Rt60 (Schroeder Frequency)

[Nordo]

I have a very naive question regarding reading the Rt60 graphs.

I want to find the schroeder frequency for my well treated home theatre room.
I have attached the RT60 graph for my un-eq'ed sub, but I don't know how to read the RT60 time (or the shroeder frequency).
Can anyone please help?

 

[Bernard]

Hello,
I can't help much but you may read with interest and attention these three web pages :
here : http://www.roomeqwizard.com/help/help_en-GB/html/graph_rt60.html
here : https://amcoustics.com/tools/amroc
or here : http://www.bobgolds.com/Mode/RoomModes.htm (at the end of the page)

 

[Nordo]

Thanks.
I've already read the REW help page, and that didn't help my layman's brain at all.
The amroc was interesting to use, but not sure how to allow for the amount of treatment I have.
Cheers

 

[John Mulcahy]

The Schroeder frequency for a domestic-sized room will be around 200 Hz, it will be well above the sub's range unless you are in a stadium. RT60 isn't relevant at subwoofer frequencies in domestic rooms, look at the unsmoothed frequency response and the waterfall to see where the room's resonances lie and how well controlled they are. You can read more about the Schroeder (transition) frequency at https://www.soundandvision.com/content/schroeder-frequency-show-and-tell-part-1

 

[Nordo]

Thanks John.
As my room is well treated, with multiple frequency absorbers at first reflection points, and bass traps across the rear wall and in the front corners, I had guessed my Rt60 was around 0.5 - 0.6 sec.
This gave me a Shroeder frequency of 160 - 180Hz. So according to you, my guestimate wasn't too bad.

What I am trying to do is find the frequency where the transition occurs so that I can limit Audyssey to below that frequency (using the MultEQ Editor).
As you said, I should adopt 200Hz and be done with it.

The link is a great article for a layperson like me. Thanks.

EDIT: John M - Just had another look at my sub's waterfall (below). With your advice, I can now see two large resonances that I'll need to EQ (using my DPS1124P).
Now that I'm starting to understand what to look for on some of these charts, I'm amazed how bad the resonances are at 20 and 30Hz when they don't look too bad on the basic SPL.
Thanks again for your amazing program (just made another donation. )

 

[mladia]

Can you share your knowledge with me? What resonances should I be working on. What exactly should I do in terms of treatment? Thank you so much in advance.

 

[Nordo]

You obviously have not added any room treatment yet.
To get some more advice from the knowledgeable guys here, they will need some more information about the room - dimensions, wall finishes, seating locations, speaker locations, maybe a photo or two.
Room treatment is the cheapest way to increasing your sound quality, especially if you are a DIYer.
There are plenty of websites with good articles on room treatment.
I personally like Ethan Winer's articles on the Real Traps website - http://realtraps.com/index.htm (click on Acoustics Info).

 

[IWC Doppel]

Try moving the axis to 400ms and see what that looks like

 

[mladia]

You obviously have not added any room treatment yet.
To get some more advice from the knowledgeable guys here, they will need some more information about the room - dimensions, wall finishes, seating locations, speaker locations, maybe a photo or two.
Room treatment is the cheapest way to increasing your sound quality, especially if you are a DIYer.
There are plenty of websites with good articles on room treatment.

I have treatment in the backwall. The room is approx 13 feet length by 29 feet width. I have speakers on the short throw... How did you get to the conclusion I do not have ANY treatment? Honest question. I am a newb.

 

[mladia]

Try moving the axis to 400ms and see what that looks like

Sorry.. how do I do that? Distance in Audyssey?

 

[Nordo]

I have treatment in the backwall. The room is approx 13 feet length by 29 feet width. I have speakers on the short throw... How did you get to the conclusion I do not have ANY treatment? Honest question. I am a newb.

How far the "mountains" come toward you is an indication of the time it takes for the initial sound to die off. i.e. how bright the room is.
After 292ms, your "mountains" have not drop off very much.
The more you treat the room (correctly), the quicker you will see those "mountains" drop off.
However some mountains or ridges will still continue to come toward you (usually below 80Hz in a domestic-sized room). They are caused by room modes and are virtually impossible to control fully.
Read Wayne's excellent article on how to read Waterfall plots :- https://www.avnirvana.com/threads/a...ing-signal-levels-in-time-domain-graphs.7341/

 

[Nordo]

Sorry.. how do I do that? Distance in Audyssey?

He is talking about the Waterfall's axis that comes out of the page toward you. This is the time measurement of how quickly the initial sound dies off.
I don't have REW in front of me, but in any REW page the setting button is up toward the top right corner.
Here you can change the range of each of the 3 axies of the Waterfall plot - even after you have taken your test readings.

 

[John Mulcahy]

The SPL range of your waterfall makes it look worse than it is, doesn't look bad to me. If you post the mdat file for the measurement people can more easily see what the response looks like.

 

[IWC Doppel]

Sorry.. how do I do that? Distance in Audyssey?

Sorry for the delay in responding, changing the axis to show 400ms or 500ms is in the controls panel, you can adjust the base floor cut off in the limits, both top right

 

[IWC Doppel]

Sorry for the delay in responding, changing the axis to show 400ms or 500ms is in the controls panel, you can adjust the base floor cut off in the limits, both top right

My noise floor is nearer 40db than 35db I tend to lift the floor until I lose the long straight tails, not sure f that's correct ?

My

 

[Nordo]

Can you share your knowledge with me? What resonances should I be working on. What exactly should I do in terms of treatment? Thank you so much in advance.



View attachment 35455

@mladia
I don't know if you are still watching this thread, but for the information you are after, you would be much better off by starting your own thread in the Room Acoustics and Treatments section of the Forum.
You should get some genuine help in that sub-forum (plus a lot of useful information by just browsing).
Don't forget to include as much information as possible - room dimensions including height; wall, floor and ceiling materials; speaker placement; seating positions, etc.

 

[mladia]

You obviously have not added any room treatment yet.

is this better? I am really sorry because I really am struggling to provide you more information. Thank you.

 

[Nordo]

is this better? I am really sorry because I really am struggling to provide you more information. Thank you.

As a waterfall, I think that looks really good.
Your SPL looks a bit wild though, but that could be partly due to the dB scale (vertical scale).
I'm not saying to alter that scale, but because it covers a fairly small range, it makes small dB variations in your SPL look pretty ugly.

Because your waterfall plot looks quite good, I would concentrate on your SPL plot.
Does your receiver come with Audyssey or Dirac?

I still think you would be better in one of the other sub forums more suited to what you are trying to do (see my post above).
And don't forget to post more details on your room and your equipment.

 

[mladia]

As a waterfall, I think that looks really good.
Your SPL looks a bit wild though, but that could be partly due to the dB scale (vertical scale).
I'm not saying to alter that scale, but because it covers a fairly small range, it makes small dB variations in your SPL look pretty ugly.

Because your waterfall plot looks quite good, I would concentrate on your SPL plot.
Does your receiver come with Audyssey or Dirac?

I still think you would be better in one of the other sub forums more suited to what you are trying to do (see my post above).
And don't forget to post more details on your room and your equipment.

Thank you. I use Audyssey and REW.

 

[Nordo]

REW by itself won't make your system sound any better, but can show you where improvements can be made, and then the result of any action you take.
Room treatment is important, but so is listening positions and speaker placement (especially the Mains).

Audyssey, when used as directed, should dramatically improve your SPL (especially below 250Hz), as well as other parameters.
The first time I ever ran Audyssey (15 years ago, with an Onkyo receiver), even my uneducated ears heard an enormous improvement.