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Discussion Starter #1
Hi,
please forgive me and give me some ideas concerning room acoustic tweaking.
my english isn't enough good to allow me to understand your posts without a little kick in the .....

can someone of you tell me which are the steps to make to start with rew?
i've read all the help files and i'm ready to test.


which are the graph's to watch to find how to position bass traps?
i don't understand which relationships i can find between modal resonances and ...the places how
to put absorbers and so on.


i've basic knowledges, taken from F. ALTON's book but i'm not able to match them with rew...


please help


thanks in advance
alessandro suppiej
 

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Waterfalls are the best graphs for determining the effectiveness of bass traps. I think the best place for them is typically corners, but it would be best to consult your vendor for directions.

Here's a step by step of the REW setup once the soundcard calibration and mic or meter calibration are loaded, and the cables are all hooked up and ready to go.


1. Prepare to run the Check Levels routine (Settings icon, Soundcard tab) selecting Check/Set Levels with Subwoofer in the Levels pull down box, with the SPL meter at the listening position (or the measurement mic, if that’s what your using for the measurements) and the dial of the meter at 80dB position.

2. Change Input Device Input and Output Device Output from Default to USB Audio, or the name of the soundcard, if that option is available, and Speaker for output, and Line In for input.

3. Begin the Check Levels routine. Ensure the REW output VU meter is at -12db and the Sweep Level at -12dB. If those fields are blank, check the two Control Mixer Volume boxes.

4. Set the Wave Volume at 1.000 and the Output Volume about ~0.500. (If those fields are blank).

5. Adjust your receiver’s volume control so the actual standalone Radio Shack SPL meter reads ~75db at the listening position. Then adjust REW Input Volume to end up with -18dB on the REW input VU meter.

6. Still in the Settings section, run the Calibrate SPL routine (Mic/Meter Tab) to match REW's SPL meter to the real SPL meter to ~75dBSPL. Make sure the “C Weighted” SPL meter is checked (if you’re going to use the meter to make the measurements).

7. Close Settings window. Run the Set Target Level routine (Target Settings icon to left of screen), which will set the target to ~75dB. Make the Speaker Type selection for what you want to measure – subwoofer, full range, etc. For subwoofers and bass-limited full range measurements, also, set the Cutoff, which is the crossover frequency you’re using.

8. Run the Measure routine.

9. Using the Graph Axis Limits icon, set the vertical scale to 45dB to 105dB and the horizontal scale for subs to 15Hz to 200Hz.

10. Select Equalizer from the Menu Bar at the top of page, to call up windows to tweak EQ filters.

11. To save the graph, select Graph from Menu Bar, then Save Graph as JPG. Use 800 size setting.

11. To get a waterfall graph, select the Waterfall tab at the top. Then press Generate Waterfall icon at the bottom of the screen.


Regards,
Wayne
 

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Discussion Starter #3
thanks Wayne , why asking vendors the right position?
doesn't rew help me doing that?
isn't possible to know where modes falls?
i've read that is possible to know where is the highest pressure of the mode.
and so, knowing where the speaker is, i think it's possible to calculate where the 'line' goes through.
sorry for my poor english
 

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isn't possible to know where modes falls?
i've read that is possible to know where is the highest pressure of the mode.
I think by “where” what you really mean is, “what frequency?” That’s not the same thing as deciding where the best location for a bass trap is. REW measurements can also tell what frequency a room mode is, but it can’t tell you where in a room to locate a bass trap. Usually your best advice for that will come from the company that sold you the bass traps.

Regards,
Wayne
 

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Waterfalls are the best graphs for determining the effectiveness of bass traps. I think the best place for them is typically corners, but it would be best to consult your vendor for directions.
Hi, Wayne:
Could you give us same methods or some examples to show, how the effectiveness of bass traps were determined by the Waterfalls.:scratch:

Thanks.

Yuan
 
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