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Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 155

post #4621 of 9584
Quote:
Originally Posted by AustinJerry View Post

All the cables look pristine.  While you are correct, simply disconnecting and re-connecting cables can clear up issues, time will tell if that is the root cause this time.  I have to admit, I have never seen a loose or defective cable cause an 8-10dB loss in output, but I guess it could happen.  In the meantime, I think it would be wise to run with the consumer calibration for several days to see if the problem returns.  A Pro calibration takes long enough to complete that I am not anxious to have to discard another one.

Wow...you mantaining a consumer cal and Keith using OmniMic temporarily because a friend borrowed his REW mic--what's the world coming to? eek.gif

If it's any consolation, I once spent several hours last year trying to ID why a series of mains+sub plots looked so awful post-Audyssey compared to previous runs. Turned out one of our white fluffy dogs stepped on a cable and inadvertedly unplugged a subwoofer.

Fortunately we have a ways to go before our newborn gets that adventurous LOL...

Gear mentioned in this thread:

post #4622 of 9584
Quote:
Originally Posted by shpitz View Post

Here's the $1M question:

I got an UMIK-1 with HDMI, how do I compare my existing surround speaker with the new Pioneer SB21 I just bought @ Walmart?

I'd like to play audio through WinAmp and place the microphone near the speaker, maybe 6" away. How can I play and measure @ the same time? How would you guys tackle this?

Thanks!

Loudspeaker measurement is difficult to do inside. You can minimize room interaction by measuring at approx 1meter on axis with the tweeter. However the FR will be unrepresentative below the baffle step where the speaker goes omni. You can also "gate" your measurements by adjusting the time window to cut out the room reflections but this reduces bass resolution.

A better way is measure outside as far away from any boundaries as possible while elevating the speaker as high as possible micd at 1meter. However you will still have ground bounce which will show up in the 100-400Hz region.

Another way is to lay speaker on its back outside away from boundaries micd at one meter. However this measures the speaker in approx 2pi space which boosts the midbass un-naturally if not installed in this manner.

For true measurements, you should measure the speaker groundplane up to the baffle step frequency and as 4pi as possible above the baffle step frequency. Then splice the measurements together or overlay them. AFAIK, This is the most correct way to represent the true speaker FR that folks like us can do.......
post #4623 of 9584
Of course, the final measure of quality is how a speaker sounds in the room with the speaker at its desired location and heard from the primary listening position. In other words, however else you measure them, you should also measure the speakers with the microphone at the primary listening position and the speakers mounted appropriately.
post #4624 of 9584
Quote:
Originally Posted by AustinJerry View Post
 

All the cables look pristine.  While you are correct, simply disconnecting and re-connecting cables can clear up issues, time will tell if that is the root cause this time.  I have to admit, I have never seen a loose or defective cable cause an 8-10dB loss in output, but I guess it could happen.  In the meantime, I think it would be wise to run with the consumer calibration for several days to see if the problem returns.  A Pro calibration takes long enough to complete that I am not anxious to have to discard another one.

 

I actually received a clue during the Pro calibration that something was wrong.  When the first sweep sent the chirp to the center channel, it had to increase the level and re-measure.  At the time, I thought it was perhaps because the speaker was in a slightly different position and didn't pay much attention.  Subsequent chirps sounded normal, of course, because the level had been raised.  The resulting trim of -8 was a real surprise.

 

Agreed that 10dB loss of SPL is weird for a cable connection issue. Do you have to run Audyssey to check the centre channel is behaving - won't a simple SPL meter reading using AVR internal tones be good enough?

 

I assume you have done a 'wiggle test' on the XPA-3 speaker connectors, input connectors and so on?

post #4625 of 9584
Quote:
Originally Posted by AV_mike View Post
 
Quote:
Originally Posted by AustinJerry View Post

All the cables look pristine.  While you are correct, simply disconnecting and re-connecting cables can clear up issues, time will tell if that is the root cause this time.  I have to admit, I have never seen a loose or defective cable cause an 8-10dB loss in output, but I guess it could happen.  In the meantime, I think it would be wise to run with the consumer calibration for several days to see if the problem returns.  A Pro calibration takes long enough to complete that I am not anxious to have to discard another one.

I actually received a clue during the Pro calibration that something was wrong.  When the first sweep sent the chirp to the center channel, it had to increase the level and re-measure.  At the time, I thought it was perhaps because the speaker was in a slightly different position and didn't pay much attention.  Subsequent chirps sounded normal, of course, because the level had been raised.  The resulting trim of -8 was a real surprise.

You may also have an intermittent/poor connection within either the Speaker or the Emo.
With the test tones playing from the centre, try to move the binding posts at each end - any variation in tone volume could indicate the root cause - also double check the pre-out to Emo in leads in the same way.
Regards, Mike.

 

Ah - the 'wiggle test' I just proposed. You beat me to it :)

post #4626 of 9584
Quote:
Originally Posted by sdrucker View Post
 
Quote:
Originally Posted by AustinJerry View Post

All the cables look pristine.  While you are correct, simply disconnecting and re-connecting cables can clear up issues, time will tell if that is the root cause this time.  I have to admit, I have never seen a loose or defective cable cause an 8-10dB loss in output, but I guess it could happen.  In the meantime, I think it would be wise to run with the consumer calibration for several days to see if the problem returns.  A Pro calibration takes long enough to complete that I am not anxious to have to discard another one.

Wow...you mantaining a consumer cal and Keith using OmniMic temporarily because a friend borrowed his REW mic--what's the world coming to? eek.gif

If it's any consolation, I once spent several hours last year trying to ID why a series of mains+sub plots looked so awful post-Audyssey compared to previous runs. Turned out one of our white fluffy dogs stepped on a cable and inadvertedly unplugged a subwoofer.

Fortunately we have a ways to go before our newborn gets that adventurous LOL...

:)  I get my REW mic back tomorrow!  I quite enjoyed the simplicity of OM. But not having a data file that one can go back to and manipulate in various ways is a PITA. If I want to look at anything different to what I recorded the other day with OM, I have to measure all over again.

post #4627 of 9584
Quote:
Originally Posted by sdrucker View Post

Wow...you mantaining a consumer cal and Keith using OmniMic temporarily because a friend borrowed his REW mic--what's the world coming to? eek.gif

Haha...this made me LOL, in public! Congrats on the new addition as well!
post #4628 of 9584
Quote:
Originally Posted by kbarnes701 View Post

smile.gif  I get my REW mic back tomorrow!  I quite enjoyed the simplicity of OM. But not having a data file that one can go back to and manipulate in various ways is a PITA. If I want to look at anything different to what I recorded the other day with OM, I have to measure all over again.

If you use the "Save IR as WAV" option in OM, you can import it into REW and then do whatever whenever you want to it. Best of both worlds IMO.
post #4629 of 9584
Quote:
Originally Posted by kbarnes701 View Post
 

 

Agreed that 10dB loss of SPL is weird for a cable connection issue. Do you have to run Audyssey to check the centre channel is behaving - won't a simple SPL meter reading using AVR internal tones be good enough?

 

I assume you have done a 'wiggle test' on the XPA-3 speaker connectors, input connectors and so on?

 

 

No, I don't have to run Audyssey.  As you say, using the internal test tones was sufficient.  Yesterday, when the center level was low, I didn't even need the SPL--it was obvious enough by ear that the level was significantly off.  Anyway, it's back to normal now, but I am still a bit uneasy that the problem could re-occur.

post #4630 of 9584
Quote:
Originally Posted by djbluemax1 View Post

Did you say you took the measurements from 6" (6 INCHES) away from the speaker? That's not correct.

Thanks for the thorough response!

I did measure both speakers from the same exact distance to the mic. A better measurement would be from the MLP and not near-field (which is what i've done)?
post #4631 of 9584
Quote:
Originally Posted by AustinJerry View Post
 
Quote:
Originally Posted by kbarnes701 View Post
 

 

Agreed that 10dB loss of SPL is weird for a cable connection issue. Do you have to run Audyssey to check the centre channel is behaving - won't a simple SPL meter reading using AVR internal tones be good enough?

 

I assume you have done a 'wiggle test' on the XPA-3 speaker connectors, input connectors and so on?

 

 

No, I don't have to run Audyssey.  As you say, using the internal test tones was sufficient.  Yesterday, when the center level was low, I didn't even need the SPL--it was obvious enough by ear that the level was significantly off.  Anyway, it's back to normal now, but I am still a bit uneasy that the problem could re-occur.

 

Yes, IKWYM. 

 

I’d be uneasy too. It would take me some time to have full confidence that things were working properly, but hopefully this is the case. The other thing that always makes me uneasy is when things 'fix themselves'.  If only...

post #4632 of 9584
Quote:
Originally Posted by jim19611961 View Post
 
Quote:
Originally Posted by kbarnes701 View Post

smile.gif  I get my REW mic back tomorrow!  I quite enjoyed the simplicity of OM. But not having a data file that one can go back to and manipulate in various ways is a PITA. If I want to look at anything different to what I recorded the other day with OM, I have to measure all over again.

If you use the "Save IR as WAV" option in OM, you can import it into REW and then do whatever whenever you want to it. Best of both worlds IMO.

 

Wow - I didn't know that. Thanks - I will try it.

post #4633 of 9584
Quote:
Originally Posted by shpitz View Post

Quote:
Originally Posted by djbluemax1 View Post

Did you say you took the measurements from 6" (6 INCHES) away from the speaker? That's not correct.

Thanks for the thorough response!

I did measure both speakers from the same exact distance to the mic. A better measurement would be from the MLP and not near-field (which is what i've done)?

the further you move the mic away from the speaker, the more garbage(reflections) you will see in the measurement.

It depends on what your goals are: There are many different ways to measure and they are all correct for different goals and what data your actually looking for.

- If your evaluating the speakers FR alone, you need to measure in a way that takes the room out of the equation.

- If your evaluating what works best in a particular room/setup then you should measure in installed in place at the LP.

6" is probably not far enough for the tweeter and woofer wave fronts to completely integrate. Thats why most folks use 1-2meters or 3-6ft. However this long of a distance introduces measurement anomalies when taking a measurement inside in the midbass/midrange as I previously mentioned.

A Measurement from 1M is good down to about 500Hz in most rooms without any significant measurement impact...... Below 500Hz you'll be seeing lots of comb filtering from reflected energy.
post #4634 of 9584
Thanks NicksHitachi!
post #4635 of 9584
Quote:
Originally Posted by J_P_A View Post

I'm not sure which Toslink think you are referring to. I've got a MacBook Pro, so my only option is a MiniDisplay port as an output. So I just went with a MiniDisplay to HDMI adapter.

I have an older MacBook Pro (Intel Core 2 Duo) that has a DVI output and other ports. The weird/neat thing about it is that the headphone jack is also a Toslink jack but you need an usual (but cheap) cable to convert to regular toslink.

I got one from radio shack for about $10 and plugged in both ends and it worked great for some stereo testing. I just used the built-in mic on the MacBook and got some neat graphs etc. Only problem, besides calibration, was that the 6ft Toslink cable didn't extend to the LP. But it was fun to get some result.

Now, to get a real mic.
post #4636 of 9584
Quote:
Originally Posted by artur9 View Post

I have an older MacBook Pro (Intel Core 2 Duo) that has a DVI output and other ports. The weird/neat thing about it is that the headphone jack is also a Toslink jack but you need an usual (but cheap) cable to convert to regular toslink.

I got one from radio shack for about $10 and plugged in both ends and it worked great for some stereo testing. I just used the built-in mic on the MacBook and got some neat graphs etc. Only problem, besides calibration, was that the 6ft Toslink cable didn't extend to the LP. But it was fun to get some result.

Now, to get a real mic.

Wow. I've never heard of that before. Did you use Soundflower to choose the output?
post #4637 of 9584
Quote:
Originally Posted by J_P_A View Post

Wow. I've never heard of that before. Did you use Soundflower to choose the output?

Not yet. That's my next step. I'm not sure the Toslink thing does multichannel. So I just tested in L+R+sub. It actually looked pretty good to my untrained eyes other than I was not getting the bass I expected and a big dip around 110Hz. But who knows what the Mac mic is capable of.

I'm going slowly because I am waiting to buy/afford a prepro that does per channel crossovers.
post #4638 of 9584
Quote:
Originally Posted by artur9 View Post

Not yet. That's my next step. I'm not sure the Toslink thing does multichannel. So I just tested in L+R+sub. It actually looked pretty good to my untrained eyes other than I was not getting the bass I expected and a big dip around 110Hz. But who knows what the Mac mic is capable of.

I'm going slowly because I am waiting to buy/afford a prepro that does per channel crossovers.

Gotcha. My first thought was that output would only support 2 channel, but I looked at the cable you linked to and it claims multi-channel support. Not sure how many channels, but it will be interesting to find out.
post #4639 of 9584
The number of channels will depend on what the Mac supports: lossless stereo PCM or lossy up to 5.1 Dolby Digital or DTS.
post #4640 of 9584
Quote:
Originally Posted by jim19611961 View Post

If you use the "Save IR as WAV" option in OM, you can import it into REW and then do whatever whenever you want to it. Best of both worlds IMO.

I have been using REW that way since after buying OM, I could not find the information or help I was looking for in the OM thread. I generate WAV files in OM, then play with them in REW. I have compared FR charts generated with both programs, and found them to be identical. I only use OM to generate the wav files and when I need real time analysis. Has anybody noticed any difference between FR generated that way?

Stef
post #4641 of 9584
Quote:
Originally Posted by stef2 View Post

I have been using REW that way since after buying OM, I could not find the information or help I was looking for in the OM thread. I generate WAV files in OM, then play with them in REW. I have compared FR charts generated with both programs, and found them to be identical. I only use OM to generate the wav files and when I need real time analysis. Has anybody noticed any difference between FR generated that way?

Stef

I haven't compared FR closely, but when comparing ETC results, REW seems to always show the peaks 2-3db lower than OM does.
post #4642 of 9584
Quote:
Originally Posted by jim19611961 View Post
 
Quote:
Originally Posted by stef2 View Post

I have been using REW that way since after buying OM, I could not find the information or help I was looking for in the OM thread. I generate WAV files in OM, then play with them in REW. I have compared FR charts generated with both programs, and found them to be identical. I only use OM to generate the wav files and when I need real time analysis. Has anybody noticed any difference between FR generated that way?

Stef

I haven't compared FR closely, but when comparing ETC results, REW seems to always show the peaks 2-3db lower than OM does.

 

Any idea why that would be the case, Jim?

post #4643 of 9584
hello, first of all thank you all for this great thread, it is very helpful to me.

recently i was trying to optimize speaker placement and was doing some basic/sanity checks.
measured FL only, FR only and both at the same time.
i discovered one thing which is bothering me. look at the LR measurement.

when i have FR speaker wired in phase (red to red, black to black) the two speakers cancel each other in 50-100hz range.
in this range spl for both speakers is lower than each separate speaker.

when i have FR speaker wired out of phase they look ok.
what does this tell me? did someone swap wires at the factory?
should i wire them out of phase? or can this be room influence?
can i verify the wiring somehow?

all those measurements are without audyssey. sub off, fronts large.

normal phase in FR:


reversed phase in FR:
post #4644 of 9584
What's a good resource for a noob to get up to speed on ETC? I've read some of the things mentioned here and the ETCs posted just look like a bunch of spiky lines to me.
post #4645 of 9584
Quote:
Originally Posted by ciukacz View Post

when i have FR speaker wired out of phase they look ok.
what does this tell me? did someone swap wires at the factory?
should i wire them out of phase? or can this be room influence?
can i verify the wiring somehow


 

 

You can verify the wiring polarity like this: disconnect the speakers from the amp. Get a small 9V battery and connect the + and - of the battery to the + and - of the speaker. The speaker driver will move slightly - if it moves out, then check the other speaker the same way. Both speaker drivers should move the same way when connected to the battery.

 
To check phase, disconnect or otherwise disable all the speakers with the exception of the L and R. Play a mono signal through the speakers - human voice is good. If the image is bang in the centre of the two speakers, they are in phase. If OTOH the image sounds 'diffuse' and 'all over the room', the speakers are out of phase.
 
Please advise the make and model of your speakers.
post #4646 of 9584
This is a good reference in general that a forum member pointed me to recently; section B discusses ETC. This was written for two-channel setup, but I believe Nyal has mentioned in the past that it applies to multi-channel as well, with the exception being more stringent bass requirements. Don't quote me on that, though.
post #4647 of 9584
Quote:
Originally Posted by artur9 View Post

What's a good resource for a noob to get up to speed on ETC? I've read some of the things mentioned here and the ETCs posted just look like a bunch of spiky lines to me.

 

Have you read AustinJerry's Guide?  It's linked in his sig.  The Guide gives you a brief overview of what to look for in the ETC graphs and how to ensure you are set up correctly in REW when you make and view the graphs.

post #4648 of 9584
Quote:
Originally Posted by kbarnes701 View Post

Any idea why that would be the case, Jim?

No.

I haven't really looked into it because for me, the difference is not that significant. Whether a peak is -28db or -30db isnt a game changer.

I will do a new comparison and post the results sometime soon just for grins.
Edited by jim19611961 - 9/17/13 at 7:05am
post #4649 of 9584
Quote:
Originally Posted by kbarnes701 View Post

You can verify the wiring polarity like this: disconnect the speakers from the amp. Get a small 9V battery and connect the + and - of the battery to the + and - of the speaker. The speaker driver will move slightly - if it moves out, then check the other speaker the same way. Both speaker drivers should move the same way when connected to the battery.
 
To check phase, disconnect or otherwise disable all the speakers with the exception of the L and R. Play a mono signal through the speakers - human voice is good. If the image is bang in the centre of the two speakers, they are in phase. If OTOH the image sounds 'diffuse' and 'all over the room', the speakers are out of phase.
 
Please advise the make and model of your speakers.

thank you for the suggestions, will try them out when i can.
my speakers are Indiana Line Nota 550, i think this is a 2.5-way construction.
could it be that just one woofer is mis-wired internally to crossover board?
post #4650 of 9584
Quote:
Originally Posted by artur9 View Post

What's a good resource for a noob to get up to speed on ETC? I've read some of the things mentioned here and the ETCs posted just look like a bunch of spiky lines to me.

I think you should read the several sources mentioned already, as well as the REW Help screens on ETC, and then come back with specific questions, and perhaps some postings of your ETC measurements. This will allow us to provide specific guidance.

At spectral frequencies (above approximately 500 Hz), your audio is influenced by reflections coming from hard surfaces in your listening room. The Impulse measurements in REW can help you identify the magnitude and timing of these reflections. We can assist you in several methods to identify the sources of the reflections, and suggest ways to treat and reduce/remove them. Reducing unwanted room reflections is as important as taming bass resonances. However, managing these two issues involves different approaches, measurements, and solutions.
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AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs