How to evaluate my DIY bass traps correctly with REW measurements?

vroad

New Member
Thread Starter
Joined
Sep 4, 2024
Posts
2
How can I tell from my measurements that did bass traps are making my system's sound better and not messing up at least?
For evaluating time domain performance of bass traps, which graphs should I read and how?
Also, is there good rule of thumb for determining how much should I absorb? I guess I can't do more in my current room, maybe in the future.

I've built and installed 4 DIY porus material bass traps in my living room in the beginning of this year.
Each panel sizes about W60cm x H72 cm x D10cm. For the porus material I've used cellrouse fiber insulation material which weighs about 90kg/m3. I stacked 2 panels in 2 corners.
I know that many people would say that fully stacking in 4 corners is the minimal recommended amount, I just tried my best to treat my room with available living room space and my limited DIY skills.

I re-measured bass traps to see if bass traps are still working as expected, and previous measurements were really showing the perforamnce of DIY bass traps.
I only measured in single position so that the conditions other than bass traps won't change.
This time there are not much changes in frequency response graphs, except for higher bass frequencies like 200-300Hz.

When I measured the traps in the beginning of this year, the SPL at 100Hz was below 50dB at worst positions because of the sharp dip.
Installing traps restored some lost SPLs, increasing the SPL at 100Hz to 55dB or so at any positions.

This time the SPL at 100Hz was 55dB with or without bass traps.

I've only looked at frequency response graphs because that seemed like the easiest one to interpret.
Later I've learned about other types of graphs that shows time domain performance of bass traps such as waterwall, though I was not sure how to interpret correctly.

With or without room correction systems like Dirac and Audyssey, my system still sounds good at least to my ears, I don't think I've heard something weird.

My living room's system is 2.1ch configuration.
For "raw" measurements I've only enabled front speakers and disabled the subwoofer.

I've also included a measurements with Dirac DLBC and subwoofer enabled.
I didn't re-callibrate as that will chnage conditions other than bass traps. (Callibrated with bass traps present)

Using Dirac and subwoofer alone lowered the depth of the dip at 100Hz by large margin.
If you have only single listening position and only want to be able to fix frequency response irregularities, Dirac and subwoofer might be enough?

Amp: Denon AVR-X3800H
Front: ELAC DBR62
Subwoofer: SVS 3000 Micro (Only enabled for measurements with Dirac)
 

Attachments

  • floor-plan.png
    floor-plan.png
    293.5 KB · Views: 23
  • REWMeasurements_2024_09_04_BT.zip
    6.7 MB · Views: 3,791
  • LFrontRawNoBT.png
    LFrontRawNoBT.png
    842.6 KB · Views: 22
  • LFrontRawBT.png
    LFrontRawBT.png
    842.9 KB · Views: 18
  • RFrontRawNoBT.png
    RFrontRawNoBT.png
    992.1 KB · Views: 46
  • RFrontRawBT.png
    RFrontRawBT.png
    952.3 KB · Views: 17
  • LFrontRaw_SPL.png
    LFrontRaw_SPL.png
    268.1 KB · Views: 15
  • RFrontRaw_SPL.png
    RFrontRaw_SPL.png
    265.7 KB · Views: 13
  • LFrontRawNoBT_Decay.png
    LFrontRawNoBT_Decay.png
    363.7 KB · Views: 13
  • LFrontRawBT_Decay.png
    LFrontRawBT_Decay.png
    364.5 KB · Views: 12
  • RFrontRawNoBT_Decay.png
    RFrontRawNoBT_Decay.png
    346.4 KB · Views: 11
  • RFrontRawBT_Decay.png
    RFrontRawBT_Decay.png
    342 KB · Views: 16
Last edited:

moedra

Member
Joined
Mar 1, 2021
Posts
140
It looks like your traps are mostly effective from 160Hz and up. They aren't doing much below that. Either they aren't thick enough, they aren't in the right places, or there isn't a large enough air gap behind them. Not sure what the case is. There is a large reflection in the ETC graph around 12.4 milliseconds in the right speaker response. That may be coming from a rear corner. There are other reflections at 4.2, 6.5, 7.9, and 8.8 milliseconds that you should look into treating. These probably don't have much to do with the bass. You should be looking at the ETC graph to locate reflections in the upper regions, and the step response to see what's happening in the lower frequencies. I can see where Dirac cleared up your inter-channel coherence, but the oscillation behind the peak is a lot stronger in all cases than the initial pulse. There is a lot of energy bouncing around the room there that the traps are not absorbing.
1726754905004.png

1726754999008.png

1726755118745.png

1726755211547.png
 

Todd Anderson

Editor / Senior Admin
Staff member
Joined
Jan 20, 2017
Posts
9,828
Location
Balt/Wash Metro
More  
Preamp, Processor or Receiver
StormAudio ISP.24 MK2
Main Amp
Emotiva XPA-5
Additional Amp
Emotiva XPA Gen3 2.8 multichannel amp
Other Amp
Denon X8500H
DAC
THX ONYX
Computer Audio
AudioEngine A2+
Universal / Blu-ray / CD Player
Kaleidescape TERRA, OPPO UDP-203, Panasonic UB9000
Streaming Equipment
iFi Audio Zen Blue
Streaming Subscriptions
Spotify
Front Speakers
GoldenEar Technology Triton One.R
Center Channel Speaker
GoldenEar Technology SuperCenter Reference
Surround Speakers
GoldenEar Invisa MPX
Surround Back Speakers
GoldenEar Invisa MPX
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
Quad Array SVS SB16s
Other Speakers
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Screen
Seymour Screen Excellence, Enlightor NEO AT Screen
Video Display Device
JVC NZ8
Other Equipment
Sony 65-inch A95L OLED, Sony 65-inch X900F, ZeroSurge 8R15W x 2, ZeroSurge 2R15W x 2
Inflicting much change in the lower registers of bass is really tough to do, unfortunately. What kind trap materials are you using?
 

vroad

New Member
Thread Starter
Joined
Sep 4, 2024
Posts
2
Inflicting much change in the lower registers of bass is really tough to do, unfortunately. What kind trap materials are you using?
I used cellrouse fiber insulation material made by a Japanese company named Ecopulton.
Because it seemed like the only material that is effective as glassfibre/rockfibre insulation and doesn't cause itchiness.
It looks like your traps are mostly effective from 160Hz and up. They aren't doing much below that. Either they aren't thick enough, they aren't in the right places, or there isn't a large enough air gap behind them. Not sure what the case is.
I guess one of the reasons that traps are not effective in lower frequencies is that I'm not spreading them as evenly as possible. I've only used 2 wall-to-wall corners in front of me. I straddled them in those corners to give some airgap.

Ethan Winer's article "Rigid Fiberglass Density Tests" showed that 12 panels 3 inches thick covering larger area is much effective than 6 panels 6 inches covering narrower area. I only have 4 panels 4 inches thick (10cm thick) now, and those doesn't have FRK facing. Each panel slightly larger than RealTraps panels but the number of panel is probably not sufficient.

To spread traps as evenly as possible I need to sacrifice room space or mount traps in ceiling to wall corner, etc.
Safely mounting 4kg weight trap to ceiling to wall corner don't sound very easy for me.
Also they make me feel the room even narrower. I'd rather avoid that as the room is not a dedicated listening room.
Looks difficult to treat more without moving to another house.
 

basscleaner

New Member
Joined
Nov 7, 2024
Posts
8
More  
Front Speakers
USHER SD-500
The first of all, you need to get noise response of your room, because there is suspecting, that power supply (or something else) in your room may causes distortion at this frequency. If not, then you need to choose the best position for stereo only, especially, if they work good in LF range. Word "good" means, that distortion in this range has to be in deviation corridor less, than +-2 dB. This value is due to our ear sensibility, because we can divide closest frequencies approximately 1.5 Hz between each other and +- 2 dB is the compromise (less is better!) to have not big difference between closest. After that you should mark peaks and dips and try to use bass traps consistently and carefully add them while controlling FR changes. It is important to remain yourself into the same seat positions due to measurements, because it influences to results. After you successed in the best stereo position by moving stereo base, seating point, you may to add sub with such a manner, that to regulate FR for deleting of remaining peaks or deeps by sub control features. If your narrow peak or dip still remains, you may to make your own tube resonator, which corresponds to this frequency and try to find zone, where it will work good. If you still want us to get comments, please, send your notes to every picture to understand what conditions were while measured.
 

Mike Schramm

Moderator
Staff member
Bright Side Crew
Joined
Sep 18, 2019
Posts
463
Location
Minooka, Illinois
More  
Preamp, Processor or Receiver
Onkyo TX-RZ840
Main Amp
Emotiva BasX A7
Universal / Blu-ray / CD Player
Panasonic DP-UB820
Streaming Equipment
Apple 4K
Streaming Subscriptions
Netflix, Hulu, Apple Music, Amazon Prime
Front Speakers
SVS Ultra Bookshelves
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Prime Satellites
Surround Back Speakers
SVS Prime Satellites
Front Height Speakers
SVS Prime Satellites
Rear Height Speakers
SVS Prime Satellites
Subwoofers
SVS PB-2000 Pro (x2)
Other Speakers
miniDSP 2x4 HD
Video Display Device
Sony XR-77A80J
Remote Control
Logitech Harmony One
I've always wondered: what is the go-to graph for evaluating room acoustics. I have treated areas of my room, but from a measurement standpoint I have no idea if they are actually doing anything to help.
 

basscleaner

New Member
Joined
Nov 7, 2024
Posts
8
More  
Front Speakers
USHER SD-500
I've always wondered: what is the go-to graph for evaluating room acoustics. I have treated areas of my room, but from a measurement standpoint I have no idea if they are actually doing anything to help.
There are two methods: to hear and to see. What is difference between them? The thing is that some of changes are difficult to sense briefly. Sometimes you need to have either very sensitive ears or big experience, because aged people have worse hearing, then young. That's why to use measurements may be more convenient, than to have the discussion with yourself. Changes in acoustical treatment become more clear, if to test some acoustical parameters, for instance, RT60 - reverberation time as dependence by frequency or any others. This can help to understand the dynamics of changes, how much to add or delete absorbing materials or use EQ, where to place it more efficient. It is well known fact, that our brain is capable to learn right listening.
 

Mike Schramm

Moderator
Staff member
Bright Side Crew
Joined
Sep 18, 2019
Posts
463
Location
Minooka, Illinois
More  
Preamp, Processor or Receiver
Onkyo TX-RZ840
Main Amp
Emotiva BasX A7
Universal / Blu-ray / CD Player
Panasonic DP-UB820
Streaming Equipment
Apple 4K
Streaming Subscriptions
Netflix, Hulu, Apple Music, Amazon Prime
Front Speakers
SVS Ultra Bookshelves
Center Channel Speaker
SVS Ultra Center
Surround Speakers
SVS Prime Satellites
Surround Back Speakers
SVS Prime Satellites
Front Height Speakers
SVS Prime Satellites
Rear Height Speakers
SVS Prime Satellites
Subwoofers
SVS PB-2000 Pro (x2)
Other Speakers
miniDSP 2x4 HD
Video Display Device
Sony XR-77A80J
Remote Control
Logitech Harmony One
So, RT60 is the graph I want to use, but the main way is to simply hear if there is difference?
 

ddude003

Senior AV Addict
Joined
Aug 13, 2017
Posts
1,593
Location
Somewhere Northeast of Kansas City Missouri
More  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
DAC
Chord Electronics Ltd. Qutest
Computer Audio
MacBook Pro, Custom i7 7700k De-lid 2xAsus1080ti GFX, Audirvana Studio, Hang Loose Convolver, Tone Projects Michelangelo, Pulsar Massive & 8200, LiquidSonics, SoX
Universal / Blu-ray / CD Player
Sony UBP-X700 /M Ultra HD 4K HDR & PS5
Streaming Equipment
Netgear Nighthawk S8000 Streaming Switch, Lumin U1 Mini Streamer Transport
Streaming Subscriptions
QoBuz Studio Premier, Amazon Prime & Netflix
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Screen
Elite Screens Aeon CLR3 0.8 Gain 103-inch
Video Display Device
Samsung The Premiere LSP7T UST Laser Projector
Remote Control
PrimaLuna, Lumin iApp, Samsung & Yamaha
Other Equipment
ThrowRug, SaddleBlankets, WideBand & Bass Traps...
I suggest more bass trapping, some wide band absorption and diffusion as first steps... Then the next step is DSP EQing...

Hint, Bass builds up in all 3 sided corners, floor and ceiling... And in all 2 sided areas, floor to wall and wall to ceiling... Also need to treat 1/4 to 1/3 of surface area... Yea, I know that's a lot... Here is a good source of information on this... http://arqen.com/bass-traps-101/placement-guide/ Also, get your hands on the Master Handbook of Acoustics by Ken C. Pohlmann... You might be able to find a previous edition on line as a pdf file for free...
 
Last edited:

basscleaner

New Member
Joined
Nov 7, 2024
Posts
8
More  
Front Speakers
USHER SD-500
So, RT60 is the graph I want to use, but the main way is to simply hear if there is difference?
No doubts, your ears sense is the Chief Justice anycase in accordance with your personal taste. In general, room acoustic treatment seems to mushroom picking in deep forest: you are looking for any mushroom, take it, and after some these acts you wonder to surprising changes. For mid and high ranges you may use the impulse response function to work with first reflections, flutter or any other kind of distortions, FFT for time domain search too. However there is some specific feature for low frequencies. The main requirement for this range - minimum FR distortion, so-called "Spread Curve", corresponding like a trend to your bass character you want to listen for music you prefer and having minimum deviations in limits +- 1.5 or less dB. Usual method for test it - yes, to hear consistently with the step 1.5 - 2.0 Hz along the frequency scale from 20 to 200 Hz (on practice 30 - 150 Hz, as a rule) and mark peaks and dips to further attempts to put away these disadvantages by appropriate methods.
 

basscleaner

New Member
Joined
Nov 7, 2024
Posts
8
More  
Front Speakers
USHER SD-500
It's necessary to add, that excessive amount of bass trap use is not good way for acoustical treatment at all. If you take away any mode from your FR by this device, it means, that you take away all subsequent modal frequencies too. Hence, you impoverish your FR, make sound dim and poor. For instance, if you delete 35 Hz peak, it means 70, 105, 140,...too. And if damping is in the wide band, for closest frequencies too. That's why the sound will be not bright you want. Good bye AC/DC !
 
Top Bottom