Roomfit strange tests

[Wiimer]

Hi,

I'm not very busy today and the temperature outside is over 39°C, so I decided to conduct the experiment inside the air-conditioned house

A slightly bizarre RoomFit test.

[Overview]
Perform a RoomFit on each of the two WiiM devices in two different rooms and compare the results of Room A measurements with the microphone in Room A.

In other words, find out if the WiiM in room B can compensate for room A. In my estimation, this is possible. Because RoomFit is running on the WiiM server.





[Test method]

1. First, run RoomFit in room A with WiiM A as usual. Room A has a tablet with IMM-6C connected.
2. Next, using the same tablet, run RoomFit on WiiM B. At this point, use the WiiM app on another phone to play a test tone from WiiM A.
3. Copy the RoomFit profile created on WiiM B to WiiM A.
4. Profiles 1 and 2 are evaluated with the WiiM Mini and the two results are compared.

I started working with my favourite earbuds, enjoying the music. The end result looked like this.


[Compare measurement results]
This photo shows the overlaid results of the WiiM A and WiiM B corrections.

1st time


2nd time


The response was slightly different for the 1st test, but for the 2nd it was almost identical. As I expected. The timing of the test tone playback was critical when measuring with the WiiM B. (I failed several times.)


Now I come to the main test .
In the next test, I will use RoomFit in WiiM B to perform MMM in room A.

Before I do that, I forgot to mention that I need to check that the RoomFit evaluation of the WiiM A matches the evaluation by the WiiM Mini.

This is the result of the WiiM A correction.


This is an evaluation by Mini.


Overlap these two sheets.

Almost identical, no problems.



[RoomFit Settings]
Band: 30Hz~4kHz
Gain/Q: MAX
Non-Boost Mode: on
Sub: on (Cross: 120Hz)
MMM: off
Smoothing: 1/12
MMM: on


For the WiiM B MMM measurement, I played my pink noise track file. I increased the volume by 10% during playback to see what would happen. The end result looked like this.

[Compare measurement results]


The results are almost identical, but with a larger dip at 150Hz~200Hz for WiiM B.


Now, incidentally, I also tested Multiple Measurements (MM).

With MM, the test sweep is played back three times, but sometimes it is only played back twice (or once) and unstable. This time I will compare the results when the test sweep is successfully played three times: with WiiM B, I was able to the test sweep is played four times. I will see if this makes a difference.

[Compare measurement results]

No major differences..



To be honest, I was hoping that something good would come from applying this method, but unfortunately it doesn't seem to help at the moment .

Today's experiment ended in a fiasco..

However, what I have learned once again is that the correction by RoomFit is uneven.

E.g., sometimes it shaved off the 150 Hz peak, sometimes it didn't.


I feel the results would be better if RoomFit could recognise the critical points and compensate for them preferentially. For now, I may need to take several measurements under the same conditions and choose the best one.


Suggestions and advice are welcome.
Thanks for reading to the end

 

[Machiavelli]

quite sure again a great job @Wiimer
it seems this stuff became some sub-hobby! the only issue? i do not understand

 

[Wiimer]

quite sure again a great job @Wiimer
it seems this stuff became some sub-hobby! the only issue? i do not understand

To be honest I don't quite understand it myself
Thank you.

 

[slartibartfast]

quite sure again a great job @Wiimer
it seems this stuff became some sub-hobby! the only issue? i do not understand

I'm glad you said that. I don't understand either

 

[Musician]

It’s important to know the differences between fundamental room resonanses ( wall/wall, floor/ceiling, wall/wall ) and reflections . Many misunderstand this.

The fundamental room resonances are mainly 3 of them - entirely dependent on the size of the room. They are all below 80 Hz in a normal European room with 2.4 meter floor/ceiling.

Reflections are always depending on where the speakers and listening positions are.
A measured reflection at listening position at 180 Hz will change frequency if you move to the side 30cm .
This is why room correction only work in a good way if you sit exactly at sweetspot .
Outside the sweetspot ( +-30 cm ) the sound will be worse than without corrections .

Multiple measurements at listening position are a compromise made to allow more than one people to listen, and is not as good sounding as it can be with only one single measurement at sweetspot.

 

[dominikz]

It’s important to know the differences between fundamental room resonanses ( wall/wall, floor/ceiling, wall/wall ) and reflections . Many misunderstand this.

The fundamental room resonances are mainly 3 of them - entirely dependent on the size of the room. They are all below 80 Hz in a normal European room with 2.4 meter floor/ceiling.

Reflections are always depending on were the speakers and listening positions are.
A measured reflection at listening position at 180 Hz will change frequency if you move to the side 30cm .
This is why room correction only work in a good way if you sit exactly at sweetspot .
Outside the sweetspot ( +-30 cm ) the sound will be worse than without corrections .

Multiple measurements at listening position is a compromise made to allow more than one people to listen, and is not as good sounding as it can be with only one single measurement at sweetspot.

While I agree with some of the points you raise, I feel some points need to be clarified further.

In the context of room correction, relevant acoustic effects can be (very) broadly categorized into:

• Room modes, which are fully described by room dimensions and shape
• Speaker (and Listener) Boundary Interference Responses (SBIR and LBIR), which depend on speaker and listener placement in the room
• Other reflections

Room modes
When you speak about "fundamental room resonances" you seem to only refer to the three 1st order axial room modes.
These are usually the strongest - that is true - but room modes can be axial (between two opposing surfaces), tangential (between two pairs of opposing surfaces) and oblique (between all 6 surfaces). All of these have higher order modes as well (2nd, 3rd, etc).
So there is a lot of room resonances / room modes in every room.

The various room modes will be distinct at very low frequencies, but they will progressively overlap as frequency increases and at some point modal behavior of the room will no longer be apparent from the response measurement. We call this point the "transition frequency" and it is usually assumed to be somewhere between 200-400Hz in a typical residential room.

Room modes are simply the characteristic of a room, and they are very difficult and expensive to treat physically. Fortunately, in-room response at very low frequencies for sound reproduction can be very effectively managed even without costly physical treatments, by using:

1. multiple subwoofers optimized with DSP (e.g MSO), and room correction, if we need an optimal response across multiple seats (see this document by T. Welti)
2. room correction only if we need an optimal response at a single seat

SBIR/LBIR
For some strange reason, most of the online resources on home acoustics for HiFi seem to mention room modes, but don't talk as much about SBIR or LBIR.
However, anyone doing any kind of serious research into home sound reproduction will quickly find that SBIR and LBIR have at least equivalent (and often even more) impact on the bass response in a room as do room modes.
Unlike room modes, SBIR/LBIR depend only on where you sit and place your speakers/subs in a room - specifically the distance from room boundaries (walls, ceiling, floor).

SBIR and LBIR will create a pattern of peaks and dips in the in-room steady-state response that will depend on these distances. I wrote more about this mechanism in this post.

Nulls (dips) caused by SBIR/LBIR are very audible ("bass suck-out") and can be difficult to fix by room correction. I always recommend to fix the cause by optimizing placement first (see previous link for more information) before attempting room correction. With careful placement nulls in the response can be avoided completely, or at least significantly reduced.
The peaks can be easily knocked down by EQ (room correction) - just note that the peaks caused by SBIR will be the same for all seats, while those caused by LBIR will not.

Other reflections
I'm using this as a collective name for everything which doesn't fall under room modes or SBIR/LBIR. These kinds of reflections can be either pleasing (e.g. early side-wall reflection causing sound-stage widening) or distracting (e.g. flutter echo).

These kinds of reflections unfortunately cannot be changed by EQ/room correction, so if we're displeased by how they affect the sound the only option we have is physical room treatment.

In summary
Room correction EQ is a very effective way to address resonances/peaks in the response below the room transition frequency, but is NOT the right tool to solve:

• nulls in the response (you need to optimize listener/speaker/sub placement and sub crossover for this)
• to optimize low bass response for a very wide listening area (you need multiple subs for this)
• to optimize upper bass response (>80Hz) for a very wide listening area (you need physical room treatment or something like Dirac ART for this)
• for acoustical issues higher up in the spectrum (you need physical room treatment for this)
• or to fix loudspeaker responses full-range (you need to EQ based on anechoic data for this, or just get better speakers )

 

[EddNog]

It’s important to know the differences between fundamental room resonanses ( wall/wall, floor/ceiling, wall/wall ) and reflections . Many misunderstand this.

The fundamental room resonances are mainly 3 of them - entirely dependent on the size of the room. They are all below 80 Hz in a normal European room with 2.4 meter floor/ceiling.

Reflections are always depending on where the speakers and listening positions are.
A measured reflection at listening position at 180 Hz will change frequency if you move to the side 30cm .
This is why room correction only work in a good way if you sit exactly at sweetspot .
Outside the sweetspot ( +-30 cm ) the sound will be worse than without corrections .

Multiple measurements at listening position are a compromise made to allow more than one people to listen, and is not as good sounding as it can be with only one single measurement at sweetspot.

This is why I now have two different, "profiles," in my system.

1: WiiM PEQ/correction disabled, DIRAC full correction up to 250Hz for when I'm doing critical listening at the sweet spot
2: One -4.5dB cut with Q=3.0 at 45Hz in the WiiM PEQ, DIRAC fully disabled for when I'm watching stuff from Apple TV as a family/group or when doing background listening (I play music while I work from home 3 days a week as my home office/desk is about 5 feet away from the MLP and closer to the corner where DIRAC overloads my corner desk with bass in a way that just the one PEQ cut in the WiiM does not). This tames the single room-gain, "bump," that appears on both channels for me and is the sole major issue I have under my room's Schroeder frequency.

-Ed