RoomFit help - Bass nulls just on left channel

[hipoagumol]

Hello,
Just purchased Dayton Audio iMM-6c usb-c calibrated mic to perform room correction.
I run with these settings and found deep nulls in the bass region response of my left channel (50 and 80 hz approx?)
- B&K
- 30-400hz
- -12/12 Gain, Q max 10
- No boost
- variable smoothing
- No multiple/moving mic measurements

My setup is wiim ultra-yamaha a-s501- Q Acoustics 3050i.
I tried without and with foam plugs in the bass reflex ports, reduxed bass energy but same nulls issue in the measured left channel response.
My room is quite symmetrical, parquet floor and plasterboard walls, so not a reflective room i would say except for cristal in doors you see in the picture..The windows you can't see on left side are shaded by Japanese panels. Picture is taken with wide angle, distance between speakers and to listen position is approx 2.5m
Any idea on what may be the reason? Is it truly so much different the left/right response or may have some flaw in my setup/hardware? Any advise?

 

[hipoagumol]

@dominikz i've read so many good posts you've written around Room Correction...may I ask for your advice?
Thanks. You can call out your choice of forum alfa team members too ...i am rather new here..thanks!

 

[dominikz]

My room is quite symmetrical, parquet floor and plasterboard walls, so not a reflective room i would say except for cristal in doors you see in the picture..The windows tou can't see on left side are shaded by Japanese panels. Picture is taken with wide angle, distance between speakers and to listen position is approx 2.5m
Any idea on what may be the reason? Is it truly so much different the left/right response or may have some flaw in my setup/hardware? Any advise?

The room is not entirely symmetrical though, on the left side there is a wall while on the right side a door opens into another room, as far as I see? That could very well be the reason, as it will affect SBIR.

A null at 50Hz corresponds to about 1.7m distance from woofer to some wall (or floor, or ceiling), and similarly the ~70Hz dip would correspond to about 1.2m distance. Does that match any boundaries in your room layout?

Do you have any flexibility in speaker placement? From the picture I'd guess no, right?

How does the response look if you use Stereo RoomFit instead of Individual Channel RoomFit?

 

[hipoagumol]

Thanks for the prompt response!
Stereo measurement has not such deep dips.?! Actually opposites, there's high bass bumps that RoomFit irons well. What does this mean? I don't just want to ignore the asymmetric room response, I assume L+R separate corrections is still the best way forward?
I am quite worried about so many ups and downs in the 100 to 500hz range.

I've never gotten such ripples when measuring with Samsung S22 mic. I used the Dayton with its calibration file etc..Wonder if doing something wrong.

Aside of the 50 and 70hz nulls on the left channel , on the right channel and stereo response there's also a deep dip around 125hz or so. I know boost does not work fine for cancelations...but should I try? Is it maybe other problem with my amp/speakers?

This is the room in panoramic, so you have a clearer view.
I can toe out the speakers that currently are slightly tied in towards listener..maybe separate from the tv furniture a bit more each but not really many options. The reflex ports are around 20-30m from wall.

Thanks!

 

[Wiimer]

Hello,
Just purchased Dayton Audio iMM-6c usb-c calibrated mic to perform room correction.
I run with these settings and found deep nulls in the bass region response of my left channel (50 and 80 hz approx?)
- B&K
- 30-400hz
- -12/12 Gain, Q max 10
- No boost
- variable smoothing
- No multiple/moving mic measurements
View attachment 35514
My setup is wiim ultra-yamaha a-s501- Q Acoustics 3050i.
I tried without and with foam plugs in the bass reflex ports, reduxed bass energy but same nulls issue in the measured left channel response.
My room is quite symmetrical, parquet floor and plasterboard walls, so not a reflective room i would say except for cristal in doors you see in the picture..The windows you can't see on left side are shaded by Japanese panels. Picture is taken with wide angle, distance between speakers and to listen position is approx 2.5m
Any idea on what may be the reason? Is it truly so much different the left/right response or may have some flaw in my setup/hardware? Any advise?
View attachment 35515

I believe the door on the left side is made of glass—does lowering the roller blind affect the measurement results at all?

 

[dominikz]

Stereo measurement has not such deep dips.?! Actually opposites, there's high bass bumps that RoomFit irons well. What does this mean? I don't just want to ignore the asymmetric room response, I assume L+R separate corrections is still the best way forward?

Ideally we'd like the individual L and R channel and stereo (L+R) responses after correction to all be smooth. Unfortunately, that is not always possible in the real word, with the various constraints we all have in our living environments.

Luckily, many recordings have mono bass anyway, so if the Stereo RoomFit variant works better, it should all still sound pretty good!

Still, the left channel response does look strange to me. Which brings us to...

I am quite worried about so many ups and downs in the 100 to 500hz range.

I've never gotten such ripples when measuring with Samsung S22 mic. I used the Dayton with its calibration file etc..Wonder if doing something wrong.

Do you have a screenshot of RoomFit responses when you measure with your S22 built-in mic? Do you get the same irregular left channel response in individual channel mode when you use the phone mic? Do you see the same if you enable MMM (moving mic measurement) to measure with pink noise? I wonder if that was just some transient error in measurement....

Note that some ripples in 100-500Hz range are unavoidable - but as long as they are narrow and not too severe they are probably audibly benign.

BTW, if you try to use MMM (moving mic measurement) you might see that these ripples decrease a bit, due to spatial averaging. Have a look at some of my responses in this comparison for an example.

Aside of the 50 and 70hz nulls on the left channel , on the right channel and stereo response there's also a deep dip around 125hz or so. I know boost does not work fine for cancelations...but should I try? Is it maybe other problem with my amp/speakers?

The reflex ports are around 20-30m from wall.

The 120-130Hz null is most likely caused by the distance of the speakers from the wall behind them - i.e. a front-wall SBIR notch.
You can try to push the speakers closer to the wall, so there is only 5cm gap behind them. That should move the null to ~200Hz, and possibly make it a bit shallower.
But while it is deep, it is a very narrow null, so probably not that audible in practice. Meaning you could also keep the current placement.

I can toe out the speakers that currently are slightly tied in towards listener..maybe separate from the tv furniture a bit more each but not really many options.

Toe in/out won't help with these specific issues, unfortunately. Let's see if any of the other suggestions help!

I believe the door on the left side is made of glass—does lowering the roller blind affect the measurement results at all?

Have to say that I doubt rollers would affect the response at 50-80Hz, but it doesn't hurt to try!
Opening/closing the windows and doors might change the response in that part of the range, however. See this post.

 

[hipoagumol]

Hi,
Thanks for all the comments. Have little time to test during weekends as kids are around. However here some findings:
- Samsung S22 per channel measurements also show the same nulls and very rippled 100-500hz range I didn't recall this when measuring in the past, but maybe it is because I measured stereo and used pro plus which I recently swapped by a second hand Ultra. Wonder if might be defective line out (rca) somehow?
S22 mic

- left side there is a cristal door yes, roller blinds were down when measuring with IMM-6C last evening. But up when measuring now with S22, so don't think they are the root cause of the deep nulls on left channel

Which android app do you recommend to evaluate room response, this time with pink noise maybe as you suggested?

I have to test this:
-measure somewhere else in the room. Those cancelations should not be seen everywhere right?
- swap right-left line output cables of my ultra and see if nulls are now measured on "right" channel room response or on "left" that would rule out or confirm a fault
- measure with speakers even closer to the wall, problem is that furniture will become a little wall on speakers side as furniture is deeper than speakers

Those -10-15dB sharp nulls are very strange don't you think?

 

[Wiimer]

Which android app do you recommend to evaluate room response,

The Spectroid app is well-known.

 

[hipoagumol]

Hi again,
@Wiimer I downloaded Spectroid, how do I ensure my iMM-6c is used? I only see these options in audio source:

When iMMc-6c connected to phone'a usb which one should I select?

Then I guess i need to play pink noise, reset "max hold" , click on play in the spectrum screen and leave it measuring some seconds until the red line doesn't change anymore.. then the red line would be the room response?

@dominikz Continued using RoomFit meanwhile:

-Tried rca cable swap and same response was now measured on the 'right' , which was actually left. So it is not ultra's output problem.
-Swapped speaker, same. So it is not a faulty speaker.
-Tried blinds down, up, speaker closer or further to wall, some thick cushion on nearest left side wall and cristal door and on wall behind my head..no noticeable changes! Dips around 52 , 70 and around 100 (double of first null), -15 -20dB deep!, are still there..

What next? Ignore and run stereo correction? Move around all the furniture and see if something changes?
Now that I know those nulls existe in my listening position i want to fixed them or at least mitigate!
I didn't know bass range of frequency may show such sharp and deep dips.

 

[Wiimer]

When iMMc-6c connected to phone'a usb which one should I select?

Select "Microphone" and touch the tip of the IMM-6C to see if the yellow line reacts significantly.

Then I guess i need to play pink noise, reset "max hold" , click on play in the spectrum screen and leave it measuring some seconds until the red line doesn't change anymore.. then the red line would be the room response?

Yas

 

[dominikz]

S22 mic

- left side there is a cristal door yes, roller blinds were down when measuring with IMM-6C last evening. But up when measuring now with S22, so don't think they are the root cause of the deep nulls on left channel

Yes, this looks in line with the measurement you got with iMM-6C. So an issue with the measurement itself is IMO unlikely.

@dominikz Continued using RoomFit meanwhile:

-Tried rca cable swap and same response was now measured on the 'right' , which was actually left. So it is not ultra's output problem.
-Swapped speaker, same. So it is not a faulty speaker.

I agree with your conclusions. It seems to be an acoustical issue, and given that it is only visible on the left channel that means it is related to the position of your left speaker.

What next? Ignore and run stereo correction? Move around all the furniture and see if something changes?

Can you measure exact distances from the center of woofer (on the front side of the speaker) to:
1) the adjoining side-wall,
2) wall behind the speaker,
3) ceiling
4) floor
And also provide H/W/D dimensions of your room?
Then we can plug those into this online SBIR calculator to figure out which ones are causing the issue. That might gives us clues what to do next.

Moving the furniture is unlikely to help, IMO.

Or you can just use the "stereo" RoomFit correction and accept that there's some asymmetry in the responses.

Now that I know those nulls existe in my listening position i want to fixed them or at least mitigate!
I didn't know bass range of frequency may show such sharp and deep dips.

If that’s any comfort, you're not the only one with these kinds of issues. They are very common in residential rooms.
It is why speaker/sub placement + room correction EQ is so crucial for good quality bass!

Which android app do you recommend to evaluate room response, this time with pink noise maybe as you suggested?

You can just enable moving microphone method (MMM) in RoomFit settings - that will then use pink noise instead of sweeps to measure the responses.

 

[hipoagumol]

Hi, tried the moving mic, yes, I noticed the pink noise ans I definitely heard different (lack of bass) the left channel when playing alone. Right speaker sounded fuller. The results, the same. Having boosted the frequency up to 50 then this sudden dip is clearly audible with the pink noise. Even I could hear some kind of periodical sound varying in intensity. Not pink at all. the right channel sounds totally different.

@dominikz I will take all those measurements you asked for and draw a floor plan best i can.
Btw, my speakers have 2 woofers and tweeter in between. Will measure all distances anyway.

Thanks

 

[hipoagumol]

Here it is...