Do These Graphs Look Incorrect

[Shannanigans]

Hello, I recently built 2' wide floor to ceiling super chunk bass traps from OC703 and installed them in all 4 corners of my mixing room.

I took REW measurements following Soundman2020's instructions (John Sayers Forum) both before and after the installation and did not see any improvement. I'm using Kali LP6 monitors, a umc1820 interface, and EMM-6 measurement mic.

Do the readings in the attachment look realistic (blue is before treatment, yellow is after)? I'm surprised there is not a distinct frequency that the signal rolls off to 0 dB at. Additionally, while my room isn't ideal (small with 7' 7" high ceiling), I would think the bass traps should have had a more noticeable effect.

I took measurements earlier in the day (unfortunately they didn't save), after I put the treatment up, that looked more like I would have expected: A hard roll off starting at 40Hz with a steep dip in the bass range. The dip's trough would increase in frequency as I moved the monitors closer to the front wall. However, when I went to redo them, I got results like you see in the attachment even though nothing in my room or audio equipment changed.

Thank you in advance for your input.

 

[Wayne A. Pflughaupt]

The purpose of bass traps is to reduce low frequency decay times, AKA “ringing.” That won’t necessarily show up with a frequency response chart. You should be looking at before and after waterfall graphs.

In addition, your speakers, being small, are mostly operating above the frequency range where bass traps would be effective.

Regards,
Wayne

 

[Shannanigans]

Hi Wayne, thanks for the response. Wouldn't the bass traps still reduce the magnitude of the reflections which would decrease how much they interfere with the original sound? Since the speakers are operating at higher frequencies, shouldn't I see a point where the speakers have a hard roll off and eventually hit zero?

 

[Wayne A. Pflughaupt]

Wouldn't the bass traps still reduce the magnitude of the reflections which would decrease how much they interfere with the original sound?

Yes, but that would only happen in the lower frequency range where the traps are effective. That type of thing isn’t always apparent in a frequency response graph, but may show on a waterfall graph or other acoustics measurements.

Since the speakers are operating at higher frequencies, shouldn't I see a point where the speakers have a hard roll off...

Yes, and you have that at about 200 Hz.

… and eventually hit zero?

No. What happens on the low end is that the signal drops into the room’s ambient noise floor. Yours appears to be really high. A common city noise floor can be in the 45-50dB range. Even a rural location or soundproofed recording studio can still have a noise floor of 25-30 dB.

Regards,
Wayne

 

[Toe in]

Your Kali speakers should go down to around 50hz. Is the measurement done properly? Do you actually hear any bass?

 

[Shannanigans]

Thank you for your explanation Wayne. That was helpful.

Toe, yes, I do hear the low end. 40 - 50 Hz was where I saw the hard roll off in the measurements I lost and cannot reproduce.