REW Question RT60, EDT, ..... - Home Theater Forum and Systems - HomeTheaterShack.com

 
Thread Tools
post #1 of 10 Old 08-28-16, 02:25 AM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
REW Question RT60, EDT, .....

Hi Forum,
love REW, and read a lot here in the forum.
I have some questions and it would be nice to get a little help and support from you. Thank you.

1)Is there a way to get a more static reading of REW RT60 graph? Everytime i measure it is really fluctuating a lot. If i measure 4 times at the same micposition with nothing else changed, "topt" changed everytime for 0,2 to 0,4 or 0,5 in different frequency ranges. How could i generate a more static measurement. I have really low ambient noise.
Is a longer sweep with multiple sweeps avareging better? It still fluctuates when i measure like this. But i think a little bit less, than with shorter sweeps.

2)I tried to find infos about "correct" rt60 measuring. Is it more significant to measure with different mic and also different speaker position, i read its even better to put the speaker in one corner and the mic in the other corner and than to avarege the measurements by eye?!?!?

3)When i measure a friends studio. The EDT curve in the rt60 graph (manual illustrates it shows the rt60 for the first db decay) shows a really odd graph. Where the lower frequency region 80-400 is at 0,15s and the higher region 1-8khz at 0,4sec. Does this illustrate a possible problem in the first 20ms? Speakers are soffit mounted. I know "topt" gives a more solid reading here, but in general the trend is the same as from the EDT curve.

4)Oh and a simple one....does the RTA-Analyzer (in combination with the generator) make use of the mic calibration file i set in the preferences?

Last edited by Micheallong; 08-29-16 at 05:12 PM.
Micheallong is offline  
Sponsored Links
Advertisement
 
post #2 of 10 Old 08-30-16, 04:28 AM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
Re: REW Question RT60, EDT, .....

4) I tested it allready with an extrem wrong tect *.cal file. And the RTA makes use of the cal file. Thats nice.
Micheallong is offline  
post #3 of 10 Old 09-03-16, 03:49 AM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
Re: REW Question RT60, EDT, .....

No advices for RT60?
Micheallong is offline  
post #4 of 10 Old 09-09-16, 06:13 AM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,410
Re: REW Question RT60, EDT, .....

The RT60 results should be consistent for successive measurements, if they aren't there may be some other issue with your measurement setup. Easiest way to check that would be for you to post some of the measurements where you see variations.

RT60 is most appropriate for large spaces. Putting a speaker in a corner and a mic in another corner is a way to excite and measure all the modal resonances of the space. Not necessarily of much relevance for a studio.
JohnM is online now  
post #5 of 10 Old 09-14-16, 02:17 PM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
Re: REW Question RT60, EDT, .....

Hi John,
thank you so much.
Here is a group of measurements with the mic at the other side of the room.
http://expirebox.com/download/317240...5398e5a10.html


BTW. Do you have a suggestion on my 4) question from the firt post? Or do you also need a measurement.
Thank you.
Bye
Micheallong is offline  
post #6 of 10 Old 09-14-16, 03:01 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,410
Re: REW Question RT60, EDT, .....

Q 4 was does the RTA use the cal file. The answer is yes.

That's an odd set of measurements. The largest peak occurs after several other peaks have already arrived, suggesting the direct sound is lower than the reflected sound, which is very unusual. There are very, very large 50 and 80 Hz resonances. What kind of environment is it measured in? What is in the room? Where were the speaker and mic placed and what kind of speaker and mic are they? Some of the measurements in that group also have significantly higher noise levels than others, is the location affected by traffic noise, or trains, or some other noise source?
JohnM is online now  
post #7 of 10 Old 09-15-16, 02:28 AM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
Re: REW Question RT60, EDT, .....

Specs: Room 4x5x2,5m, speaker KRK vxt8, living room with some furniture tables absorber etc., mic dayton
Measuring: speaker near frontwall, and mic near the rearwall floor corner.....i think the earlier peaks are caused because the mic was a little bit of center and one speaker arrived earlier.

So in conclusion i need much more direct signal for RT60 measuring and the mic centered? I thought i should be more in the diffusefield a little bit offcenter to catch more of the ambience/verb to measure it? Perhaps thats a wrong guess?
You mentioned the difference in noise levels. Did you meter (see) it from the lower end of the impulse-graph? Or is there a better way to look at noise floor? I not sure what could cause the differen noise levels you mentioned because it was really quite and all doors and windows were closed.

Here is another small measurement set: with the mic centered 50cm in front of the rear wall. No prereflections this time. But still a lot of variation in the rt60 graph.
Thanks

http://expirebox.com/download/c86160...b18a2b0c2.html
Micheallong is offline  
post #8 of 10 Old 09-15-16, 02:40 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,410
Re: REW Question RT60, EDT, .....

There isn't a meaningful reverberant sound field in such a small space. The RT60 results will be fairly consistent above a few hundred Hz, but they are still not reverberant decay in the sense for which RT60 is intended. In small spaces the results will vary significantly with mic position, unless you plan to listen with your head stuck in that corner I suggest you make your measurements with your mic where your head would be when you do listen

It was the variation in the impulse response noise floor I was noticing in the previous measurement set. If there is no acoustic reason for that the cause might be electrical - for example, WiFi activity can interfere with measurements.
JohnM is online now  
post #9 of 10 Old 09-16-16, 02:11 AM Thread Starter
Shackster
Micheallong
 
Join Date: Jul 2007
Posts: 15
Re: REW Question RT60, EDT, .....

Okay, thank you so much for helping me. Is there another type of measurement to proof if a small room is too dull or to measure high and mid frequency absorber in smaller room. I see on most measurements a slight dip at the upper end. In the Early Decay Plots there is also a clearly dip in the high end. Is this an indication for dullness or is this also not enough information within small rooms? Im interested in measuring with and without carpet or curtain, or shelvs.So i thought RT60 would be the best choice to even out the rt60. Its more a question in generall.


Sorry John, i meant question 3 before. May i post a measurement of my friends studio? Perhaps you have an idea where i could find the error.
Attached Thumbnails
REW Question RT60, EDT, .....-decy.jpg  

Micheallong is offline  
post #10 of 10 Old 09-16-16, 02:25 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,410
Re: REW Question RT60, EDT, .....

EDT will not give meaningful information in small rooms and it is completely useless below a few hundred Hz in such rooms as the response there is dominated by modal resonances. To look at the early behaviour of the impulse response use the envelope (also called Energy time Curve).

Above a few hundred Hz the RT60 plot will give a reasonable indication of relative absorption levels. For more advice on studio treatment in general gearslutz is a good resource.

It is entirely normal for listening position (as opposed to near field) measurements to roll off at the high end, don't be tempted to try and boost anything to change that.
JohnM is online now  
Reply

Bookmarks

Tags
edt , question , rew , rt60

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome