I've done this on the front wall. About 10 bags, plastic still on, especially around the edges with some spacing from the wall, more on the open top half of the wall/ceiling, opened a couple for use directly around the speakers, added three individually tuned subs to complement the main woofers. Saved modifying the walls themselves and calmed the bass nicely.
while simply putting the bags of rockwool will work, its better to let the rockwool expend and build proper corner bass traps as the rockwwol is compressed in the bags hence reducing their efficiency.
"I thoroughly tested the two approaches and can confirm that compressed Roxul *DOES NOT* perform nearly as well as uncompressed Roxul. Too bad treating a room isn't as easy as throwing a few sealed bags of insulation in the corners. "
I also wanted to use that method but have been told that it wouldnt work as well.
https://www.gearslutz.com/board/bas.../494866-roxul-just-leave-bag-drop-corner.html
Right, air is the best damper and IIRC there was a pattern one cut in the bag to allow it to 'breathe' enough to get much of the benefit of no bag, but still be able to handle/stack it.
Unfortunately, this is all I remember and so long ago before the WWW......... hopefully someone posted it, but in a quick search couldn't find the magazine article.
GM
Unfortunately, this is all I remember and so long ago before the WWW......... hopefully someone posted it, but in a quick search couldn't find the magazine article.
GM
Some previous posts are saying stuff that seems in error, to my poor understanding.
Whatever your personal intuition, a light plastic bag should be pretty much transparent to low notes and a cut or two providing minimal advantage.
The Sabine value of an absorber like fibreglass would be a combination of location, thickness, and density. So, not clear if the unpacked insulation is spaced-out and somewhat more away-from the wall and so not exactly comparable to the in-the-bag results, except for cost, of course.
The sound in a room takes a few trips around before all has hit your ears (which is why you can reduce street traffic noise by putting absorbing stuff under your couch).
As I posted earlier, still an open question to settle how much music is like steady tones and how much like pulses. But it would matter a lot in terms of your sound quality vis a vis room treatment measurements.
Ben
Whatever your personal intuition, a light plastic bag should be pretty much transparent to low notes and a cut or two providing minimal advantage.
The Sabine value of an absorber like fibreglass would be a combination of location, thickness, and density. So, not clear if the unpacked insulation is spaced-out and somewhat more away-from the wall and so not exactly comparable to the in-the-bag results, except for cost, of course.
The sound in a room takes a few trips around before all has hit your ears (which is why you can reduce street traffic noise by putting absorbing stuff under your couch).
As I posted earlier, still an open question to settle how much music is like steady tones and how much like pulses. But it would matter a lot in terms of your sound quality vis a vis room treatment measurements.
Ben
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rockwool are compressed in the bag, therefore not as efficient then uncompressed.
bass traps are more efficient in corners and a air gap also adds efficiency to the bass traps. where two walls meet, theres a corner. you have 12 corner in a room.
You are a careful person to use "efficient" which recognizes the complexity here.
I've glanced at Sabine tables, but can't recall seeing values for stuff compressed in the bag, let alone spaced from the wall, etc. I suspect it's pretty good for low notes even fairly compressed. So I'm guessing.
My favourite material for several reasons is Tectum - looks like boards of calcified shredded wheat and easy to use as a replacement for drywall sheets. One of the few materials with good low frequency action, esp. spaced from wall. 35 years ago, I did my large, beamed-ceiling room LEDE with it.... just wonderful sound.
Ben
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https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/396026-tectum-finale.html
tectum, rockwool will all do the same job if you use enough material.
Interesting about your LEDE room. care to share pictures?
uncompressed rockwool will work better then compressed rockwool. just by understanding the way rockwool absorb the bass, its obvious that uncompressed rockwool will perform better, right?
Sure, use enough Kleenex and you have a great absorber, esp. uncompressed.
Tectum (a rigid board, not expensive, looks good (to me), just a few inches thick) can be a whole lot easier to accommodate than unwholesome foam-stuff. I recall that it has a remarkably smooth coeficient across the frequency compass too; an important virtue. Smart architects use it now and then - just keep an eye out for a wall or ceiling made of shredded wheat.
Yeah, wish I still had that beautiful beamed ceiling music room. Some folks from the Toronto audio club might remember it... and my high-voltage direct-drive-amp Dayton-Wright electrostatics. Here's a look during renovations. The doorway between the Klipschhorn bass and the ESLs became a sealed enclosure for 9 drivers. That's a genuine 1955 AR-1w (I am using it now, no kidding).
Ben
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Depends on a lot of factors. If you are doing serious construction, it costs only a bit more than the drywall it is substituting for and might need no finishing, unlike drywall. And that's it.
Ben
Ten Million dollar anechoic chamber
https://uwaterloo.ca/news/news/next-generation-wireless-communications-facility-opens
https://uwaterloo.ca/news/news/next-generation-wireless-communications-facility-opens
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No radio-wave echoes! Instructive to consider that those radio wavelengths can be just fractions of an inch as compared to 50+ feet for sub-sonics. Not sure why you'd need any chamber, except to keep out of the Canadian winter weather. Maybe real function is as an isolation chamber, a very different issue.
Even mighty Harman Corp's anechoic chamber didn't/doesn't go very low and needed math tricks to estimate low frequency performance, if I read Toole correctly.
Few truly big-scale anechoic chambers like the biggie at Bell Labs in Murray Hill, NJ, where I fiddled with motional feedback 45 yrs ago. I'm not sure how low that went. Anybody? Or the EMI building??
Do you need to vacuum-clean an anechoic chamber every decade?
Ben
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if you were to build the walls, why not use a couple of feet of fluffy rockwool which will work 10 times better.
I use that method in my theater. The front Sub is 4x15 IB with the manifold in-room. The rear sub is a 16 cuft sealed sub with a 18" Dayton Ultimax powered by a Crown XLS2500 (bridged).
There was significant improvement in the smoothness throughout the space, and FR at the MLP improved. With just the IB, there was a big null at 20 and 76Hz, now smooth at 20 and much improved at both points now.
Here is the waterfall plot, measured at the MLP, it reflects my house curve EQ, which is why the <80Hz rises.
Room was ideally sized, and then extensively treated. Subjective bass is very smooth and clear. And that IB goes deep, shakes the whole structure, the door will occasionally pop open due to pressure and vibration releasing the latch!
But more importantly, music is crystal clear even at high SPL.
I do plan to add another 16cuFt sealed (identical to the rear unit) at roughly the mid-point sidewall location, almost parallel to the MLP. as a way of further smoothing some of the resonances at 27 and 41Hz.
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I've just read the whole thread, if you don't want to do that, start at post #104
This is very interesting stuff. I want to ask whether this method also means the room is not pressurised? It seems to
Do you think there are any downsides to doing this with a stereo system opposed to home theater?
Can expand on what you mean by "room is not pressurized"?
Welti's method basically uses the second sub on the back wall to "destruct" the room modes since it is playing out of phase. I have seen measurements from one other system that does this (along with many RPG Modex plates) and the response is incredibly flat and the user says bass response is very even throughout the room.
Full paper is here: https://audioroundtable.com/misc/Welti_Multisub.pdf
Two sealed subs, one phase reversed is a dipole and so theoretically won't pressurise the room. This link explains it DP_woofer_room