New to REW, difficulty calibrating and more questions - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #1 of 15 Old 12-14-16, 12:01 AM Thread Starter
Shackster
 
Join Date: Dec 2016
Posts: 13
New to REW, difficulty calibrating and more questions

Hello,

I am in need of help! I am currently in the process of treating my room to utilize my new Focal Alphas, and I am new to REW.

First, I am having some difficulty calibrating my REW. For some reason, when I try to calibrate REW's SPL meter, using a behringer ecm8000, the spl rating is not matching up with my hand-held SPL meter set to Slow, C-weight. Do I need to be using different settings on the REW SPL meter since I am using a mic and not a SPL? Due to this, I have gotten some extremely wonky results, especially since my monitors have been calibrated to 75dB with pink noise.

Additionally, I was told that when actually doing the measurements, it should utilize both speakers. For some reason it is only letting me choose one at a time. Will this affect my results, or do I just take an average between left and right?

Finally, once I have my measurements, would anyone be willing to help interpret my results, or enlighten me by way of tutorial or other means to analyze it myself? I have had some pretty accentuated bass frequencies in my room when I was using different studio monitors. Now that I have some beefy new Focals, I am in desperate need to figure how much more treatment I need to purchase or how much I need to utilize the built in lowpass filters.

Any help is greatly appreciated!
Roughroom is offline  
Sponsored Links
Advertisement
 
post #2 of 15 Old 12-14-16, 05:49 AM
Elite Shackster
Wayne Myers
 
Join Date: Jun 2012
Location: Lincoln, NE
Posts: 4,838
Re: New to REW, difficulty calibrating and more questions

Quote:
Roughroom wrote: View Post
Hello,

I am in need of help! I am currently in the process of treating my room to utilize my new Focal Alphas, and I am new to REW.

First, I am having some difficulty calibrating my REW. For some reason, when I try to calibrate REW's SPL meter, using a behringer ecm8000, the spl rating is not matching up with my hand-held SPL meter set to Slow, C-weight. Do I need to be using different settings on the REW SPL meter since I am using a mic and not a SPL? Due to this, I have gotten some extremely wonky results, especially since my monitors have been calibrated to 75dB with pink noise.
Not quite surie what you mean. With a SPL meter as your reference, you are telling REW what the SPL is for a given level of input from your mic for a given gain setting on the mic preamt of your audio interface. Once done, as long as you do not change that gain, the result should match exactly. What is the "difference" you are seeing?

Quote:
Additionally, I was told that when actually doing the measurements, it should utilize both speakers. For some reason it is only letting me choose one at a time. Will this affect my results, or do I just take an average between left and right?
You were told incorrectly. Meaningful results require that speakers be measured one at a time. The human psychoacoustical brain does the "separating" of signals from different directions as we listen, a microphone cannot and at high frequencies gives eratic - and useless - and misleading - results due to phase cancellations at high frequencies.

Quote:
Finally, once I have my measurements, would anyone be willing to help interpret my results, or enlighten me by way of tutorial or other means to analyze it myself? I have had some pretty accentuated bass frequencies in my room when I was using different studio monitors. Now that I have some beefy new Focals, I am in desperate need to figure how much more treatment I need to purchase or how much I need to utilize the built in lowpass filters.
Post your measurement .mdat file and we'll take a look.
AudiocRaver is offline  
post #3 of 15 Old 12-14-16, 06:00 AM
HTS Senior Moderator
 
Wayne A. Pflughaupt's Avatar
 
Join Date: Apr 2006
Location: Katy, Texas
Posts: 8,916
Send a message via Yahoo to Wayne A. Pflughaupt
Re: New to REW, difficulty calibrating and more questions


Welcome to the Forum, Roughroom!

You can’t calibrate REW’s SPL meter with a mic directly. You must have a calibration file for the mic (loaded under Preferences -> Mic/Meter) that includes a sensitivity figure. Otherwise you should just use your hand-held SPL meter to do it, a shown in Section 8 of the REW Help Files.

As for measuring with both speakers or one, that depends on the measurement signal and your intent for measuring. As AudiocRaver mentioned, using the sine wave sweep with both speakers can register a droop in the graph at high frequencies, caused by comb filtering resulting from the mic not being perfectly centered between the speakers. For full range measurements, pink noise is a better signal source for measuring with both speakers.

However, since you’re primarily interested in the lower frequency range, that won’t be an issue for you. If you want to measure both speakers simultaneously, just split the analog output of your sound card to the inputs of your speakers.

You didn’t go into details on what you hope to accomplish with your treatments, but if it’s for the low frequencies their main benefit is reducing ringing (aka low frequency decay times), which can make the bass sound tighter. However, if you have large low frequency peaks or troughs you’re trying to address, it takes a lot of treatment to minimize those, typically more than most people want in a room.

Regards,
Wayne



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
|
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.

Wayne A. Pflughaupt is offline  
 
post #4 of 15 Old 12-14-16, 07:15 AM
Elite Shackster
Wayne Myers
 
Join Date: Jun 2012
Location: Lincoln, NE
Posts: 4,838
Re: New to REW, difficulty calibrating and more questions

A teeny, tiny, minor correction Wayne. I believe the ECM8000 is an analog mic, so the calibration file will not have a sensitivity number, since it has to run through an audio interface.

Wayne P is correct, for subwoofers you can - and should - run the signal through all subs together for LF measurements. Above sub frequencies, I recommend running the speaker measurements separately.
AudiocRaver is offline  
post #5 of 15 Old 12-14-16, 04:31 PM
HTS Senior Moderator
 
Wayne A. Pflughaupt's Avatar
 
Join Date: Apr 2006
Location: Katy, Texas
Posts: 8,916
Send a message via Yahoo to Wayne A. Pflughaupt
Re: New to REW, difficulty calibrating and more questions


Quote:
AudiocRaver wrote: View Post
A teeny, tiny, minor correction Wayne. I believe the ECM8000 is an analog mic, so the calibration file will not have a sensitivity number, since it has to run through an audio interface.
Thanks for that somehow I had not made the connection that the sensitivity was only given with USB mics.

Regards,
Wayne




To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
|
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.

Wayne A. Pflughaupt is offline  
post #6 of 15 Old 12-14-16, 07:27 PM Thread Starter
Shackster
 
Join Date: Dec 2016
Posts: 13
Re: New to REW, difficulty calibrating and more questions

Thanks for the replies!

The main confusion about the SPL calibration was that I thought it was asking for me to put in the value being registered by my mic, not my SPL meter. Luckily, I just put in my SPL meter's output.

Hopefully the upload worked. I have been having some issues with my internet lately.

In regards to the room that I am in, it is a home studio. Luckily I do not do any live recording. All of my work is entirely within the computer, so I need to be confident that any changes I make to a mix are not caused by my speakers/room. I was ecstatic to find wholesale acoustic foam/treatment, so I have no qualms about the room looking like a padded cell

Thank you again for the help.
Attached Files Measurements.mdat (9.71 MB) 
Roughroom is offline  
post #7 of 15 Old 12-14-16, 11:06 PM
Elite Shackster
Wayne Myers
 
Join Date: Jun 2012
Location: Lincoln, NE
Posts: 4,838
Re: New to REW, difficulty calibrating and more questions

Your soundcard calibration file is very noisy, that should not be the case, and has a steady downward slant, that should also not be the case.(it gives your measurements the illusion of rising response at high frequencies)

The L and R impulse diagrams show pretty good reflection control, except within the first 1.5 sec or so. Surfaces close to the speakers &/or listening position are causing some irregularities that could affect imaging.

Freq Response:
  • vertical settings should cover a 60 dB range
  • measurements need not be done nearly so loud, use 75 or 80 dB level for sweeps
  • don't know what curve 1 is, "soundcard?"
  • do not try to fix freq resp before addressing other questions above, which affect the FR measurement accuracy
  • the dips at 60 to 80 hz will be hard to get rid of, the rest should be easier; the 60 to 80 hz dips are probably from reflection cancellations, getting rid of the reflection at that frequency is really tough
AudiocRaver is offline  
post #8 of 15 Old 12-15-16, 11:10 AM Thread Starter
Shackster
 
Join Date: Dec 2016
Posts: 13
Re: New to REW, difficulty calibrating and more questions

Thank you.

In regards to your questions:

1) I have no clue what to do about the soundcard calibration. I have tried using both inputs and outputs. I am curious if it is being caused by the drivers on it. It is an older Focusrite2i4 which is not fully supported on Win10, only works with beta drivers.

2) Unfortunately, the speakers are close to the wall, 11" to be exact. I am unable to preposition them. Would this be the cause of the imaging irregularities?

3) From my understanding, I thought I had the sweeps being produced at 75dB, at least that is what my external meter was showing. Since I know the meter is calibrated correctly, I most likely am ignorant to something within REW. I followed several tutorials while completing this process.

4) Curve1 was the measurement it produced while my soundcard loop was still connected. It showed up once I completed my calibration.

Finally, these measurements were taken while utilizing the Focal's built in low pass filter due to their position near the wall. It attenuates anything below 300Hz.

How should I proceed?

Last edited by Roughroom; 12-15-16 at 11:17 AM.
Roughroom is offline  
post #9 of 15 Old 12-16-16, 02:26 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,554
Re: New to REW, difficulty calibrating and more questions

The soundcard cal file is wrong, you'll need to clear in the Soundcard preferences that so it isn't used for any further measurements. You can remove it from existing measurements using the Change Cal button. Perhaps the loopback connection was on the wrong channel, but the measurements look OK so it isn't a big deal to just get rid of the cal and carry on.

The idea of calibrating REW's SPL meter is to tell REW the real SPL, as read from some external source (i.e. your own meter) so that REW can offset its own meter to read the same. After you've done it the REW meter and your external meter should be showing the same levels.
JohnM is offline  
post #10 of 15 Old 01-07-17, 11:44 PM Thread Starter
Shackster
 
Join Date: Dec 2016
Posts: 13
Re: New to REW, difficulty calibrating and more questions

Hello,

I recently put up the last of my room treatment. Here are the results. After the problems I have had with room eq, I decided not to add a calibration file because my most recent ones are no better than the original.

What did change:

1) Additional Room treatment at the first reflection points on the sides of the wall, above the listening position, and directly behind the listening position. All absorption. I have some additional treatment spread out along the side walls.

2) Studio Monitors calibrated at 67.5dB. For some reason it seems that the measurement was recorded at a much higher amplitude than my monitors produced.

3) Measurement sweep was done at -20dB instead of -12. For some reason it was clipping at -12. Nothing has changed in my setup, so I figured it was not going to be the end of the world.

I am by no means fluent in analyzing this data, but from what I am looking at, there are dips at 60-80dB, 600-800dB, and 2k-5k? How much of this could be caused by the output level of my monitors? If this is just a reflection of my room, or the less than desirable placement of my monitors that I cannot fix, then I guess it is not worth adding additional treatment. (Although I have space for more basstraps along the wall my monitors are placed.) Furthermore, would diffusion be of value, or do you feel that I have hit the maximum amount of treatment before I begin to just chase my tail? Lastly, are these fluctuations are enough to warrant a corrective eq?
Roughroom is offline  
Reply

Bookmarks

Tags
calibrating , difficulty , questions , rew

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