Quantcast
A lot of bass traping, poor results. - Gearspace.com
The No.1 Website for Pro Audio
A lot of bass traping, poor results.
Old 12th September 2012
  #1
Gear Nut
 
Golitan11's Avatar
 
🎧 5 years
A lot of bass traping, poor results.

I just made eight bass traps with Roxul Safe n' Sound (6'' thick, 2' large, from floor to ceiling (all corners) with a small gap behind (8'')) and after reading the graphs, I don't notice a big difference (with my ears too). Why?

Bass traps:

A lot of bass traping, poor results.-bass-trap.jpg

Waterfall (before):

A lot of bass traping, poor results.-waterfall-before-.jpg

Waterfall (after):

A lot of bass traping, poor results.-waterfall-after-.jpg

P.S. My room is 16'x14'x8'.
Old 12th September 2012
  #2
Lives for gear
 
Jens Eklund's Avatar
 
🎧 10 years
For a velocity based absorber to be effective at low frequencies; it needs to be very deep, and it also needs to cover a big part of the area related to the problematic modal/SBIR frequency.

Use this free tool to calculate the depth and flow resistivity needed (at specific angles of incidence since random incidence is not relevant in small room acoustics, especially not below Schroeder):

Porous Absorber Calculator


Also consider pressure based absorbers if space (depth) is limited. Another advantaged besides more efficient LF absorption for a given depth, is that they normally don’t absorb the mids and highs thus minimizing the risk of ending up with a room that suffers from too short decay times in the frequency range above the modal range (and too long below).



4m x 5m x 2.5m room - modal resonance problem

Before posting your measurement results
Old 12th September 2012
  #3
Gear Addict
 
🎧 10 years
2' large corner traps aren't very big, nor deep .. you're not the first one to be disappointed after the effort to build a bunch of traps.

Better invest into grabbing a good understanding of how modes and traps work, measure sound pressure in your room, and then build and place appropriate traps.
Old 12th September 2012
  #4
Lives for gear
 
kasmira's Avatar
 
🎧 10 years
A few reasons...

They weren't thick enough to deliver a LOT of impact at low frequencies.

You only have 4 corner traps installed - this really isn't much in comparison to the amounts usually suggested to get bass controlled by velocity based absorption.

You have two coinciding room modes - 8' and 16'.

Looking at similar absorbers, normally 2' wide traps are installed in the corners which leaves a large 12" max air gap which helps tremendously increase their performance. If you cut them so they fit more snug into the corner you significantly reduce the air gap. 8" is still a good air gap, yes, but 12" air gap is really a good bit more.

And a whole slew of other 'might be' problems - your walls might be resonating, those corners may not be the best places for traps, you might need traps to tame issues relating to height modes instead of L/W modes, etc etc.

There are reasons some of us get technical when answering questions. There is also a reason why we speak in large quantities. We typically speak in thicknesses of 6" as a pretty small impact bass absorber when mounted in corners. 4" is of the usual absolute minimum for getting some bass action. You have reduced peaks by 3-4dB, smoothed out some nulls, and dampened some resonances. I don't even see your graphs as unusual or as poor results. They look like what I would expect from 4 corners treated. Realize that your room has 928 square feet of surface area. Your absorbers have 64 square feet of coverage. That isn't even 7% of the surface area of the room. It is pretty minimal treatment for a room of that size.

Don't forget listening position, speaker position (including speaker height!), SBIR, high gain early reflections, as well as monitors not being decoupled from stands or desk, etc all play a factor on top of room modes, and can all be seen pretty low in the frequency spectrum for the most part.

Edit: They do look good though!
Old 12th September 2012
  #5
Lives for gear
 
🎧 5 years
Needs more surface area. Superchunks are just for the corner. They don't magically improve everything.

Looking at your graphs, they did improve response as one would expect them to. Peaks lowered and widened out, and some nulls came up. They are just fine. If you want more improvement, you will need more traps for more surface area.
Old 12th September 2012
  #6
Gear Nut
 
🎧 5 years
simply not enough. I have over 14 foot floor to ceiling 2 foot deep - thats a bass trap/ broadband absorber
Old 12th September 2012
  #7
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
You are getting some good answers above but just add about tuned traps. If you see the following thread I did do a experiment with broad band starting then adding something tuned after. If you have the mix in the right part of the room, the broad band is made right and place it right you should see a pretty nice improvement. To see improvement around the 40hz area though you do want to use tuned trapping (pressure based)
https://gearspace.com/board/7597560-post146.html
The way you are showing your tests are kind of hard to read. You should zip the REW file and post it here. The following video will explain how to do that.
Room EQ Wizard Tutorial Video
Old 12th September 2012
  #8
Gear Guru
 
1 Review written
🎧 15 years
Good

Reading test results seems to be a psychological exercise. Elsewhere we have seen poor results repeatedly and vehemently claimed as great success. Indeed we saw them pop up throughout threads as a sort of trojan advertising, shilling, for the particular V product involved. Here we see some graphs which show quite decent improvements, claimed as failure. Golitan, Zip and post the .mdat file so that we can illustrate the success. Also try a cut or boost of 3dB or so at say 100Hz, with a Q of 1 or so. Let's tie the audible to the pictures.

Sonically, the LF improvements are not simply audible. You need to focus on impulsive LF information, the speed of the Bass tones starting and stopping e.g. boggy's tone pulses, or say the drums in Jennifer Warren's 'Bird on a Wire.' For a more simply audible treat. Absorb the sides and overhead and you will be simply amazed at the improvement in stereo image.

Treatment of 20% of surface area is often quoted as a minimum to achieve ' a significant change'.

Good start.

DD
Old 12th September 2012
  #9
Gear Nut
 
Golitan11's Avatar
 
🎧 5 years
Here is the .mdat file:

Zippyshare.com
Old 12th September 2012 | Show parent
  #10
Lives for gear
 
seen-da-sizer's Avatar
 
🎧 10 years
Quote:
Originally Posted by DanDan ➑️
Reading test results seems to be a psychological exercise...
Agree, I do see a bit of improvement related to decay in the above charts. Making better waterfall charts will make it more obvious.

Still I trying to wrap around my head on this one.


------

Edit: OK, downloard the mdat file. Here is the overlay:

A lot of bass traping, poor results.-overlay.jpg
Clearly there is an improvement in the decay time, but not much more. However there is something strange with the area that has now more decay (120-300Hz). I would double check the entire test setup. Also make sure that recording level is as high as possible and the speakers are as loud as possible.

@OP: The LF is not very well represented in either chart. What speakers have been used?

Edit 2: Added before and after TOpt:
Attached Thumbnails
A lot of bass traping, poor results.-overlay.jpg   A lot of bass traping, poor results.-topt.jpg  
Old 13th September 2012
  #11
Gear Nut
 
Golitan11's Avatar
 
🎧 5 years
KRK Rokit 8 (low end monitors)
Old 13th September 2012
  #12
Gear Guru
 
1 Review written
🎧 15 years
Truth

Thank you SDS. Clearly a confusing picture. Mostly due to flutter echo between the side walls and the floor/ceiling I suspect. The longer decays in the lower mid regions could be a flaw in the testing. Or perhaps some weird interaction. Certainly I have found early treatment efforts, to reveal, make more obvious, or even make worse, other factors. That is why I have little interest, in general, in the before and after. Treatment is often, even usually, limited. I am entirely sure that SSC's work. However I always advise the bigger ones are better. Much better if you really have real LF issues. Furthermore, RFZ or as I prefer Zone Without Reflections, treatment is smaller, cheaper, and of immediately noticeable sonic benefit.
Four corners, floor to ceiling, ZWR. In the real world of real rooms, prosumer standard activity, it works.
In this case we do not have huge problems in the SSC effective region to begin with. This, plus the mysterious test anomaly. Golitan, I recommend you go ahead with Side and Overhead treatment. I fully expect to see that 1K stuff vanish. Further tests will probably not repeat the low mid stuff. If you do 100mm panels with 100mm airgap, (at least two panels per side and four overhead) I am confident that you will be delighted with the sonic improvement. As you can see, the graphs will never share or show such delights. Measurement is interesting. There is skill needed to tie it to reality. But Acoustic targeted acoustic treatment works. Every time.

DD
Old 13th September 2012
  #13
Gear Nut
 
Golitan11's Avatar
 
🎧 5 years
Thanks DD. I just made four panels to go on side and ceiling, I will fix them when I will have the time to. I will come back with the results.
Old 13th September 2012
  #14
Gear Guru
 
1 Review written
🎧 15 years
Half

Quote:
I just made four panels to go on side and ceiling
That's about half the minimum recommended.
So don't expect miracles. Here's a typical go-to treatment. But in this case Brendan made the larger 32 inch wide SuperChunks.
Little Dylan Studios
DD
Old 27th October 2012
  #15
Gear Nut
 
🎧 5 years
thickness

So how thick does a bass trap need to be? I am making a 13" deep by 24" width by 8 feet length, a rectangular shape placed diagonally in the corners. I am using Knauf fiberglass batting. Is thicker better?
Old 28th October 2012 | Show parent
  #16
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Quote:
Originally Posted by umarekawaru ➑️
So how thick does a bass trap need to be? I am making a 13" deep by 24" width by 8 feet length, a rectangular shape placed diagonally in the corners. I am using Knauf fiberglass batting. Is thicker better?
If you are straddling the corner that should do pretty darn well. You just have to put enough of them in.
πŸ“ Reply

Similar Threads

Thread / Thread Starter Replies / Views Last Post
replies: 396 views: 101901
Avatar for AndreiPiatra
AndreiPiatra 14th January 2020
replies: 51 views: 17165
Avatar for analogvinnie
analogvinnie 17th April 2013
replies: 928 views: 136243
Avatar for brianbotkiller
brianbotkiller 7th February 2015
replies: 18 views: 2964
Avatar for michael.kroeger
michael.kroeger 23rd November 2020
Topic:
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…

Forum Jump
Forum Jump