Final REW measurements, opinions?

[Davide]

Dear users,

I state that my system is the one in the signature.

I've recently been struggling a bit with Dirac Live due to some issues related to it. I discovered that when measuring at high sample rates the IR it detected was completely wrong, although it sounded satisfactory.
Taking measurements with REW I actually detected some anomalies, so I repeated everything at 44khz.
I also found that the asymmetry in the measurements causes a slight but perceptible difference towards the high frequencies, as Dirac compensates the gain based on these calculations. In fact, at large angles the correction should be limited in band, but since I needed to equalize I preferred to use the Dirac filter directly.

Anyway, I'm quite happy with the result. With the new measurement there is definitely more focus, so Dirac is doing his thing now.

There remain some aspects to improve, such as cancellations between 100 and 200hz, curious GD peaks and also a high GD in the subwoofers, but also high RT60 above 300hz.

Unfortunately I am limited in terms of speaker positioning, this is their definitive position, and in terms of treatment of the room I wouldn't know what to do without obtaining the dissent of my wife and son.
I am attaching a photo of the room (the subs are hidden in the TV cabinet and the door is a grid with a fine wood effect film applied).

I'm attaching some measurements.

Tell me yours!

Thank you

PS. I can't evaluate the IACC calculation... what do you think it is?

 

[Keith_W]

The IACC is a measure of how similar left and right speaker impulses are to each other. What you want is early IACC to be as high as possible (1 = exactly the same). Values above 0.85 are good, above 0.9 are very good. I don't know what values REW uses for "early" and "late" and I could not find it with a quick examination in REW's online manual.

Your early IACC is very poor. Everything from 125Hz up is less than 0.7 meaning that the sound from your left and right speakers are not identical. The obvious reason is how you have placed your speakers. DSP can help somewhat, but ultimately physical problems need physical solutions. If you are unable to find a way to place them better in your room, there is nothing DSP can do to help.

Disclaimer here: I am used to reading IACC in Acourate, which expresses it in % (i.e. > 90% is very good, etc). I am assuming that REW has normalized IACC to 1. If this assumption is wrong, throw everything I said above out the window.

The other obvious problem is that your T20 is very high ... between 600-700ms. You should target between 250-500ms. This means that an impulse will take about 0.6 to 0.7 seconds to decay by 20dB. Again, there is nothing DSP can do about this. You could fix it with more furniture, wall tapestries, thick curtains, room treatment, etc.

The step response looks OK, apart from the very long ringing. Again, not a DSP issue.

In summary:
- Dirac looks like it has done a decent job given what it had to work with.
- Speaker symmetry and placement needs rethinking.
- Excessive reverberation and ringing in the room. Needs work done.

Ultimately it may be better to ignore the measurements and decide whether you like what you hear or not. We humans are very good at adapting to listening rooms, even when the microphone says evil things.

Sorry. I realize this may not be what you want to hear. Good luck.

 

[AnalogSteph]

Looking at the last picture:

Holy mother of floor reflections. Somebody could really do with a nice thick carpet between the table and the TV cabinet. The bare tiled floor is certainly a major contributor to the high reverb times, I know that from my parents. The general lack of carpets and curtains is not helping matters.

Why is the TV cabinet squeezed into the corner that much? I would place it at least one row of tiles over to the right.

Is there a wall behind the sofa, and if so, what does it look like? Walls a short distance behind you tend to be a real trouble spot and generally need heavy treatment.

 

[Davide]

Thanks for the comments!

Why is the TV cabinet squeezed into the corner that much? I would place it at least one row of tiles over to the right.

Is there a wall behind the sofa, and if so, what does it look like? Walls a short distance behind you tend to be a real trouble spot and generally need heavy treatment.

I too would move the TV cabinet to the right but then it is no longer possible to open the dark brown cube on the wall...
That damn low wall that appears on the left seems made just to break the balls... but I am rented and cannot remove it.

Behind the sofa there is a wall with a 130x65cm painting and nothing else.
Not the best this too...

 

[DWPress]

How about putting the left speaker on "damn low wall" and moving the right out on a stand away from the wall? Get some absorption like a nice thick cozy carpet for starters.

As mentioned, Dirac has done its best with what you've presented to it.

 

[Davide]

How about putting the left speaker on "damn low wall" and moving the right out on a stand away from the wall? Get some absorption like a nice thick cozy carpet for starters.

As mentioned, Dirac has done its best with what you've presented to it.

It might be a good idea to improve some aspects, but I cannot place a speaker on a stand with my 3 year old son

And the carpet is definitely something I had thought of, but they are an honest dirt cage.