Author Topic: Bass trap build (at last!)  (Read 17200 times)

Offline Gerhard

Re: Bass trap build (at last!)
« Reply #15 on: January 17, 2011, 07:20:37 PM »
Now this may very well be a stupid question! :-[

Were the think pink rolls still in their plastic bags? I'd imagine so in light of your valid concerns in the "Isotherm vs Think Pink" thread about damping material and the use of "open" fiberglass in bass reflex speakers. So the question now is - in my head at least - what made the difference? Is it that "something" (anything really) placed in the particular locations in the room - corners probably - would have made a difference? I.e. the offending sound waves were not absorbed/turned into heat but were scattered instead. And if so, what would the effect be of having both "something" in the corners and something with acoustic absorption properties.

I ask this for my own edification and probably others' as well since I like to know what I will have to do in my room.

Offline JimGore

Re: Bass trap build (at last!)
« Reply #16 on: January 18, 2011, 07:02:13 AM »
Hi Gerhard,

If you just place anything in the corner it doesn't absorb the bass - it just reflects it back in a different way.  The think pink is still in the plastic.  That being said, the bass doesn't care about the little bit of plastic - it goes right through it.  Midrange and treble frequencies do however mostly bounce off as they don't have the energy to pass through.

Regards,
Ian.

Offline iondb

Re: Bass trap build (at last!)
« Reply #17 on: January 18, 2011, 08:09:48 AM »
That looks good.  Also, a question about bass traps.  I have a very small room for listening. Would a material bag with pieces of think pink work in the corners, right behind the speakers (almost against it)?  Or maybe the opposite corners from the speakers?

Online DRNB

Re: Bass trap build (at last!)
« Reply #18 on: January 18, 2011, 09:13:42 AM »
That looks good.  Also, a question about bass traps.  I have a very small room for listening. Would a material bag with pieces of think pink work in the corners, right behind the speakers (almost against it)?  Or maybe the opposite corners from the speakers?

Material bags with Think Pink I will work. And it will work in any corner, behind or opposite. I would personally put it in the corners behind the speakers.

Main thing is for bass absorption you need a fairly high density. So a easier product to work with is something like enegylite or rockwool, mainly because it doesn't need to be compressed. I've build a few basstraps using Think Pink, and would in future rather look at using one of the other mentioned products.

http://www.insulpro.co.za/energyliteIP.htm
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline ByronH

Re: Bass trap build (at last!)
« Reply #19 on: January 18, 2011, 09:44:16 AM »
Would IsoTherm serve well as a safer alternative? Also, how susceptible do you think these traps would be to pests such as rodents and mildew, mould, etc?

Online DRNB

Re: Bass trap build (at last!)
« Reply #20 on: January 18, 2011, 10:16:19 AM »
Would IsoTherm serve well as a safer alternative? Also, how susceptible do you think these traps would be to pests such as rodents and mildew, mould, etc?

Would work fine, but just as Think Pink the density is lower than that of EnergyLite, Rockwool and other Ridged Fibreglass products, which means you need to find a way to compress it, like with e frame Ian is building. Take a look at Ethan Winters web page.

http://www.realtraps.com/art_measure.htm

http://www.realtraps.com/art_measure.htm

http://www.radford.edu/~shelm/acoustics/bass-traps.html

http://www.ethanwiner.com/basstrap.html

There are so much reading in this regard, its just not true.
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline fdlsys

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Re: Bass trap build (at last!)
« Reply #21 on: January 18, 2011, 11:04:02 AM »
If I may;

@iondb: Creation of the audible standing wave ("bass booming") on lower frequencies is in function of the frequency and the length of the room and most effective use of bass traps usually requires experimenting.

Most efficient bass-trapping, especially in the larger rooms where multiple standing waves may occur, is usually done by either having different types (material density) of traps, or by building traps that combine materials of different densities, usually packing/rolling them into some form of "sandwich". Ian's favourite "dog blanket" would be one of the denser ones that would go closer to the middle of the sandwich.

In the recording studios, it is perfectly normal to find the acoustic resonators (google Helmholtz) that are the most efficient in fully stripping not only the bass boom, but also midrange, etc. (smaller rooms).

In case of Clubs and similar closed spaces where eardrums are pushed to the max, it is not unusual to find combinations of Helmholtz resonator based panelling, and passive bass traps that often contain material as dense as strips made of gypsum boards or chipboard, either inside the sandwich, or in the double-wall cavities hanging loosely (fake walls).

To come back to planet Earth; for our so-so typical listening room scenarios, what Ian is doing is perfectly good enough. Sandwiching some dog blanket in the middle and packing the fibre(ous) material around it in such a way that it's denser closer to the middle, and looser towards the outside would increase the frequency bandwidth of the trap.

Finally; I firmly believe that all artificial fibre material that is extruded from raw mineral or other inorganic materials should be avoided always, no debate. Problem is that inorganic fibre is brittle and it keeps breaking all the time, often turning into miniature particles that end up suspended in the air, and eventually in our lungs.

IsoTherm on the other hand is a Polyester fibre. It does not break off, and even if you intentionally turn it into "dust" and breathe it in - the fibre particles are not "sharp" and do not damage the lungs.

To give you an example of exactly how bad the materials like ThinkPink or traditional fibreglass are - responsible speaker manufacturers have stopped using these back in the early 80s even for the sealed (compressions) enclosures!
Why? Two reasons:
- If you open the speaker box (servicing) the fibre particles will escape into the outside air
- Particle dust created inside the sealed boxes WILL penetrate the porous spider/spring material of the speaker and end up in the coil-magnet gap.

Moral of the story: Use the organic soft fibre materials, forget about the rest.

@ByronH: All manufacturers of all types of these materials (incl. organic) claim that they are mildew/rot resistant, mainly because the primary intended use for these is thermal (and acoustical) insulation, so this resistance was a design objective.

Final word: Even though sheep's wool is the nature's ultimate and perfect fibre material for all purposes, it is NOT to be used for the open speaker boxes or bass traps. The reason is that it is extremely attractive to all sorts of pests (attracting even more pests) so one would have to treat it on regular intervals with insecticide.
For sealed boxes however (assuming that you treat it before sealing the box) it's a true miracle damping material. Non-uniform fibre, varying natural density, very flexible thus easy to pack into rolls/sheets of desired density. Typically, you would need 1/3 less sheep wool to achieve the same damping effect on midrange-high FQs compared to using the man-made fibres.

Mike
« Last Edit: January 18, 2011, 11:15:48 AM by fdlsys »
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Offline JimGore

Re: Bass trap build (at last!)
« Reply #22 on: January 18, 2011, 11:10:02 AM »
Thank you Mike.  Very informative.

Ian.

Offline fdlsys

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Re: Bass trap build (at last!)
« Reply #23 on: January 18, 2011, 11:19:00 AM »
A pleasure Sir!
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when you’ve lived a little. Miles Davis

Online DRNB

Re: Bass trap build (at last!)
« Reply #24 on: January 18, 2011, 01:22:13 PM »
Creation of the audible standing wave ("bass booming") on lower frequencies is in function of the frequency and the length of the room and most effective use of bass traps usually requires experimenting.

Most efficient bass-trapping, especially in the larger rooms where multiple standing waves may occur, is usually done by either having different types (material density) of traps, or by building traps that combine materials of different densities, usually packing/rolling them into some form of "sandwich". Ian's favourite "dog blanket" would be one of the denser ones that would go closer to the middle of the sandwich.

Just to make myself more clear in case people might have got the wrong impression from my earlier posts. I didn't mean what Ian doing is not a good idea... it will work very well, but its a lot of work. I would strongly suggest to any one that want to take on a bass trap DIY job to try out this route: http://www.radford.edu/~shelm/acoustics/bass-traps.html
It will work well as a wide band absorber, and no real need to sandwich.
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Online DRNB

Re: Bass trap build (at last!)
« Reply #25 on: January 18, 2011, 01:58:32 PM »
Appologies Ian, I don't want to take over the thread, but this is a must read to anyone that want to do this.  ;D

http://www.ethanwiner.com/acoustics.html
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline JimGore

Re: Bass trap build (at last!)
« Reply #26 on: January 18, 2011, 02:09:35 PM »
No problems!  We are all here to learn things - not just to look at pictures of builds.

Please feel free!

Cheers,
Ian.

Offline fdlsys

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Re: Bass trap build (at last!)
« Reply #27 on: January 18, 2011, 03:19:14 PM »
Just to make myself more clear in case people might have got the wrong impression from my earlier posts. I didn't mean what Ian doing is not a good idea... it will work very well, but its a lot of work. I would strongly suggest to any one that want to take on a bass trap DIY job to try out this route: http://www.radford.edu/~shelm/acoustics/bass-traps.html
It will work well as a wide band absorber, and no real need to sandwich.
My literary effort that you are referring to has been started way before yours was posted  ;D It just took a while to finish; I am at the office after all... No reference to anything you posted, really.

The intention was to steer everybody away from using mineral fibre, more than anything else.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when you’ve lived a little. Miles Davis

Offline faultysa

Re: Bass trap build (at last!)
« Reply #28 on: January 19, 2011, 12:14:42 AM »
Saw the effort going in here on the weekend, cant wait to see those rolls replaced.
Stereo is still best Boys!

Offline JimGore

Re: Bass trap build (at last!)
« Reply #29 on: January 19, 2011, 07:29:13 AM »
I removed one of the rolls last night to start cutting it up.  The lounge looks so strange and empty without that pink monster in the corner  ;D

Ian.