Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 53

As I said, I am re-working the instructions.  You need to add the actual distance from your speaker to the mic at the MLP to the distance you derive from the ETC graph (you can use the Audyssey-calculated distance).  Would that make more sense?

Here are the original instructions from Jason:

If your first reflection is at 8.1ft (not 8.1ms, right, but you used the right mouse button, pointed at 0, then dragged all the way over to the first spike while holding down the CTRL key, right?? That's how you convert the ms into feet. REW does it for you as long as you use this technique) that means the total path length, IN ADDITION TO the time it took for the direct sound to get to you (which has no reflections and is shown as the initial spike at 0 in REW) is 8.1ft.

So then what you have to do is (you can imagine this after you get some practice in and then verify you've taken care of it by running another ETC and seeing if the spike is gone) cut a piece of string.

You determine the length of the string by Adding the ACTUAL distance between the microphone and the mid-range driver of your speaker to this 8.1ft measurement.

Then attach one end at the mic, without moving it (it's okay to make the string longer to give you a place to tie it to at both ends, but be sure and mark on it the actual starting point at 0.0'/at mic and the actual 8.1ft+distance between mic and mid-range driver) and the other end to a tri-pod or other temporary device to hold the other end as close to the mid-range driver (including the height of it - literally right in front of it as close as you can get without touching it/damaging the driver) then pull the string taught.

With the string pulled taught simply move the string around, keeping it taught, in all directions until it touches a hard reflective surface. When it does (this isn't necessarily "exact" but pretty darn close, so if the string touches a surface but isn't totally taught or if it "almost" touches a surface but doesn't quite reach, that could still be your culprit) you've found the culprit.

I apologize for the original wrong instructions--ETC graphs are not easy for me.

Quote:

Originally Posted by NicksHitachi 

Quote:

Originally Posted by kbarnes701 

OK guys - question... I was about to do the 'string thing', despite Mrs Keith looking on incredulously as I measure and prepare to cut a length of string

Here is the ETC of my centre speaker (Audyssey is on):





It shows a couple of nasty spikes. The first is at 1.44ms and the second is at 4.76ms. Using the formula on p63 of Jerry's guide gives me the following:

1.44 x 13.39722 is 19.29 inches, or 1.60 feet.

4.76 x 13.39722 is 63.77 inches, or 5.3142 feet.

Multiplying those by 1.13 gives me a total reflection distance of 1.82 feet and 6.00 feet respectively.

The problem is, in my room, it is impossible to have a reflective surface at those distances, given that the MLP (and thus the mic) is approx 9.5 feet from the centre speaker.

What am I missing before I break out my new ball of string delivered so efficiently by Amazon Prime yesterday?


EDIT: The example in the Guide doesn't make much sense either, because it shows a calculated distance of 8.6 feet and, again, that is way too short a distance from the speaker to the reflective point and then on to the mic. Something seems to be amiss...

Make the string:

9.5 + 1.60 = 11.1 feet and stretch to see where it will touch.

also

9.5 + 5.3 = 14.8 feet

see if that helps you identify.

Quote:

Originally Posted by AustinJerry 

As I said, I am re-working the instructions.  You need to add the actual distance from your speaker to the mic at the MLP to the distance you derive from the ETC graph (you can use the Audyssey-calculated distance).  Would that make more sense?

 

Here are the original instructions from Jason:

 

If your first reflection is at 8.1ft (not 8.1ms, right, but you used the right mouse button, pointed at 0, then dragged all the way over to the first spike while holding down the CTRL key, right?? That's how you convert the ms into feet. REW does it for you as long as you use this technique) that means the total path length, IN ADDITION TO the time it took for the direct sound to get to you (which has no reflections and is shown as the initial spike at 0 in REW) is 8.1ft.

So then what you have to do is (you can imagine this after you get some practice in and then verify you've taken care of it by running another ETC and seeing if the spike is gone) cut a piece of string.

You determine the length of the string by Adding the ACTUAL distance between the microphone and the mid-range driver of your speaker to this 8.1ft measurement.

Then attach one end at the mic, without moving it (it's okay to make the string longer to give you a place to tie it to at both ends, but be sure and mark on it the actual starting point at 0.0'/at mic and the actual 8.1ft+distance between mic and mid-range driver) and the other end to a tri-pod or other temporary device to hold the other end as close to the mid-range driver (including the height of it - literally right in front of it as close as you can get without touching it/damaging the driver) then pull the string taught.

With the string pulled taught simply move the string around, keeping it taught, in all directions until it touches a hard reflective surface. When it does (this isn't necessarily "exact" but pretty darn close, so if the string touches a surface but isn't totally taught or if it "almost" touches a surface but doesn't quite reach, that could still be your culprit) you've found the culprit.

 

I apologize for the original wrong instructions--ETC graphs are not easy for me.

BINGO!!!  

Thanks guys. Jerry, I look forward to the revised version of the Guide when you get the chance....

So, Keith, with this new bit of information, what distances are you looking at now?  Are they more realistic?

Quote:

Originally Posted by cuzed2 

Gentlemen,
That practical group discussion above >> just made ETC come into focus for me!!
Seriously that was a relatively short read that puts it into perspective

So just a few more questions (for kbarnes):
What did you find at 11.1 and 14.5 feet ??
I'm now off to Amazon Prime for some special string >>>> what "coefficient of stretch" is best to order?

I haven't done the string thing yet (it's 10pm here now so I'll leave it till tomorrow) but I am guessing that the centre channel is reflecting off the ceiling (the other candidates are already treated). I also have to do the string thing for my L and R channels (where I again think I know the issues). I'll post the results.

Quote:

Originally Posted by AustinJerry 

Quote:

 

 

BINGO!!!  

 

Thanks guys. Jerry, I look forward to the revised version of the Guide when you get the chance....

 

So, Keith, with this new bit of information, what distances are you looking at now?  Are they more realistic?

Yes, Jerry - much better - see my last post.

Quote:

Originally Posted by kbarnes701 

Quote:

Originally Posted by cuzed2 

Gentlemen,
That practical group discussion above >> just made ETC come into focus for me!!
Seriously that was a relatively short read that puts it into perspective

So just a few more questions (for kbarnes):
What did you find at 11.1 and 14.5 feet ??
I'm now off to Amazon Prime for some special string >>>> what "coefficient of stretch" is best to order?

 

I haven't done the string thing yet (it's 10pm here now so I'll leave it till tomorrow) but I am guessing that the centre channel is reflecting off the ceiling (the other candidates are already treated). I also have to do the string thing for my L and R channels (where I again think I know the issues). I'll post the results.

Remember, any speaker can reflect off of any wall.  So the left and right speakers may have a ceiling reflection, and the center may have sidewall reflections.

Version 2.5 of the REW Guide has been posted.

Changes in this version are:

• Updated ETC section by correcting the distance calculation instructions.
• Updated the Pre-Out measurement section to include instructions on creating a microphone calibration file.
• Updated the Measurements Guidelines section with note on how users with 8-channel capable set-ups should configure tests that include sub(s).
• Revised Taking REW Measurements, Section 15.b (page 56) referring to instructions for generating an average.

A copy of the Guide can be downloaded at the link in my signature.

Quote:

Originally Posted by Anechoic 

Quote:

Originally Posted by Pres2play 

Anechoic,how exactly did you get the mic to work?

Gah, I was afraid someone would ask.

Quote:

From earlier posts, I assumed the problem had to do with the way and order the mic is connected, i.e., plug in mic before powerup.

I actually have an issue with my laptop that if a UMM-6 is connected when the power is off, the machine will hang during bootup. I'm running Windows 7 64-bit under Bootcamp on a MacBook Air so that could be an issue with Windows, the Mac, EFI, or all of the above. But if I plug in the mic after it's booted up, everything is fine.

Quote:

If you remedied the problem with the sound control panel instead, can I ask you which driver did you use? Java or ASIO? I used ASIO and maybe the issue is there.

I don't see where, in REW (v5), you have a choice. In ARTA I use the WDM driver, ASIO has always given me problems.

I don't mean any disrespect, but I think you should have revealed to use that you were running REW under Bootcamp on a Mac.  That is clearly a different configuration than most of us are running, and is likely to have a unique set of problems that we would be unaware of.

Quote:

Originally Posted by AustinJerry 

I don't mean any disrespect, but I think you should have revealed to use that you were running REW under Bootcamp on a Mac.  That is clearly a different configuration than most of us are running, and is likely to have a unique set of problems that we would be unaware of.

It shouldn't be an issue, Jerry. All that Bootcamp does is to allow Windows to run on an Intel Mac. It's just a normal copy of Windows running on an Intel processor.

Quote:

Originally Posted by AustinJerry 

Quote:

Originally Posted by kbarnes701 

Quote:

Originally Posted by cuzed2 

Gentlemen,
That practical group discussion above >> just made ETC come into focus for me!!
Seriously that was a relatively short read that puts it into perspective

So just a few more questions (for kbarnes):
What did you find at 11.1 and 14.5 feet ??
I'm now off to Amazon Prime for some special string >>>> what "coefficient of stretch" is best to order?

 

I haven't done the string thing yet (it's 10pm here now so I'll leave it till tomorrow) but I am guessing that the centre channel is reflecting off the ceiling (the other candidates are already treated). I also have to do the string thing for my L and R channels (where I again think I know the issues). I'll post the results.

 

Remember, any speaker can reflect off of any wall.  So the left and right speakers may have a ceiling reflection, and the center may have sidewall reflections.

Oh sure. I was just meaning that the other likely candidates are already treated. I will apply the string thing to every possible place, have no fear :)

Quote:

Originally Posted by cadett 

Quote:

Originally Posted by kbarnes701 

You could always fix it the professional way: gaffer tape

Well after the glue dried. I attempted to use the mic & didn't work. I think i might have pulled one of the three wires lose when trying to fix it.

That's a bummer for sure. Is it not possible to reconnect the wire?

Quote:

Originally Posted by AVRams 

Hello:)
I have a problem, perhaps it's already explained in this forum but I could not find it:
When I try to choose "Input" on REW soundcard page, there is no option to choose UMM-6.
On ASIO controll page the UMM-6 is IDLE while the Realtek High Defenition Audio is Active.
How do I change that?
Thanks in advance:)))

That happened to me the first time I tried to use it. Much plugging and unplugging, shutting down and restarting, connecting and disconnecting in random orders, connecting the mic without HDMI connected and vice-versa later, it all started to work and has done so since. I didn't even need to use the incantation.

When you plug the mic in, did you get the little Windows popup about installing drivers etc?  Also, it can, apparently, take up to 60 seconds for Windows to recognise a USB mic, but I guess if it is showing in ASIO that Windows knows it's there.