panels and design

[RCA]

Hi all,

Last week I took a look in a bigger studio just to see what they had done about acoustics.
They had a big helmholtz resonator above their monitoring system with very big openings.

That transmitted a puls to my brain......
Why did they make the slats vertical and not horizontal.
Other questions also poped in to my head.

So here they are :

From the design view I liked to make the seiling optical higher by adding the slats vertically in my helmholtz resonator.

Question : if I make two panels with the same number of slats and both on the same range of frequencies. Do they operating differendly if the slats are horizontal or vertical ? or does the results stay the same ?
If not , when do you use which type ?
See drawing below



Question 2:

With a formula you can calculate the resonance frequency of a panel absorber.
If I would make it with a variable depth will it work on more frequencies?
Maybe so : one variable is depth but your panel has limitations right ? Wrong ?



Can someone help me with this ?
I hope the questions will be understood
Thanx

Chris

[knightfly]

1 - whatever diffusion you get from the edges of slats (in addition to other effects) will be primarily in the horizontal plane with vertical slats, and in the vertical plane with horizontal slats. If I were to build something like that I'd make sure it was probably at least 12-15 feet from the mix position to avoid specular reflections, and I'd make each module relatively small (like 2 feet) and ALTERNATE them to avoid "zoning" of the effect.

2 - I believe the overall volume of space behind the panel has more effect on frequency, but it's likely that there would be some broadening of the "Q" of the trap with a variable depth - haven't built such a beast so this is purely conjecture... Steve

[RCA]

Steve,

Your message tells me that it is not good to combine 2 resonators like
I showed by the image but that was more for explaining what I ment.
I like to build the helmholts resonators both vertelcally or horizontal but I was not sure which one to choose.

I guess the horizontal slats will be the best thing to do then.

About the panel absorber:
It was just an idea which I had.
It could work, but I understand that it only will change the q-factor.

Thanx for taking the time to answer my questions.
Maybe some other members have some comments about this.
I'm all open minded and ready to learn new things in live

Chris

[Vagabond]

Not to threadsteal, but I also had a question about helmholtz resonators.

Instead of using lots of slats and slots, what if I had a 2'x4' 4" thick fiberglass board like OC703 encased on 5 sides (back panel + edges) with two panels on the front forming a single slot down the center? Would this be bad? I think it would minimize diffraction but I don't know if it would be as effective a low/mid absorber as many slots/slats. Also if I had 11.5" slat/1"slot/11.5" slat across the front, would I use 23" as my 'slat' and 1" as my 'slot' in the spreadsheets to get the right % perforation?

[RCA]

Vagabond,

First : when building a helmholtz resonator you don't have to put mineralwool on all sides, only at the rear of the unit.

If you make one center opening it could work as a low absorber but that depends on the depth of the box / opening and the width of the slat / slot
There is a nice calculator on this forum so you may calculate your options but I guess you already found it.

I think one opening could reduse some mid frequencies but it depends on the size of that opening and what frequency range you are trying to controle.

A small opening will *not* handle the ( higher) mid frequencies.
Again it depends on the frequencies.

However I guess a few more openings will be best or else you will get a lot of reflections in the room if you understand what I mean.

I'm not a pro, and have a long way to go before I will ever be.
From what I understand is a slat resonator a device which will help you to eliminate problem frequencies and still keep some live in your room.

Your design will add (TOO) much (??) live.
But it all depends on your demands and your room of course.
I tried it also but it didn't work for me.

But the first thing you have to do is calculate you problem frequencies.
Only than you know at which frequencies the helmholtz unit has to operate at that point.
Your design can eliminate the right frequencies and leave the wrong ones still in the room or another option is that you will eliminate too much frequencies and their will nothing left to add some live.

Good luck

***
For the pro's here
I hope I'm not telling lies , if so correct me

[cadesignr]

Hello RCA. What program did you use to create the graphics? Very real look to them. Nice work.

And secondly, what told you that you needed these in the first place? Since Hemholtz resonators are frequency specific, did you run some room tests that showed you needed absorption at a specific frequency? And then what determined the various dimensional aspects of your design? Thanks.
fitZ

[cadesignr]

Almost forgot. What are you using to machine the slots? Thanks.

[RCA]

Hello RCA. What program did you use to create the graphics? Very real look to them. Nice work.

And secondly, what told you that you needed these in the first place? Since Hemholtz resonators are frequency specific, did you run some room tests that showed you needed absorption at a specific frequency? And then what determined the various dimensional aspects of your design? Thanks.
fitZ

Hi fitZ,

First I made the drawings of the room mode calculator.
This showed me some problem frequencies which chould be solved by moving the mixer and the speakers to different locations.
Offcourse everything was checked by running it trough a
realtime analyzer.


After that I had still two left one low and one low-mid frequency.

For the low frequency I made calculations for a panel absorber
The helmholtz for the low-mid.
The slots are tuned to this frequency.

After this I put that room mode image into a 3D Program called Autodesk Animator which allows me to make a complete room with all the desks, speakers etc on scale.
When placed in the room you can walk through the virtual studio to see if anything is at the wrong place.
You can change all materials by a click on a button.
So you can see how your studio is going to look.

I will upload some detailed images If you like.



Chris