Bass ringing issues in an odd-shaped room and how I solved it

[ppataki]

I thought I would share this with the ASR Community since there might be folks out there with the same or similar issues

I have a pretty odd-shaped living room:

I have had various sound systems in it during the past 4 years and I have always had a huge issue with certain bass notes under certain circumstances.
For example when listening to tracks like this and this, the bass that should be coming from the left side I actually hear directly around my head, especially around my right ear....
It is a very annoying phenomenon that I have never heard in any other rooms; I guess it is due to that angled wall on the left-hand side reflecting bass sound waves in a funky fashion
(I am just speculating but could not come up with a better possible explanation)

During the years I have tried to solve it but could never come up with anything that would actually work - and since this is a living room I am very limited in terms of physical acoustic treatment

There was one thing that sort of worked but had downsides that shadowed the gains:
There is a VST plugin called GMonoBass that can 'monofy' the signal below a certain frequency that you can set. It did a great job, the ringing has stopped around my head but it introduced additional dips in the frequency range and it caused phase issues with movies (I have a 4.0 system and the whole 3D image of movies went out the window)
So I decided to no longer use it....

Then literally a few days ago I had an 'aha' moment while I was fiddling around with my CraveEQ plugin to boost the bass in my system
It can actually set any filter to behave in Mid/Side (M/S) mode instead of normal Stereo mode.

So what I tried is to set the boost filter (and only that) from Stereo to full Mid (with the system EQ-d to total flat in advance)

And wooow! The ringing around my ears is no more there, the impact is still there, I can still hear the bass from where it shall come from and the movies are not impacted either!

I am as happy as I can be - this simple thing just solved my issue I have been battling with for many years.....
If anybody has similar issues I would be curious to hear if this solution worked for you too

 

[neRok]

I've been reading over the various bass array threads, and one of your posts lead me to this thread...

Mid/Side technique isn't something I've heard of before, but after looking it up, it sounds like it takes stereo sound and puts the common sound in a mid channel, leaving the differences in the side channels. And then you've only EQ'd the Mid channel (the common sound). But with your music and its panned bass, if there is no sound around 35Hz say, and then a note is played in the left channel only at 35Hz, wouldn't that mean the note is played with no EQ applied? So how is this better?

Also, what is current speaker setup that has worked with this EQ? Just your 15" single driver speakers with full stereo bass, and no subwoofers?

 

[ppataki]

So how is this better?

It is not better or worse - it is just another EQ-ing method that actually fixed the acoustic issue that I have in my living room.
I would not recommend this method in a 'normal' shaped room but if the room has the same or similar weird bass ringing issue then it is definitely worth trying.

, if there is no sound around 35Hz say, and then a note is played in the left channel only at 35Hz, wouldn't that mean the note is played with no EQ applied?

I was afraid of this too. Technically you are right but actually in real-life situations I can hear bass coming from the sides as if they were EQ-d too
For example in this track the drums that are panned to the right have a visceral impact even with only boosting the Mid channel.

Also, what is current speaker setup that has worked with this EQ? Just your 15" single driver speakers with full stereo bass, and no subwoofers?

Correct, just the two 15" Fane drivers - I have no subwoofer and I have no intention to have any (been there, done that)

 

[ppataki]

I have found another great use-case for the M/S processing
One of my friends have optimized his system with Dirac Live 3.5 and this is the outcome

Orange is the corrected left channel, green is the corrected right channel and blue is the L+R measurement

There is a huge frequency dip between 45 and 80Hz caused by how the two speakers interact with each other in the room (my best guess only, if anybody has a better idea why please let me know)

As a result, all the bass (mainly kick-drums) that are panned to the middle sound lifeless and seriously lack energy
How I solved this for him is that one single PEQ bell boosting filter was applied at 55Hz on the Mid channel only
I know very well that it is not advised to boost dips but it just works (in this case at least) and he is super happy with the results - drums are now back to life!

 

[abdo123]

How I solved this for him is that one single PEQ bell boosting filter was applied at 55Hz on the Mid channel only

Couldn't you just do some FIR filtering to get the two speakers to play in-phase in that frequency?

 

[abdo123]

Or heck a good old fashioned all-pass filter

 

[ppataki]

Couldn't you just do some FIR filtering to get the two speakers to play in-phase in that frequency?

How would I do that? I would be grateful if you could please elaborate this

Or heck a good old fashioned all-pass filter

Applying an all-pass filter on both channels at 55Hz or how would I go about it?

Thank you

 

[ROOSKIE]

OP, out of curiosity why are you EQing the speaker flat in room?
Is this a personal preference for a trebble heavy tonality or is there something about your particular speakers and install that warranty such a tuning?

Ps. This is an interesting method for dealing with bass tuning by the way. I don't think my miniDSP supports this but I might try it in other software just to play with it.

 

[ppataki]

OP, out of curiosity why are you EQing the speaker flat in room?
Is this a personal preference for a trebble heavy tonality or is there something about your particular speakers and install that warranty such a tuning?

Ps. This is an interesting method for dealing with bass tuning by the way. I don't think my miniDSP supports this but I might try it in other software just to play with it.

This FR graph is not the final one, there are low and high shelves added to taste

 

[ernestcarl]

The allpass or FIR phase EQ abdo123 mentioned requires that you look at the phase response — alongside magnitude ideally. The alignment tool can be used for this purpose in REW.

 

[abdo123]

The allpass or FIR phase EQ abdo123 mentioned requires that you look at the phase response — alongside magnitude ideally. The alignment tool can be used for this purpose in REW.

Yes.

Generating a predicted response from REW's EQ tool and using the predicted response in the REW alignment tool to tune the Q and frequency of the all-pass accordingly.

it's tedious but an all-pass would add no delay or distortion and for a Q this size it should work pretty effictively.

in theory you need to EQ only one of the speakers to match the other.

 

[ppataki]

Thank you @abdo123 & @ernestcarl

I just 'blindly' played around with an all-pass filter on the right channel and got this result in the simulation (A+B)

The dip got way narrower, shallower and moved upwards - really cool!

I set the AP filter at 55Hz Q=3.5

I am not familiar with the alignment tool but if you think there can be better results achieved I would be happy to dive into it
Thank you

 

[abdo123]

the comment pushed me to look at my own summation and found major holes, one AP smooths it out but i haven't tested it out yet (listening wise)

 

[ppataki]

the comment pushed me to look at my own summation and found major holes, one AP smooths it out but i haven't tested it out yet (listening wise)

This looks really great!
How did you come up with that one AP filter?
I would love to understand if there is a better way than just trial and error

 

[abdo123]

This looks really great!
How did you come up with that one AP filter?
I would love to understand if there is a better way than just trial and error

I managed an even better result with two APs instead of one and higher Q values.

I guess that’s why people pay Dirac hundreds of dollars. Specially for the bass control.

Also makes me wanna get an AVR and a dedicated center even sooner.

 

[sarumbear]

I thought I would share this with the ASR Community since there might be folks out there with the same or similar issues

I have a pretty odd-shaped living room:

View attachment 262861
I have had various sound systems in it during the past 4 years and I have always had a huge issue with certain bass notes under certain circumstances.
For example when listening to tracks like this and this, the bass that should be coming from the left side I actually hear directly around my head, especially around my right ear....
It is a very annoying phenomenon that I have never heard in any other rooms; I guess it is due to that angled wall on the left-hand side reflecting bass sound waves in a funky fashion
(I am just speculating but could not come up with a better possible explanation)

During the years I have tried to solve it but could never come up with anything that would actually work - and since this is a living room I am very limited in terms of physical acoustic treatment

There was one thing that sort of worked but had downsides that shadowed the gains:
There is a VST plugin called GMonoBass that can 'monofy' the signal below a certain frequency that you can set. It did a great job, the ringing has stopped around my head but it introduced additional dips in the frequency range and it caused phase issues with movies (I have a 4.0 system and the whole 3D image of movies went out the window)
So I decided to no longer use it....

Then literally a few days ago I had an 'aha' moment while I was fiddling around with my CraveEQ plugin to boost the bass in my system
It can actually set any filter to behave in Mid/Side (M/S) mode instead of normal Stereo mode.

So what I tried is to set the boost filter (and only that) from Stereo to full Mid (with the system EQ-d to total flat in advance)

View attachment 262867

And wooow! The ringing around my ears is no more there, the impact is still there, I can still hear the bass from where it shall come from and the movies are not impacted either!

I am as happy as I can be - this simple thing just solved my issue I have been battling with for many years.....
If anybody has similar issues I would be curious to hear if this solution worked for you too

What do you mean by ringing? Ringing usually means this.

 

[ernestcarl]

I would only make sure it sounds “correct” or perceptibly better afterwards as this sort of phase manipulation can come off as “worse” to the ears.

 

[ppataki]

What do you mean by ringing? Ringing usually means this.

View attachment 277784

By ringing I mean the sound of decaying bass notes in the room (post ringing, for example after a kick-drum is hit)
As I explained above, my odd shaped living room produces really weird ringing phenomena that was resolved by the M/S EQ-ing method after years of trying many things

 

[fluid]

I would only make sure it sounds “correct” or perceptibly better afterwards as this sort of phase manipulation can come off as “worse” to the ears.

A very important point, manipulating phase while only looking at graphs is an all too easy way to destroy the sound.

For summation problems like that it is important to look at the cause, why do the two speakers cancel each other out? Looking at the SPL and Phase is one way, the spectrogram can also give a clue as often nulls develop in time. Sometimes it is better to attenuate the problem frequency range in one speaker and boost the other side a little to compensate so they don't fight each other as much. Placement can often solve these sort of things without any processing being needed.

Processing like Dirac needs to be the icing on the cake not a band aid for taming acoustic issues that are easily solvable with physical solutions.

 

[ppataki]

A very important point, manipulating phase while only looking at graphs is an all too easy way to destroy the sound.

For summation problems like that it is important to look at the cause, why do the two speakers cancel each other out? Looking at the SPL and Phase is one way, the spectrogram can also give a clue as often nulls develop in time. Sometimes it is better to attenuate the problem frequency range in one speaker and boost the other side a little to compensate so they don't fight each other as much. Placement can often solve these sort of things without any processing being needed.

Processing like Dirac needs to be the icing on the cake not a band aid for taming acoustic issues that are easily solvable with physical solutions.

Fully agreed, however physical solutions are not an option in my friend's living room hence the band aids