.

By reducing the width a few more inches so that the primary width axial is at 50 Hz, we'd have a situation where the first double resonance between the width dimension and the height dimension would be the 4th harmonic of the width resonating with the 5th harmonic of the height, since there would now be a 5 : 4 relationship between them (major 3rd). This double resonance would be at 250 Hz, which is noticeably better than the previous example (where the first double resonance occurred at 188 Hz). The further up into the midrange these problems can be pushed, the easier it is to treat them with traditional room treatments.

An added benifit is that the 5 : 4 ( major third) ratio is exactly one third of the way around the Circle of 5ths, meaning that all of the higher harmonics would be more evenly distributed throughout the various musical keys, not just the primary harmonics.

It's worth noting that I give highest priority to the axial resonances, secondary priority to tangential resonances, and lowest priority to oblique resonances. This makes sense to me due to the far greater wall surface area available to the axials.

However, there is a tradeoff of a few inches of room space, and whether the sound difference would be enough to justify the reduced space for a given client is an open question. I tend to go for the more misically pure solutions since these are sound rooms, after all.

-Wes
Old 15th November 2009
  #54
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Quote:
Originally Posted by Wes Lachot View Post
I think it's far better than the original square room. The spacing between the three primary axials could be improved, in my opinion, by moving the F# up to G...
If anyone else is facinated by this discussion of interval ratios here's an
excerpt from a book on the subject (click on the blue arrow in the box
to expand the text) :
Music, physics and engineering
The many pages that follow contain all the notes, intervals and their ratios.

I take it we're more interested in just intonation when we talk about rooms
as musical instruments and that we priviledge dissonnant intervals for the
ratios ?

Paul P
Old 15th November 2009
  #55
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Quote:
I've read up on Wes's ...Musical Scales in Sound Rooms... and I think we're close. -- (I'm also doing a lot of research and reading papers on Constrained Layer Damping as in Green Glue - of which earlier I was very skeptical. - still a skeptic until I can see the data for below 125Hz - but that's another thread...)
On the GG site you have tons of lab measurements, they go from 80 Hz up
Old 15th November 2009
  #56
Gear Nut
 

Quote:
Originally Posted by PaulP View Post
I
I take it we're more interested in just intonation when we talk about rooms
as musical instruments and that we priviledge dissonnant intervals for the
ratios ?

Paul P
The reason I use just intonation intervals for discussion purposes is simply that they are easy to represent as whole number ratios. A just intonation perfect 5th is simply a 3 : 2 ratio, whereas an equal termpered perfect 5th is the 12th root of 2 raised to the 7th power. See what I mean? You lose a lot of people talking about equal tempered intervals.

And the truth is, it doesn't really matter anyway. I'm not saying that all room ratios should be tuned to musical intervals per se. What I am saying is that the 12 musical divisions of the octave are the easiest and best way to discuss and work with room ratios because 1) the 12 tones represent a logarithmic division of the 2 : 1 (octave) ratio, which is more useful than a linear division, and 2) we are, after all, talking about creating rooms for musical listening and production, so I feel it helps to work within a musical context when designing and creating these rooms.

So while I may start out with a just major third ratio between height and width ( 1 : 1.25), I always feel free to move that to the equal tempered 3rd ( 1 : 1.26) if it helps to bring the numbers into balance. The bass waves aren't going to notice an inch here or there, but they will respond to a change from a perfect 5th to a diminished 5th, let's say. So, in other words, a 1 : 1.4 ratio is good (just intonation), a 1 : 1.414 ratio is good ( equal temperament), but a 1 : 1.5 interval (or it's equal tempered counterpart) is bad.

As to your other question about dissonant intervals being better than consonant ones, I would say the answer to that is a bit more nuanced. If we define consonance as Harry Partch ( and others) have, then the simpler the whole number ratio, the more consonant the ratio. So the most consonant ratio is 1 : 1, followed by 2 : 1, 3 : 2, 4 : 3, 5 : 4, etc. I think this is a reasonable definition, since many musicians, mathematicians, and golden ears have tended to agree on this point for centuries.

I would agree that it's best to avoid the very consonant, low integer ratios for room dimensions for obvious reasons. A 1: 1 or 2 : 1 ratio is going to get you into obvious trouble. But a 5 : 4 ratio is actually a very good ratio, for instance. That's because it happens to be approximately one third of the way around the Circle of 5ths, and lends very even spacing to the lowest axial modes, as well as distributing the modal harmonics evenly throughout the musical keys.

So the best way I can briefly state it is to say this: Very low low integer ratios are to be avoided, but other simple integer ratios can be used to create intentionally "musical" spacing of the modal resonances.

-Wes
Old 15th November 2009
  #57
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Quote:
Originally Posted by Wes Lachot View Post
So the best way I can briefly state it is to say this: Very low low integer ratios are to be avoided, but other simple integer ratios can be used to create intentionally "musical" spacing of the modal resonances.
I'm fairly new to acoustics and I must say this is the first I've heard anything
about this way of looking at things. More studying to do ! It has never
occured to me that given the proper ratios I could get my room to boom a
G chord . Not that I'd want to, but it's interesting to think of the modes
as notes and not just abstract problem frequencies.

Paul P
Old 15th November 2009
  #58
Gear Guru
Survey

I have quite a collection of Room Mode Calculators here. I took this opportunity to check them out, dump a few, elevate a few. The one I mentioned earlier seems to work really well.
It is very easy to use and visually shows the good the bad and the ugly quite distinctly. It was originally written by knightfly over at john sayers forum. It is so simple that one might overlook how great it is. I like it so much that I have brazenly stolen it and tweaked it for easier viewing and use. I also did a Metric version. I hope y'all will enjoy these.
RoomTune DD.xls
RoomTune DD Metric.xls
I ran the numbers in all of my calculators. There is a broad area of agreement that from 11ft to 11ft 6 inches is good.
I must say this musical interval viewpoint is new to me, very attractive, and makes sense due to the log/close to nature thing. Nice one Wes, I too will be reading.
On my travels I found this roomsizer.pdf
I am sure the authors won't mind us borrowing it. It describes a computer program which tries many combinations of dimensions, applying new sophisticated criteria to get the flattest frequency response. Hopefully someday we may see that program.

DD

Last edited by DanDan; 16th November 2009 at 01:26 AM.. Reason: More
Old 15th November 2009
  #59
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PaulP's Avatar
 

I just located Wes's paper on his website :
Architectural and Music Scales in Sound Room Design
Haven't read it yet but it looks interesting.

Paul P
Old 17th November 2009
  #60
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To anyone that was wondering/asking... the ceilings are confirmed at 9ft.
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