Anyone used these room acoustics calculators? How to interpret results - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 6 Old 06-22-2020, 03:21 PM - Thread Starter
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Anyone used these room acoustics calculators? How to interpret results

Was looking at these using google translate:
https://www.hunecke.de/en/calculator...igenmodes.html
https://trikustik.at/amroc/index.php...&h=259&r60=0.6

I put in my data, height 259 cm, width 439 cm and length 379 cm. Not sure how to interpret the result and how to take action to improve speaker position and room acoustics?

Anyone understand these things?
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post #2 of 6 Old 06-22-2020, 09:56 PM
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As a tool, by itself, it can help predict problem areas in the in room FR response, potential high / low areas of pressure and sound build up or deficiency . . .

another good tool that will get you more into the game as played in this forum
wrt to how your stuff and the room are playing together is
get REW and the calibrated ummk-6 mike setup

there is a learning curve but there are well groomed tutorials

then when you post results, the sweeps- done as per the correct manner
you'll see guidance and corrective suggestions that you can use

the room mode calc. can display potential problems

REW will show you your real interaction in real time, set a base line of system in the raw
then you can set a plan for improvements

subscribe to this thread, get the tutorials, the mike and stick with it

https://www.avsforum.com/forum/91-au...et-graphs.html

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post #3 of 6 Old 06-23-2020, 09:31 AM
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If you blow across an empty bottle, you can get the air inside that small chamber to resonate (make that booooooh sound). If you enlarge that small chamber to the size of your room, the air inside will still resonate (of course at different frequencies than the bottle).

The calculators you linked to show what the resonances (room modes) are for your room, based on the dimensions you enter. Easier to understand room modes if the calculator used a different style of graphics. Try downloading the Harman room mode calculator at the bottom of this page: https://www.harman.com/audio-innovations

For example, your 379 cm room length will result in modes/resonances at 46Hz, 91Hz, 137Hz, 182Hz, 228Hz, 273Hz, etc. The first 4 of these are mapped in the graph below, with each room mode colour coded so you can see where each of those problem frequencies are peaking or nulling.



Useful to view the modes this way because it can help you with placement. For example, the worst place to sit would at the midpoint of room length, because it's all loud peaks and quiet nulls (all extremes, no moderation). Frequency response would look like a roller coaster.



Notice that all the nulls fall at even divisions (half, quarters, sixths) of room length. You can avoid these by placing the listeners' ears at odd divisions (thirds, fifths) of room length. For example, at 2/3 back from the front wall, most of the problem frequencies are the same level. Good place for the listeners.



Understanding how to view these room mode graphs can help you pick seating location (and subwoofer/speaker locations) so that you get smoother frequency response (fewer/smaller peaks & dips). This will give the room correction system in your receiver a big head start. Best part: it's free (doesn't cost anything to move listeners, subwoofers & speakers).
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post #4 of 6 Old 06-23-2020, 01:19 PM - Thread Starter
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Quote:
Originally Posted by sdurani View Post
If you blow across an empty bottle, you can get the air inside that small chamber to resonate (make that booooooh sound). If you enlarge that small chamber to the size of your room, the air inside will still resonate (of course at different frequencies than the bottle).

The calculators you linked to show what the resonances (room modes) are for your room, based on the dimensions you enter. Easier to understand room modes if the calculator used a different style of graphics. Try downloading the Harman room mode calculator at the bottom of this page: https://www.harman.com/audio-innovations

For example, your 379 cm room length will result in modes/resonances at 46Hz, 91Hz, 137Hz, 182Hz, 228Hz, 273Hz, etc. The first 4 of these are mapped in the graph below, with each room mode colour coded so you can see where each of those problem frequencies are peaking or nulling.



Useful to view the modes this way because it can help you with placement. For example, the worst place to sit would at the midpoint of room length, because it's all loud peaks and quiet nulls (all extremes, no moderation). Frequency response would look like a roller coaster.



Notice that all the nulls fall at even divisions (half, quarters, sixths) of room length. You can avoid these by placing the listeners' ears at odd divisions (thirds, fifths) of room length. For example, at 2/3 back from the front wall, most of the problem frequencies are the same level. Good place for the listeners.



Understanding how to view these room mode graphs can help you pick seating location (and subwoofer/speaker locations) so that you get smoother frequency response (fewer/smaller peaks & dips). This will give the room correction system in your receiver a big head start. Best part: it's free (doesn't cost anything to move listeners, subwoofers & speakers).
Thanks that certainly explain some problems I've been having. Seating position is almost around the mid point of the room, and sometimes when kids move the sofa even a small amount the sound becomes very different.

But another question - from looking at this would one place the subwoofer at the low point of the nulls in the bass e.g. 46 hz - or is it the opposite: avoid putting the subwoofer there?

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post #5 of 6 Old 06-23-2020, 03:38 PM
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Quote:
Originally Posted by Osamede View Post
But another question - from looking at this would one place the subwoofer at the low point of the nulls in the bass e.g. 46 hz - or is it the opposite: avoid putting the subwoofer there?
Placing a sub in the null of a mode prevents that particular room mode from resonating. When you look at the peaks & nulls on the graph, think of them more as coupling functions rather than acoustical peaks & nulls (note that there's no dB scale on the side of the graph). The coupling function shows you how strongly a subwoofer couples with a room mode. So if you place your sub in the null of the 46Hz mode, then that mode will not resonate (zero coupling going on at that location). All the peaks & nulls caused by that mode disappear. However, that locations is also the peak of the 91Hz mode, so it will resonate very loudly at that location. Not to worry, EQ can pull down a peak. But you do get rid of the giant null there.
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post #6 of 6 Old 06-23-2020, 11:57 PM - Thread Starter
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Thanks - that was very helpful for taking action!
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