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

vroad

New Member
Thread Starter
Joined
Sep 4, 2024
Messages
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: 14
  • REWMeasurements_2024_09_04_BT.zip
    6.7 MB · Views: 3,785
  • LFrontRawNoBT.png
    LFrontRawNoBT.png
    842.6 KB · Views: 13
  • LFrontRawBT.png
    LFrontRawBT.png
    842.9 KB · Views: 11
  • RFrontRawNoBT.png
    RFrontRawNoBT.png
    992.1 KB · Views: 38
  • RFrontRawBT.png
    RFrontRawBT.png
    952.3 KB · Views: 11
  • LFrontRaw_SPL.png
    LFrontRaw_SPL.png
    268.1 KB · Views: 9
  • RFrontRaw_SPL.png
    RFrontRaw_SPL.png
    265.7 KB · Views: 9
  • LFrontRawNoBT_Decay.png
    LFrontRawNoBT_Decay.png
    363.7 KB · Views: 9
  • LFrontRawBT_Decay.png
    LFrontRawBT_Decay.png
    364.5 KB · Views: 8
  • RFrontRawNoBT_Decay.png
    RFrontRawNoBT_Decay.png
    346.4 KB · Views: 7
  • RFrontRawBT_Decay.png
    RFrontRawBT_Decay.png
    342 KB · Views: 8
Last edited:

moedra

Member
Joined
Mar 1, 2021
Messages
139
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
Messages
9,696
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
Qobuz, TIDAL, Spotify, ROON
Front Speakers
GoldenEar Technology Triton One.R
Center Channel Speaker
GoldenEar Technology SuperCenter Reference
Surround Speakers
SVS Ultra Surround
Surround Back Speakers
SVS Ultra Bookshelf
Front Height Speakers
SVS Prime Elevation x4 (Top Front, Top Mid-Front)
Rear Height Speakers
SVS Prime Elevation x4 (Top Middle, Top Rear)
Subwoofers
dual SVS SB16s + dual PSA XS30s
Other Speakers
Behringer 1124p; Aura Bass Shaker Pros; SuperSub X
Screen
Seymour Screen Excellence, Enlightor NEO AT Screen
Video Display Device
JVC NX7
Other Equipment
LG Electronics 65-inch B6 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
Messages
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.
 
Top Bottom