Cavity Resonance?

[Jack Russell]

Here ya go Jack. Its quite easy and looks fantastic. One thing though, the interior gap must be sealed at the ends, floor and cieling(like a bottle).

http://www.saecollege.de/reference_material/index.html

Aha! Bingo, I figured it out. A slot resonator is also known as a Helmholtz resonator. That might be the answer!

Thanks, man!

Also: I assume a slot resonator is the same thing as a slat resonator. Yes?

Now, if I can just resonate my slut....

 

[RICK FITZPATRICK]

Aha! Bingo, I figured it out. A slot resonator is also known as a Helmholtz resonator. That might be the answer!

How bout a wall of Broadband Slot resonator-Panel Absorber-Polycurve Slat Diffuser instead?
fitZ

 

[Jack Russell]

How bout a wall of Broadband Slot resonator-Panel Absorber-Polycurve Slat Diffuser instead?
fitZ

Good god, man. You must be obsessed!

That is really frikkin' cool though. Thanks for taking the time to spec that out. I will have to think about it awhile. That would do the trick for sure.

Cheers,
JR

 

[TexRoadkill]

A quick and dirty way if you don't want to do all the math is just put some 703 in the space between the studs. Cover the wall with frabric. Then rip up some 8' strips of 1/4" or 1/2" plywood in 6" widths. Nail them up going horizontally across the studs. Leave a random gap between slats of about 1/4"-1". If you make the gaps into a pattern it won't look like your just a sloppy carpenter.

Check out the walls at Blue Bear's studio http://www.bluebearsound.com/gallery_studio.htm

 

[Jack Russell]

Thanks, Tex. That is a great idea also.

At this point, due to pretty significant time and money pressure in my life (life sucks...then you die ), and the fact that I need to "finish" my studio/rehearsal room soon so I can get by band to start using it, here's what I'm doing:

1) I filled the space with CertaSound insulation, made my Certainteed. This appears to be cheaper than 703, or at least it is what I can get locally today.

2) I have laid burlap over every other stud, from 6 inches to 60 inches up from the floor. So I have four 15" by 54" burlap-covered openings. The rest I will just go ahead and cover with drywall.

It isn't ideal, but I could revisit this later and upgrade it.

What do you think? I wonder if the 4 holes are enough space though. Apl said it should be one-third (see above).

 

[apl]

22.5 ft² out of 176, around 18%. I'd try to do a couple more if you could.

 

[Jack Russell]

22.5 ft² out of 176, around 18%. I'd try to do a couple more if you could.

Thanks. Yeah, I think I can make that happen. I'll work on it.

You da man, Apl!

 

[apl]

You da man, Apl!

Unless it sounds like squat.

 

[Jack Russell]

Unless it sounds like squat.

That will happen when I christen the room with my amazingly sweet voice on my recordings.

Actually, I have another question about the posts above. If I have 100 sq. ft. of wall space, and leave openings in the wall that total 33 sq. ft. (to achieve the one-third rule), would I lose more space if I cover the openings with the strips of plywood? In other words, would the plywood act as wall space, reducing the amont of the 33 total sq. ft. of opening?

 

[apl]

That will happen when I christen the room with my amazingly sweet voice on my recordings.

Actually, I have another question about the posts above. If I have 100 sq. ft. of wall space, and leave openings in the wall that total 33 sq. ft. (to achieve the one-third rule), would I lose more space if I cover the openings with the strips of plywood? In other words, would the plywood act as wall space, reducing the amont of the 33 total sq. ft. of opening?

If the strips are small, they let most everything by. The math is complicated.

 

[Jack Russell]

If the strips are small, they let most everything by. The math is complicated.

Haha. I'll bet!. I got an 'F' in caclulus in college....

Refering to what Tex said above: "Then rip up some 8' strips of 1/4" or 1/2" plywood in 6" widths. Nail them up going horizontally across the studs. Leave a random gap between slats of about 1/4"-1"."

Would 6-inch strips be small enough? I'm leaning that way because having a big wall of burlap by itself might look like crap. Or was Tex talking about the slat resonator approach? That would more than I can handle, since, correct me if I'm wrong, it requires an airtight enclosure.

 

[apl]

Haha. I'll bet!. I got an 'F' in caclulus in college....

Refering to what Tex said above: "Then rip up some 8' strips of 1/4" or 1/2" plywood in 6" widths. Nail them up going horizontally across the studs. Leave a random gap between slats of about 1/4"-1"."

Would 6-inch strips be small enough? I'm leaning that way because having a big wall of burlap by itself might look like crap. Or was Tex talking about the slat resonator approach? That would more than I can handle, since, correct me if I'm wrong, it requires an airtight enclosure.

Maybe you could make faux draperies that would hang over the gaps.

 

[TexRoadkill]

I was talking about a basic slat resonator. If you are asking if 6" slats would be okay then yes. The reason they use wood instead of drywall is because you want some reflection and wood usually has a pleasant and 'warm' reflection. Nothing has to be airtight. The slats themselves would make any airtightness impossible. The principle is that some of the highs and high mids are bounced off the slats and the lows and low mids are absorbed in the trap in back. You end up with good low end absorption and some reflection in the higher end so the room isn't completely dead and unnatural sounding.

You could try dieing the burlap. I've never tried it but if you make it a dark color it should dissapear behind the wood or drywall.

 

[RICK FITZPATRICK]

Nothing has to be airtight.

Hello Tex. Say, I know what you are saying, but there IS a principle here that, from my understanding, does require "airtight" ness. And thats because the slots act like the neck of a bottle, which when the air in this slot is excited by soundwaves, act on the air in the "box", which acts like the air in a bottle. Even though an open bottle is not in effect, "airtight", if you cover the opening with your lips and blow, THEN, it is "airtight" and you can't blow air into it. But blow ACROSS the opening, and it will resonate at a certain frequency. I believe this is because the air in the bottle, or a Hemholtz resonator BOX, acts like a spring, which if is NOT airtight BEHIND the slats, will not perform as it should. Some one tell me if this isn't correct, but I think it is.
fitZ

 

[apl]

The Helmholtz resonator is a cool device. It's able to work at very low frequencies using a small volume. It works differently from say, a 1/4 wave tube. Using the pop bottle example, the slug of air that sits in the opening acts like a mass sitting on a spring, the spring being the volume of air inside the bottle. The problem is that it's a very narrow band device; it has a high Q. You can spread out the effect by adding damping to the system which is usually fiberglass. But that reduces it's effectiveness.

This concept is applied to ported loudspeakers. The slug of air in the port bouncing against the spring of the air in the enclosure has a resonant frequency. Some fiberglass is stuffed into the cabinet, and then that frequency is tuned so that as the woofer's ability starts to taper off as frequency goes down, the resonator starts to pick up the slack, extending low end response substantially.

But in this case, he's got tons of available volume for absorption, so there's no point in trying to tune it. In fact, with that huge a volume, he'd probably be at like 1 or 2 Hz, which is useful for damping Space Shuttle launch sounds that you can't hear anyway.

 

[RICK FITZPATRICK]

he'd probably be at like 1 or 2 Hz, which is useful for damping Space Shuttle launch sounds that you can't hear anyway.

Excuse me apl, but what are you saying here? The discussion was about slot resonators, which from my understanding of John Sayers design, uses vairied width slots and slats, which supposedly will broaden the bandwidth of low frequency absorption, no? I still don't understand what you are implying though. Could you elaborate. I'm certainly no expert and appreciate your status as one. Thanks

 

[apl]

Excuse me apl, but what are you saying here? The discussion was about slot resonators, which from my understanding of John Sayers design, uses vairied width slots and slats, which supposedly will broaden the bandwidth of low frequency absorption, no? I still don't understand what you are implying though. Could you elaborate. I'm certainly no expert and appreciate your status as one. Thanks

I'd have to read all that stuff, but if it can be done simply, I think it's better. That why I like realtraps if you got the money, 703 triangles if you don't. And I'm too tired to go read it now. I'm sure they work but they're a lot of work, too.

 

[RICK FITZPATRICK]

I'm sure they work but they're a lot of work, too.

I'm sure they work too, but what I'm not understanding is what made you think a wall of slot resonator would only absorb frequencies so low that it wouldn't matter because you can't hear them anyway. I do agree about the corner "superchunks", but just the same, I would think this space he has could be acoustically usefull if you knew what would be the best application for it.