Help: Which Freq Response is "better"?

[rubicon99]

Im calibrating Genelec 8361s using GLM with 2 different physical arrangements. Trying to evaluate results in the GLM grade report.
Obviously best to listen to evaluate but since it takes me a while to change back and forth, its rather hard to do.

From a purely objective perspective, which of these graphs would y'all think gives better results? These are "post-correction" graphs.
One seems to have deeper but narrow notches, and the other shallower but wider.

GLM grade reports are also attached if anyone wants to dig deeper.

Your help is much appreciated.

Position #1:

Position #2:

 

[staticV3]

Scrolling through the reports side-by-side, I believe position #1 has more favorable decay characteristics.

Though if the calculated room size is correct, then some room treatment would be in order regardless of position:

 

[rubicon99]

Thanks. Room size isnt correct as its an oddly shaped room and i just entered numbers ignoring certain boundaries etc.
So u think the FR response is similar enough that decay characteristics are the determining factor?

 

[staticV3]

So u think the FR response is similar enough that decay characteristics are the determining factor?

Yes, they would be for me.

 

[RayDunzl]

From a purely objective perspective, which of these graphs would y'all think gives better results?

Can you show a measurement where both speakers are playing?

Sometimes that makes a difference.

Mine:

Left, Right and Both (black), at the sweet spot

 

[Keith_W]

Thanks. Room size isnt correct as its an oddly shaped room and i just entered numbers ignoring certain boundaries etc.
So u think the FR response is similar enough that decay characteristics are the determining factor?

1. It is the room volume that is important for that calculation, not the exact dimensions. If you have a non-rectangular room, add up the dimensions as if it were rectangular and then input that into the calculator.
2. Regardless, it is still an estimate because the other important factor in the calculation (the T30 and T20) are progressively less accurate at longer wavelengths.

 

[rubicon99]

Can you show a measurement where both speakers are playing?

Sometimes that makes a difference.

Mine:

Left, Right and Both (black), at the sweet spot

View attachment 446545

Both playing at the same time? No
GLM takes left and right measurements separately. And in the GLM report, they just overlay the L and R graphs on top of each other.

 

[Ropeburn]

Can you show a measurement where both speakers are playing?

Sometimes that makes a difference.

Mine:

Left, Right and Both (black), at the sweet spot

View attachment 446545

Whoa, that fat bass dip in what looks really good otherwise is BAD. Where does it come from? Some cancellation from floor bounce or something? I don't get it; the individual speaker curves suggest nothing remotely like that.

Most unfortunate cancellation ever. It's exactly where most of the bass energy is in properly made dance music. 40-50 is the "belly punch" that makes your feet move! Have you been able to address the problem meanwhile?

 

[Keith_W]

Whoa, that fat bass dip in what looks really good otherwise is BAD. Where does it come from? Some cancellation from floor bounce or something? I don't get it; the individual speaker curves suggest nothing remotely like that.

It's going to be because L/R are 180deg out of phase at that particular frequency band. Goodness knows why. OP needs more than a Genelec GRADE report, he needs REW measurements he can play around with and run simulations on.

EDIT: OOPS I just realised that it's RayDunzl's plot not the OP's. My sincere apologies!

 

[Ropeburn]

It's going to be because L/R are 180deg out of phase at that particular frequency band. Goodness knows why. OP needs more than a Genelec GRADE report, he needs REW measurements he can play around with and run simulations on.

Then the measurement must be flawed, because if you look closely, L and R are neither out of phase around those frequencies, nor do they differ anywhere close enough to produce such an hilariously large dip of 18dB or so. It must be something else, my best (uninformed) guess is it's some weird room interaction.

 

[staticV3]

if you look closely, L and R are neither out of phase around those frequencies, nor do they differ anywhere close enough to produce such an hilariously large dip of 18dB or so.

How can you judge phase from a frequency response graph?

 

[Salt]

It's going to be because L/R are 180deg out of phase at that particular frequency band. Goodness knows why.

That would be an explanation.

EDIT: OOPS I just realised that it's RayDunzl's plot not the OP's. My sincere apologies!

That does not mean there is no problem .
IIRC he's using planes planars, and those are pretty difficult to position in room due to omnidirectionality.
Though can't remember the model and if bass is conventionally housed.

Wait until he's hangared his Schweizer and he will reply...

 

[Ropeburn]

It's going to be because L/R are 180deg out of phase at that particular frequency band. Goodness knows why. OP needs more than a Genelec GRADE report, he needs REW measurements he can play around with and run simulations on.

EDIT: OOPS I just realised that it's RayDunzl's plot not the OP's. My sincere apologies!

Ah, I think that's what my mental mistake was. L and R are separate measurements taken independently from each other. So phase differences between them do not neccessarily show, unlike in the measurement of both of them playing together.

The severity of the deep bass dip is still astonishing. Neither L nor R have nearly as much amplitude difference to explain it easily.

 

[RayDunzl]

Whoa, that fat bass dip in what looks really good otherwise is BAD. Where does it come from?

That standing wave around 48hz is 180 degrees out of phase. I've verified this with the phase reported in REW.

Reason? I suppose because of my irregular room.

Here is an etching of the situation:

Green direct sound to couch
Red, some bounces off the distant walls to the couch.

The interesting part is I don't hear it, and didn't know it was there till measured.

Also, if the bass is stereo (and not duplicated mono) the dip disappears, as verified by RTA of various pieces with stereo and mono bass.

 

[RayDunzl]

Wait until he's hangared his Schweizer and he will reply...

If it goes in the hangar it's broke.

The rest of the time it remains tied outside with several others.

 

[alankila]

I'd go with measurement position 2 because the cancellations are less steep and there is slightly more low bass.