Now I've decided to improve my room, new walls, bass traps, dead celing..
I've read some about this and it seems like most of you are considering a hard floor (wood, concrete, linolium) to be the best thing to keep the room alive.
The Celing should be very well isolated, the more the better...
I'm thinking about constructing thin wood stripes running 7 inches down holding up Rigid fiberglass and leaving a few inches air between the fiber and the celing.
I will construct new walls made of wooden slats (bound together with 3 cross boards) 1 inch apart from each other.
Between this wall and the existing concrete wall I will hang more rigid fiber but I´m not sure how far from the woodwall? As I understand it the more distance from the original wall the better..right?
Finally I will add a Bass trap in each corner built this way
http://europa.spaceports.com/~fishbake/ ... sstrap.htm
The room has I pretty bad shape for a recording room i suspect? .. Here is my whole plan
www.lenaleierth.com/studioplan.gif
Tips and help are more then welcome / Stefan
help building studio
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
Steefann, first of all, welcome to the forum -
It would help if we knew what you plan to do in the room - is it just for drum practice, or are you planning to record in it too? Is there another room, or is this room going to be everything?
Your wall idea is kind of a cross between high bass trapping and slat resonators; calculated as slot resonators, your entire walls would absorb most at around 600-700 hZ, which would give your room kind of a low, hollow sound - not the best idea for a large area treatment. Also, that much "live" surface in the form of the 4" slats would tend to make problems with early reflections if you're planning to record and mix in there.
The ceiling idea sounds OK for almost any acoustic use of the room.
Yes, the further from the wall you put absorptive material, the lower frequencies will be absorbed. Keep in mind, though, that in order to absorb low bass frequencies equally the material would need to be about 8-9 feet (3 meters) off the wall. Not too practical for a room that's less than about 20 meters across...
Also, you're correct that the shape could be better - square is not ideal for acoustics. Here is a mode plot of your room, assuming (you didn't mention) that the ceiling is at 8 feet (244 cm) Note the adjacent bars on the graph that are the same height - this is not good, and is caused by the square room. Better would be if they were all different but not too different. This can only be changed by different room dimensions, so treatment becomes the only help here.
There are better ways to handle this shape room, but I need to know what your plans are for its use - How about some more thoughts on that? Steve
It would help if we knew what you plan to do in the room - is it just for drum practice, or are you planning to record in it too? Is there another room, or is this room going to be everything?
Your wall idea is kind of a cross between high bass trapping and slat resonators; calculated as slot resonators, your entire walls would absorb most at around 600-700 hZ, which would give your room kind of a low, hollow sound - not the best idea for a large area treatment. Also, that much "live" surface in the form of the 4" slats would tend to make problems with early reflections if you're planning to record and mix in there.
The ceiling idea sounds OK for almost any acoustic use of the room.
Yes, the further from the wall you put absorptive material, the lower frequencies will be absorbed. Keep in mind, though, that in order to absorb low bass frequencies equally the material would need to be about 8-9 feet (3 meters) off the wall. Not too practical for a room that's less than about 20 meters across...
Also, you're correct that the shape could be better - square is not ideal for acoustics. Here is a mode plot of your room, assuming (you didn't mention) that the ceiling is at 8 feet (244 cm) Note the adjacent bars on the graph that are the same height - this is not good, and is caused by the square room. Better would be if they were all different but not too different. This can only be changed by different room dimensions, so treatment becomes the only help here.
There are better ways to handle this shape room, but I need to know what your plans are for its use - How about some more thoughts on that? Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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steefann
- Posts: 10
- Joined: Wed Aug 06, 2003 8:13 am
- Location: sweden
Ok, here is my plan
Thanks Steve!
I'm using the room(s) right now for recording, the window on the drawing leads to the controlroom that is just a little bit smaller. I've built a wood panel over glassfiber on the walls and the celing, not super but it works really good for me. I think I can do I pretty good job in there.
My biggest problem right now is the recording room and right now I've basicly just squeezed fiberglass and junk up the walls and a few absorbers (the general ones used in schools in Sweden) to the celing that is pure concrete.
The floor is covered with a pretty thick carpet but I've learned it will not stop the bass as no carpet is that thick. That leaves me with a lot of bass that probably are bouncing happily up and down
Most of my material comes out pretty muddy and I have to fight it with lots of eq. The main problem is recording drums, they don't come out as focust as I would like , especially not the bass and the low mid... to be honest not at all.
My goal is to build a room that is more focused, but not dead.
It's a bit hard for me to understand all the terms cause this is certainly not simple school english and most material don't share the same name.
You wrote that my plan would probably result in a kind of "dark" room and that is certainly not what I'm trying to create. To make it simple... I need a room that works good for drums.
....And you were almost right about the celing, It is 220 cm, kind of low but I read it would be a good Idea to put glassfiber right to the celing and then leave a 4" air gap (or as big as you can afford) and then another layer of fiber. It would make the celing pretty low but ,as Nathan wrore, a totaly dead celing=infinit hight... right?
I do not need more then 195 cm for overhead mics but I suspect it is not that good to place them close to the fiber no matter how thick it is.
I'm totaly new at this so If you have any suggestions, even if they are miles away from my plan, I would love to hear them / Best regards Stefan
I'm using the room(s) right now for recording, the window on the drawing leads to the controlroom that is just a little bit smaller. I've built a wood panel over glassfiber on the walls and the celing, not super but it works really good for me. I think I can do I pretty good job in there.
My biggest problem right now is the recording room and right now I've basicly just squeezed fiberglass and junk up the walls and a few absorbers (the general ones used in schools in Sweden) to the celing that is pure concrete.
The floor is covered with a pretty thick carpet but I've learned it will not stop the bass as no carpet is that thick. That leaves me with a lot of bass that probably are bouncing happily up and down
Most of my material comes out pretty muddy and I have to fight it with lots of eq. The main problem is recording drums, they don't come out as focust as I would like , especially not the bass and the low mid... to be honest not at all.
My goal is to build a room that is more focused, but not dead.
It's a bit hard for me to understand all the terms cause this is certainly not simple school english and most material don't share the same name.
You wrote that my plan would probably result in a kind of "dark" room and that is certainly not what I'm trying to create. To make it simple... I need a room that works good for drums.
....And you were almost right about the celing, It is 220 cm, kind of low but I read it would be a good Idea to put glassfiber right to the celing and then leave a 4" air gap (or as big as you can afford) and then another layer of fiber. It would make the celing pretty low but ,as Nathan wrore, a totaly dead celing=infinit hight... right?
I do not need more then 195 cm for overhead mics but I suspect it is not that good to place them close to the fiber no matter how thick it is.
I'm totaly new at this so If you have any suggestions, even if they are miles away from my plan, I would love to hear them / Best regards Stefan
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
After looking again at the axial modes of your room, I can understand what the majority of your problem is coming from.
Not only are a lot of highs being sucked out by the heavy carpet, but you have ALL THREE axial modes combining at 156 hZ in one combination of harmonics. This standing wave, if all three coordinates of either instrument or mic coincide, could cause either a huge dip or a huge peak in response at that frequency. Neither would be good. I'll bet that right now, with someone else playing the drums, you could find at least a 20 dB swing in level at 150 hZ just by moving the mic up, down, left, right, or anywhere.
The first thing I think you need to do is to get rid of the carpet - if you can't do that, then cover it with wood like you did the drum riser.
The next thing you need to do is build some of John's SIDE WALL ABSORBER slat absorbers, the drawings are here
http://www.johnlsayers.com/HR/index1.htm
Only, you should change the depth dimensions from 200 mm to 350 mm, from 50 mm to 100 mm, use your 1x4 slats but space them 2mm apart (this needs to be quite accurate, a small change in slot width at these values will change the frequency quite a bit) - If you can get twice as thick slats (38mm) you could increase the slot width between them to 3-4mm and it would be easier to build. I would build at least 4 of these in the size shown, and place them opposite each other as I show in the marked up version of your room drawing.
These side wall absorbers will help flutter echo, minimise early reflections back into your drum mics (which will clean up SOME of the phasing problems you're most likely calling "mud") and absorb a lot of the excess 150 hZ range caused by your room's modal problems.
I would forget about slat walls other than that, because you're only going to cause another dip in room response at around 600 hZ. Since room responses are not consistent throughout the room, no amount of EQ will compensate for them. One slight movement of a mic will start your problems all over again.
Once you get these things done to the room, it's time to cover mic/instrument placing. Even with the improvements to your room, there will still be places that neither a mic nor a drum nor any other instrument should be placed. These places will generally follow the pattern of dimensions that are evenly divided into your room dimensions. For example, you should never have either an instrument or a mic at 1/2, 1/3, 1/4, 1/5, etc, of ANY room dimension. (This isn't as bad in a splayed room as it is in a parallel walled room.)If your ceiling is at 220 cm, for example, don't think you'll get good results placing anything at 110 cm, 73, 55, 44 cm - those are all harmonics of the prime mode caused by your ceiling height. Same goes for length and width.
With the exception of VOLUME, never put a mic where your EAR doesn't like the sound. Don't expect your drums to record well if you can't stand the sound of them in the room. Don't play them un-tuned, with rattly hardware, unevenly tensioned heads, squeaky pedals, etc -
If you're getting too much tom in the overheads, raise the cymbals and overheads. If too much cymbal, lower the cymbals but NOT the overheads. If you learn to balance distances, a lot of drum tracks can be made with just a pair of overheads and a kick mic. Probably a snare mic too. Simple is sometimes better, but it's easier to try simple FIRST.
Phasing problems with overheads can be caused with as little as 1/8" movement in one mic relative to the other, if you're using an XY pair. Phasing can smear things and lose highs for you. This is why, right after I bought one of those "XY bars" for overheads, I promptly threw away the flimsy little sheet metal leaves (3 of them) and fabbed a new set out of 30mm x 3.5mm stainless steel bar. All I kept were the joint hardware and the mic stand adapter, then I added a pair of Shure Integral Shock mounts. I can adjust one mic with respect to the other by as little as a few thousanths of an inch. Cool...
If you use too many mics, you increase the chance that one of them will phase cancel another, and only at certain frequencies. Reversing the polarity of a snare mic versus the batter head mic will only get you close. You need delay control on the board (or a micrometer) to finish aligning the phase of the pair once you've set them. Too many mics too close together will GUARANTEE phasing problems - these can NOT be fixed with EQ, only changed.
I need to go for now, but I hope I've given you some ideas that will help you improve your room and your recordings - Always feel free to come back and question (or argue) anything - I find that I always learn more by arguing (peaceably) than almost any other way... Steve
Not only are a lot of highs being sucked out by the heavy carpet, but you have ALL THREE axial modes combining at 156 hZ in one combination of harmonics. This standing wave, if all three coordinates of either instrument or mic coincide, could cause either a huge dip or a huge peak in response at that frequency. Neither would be good. I'll bet that right now, with someone else playing the drums, you could find at least a 20 dB swing in level at 150 hZ just by moving the mic up, down, left, right, or anywhere.
The first thing I think you need to do is to get rid of the carpet - if you can't do that, then cover it with wood like you did the drum riser.
The next thing you need to do is build some of John's SIDE WALL ABSORBER slat absorbers, the drawings are here
http://www.johnlsayers.com/HR/index1.htm
Only, you should change the depth dimensions from 200 mm to 350 mm, from 50 mm to 100 mm, use your 1x4 slats but space them 2mm apart (this needs to be quite accurate, a small change in slot width at these values will change the frequency quite a bit) - If you can get twice as thick slats (38mm) you could increase the slot width between them to 3-4mm and it would be easier to build. I would build at least 4 of these in the size shown, and place them opposite each other as I show in the marked up version of your room drawing.
These side wall absorbers will help flutter echo, minimise early reflections back into your drum mics (which will clean up SOME of the phasing problems you're most likely calling "mud") and absorb a lot of the excess 150 hZ range caused by your room's modal problems.
I would forget about slat walls other than that, because you're only going to cause another dip in room response at around 600 hZ. Since room responses are not consistent throughout the room, no amount of EQ will compensate for them. One slight movement of a mic will start your problems all over again.
Once you get these things done to the room, it's time to cover mic/instrument placing. Even with the improvements to your room, there will still be places that neither a mic nor a drum nor any other instrument should be placed. These places will generally follow the pattern of dimensions that are evenly divided into your room dimensions. For example, you should never have either an instrument or a mic at 1/2, 1/3, 1/4, 1/5, etc, of ANY room dimension. (This isn't as bad in a splayed room as it is in a parallel walled room.)If your ceiling is at 220 cm, for example, don't think you'll get good results placing anything at 110 cm, 73, 55, 44 cm - those are all harmonics of the prime mode caused by your ceiling height. Same goes for length and width.
With the exception of VOLUME, never put a mic where your EAR doesn't like the sound. Don't expect your drums to record well if you can't stand the sound of them in the room. Don't play them un-tuned, with rattly hardware, unevenly tensioned heads, squeaky pedals, etc -
If you're getting too much tom in the overheads, raise the cymbals and overheads. If too much cymbal, lower the cymbals but NOT the overheads. If you learn to balance distances, a lot of drum tracks can be made with just a pair of overheads and a kick mic. Probably a snare mic too. Simple is sometimes better, but it's easier to try simple FIRST.
Phasing problems with overheads can be caused with as little as 1/8" movement in one mic relative to the other, if you're using an XY pair. Phasing can smear things and lose highs for you. This is why, right after I bought one of those "XY bars" for overheads, I promptly threw away the flimsy little sheet metal leaves (3 of them) and fabbed a new set out of 30mm x 3.5mm stainless steel bar. All I kept were the joint hardware and the mic stand adapter, then I added a pair of Shure Integral Shock mounts. I can adjust one mic with respect to the other by as little as a few thousanths of an inch. Cool...
If you use too many mics, you increase the chance that one of them will phase cancel another, and only at certain frequencies. Reversing the polarity of a snare mic versus the batter head mic will only get you close. You need delay control on the board (or a micrometer) to finish aligning the phase of the pair once you've set them. Too many mics too close together will GUARANTEE phasing problems - these can NOT be fixed with EQ, only changed.
I need to go for now, but I hope I've given you some ideas that will help you improve your room and your recordings - Always feel free to come back and question (or argue) anything - I find that I always learn more by arguing (peaceably) than almost any other way... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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steefann
- Posts: 10
- Joined: Wed Aug 06, 2003 8:13 am
- Location: sweden
Ok Steve, lets see if I got it right here And Thanks again!!
You mean that I should put heavy absorption on the walls... rigid fiberglass placed at a 10-20 cm distance from the concrete walls but not a outer wall made of slats. Same goes for the celing. When you write "heavy" do you mean as heavy as I can afford or just a layer of 5-10 cm rigid fiberglass hanging at a distance from the wall?
In the corners there should still be bass traps, probably and the ones I suggested is Ok? Any better models?
Only, you should change the depth dimensions from 200 mm to 350 mm, from 50 mm to 100 mm, use your 1x4 slats but space them 2mm apart (this needs to be quite accurate, a small change in slot width at these values will change the frequency quite a bit) - If you can get twice as thick slats (38mm) you could increase the slot width between them to 3-4mm and it would be easier to build. I would build at least 4 of these in the size shown, and place them opposite each other as I show in the marked up version of your room drawing.
Sounds great, I got a few questions..
I asume "slats" are "wooden slats"? , Not very used to all those terms
What is MDF.. plywood or is there some "International" material called MDF?
The drawings never really tell what is on the top and bottom of the side wall absorbers, since he writes "The only access to the outer air is via the gaps between the slats." i asume i put MDF there to?
The "insulation" is that 5 cm rigid fiberglass ?
/ Best Regards Stefan
And Thanks again!!You mean that I should put heavy absorption on the walls... rigid fiberglass placed at a 10-20 cm distance from the concrete walls but not a outer wall made of slats. Same goes for the celing. When you write "heavy" do you mean as heavy as I can afford or just a layer of 5-10 cm rigid fiberglass hanging at a distance from the wall?
In the corners there should still be bass traps, probably and the ones I suggested is Ok? Any better models?
Only, you should change the depth dimensions from 200 mm to 350 mm, from 50 mm to 100 mm, use your 1x4 slats but space them 2mm apart (this needs to be quite accurate, a small change in slot width at these values will change the frequency quite a bit) - If you can get twice as thick slats (38mm) you could increase the slot width between them to 3-4mm and it would be easier to build. I would build at least 4 of these in the size shown, and place them opposite each other as I show in the marked up version of your room drawing.
Sounds great, I got a few questions..
I asume "slats" are "wooden slats"? , Not very used to all those terms
What is MDF.. plywood or is there some "International" material called MDF?
The drawings never really tell what is on the top and bottom of the side wall absorbers, since he writes "The only access to the outer air is via the gaps between the slats." i asume i put MDF there to?
The "insulation" is that 5 cm rigid fiberglass ?
/ Best Regards Stefan
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
Stefan, your questions (in order asked) -
"as heavy as I can afford or just a layer of 5-10 cm rigid fiberglass hanging at a distance from the wall?" -
*A layer of 5-10 cm spaced off the wall is fine. Be sure to cover all rigid fiberglas with cloth, and vacuum clean everything in the room (wearing a dust mask) when you're finished.
"In the corners there should still be bass traps, probably and the ones I suggested is Ok? Any better models?" -
*The basic corner design is OK, but again I would forget about the slats in front. Any time you use slats spaced like that, especially if the box is sealed so that the gaps between the slats are the only way in or out of the box, you've just created a Helmholz resonator, also called a Slat Resonator, also called a Slot Resonator. When you do that, you should know what range of frequencies you are affecting, and without calculations you won't know that.
Besides, you need overall bass absorption in the corners, not just one frequency range. You can create a simple bass trap simply by placing a thick (75-100 mm) piece of rigid fiberglas diagonally across the corner. It doesn't even have to be sealed, it will still work. It will work BETTER if there is also absorbent INSIDE the triangle that is created by placing the rigid fiberglas across the corner.
"I asume "slats" are "wooden slats"? " -
*Right, the same ones you were planning to put on the walls all around the room. I'm assuming from your description that they are what I would call 1 x 4, which should be about 19mm by 90mm. I've attached a side view drawing with more explanation of terms.
"What is MDF.. plywood or is there some "International" material called MDF?" -
*Not sure how "International" the term is, but it stands for Medium Density Fiberboard. It is sold in sheets like plywood, but is made by mixing a slurry of small wood chips and binder (glue) and then pressing this into sheets under several TONS of pressure. The result is a dense, heavy board that has enough mass not to vibrate easily. It is used in the manufacture of speaker boxes a lot. It is similar to a product called Particle Board, except that Particle board is lower density, sometimes referred to as LDF or Low Density Fiberboard.
"The drawings never really tell what is on the top and bottom of the side wall absorbers, since he writes "The only access to the outer air is via the gaps between the slats." i asume i put MDF there to?" -
*That's correct. The final result should be a sealed box, with the only access in or out being through the slots between the slats (boards) across the front.
"The "insulation" is that 5 cm rigid fiberglass ?" -
*Correct. However, the design would work better if the insulation were placed closer to the front slats and parallel to them - this would broaden the response somewhat, which would sound more natural by not affecting as narrow a range of frequencies.
Hope that helped... Steve
"as heavy as I can afford or just a layer of 5-10 cm rigid fiberglass hanging at a distance from the wall?" -
*A layer of 5-10 cm spaced off the wall is fine. Be sure to cover all rigid fiberglas with cloth, and vacuum clean everything in the room (wearing a dust mask) when you're finished.
"In the corners there should still be bass traps, probably and the ones I suggested is Ok? Any better models?" -
*The basic corner design is OK, but again I would forget about the slats in front. Any time you use slats spaced like that, especially if the box is sealed so that the gaps between the slats are the only way in or out of the box, you've just created a Helmholz resonator, also called a Slat Resonator, also called a Slot Resonator. When you do that, you should know what range of frequencies you are affecting, and without calculations you won't know that.
Besides, you need overall bass absorption in the corners, not just one frequency range. You can create a simple bass trap simply by placing a thick (75-100 mm) piece of rigid fiberglas diagonally across the corner. It doesn't even have to be sealed, it will still work. It will work BETTER if there is also absorbent INSIDE the triangle that is created by placing the rigid fiberglas across the corner.
"I asume "slats" are "wooden slats"? " -
*Right, the same ones you were planning to put on the walls all around the room. I'm assuming from your description that they are what I would call 1 x 4, which should be about 19mm by 90mm. I've attached a side view drawing with more explanation of terms.
"What is MDF.. plywood or is there some "International" material called MDF?" -
*Not sure how "International" the term is, but it stands for Medium Density Fiberboard. It is sold in sheets like plywood, but is made by mixing a slurry of small wood chips and binder (glue) and then pressing this into sheets under several TONS of pressure. The result is a dense, heavy board that has enough mass not to vibrate easily. It is used in the manufacture of speaker boxes a lot. It is similar to a product called Particle Board, except that Particle board is lower density, sometimes referred to as LDF or Low Density Fiberboard.
"The drawings never really tell what is on the top and bottom of the side wall absorbers, since he writes "The only access to the outer air is via the gaps between the slats." i asume i put MDF there to?" -
*That's correct. The final result should be a sealed box, with the only access in or out being through the slots between the slats (boards) across the front.
"The "insulation" is that 5 cm rigid fiberglass ?" -
*Correct. However, the design would work better if the insulation were placed closer to the front slats and parallel to them - this would broaden the response somewhat, which would sound more natural by not affecting as narrow a range of frequencies.
Hope that helped... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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steefann
- Posts: 10
- Joined: Wed Aug 06, 2003 8:13 am
- Location: sweden
Ok
Called a local dealer today to check how much money I have to spend.
In Sweden we do not have the Rigid fiber i read about on this forum (705..703..).
For now I have two choises..
1. Rockwool, 170mm = 70$, 95 mm= 40$ (m2)
2. Echophon 40mm = 300$ (m2)
I first thought Echophon must be much better but than a carpenter told me It will not be able to stop the low bass cause it has to low density if it is just 40mm. 170 mm Rockwool probably would, they claimed it worked just as good as studio material.
Steve...Do you know anything about those materials?
For the moment I am doing more exact drawings to know what to buy and how much of it.
After looking at my room drawing I can not help thinking that it looks very hard insulated. The only "reflecting" areas are the side wall absorber and the floor. The Celing and the walls are supposed to be as dead as possible, don't I need some high-freq reflectors or something?... not that I don't trust you
Called a local dealer today to check how much money I have to spend.
In Sweden we do not have the Rigid fiber i read about on this forum (705..703..).
For now I have two choises..
1. Rockwool, 170mm = 70$, 95 mm= 40$ (m2)
2. Echophon 40mm = 300$ (m2)
I first thought Echophon must be much better but than a carpenter told me It will not be able to stop the low bass cause it has to low density if it is just 40mm. 170 mm Rockwool probably would, they claimed it worked just as good as studio material.
Steve...Do you know anything about those materials?
For the moment I am doing more exact drawings to know what to buy and how much of it.
After looking at my room drawing I can not help thinking that it looks very hard insulated. The only "reflecting" areas are the side wall absorber and the floor. The Celing and the walls are supposed to be as dead as possible, don't I need some high-freq reflectors or something?... not that I don't trust you
Last edited by steefann on Fri Aug 08, 2003 6:52 am, edited 1 time in total.
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giles117
- Senior Member
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- Joined: Sat Jun 21, 2003 2:42 am
- Location: Henderson County
- Contact:
Rockwool is a trade name for Mineral Wool. That is what I put in my slats. It's dense like 703, just more "environmentally safe"
The Mineral wool/Rock Wool, AFB I purchase was 4pcf, whereas 703 is 3pcf and 705 is 5pcf respectively, hence the last number in the designation.
So Rock wool is a proper substitute in those walls and absorbers.
703/705 is sturdier than rockwool so it works well in an exposed situation like the bass traps or the cloth covered absorbers.
Bryan Giles
The Mineral wool/Rock Wool, AFB I purchase was 4pcf, whereas 703 is 3pcf and 705 is 5pcf respectively, hence the last number in the designation.
So Rock wool is a proper substitute in those walls and absorbers.
703/705 is sturdier than rockwool so it works well in an exposed situation like the bass traps or the cloth covered absorbers.
Bryan Giles
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steefann
- Posts: 10
- Joined: Wed Aug 06, 2003 8:13 am
- Location: sweden
Ok, thanks!
Regarding the price I thought swedish kronor... should be 4$ , not 40$.
it is sure expensive here but not THAT expensive
Does this mean that 4" of rockwool absorbs 86% of the 125Hz Bass, all the freq (111%) around 250 and so forth......?
Material
125Hz 250Hz 500Hz 1000Hz 2000Hz 4000HZ NRC
rockwool 4" 0.86 1.11 1.20 1.07 1.08 1.07 1.10
Regarding the price I thought swedish kronor... should be 4$ , not 40$.
it is sure expensive here but not THAT expensive
Does this mean that 4" of rockwool absorbs 86% of the 125Hz Bass, all the freq (111%) around 250 and so forth......?
Material
125Hz 250Hz 500Hz 1000Hz 2000Hz 4000HZ NRC
rockwool 4" 0.86 1.11 1.20 1.07 1.08 1.07 1.10
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
OK, first of all Bryan - I made the same mistake you did in assuming that the last digit in the 700 series indicated the PCF - it does in MOST cases, but the 705 is really 6 PCF, not 5. (not that it matters, since stefan can't get it...
Stefan, the 95 mm Rockwool will be fine - if they know the answer, you want a material that is 2.5 to 3 Pounds per Cubic Foot, or 40-45 kg per Cubic Meter density. That stuff can be used inside a wall to improve sound proofing, or on top (covered with cloth or burlap) to improve acoustics such as for bass traps, slot absorbers, general wall absorption, etc -
As to your doubts on all the absorption - If you do it in this order you won't overdo -
1. Get rid of the carpet. I wouldn't just put wood over it for any length of time, you'll grow mites and bugs under there.
2. Build the slant-faced slat absorbers I mentioned. Get them in place. Listen. Move them around to places that seem like a good idea. Listen again. When you like them the best, play some well-recorded CD
's through the system and listen. If they sound good, you're done. If not, analyze what's wrong and, if it's still too live, add absorption. Try not to put absorption on the same part of opposite walls.
"Does this mean that 4" of rockwool absorbs 86% of the 125Hz Bass, all the freq (111%) around 250 and so forth" -
Yes and no. Companies that don't correct their absorption readings for the "edge effect" will often show absorption rates above 1.00 - this isn't even possible, since theoretically 1.0 is TOTAL absorption.
What happens is, during testing the material is tested in standard size pieces, and for some reason one of the dimensions is 9 feet - there are a lot of edge surfaces on a 9 foot sample, and they "skew" the results so as to show more absorption than the material could absorb if it had no edges.
I usually re-adjust ALL the absorption values a company gives, DOWNWARD until the highest absorption value = one. That same value difference is subtracted from ALL the values, and that gives you a more real world idea of what the stuff can do.
If, however, you're cutting the same material into smaller pieces and scattering them around the room, standard formulae for figuring out the Sabins of absorption won't work because of the edge effect I mentioned earlier.
See, nice simple stuff we're playing with, huh??!? Steve
Stefan, the 95 mm Rockwool will be fine - if they know the answer, you want a material that is 2.5 to 3 Pounds per Cubic Foot, or 40-45 kg per Cubic Meter density. That stuff can be used inside a wall to improve sound proofing, or on top (covered with cloth or burlap) to improve acoustics such as for bass traps, slot absorbers, general wall absorption, etc -
As to your doubts on all the absorption - If you do it in this order you won't overdo -
1. Get rid of the carpet. I wouldn't just put wood over it for any length of time, you'll grow mites and bugs under there.
2. Build the slant-faced slat absorbers I mentioned. Get them in place. Listen. Move them around to places that seem like a good idea. Listen again. When you like them the best, play some well-recorded CD
's through the system and listen. If they sound good, you're done. If not, analyze what's wrong and, if it's still too live, add absorption. Try not to put absorption on the same part of opposite walls.
"Does this mean that 4" of rockwool absorbs 86% of the 125Hz Bass, all the freq (111%) around 250 and so forth" -
Yes and no. Companies that don't correct their absorption readings for the "edge effect" will often show absorption rates above 1.00 - this isn't even possible, since theoretically 1.0 is TOTAL absorption.
What happens is, during testing the material is tested in standard size pieces, and for some reason one of the dimensions is 9 feet - there are a lot of edge surfaces on a 9 foot sample, and they "skew" the results so as to show more absorption than the material could absorb if it had no edges.
I usually re-adjust ALL the absorption values a company gives, DOWNWARD until the highest absorption value = one. That same value difference is subtracted from ALL the values, and that gives you a more real world idea of what the stuff can do.
If, however, you're cutting the same material into smaller pieces and scattering them around the room, standard formulae for figuring out the Sabins of absorption won't work because of the edge effect I mentioned earlier.
See, nice simple stuff we're playing with, huh??!? Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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giles117
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knightfly
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Stefan, you could use the thicker stuff for your actual bass traps, it would do a better job - but for wall treatments, etc, the 95mm stuff is plenty thick. Check with them on the DENSITY though - you want at least 3 PCF, or 40-45 kG/Cubic Meter.
Bryan, here's their own literature -
http://www.owenscorning.com/comminsul/d ... Series.pdf
Later guys... Steve
Bryan, here's their own literature -
http://www.owenscorning.com/comminsul/d ... Series.pdf
Later guys... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...