Salem Oregon conference center studio

[Guit-picker]

Hey! Thanks John! I really like this! I will have to go through a bit of a learning curve and will have some questions. I need to understand more details than I can determine with a 2-dimensional drawing.
Starting with the first stupid questions, but the rectangular in your drawing are pieces wood, right?
Then, does the depth of the pieces matter? I'm thinking the depth of the cavity is the only concern, right?
Would I put a layer of rockwool or OC703 behind the slats and/or on the back wall?
I don't know how to calculate the depth of the cavity since it is at a 45 degree angle. Would I just choose the greatest depth in the calculator?

Thanks so much for your nudge. I REALLY like the idea!

-Ron

[John Sayers]

Ron, the squares are vertical 6" x 2"s with a 1/4" space between them. They are at 45 degrees from the side walls.
The depth is the same as you've already built and because they are mounted across the corner the depth varies.
Check the photos I posted.

cheers
john

[Guit-picker]

Yes, thanks John! I appreciate your attention. Please bear with me. I looked again at the photos - very nice, I would add.

So how can I use the calculator with different "depth from wall" all across? Do I use the deepest depth (i.e. the corner of the wall) in the calculator? I am confused with the differences in the drawing included in the calculator and the 45-degree drawing. Should I assume I would use 2" slat width (or 4" on pieces that are butting together) and 6" for slat depth in the calculator?

What I'm getting at is the difference in the two examples, where one is on a flat wall with flat slats and your corner example has really deep varying slats, some with no gap and some with gaps and each one is a different depth from the wall. Perhaps I should take all of the individual depths and average them?

No arguing is intended here, but I'm just trying to understand how to apply the calculator with all these variables. I am really intrigued by your design and want to go further with it!
By the way, where can I link to the calculator?

Best Regards,
Ron

[Gregwor]

Here is a post John made describing his amazing device in more detail:
http://www.johnlsayers.com/phpBB2/viewt ... or#p135094

By the way, where can I link to the calculator?

http://johnlsayers.com/Recmanual/Images ... perial.xls

I'm so glad John shares his designs in such great detail!

Greg

[Guit-picker]

Thanks Greg! There's a wealth to study in that thread you shared. Just what I need. I am still unclear about how to apply the calculator in the corner application, but I will start with a first-draft drawing with what I understand so far after reading the thread.

I'm so glad John shares his designs in such great detail!

...and so am I!! Thanks John!
I don't know what I'd do without this forum!

Gratefully,
Ron

[Gregwor]

I am still unclear about how to apply the calculator in the corner application

For a Helmholtz design, just realize that the distance in the equation is the distance from the slot to the wall. Like John said, because it is in a corner, each slot will have a different distance to the wall (with the max distance being the slot in the middle of the device). This is awesome because it makes the device cover a larger range of frequencies.

Greg

[Guit-picker]

Here is what I drew up from what I could ascertain from John's bass trap design that he graciously offered. I am using dimension lumber, starting with 2x4" on the outsides, switching to 2x8 and finally two pieces of 2x12 in the middle. These are the dimensions his drawing looks like (although he only specifically mentioned 2x6). This is going to be REALLY heavy, but that's no problem. I intend on facing the exposed areas with birch skins (I have experience with this and it's not hard at all), which should look great! I will trim the outside with solid birch for appearance.

Wood_Bass_trap_A.jpg

I did some calculating and it looks like this will be close to 1/3 the price of the hanger design! It should be easier to build too and in the end look better. Here is another view from above with the framing removed for clarity:

Wood_Bass_trap_B.jpg

So to weigh the difference: ... let's see.... cheaper, easier to build, better trap, looks better! Gee, which way to go?!
I want to put the dimensions through the calculator for each gap and see what it yields. I'm quite sure the differences in the lumber width is the right thing to do, believing that it was drawn that way for a reason. My intuition is that it widens the frequency range of the trap. Please correct me if I'm mistaken.
How about the insulation in the back? Should I line the wall with a layer of 3" Roxul Safe-n-sound? It's readily available and cheaper than shipping in OC703.
I'm pretty jazzed about this design!!
-Ron

[Gregwor]

That looks amazing.

We're going to have to rely on John here to advise on the insulation and to confirm that your design matches his vision for the device.

Great work and yeah, I'm very impressed with how awesome it looks. I hope you'll share an .skp file of that device when you're done so that others like myself could implement it in one of my personal rooms!

Greg

[John Sayers]

Hi Ron that looks great. You must line the back of the timbers with black cloth so you don't see through the spaces.
Leave the center slots till last and toss all your insulation offcuts into the cavity

cheers
john

[Guit-picker]

I used the handy Hemholtz calculator to calculate each of the 19 slots individually to see what it would show for absorption frequency. Not sure if this is the correct approach, but it's interesting and here is a graph of it (from left to right slots):

Ctrl_Rm_Bass_Trap_Hemholtz.jpg

Any comments on this?
-Ron

[Gregwor]

It looks awesome!

I'm just confused about John's recommendation to fill the cavity with insulation. Everything I've ever read about Helmholtz devices is that filling the cavity really widens the Q of the device but it drastically reduces the absorption.

Maybe I'm misunderstanding his design. Anyone care to chime in on this?

Greg

[John Sayers]

Take a coke bottle and blow over the neck and it will produce a note.
Now add some insulation to the bottle and blow over the neck and the note is gone.
It's been absorbed.
That's how helmholtz resonators work to reduce the note in your studio.

cheers
john

[Waka]

I'm just confused about John's recommendation to fill the cavity with insulation. Everything I've ever read about Helmholtz devices is that filling the cavity really widens the Q of the device but it drastically reduces the absorption.

Maybe I'm misunderstanding his design. Anyone care to chime in on this?

I would also like a little more information about this if you get a minute John.

So in your Recording Manual (I know it's quite old now!) you show that you have a thin layer of insulation behind the mouth of the slots, and the rest of the cavity is empty (but sealed).

Are you saying that a fully filled cavity is simpler to achieve (as there isn't any need to glue/attach the insulation to the slats) but still has the same effectiveness? I ask because I've also read that over damping the cavity can negatively affect the absorption.

I suppose chucking only low density off-cuts into the cavity and not compressing them would leave a lot of gaps between them and potentially prevent over-damping.
Obviously, you use these all the time! So they must work, but can you expand on how heavily/compactly you fill the cavity?

Thanks,
Dan

[John Sayers]

I suggested to add offcuts to the cavity in this corner trap as it's cheap, easy and simple.
When I add angled slots, like on side walls we just line the cavity walls with insulation.
When I add slots to an inside out wall we just add insulation as usual set to the back of the cavity.

cheers
john

[Guit-picker]

A couple of months ago we rang the control room for the first time. It took a while to figure out the whole setup and I hope we did it right. In the meantime, I got busy on the rear bass trap design and didn't get around to finding a cloud to post the first data. So for what it's worth, here is the first ring data. It would be nice if someone with experience could take a look at it and tell me if it looks right. Stuart was a big help when we started.
We haven't figured out all the tools, and graphs nor their meanings yet. A lot of fumbling, but I think we rang it right.

Here's the link - first ring with an empty control room, except for front soffit framing.
https://drive.google.com/file/d/1YupEGv ... sp=sharing

Please let me know if this looks right for my first worst-case ring.