Slot Resonator Question

[AlexT]

I am in the process of building a Slot Resonator along a Tracking booth wall, which is 6ft wide x 8ft high.
Airtight framing is done and the insulation with cloth backing is in place.

Getting ready to put the timber slats on…
…but realized that there are (insulation) lumps that are pushing up against (touching) the slats.

Is this defeating the purpose of the slats and a total NO-NO?
Should there be air gap between the slats and the insulation, if so how much?
Is there a practical technique to doing this?
Did some search but not much specific to this topic.


Oh BTW my studio project has started and have loads of pix to share.
Will post them all soon.
Thanks to Steve, John and all the others around here.

[Dan Fitzpatrick]

alex, sorry i can't help with your question.

i'm just writing to say, i've been wondering about your project and I WANNA SEE PIX!!!!!

[the dreamer]

I think it's okay for the wool to touch the slats as this is no paneltrap which functions on a "movement-priciple" which is obstructed/damped by direct contact.
IOW it's the air in the cavity that resonates and not the slats.

[knightfly]

Slat resonators should have the cloth AND insulation touching the slats; not only does this provide the correct design function of controlling the air flow through the slots, it also dampens any ringing that might occur at resonance so it minimises returned energy at trap design frequencies.

Generally for most applications you want roughly half the total depth of trap to have absorption material; more will widen the Q of the trap (bandwidth) while lowering absorption a few dB; less insulation depth will NARROW the Q and INCREASE absorption at design frequency.

Moving the absorbent AWAY from the slats, besides losing the damping effect, will also make any calculations unpredictable. Not saying the trap won't do SOMETHING, it's just that the only way you'll know WHAT it does is to measure the room before and after. Not too promising... Steve

[AlexT]

Thanx Steve,
After a whole bunch of searches I found couple of your other posts regarding the subject.
Great info.

My main reason in building this angled resonator is to prevent the build up of standing waves and flutter.
I will be tracking vox, drums, guitars etc. in this room

Room dimensions are
6’ x 9’-6” with sloped ceiling averaging 8’ (8’-5” to 7’-6”)

Slat wall is along the short (6’) side of the wall angled from 3” to 16” (wall to slat frame)
Haven’t yet figured out the slat/slot depth etc.
Any recommendations before I go any further?
Alex

[knightfly]

If it's not too late, I'd consider putting a divider into part of the trap to separate the air spaces behind the slats; then I'd calculate that section for a center freq of 300 hZ. (or, you can just use the average depth and choose slat width/thickness and slot width for 300 hZ center)

Reason - kick drum primary shell modes run right at 300 hZ, you'll need to pull some of that out for drum recording... Steve

[AlexT]

If it's not too late, I'd consider putting a divider into part of the trap to separate the air spaces behind the slats...

Oh boy Steve,
It took me about an hour just to stretch that black cloth (due to my dumb mistake…:oops: 2” short measurement… thank God it was the stretching type cloth).

Would it be a problem to do this without dividing it into a separate septum?
What other frequencies should I tune this room to vox, acc. guitar?

I know some of these are dumb questions... but I get frustrated when it comes down to calculations.
Thanx,
Alex

[knightfly]

You can get your existing construction to work from approximately 230 hZ up to about 540 hZ (average depth being 9.5") by using 2.5" wide, 3/4" thick slats spaced 1/2" apart - If you were to space the slats at the bottom and top 2 feet or so at 1/8" instead of 1/2", you could get some usable effect down to about 120 hZ.

The lack of internal dividers will keep the helmholtz effect from being as pronounced at different frequencies, but generally this is NOT a bad thing - building the slats out at those sizes/spacing should work well for ALL your intended uses.

nominal 1x3 lumber is the exact size you need, which is partly why I used those dimensions - less work than ripping each slat to width, unless you have access to a table or radial saw.

Acoustically, spacing of the slats isn't real critical; but you should keep them as close to the recommended spacing as possible or it will not only change the frequency range a small amount, it will also look wierd if they're uneven.

HTH... Steve

[sharward]

i've been wondering about your project and I WANNA SEE PIX!!!!!

Field trip!

[AlexT]

i've been wondering about your project and I WANNA SEE PIX!!!!!

Field trip!

Hey Dan, Keith,
I’ve been resizing whole bunch of pix to post on my construction thread.
Hopefully will get to them this evening sometime.
Field trip sounds good!

[AlexT]

Thanx Steve,
That is great info.
Using one-size slats will make everything a whole lot easier (plus will look better).

...If you were to space the slats at the bottom and top 2 feet or so at 1/8" instead of 1/2", you could get some usable effect down to about 120 hZ.

Is this 2 feet altogether (1 ft top, 1 ft bottom)?

[knightfly]

No, you should keep in mind that low frequency waves are BIG - I meant 2 feet at the bottom, and 2 feet at the top, with the mid section back at 1/2" spacing to pull out more mid frequencies... Steve

[AlexT]

... you should keep in mind that low frequency waves are BIG...

Got it!
Thanx Steve