Quick absorption/bass trap question

[Glenn Kuras]

Broadband "bass traps" are items that cover more of the over all frequency range. A tuned bass trap is some thing that is targeted to a certain frequency range. Smaller rooms (99% of the rooms these days) need mostly broad band to start and then you could (if need be) follow up with tuned traps. In my option though they are all "bass traps".

This is off our education page.GIK Acoustics presents Acoustics Primer: Some Basics on Acoustics.

b) Rigid Fiberglass and Rockwool, Bass thru High Frequency Absorbers

Treatments constructed from Rigid Fiberglass and Rockwool are broadband in nature – thus they tend to deal with the entire frequency range. They are a very cost effective manner in which to treat a room. Lean towards densities of 3pcf (pounds per cubic foot) for higher and mid frequencies – and 6pcf to tame more of the low frequencies.

Placement of these traps with an air space between them and the adjacent surface increases the trap’s effectiveness. In the higher density materials – these can be very effective at low frequencies if placed straddling dihedral and trihedral corners.

These traps work on the principle of sound energy being converted into heat as the sound passes through the insulating material.

c) Narrow Bandwidth Bass traps

Panel and Helmholtz bass traps deal with low frequencies in a fairly narrow bandwidth range. Thus these traps are usually the last resort, used specifically to deal with a problem frequency left in a room, after broadband applications are in place.

Panel traps are constructed as sealed chambers – and require that “air-tight” construction in order to operate properly. Should you lose the seal over time – you also lose the effectiveness of the trap. A panel trap can be constructed to effectively deal with about an octave (1/2 above and below the traps center frequency) by installing rigid fiberglass behind (but not touching) the back of the panel. If this material were to touch the panel – it would not be allowed to vibrate freely – and thus would fail at it’s primary task.

Helmholtz traps as constructed with slats of wood placed over framing members. The frequency that these traps can handle is determined by the depth of the trap, the width and thickness of the slat and the slot left between adjacent slats(the slot).

With a deep depth behind the slats – and very small slots – these can be constructed to handle very low frequencies.

Again, the placement of rigid glass materials behind the slats helps to trap about an octave around the center frequency of the trap itself.

A Helmholtz trap can be constructed as a broadband trap if it is designed as a splayed trap – as well as through the use of varying the slot widths in a flat trap.

[The Magic Hoof]

I have some tri traps, some 244s and a monster bass trap. Would these count as 'broadband' traps? I think I recall Frank saying somewhere that the GIK traps are made to absorb more than just bass frequencies.

[Weasel9992]

Originally Posted by The Magic Hoof

I have some tri traps, some 244s and a monster bass trap. Would these count as 'broadband' traps? I think I recall Frank saying somewhere that the GIK traps are made to absorb more than just bass frequencies.

The 244 is a true broadband trap that absorbs around 2 times as much at 125Hz as 5Khz.. The Tri Trap and Monster Bass Trap are more like traditional bass traps that absorb 2.5 to 3.5 times as much at 80Hz as they do at 4Khz.

Frank

[The Magic Hoof]

Perfect, thanks Frank thumbsup

[ciro]

Looking at GIK site, I see the 242 recommended for the reflection points:

"Ideally mounted at first and secondary reflection points in a room the GIK 242 Acoustic Panel has the same equal absorption as the GIK 244 from 4000Hz down to 250Hz."

I don´t see a 'without' "limp" membrane type option for RFZ.
How it works?

Ciro

[ciro]

Originally Posted by ciro

Looking at GIK site, I see the 242 recommended for the reflection points:

"Ideally mounted at first and secondary reflection points in a room the GIK 242 Acoustic Panel has the same equal absorption as the GIK 244 from 4000Hz down to 250Hz."

I don´t see a 'without' "limp" membrane type option for RFZ.
How it works?


Ciro

Sorry for the "bump", maybe you have not read (I wrote it saturday,bad day for post I think...)

Tks again

Ciro

[Weasel9992]

It's just a 2" absorption panel, but by design it rolls off pretty dramatically below 500Hz.

Frank

[speerchucker]

Kudos to Glenn Kuras.

That is some of the most accurate & concise info I've ever seen online, re this topic.

There is so much misinformation & nonsense to be found, especially on these forums (and from folks who should know better) it practically makes my brain explode.

This guy knows what he's talking about.

[Glenn Kuras]

Originally Posted by speerchucker

Kudos to Glenn Kuras.

That is some of the most accurate & concise info I've ever seen online, re this topic.

There is so much misinformation & nonsense to be found, especially on these forums (and from folks who should know better) it practically makes my brain explode.

This guy knows what he's talking about.

Thanks man we really do try.

[xaMdaM]

Originally Posted by Glenn Kuras

Thanks man we really do try.

Most wives would say we're a VERY trying lot...

[Seamus TM]

I have a question about the placement of absorbent in a perforated panel trap.

These are standards that I have found:
Panel Trap: Absorbent does NOT touch the panel.
Slot Absorber: Absorbent DOES touch the slats.

So, what about a perforated panel?
Touchy or no touchy?

Thanks,
Seamus

[Brainchild]

The perforated panel works the same way as the slotted panel, so the absorbent should be touching the panel.

[Seamus TM]

That's what I figured.

Thanks a lot,
Seamus

[SAC]

Also note that a resonant panel absorber, unlike the slot and perforated absorbers, is not a Helmholtz absorber.

(Edit: Mentioned in case anyone seeks information on how they work...)

[Seamus TM]

True enough.