Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 783 - AVS Forum | Home Theater Discussions And Reviews
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post #23461 of 23472 Old 08-20-2017, 02:22 PM
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Quote:
Originally Posted by lonestarwings View Post
In the first 2 charts above - take 6khz. The mic calibration file for my Umik-1 at 6002.27 hz is +2.43 db.

On the ALL SPL the 6khz ALL SPL on the right (red) channel is 92.67 db. On the Distortion Fundamental plot, it is 95.10 at 6 khz, for a difference of 2.43.

Similairly, at 24.62hz, the All SPL on the right channl is 89.50. On the distortion fundamental it's 90.25, a difference of 0.75, and the cal file is +0.75 at 24.62hz. So it appears that the response on the distortion fundamental graph is being corrected by the values in the cal file while the ALL SPL window isn.t

I apologize if I'm misunderstanding something. Also, someone on another forum told me that the "SPL & Phase" and "All SPL" windows don't include the mic cal files, which is what alerted me to it initially.
From the REW help file on the Distortion Graph:

"The plots of the Fundamental (the linear part of the measurement) and the distortion harmonics do not include mic/meter or soundcard calibration corrections. This is to avoid the effect of the corrections generating a misleading view of distortion levels. For example, mic/meter and soundcard calibration corrections boost the lowest frequencies of measurements to counter the roll-off of the mic/meter and soundcard interfaces, but adding those corrections to a distortion plot would make distortion appear to rise at low frequencies, hence their omission"
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post #23462 of 23472 Old 08-20-2017, 03:57 PM
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Originally Posted by sam_adams View Post
From the REW help file on the Distortion Graph:

"The plots of the Fundamental (the linear part of the measurement) and the distortion harmonics do not include mic/meter or soundcard calibration corrections. This is to avoid the effect of the corrections generating a misleading view of distortion levels. For example, mic/meter and soundcard calibration corrections boost the lowest frequencies of measurements to counter the roll-off of the mic/meter and soundcard interfaces, but adding those corrections to a distortion plot would make distortion appear to rise at low frequencies, hence their omission"
Ok, so I guess I was misunderstanding the meaning of the +/- values of the calibration file. I guess a - would mean the mic reads low at that frequency and the corrective value needs to be added to the raw measurement, and a positive number means it reads high and the corrective value needs to be subtracted. Thanks for clarifying that for me!
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post #23463 of 23472 Old 08-20-2017, 04:39 PM
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Originally Posted by AustinJerry View Post
Well, the "All SPL" is a display window that shows existing measurements. When the measurements were originally taken, they were taken with the mic cal file in effect. Simply displaying a pre-existing measurement in the All SPL window doesn't remove the cal file adjustments. That would be weird, wouldn't it?

Using the UMIK-1 and REW to measure headphone output is somewhat unusual, and I don't claim to have ever tried it, or understand how it could be done.. Not sure whether the measurements you are getting are accurately capturing the frequency response of your headphones, which are very nice indeed.
Yeah, I definitely loaded the calibration file in beforehand. I was just misinterpreting the postive/negative values of the .cal file and operating on some questionable advice.

Here is the measurement rig. The coupling surface is creatology foam with graduation marks for placement repeatability, foam blocks for structure, and some polyfill on the surface immediately around the mic. A lot of people on superbestaudiofriends.org do this kind of thing and a few on head-fi.







It's not as far off from some pro measurements as I though it'd be. It seems pretty accurate until about 7 khz or so, compared to this pro measurement from Innerfidelity:
On my rig:


Same Headphone make/model pro measurement:
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post #23464 of 23472 Old 08-20-2017, 05:20 PM
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The reviews on your headphones are stellar. Very nice! I guess you must be a headphone kind of guy. That measurement rig is pretty creative.
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post #23465 of 23472 Old Today, 01:59 PM
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I'm having an issue with my Right tower speaker: when I play a measurement sweep above about 80 db or so, I get a weird doubling of the tone from about 1200-2000 hz. It sounds like a loud lower harmonic almost as loud as the fundamental. Also the Right mid in 1" nearfield measuremets plays about 3db lower volume than the left (all receiver EQ and level controls defeated), but nothing really showed up that much different between the two speakers in the 1 meter or 1" distortion plots.

The speakers use a 1.5" soft dome midrange.

I was wondering if this sound could be an indication of a damaged midrange? It sounds ok below 80db, but above that it's pretty noticeable, at least on the sweeps. I did a full battery of 1 meter and 1" measurements to try and diagnose, but I can't seem to recognize anything showing up. I even tried swapping the positions of the "good" and "bad" speaker (and the channels of the AVR they used) to see if it was room or AVR related, but it wasn't.

My speakers are still under warranty and they did a good job of repairing the broken tweeter in my center channel.

REW file of my troubleshooting measurments:
https://www.dropbox.com/s/p9xk7kmrpz...ting.mdat?dl=1

Some relevant screenshots:



The Left side, which sounds ok, for reference

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Nothing stands out in the measurements you posted. Am I missing something?

Why are you measuring at such high levels? Does the anomaly occur at lower measurement levels?
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post #23467 of 23472 Old Today, 03:26 PM
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Originally Posted by AustinJerry View Post
Nothing stands out in the measurements you posted. Am I missing something?

Why are you measuring at such high levels? Does the anomaly occur at lower measurement levels?
Thanks for looking! The levels are high on the nearfield stuff because the problem on the right mid-range really didn't show up until the volume was 85db at the main listening position, the measurement sweeps sound fine tonally at lower volumes, however the 3db difference is always there regardless (the 1" measurents I posted are as loud as I could get without clipping the mic), at -28 on a scale of +12 to -80. The avr tries to compensate by reducing level on the left by 2 db compared to the right.
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post #23468 of 23472 Old Today, 04:11 PM
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Quote:
Originally Posted by lonestarwings View Post
when I play a measurement sweep above about 80 db or so, I get a weird doubling of the tone from about 1200-2000 hz. It sounds like a loud lower harmonic almost as loud as the fundamental.

I was wondering if this sound could be an indication of a damaged midrange?
Rather than a sweep tone, use a fixed frequency sine wave. To do so, turn on REW's Generator tool. Select sine wave. Set the frequency near the problem area, say 1500 Hz. Set the volume low on the AVR, and activate the sine wave.

The tone should be free of distortion at low levels. If not, fix that first.

Gradually advance the loudness. At some point you will hear the added harmonics appear. Leave the volume so you can hear the distortion. Gently touch the cone of the midrange driver. If the harmonics stop or change, you have found the problem driver. If not, move your finger around the driver to see if you find anyplace that changes the sound. If nothing happens, try the tweeter. This is more delicate so be extra careful.

If you do confirm that slight diaphragmatic deformation induced by calibrated fingerwerkin alters the distortion, it means the driver is rubbing something, usually the voicecoil former vs the magnet. New driver is indicated. Been there, fixed that.
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Originally Posted by AV_mike View Post
I noticed that when viewing the REW file, both microphone and sound-card calibration files are shown as your UMIK serial number. Have you applied the Mic Cal file twice by any chance?
Normally only the Mic needs correcting, when using HDMI - no sound-card correction is required.
Regards, Mike.
Quote:
Originally Posted by AustinJerry View Post
If the cable is not seated pro[erly, you won't get any signal. It won't cause bad measurements, it will cause no measurements. Don't assume that this is influencing the measurements.

It is important that you answer Mike's question. When using a USB mic, there should be NO sound card calibration file in use. Having something in the sound card box could definitely skew the measurements.

I had a few minutes tonight to play around more. I removed the soundcard cal file and also used the 90deg cal file with the mic pointing to the ceiling this time around. Remeasures have been updated to https://drive.google.com/drive/folde...UE?usp=sharing All were taken without sound panels installed. Three measurements for each speaker: Audessey off, Audessey On without DEQ, Audessey On with DEQ on.


I believe the high end came up for all speakers with the new config but the left speaker only slightly increased and is still about 8dB down compared to the center and right speaker. I didn't dive into the waterfall plots or impulse responses with my limited time. Figured I'd start with the frequency response and go from there. Mic level was about 6-8 inches above the back of couch and pretty level with the tweeter height.


Any initial thoughts on the high frequency drop?
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post #23470 of 23472 Old Today, 06:49 PM
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Originally Posted by Roger Dressler View Post
Rather than a sweep tone, use a fixed frequency sine wave. To do so, turn on REW's Generator tool. Select sine wave. Set the frequency near the problem area, say 1500 Hz. Set the volume low on the AVR, and activate the sine wave.

The tone should be free of distortion at low levels. If not, fix that first.

Gradually advance the loudness. At some point you will hear the added harmonics appear. Leave the volume so you can hear the distortion. Gently touch the cone of the midrange driver. If the harmonics stop or change, you have found the problem driver. If not, move your finger around the driver to see if you find anyplace that changes the sound. If nothing happens, try the tweeter. This is more delicate so be extra careful.

If you do confirm that slight diaphragmatic deformation induced by calibrated fingerwerkin alters the distortion, it means the driver is rubbing something, usually the voicecoil former vs the magnet. New driver is indicated. Been there, fixed that.
Tried this, specifically the problem seems to start at about 1200 and end around 1950hz, pulsating a bit as it goes. It seems like the only speaker really doing anything at this frequency is the 1.5" dome midrange. When I try to touch it, it definitely changes the sound, it makes a a buzzing noise about like I'd expect. I tried it with a 1450hz constant frequency sine wave.

I need to have the receiver at volume -12 on a scale of +12/-80 before it becomes noticeable, and at -10 before it's really obvious, which equates to about 90db at the main listening position, much louder when I'm up there trying to touch it. I might just leave well enough alone and deal with it since I'm not 100% sure how bad the problem is and I don't know how often I'd be listening to something that loud out of the speakers.

WARNING - TURN YOUR SPEAKERS DOWN BEFORE YOU LISTEN TO THIS:

Here is an audio/video file of the good speaker playing a 1000-2000 hz sine sweep on a loop

And the bad one, the difference comes through pretty clear (starts at lower volume then I turn it up to make the problem audible):

Last edited by lonestarwings; Today at 07:26 PM.
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post #23471 of 23472 Old Today, 07:12 PM
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Quote:
Originally Posted by lonestarwings View Post
Tried this, specifically the problem seems to start at about 1200 and end around 1950hz, pulsating a bit as it goes. It seems like the only speaker really doing anything at this frequency is the 1.5" dome midrange. When I try to touch it, it definitely changes the sound, it makes a a buzzing noise about like I'd expect. I tried it with a 1450hz constant frequency sine wave.
Yup, sounds like a mechanical problem. What make/model are they? I'm guessing if there's a 1.5" driver in there it's the tweeter, and the midrange is the first below it, then a couple woofers.

Maybe if you sent the videos to the manufacturer they's ship you a new driver. Pretty simple to swap them out, usually.
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post #23472 of 23472 Old Today, 07:21 PM
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Originally Posted by Roger Dressler View Post
Yup, sounds like a mechanical problem. What make/model are they? I'm guessing if there's a 1.5" driver in there it's the tweeter, and the midrange is the first below it, then a couple woofers.

Maybe if you sent the videos to the manufacturer they's ship you a new driver. Pretty simple to swap them out, usually.
Yeah, it's a 1" tweeter, 1.5" dome mid below, then 3x 6.5".

It's these, Phase Technology 9.5: http://phasetech.mseaudio.com/series...ection/pc-9-5/

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