RT60 measurement in my room
- Thread starter Analogous
- Start date
Don’t know.
The AI part of the search results complied this:
For any passive object to interact with a specific wavelength, its size needs to be approximately one-quarter of the wavelength. This makes it challenging to treat low frequencies using any passive device to reduce RT60.
Example: The wavelength of an 80Hz sound wave in air is approximately 4.3 meters or 14.1 feet. The REW measurement indicates a problem between 60-100Hz in my room. This translates into large (ugly) corner bass traps.
But more worryingly I am not able to hear the reverberant bass or boominess. So pondering …
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prateekatasniya
Well-Known Member
Tuned bass traps is the solution..
Or else multiple subs calibrated using DIRAC
Or else multiple subs calibrated using DIRAC
Thanks.
What’s a Tuned Bass trap?
square_wave
Well-Known Member
I am also curious about this.
I am guessing it refers to bass traps constructed with careful consideration to the density and thickness and dimensions to absorb just enough to tame the excess reverb in a particular room. If this is true, the next question is how is all this calculated?
square_wave
Well-Known Member
Gotcha. However, if the problem is between 40 and 100 hz, you will land up with bass traps that are quite large. Are there materials that will work on such large waves but are smaller in size ? I was wondering how one can make it small even if it is tuned.
I have seen people using DSP to fix such issues in bass in rooms where you cannot accommodate such large size traps. Especially Dirac.
I have seen people using DSP to fix such issues in bass in rooms where you cannot accommodate such large size traps. Especially Dirac.
I think the larger size of the wavelengths at these frequencies will dictate the density and thickness of the bass traps. If using bass traps they are going to be large and ugly.
I am reluctant to go the DSP-DIRAC route, but a equaliser that allows adjustments by hearing might be one way.
The big issue for me is I am not hearing the RT60 problem identified by the REW process.
I spent several hours today with a variety of music trying to do this.
Maybe I will just let it be and enjoy it as it is.
Sometimes what the mind does not know, the ear will not hear
grindstone
Active Member
Yeah, RT60 can mislead. Trust your ears. The utility of RT60 is that it's mostly repeatible. People (all of us) try to improve what we can measure, right?
IMO, the wavelets are the way to try to make sense of what something might be and whether it is (or should be?) fixable or not.
IMO, the wavelets are the way to try to make sense of what something might be and whether it is (or should be?) fixable or not.
Thanks for this useful and informative tutorial.
We did not perform the first three recommendations. I was not aware of the fourth in the list.
Well, if you don’t hear them, then it is better not to bother about it and enjoy the music the way it is.
I think a balanced subjective + objective approach would be beneficial. In other words, you would know which to consider and which to discard, based on your own personal preferences and judgment. It is all about perception.
One crucial information that is missing is that the speakers are Open Baffle. With these type, the room then acts as a cabinet.
A good internal damping is needed for the cabinets. The reason is that the sound waves from the rear of the woofer cone travel backwards and reflect back on to the same surface. If not damped properly they could interfere with the woofer movement, thereby making the sound muddy and smeared.
This is more pronounced with higher volume (SPL > 75dB). So, the stagnating waves and the nodes will further accentuate the issue.
I think a balanced subjective + objective approach would be beneficial. In other words, you would know which to consider and which to discard, based on your own personal preferences and judgment. It is all about perception.
One crucial information that is missing is that the speakers are Open Baffle. With these type, the room then acts as a cabinet.
A good internal damping is needed for the cabinets. The reason is that the sound waves from the rear of the woofer cone travel backwards and reflect back on to the same surface. If not damped properly they could interfere with the woofer movement, thereby making the sound muddy and smeared.
This is more pronounced with higher volume (SPL > 75dB). So, the stagnating waves and the nodes will further accentuate the issue.
prateekatasniya
Well-Known Member
Like tuned ported subwoofers... Tuned ported bass traps.
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Room measurements below 200hz are not reliable and should not be considered to draw any conclusion. A better approach will be to take atleast 10 measurements at various positions of the microphone and average the measurements. Maybe this could be something reliable. Our ears are a better tool to decide boom and resonance at low frequency.
Why are Room measurements below 200hz not reliable ?
grindstone
Active Member
There are 4-ish different ways that sound works in a room, frequency-wise. Direct sound...what most people think -- like ray-tracing. Direct+some reflections (reverberant), a "modal" region driven by the room size (which 200Hz might be a fine spot to set as a typical boundary to), and a "pressure" region (think like car-audio where it's too small for long waves to form but the cabin can certainly be pressurized by drivers, etc.). These are not step-function/sharply-delineated boundaries. There is a "transition region" between direct/reverberant, etc. Check-out Figures 4 & 13 here. The things you "go after" in your room are maybe the flip-side of thinking about how the sound works in your room. Your perfectly reasonable questions have you metaphorically standing on a greasy banana peel on the edge of a long slope 
Your questions are circling around stuff that, if not directly applicable/topical in your project at this instant, will be rites of passage on this trail. Fastest uptake intro might be YT of Toole (1 hr) and Griesinger (esp learning to listen = 1hr, aud proxim, localiz'n) YT videos.
Sooo, measuring below 200Hz is in the "modal" region. Think of bass under that freq like an undulating checkerboard of hot and cold spots and the image won't be far-off. So what you get depends on where you measure and that's why you can't trust (or at least conclude) much inside the modal region.
Your questions are circling around stuff that, if not directly applicable/topical in your project at this instant, will be rites of passage on this trail. Fastest uptake intro might be YT of Toole (1 hr) and Griesinger (esp learning to listen = 1hr, aud proxim, localiz'n) YT videos.
Sooo, measuring below 200Hz is in the "modal" region. Think of bass under that freq like an undulating checkerboard of hot and cold spots and the image won't be far-off. So what you get depends on where you measure and that's why you can't trust (or at least conclude) much inside the modal region.
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Thank you @grindstone .There are 4-ish different ways that sound works in a room, frequency-wise. Direct sound...what most people think -- like ray-tracing. Direct+some reflections (reverberant), a "modal" region driven by the room size (which 200Hz might be a fine spot to set as a typical boundary to), and a "pressure" region (think like car-audio where it's too small for long waves to form but the cabin can certainly be pressurized by drivers, etc.). These are not step-function/sharply-delineated boundaries. There is a "transition region" between direct/reverberant, etc. Check-out Figures 4 & 13 here. The things you "go after" in your room are maybe the flip-side of thinking about how the sound works in your room. Your perfectly reasonable questions have you metaphorically standing on a greasy banana peel on the edge of a long slope
Your questions are circling around stuff that, if not directly applicable/topical in your project at this instant, will be rites of passage on this trail. Fastest uptake intro might be YT of Toole (1 hr) and Griesinger (esp learning to listen = 1hr, aud proxim, localiz'n) YT videos.
Sooo, measuring below 200Hz is in the "modal" region. Think of bass under that freq like an undulating checkerboard of hot and cold spots and the image won't be far-off. So what you get depends on where you measure and that's why you can't trust (or at least conclude) much inside the modal region.
The Floyd Toole video is fascinating and so informative.
I will watch the Greisinger video soon as I digest the info from Toole.
Thank you for sharing these links. Definitely essential information for those who have been on the audio quest path for a while.
Ah no, you definitely can.
What you need is a sine wave generator and do a manual sweep. There will be many frequencies especially below 250 Hz where you will observe sudden boominess.
Fortunately, music is a mix of multi frequencies so few particular resonant frequencies will not typically stand out.
I sometimes use notch filter to eliminate such frequencies - but please note that any change in position means re-evaluation of the frequencies and reconfiguring the filter.
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