Help with reading my first REW graphs

moves

moves

Audioholic Chief
Ratings
123
#1
Hello - I just moved into my house and would like some input on how to read the 2 graphs that I just made. I understand what peaks and troughs (SP) are but not sure how to read them... meaning what is a big dip and what is nothing to worry about... what looks good and what does not....

Below is an overlay of my first two graphs... the green is with nothing on the walls and the blue is with a few panels laying against the wall..

I can see that with the panels... the 38.7 kHz range improved by about 7 db. I see there is also a big blue nasty dip somewhere around 160khz... What does all this mean and how to you go about fixing panels and such in an attempt to flatten the line as best you can.. I know flat is impossible but I've hear that the line should be around + or - 3db of the main line...

Also, where should the main line reside on the db scale? I used the umik and its calibration file and set the sound generator to 75db.. What next?


Screen Shot 2018-07-25 at 3.57.27 PM.png
 
everettT

everettT

Audioholic Ninja
Ratings
1,154 9 15
#2
You really want to take away, not add with most EQ. Are we to assume that there is still a sub in the system? Did you use the REW speaker placement tool to see what the model is when moving said sub?
 
moves

moves

Audioholic Chief
Ratings
123
#3
You really want to take away, not add with most EQ. Are we to assume that there is still a sub in the system? Did you use the REW speaker placement tool to see what the model is when moving said sub?
I don't have a sub. Currently it's a 5.0 system. I didn't use the REW speaker placement tool.. not sure what that is.
 
KEW

KEW

Audioholic Warlord
Ratings
4,733 22 9
#4
That bass looks pretty good for no sub! What speakers? How big is room?
I don't think you can expect standard room treatments to have much effect below 200 Hz.
If you moved the microphone a couple of inches you would probably see more variation!
Why did you set the top of the range to 200Hz instead of measuring on up to 20kHz?
I know many people only focus on tuning the low frequencies, but it seem like you would want to measure the entire audio spectrum in your new home to make sure there is nothing egregious. Also, that would show you what benefit you get from the treatments!
 
moves

moves

Audioholic Chief
Ratings
123
#5
That bass looks pretty good for no sub! What speakers? Totem Wind How big is room? 13 X 35 feet with the listening position 6-7 feet away from the speakers.

I don't think you can expect standard room treatments to have much effect below 200 Hz. Agreed
If you moved the microphone a couple of inches you would probably see more variation!
Why did you set the top of the range to 200Hz instead of measuring on up to 20kHz? I didn't lol I set the tone volume with the spl meter in REW and clicked on Start Measure
I know many people only focus on tuning the low frequencies, but it seem like you would want to measure the entire audio spectrum in your new home to make sure there is nothing egregious. Correct :)Also, that would show you what benefit you get from the treatments!
I will see if I can set the top range to 20khz.
 
Last edited:
moves

moves

Audioholic Chief
Ratings
123
#6
I think it was just zoomed in because now I see 30.0 kHz.
I feel the blue line looks better than the green no? Next is how do I go about making it better? for example, how do I located the areas in the room that need fixing?
Screen Shot 2018-07-25 at 4.43.25 PM.png
 
moves

moves

Audioholic Chief
Ratings
123
#7
So I just put some panels on the walls and played around and I think this is the best result that I got.. Seems like there is an issue at 40 60 and 80 khz... how does this graph look? Is there anything I can do about all those squiggles in the higher frequencies?

this2.png
 
KEW

KEW

Audioholic Warlord
Ratings
4,733 22 9
#8
I'm not the person to really help you as I haven't used REW; however, while we are waiting for someone better, you might locate where in the program you apply smoothing. I don't remember for sure, but it seems like something like 1/12th octave smoothing is recommended.
Too much will get you an artificially good looking curve, and too little (as in none used in your chart) and you get all of the essentially vertical lines in the curve that make it unreadable!
 
KEW

KEW

Audioholic Warlord
Ratings
4,733 22 9
#9
So I just put some panels on the walls and played around and I think this is the best result that I got.. Seems like there is an issue at 40 60 and 80 khz... how does this graph look? Is there anything I can do about all those squiggles in the higher frequencies?

View attachment 25160
This curve looks artificially better than it is because you have compressed the Y-axis. Set the range for SPL to read from 40dB to 100dB. Again, I'm not sure if that is the standard recommended, but it will give you good resolution.
 
KEW

KEW

Audioholic Warlord
Ratings
4,733 22 9
#11
If you apply smoothing and expand the range, you will be able to much better compare teh blue vs green FR's.
...and you will better be able to see if teh red curve is better.
It does look like the blue curve is better, but really not very clear with no smoothing. You don't need the smoothing if you are only measuring the low frequencies (say, below 200Hz),but it becomes important if you want to make sense of the higher frequencies!
 
WaynePflughaupt

WaynePflughaupt

Audioholic Field Marshall
Ratings
629
#13
The last two graphs are useless because of the huge vertical scale of over 350 dB. That kind of scaling would make the Grand Canyon look like a Kansas prairie. Your first graph scaled for 45-105 dB is correct.

In other news, that little camera icon at the top left of the REW screen will let you save the graph as a .jpg. No need to do screen shots.

The "squiggles" at the top end is comb filtering. Perfectly normal in any room that's not as acoustically dead as a recording studio. Looks worse than it sounds. Smooth the graph for 1/6 or 1/3-octave to get a visual representation that better resembles what you're actually hearing.

Regards,
Wayne A. Pflughaupt
 
moves

moves

Audioholic Chief
Ratings
123
#15
I'm not the person to really help you as I haven't used REW; however, while we are waiting for someone better, you might locate where in the program you apply smoothing. I don't remember for sure, but it seems like something like 1/12th octave smoothing is recommended.
Too much will get you an artificially good looking curve, and too little (as in none used in your chart) and you get all of the essentially vertical lines in the curve that make it unreadable!
Yea I've read about smoothing but I don't have a minidsp so I am not sure what it would be useful for?
 
moves

moves

Audioholic Chief
Ratings
123
#16
The last two graphs are useless because of the huge vertical scale of over 350 dB. That kind of scaling would make the Grand Canyon look like a Kansas prairie. Your first graph scaled for 45-105 dB is correct.

In other news, that little camera icon at the top left of the REW screen will let you save the graph as a .jpg. No need to do screen shots.

The "squiggles" at the top end is comb filtering. Perfectly normal in any room that's not as acoustically dead as a recording studio. Looks worse than it sounds. Smooth the graph for 1/6 or 1/3-octave to get a visual representation that better resembles what you're actually hearing.

Regards,
Wayne A. Pflughaupt
Sweet thanks for the camera tip as well as the scaling... Here is the graph in the correct scale unsmoothed

Right scale best.jpg


Here the same graph smoothed to 1/6

same graph smoothed to 1:6th.jpg



How does it look? It sounds alright I guess... is the graph poo?
Right scale best.jpg
same graph smoothed to 1:6th.jpg
 
moves

moves

Audioholic Chief
Ratings
123
#18
I'm not the person to really help you as I haven't used REW; however, while we are waiting for someone better, you might locate where in the program you apply smoothing. I don't remember for sure, but it seems like something like 1/12th octave smoothing is recommended.
Too much will get you an artificially good looking curve, and too little (as in none used in your chart) and you get all of the essentially vertical lines in the curve that make it unreadable!

Ah I see so the smoothing is for better readability of the graph. I see!
 
WaynePflughaupt

WaynePflughaupt

Audioholic Field Marshall
Ratings
629
#19
Unsmoothed is best for analyzing below 200 Hz. Above that, smoothing is recommended to prevent the graph from looking scary with the comb filtering.

Your bass has some serious nulls (the deep, sharp depressions). Can you give us a map of the room and your speaker locations, or some pictures?

Regards,
Wayne A. Pflughaupt
 

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