To make a simple fun experiment:
Take some tubes or bottles, construct for them a neck with straws of variable lenght by adding segments or substracting segments , and with straws of variable perimeter ....No need to calculate anything for this fun experiment....make some other tubes of different volume size without neck only a fabric cloth for filtering the aperture also with variable size...The first volume will absorb more than diffuse by virtue of the ratio between the volume and his neck, the other without neck will diffuse more than they absorb...
But remember that the mechanical Helmoltz control cannot replace the balance between passive material treatment with absorbing surfaces, diffusive surfaces and reflecting surfaces at the right spot in the room... I make all this by EARS listening experiments during many months each day... It was the more fun i ever have...
Make a few of them, tubes and bottles with different size and put them on various reflection point in the room..
Only this fun experiment will give you a "taste" of things to come..
Now it is impossible to design these bottles and tubes in a grid of resonators and diffusers with an priori size because of the specificity of each room content, and geometry and because of the specific needs of each speakers type...
This grid of H. R. has the goal to change the distribution of the zone pressures to accomodate the room response to this specific speakers you own FOR YOUR EARS who act like a microphone... The timbre of instrument response from the speakers is used here like a test frequency coming from an electronical equalizer, instead here the grid of tubes is a mechanical equalizer... The volume of the tubes must be varied...
I eliminate negative impact of one tube by the self correecting number of the tubes in my grid designed by adding one or two or three at a times with the response of my ears to correct mechanically each one ratio aperture or neck lenght... It is easy and fun like tuning a piano...Anybody can do it with self confidence... And we learn how to listen in the process... it is an INCREMENTAL process of correction of the room for our specific speakers...
You must experiment...
I did mine on a long time experiment each day non stop for months...It cost me peanuts...
Each room need his particular grid...
But the principle is very simple and easy to play with IF YOU HAVE A DEDICATED ROOM... If not your wife will divorce... Sorry... 😁😊
But a room need material passive treatment also ...
Helmholtz resonators and diffusers cannot replace treatment, and passive material treatment cannot in no way replace mechanical Helmholtz control...
my room is a dedicated audio room for sure and my numerous tubes look like the pipe organ distributed around my room and two listening positions...
The result is so amazing that my system of 500 bucks give a ratio S.Q. /price over the roof....
No sellers of acoustic panels sells a grid of resonator which anyway must be tuned by ears for specific ears, room and speakers..If a pro acoustician would dare to do that the cost will be more near 100,000 dollars with the time need for the tuning and the material cost of the passive treatment plus the cost of the esthetically pleasing H.R. resonators and diffusers......
Think about that: it cost me nothing save using junk materials...It is not esthetical though but i dont give a dam, i dont want and i cannot afford to throw my money...
An audiophile system was my dream beginning was i had 24 years old...life never give me the time to do it and learn it right till my retirement...
Why do you think my information dont please everyone?
For sure you need a dedicated audio room... This is the ONLY costly device need for audio , NOT THE GEAR, the room...Almost all other audiophiles claim that the gear matter first and last, but they are wrong...Almost no one experimentr with acoustic, most people buy acoustic panels all stop there at best...
The electronical engineering industry is mature for the last 70 years...A good amplifier of 1960 is a good one today...
But the science of small room acoustic exist with the demand which exist ONLY for the last few decades with the production of stereo comnplex separate audio system parts...