Let´s say, you have to tune a "plywood box" (SAE´s panel absorber like) at 110 Hz... Given certain dimensions and materials, how do you know the freq you´re aiming to? (Hemholtz resonator formula like...)
Thank you! Regards.
Chino
Diaphragmatic traps...
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
Diaphragmatic traps...
Is there any precise formula to calculate the centre freq of a diaphragmatic trap so you can tune it correctly?
Let´s say, you have to tune a "plywood box" (SAE´s panel absorber like) at 110 Hz... Given certain dimensions and materials, how do you know the freq you´re aiming to? (Hemholtz resonator formula like...)
Thank you! Regards.
Chino
Let´s say, you have to tune a "plywood box" (SAE´s panel absorber like) at 110 Hz... Given certain dimensions and materials, how do you know the freq you´re aiming to? (Hemholtz resonator formula like...)
Thank you! Regards.
Chino
-
the dreamer
- Posts: 207
- Joined: Thu Dec 11, 2003 3:02 am
- Location: in the alps / Europe
http://www.mhsoft.nl/Helmholtzabsorber.asp
Don't use the Helmholtz-calculator on that site, according to Steve it's still the woring formula!
Hope this helps!
Florian
Don't use the Helmholtz-calculator on that site, according to Steve it's still the woring formula!
Hope this helps!
Florian
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
-
Ethan Winer
- Senior Member
- Posts: 1063
- Joined: Fri Feb 21, 2003 3:50 am
- Location: New Milford, CT, USA
- Contact:
Re: Diaphragmatic traps...
Chino,
> Is there any precise formula to calculate the centre freq of a diaphragmatic trap so you can tune it correctly? <
Yes, and be aware that a panel trap is not the same as a Helmholtz resonator. The correct formula for panel traps is shown in Everest's popular Handbook, and also repeated in this post at my Acoustics forum:
http://www.musicplayer.com/ubb/ultimate ... 00766.html
You can also see complete plans to built them here:
www.ethanwiner.com/basstrap.html
The low-bass trap shown in these plans is tuned to about 100 Hz, and the high-bass type is about 180 Hz. Each absorbs over a range of about one octave.
--Ethan
> Is there any precise formula to calculate the centre freq of a diaphragmatic trap so you can tune it correctly? <
Yes, and be aware that a panel trap is not the same as a Helmholtz resonator. The correct formula for panel traps is shown in Everest's popular Handbook, and also repeated in this post at my Acoustics forum:
http://www.musicplayer.com/ubb/ultimate ... 00766.html
You can also see complete plans to built them here:
www.ethanwiner.com/basstrap.html
The low-bass trap shown in these plans is tuned to about 100 Hz, and the high-bass type is about 180 Hz. Each absorbs over a range of about one octave.
--Ethan
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
-
the dreamer
- Posts: 207
- Joined: Thu Dec 11, 2003 3:02 am
- Location: in the alps / Europe
-
Ethan Winer
- Senior Member
- Posts: 1063
- Joined: Fri Feb 21, 2003 3:50 am
- Location: New Milford, CT, USA
- Contact:
Chino,
> are you using your ModeCalc to see "virgin room" modes <
Yes, my ModeCalc program will show you the important modes. But be aware that calculating modes is not the same as measuring the room. A while ago I tested a normal rectangular room with standard sheet rock walls and ceiling. The measured modes were 20 percent higher than predicted! This is not a failing of mode calculators, because the numbers are correct. But no mode calculator I know of can account for losses in the walls or other factors that can shift the frequencies.
--Ethan
> are you using your ModeCalc to see "virgin room" modes <
Yes, my ModeCalc program will show you the important modes. But be aware that calculating modes is not the same as measuring the room. A while ago I tested a normal rectangular room with standard sheet rock walls and ceiling. The measured modes were 20 percent higher than predicted! This is not a failing of mode calculators, because the numbers are correct. But no mode calculator I know of can account for losses in the walls or other factors that can shift the frequencies.
--Ethan
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
Thanks Ethan (and thanks, Florian, for the links)!
Yes, I totally understand what you say. Practice is, and even more in acoustics, not as much as theory, as you´d know... But is good to have an approximation, an approach to that specific issues you know you could have, let´s say, in a "no-good-ratio" room - my case here...
I´m working on a space that is 3,50 m L x 2,68 m W x 2,90 m H ... and, in numbers, I can see a little problem at around 100Hz.
So, I´m trying to get as close as possible to the correct frequency, attack it, and when I "theoretically"cover the known problems given by calculators, I´ll give a good measurement of this room.
Any suggestion from all of you, guys, is very welcome!!
Thanks again.
Chino.
Yes, I totally understand what you say. Practice is, and even more in acoustics, not as much as theory, as you´d know... But is good to have an approximation, an approach to that specific issues you know you could have, let´s say, in a "no-good-ratio" room - my case here...
I´m working on a space that is 3,50 m L x 2,68 m W x 2,90 m H ... and, in numbers, I can see a little problem at around 100Hz.
So, I´m trying to get as close as possible to the correct frequency, attack it, and when I "theoretically"cover the known problems given by calculators, I´ll give a good measurement of this room.
Any suggestion from all of you, guys, is very welcome!!
Thanks again.
Chino.
-
Ethan Winer
- Senior Member
- Posts: 1063
- Joined: Fri Feb 21, 2003 3:50 am
- Location: New Milford, CT, USA
- Contact:
Chino,
> I´m working on a space that is 3,50 m L x 2,68 m W x 2,90 m H ... I´m trying to get as close as possible to the correct frequency, attack it <
Tuned absorption is not appropriate in a room that size. You'll get much better results from broadband absorption - rigid fiberglass at least four inches thick mounted straddling all of the corners including the wall-ceiling corners. Wood panel traps make more sense in large rooms.
--Ethan
> I´m working on a space that is 3,50 m L x 2,68 m W x 2,90 m H ... I´m trying to get as close as possible to the correct frequency, attack it <
Tuned absorption is not appropriate in a room that size. You'll get much better results from broadband absorption - rigid fiberglass at least four inches thick mounted straddling all of the corners including the wall-ceiling corners. Wood panel traps make more sense in large rooms.
--Ethan
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
>You'll get much better results from broadband absorption<
Hummmm... You´re right, of course, Ethan.
Most of all because I´m soffit-mounting the monitors, a pair of KrKs, that have a known "extra low" reinforcement...
The fact is I will use two models of 2D diffusers (designed by an argentinean engineer and designer, an ex-chief of mine, that are very good indeed), on the ceiling and in the back, and a hanging trap over the head. One of the diffusers, by construction acts like a low-medium trap (from 160 t 350 Hz), there I have som absorption. But I need a lower one too...
So, I´ll have very little space to work on with the broadband absorbers. I´ll have to use the free places, like the sides below the windows, the ceiling corners, and the space between the superior end of the door and the ceiling, to build traps in...
Here are some snapshots of the design, to give you an idea of what it´s being done.
Well, I´ll keep on thinking and trying to solve the things... Opinions are welcome, as usual.
Thanks again!!
Chino
Hummmm... You´re right, of course, Ethan.
Most of all because I´m soffit-mounting the monitors, a pair of KrKs, that have a known "extra low" reinforcement...
The fact is I will use two models of 2D diffusers (designed by an argentinean engineer and designer, an ex-chief of mine, that are very good indeed), on the ceiling and in the back, and a hanging trap over the head. One of the diffusers, by construction acts like a low-medium trap (from 160 t 350 Hz), there I have som absorption. But I need a lower one too...
So, I´ll have very little space to work on with the broadband absorbers. I´ll have to use the free places, like the sides below the windows, the ceiling corners, and the space between the superior end of the door and the ceiling, to build traps in...
Here are some snapshots of the design, to give you an idea of what it´s being done.
Well, I´ll keep on thinking and trying to solve the things... Opinions are welcome, as usual.
Thanks again!!
Chino
Last edited by chinocurva on Fri Aug 19, 2005 5:12 am, edited 1 time in total.
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
Between the two soffited monitors you can see a "tall" red stud. It´s about 2,50 m H x 1,30 m W x 0,10 m D. I was thinking about using it as the biggest broadband absorption in the room, plus one above the door, the ceiling hanger, some on the corners of the ceiling, and the ones under the windows (Regardless of any other necessary, that will be placed wherever it could be possible).
What do you think?
Thanks to all of you!
Chino.
What do you think?
Thanks to all of you!
Chino.
-
the dreamer
- Posts: 207
- Joined: Thu Dec 11, 2003 3:02 am
- Location: in the alps / Europe
Chino,
I often read that generally diffusion is not recommended when the distance from your ear to the diffusor is less than around 3 - 3,5m. The diffuse field can not develop. Maybe it's a better idea if you build Superchunks all around the ceiling/wall corners
and a broadbandpanel on the backwall?!?? Just thinking.....
Florian
I often read that generally diffusion is not recommended when the distance from your ear to the diffusor is less than around 3 - 3,5m. The diffuse field can not develop. Maybe it's a better idea if you build Superchunks all around the ceiling/wall corners
and a broadbandpanel on the backwall?!?? Just thinking.....Florian
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
-
knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
All well and good, but there is absolutely no mention of a working distance in the brochure; all diffusors, by definition, need a certain amount of distance to achieve a diffuse sound field - the distance is wavelength related, so the deeper the frequency of diffusion the longer the practical working distance between the diffusor and the ear in order to achieve a diffuse sound field... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
-
chinocurva
- Posts: 36
- Joined: Thu Jul 14, 2005 12:49 am
- Location: Buenos Aires, Argentina
- Contact:
Oh, I love discussions!! They´re so constructive!!! 
Well, let´s see. Why should I speak for "the designer´s mouth"...?
Let me introduce you Eng. Bidondo. He will give a more accurate explanation on the subject. I think he´s registering now...
Kind regards and let´s keep sharing knowledge!!! It´s soooo good for all of us.
Chino.
Well, let´s see. Why should I speak for "the designer´s mouth"...?
Let me introduce you Eng. Bidondo. He will give a more accurate explanation on the subject. I think he´s registering now...
Kind regards and let´s keep sharing knowledge!!! It´s soooo good for all of us.
Chino.