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measuring correctly and interpreting the results (some questions...)

slacki

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hi, i removed my old bass traps and did some measurements. now i am nearly finished with my furniture (whats missing is my carpet thats still in cleaning). So i thought i'll do first measurements to see how the 20-250hz range does. So i took my laptop, connected it via hdmi to my Marantz Cinema 50, disabled all Audyssey in it, switched it to multi channel stereo and started the measurement. I hope that configuration is correct. I wanted to see how the frequencies look like when all speakers work. I used var smoothing.

spl.jpg

tbh this does not look that bad to me.
Unfortunately, i dont know how to interpret RT60, so maybe someone can say something about that:
rt60.jpg

and here the rt60 decay which also looks absolute ok to me:
waterfall.jpg

This is with nearly no room threatment (except my old 4 caruso isobonds for early reflections)

Am i missing something? Any feedback is welcome, any hint for improving the room acustics is welcome :)
 

ernestcarl

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I would say you are likely to hear more “room sound” given the RT. But I’ve seen worse around the 1s mark…

Probably 0.2 - 0.35 is more desirable for a dedicated listening space in small domestic room.

The dip in the low bass is both deep and broad which is going to be quite audible as a deficiency — more obvious with certain types of music.

There doesn’t seem to be too much prolonged ringing in the bass below 100Hz which is good — besides the lone peak around +20 Hz.
 

amirm

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Unfortunately, i dont know how to interpret RT60, so maybe someone can say something about that:
Follow the Topt line (green?) and see where it lands at 500 Hz. That value should be between 0.2 to 0.5 seconds which yours is (opt for larger for stereo music, lower for multichannel).
 

amirm

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I wanted to see how the frequencies look like when all speakers work. I used var smoothing.
You have 30 dB variation which is huge. You definitely need to EQ.
 

Elitzur–Vaidman

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It looks like your sub is set like 10db too low. I'd crank it up and eq down the peaks.
 
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slacki

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It looks like your sub is set like 10db too low. I'd crank it up and eq down the peaks.
This is for planning room acoustics on hardware-side, e.g. absorbers, diffusors, etc. - so just raising the sub and then EQing it is not exactly what i want in the first place, but of course this will be used in the end.
Its like: I want to prepare the room for Audyssey.
The dip in the low bass is both deep and broad which is going to be quite audible as a deficiency
you mean from ~22 up to ~72? So i need to find a better spot for my subs, yay... :(
Right now i have 2 in the back corner behind the curtains and a bigger one in the front. Unfortunately i have to protect them somehow from my cat, thats why i have this towel in the front and the ones in the back behind the curtain.

IMG_20230129_095902.jpg

IMG_20230129_095919.jpg


There will be a 3x3m carpet in 2 weeks between the TV and me, i guess that does not influence those low frequencies.
How can i improve that dip? Moving the subs or buying diffusors? Any golden rule for the subs? I want audyssey to have as less work to do as possible to have a good sound.
Just remembering i also have a MiniDSP, would it make sense to use only 1 sub-out of the marantz and instead use the MiniDSP for the lowest frequencies?

Thanks for your help, i really appreciate that!
 
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slacki

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i tried to build that room in REW room simulator and it looks close to my measurement. But no matter where i move the subs to, the signal gets worse. Unfortunately i dont know how to export only the room simulator, so another one could test it.

Bildschirmfoto_2023-01-29_12-36-30.png


distance.png


The both subs (2 and 3) have a PEQ onboard, should i use that to boost the bass a bit between 25-40hz and 50-60hz?
 
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HarmonicTHD

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i tried to build that room in REW room simulator and it looks close to my measurement. But no matter where i move the subs to, the signal gets worse. Unfortunately i dont know how to export only the room simulator, so another one could test it.

View attachment 260837

View attachment 260838
If you look at your first graph.
1674993026213.jpeg

Your sub is about 15dB too low vs the REW sim above. So crank it up and EQ out the peaks that will already smoothen things (aim for about an 75 to 80dB overall level).

Which dip do you mean exactly? The one around 50Hz? Here you can play a bit with the xover and the sub positioning if possible (REW simulator gives first hints, which positions to check). But there is no free lunch. With one sub there will always be some dips the trick is to find the best compromise given your room etc.

A carpet won’t change anything in that sub 200Hz frequency range (too thin vs the wavelengths).
 

Elitzur–Vaidman

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What's your crossover point? Knowing that will help us figure out what's going on.
 
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slacki

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I use 80hz as crossover, yes

I have 3 subs, so only saying "raise your sub" is a bit problematic, as i dont know which one ;)
I used Audyssey to set them to the level audyssey wanted them to be, this is -4db for the sub2, -5db for the sub3, sub1 has no PEQ/Menue, only a knob, its about... -6db
 
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Elitzur–Vaidman

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The REW sim picture he posted shows 80hz. Provided this is what’s used in his EQ.
Ahh, missed that. Thanks!

I have 3 subs, so only saying "raise your sub" is a bit problematic, as i dont know which one ;)
I used Audyssey to set them to the level audyssey wanted them to be, this is -4db for the sub2, -5db for the sub3, sub1 has no PEQ/Menue, only a knob, its about... -6db
Would it be too difficult to make 3 measurements, one for each sub? Others might have better suggestions.
 

HarmonicTHD

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I use 80hz as crossover, yes

I have 3 subs, so only saying "raise your sub" is a bit problematic, as i dont know which one ;)
I used Audyssey to set them to the level audyssey wanted them to be, this is -4db for the sub2, -5db for the sub3, sub1 has no PEQ/Menue, only a knob, its about... -6db
Ah. I overlooked that. With 3 subs you should have much more bass or are they all very small? Something is odd.

What AVR and Audyssey do you have? Does it let you control the subs independently?

Please double check that all subs were playing when you did your REW sweep. Audyssey can be tricky there and depends what Sub Mode you set. We had this just a few weeks back with some other user plus the subs did not go out of sleep mode either for him.
 
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slacki

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Please double check that all subs were playing when you did your REW sweep
i tested that, all where playing.
Audyssey can be tricky there and depends what Sub Mode you set.
Audyssey was turned off. This is to improve the curve before audyssey comes to play.

Would it be too difficult to make 3 measurements, one for each sub?
i can do that but takes quiet some time.. :/ thought with REW room sim i can find the "perfect" location for each of the subs without moving too much and measuring
 

HarmonicTHD

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i tested that, all where playing.

Audyssey was turned off. This is to improve the curve before audyssey comes to play.


i can do that but takes quiet some time.. :/ thought with REW room sim i can find the "perfect" location for each of the subs without moving too much and measuring
Ah ok. I don’t think it works that way. The REW sim assume ideal aligned (phase and level) subs. You turn Audyssey off that is not what you will get and you are comparing apples with oranges.

Can you run an Audyssey automated setup and then do a REW with this setup and post it here? So we can see if your subs are still wayyy too low.

But yes in general to optimize you would have to measure the subs individually with timing reference for later manual alignment in Audyssey as it does not have automated sub alignment and is limited for using multiple subs as opposed to something like MSO.
 
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slacki

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the guys from marantz told me that it (audyssey on the cinema 50) should be able to work with multiple subs perfectly fine, but i also have an umik1 with minidsp available, so i could also try it with MSO.
I will later create that audyssey measurement and upload it
 

HarmonicTHD

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the guys from marantz told me that it (audyssey on the cinema 50) should be able to work with multiple subs perfectly fine, but i also have an umik1 with minidsp available, so i could also try it with MSO.
I will later create that audyssey measurement and upload it
It works but it does not automatically phase align multiple subs. You might trick it afterwards by first measuring each sub with REW and then manually tweak the distance setting in Audyssey of each sub to fit.
MSO is better that way, but that’s not to say it won’t work in your room with Audyssey alone.

I have 2 subs and it is fine with Audyssey’s automatic algorithm (I use MultiEQX too).

Looking forward to your REW measurements.
 

HarmonicTHD

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here we go, this is now absolute default settings from the audyssey app, with 3 measures from 3 close positions
View attachment 260853
Ah much better. Isn’t it. What do you think?
What smoothing did you use in the graph? Var?
The dip around 90hz is very very narrow and probably not audible. Still you can now starting to tweak a bit and see if it improves without cause dips to appear at other frequencies. Maybe see if you can fill in that somewhat broader dip, but much less pronounced around 75Hz.
 
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slacki

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Yeah of course its better, its EQ'd ;)
But as mentioned, i'd like to optimize the room as much as possible without Audyssey involved (at first), because when i want to listen without Audyssey (because sometimes it just kills too much bass etc.), i would also like to have a good curve

The measurement above was without any smoothing, this is now with var smoothing
withsmpooth.jpg

but now the other values are not so good...
rt60.jpg

rt60decay.jpg

waterfall.jpg
 
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