Measuring, room responses using REW..

[elangoas]

After using the Audyssey Multi EQ mobile app & reading thru many threads/posts/videos on AVSforum / HTshack/ Youtube on REW guide, I wanted to give REW a try..

Some AVSforum members have put enormous effort in compiling detailed guide :clapping:.. Here is the link - http://www.avsforum.com/forum/91-au...surement-techniques-how-interpret-graphs.html (Courtesy AVSforum)

https://www.dropbox.com/s/zdhq72a1puyyxpr/REW 101 HTS Current Version.pdf?dl=0

All i have is an Audyssey Microphone that came with my Denon AVR x3300 & a PC with HDMI out(Nvidia Graphics card), so decided to get started with it..

Plugged it in to Mic in on my Win7-PC and made the necessary settings under recording devices..
- Set volume to 75
- Mic boost to 0%

I also downloaded ASIO4ALL and configured the output settings in REW per the guide..

When i clicked calibrate the Mic, REW popped up with a msg that "maximim SPL with this calibration is 76db. If you need to measure higher SPL the input sensitivity will need to be reduced".

When volume on AVR was -15db approx, test tone was showing -12db (out) from REW, the Level in was -28db and Ref in -30db...REW SPL meter was showing 58db..

Am not sure if i missed any setting in REW, could someone help here...

I wanted to measure sub response, re-position for a better response if reqd..

 

[kaptan]

Looks like the microphone. Instead of audyssey mic why dont you try a different microphone.

 

[elangoas]

Looks like the microphone.

This was a Mic shooutout performed by one of the AVSforum member with an other calibrated microphone.. From other threads, i gathered info that the Audyssey Mic has variance of +/-2 db until 5Khz, beyond that there is variation (Think because it doesn't have calibration files req for REW measurements)

Instead of audyssey mic why dont you try a different microphone.

The likes of USB Microphone UMIK, might cost 10K here.. Don't want to spend that much on something, where am yet to get hands-on..

Audyssey Mic is something which i have, so thought to learn REW measurements thru it without spending..

 

[sud98]

I had the same problem, the meter didnt show beyond 58, I changed to a different laptop and it worked fine. It appeared to be a problem of the headphone jack of my laptop.

 

[elangoas]

I had the same problem, the meter didnt show beyond 58, I changed to a different laptop and it worked fine. It appeared to be a problem of the headphone jack of my laptop.

I had plugged the Microphone to Mic port (pink one) on my PC.. There are two other ports adjacent to it.. (Green & Blue), think Line in ports..Can i try this port?

 

[sud98]

I had plugged the Microphone to Mic port (pink one) on my PC.. There are two other ports adjacent to it.. (Green & Blue), think Line in ports..Can i try this port?

I am quite sure you cant. Try the hdmi cable if that works for you.

 

[manoj.p]

You need to calibrate the mic input port of the pic through REW first. Do a loop back connection (audio output from pic to mic input connection) and measure. Save it as mic input calibration file and use it for further measurement.

There are documents on web for this. After this, any shortcomings of your audio card are taken care.

 

[elangoas]

I am quite sure you cant.

Right.. Looks like Mic-in jack on PC is for mono signal & line-in jack is for stereo signal

Try the hdmi cable if that works for you.

Didn't get you.. I used HDMI out from PC to AVR.. Did you mean something else ?

 

[elangoas]

You need to calibrate the mic input port of the pic through REW first. Do a loop back connection (audio output from pic to mic input connection) and measure. Save it as mic input calibration file and use it for further measurement.

There are documents on web for this. After this, any shortcomings of your audio card are taken care.

Am not sure if i understood your statement correctly regarding loopback.. I understand, i need to save calibration files for future use..

This is the REW guide prepared by one of the AVS forum member, where he has used Audyssey Microphone on PC and HDMI out from PC/Laptop - http://www.avsforum.com/attachments/66264

I followed the guide, not sure if it covers loopback connection..


I guess, i messed few things..

When the REW SPL meter was displaying 58db, i used an SPL meter on android phone, which was showing 50db.. Only when i entered the value of 50db, it made the statement that max SPL with this calibration is 76 db SPL..

I will redo the REW calibration for the microphone and update here..

 

[sound_cycle]

Am not sure if i understood your statement correctly regarding loopback.. I understand, i need to save calibration files for future use..

https://www.roomeqwizard.com/help/help_en-GB/html/calsoundcard.html


ciao
gr

 

[elangoas]

https://www.roomeqwizard.com/help/help_en-GB/html/calsoundcard.html

ciao
gr

Great.. So creating a calibration file for the Mic, which can be used for future measurements is loop back calibration..(Correct me if am wrong)

Am concerned abt an issue here..

When i do the Mic calibration, REW pops up a window to enter the SPL reading from a physical meter (which i don't have) against the REW SPL meter..

Is it fine if i pick the value that is displayed in REW SPL meter and input it in the popup window for REW to calibrate the Mic?

The reason i ask this is, i saw a post in HTshack mentioning the same.. Basically to trick REW, in absence of physical SPL meter..

 

[tuff]

Maybe use an SPL meter from mobile?

 

[sound_cycle]

When i do the Mic calibration, REW pops up a window to enter the SPL reading from a physical meter (which i don't have) against the REW SPL meter.

I use a USB Umik and could gleefully skip these steps. I don't think you need a SPL meter because you are looping back the sound from the speakers into the mic. with a cable. See the glen kuras vid on yt or maybe this one

https://www.youtube.com/watch?v=zXV0yZCax-w

ciao
gr

 

[elangoas]

Maybe use an SPL meter from mobile?

Yes.. I used the SPL meter app.. It was showing 4 - 5 db lower than what was displayed in REW SPL meter..

When i raised the volume in AVR (-10db), i could feel the sound louder, buth for some reason, the mobile SPL meter was not registering the loudness..

I use a USB Umik and could gleefully skip these steps. I don't think you need a SPL meter because you are looping back the sound from the speakers into the mic. with a cable. See the glen kuras vid on yt or maybe this one

https://www.youtube.com/watch?v=zXV0yZCax-w

ciao
gr

USB Mic is just plug & play compared to these Analogue Mic..

I will revisit the steps and update here..

 

[elangoas]

Got UMIK-1.. Did go thru a detailed REW guide created by AVSforum members..

Trying to get hands-on with REW..First measurement of dual subs..

Not sure if i have did that correctly.. If incorrect, will post measurement again as req..

Info abt the living room -

14 W x 11 L x 9.7 H with few openings.. Will share image

At present, have placed the subs at front left & right corner's of the room..

My seating position is against the back wall..

Here are the measurement -

Appreciate your inputs on getting better room response if possible..

 

[elangoas]

One more pic of L + R + dual subs response from 20 Hz - 300 Hz in "Stereo mode", Audyssey disengaged, Crossover 120 Hz (between Fronts / Sub's)..

 

[sound_cycle]

Hi

The waterfall plot looks alarming but is not descriptive of your room.

Rescale y-axis to be about -30db from your peak SPL.

ciao
gr

 

[Hari Iyer]

I had previously used AKG mic with Shure mic preamp and now using UMM-6. In both cases setup was not an issue as the mic had its own calibration files. You need to also calibrate the laptop sound card. Most laptops seldom have flat output response.

 

[elangoas]

Hi

The waterfall plot looks alarming but is not descriptive of your room.

Rescale y-axis to be about -30db from your peak SPL.

ciao
gr

Here it is..

I had previously used AKG mic with Shure mic preamp and now using UMM-6. In both cases setup was not an issue as the mic had its own calibration files. You need to also calibrate the laptop sound card. Most laptops seldom have flat output response.

I missed that with Audysey Mic.. But now, i got the UMIK-1..

 

[sound_cycle]

You can now clearly see that you have ringing issues is the 40 - ~ 150 Hz range. Increase the time scale so that the hills don't get squashed (nose against glass) and you will see how bad. ~ 300 ms or less is what you would want . You can see 40 - ~ 80 squashing ringing beyond 450ms in your plot

You could try positioning your subs to get rid of this ringing (I recollect from other threads that was one of your intentions).

If you want to hear how it would sound without that boom before you start moving heavy subs, download and trial a room correction software, or Roon maybe. You should hear tuneful bass after that. A probably unnecessary warning, it will seem underwhelming initially, because it is quality not quantity.

Do see also if you have this boom with your subs not hooked up. Probably yes, it is a bane of small rooms

ciao
gr