Wood For Slots

rsb · Post by **rsb** » Wed Aug 20, 2003 4:25 am

Just curious what types of wood you have used for your slats?

I have looked at a few options but they are all pretty expensive.

Thanks

Ryan

giles117 · Post by **giles117** » Wed Aug 20, 2003 4:39 am

I used whitewood (pine)

1x4, 1x6, 1x3

$3.12, $5.95 and $1.49 respectively

Bryan Giles

rsb · Post by **rsb** » Wed Aug 20, 2003 5:32 am

Is that x 8'? I have 2 boxes ~7' x 4' that I need to put them on.

Ryan

knightfly · Post by **knightfly** » Wed Aug 20, 2003 11:46 am

Ryan, if you're on a budget you can also use MDF - if you need extra thickness (for lower frequencies) you can laminate two sheets together. For a nicer look, you can laminate your choice of veneer onto the finished thickness. A single 3/4" sheet of MDF with a sheet of 1/8" birch or oak ply would cost about $35-40, and you'd get 8 8' lengths of nearly 6" wide "boards" from it.

If you have a table saw or radial saw and a helper (or better, three helpers :=), you can laminate a full 4x8 sheet (two 3/4" MDF and one 1/8" veneer) and then rip it to width. Always remember to set blade depth to just slightly thicker than the material, and put the finish side AWAY from the blade center. (Radial saw, good side down - Table saw, good side UP) This minimises breakout at the saw kerf.

Clean cuts lightly sanded will not only look best, but give you the most predictable results (via the calculator at the SAE site)

HTH... Steve

giles117 · Post by **giles117** » Wed Aug 20, 2003 11:03 pm

Yeah those are 8' lengths

Bryan

knightfly · Post by **knightfly** » Thu Aug 21, 2003 3:42 pm

Ryan, another way to go might be to buy 4x8 3/4" veneer-faced plywood, the oak and birch are about $50 per sheet. If you were to carefully rip a sheet into widths of your choice and KEEP THEM IN ORDER, you could put a satin varnish on them and keep the grain pattern across the entire absorber. Might be kinda cool looking, one of those things you don't necessarily see right away but when you do, it's "Whoaaa, COOL!!!

Just a thought... Steve

gearmike · Post by **gearmike** » Fri Aug 22, 2003 3:01 am

What is the recomended minimum depth for the slats?

And is there any advantage to various depths?

rsb · Post by **rsb** » Fri Aug 22, 2003 4:19 am

Thanks guys.

Knightfly I have thought about the veneer ply. I only have a skil saw at this point so that would be a lot of work. ( Not that I have not logged a few hours in so far )

Gearmike take a look at

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

Under absorbers there is a lot of good info on that Helmholtz resonators.

Ryan

knightfly · Post by **knightfly** » Fri Aug 22, 2003 4:31 am

Gearmike, more specifically here, and if you have Excel you can download the sheet to use locally -

http://www.saecollege.de/reference_mate ... mholtz.xls

Ryan, with a sharp carbide blade and some straigh edges/clamps you can make accurate cuts with a skil saw - yeah, it's more work than with a table or radial saw, but I've done it with good results... Steve

giles117 · Post by **giles117** » Fri Aug 22, 2003 6:27 am

For my Slats, I had to buy 10 - 1x4's and 10 - 1x6's

Total cost was about $90

Not bad if you ask me.

Bryan Giles

gearmike · Post by **gearmike** » Fri Aug 22, 2003 8:02 am

So it looks like volume doesn't matter in the calculations, just the depth...that doesn't seem right to me...am I missing something?

knightfly · Post by **knightfly** » Fri Aug 22, 2003 9:13 am

Yeah, I know - it's counter-intuitive, that's how you know it's probably right for acoustics

Here's an experiment you can do that will (hopefully) convince you -

Take an empty, small-mouthed bottle - a 1-quart vinegar bottle, or a 2-liter pop bottle will work - anything you can blow across the mouth of and make a tone.

Start with the bottle empty, and remember the pitch you get when you blow across the mouth. Now, add water til you can still tip the bottle on its side far enough to expose about 1/3 of the bottom to air instead of water.

Hold the bottle upright again, and blow across the mouth. Note the pitch of the tone you made.

Now, again tilt the bottle until the water is NOT QUITE running out - you don't want to lose ANY water -

Again, blow across the mouth of the bottle (you'll need to do this from the side instead of the front, so you can get the correct angle to make a tone.

Note that the pitch is noticeably LOWER with the bottle horizontal - In fact, other than loudness, it should be the same tone you got with the bottle empty. Which parameter changed? You still have exactly the same volume of air in the bottle (as long as you didn't spill any), yet a lower pitch when the air column is longer.

'Nuff said?

That's why my general rule of thumb for acoustics is "If it doesn't make sense at first, it's probably right"... Steve

knightfly · Post by **knightfly** » Fri Aug 22, 2003 9:30 am

Mike, I missed this question -

"What is the recomended minimum depth for the slats?

And is there any advantage to various depths?"

Yeah, If the slats are too thin they would tend to act somewhat as a panel resonator. I'm not sure exactly what that would do, so I'd stay with at least 3/4" material - there are enough variables in acoustics without "tugging on Superman's cape" -

Increasing depth of either the slats or the cavity lowers the frequency. Plug in 18mm for slot depth, then see what happens to resonance when you change it to 36mm (like 2x lumber, or 1.5")

Practical limits for some of the dimensions would dictate just how far you can go - still, the advantages of slat resonators are several. They don't suck up all the highs, so you can get rid of "tubbiness" without losing the "shimmer" - makes 'em great for drum booths for example - you can dial out some of the 300 hZ crap from the kick drum without losing all the cool sizzle from that vintage Ziljian you found at the garage sale... Steve

gearmike · Post by **gearmike** » Fri Aug 22, 2003 1:43 pm

Ok,

So I'm starting to understand this....I take it maybe volume affects the amount of absorbtion?

Anyway, here's an idea for you.

In order to make a slat wall operate into the sub-bass region, you would have to have a cavity depth of like 8 or 10 feet right? What if you made a box where the slats were on the top side? so the wall that faced into the studio was solid, but the top side (facing the ceiling) had the slots? You could get a cavity depth of say 7 feet in a room with 8 foot ceilings.

Any ideas on performance? Does it sound like I understand the concept, or am I not making any sense?

knightfly · Post by **knightfly** » Fri Aug 22, 2003 3:34 pm

Mike, that sounds like an idea with possibilities, but you'd probably be better off posing that question to Barefoot in the Acoustics forum, so ALL of us can learn something.

My gut feel is that it should work, but I think it would also worsen the Transmission Loss of the wall in that freq range; it has to do with the restrictions of the slats causing the inner wall of the trap to act as a third leaf of the wall.

Like I said, Barefoot's the guru on this sort of stuff, why not just copy your last post and paste into a Q for the Guru? Maybe do a rough drawing so we can slice and dice it from there... Steve