Why do my test tones have tremolo?

[D700]

While learning about room calibration, I began using long playing test tones (40hz->700hz) and discovered that certain frequencies have pronounced oscillation (tremolo?). Between 100 hz and 500 hz is more pronounced, with variability in frequency of the oscillation as well as loudness. The effect is present outside that range but not as pronounced.

Is this normal? Or should tones be playing with no pulsation?

My system is 2.1 with LS50s and a Velodyne MicroVee, using Wiim Room Correction. Trying to decide if I need bass management (Wiim Ultra) when I noticed this. My Marantz HD-AMP1 has subwoofer out but I don't think it has filtering. I've got the MicroVee rolling off @100hz

I started reading about comb filtering but got a little lost. If there are any reference videos or good threads explaining, I'd like to learn more.

Thanks!

 

[staticV3]

What you're hearing are room modes.

To alleviate these, you can:
-install room treatment
-apply room correction
-place multiple subwoofers in the room (even better with Multi Sub Optimizer)
-use Dirac ART or Trinnov Waveforming
-install a double bass array

 

[D700]

Would room correction apply on a continuous signal at a set frequency though? I thought it adjusted volumes at specific frequencies/ranges?

I was thinking part of it might be lack of sub low pass/speaker high pass filter setup, so speakers/sub were interfering with each other.

Here's pics of the room:

and I know jamming my LS50s against the wall of bookcase isn't ideal, I am using the port plugs and blanket behind. With room correction, I was able to get nearly ideal frequency response curve...but then started playing with test tones

 

[staticV3]

Would room correction apply on a continuous signal at a set frequency though? I thought it adjusted volumes at specific frequencies/ranges?

I was thinking part of it might be lack of sub low pass/speaker high pass filter setup, so speakers/sub were interfering with each other.

Here's pics of the room:

View attachment 405910View attachment 405911

and I know jamming my LS50s against the wall of bookcase isn't ideal, I am using the port plugs and blanket behind. With room correction, I was able to get nearly ideal frequency response curve...but then started playing with test tones

Ah, hm, I might've misunderstood your description of the issue.

Do you mean that even when playing constant test tones at a fixed frequency, there are oscillations in output amplitude and frequency?

That would be highly unusual.

 

[D700]

Yes, exactly. However, after comparing what I'm hearing from speakers to same test tones played through AirPods I think a lot of the osciallation/frequency of what I am hearing is just the natural tone of that particular frequency. But taking that oscillation out of equation (presuming if I hear it on earbuds, then its meant to be there) then when listening to speakers, what does change is the volume, which is louder near the speakers than my listening position (as expected)...but it gets really much louder at other end of room near the windows. Is that normal?

Especially when standing in the concave area formed by the bow windows...maybe those angled side windows are focusing the sound/amplifying to that area.

I installed the vertical blinds, thought would help absorb reflections...they are hard, textured vinyl s-curve cross section, wondering if I should have used fabric. Or maybe overthinking it.

Thanks

 

[Killingbeans]

but it gets really much louder at other end of room near the windows. Is that normal?

Yes, it's boundary reinforcement:

All About The Boundary Effect

Accurate monitoring is a must in the recording studio, but the perceived level of bass depends on where you are standing and where the speakers are positioned. Paul White explains why in audio, a boundary literally means a six.

www.soundonsound.com

 

[DVDdoug]

Nothing in the electronics or acoustics should cause tremolo or vibrato...

The only "odd" thing that sometimes happens is if for example, you have a 50Hz room-resonance it might be excited by a 49Hz tone, or something like that. You feed-in a "close" frequency and a different frequency is generated-resonated. But it wouldn't frequency wobble like vibrato.

 

[D700]

Yes, it's boundary reinforcement:

All About The Boundary Effect

Accurate monitoring is a must in the recording studio, but the perceived level of bass depends on where you are standing and where the speakers are positioned. Paul White explains why in audio, a boundary literally means a six.

www.soundonsound.com

gobsmacked! Textbook explanation of what's happening! Thank you!

At 100hz,
-I get 45 db 2' off bookcase between speakers
-65db if I slide over to in front of the sub.
-At listening position 7-8' from front wall, I get between 55-57db without much change as I move around
-At back, in the convex of the windows, I'm getting 70 db, which made the normal tone oscillation seem really loud.


As for the "wobbling" I'm hearing, I hear it with the same tone via AirPods as I do the speakers, which I presume takes the room out of the equation. So I expect that's just the normal oscillation for that frequency. I'm new to these test tones, so processing a lot of new info here.

Thanks for the assist.

 

[Sokel]

It's not tremolo,it's probably one form of consonance or assonance (depends who you talk to and you can also tune an instrument to it too) .
Try balance things by measuring them (meter,DMM and mic)