Initial room response graph help

[dano1122]

Hi everyone. I got REW up and running w/ ADS instant music soundcard USB and CM-140 meter (no .cal file). I took a measurement and the result is below. I believe I am doing everything ok and check levels comes back within tolerance for the input level. I am testing to 200Hz through the SPDIF of my XR57 receiver. How does room response look? Room is roughly 14Wx22Lx10H. Thanks for any comments and constructive criticism. I hope this thread can be a work in progress.

p.s. i'm not sure what that blue line going fading downward from left to right is on the graph.

[dano1122]

to update my original post: i had the left main hooked up also and did not realize that it was outputting sound as well so i disconnected and am rerunning the measurement with just the subwoofer. should i be doing this via spdif to the receiver or analog?

[brucek]

should i be doing this via spdif to the receiver or analog?

Analog.

You need to use a meter/microphone calibration file that matches the meter you're using.

Post your graphs with a vertical scale of 45dB to 105dB and horizontal from 15Hz to 200Hz and a target of 75dB.

To save graphs, click the icon in the bottom left of the graph panel.

blue line going fading downward from left to right is on the graph

That's your target for the sub, with the crossover you set in REW.

Did you read the very well written REW HELP FILES

brucek

[dano1122]

Thank you everyone for reading and being patient with me. It would seem that in retrospect my initial post was a little premature. I had been reading the REW help files to help me setup my first graph but had insufficiently setup my measurement settings. Thanks for the additional guidance. The following two graphs show my in-room measurements with the following settings:

CM-140 w/ ECM8000 cal file, meter set to dBc, 25-80 level, fast
ADS instant music soundcard cal file loaded (no input volume control via REW or XP)
Setup: soundcard right rca -> avr (xr-57)-> sub out -> sub (aci force 10")
crossover 80hz
Volume: Wave 1, Output Volume .891, Sweep Level -12.0

Both graphs are 45-105dB, 2-200Hz, 512k length, 1 sweep
Graph 1 - Levels: set w/ sub, -12 output,-14 input, avr volume -25


Graph 2 - Levels: set w/ sub, -12 output, -11 input, avr volume -20
(took 2nd measurement higher avr volume to bring up graph nearer to 75dB line)

On the 2nd measurement I got warnings about clipping and high levels


The graphs look hilly =\

[dano1122]

1 more graph with output volume at 1 and avr at -30

quick question, all these measurements are sub only, if i wanted to measure sub and both l and r speaker how would i go about that?

[brucek]

all these measurements are sub only, if i wanted to measure sub and both l and r speaker how would i go about that?

Do nothing different, except hook up or turn on the mains.

You will need to reset the levels because the mains will change the loudness. But basically you do the same measurement with the sub as you did before.

Then you look at the area around the crossover and adjust the phase of the sub if there is a problem and try and get a smooth transition between the mains and sub.

BTW, did you do the Calibrate SPL routine and after that press the Set Target Level button?

brucek

[dano1122]

brucek wrote:

Do nothing different, except hook up or turn on the mains.
You will need to reset the levels because the mains will change the loudness. But basically you do the same measurement with the sub as you did before.
Then you look at the area around the crossover and adjust the phase of the sub if there is a problem and try and get a smooth transition between the mains and sub.
BTW, did you do the Calibrate SPL routine and after that press the Set Target Level button?
brucek

I hooked up the mains prior but only had sound coming from the right due to the rca right only being hooked up on the avr. i guess i should make the full rca connection at both halves and retry?
thanks for the tip about the phase, ill check it out, i know i can move it around too and ordered a 25' cable to do so.
i did do the calibration routine but not sure if it was before or after i loaded the cal file, i will double check thank you

[Wayne A. Pflughaupt]

Dan,

I don’t know if you have a BFD or not, or plan to use one, but your response is really bad – virtually un-equalizible, in my opinion. I suggest trying to re-locate your sub.

Regards,
Wayne

[brucek]

I hooked up the mains prior but only had sound coming from the right due to the rca right only being hooked up on the avr. i guess i should make the full rca connection at both halves and retry?

Some people use a Y-splitter to feed the receiver with left and right and some people hook up both the left and right channel of the line-out from the soundcard. The line-out in REW has both channels active (only one channel on line-in though).

Use a horizontal axis of 15Hz to 200Hz and the same vertical that you have now.

brucek

[dano1122]

brucek wrote:

BTW, did you do the Calibrate SPL routine and after that press the Set Target Level button?

brucek

i redid the spl level calibration and matched it at 69db and finish
Wayne your statement confirms my suspicions of one horrible bass response, the 25' cable should open up alot of relocation options
I have 2 tri-traps, 2 2x4x4, and 3 2x2x2 acoustic panels coming from GIK to help the issue
the 15Hz-200Hz graph is as follows, output volume at 1 still

compared to the previous


thank you. going to try the phase and l/r/sub measured

[dano1122]

i tried flipping phase to 180 instead of 0 but the graph remained nearly identical so i am not uploading it.

next i will try to move the sub around

i had no idea the room could play this kind of havoc on low frequency response

one more graph done with phase at 0 uploaded for records sake, i adjusted the vertical limit to 35-105dB to give a better view of the dips

[dano1122]

here is a graph with the sub pulled out into the room; it looks much better to me

question, how come the majority of my response is under the 75dB mark? if i try to raise this through increasing output volume i run out of headroom on level check and it warns me about clipped signals because.... what does this mean about bass in general?

[brucek]

how come the majority of my response is under the 75dB mark?

You can set any level you wish. Once the wave is set to 1.000 and the Output set to 0.500 and the Sweep set to -12db, then the volume at the RS SPL meter is determined by the volume control of the receiver. Go ahead and set it to 80dB if you like.

Then adjust the Input level control of REW to the correct level.

Then Calibrate SPL routine and set it to match the RS SPL meter of ~80dB

The click Set Target Level and it will return 80dB.

Then measure......

We recommend 75dB, but if you want it higher, go ahead.

brucek

[dano1122]

The only problem i see with that is that i don't have any control of input level, it is locked at .250. soundcard is USB ADS instant music. Im gona try a couple different positions for the subwoofer but the graph i posted from where it is now seems pretty good. I do notice though that as I move the mic around the room (CM-140) that the response can change drastically.

[brucek]

The only problem i see with that is that i don't have any control of input level, it is locked at .250.

Sure you do. Go to the Windows mixer and turn it up.

Mixer record.jpg

brucek

[dano1122]

on my ADS instant music in the windows volume control panel i can only select playback for volume adjustments. the recording ticker is not selectable. i'm guessing that the line-in matches with the input volume control in REW which is also greyed out and not selectable in REW for me. in the REW help files under checking levels it mentions that, "Some soundcards do not provide an input volume control (e.g. some USB cards). As long as the signal RMS level is within the -30 to -12dB range when the speaker/subwoofer cal signal is playing everything should work OK. If the level is below -30dB try reducing the meter range to raise the level, but be careful not to reduce the range to the point the meter is overloaded. If the level is above -12dB try increasing the meter range to lower the level."

btw, why does the graph dip and then rise so much after 80Hz if that is my crossover point? I only have the sub connected.

[brucek]

why does the graph dip and then rise so much after 80Hz if that is my crossover point? I only have the sub connected.

If the sub is connected from the receiver, usually the slope of the sub crossover low pass filter is 24dB/octave. Doesn't look like yours is dropping that quickly. Some older LPF's used to be 18dB/octave and the dropoff was slower.

brucek