Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 495 - AVS | Home Theater Discussions And Reviews
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post #14821 of 14826 Old Today, 01:33 PM
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I'm using HDMI output from my laptop to the AVR for the test tones. My laptop only supports the "stereo" configuration and in the Output dropdown on the Soundcard tab my only options are HDMI #1 and HDMI #2 , which work as left/right speakers as expected.

In this scenario, is it possible to measure the subwoofer only, without any sound going to the right or left speaker? Or do I have to disconnect the front speakers if I want sub only, like I'd have to do with a non-HDMI output config?
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post #14822 of 14826 Old Today, 02:13 PM
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Originally Posted by lovingdvd View Post
I'm using HDMI output from my laptop to the AVR for the test tones. My laptop only supports the "stereo" configuration and in the Output dropdown on the Soundcard tab my only options are HDMI #1 and HDMI #2 , which work as left/right speakers as expected.

In this scenario, is it possible to measure the subwoofer only, without any sound going to the right or left speaker? Or do I have to disconnect the front speakers if I want sub only, like I'd have to do with a non-HDMI output config?
You will need to disconnect the front speakers to get a sub-only measurement. That's where running an external amp comes in handy--it is easier to turn off the amp, rather than unplugging the speakers.
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post #14823 of 14826 Old Today, 02:17 PM
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Below is the RTA of my room, does it looks normal to you? When I opened the SPL meter, it constantly read above 62dbs with just the fans of my projector and the Inuke running.
I have this issue also, but with the UMM-6 USB mic. My AC, refrigerator, and dvr all off. My noise floor seems to be around 60-62db. Interested to see what your issue might be.
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post #14824 of 14826 Old Today, 02:20 PM
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Jerry,

I set my front speakers to large and turned off Audyssey, but somehow bass mgmt still kicked in as you can see below. The frequency response looks really bad compared to my earlier cheapo speakers (HTIB type). Any advice?



In addition, during the measurement I hear strange noise from my left speaker at high frequency, which scared me. It never happened before with any other speakers, so my thought is would it be something wrong with my mic sensitivity? I am using the Umik-1 calibrated by Spectrum Labs with sensitivity factor downloaded and added to the cal file.

Below is the RTA of my room, does it looks normal to you? When I opened the SPL meter, it constantly read above 62dbs with just the fans of my projector and the Inuke running.

If you are sending the REW test signal to HDMI1 and/or HDMI2 and the front speakers are set to Large, you should not be getting a signal from the subs. Run the sweep again and feel the sub's cone--is it indeed moving? As for the quality of the measurement, I suspect the new speakers are placed in a different spot than the HTIB speakers, which may account for what looks worse. Experiment with different speaker placements. And BTW, I would measure speakers + subs.

The strange noise coming from the speaker cannot have anything to do with the microphone--a mic doesn't generate any sound.

And finally, a typical noise level should be in the 40-50dB range. A reading above 60dB would be a pretty noisy room, IMO. Is there a reason to have the projector running while taking measurements? I am not familiar with the iNuke. Does it generate noise, like with cooling fans?

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post #14825 of 14826 Old Today, 05:08 PM
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Does it generate noise, like with cooling fans?
Indeed, the fans of the iNukes are (in)famous for noise. Threads about replacing the fans abound. But that still wouldn't get a room to 60dB.

Did you really need to quote that entire post in your reply?
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post #14826 of 14826 Old Today, 09:38 PM
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Is there a way in REW to plot the delta in FR between two different measures? For example, I can take measure 1 and measure 2 and it will plot the FR of both together. That's useful. But for one specific purpose I'm mot interested in seeing a graph of the delta. Like with 0 dB at the middle of the Y axis, and dBs increasing going up the Y axis and decreasing going down the Y axis, with the Hz along the X axis. And having the plot show me the difference between the two. So if at 50 Hz measure 1 was 4 dB more than measure 2, then at the X axis at 50 Hz the value plotted there would be 4 dB. Is this possible?

In case you are wondering, I am measuring the acoustical transparency and properties of different AT screens. I want to have a Baseline measure which is the speaker without any screen in front of it. Then do measures for each screen. Then to interpret the results, I don't care so much about what the actual absolute dB levels are, but rather what the delta is between that measure and the baseline measure, so I can most easily judge the affect of the screen on the measurement. The way I'd have to do this now is to eyeball the FR and put the cursor over places where they FR levels look wider and then read them "oh ok this is 75 db baseline vs 72 dB for screen one, so that's -3 dB at X Hz". That works but a much more intuitive view of the data would be a plot with the deltas.

Thanks!
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