How to interpret (and correct for) room modes

SeanRo

Standard Member
I'd like guidance on how to interpret and correct for room modes, specifically how to relate the different room mode pictures at different frequencies to the sub and seating positions.

I'm early in my dedicated room build and in my understanding of room acoustics.
First I read Different room modes explained. - inSync

Then I entered my room values for the hard walls after sound isolation 4450 x 5132 x 2450 (LxWxH) into an online calculator - amcoustics.com and adjusted for an RT60 of 0.4 seconds

The first try calculation - 445x513x245 showed I was good for Bonello but outside the Bolt envelope. I can't increase the size of my room further but by decreasing the length by 20cm I could get on the edge of the Bolt envelope and still pass Bonello
calculation 425x513x245 I was planning on a fabric covered frame around the screen and LCR speakers but can change this to a baffle wall, reducing actual length without any perceived loss of length.

Some questions:

Am I right to use RT60 = 0.4 for a home theatre?

Is the critical distance the diameter of the 'sweet spot'? Where would this sweet spot be located? I'm planning an MLP 2.64m from the screen which is 62% of the length of the room - very close to 3/5. Which sounds like that could be an issue at specific frequencies.

When I run the mouse over the piano keys the Room 3D picture changes showing the pressure points - how am I supposed to interpret this and use it for planning treatment, sub placement and mlp?

For my room of 90m2 surface area, am I reading correctly that they recommend 20m2 of absorption?

Are there better online tools to use when planning the room dimensions?

Thanks
 

Lesmor

Distinguished Member
Hi
Congratulations on researching and realising how important the room is
if you were further on in construction I would have suggested measuring the room with REW to see what the real world issues were
unfortunately room acoustics is a complicated subject there are just too many variables at play and with the best will in the world any advice from AVF members (myself included) will be a crap shoot
you have an irregular shaped space so the tools you have at hand will only really be a guide

with a blank canvas I would start by determining which "golden ratio" might work in your space,but even then there are so many construction variables in play to skew the results it might be worth hiring a professional for a room design
 

Lesmor

Distinguished Member
I do plan on learning REW (I have a reverberant games room next door that could do with taming) but for the home theatre I'm still at the bare studs stage - so figured REW no use until the plasterboard is up.

Thanks for the link to the Golden Ratio article - my room is totally un golden!
I would say most of our rooms are un-golden but we have to start somewhere
my main point is that it is great to realise the importance of the room and room acoustics but the tools at hand are all theory which never translates to reality
you have a great space to work with
 

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