Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 19 - AVS Forum

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Audio Theory, Setup, and Chat

laugsbach's Avatar laugsbach
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Quote:
Originally Posted by mrfattbill View Post

So Larry, when are you going to come by and school me on the in's and out's of REW? smile.gif

Bill

Hey Bill, as soon as I remember everything I forgot about REW redface.gif...OM is so easy but I want to go deeper into measuring.
JChin's Avatar JChin
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If I can't get a flat or decent respond curve (by moving front speakers and/or sub), is it better to have more peaks than dips or more dips than peaks? Maybe my question is, whether its easier to handle peaks or easier to handle dips?
AustinJerry's Avatar AustinJerry
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^ I suspect it depends on where the peaks and valleys are. Have you published a response curve? Some dips are caused by room modes, and cannot be easily addressed by room EQ. I would think peaks could be addressed by a combination of treatments and EQ. However, if you only have one sub, then there is a lot of evidence that shows adding additional subs goes a long way to smooth out the bass response.

Please post some measurements.
jkasanic's Avatar jkasanic
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Now that the latest version of REW beta is compatible with OM, what "exactly" do I need to start taking measurements with a non-HDMI laptop and OM USB mic?  Latest beta version of REW + latest version of ASIO4ALL driver and I guess a splitter out of the laptop microphone jack and another Y cable for the mono portion of the Y coming out of the laptop going into the RCA jacks of my pre/pro input?  I suppose a single RCA cable would do if I only wanted to measure L+Sub, C+Sub or R+Sub but not a combination of any?  Sorry, I know this has been debated ad nauseum in the last 500 or so posts but I'm more of a picture guy and want to make sure I have everything hooked up correctly.


AustinJerry's Avatar AustinJerry
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Quote:
Originally Posted by jkasanic View Post

Now that the latest version of REW beta is compatible with OM, what "exactly" do I need to start taking measurements with a non-HDMI laptop and OM USB mic?  Latest beta version of REW + latest version of ASIO4ALL driver and I guess a splitter out of the laptop microphone jack and another Y cable for the mono portion of the Y coming out of the laptop going into the RCA jacks of my pre/pro input?  I suppose a single RCA cable would do if I only wanted to measure L+Sub, C+Sub or R+Sub but not a combination of any?  Sorry, I know this has been debated ad nauseum in the last 500 or so posts but I'm more of a picture guy and want to make sure I have everything hooked up correctly.

On the input side, you only need the OM microphone.

On the output side, you will use the stereo mini-jack on the laptop. You need a cable with a stereo mini-plug on one end, and dual RCA jacks on the other. REW will output a mono signal, so you need an RCA cable long enough to reach the AVR, and then a Y-cable to take the mono signal and connect it to the left and right AUX IN connections on the front of the AVR.

AFAIK, ASIO4ALL is only required if you are going to be using the HDMI connection to the AVR.
jkasanic's Avatar jkasanic
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Quote:
Originally Posted by AustinJerry View Post


On the input side, you only need the OM microphone.

On the output side, you will use the stereo mini-jack on the laptop. You need a cable with a stereo mini-plug on one end, and dual RCA jacks on the other. REW will output a mono signal, so you need an RCA cable long enough to reach the AVR, and then a Y-cable to take the mono signal and connect it to the left and right AUX IN connections on the front of the AVR.

AFAIK, ASIO4ALL is only required if you are going to be using the HDMI connection to the AVR.

 

So, by stereo mini-jack you mean the headphone output on the laptop (my laptop card only has a mic input and a headphone output).  So a cable like this with 3.5mm stereo to dual RCA (female in this case):

 

 

 

and then ideally a single to double male RCA cable (would a standard RCA work?).  The single to double RCA Y cable is what I'm struggling to find.  I guess I might need another adapter like this to plug the male side into the mono side of the previous adapter:

 

 

 

 

 

And then just a standard dual male RCA cable going from this adapter into the Aux inputs on the pre/pro?  If a single male RCA to dual male RCA cable exists that might simplify the connections but I couldn't find one doing a cursory online search.


AustinJerry's Avatar AustinJerry
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^ The stereo mini-plug to RCA cable you show should work.  Then you would run a male RCA to male RCA cable to the AVR.  However, the second cable you show would not work, because you want a single FEMALE RCA to a dual MALE RCA, since the AVR has female RCA plugs.


jkasanic's Avatar jkasanic
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Quote:
Originally Posted by AustinJerry View Post

^ The stereo mini-plug to RCA cable you show should work.  Then you would run a male RCA to male RCA cable to the AVR.  However, the second cable you show would not work, because you want a single FEMALE RCA to a dual MALE RCA, since the AVR has female RCA plugs.

Jerry, first off, thanks for taking the time to respond to my questions. Your efforts here and in other threads I follow is definitely above and beyond!

I'm having issues replyiing to multiple posts using my iPad but the point of the two separate adapters above was to alleviate an issue you actually mentioned quite a few posts back to batpig regarding the mono output of REW and the fact that an additional Y adapter would be necessary going into the pre/pro otherwise you would have to keep switching the red mono cable between L and R channels and measuring them together would not be possible. I was unable to find a single male RCA (for the mono output of REW) to dual male RCA connectors going into the Aux input on the pre/pro. Therefore, I proposed the male to dual female adapter so that a standard RCA dual male cable could be used from this adapter into the Aux input. Make sense now? I'll edit this post with a link to the previous post for reference.

EDIT: Ok, here's the relevant discussion:

 

Quote:
Originally Posted by batpig View Post

OK, so now we can route back to my original question which started this discussion:

Isn't the simple male>male 3.5mm to stereo RCA y-cable sufficient?




My understanding was that, with this cable, you plug into the left RCA AUX input to test the left front speaker, the right RCA AUX input to test the right front speaker, and BOTH of the AUX inputs (with PLII Cinema enabled) to test the center channel speaker. Is my understanding correct?

 

Quote:
Originally Posted by AustinJerry View Post


Not quite. If you use the cable above, only the right channel, I.e. the red cable, will carry a signal (recall that REW is a mono signal). So, you would plug the red cable into the right channel input on the AVR to measure the right channel, and move the red cable to the left input on the AVR to test the left channel. However, to test left+right, you need to plug the red cable into a Y-cable, and feed both the left and right AVR channels simultaneously. Setting the AVR to PLII Cinema will combine the left and right signals and output to the center channel.

Does this clear it up?

 

Quote:
Originally Posted by batpig View Post

Yes it does! Thank you!! smile.gif

Silly me, the reason it wasn't clicking was that I assumed the mono signal output would be dual-mono, not just isolated to one of the RCAs. Cheers!

 

 

This comment in between the above discussion is what confused me but perhaps that's because I haven't used REW before:

Quote:
Originally Posted by AV_mike View Post


Well I've been using the same cable for about a year, treating it as mono. REW input/output 1 is Left. With both RCA plugs connected (left & right), you use the Timing Ref Output to drive the "other" channel.
Regards, mike. (Sorry for lack of detail, sick in bed at present) - where's Jason when you need him?

JapanDave's Avatar JapanDave
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I still can't understand after all this how you would make a calibration file for the sound card if you did not use the USB mic?
AustinJerry's Avatar AustinJerry
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@ jkasanic,

 

A picture should clear it up:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


AustinJerry's Avatar AustinJerry
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Quote:
Originally Posted by JapanDave View Post

I still can't understand after all this how you would make a calibration file for the sound card if you did not use the USB mic?

 

I am not sure I understand your question.  Instructions for creating the soundcard calibration file are in the Guide (linked in my sig), Step 4, page 33.


JapanDave's Avatar JapanDave
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Quote:
Originally Posted by AustinJerry View Post

I am not sure I understand your question.  Instructions for creating the soundcard calibration file are in the Guide (linked in my sig), Step 4, page 33.
OK, so it is the same as before the HDMI output was added to REW. Thanks. Great guide BTW, I had not seen that yet.
JapanDave's Avatar JapanDave
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Quote:
Originally Posted by AustinJerry View Post

I am not sure I understand your question.  Instructions for creating the soundcard calibration file are in the Guide (linked in my sig), Step 4, page 33.
After reading through your guide a bit more, is it safe to assume that if your PC does not support 8 channels, that you will not be able to play back all 8 channels in REW, just the left and right speakers?
AustinJerry's Avatar AustinJerry
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Quote:
Originally Posted by JapanDave View Post

After reading through your guide a bit more, is it safe to assume that if your PC does not support 8 channels, that you will not be able to play back all 8 channels in REW, just the left and right speakers?

That is correct. However, when analyzing room response, the important speakers to use in the measurements are the left, right, and center speakers, as well as the subs. You do not need 8-channel support to test these speakers.
jkasanic's Avatar jkasanic
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Quote:
Originally Posted by AustinJerry View Post

@ jkasanic,

A picture should clear it up:

















Doh, male ends on 3.5mm adapter to a single female to two male Y adapter solves that issue with common cables! There's alway more than one way to skin a cat! Thanks!

Edit: is there any concern on cable lengths with this configuration (i.e. like not exceeding a 25ft extension with an Audyssey mic)?
JapanDave's Avatar JapanDave
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Quote:
Originally Posted by AustinJerry View Post

That is correct. However, when analyzing room response, the important speakers to use in the measurements are the left, right, and center speakers, as well as the subs. You do not need 8-channel support to test these speakers.
How do you test the center and sub if you only have stereo setup?
JD in NJ's Avatar JD in NJ
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Quote:
Originally Posted by JapanDave View Post

How do you test the center and sub if you only have stereo setup?

Is that a trick question?
kbarnes701's Avatar kbarnes701
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Quote:
Originally Posted by JChin View Post

If I can't get a flat or decent respond curve (by moving front speakers and/or sub), is it better to have more peaks than dips or more dips than peaks? Maybe my question is, whether its easier to handle peaks or easier to handle dips?

Electronic EQ such as Audyssey XT32 can deal most effectively with peaks (they shouldn’t be too bad if you have optimised setup prior to calibrating). But electronic EQ can't do anything at all for true nulls - treatments and/or more subs is the solution there, especially, IME, the latter.  Also, electronic EQ such as Audyssey is wary of trying to correct large dips because attempting to do so can use enormous amounts of amp power, for little or no solution. This has the potential to damage speakers, hence the limitation. So it is always easier, when attempting to level out the FR, to cut the peaks down to approach the dips, and then boost the entire spectrum in volume to get back to the original level as much as possible. Again, this is limited in electronic EQ systems, so treating the room, optimising speaker placement and adding more subs is always a more satisfactory solution. 


JapanDave's Avatar JapanDave
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Quote:
Originally Posted by JD in NJ View Post

Is that a trick question?
On my receiver, no it is not. Especially if you want to measure the in room response with EQ applied.

But, lucky for me ,my laptop has 8 channels, so I don't have to worry now.

My sub measurement with the HDMI.


Martycool007's Avatar Martycool007
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Ok, so I am confused. Is the mic from Minidsp all that is needed to do measurements in REW without having to buy an external sound card and mic pre-amp with phantom power? Are there any other usb mics that work with REW hooked up to a laptop that does not require an external sound card or mic pre-amp? If so, what are they, ie brands and models?

Last set of questions, Do these usb mics from the likes of Minidsp already come pre-callibrated? I already have a spare Behringer EM8000 that I have never used, could I send it to CSL and have it callibrated? If so, the only other things I would need would be a mic pre-amp, such as the Behringer Xenyx 502, and an external sound card, such as the...(need cheap suggestions)...


Oh and I almost forgot, what is the ASIO4ALL? Is this a sound card, or what?
AustinJerry's Avatar AustinJerry
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Quote:
Originally Posted by Martycool007 View Post

Ok, so I am confused. Is the mic from Minidsp all that is needed to do measurements in REW without having to buy an external sound card and mic pre-amp with phantom power? Are there any other usb mics that work with REW hooked up to a laptop that does not require an external sound card or mic pre-amp? If so, what are they, ie brands and models?

Last set of questions, Do these usb mics from the likes of Minidsp already come pre-callibrated? I already have a spare Behringer EM8000 that I have never used, could I send it to CSL and have it callibrated? If so, the only other things I would need would be a mic pre-amp, such as the Behringer Xenyx 502, and an external sound card, such as the...(need cheap suggestions)...


Oh and I almost forgot, what is the ASIO4ALL? Is this a sound card, or what?

 

You will not need an external sound card with a USB mic, and according to what we have heard, the USB mic is pre-calibrated.  Other USB mics include the UMM-6 and the OmniMic.  To use the EMM8000, you would need an external USB soundcard and a device to provide phantom power.  I use the Soundblaster X-Fi and the Behringer Xenyx 502 which, IIRC, represent a combined cost of approximately $100.

 

The ASIO4ALL is a driver that enables using a laptop's HDMI connection to send signals to the AVR.  On recent laptop hardware, you will have 8-channel support with an HDMI connection, allowing REW to measure individual channels, unlike a stereo setup, which is limited to testing left, right, center, and subs.  IMO, there is marginal value in testing the other channels, but the HDMI connection makes the whole setup much simpler.


AustinJerry's Avatar AustinJerry
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Originally Posted by JapanDave View Post


On my receiver, no it is not. Especially if you want to measure the in room response with EQ applied.

But, lucky for me ,my laptop has 8 channels, so I don't have to worry now.

My sub measurement with the HDMI.

 

If you have 8-channel support, whay are you asking about a stereo set-up?


JapanDave's Avatar JapanDave
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Quote:
Originally Posted by AustinJerry View Post

If you have 8-channel support, whay are you asking about a stereo set-up?
I had to think about this question for a while, but I am pretty sure I have the answer. Probably the biggest reason was b/c when I was researching this in my lunch break today, my laptop was at home and I was at work and since I have never had the need to use HDMI, I guess I did not know if I had 8 channel or stereo on it. I guess it was the same as when I was in kindergarten and I asked the teacher what would happen if I didn't go to the toilet, as time passed I found out pretty quickly, but sometimes you have to ask anyway.
cadett's Avatar cadett
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I was just wondering if the signal that is being sent from REW, through HDMI, could be sent without any processing via the sound card. In Other Words, pass through. Not sure if it is a PCM signal or not. That would definitely squash the need to calibrate the sound card using USB/HDMI, Just a thought.
AustinJerry's Avatar AustinJerry
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Quote:
Originally Posted by cadett View Post

I was just wondering if the signal that is being sent from REW, through HDMI, could be sent without any processing via the sound card. In Other Words, pass through. Not sure if it is a PCM signal or not. That would definitely squash the need to calibrate the sound card using USB/HDMI, Just a thought.

 

As we have been told, there is no need to calibrate the laptop internal soundcard when using a USB mic.  It has nothing to do with using HDMI, or the headphone jack, as the output.  As for processing, you will want to configure the AVR output appropriately, depending on what you want to measure.  In some cases, you may want to measure with Audyssey off, or with Audyssey on, DEQ off or on, etc.


AustinJerry's Avatar AustinJerry
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Version 1.7 of the REW Guide is now available.

 

Updated in this version:

 

- Added "Credits" section

- Added "Cabling Basics when using USB Microphones" section

- Updated "Generating Waterfall Graphs" based on recent discussions in this thread

 

Go to the link in my signature to download the Guide.


kbarnes701's Avatar kbarnes701
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Quote:
Originally Posted by AustinJerry View Post

Version 1.7 of the REW Guide is now available.

 

Updated in this version:

 

- Added "Credits" section

- Added "Cabling Basics when using USB Microphones" section

- Updated "Generating Waterfall Graphs" based on recent discussions in this thread

 

Go to the link in my signature to download the Guide.

It just keeps on getting better, Jerry....


JapanDave's Avatar JapanDave
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Thanks again Jerry for the hard work!
mogorf's Avatar mogorf
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Originally Posted by JapanDave View Post

Thanks again Jerry for the hard work!

A great job, indeed Jerry. Special thanks for the Credits! wink.gif
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