Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 490 - AVS Forum | Home Theater Discussions And Reviews
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post #14671 of 15543 Old 05-12-2015, 10:37 PM
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Quote:
Originally Posted by lovingdvd View Post
Is it possible to use REW to create a polar frequency response, like the one posted below which shows an off-axis frequency response (I don't think that software is REW):

Not directly no. You can use REW to measure then use the feature added in 5.11 to save all measurements to text at once then use the script i wrote to generate the graph - https://github.com/3ll3d00d/directivity-utils

The software shown is omnimic I believe. Apparently you can load data into it without buying it though.
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post #14672 of 15543 Old 05-13-2015, 06:43 PM
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something is wrong there, there's no way a normally functioning HT system will produce <0.1V given a digital full scale 60Hz sine wave and all trims/volume at 0
@3ll3d00d

True to occam's razor I suspect the problem lies with me. I could use some help determining where I've gone wrong.

Following the guide, with the black lead in COM and red in V, I set my multimeter to AC (The V with the wavy line) and my current reading was 0.8 (with AVR trim +12). However reversing which lead was contacting the pin and the shield resulted in that number jumping to 24, instead of what the guide indicated it would likely be, -0.8. This made me believe my settings were incorrect.

I then, as a lark, switched to DC (V with a straight solid and dotted line) and got a reading of 12. Reversing the leads showed -12.

Using this method--with DC--my receiver outputs 0.9V at an AVR trim level of 3.5.

Soooooo...where is the error? Should the guide say DC instead of AC? Is my understanding of direct=straight line, alternating=wavy line flipped on its head? Are BOTH of my cheapo multimeters manufactured such that AC and DC are actually reversed? Gremlins? Could it be gremlins? 'Cause right about now I'd believe just about any explanation offered.

...

help?

Last edited by HDgaming42; 05-13-2015 at 07:24 PM.
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post #14673 of 15543 Old 05-13-2015, 08:49 PM
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Quote:
Originally Posted by 3ll3d00d View Post
Not directly no. You can use REW to measure then use the feature added in 5.11 to save all measurements to text at once then use the script i wrote to generate the graph - https://github.com/3ll3d00d/directivity-utils

The software shown is omnimic I believe. Apparently you can load data into it without buying it though.
Thanks. Do you think this feature may be worthwhile for John to consider adding to REW?
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post #14674 of 15543 Old 05-13-2015, 09:08 PM
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Quote:
Originally Posted by HDgaming42 View Post

True to occam's razor I suspect the problem lies with me. I could use some help determining where I've gone wrong.

Following the guide, with the black lead in COM and red in V, I set my multimeter to AC (The V with the wavy line) and my current reading was 0.8 (with AVR trim +12). However reversing which lead was contacting the pin and the shield resulted in that number jumping to 24, instead of what the guide indicated it would likely be, -0.8. This made me believe my settings were incorrect.

I then, as a lark, switched to DC (V with a straight solid and dotted line) and got a reading of 12. Reversing the leads showed -12.

Using this method--with DC--my receiver outputs 0.9V at an AVR trim level of 3.5.

Soooooo...where is the error? Should the guide say DC instead of AC? Is my understanding of direct=straight line, alternating=wavy line flipped on its head? Are BOTH of my cheapo multimeters manufactured such that AC and DC are actually reversed? Gremlins? Could it be gremlins? 'Cause right about now I'd believe just about any explanation offered.

...

help?
I don't recall a section in the Guide that covers reading voltages. What guide are you following?

You definitely want the DMM set to read AC voltage. Your first reading looks reasonable, but you shouldn't get a completely different reading by simply reversing the leads. Certainly not a jump from .8V to 24V (which would fry your electronics). Perhaps you meant 2.4V, but you still should be getting -.8V with the leads reversed. Perhaps the leads are not making good contact with the signal cable?
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post #14675 of 15543 Old 05-13-2015, 09:32 PM
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Quote:
Originally Posted by AustinJerry View Post
I don't recall a section in the Guide that covers reading voltages. What guide are you following?

You definitely want the DMM set to read AC voltage. Your first reading looks reasonable, but you shouldn't get a completely different reading by simply reversing the leads. Certainly not a jump from .8V to 24V (which would fry your electronics). Perhaps you meant 2.4V, but you still should be getting -.8V with the leads reversed. Perhaps the leads are not making good contact with the signal cable?
When time permits it would be great to see a section of the guide cover how to measure the voltages and understanding what it means, and as it relates to the dip switches and when its appropriate to change the dips and what it means for balanced/unbalanced connection choices.
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post #14676 of 15543 Old 05-13-2015, 09:37 PM
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Quote:
Originally Posted by lovingdvd View Post
Thanks. Do you think this feature may be worthwhile for John to consider adding to REW?
He already is:

http://www.hometheatershack.com/foru...nse-plots.html

My Home Theater/Video Gaming/HTPC/2 Channel rig (Mitsubishi, MartinLogan, Marantz, DIYMA, and others)

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post #14677 of 15543 Old 05-13-2015, 10:25 PM
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Quote:
Originally Posted by AustinJerry View Post
I don't recall a section in the Guide that covers reading voltages. What guide are you following?

You definitely want the DMM set to read AC voltage. Your first reading looks reasonable, but you shouldn't get a completely different reading by simply reversing the leads. Certainly not a jump from .8V to 24V (which would fry your electronics). Perhaps you meant 2.4V, but you still should be getting -.8V with the leads reversed. Perhaps the leads are not making good contact with the signal cable?
I just realized I'm probably posting in the wrong thread. I'm referring to your guide to time align two subs with a miniDSP.

(which would fry your electronics)

Oh I don't like the sound of that one bit. Not one bit. It was most certainly reading 24V, not 2.4V. It was making good contact. I tried reversing them again and again as it made no sense, and frankly scared me. Should turning up the gain on an AVR enable a voltage of 24V?! Or do I have the world's worst hand-me-down multimeter?

I'd think the first number (0.8V) must be accurate, as my miniDSP still functions...it would have taken the brunt of it, as I only swapped it out later to connect the sub directly.

Ignoring for a moment that the readings *should* be a mirror of one another (postive/negative), the correct procedure is to put red on the tip, and black on the sleeve? Sadly at this point I don't recall which order gave me the 24V reading...I'll have to verify.
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post #14678 of 15543 Old 05-14-2015, 01:38 AM
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Your avr won't be putting out 24V unless you were measuring the speaker output not the pre out. My guess is your dmm is dodgy.
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post #14679 of 15543 Old 05-14-2015, 05:41 AM
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Quote:
Originally Posted by lovingdvd View Post
When time permits it would be great to see a section of the guide cover how to measure the voltages and understanding what it means, and as it relates to the dip switches and when its appropriate to change the dips and what it means for balanced/unbalanced connection choices.
Thanks for the feedback. As HDGaming mentioned, there is a section pertaining to voltage measurements in the guide for implementing the 2x4, linked in my sig. I am not sure a discussion of voltages belongs in a REW guide.
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post #14680 of 15543 Old 05-14-2015, 05:59 AM
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Just received my MiniDSP UMIK-1 at work here. Fun starts this evening now Have read through quite a bit of this thread, skipped a bit and read some more. Quite a bit to take in!
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post #14681 of 15543 Old 05-14-2015, 06:02 AM
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Just received my MiniDSP UMIK-1 at work here. Fun starts this evening now Have read through quite a bit of this thread, skipped a bit and read some more. Quite a bit to take in!
Did you read through the guide?
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post #14682 of 15543 Old 05-14-2015, 06:06 AM
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Did you read through the guide?
The REW 101 Guide? Yeah, although I'll be reading through it again now that I have the mic to work with. I have the software installed and tested out with HDMI. Information in the guide and on here is fanstastic.
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post #14683 of 15543 Old 05-14-2015, 05:55 PM
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The REW 101 Guide? Yeah, although I'll be reading through it again now that I have the mic to work with. I have the software installed and tested out with HDMI. Information in the guide and on here is fanstastic.
Well, the payoff for us is the voyeuristic pleasure of seeing your equipment and graphs. Please don't let us down.

And don't forget to follow the graph posting guidelines.
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post #14684 of 15543 Old 05-14-2015, 06:13 PM
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Quote:
Originally Posted by AustinJerry View Post
You definitely want the DMM set to read AC voltage. Your first reading looks reasonable, but you shouldn't get a completely different reading by simply reversing the leads. Certainly not a jump from .8V to 24V (which would fry your electronics).
Quote:
Originally Posted by 3ll3d00d View Post
Your avr won't be putting out 24V unless you were measuring the speaker output not the pre out. My guess is your dmm is dodgy.
Yes...and no? So that DMM was crap--figured I'd put fresh batteries in it and the battery terminals snapped off. Didn't feel like breaking out my soldering iron, so instead dug out an old MM I'd long since retired. Tested it in AC in a wall socket (Canada). Red to Hot and black to Ground read 0.1. Red to Hot and Black to Neutral read 122. Reversing them also read 122, with no negative symbol (not sure if that's expected?). Red to Neutral and Black to Ground also read 122.

Was the above an appropriate test of this MM? It is a Sperry DM-350A. I've included a web-pic of it.



The picture shows red going into COM; I did black to COM and red to V
, though I suspect if you take the readings both ways you have enough data to suss out what's what.

So on to the insanity, and I'm hoping someone can help. I ran two tests.

Test 01

1. REW out via HDMI into Onkyo.
2. Using ASIO4ALL, generate 60Hz test tone, -3dBFS direct to Channel 4 (sub)
3. AVR sub trim set to 0
4. AVR volume began at -20, and was increased by 1dB increments
5. RCA cable hooked to Onkyo sub pre-out. Other end disconnected from subwoofer and measured.
6. Measurements were taken with both the red lead touching the tip while black touched the sleeve, and the reverse
7. Measurements were slow, and took care to ensure a proper connection with stable voltage recorded

Behold



Test 02

1. REW out via HDMI into Onkyo.
2. Using ASIO4ALL, generate 60Hz test tone, -3dBFS direct to Channel 4 (sub)
3. AVR sub trim set to 0, and decreased by 1dB each measurement
4. AVR volume set to 0
5. RCA cable hooked to Onkyo sub pre-out. Other end disconnected from subwoofer and measured.
6. Measurements were taken with both the red lead touching the tip while black touched the sleeve, and the reverse
7. Measurements were slow, and took care to ensure a proper connection with stable voltage recorded

Essentially exactly the same as lowering the MV. I skipped ahead to what I felt was the theoretical "sweetspot".



It seems that higher than -13.5dB - whether as a MV while sub trim=0, or a sub trim while at MV=0, things go off the rails.

The whole reason I've gone down this rabbit hole is because my system suddenly lost most of its "oomph". Turned out my good sub wasn't operating at all. Reset my Onkyo, reset my miniDSP and that didn't bring it back (making sure to enable the sub, and set its LPF to 120Hz). I removed the miniDSP and still no sub. Actually it worked briefly at +12 sub trim and MV=0, and at the sub's lowest input sensitivity. Briefly. No boom or pop or snap. It just stopped.

Phew. That was a lot of explaining. And measuring. Hopefully it's enough to go on to help me? To throw some theories out there?

Questions; from the ground up.

1. Does it appear my DMM is functioning correctly? What else could I do to verify this?
2. Do I appear to be using it correctly? Black to COM, Red to V. Measuring AC, on the 200 setting.
3. Do you feel the voltage readings are accurate?
4. If so, is this normal AVR behaviour, or it is faulty?
5. Is this behaviour concerning or potentially damaging?
6. Would I be safe to use at sub trim = -13.5dB (0.9V)?

Thanks so much for the help!
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post #14685 of 15543 Old 05-14-2015, 07:56 PM
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Hey guys, a little help!

I got my sub set up in a decent spot I think. I ran some measurements using different MCACC settings and in Pure Direct.

Pure Direct gave me a good looking response from what I can tell. With MCACC my measurements got worst. I'm using a Pioneer SC-1522k and the measurement is using the All Channel's Adjust gave me best results from the others.

Any insight on this? Anyone know if I can run MCACC to apply to speakers only and not the sub or correct any of the MCACC options?

Many thanks.

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post #14686 of 15543 Old 05-14-2015, 08:36 PM
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Something is amiss there. When measuring AC the meter lead polarity should not effect the readings. I would use the ohm function, disconnect your RCA cable and test it for continuity or a short or just replace it with a known good cable.

Sent from my SM-P900 using Tapatalk
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post #14687 of 15543 Old 05-14-2015, 10:55 PM
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FWIW 6dB is 2x the voltage, 3dB is ~1.4x. Your results are nowhere near that and 12V at 0 seems extremely high. I still wouldn't trust those results but have no idea what is wrong tbh.
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post #14688 of 15543 Old 05-15-2015, 12:10 AM
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Quote:
Originally Posted by artur9 View Post
Well, the payoff for us is the voyeuristic pleasure of seeing your equipment and graphs. Please don't let us down.

And don't forget to follow the graph posting guidelines.
Got it running last night but only had time for a quick test. Had a few issues getting the mic sorted. The UMIK is stuck on 32bit 48khz and the option to change is disabled. So not sure if this will cause a problem yet. I'll get some testing done this evening. At the moment I have no panels or anything on the walls and have 2 radiators! So will be interesting to see.

Backgroung on the room/equipment : With regards to the room layout I have a build thread on another site (Here). My current setup is an Onkyo-607, Monitor Audio Radius HD speakers (4xR90HD, 1x225HD, 1x R370HD). I am upgrading my receiver but have decided to wait until next year for the Atmos/DTS:X receivers. Also moving up to 7.1 shortly, thinking on bipole speakers. Of course this would mean doing all this wonderful calibration again Then in the future the plan is in ceiling speakers at some point for the new audio formats.

Room layout attached, its a slanted ceiling. The black squares are the current speakers, blue is where the new speakers will go and red is where the current surround (black) speakers will be moved to for 7.1. (Subject to change!)

Hopefully I might have a few graphs for you later
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post #14689 of 15543 Old 05-15-2015, 05:17 AM
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Originally Posted by glugus2000 View Post
Something is amiss there. When measuring AC the meter lead polarity should not effect the readings. I would use the ohm function, disconnect your RCA cable and test it for continuity or a short or just replace it with a known good cable.
Quote:
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FWIW 6dB is 2x the voltage, 3dB is ~1.4x. Your results are nowhere near that and 12V at 0 seems extremely high. I still wouldn't trust those results but have no idea what is wrong tbh.
I'll try another cable, but I'm at a loss as to how I could be doing this incorrectly. Or how I could get identical erroneous results from two different DMMs...
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post #14690 of 15543 Old 05-15-2015, 07:09 AM
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Originally Posted by jubei951 View Post
Hey guys, a little help!

I got my sub set up in a decent spot I think. I ran some measurements using different MCACC settings and in Pure Direct.

Pure Direct gave me a good looking response from what I can tell. With MCACC my measurements got worst. I'm using a Pioneer SC-1522k and the measurement is using the All Channel's Adjust gave me best results from the others.

Any insight on this? Anyone know if I can run MCACC to apply to speakers only and not the sub or correct any of the MCACC options?

Many thanks.

Guys - what can generally be done to handle a situation like the dip at 60 Hz he has? I know you cannot boost 60 Hz by 10 dB... If this a situation where either moving the sub is recommended, or adding a second sub? Can he use cuts to lower everything below 60 Hz by about 10 dB (doesn't seem like a good idea)? And the void at 100 Hz, that is likely the way the room is and sub relocation may be the only solution for that, if he is concerned with it?

jubei - Can you describe your room dimensions, layout, position of the sub, position of your seat, and what if any room treatments you have? You may also want to post a waterfall - that would be handy so we can see your decay time.
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post #14691 of 15543 Old 05-15-2015, 08:50 AM
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Quote:
Originally Posted by jubei951 View Post
Hey guys, a little help!

I got my sub set up in a decent spot I think. I ran some measurements using different MCACC settings and in Pure Direct.

Pure Direct gave me a good looking response from what I can tell. With MCACC my measurements got worst. I'm using a Pioneer SC-1522k and the measurement is using the All Channel's Adjust gave me best results from the others.

Any insight on this? Anyone know if I can run MCACC to apply to speakers only and not the sub or correct any of the MCACC options?

Many thanks.

Please repost with the proper settings (5db steps on the vertical).



Quote:
Originally Posted by lovingdvd View Post
Guys - what can generally be done to handle a situation like the dip at 60 Hz he has? I know you cannot boost 60 Hz by 10 dB... If this a situation where either moving the sub is recommended, or adding a second sub? Can he use cuts to lower everything below 60 Hz by about 10 dB (doesn't seem like a good idea)? And the void at 100 Hz, that is likely the way the room is and sub relocation may be the only solution for that, if he is concerned with it?

jubei - Can you describe your room dimensions, layout, position of the sub, position of your seat, and what if any room treatments you have? You may also want to post a waterfall - that would be handy so we can see your decay time.
Yup, he needs to move the sub around more and see if he can get a flatter response...if not, it's time for more subs.
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post #14692 of 15543 Old 05-15-2015, 11:38 AM
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Quick question and I'm sorry if I've missed the answer somewhere! It mentions measuring the L+C+R+SUB at the same time. How is this done? Cant REW only do 2 channels at most at a time

Last edited by Its Chris; 05-15-2015 at 01:52 PM.
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post #14693 of 15543 Old 05-15-2015, 12:18 PM
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Quick question and I'm sorry if I've missed the answer somewhere! It mentions measuring the L+C+R+SUB at the same time. How is this done? Cant REW only do 2 channels at most at a time?

Very rough first run : Link
I think you might have misread something. To measure bass performance, take two measurements: L+R+Subs, and C+Subs. The main speakers should be set to "small", of course, and you can experiment with different crossover settings, starting with 80Hz.
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post #14694 of 15543 Old 05-15-2015, 12:42 PM
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The speakers are set at small. Crossover at 80. I set all speaker settings back to 0 ( that audussey had changed) etc.

R+L+Sub is three channels though?

I've done all channels on their own, no sub. Then R, L and C each individually with sub.
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post #14695 of 15543 Old 05-15-2015, 01:00 PM
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The speakers are set at small. Crossover at 80. I set all speaker settings back to 0 ( that audussey had changed) etc.

R+L+Sub is three channels though?

I've done all channels on their own, no sub. Then R, L and C each individually with sub.
R+L is two channels. Bass below the crossover gets redirected to the subs by virtue of bass management when the speakers are set to small. So you are essentially measuring all the speakers that are outputting bass.
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post #14696 of 15543 Old 05-15-2015, 01:08 PM
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Ah ok. I had switched the sub off when testing all speakers individually. Makes sense. Ha! Oops...

Cheers!
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post #14697 of 15543 Old 05-15-2015, 01:50 PM
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Guys - what can generally be done to handle a situation like the dip at 60 Hz he has?
That could be a mode or destructive interference of some kind.

If it's a mode then the sub has to move so that the mode is somewhere else (i.e. not at the MLP).

If it's destructive interference then adjusting delays might fix some of it.
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post #14698 of 15543 Old 05-15-2015, 01:51 PM
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I've redone it. Actually got better headroom this time around. Had to restart everything. Havent got time at the minute to post up some screenshots, but if anyone is interested in the file its here : mdat file

Will post screenshots when I can. Cheers guys.
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post #14699 of 15543 Old 05-15-2015, 02:46 PM
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Hi guys finally got a umik-1 and REW up and running so this will be a first attempt and help is needed. This is for DXD12012's stacked in the right corner of the room from the mlp.
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post #14700 of 15543 Old 05-15-2015, 05:29 PM
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Quote:
Originally Posted by HDgaming42 View Post


So I spoke with an engineer at work about what I was seeing with my sub pre-out voltage-wise, and this is what he shared. I'd love for those more knowledgeable than myself to weigh in.

1. Without a proper reference to ground, not seeing polarity reverse isn't unusual when reversing the leads.
2. He sees two scenarios where reversing the leads would result in different readings
a. the multimeter contains a [can't remember the term--will add it later] which would essentially zero out much of the voltage when read in reverse
- this doesn't seem to be the case as reversed readings of an AC wall outlet show full voltage
b. the pre-out has a sizable DC offset; this could cause reverse readings to be reduced to under 1V.

He had to refresh his memory regarding RMS and DC offsets, but that's what he offered up. Anything there to go on? He didn't think the first column of data would be incorrect. Figured an oscilloscope would be helpful, but we no longer have one.

I tested the continuity of the cable--it checks out. Also tested a spare--same thing.

Now I'm looking in to how to read DC offset. I know that on speaker terminals if it exceeds 100mV you should be concerned, but I'm not sure what the range for pre-outs would be...

Last edited by HDgaming42; 05-15-2015 at 05:34 PM.
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