Room measurement, if someone could review and advise please.

[UpTheSwanny]

This is the Left speaker only.

This is the right speaker only.

I'm interested to know why the two graphs are different between the left and right channels. I have a rectangular room which if almost empty apart from desk chair and a small filing cabinet.

I'd be over the moon if anyone could let me know what this all means and if there is anything I can do to improve my listening experience further.

My monitors are Genelec 8030c.

Here is the right .mdat: https://www.dropbox.com/scl/fi/5u0q...ght.mdat?rlkey=c2rp03ig97lyy1zn4uwbf37qn&dl=0

And the left one: https://www.dropbox.com/scl/fi/3mdd...eft.mdat?rlkey=whs57tprshlr7egft3nfknnmm&dl=0

Thanks again.

 

[Purité Audio]

Have you tried the room ‘sim’ feature of REW, that will help with optimum placement.
Keith

 

[olieb]

I'm interested to know why the two graphs are different between the left and right channels.

The differences are not really that big. Considering that this is in the modal region of the room I guess these differences are to be expected even in a symmetrical, rectangular room. Small deviations from the symmetry can easily produce this. As Keith mentioned you can check with Room Sim option in REW.

 

[UpTheSwanny]

Hello, thanks for your replies. My room is only 10 feet by 6.5 feet and am limited where I can place things. But I feel everything is in the best place it can be. I have six acoustic panels which are 4 x 2 feet each at 4 inches thick. One in each corner and one on each side at the first reflection point. I've read that a cloud panel would be worth having? I've read too that damping the rear wall completely is worth while.

This is really a listening space so I only sit in one position. I was wondering if specific eq could be used?

It's such a complex thing.

 

[Purité Audio]

Have you entered your room’s dimensions/your seating/speaker positions into REWs ‘room sim’?
Keith

 

[flipflop]

I was wondering if specific eq could be used?

Yes, EQ is the only thing that can effectively address room modes.
You need to measure both speakers again at the same time, preferably using the MMM method. Instead of CSD, you have to use the regular in-room response with a 50 dB vertical scaling and Var smoothing to create the EQ filters. Don't go above the transition frequency.

 

[fineMen]

It's such a complex thing.

Don't worry. You expect symmetry but as you stated before, there is none: "... almost empty apart from ...". In the following you discuss acoustical treatment.

The static wave pattern is a complex matter indeed. Don't expect a cancellation of single reflections in bass with common treatment of only 4" thickness.

I once heard, but never tried myself, about the mirror symmetry of room acoustics, another one ;-) You might, if my recollection doesn't tick me, swap source and receiver. Means: place the speaker in your preferred listening position, and then seek out with the microphone at which point in the room the bass response is best. Then vice versa place the speaker there, and take the seat for yourself.

 

[olieb]

You might, if my recollection doesn't tick me, swap source and receiver.

Yeah, the wave equation is such a cool thing.
But the OP uses stereo full range (Genelec 8030), so there are two source positions and they cannot be chosen freely.There it gets more complicated again.

The interesting thing here is that the lower bass region (50-100 Hz) where typically single modes dominate and ruin the FR looks very good and balanced, whereas in the transition region (100-200 Hz) obviously the modes are somewhat lumped (around 140 Hz and around 180 Hz). The right speaker position seems to couple more strongly to the modes around 180 Hz for some reason.

 

[fineMen]

Yeah, the wave equation is such a cool thing.

You confirm my vague recollection? I think I can prove it, but ...

... two source positions ...

That was implicated; first choose an acceptable position for one speaker, then try to add the second one under more restrictions due to stereo symmetry. Maybe to move the microphone isn't as cumbersome as moving the delicate and heavy speakers.

With 'to add' I mean that the two could help each other out. A dip in one could be compensated by the other's peak. Finally, accepting a little deviation rom 'perfect' helps with many problems in life.

 

[olieb]

You confirm my vague recollection? I think I can prove it, but ...

That should be the symmetry versus time inversion of the wave equation.

A dip in one could be compensated by the other's peak.

I agree, in bass that should be ok. But the OP was investigating the L-R-asymmetry in the first place.
And in most rooms there are not so many stereo speaker positions to choose from. If the stereo triangle could be moved as a whole a little bit on the other side ...

The biggest problems seem to be in 100-200 Hz, I am not so sure "helping each other out" is working very well here. Even less as the peak around 140 Hz and the dip at 120 Hz are in both measurements.

 

[fineMen]

The biggest problems seem to be in 100-200 Hz, I am not so sure "helping each other out" is working very well here. Even less as the peak around 140 Hz and the dip at 120 Hz are in both measurements.

Well put. With the 'helping' I was after starting anew and then see.

So, to the bad of it, the relevant ondulations are quite symmetric? Maybe the o/p was after maximizing the symmetry for best stereo effect, but here it seems to backfire.

Sidenote: now that I personally arrived at a quite good stereo system that has it all for me, I'm not (!) that pedantic anymore. I'm 'over the top' as you will looking forward to actually taking the opportunities for their initial use, just music, speach, soundscapes ... . Not worrying anymore.

What could he do? Symmetry in the reflections, imho, isn't a good thing to begin with. Maybe there is a possibility to not place the speakers at a common wall, but around an edge of the room (do you say that?). Not the least, the stereo image is a quite fragile thing. Is it really worth to sacrifice comfort, visual appeal and usability of a room for perfecting it? O/k, once in a lifetime, sure, just for the experience. But on a daily basis, I doubt that.

In short: break the symmetry.

 

[olieb]

What could he do? Symmetry in the reflections, imho, isn't a good thing to begin with.

Why not? I imagine a situation where upper mid reflections arrive mainly from the left and lower mid from the right are not such a great experience.

To improve upper bass in the measured room one could
- try to have stronger absorption in general - so modes are broader and FR becomes flatter
- absorb selectively in the range around 140 Hz (Helmholtz-absorbers in the corners? / membrane absorbers?)
- try to diffuse the modes at 140 Hz (2,5m wavelength) thereby moving the modes to other frequencies. But you need rather big "diffusers" for that
- find a positioning where the speakers couple less to the room modes around 140 Hz. But the problems might just move somewhere else

The last option will probably not help with the broad dip around 120 Hz unless there are room modes at this frequency that are not excited with the measured positions.

Just my 2ct.

 

[fineMen]

Why not? I imagine a situation where upper mid reflections ...

I was under the same impression for a long time. Now I doubt it. Strong direct reflections will interfere with the direct sound, maybe even within the 'precedence' window, weakening the, whatever that is, stereo image. They could contribute to localizing the speakers individually (speculation).

Muting them would weaken the late overall reverberation, desirable or not. But is it at all possible to a sufficient degree? If sufficient, why then symmetry? In every case, if really smmetrical, all adverse effects are doubled, because they occur in identical frequency ranges on both sides at the single pair of ears.

If they were broken down to a more diffuse pattern, then there is no need for symmetry anymore by definition. Or is there a symmetrical diffuse? Symmetry is order, diffuse is (meant to be) the opposite of order.

The detrimental effect is easily seen in bass like here. Speaker A won't be able to compensate speaker B's ondulations, because A and B undergo the same.

Hope this helps. And again, perfection isn't the goal. Humble satisfaction and subsequent relaxation is.

 

[UpTheSwanny]

Thanks everyone. Really appreciate your help.

 

[olieb]

Or is there a symmetrical diffuse? Symmetry is order, diffuse is (meant to be) the opposite of order.

Hmm. I would definitely say that diffuse is a form of symmetry. Symmetry means that even if you change something (left versus right, position, rotation and so on, or time direction like in the wave equation) the outcome is the same as before (nothing changes). Diffuse sound is exactly like that.
Order is regularity and for this you actually have to „break symmetry“ first. The resulting regularity can still have symmetrical properties. But structureless goo is more symmetrical than a crystal.

 

[fineMen]

Hmm. I would definitely say that diffuse is a form of symmetry. Symmetry means that even if you change something (left versus right, position, rotation and so on, or time direction like in the wave equation) the outcome is the same as before (nothing changes). Diffuse sound is exactly like that.
Order is regularity and for this you actually have to „break symmetry“ first. The resulting regularity can still have symmetrical properties. But structureless goo is more symmetrical than a crystal.

My significant other would happily connect to your point of view ;-) Thermodynamics ... problem is, that what an audiophile associates with the significant effort to pay for diffusors is not quite diffuse. All the results, as far as I know, are limited. Improvement, yes, solution , no.

On one hand Dr. Toole says that people adopt to a room easily. Relaxed requirements in this regard. But he also shows some preferrence for more indirect sound, which isn't everybody's cup of tea.

Couldn't we conclude on giving a more asymmetrical set-up a try for bass equalization? Perhaps, as already at hand, using room treatment as an aftermath coping with asymmetry issues in the lower mids and up?

 

[olieb]

the significant effort to pay for diffusors is not quite diffuse.

Haha, right. But a diffusor could be a book shelf, too.

On one hand Dr. Toole says that people adopt to a room easily. Relaxed requirements in this regard. But he also shows some preferrence for more indirect sound, which isn't everybody's cup of tea.

There seems to be some kind of contradiction here. The adaption to a room certainly has its limits. I heard the Kii once in a demonstration in a very bad room with naked brick walls and windows all over, so directed reflexions galore. It took an hour and the sound was still as awful at the end as in the beginning.
Diffusion (indirect sound) is one way to increase symmetry and "relax requirements".

Couldn't we conclude on giving a more asymmetrical set-up a try for bass equalization?

Sure, in bass range the concept of reflexion does not really apply anyways. In the frequency region considered here human hearing (in rooms) is not very directive and the sound is produced in the form of room modes (mainly global in nature).
But it has to be checked whether an asymmetrical set-up improves the result. The coupling to room modes may change, but if there are no modes around 120 Hz that will not help. And it might improve the 160Hz peak or on the other hand worsen the smooth FR in lower bass. One has to check. Or simulate with REW.

using room treatment as an aftermath

That is a more general point. To see the room and its treatment as an afterthought is quite usual. I would not want to do that. What we actually hear in the first place is the sound pressure in room and the reflexion, diffusion and absorption of the room is crucial in this respect. In bass I would consider the room even more important, there I would consider the room actually part of the transducer/speaker.

 

[poxymoron]

I'd swap speakers left to right and right to left and then remeasure to see how much the speakers deviate from each other.

 

[fineMen]

Haha, right. But ...

I appreciate the discussion, and you've got one point or the other. I'm going to leave room to others now, though. Let's see what comes out within the next week or so? It's an all too general complex matter, but not desperate.

As I always do: Sly and the Familiy Stone " Runnin' Away (Single Version)" calculatedly low fi for max aha effect with the implicated message, great art in my book

 

[UpTheSwanny]

Hi my apologies, I've re measured. I realised I had the wrong calibration file for the mic. UMIK1.

Here are the new images;

Here is the left speaker

Here is the right

Here is right and left together.

I hope some will come back and see the new images and make comment if appropriate.

here are the mdat file links.

Left: https://www.dropbox.com/scl/fi/8g6z...923.mdat?rlkey=m5dxtyf56ei5a26ff5ilde0ij&dl=0

Right: https://www.dropbox.com/scl/fi/37ti...923.mdat?rlkey=h7kb3ljiisc2d5bdgtkqnn656&dl=0

r and l: https://www.dropbox.com/scl/fi/wipq...923.mdat?rlkey=kl34skz2hzizz32zzjmjiqp4e&dl=0

Many thanks.