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Help analyze room graph and acoustic design
Old 21st September 2012
  #1
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sl4zhz's Avatar
 
🎧 10 years
Help analyze room graph and acoustic design

Hi, I was having difficulties to decide acoustic design for my room. I just measure my room grap with fuzzmeasure and ECM8000.
I use this room particularly for vocal-guitar-bass tracking, and mixing mastering purpose.
I'm using yamaha hs80m for my main studio monitor. what I'm trying to achieve here is to get more accurate listening room and flatter response, so that it helps my mixing decision.

Currenly my room have:
-2 basstrap in front, with egg foam in the center wall.
-2 basstrap on the first reflection left and right wall.
-2 egg foam (100x200cm) cover the backwall and 1 bass trap on top of the egg foam
-1 egg foam on the ceiling right on top of my table/mixing position.

Here's the graph
1/48


NEW GRAPH AFTER I MOVE MY SPEAKER POSITION DOWN by 20cm and added couple of basstrap and super chunk UPDATED 2013



1/3




Waterfall full spectrum


Waterfall 300hz


Reverb Time EDT


there's a big null -12db around 70hz
and also another null at around 500-700hz

Here's my room layout and pictures

front side

Left side

Left Side, just replace the big picture frame with bass trap


I'm planning to take out the BIG closet and add 1 more basstrap on the right side of the room and also the 2 remaining corner.
also I'm planning to put couple 120x60cm or 60x60 cmN7 diffuser.

My question:
-what cause the big null at 70db and 500-700hz ?
-will this additional diffuser, removing closet, adding basstrap help to treat my room significantly?
-what are your suggestion to help treat my room better ?

thanks a lot for your help
Old 21st September 2012
  #2
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by sl4zhz ➡️

-what cause the big null at 70db and 500-700hz ?
-will this additional diffuser, removing closet, adding basstrap help to treat my room significantly?
-what are your suggestion to help treat my room better ?

thanks a lot for your help
Frist of all; read this:

Before posting your measurement results

The null at 70 Hz is either a modal null (source and/or receiver in a null), an SBIR related issue or a combination of the two. The dip at 750 Hz is probably due to the desk reflection. Try raising the speaker and see if the dip moves and check the ETC for early energy corresponding to a ½ wavelength time difference (from the woofer) at your cancellation frequency. Placing the speakers on stands behind the desk usually solves this problem. Other possible sources for early energy is diffraction from poorly designed speaker baffles or displays or other edges nearby.

Regarding acoustic treatment in general:

4m x 5m x 2.5m room - modal resonance problem
Old 21st September 2012
  #3
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GIK Acoustics's Avatar
 
🎧 5 years
Quote:
Originally Posted by sl4zhz ➡️
My question:
-what cause the big null at 70db and 500-700hz ?
-will this additional diffuser, removing closet, adding basstrap help to treat my room significantly?
-what are your suggestion to help treat my room better ?
Jens did a wonderful job above illustrating the possible causes of a null at 70 Hz. To add a little bit of readability to it, a modal null would be a null caused by the dimensions of your room and your position in it. A null relating to SBIR would be one caused by the position of the speakers in your room and your position in relation to them. You can read more about modes and SBIR here: Acoustic Primer - Room Setup, Testing, Treatments

Adding a single bass trap would probably help, but you'll likely need more than a few to tame some of your massive spikes in the room and help even out the decay time. Also, you did not post the waterfalls of your room, which would be more beneficial for suggestions. You can view our video on REW here (the beginning goes over download and installation of REW, so you can skip the first half) and it will explain the different types of graphs and how to properly view them: Room EQ Wizard Tutorial Video

I would also like to point out that you should get your low end in control before throwing in diffusers. Diffusers can be very useful, but your room is very small - likely too small for proper use of diffusion [EDIT: I am sorry, disregard the prior sentence. I horribly misread your dimensions] I would focus my money and time into taming that 70 Hz null and getting more bass traps up in there.
Old 21st September 2012 | Show parent
  #4
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🎧 10 years
Quote:
Originally Posted by GIK Acoustics ➡️
Diffusers can be very useful, but your room is very small - likely too small for proper use of diffusion.
Allow me to disagree here.

A 6 meter room is absolutely not too small for proper use of diffusers. Depending on the ISD-gap required, as small as 4 meters is still long enough. One naturally needs to read up on how to use diffusers properly in combination with other treatment in order for it to be effective.



sl4zhz:

You might be able to address the null at 70 Hz somewhat by following the second point in my checklist linked to in previous post.
Old 21st September 2012 | Show parent
  #5
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🎧 5 years
Quote:
Originally Posted by Jens Eklund ➡️
Allow me to disagree here.

A 6 meter room is absolutely not too small for proper use of diffusers. Depending on the ISD-gap required, as small as 4 meters is still long enough. One naturally needs to read up on how to use diffusers properly in combination with other treatment in order for it to be effective.
Woah! Let me stand corrected, I horribly misread his dimensions. Thank you for addressing, I will edit my post above as well. 6 x 4 meters is clearly a good sized room. I should have known by the pictures!
Old 21st September 2012 | Show parent
  #6
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
Frist of all; read this:

Before posting your measurement results

The null at 70 Hz is either a modal null (source and/or receiver in a null), an SBIR related issue or a combination of the two. The dip at 750 Hz is probably due to the desk reflection. Try raising the speaker and see if the dip moves and check the ETC for early energy corresponding to a ½ wavelength time difference (from the woofer) at your cancellation frequency. Placing the speakers on stands behind the desk usually solves this problem. Other possible sources for early energy is diffraction from poorly designed speaker baffles or displays or other edges nearby.

Regarding acoustic treatment in general:

4m x 5m x 2.5m room - modal resonance problem
I see, so the solution for the 70hz is to check SBIR and modal null?
can you explain more on modal null ?

I wish to try placing the speaker on stand behind desk, but there are 2 rack on my table. if I put the speaker behind with stand, the rack will block the speaker right ? and If I try to put the speaker higher than the rack, its gonna be too high for my ear or listening position.
now the position measure is
floor to top table rack is 104cm + speaker 39cm
Old 21st September 2012 | Show parent
  #7
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by GIK Acoustics ➡️
Jens did a wonderful job above illustrating the possible causes of a null at 70 Hz. To add a little bit of readability to it, a modal null would be a null caused by the dimensions of your room and your position in it. A null relating to SBIR would be one caused by the position of the speakers in your room and your position in relation to them. You can read more about modes and SBIR here: Acoustic Primer - Room Setup, Testing, Treatments

Adding a single bass trap would probably help, but you'll likely need more than a few to tame some of your massive spikes in the room and help even out the decay time. Also, you did not post the waterfalls of your room, which would be more beneficial for suggestions. You can view our video on REW here (the beginning goes over download and installation of REW, so you can skip the first half) and it will explain the different types of graphs and how to properly view them: Room EQ Wizard Tutorial Video

I would also like to point out that you should get your low end in control before throwing in diffusers. Diffusers can be very useful, but your room is very small - likely too small for proper use of diffusion [EDIT: I am sorry, disregard the prior sentence. I horribly misread your dimensions] I would focus my money and time into taming that 70 Hz null and getting more bass traps up in there.
I'll post the more detail graph tonight and waterfall. thanks for your advise
Old 21st September 2012 | Show parent
  #8
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
Allow me to disagree here.

A 6 meter room is absolutely not too small for proper use of diffusers. Depending on the ISD-gap required, as small as 4 meters is still long enough. One naturally needs to read up on how to use diffusers properly in combination with other treatment in order for it to be effective.



sl4zhz:

You might be able to address the null at 70 Hz somewhat by following the second point in my checklist linked to in previous post.
do you think the big closet in the room might be the cause of 70hz ? cos in that side absolutely I can't install any basstrap whatsoever.

and I don't have too much treatment on the ceiling either.
on the floor I have them cover with carpet, rug, almost 70% of the room
Old 21st September 2012 | Show parent
  #9
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by sl4zhz ➡️
I see, so the solution for the 70hz is to check SBIR and modal null?
can you explain more on modal null ?

I wish to try placing the speaker on stand behind desk, but there are 2 rack on my table. if I put the speaker behind with stand, the rack will block the speaker right ? and If I try to put the speaker higher than the rack, its gonna be too high for my ear or listening position.
now the position measure is
floor to top table rack is 104cm + speaker 39cm
How to treat nulls

You can put your monitors upside down (but still keeping the acoustic axis in ear height unless you tilt the speaker, then you can place them even higher) thus further increasing the distance from the woofer to the reflection surface and even better if the speakers are placed further back as well (on stands behind the desk).
Old 21st September 2012
  #10
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Frequency response is important but really want you want to look at is the decay time on the low end (think of this as low end reverb). That is much more damaging to properly hearing the low end. For that you need a lot more bass trapping in our room in the corners. In a room like that I can see 10 or more traps in corners easily.
For testing for placement try to the following program.
Video: Testing Bass Trap Placement
Old 21st September 2012
  #11
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🎧 10 years
I've updated the graph pict
is my room in a very bad condition looking at the graph?
Old 21st September 2012 | Show parent
  #12
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by sl4zhz ➡️
I've updated the graph pict
is my room in a very bad condition looking at the graph?
Please have a look at this post:

https://gearspace.com/board/7699710-post1.html

The two important graphs are the ETC and the waterfall plot. EDT is more or less useless for checking decay times in control rooms, so if decay times are of interest; use "Topt" or similar (that checks the slope of the linear Schroeder integral).
Old 21st September 2012 | Show parent
  #13
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
Please have a look at this post:

https://gearspace.com/board/7699710-post1.html

The two important graphs are the ETC and the waterfall plot. EDT is more or less useless for checking decay times in control rooms, so if decay times are of interest; use "Topt" or similar (that checks the slope of the linear Schroeder integral).
I'm using fuzzmeasure trial, does't have ETC graph. I'll try to install REW and try to do another measurement. I have the waterfall though. thanks jens for your help.
Old 21st September 2012 | Show parent
  #14
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by sl4zhz ➡️
I have the waterfall though. thanks jens for your help.
Adjust the setting to increase the resolution in order to be able to identify individual modes and also adjust the range to include down to 20 Hz (instead of only 50 Hz currently).

One thing one can say already is that the decay time below about 150 Hz is too long but above 150 Hz, the decay time is good (up to 500 Hz at least, perhaps too short in the highs), so you probably don´t want to add more broadband absorption (velocity based) but instead rearrange the once you have, increase the depth of the once you have or add pressure based absorbers to tackle the region below 150 Hz without absorbing more above.
Old 21st September 2012 | Show parent
  #15
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Considering I doubt you know what to tune the pressure based (tuned) trap at or where to place them I would stick with broad band with something like FRK on the fronts to reflect high end. But then again you could work with a company that has a proven product that is tuned and can help you with placement. It really comes down to what kind of skill you have and or your budget.
Old 22nd September 2012 | Show parent
  #16
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
Adjust the setting to increase the resolution in order to be able to identify individual modes and also adjust the range to include down to 20 Hz (instead of only 50 Hz currently).

One thing one can say already is that the decay time below about 150 Hz is too long but above 150 Hz, the decay time is good (up to 500 Hz at least, perhaps too short in the highs), so you probably don´t want to add more broadband absorption (velocity based) but instead rearrange the once you have, increase the depth of the once you have or add pressure based absorbers to tackle the region below 150 Hz without absorbing more above.
I've updated the pictures to 20hz.
how to read the waterfall? is it right if i read i like this
the RED circle area is freq 150hz below and the decay time to long around 350ms ?
and the BLUE circle 500hz above is too short and the decay time around 250ms ?



what do you mean by increas the depth of the once you have?
is this what you mean adding pressure based absorbers ?
https://gearspace.com/board/attachme...-helmholtz.jpg
Old 22nd September 2012 | Show parent
  #17
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by sl4zhz ➡️
I've updated the pictures to 20hz.
how to read the waterfall? is it right if i read i like this
the RED circle area is freq 150hz below and the decay time to long around 350ms ?
and the BLUE circle 500hz above is too short and the decay time around 250ms ?

Well, the decay time from about 200 Hz to 2-4 kHz is good (about 250 ms) but above it, it´s shorter and this is usually something we try to avoid.

The decay time below about 150 Hz is longer than the scale of the time line since the decay of a room mode does not suddenly drop like your graph shows, so it looks like you are gating the IR. Export the impulse as an audio file (wav/AIFF) and post it here (or PM me a download link) and I´ll make you a waterfall plot with appropriate settings and higher resolution (I don´t use Fuzz).



Quote:
Originally Posted by sl4zhz ➡️
what do you mean by increas the depth of the once you have?
Increasing the depth of existing velocity based absorbers (used for early reflection control) will increase efficiency at lower frequencies so the performance is not limited to the mids and highs that cause the response you see in the waterfall plot:

https://gearspace.com/board/7237454-post133.html
https://gearspace.com/board/7713914-post3.html

Quote:
Originally Posted by sl4zhz ➡️
is this what you mean adding pressure based absorbers ?
https://gearspace.com/board/attachme...-helmholtz.jpg
Yes, that’s a slotted panel in the shape of polys (for some scattering effect). Pressure based absorbers are usually either membrane absorbers or perforated panels (slots, circular holes or other perforations) forming an array of Helmholtz resonators. Pressure based absorbers are used to tame the low frequency rang that might be tricky to take care of using velocity based absorbers unless very deep but even if so, they still absorb the highs as well so unless we want to end up with a dry sounding room we try to avoid broadband absorption and use it only where needed (early reflection points) and use pressure based absorbers for the modal range.
Old 22nd September 2012
  #18
Gear Guru
 
1 Review written
🎧 15 years
Simple

si4hz, FuzzMeasure is a very powerful analytical tool. It displays graphically how a room behaves when acoustically stimulated. Fascinating and very useful when you get to know how to ask it questions.
However, an ECG monitor will not make a heart surgeon.
Showing a graph and asking, how good/bad is my room, is, well, the wrong question. And unnecessary if you are simply someone who wants to improve your listening conditions. The advice is to be found all over the place.
Massive amounts of bass trapping in corners.
Kill the reflections above and to the sides of your listening position.
It is as simple as that.
FuzzMeasure 3 has ETC. Earlier versions have Impulse Response, which is useable for reflection work. Those odd images at LF are caused by your Window being much shorter than your viewing time scale. Try your Graph window at 600mS and the Measurement Window at 500mS.
The falling HF is probably due to running two speakers. One should be the norm.
http://www.irishacoustics.com/index....oom-acoustics/

DD
Old 22nd September 2012 | Show parent
  #19
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by DanDan ➡️
si4hz, FuzzMeasure is a very powerful analytical tool. It displays graphically how a room behaves when acoustically stimulated. Fascinating and very useful when you get to know how to ask it questions.
However, an ECG monitor will not make a heart surgeon.
Showing a graph and asking, how good/bad is my room, is, well, the wrong question. And unnecessary if you are simply someone who wants to improve your listening conditions. The advice is to be found all over the place.
Massive amounts of bass trapping in corners.
Kill the reflections above and to the sides of your listening position.
It is as simple as that.
FuzzMeasure 3 has ETC. Earlier versions have Impulse Response, which is useable for reflection work. Those odd images at LF are caused by your Window being much shorter than your viewing time scale. Try your Graph window at 600mS and the Measurement Window at 500mS.
The falling HF is probably due to running two speakers. One should be the norm.
Measuring Room Acoustics

DD
dandan. what do you mean by Window being much shorter than your viewing time scale here ? I set the duration of the waterfall to 500ms.
and I'm using only 1 speaker which is the left speaker
Old 22nd September 2012 | Show parent
  #20
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
Well, the decay time from about 200 Hz to 2-4 kHz is good (about 250 ms) but above it, it´s shorter and this is usually something we try to avoid.

The decay time below about 150 Hz is longer than the scale of the time line since the decay of a room mode does not suddenly drop like your graph shows, so it looks like you are gating the IR. Export the impulse as an audio file (wav/AIFF) and post it here (or PM me a download link) and I´ll make you a waterfall plot with appropriate settings and higher resolution (I don´t use Fuzz).





Increasing the depth of existing velocity based absorbers (used for early reflection control) will increase efficiency at lower frequencies so the performance is not limited to the mids and highs that cause the response you see in the waterfall plot:

https://gearspace.com/board/7237454-post133.html
https://gearspace.com/board/7713914-post3.html



Yes, that’s a slotted panel in the shape of polys (for some scattering effect). Pressure based absorbers are usually either membrane absorbers or perforated panels (slots, circular holes or other perforations) forming an array of Helmholtz resonators. Pressure based absorbers are used to tame the low frequency rang that might be tricky to take care of using velocity based absorbers unless very deep but even if so, they still absorb the highs as well so unless we want to end up with a dry sounding room we try to avoid broadband absorption and use it only where needed (early reflection points) and use pressure based absorbers for the modal range.
here's the impuse data
https://dl.dropbox.com/u/2416466/cub...%20measure.csv

if I put Q7 diffuser behind the mixing position and the back side wall is it a good idea ?
and what you suggest for my ceiling
Old 22nd September 2012 | Show parent
  #21
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Glenn Kuras ➡️
Frequency response is important but really want you want to look at is the decay time on the low end (think of this as low end reverb). That is much more damaging to properly hearing the low end. For that you need a lot more bass trapping in our room in the corners. In a room like that I can see 10 or more traps in corners easily.
For testing for placement try to the following program.
Video: Testing Bass Trap Placement
that video makes me wanna put basstrap from floor to ceiling.
thanks for the input.. do you have any suggestion for the ceiling?
currenly I only have 100x200cm egg foam on top of my mixing position.
my ceiling is plain gypsum. I'll post more picture of my room soon
Old 22nd September 2012
  #22
Gear Guru
 
1 Review written
🎧 15 years
Windoze

The Exported Impulse Response should be a simple WAV file. Best to Zip it and insert directly in the posts here.
The Graph Duration and Window are different things. See below how a short Window can distort a graph. Fuzz seems to want them to be equal length or close to it. REW is happy to use shorter windows which give greater accuracy in one respect. This is covered in the linked primer, the Fuzz manual, and best of all the REW manual.
Help analyze room graph and acoustic design-screen-shot-2012-09-22-18.26.27.jpg
Help analyze room graph and acoustic design-screen-shot-2012-09-22-18.27.04.jpg


DD
Old 23rd September 2012
  #23
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
dandan here's antoher shoot.
is this better ?
Old 23rd September 2012
  #24
Gear Guru
 
1 Review written
🎧 15 years
Better

You know it is! Now you can see that you have one big problem around 70Hz. You can see a BIR null around 65Hz early in the decay, then a mode around 70Hz swelling up to dominate later on. The mode is obviously the more significant. Play a 70 ish sinewave loudly and tune it carefully until you hear maximum resonance. Then find the loudest spots. These are the best places to place treatment. Could be overhead.
DD
Old 24th September 2012 | Show parent
  #25
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by DanDan ➡️
You know it is! Now you can see that you have one big problem around 70Hz. You can see a BIR null around 65Hz early in the decay, then a mode around 70Hz swelling up to dominate later on. The mode is obviously the more significant. Play a 70 ish sinewave loudly and tune it carefully until you hear maximum resonance. Then find the loudest spots. These are the best places to place treatment. Could be overhead.
DD
thanks dan.. yeah thats the problem, I fell that my mixes always tend to lack of low. especially the bass instrument.
overhead means the ceiling side ?
so you mean play a 70 sinewave and measure it with spl meter and find the spot ? how if I don't have spl meter? is there any I can do with microphone maybe?
Old 24th September 2012
  #26
Gear Guru
 
1 Review written
🎧 15 years
Ear Ear

A microphone and a meter in your DAW or Desk will do fine. Although, you will probably find the hot spots very easily by ear.
DD
Old 27th September 2012 | Show parent
  #27
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by DanDan ➡️
A microphone and a meter in your DAW or Desk will do fine. Although, you will probably find the hot spots very easily by ear.
DD
I've try to play a 70hz sine wave from here
http://www.realmofexcursion.com/audi...tones/70hz.mp3

and I use my behringer ecm8000 as well.
I read through my saffire pro 40 input meter.

When I put the microphone in mixing position it reads around -23db
when i move it to Top left and right corner it jumps to -3db
mostly I get a significant jump around the front ceiling and corner


doest it means that these are need to be treated properly?
and after I tame all that area 70hz, is it going to help 70hz null in my room?
Old 27th September 2012 | Show parent
  #28
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
that video makes me wanna put basstrap from floor to ceiling.
Which you should do!

Quote:
thanks for the input.. do you have any suggestion for the ceiling?
4" panels in the early reflection point with a few more straddling upper wall to ceiling corners. This will help with height modes.

Video: First Reflection Points
Old 27th September 2012 | Show parent
  #29
Gear Maniac
 
sl4zhz's Avatar
 
🎧 10 years
Quote:
Originally Posted by Glenn Kuras ➡️
Which you should do!



4" panels in the early reflection point with a few more straddling upper wall to ceiling corners. This will help with height modes.

Video: First Reflection Points
I know that left and right walls first reflection point is by using mirror.
what about the ceiling ? there's first reflection point too?
how to measure ?

yeah I'm pllaning to put bass trap on left right ceiling wall
Old 27th September 2012
  #30
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
I know that left and right walls first reflection point is by using mirror.
what about the ceiling ? there's first reflection point too?
how to measure ?
Same thing, just use the mirror there also. Basically it is center between where you sit and the monitors.
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