Lighter bass traps for small budgets

[avare]

Originally Posted by Weasel9992

What I mean is using a gap to expand low end extension. In rooms where there's not a lot of wall space, getting all the low end extension possible is critical.

Okay, I am still confused. As I am following this exanple, you have limited wall space, not depth. Correct? Using an air gap is a function of the absorbent material and desired low end absorption desired. It has nothing to do with gaping (I hope that is a verb) the material.

I think there is a gap in our understanding,
Andre

[PaulP]

Originally Posted by PaulP
For the low frequencies, if I understand things correctly, the thickness of the
absorber determines the bandwidth of the absorption, and the air gap (plus
half the thickness of the absorber) sets the center frequency.

Originally Posted by avare

The thickness determines the low frequency cut of point. Thickness includes
the material and the air gap. The larger the air gap, the larger the dip at
multiples of wavelength/2 frequencies.

Ok, thanks for the clarification. For some reason I was hung up on the middle
of the absorbant with a sort of bell curve on both sides. I can now see that
it's at the front of the absorbant where the most/lowest absorption takes
place. And whatever frequency is quarter-length at that distance is
the lower limit.

So the thickness, not counting the air gap, affects frequencies above the
cut-off point more or less equally ? Counting the air gap, those frequencies
that are nulled by their reflections inside the absorbant will be absorbed
only to the extent that there is thickness on either side of the null point.

I think.

Paul P

[avare]

Originally Posted by PaulP

So the thickness, not counting the air gap, affects frequencies above the cut-off point more or less equally ?

Yes.

Counting the air gap, those frequencies that are nulled by their reflections inside the absorbant will be absorbed only to the extent that there is thickness on either side of the null point.

Yes, bearing in mind that nulls do not appear significantly with gaps up to around 2:1, have been used up to 5:1 in engineeered absorbers (BBC A1 as already mentioned) and 15:1 is quite normal where space is available and initial reflections are not significant. The l15:1 is typical of the air to gap ratio in suspended ceilings.

If the previous sentence seems long winded, it is because the 2:1 myth is so widespread, and I want to make it clear that it is just that; a myth.

Andre

[takman]

ok im bringing this back to life because im trying to figure this out here....

I'm debating on doing a corner trap 3 different ways here..

#1 the most common ( i can only go out 1 foot from the corner due to restrictions like windows, outlets etc) just using one piece of insulation for the example...they will be stacked to the ceiling of course....





# 2 same as #1 just with material removed leaving a 2" gap on the sides. with #1 i have a 1' x 1' by 17" wedge..with only 17" of material exposed.

With 2" gap on the sides, i have less material but 27" of the material is exposed.




# 3 extend front out, since i dont dont have room on the wall, but i do have room to extend into the room a bit...this would give me 35" of total area exposed with the added material. But its probably the same amount of material as #1. But its deeper in the front..which would give better LF absorption?



so which one would be better?

[avare]

Which one would I recommend?
Number 1.

Andre

[takman]

Originally Posted by avare

Which one would I recommend?
Number 1.

Andre

Nooooooo...i did #2

But heres the thing.....

.....i built the frame so its entirely open on every side....Wont that be more efficient because the two sides that would normally be up against the wall un-exposed...will now be exposed? more material vs. more exposure??

i have read a number of your posts about the whole air gap thing..and im still confused here....