Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 172 - AVS Forum
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Audio Theory, Setup, and Chat > Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
bao01's Avatar bao01 10:09 AM 10-11-2013
Also, are there any drawbacks to placing a powerful sub under / near a plasma TV?

AustinJerry's Avatar AustinJerry 10:20 AM 10-11-2013
Quote:
Originally Posted by JasonT35 View Post

Hi all

If I get one of the USB mics mentioned in the help guide, do I need to get a radio shack SPL meter also? Or is the USB mic, mic boom stand, REW software and HDMI cable all I need to start taking measurements?

Thanks

I am of the opinion that an SPL is an essential tool for anyone involved in this hobby. HST, whether you NEED an SPL depends on the calibration file that you received with the mic. If it has a sensitivity parameter, REW will read the parameter and allow you to bypass the mic calibration step.

How do you know if your file has a sensitivity parameter? Since it is a text file, you can open the file using a text editor, e.g. Notepad in Windows. The first line in the file will contain the word "Sensitivity" with a numerical value. If the file doesn't have this parameter, you will need to calibrate your mic in REW before you can use it. Any SPL meter will do the trick.
Brian Fineberg's Avatar Brian Fineberg 10:29 AM 10-11-2013
Quote:
Originally Posted by AustinJerry View Post

I am of the opinion that an SPL is an essential tool for anyone involved in this hobby. HST, whether you NEED an SPL depends on the calibration file that you received with the mic. If it has a sensitivity parameter, REW will read the parameter and allow you to bypass the mic calibration step.

How do you know if your file has a sensitivity parameter? Since it is a text file, you can open the file using a text editor, e.g. Notepad in Windows. The first line in the file will contain the word "Sensitivity" with a numerical value. If the file doesn't have this parameter, you will need to calibrate your mic in REW before you can use it. Any SPL meter will do the trick.

when loading the calibration file...you upload the txt file correct? if its sitting in the calibration window...it is loaded? the only reason I ask is because it doesnt show you its loading the parameters...and I wanna make sure the files are loaded into REW
jlpowell84's Avatar jlpowell84 10:32 AM 10-11-2013
Quote:
Originally Posted by kbarnes701 View Post

Did you remember to turn DEQ off?  Are these with Audyssey on or off?

As Jerry says, it is important to be consistent with the parameters because otherwise any comparisons are difficult. Try annotating the graphs when you save them - eg, Aud ON, DEQ Off, 1/6th smoothing, Subs + R + L etc.

Quote:
Originally Posted by kbarnes701 View Post

One starts at 5Hz and one at 15Hz... that confuses the picture somewhat.

I bet the ringing will look really bad even at 450ms or 600ms.

Ok I will label graphs too and use all the same parameters. I admit I was a bit excited and rushed to get my first ever measurements posted. Keith what is your bottom with Submersives?

I will be consistent from here on out for you all. It really is a great tool and privilege to have all the input and assistance on this thread.

It was all pre audyssey. I realized later I should have run Audyssey and then just toggled on and off. That way my distances and timing would have been right. I will do so this weekend
jlpowell84's Avatar jlpowell84 10:35 AM 10-11-2013
Oh yea, about the ringing in my waterfall (or what you can see). Is that combatted with room treatments only?
Brian Fineberg's Avatar Brian Fineberg 10:41 AM 10-11-2013
Quote:
Originally Posted by jlpowell84 View Post


Ok I will label graphs too and use all the same parameters. I admit I was a bit excited and rushed to get my first ever measurements posted. Keith what is your bottom with Submersives?

I will be consistent from here on out for you all. It really is a great tool and privilege to have all the input and assistance on this thread.

It was all pre audyssey. I realized later I should have run Audyssey and then just toggled on and off. That way my distances and timing would have been right. I will do so this weekend

dont worry i was doing the exact same thin g...everything rushed due to excitement ...I will redo all of them and post soon smile.gif
jlpowell84's Avatar jlpowell84 10:53 AM 10-11-2013
Nice! Just got confirmation my Open DRC-AN from mini dsp will be here today! That's 2 day shipping from Hong Kong!

Now I get get some shelf filters in there if needed! Plus any single frequency boost or cut!

Here it is



I won't implement though until the best placement is found smile.gif
AustinJerry's Avatar AustinJerry 10:55 AM 10-11-2013
Quote:
Originally Posted by Brian Fineberg View Post

when loading the calibration file...you upload the txt file correct? if its sitting in the calibration window...it is loaded? the only reason I ask is because it doesnt show you its loading the parameters...and I wanna make sure the files are loaded into REW

In REW, "loading the calibration file" simply means that you have specified the name and location of the calibration file on the Mic/Meter tab of the Preferences screen.
Brian Fineberg's Avatar Brian Fineberg 11:08 AM 10-11-2013
ok perfect...then it was "loaded" smile.gif thanks!
AustinJerry's Avatar AustinJerry 11:10 AM 10-11-2013
Quote:
Originally Posted by jlpowell84 View Post

Oh yea, about the ringing in my waterfall (or what you can see). Is that combatted with room treatments only?

Optimizing bass consists of several steps:

- Finding the best placement for the subs
- Optimizing phase with the mains (the so-called distance tweak)
- Treating the room to reduce ringing

Of these, the last step can be the most demanding. The initial assessment of bass ringing is, of course, the waterfall. As mentioned in the Guide, your objective should be to reduce resonances below the noise floor (~40dB) within 450ms (300ms would be really excellent, 450ms is not too shabby).

Resonances are controlled, for the most part, by bass treatments. Treatments can be DIY, or purchased from a number of reputable companies like GIK Acoustics, RealTraps, ATS Acoustics, etc. Number of treatments and placement are part of an iterative process that involves mounting the treatments, taking new measurements, and enduring strange looks from the Significant Other, if that applies in your case. wink.gif

Over the last several years, I have added more and more treatments, and am now at sixteen 4'x2' 4-inch wall panels, with no room on the walls for any more. My resonances are at or below the noise floor within 450ms, but I fear the 300ms level is unattainable for me.
jlpowell84's Avatar jlpowell84 11:29 AM 10-11-2013
Quote:
Originally Posted by AustinJerry View Post

Optimizing bass consists of several steps:

- Finding the best placement for the subs
- Optimizing phase with the mains (the so-called distance tweak)
- Treating the room to reduce ringing

Of these, the last step can be the most demanding. The initial assessment of bass ringing is, of course, the waterfall. As mentioned in the Guide, your objective should be to reduce resonances below the noise floor (~40dB) within 450ms (300ms would be really excellent, 450ms is not too shabby).

Resonances are controlled, for the most part, by bass treatments. Treatments can be DIY, or purchased from a number of reputable companies like GIK Acoustics, RealTraps, ATS Acoustics, etc. Number of treatments and placement are part of an iterative process that involves mounting the treatments, taking new measurements, and enduring strange looks from the Significant Other, if that applies in your case. wink.gif

Over the last several years, I have added more and more treatments, and am now at sixteen 4'x2' 4-inch wall panels, with no room on the walls for any more. My resonances are at or below the noise floor within 450ms, but I fear the 300ms level is unattainable for me.

I see, I may flip the Submersives over (easy to slide) and get some measurements and impressions. I am curious what behind the couch near field would be like smile.gif
I plan on 5 AST 4 inch panels and bass traps for the right front and right rear corners. The left side is open to the kitchen and dining area. Also the right rear has an AC on the top half so I will only be able to put a 4 ft one in that corner. Actually I could put another little 2 ft one up top.
jkasanic's Avatar jkasanic 11:31 AM 10-11-2013
Quote:
Originally Posted by AustinJerry View Post
 
Quote:
Originally Posted by jlpowell84 View Post

Oh yea, about the ringing in my waterfall (or what you can see). Is that combatted with room treatments only?

Optimizing bass consists of several steps:

- Finding the best placement for the subs
- Optimizing phase with the mains (the so-called distance tweak)
- Treating the room to reduce ringing

Of these, the last step can be the most demanding. The initial assessment of bass ringing is, of course, the waterfall. As mentioned in the Guide, your objective should be to reduce resonances below the noise floor (~40dB) within 450ms (300ms would be really excellent, 450ms is not too shabby).

Resonances are controlled, for the most part, by bass treatments. Treatments can be DIY, or purchased from a number of reputable companies like GIK Acoustics, RealTraps, ATS Acoustics, etc. Number of treatments and placement are part of an iterative process that involves mounting the treatments, taking new measurements, and enduring strange looks from the Significant Other, if that applies in your case. wink.gif

Over the last several years, I have added more and more treatments, and am now at sixteen 4'x2' 4-inch wall panels, with no room on the walls for any more. My resonances are at or below the noise floor within 450ms, but I fear the 300ms level is unattainable for me.

 

One thing I might add (particularly in jlpowell84's situation where he has a bunch of new goodies to improve his SQ) is not to underestimate the importance of step one - finding the best placement for the subs prior to any EQ.  I know your excited to run Audyssey and get your Open DRC-AN in the chain but I think most would agree that you'd be doing yourself a dis-service by not spending enough time finding the best location to start from.  It has been shown time and again that the bettter the starting point the better the results.  Have fun...exciting (at least that's what we like to call it down here in the rabbit hole) times are ahead!  Good luck!


jkasanic's Avatar jkasanic 11:39 AM 10-11-2013
Quote:
Originally Posted by jlpowell84 View Post
 
Quote:
Originally Posted by AustinJerry View Post

Optimizing bass consists of several steps:

- Finding the best placement for the subs
- Optimizing phase with the mains (the so-called distance tweak)
- Treating the room to reduce ringing

Of these, the last step can be the most demanding. The initial assessment of bass ringing is, of course, the waterfall. As mentioned in the Guide, your objective should be to reduce resonances below the noise floor (~40dB) within 450ms (300ms would be really excellent, 450ms is not too shabby).

Resonances are controlled, for the most part, by bass treatments. Treatments can be DIY, or purchased from a number of reputable companies like GIK Acoustics, RealTraps, ATS Acoustics, etc. Number of treatments and placement are part of an iterative process that involves mounting the treatments, taking new measurements, and enduring strange looks from the Significant Other, if that applies in your case. wink.gif

Over the last several years, I have added more and more treatments, and am now at sixteen 4'x2' 4-inch wall panels, with no room on the walls for any more. My resonances are at or below the noise floor within 450ms, but I fear the 300ms level is unattainable for me.

I see, I may flip the Submersives over (easy to slide) and get some measurements and impressions. I am curious what behind the couch near field would be like smile.gif
I plan on 5 AST 4 inch panels and bass traps for the right front and right rear corners. The left side is open to the kitchen and dining area. Also the right rear has an AC on the top half so I will only be able to put a 4 ft one in that corner. Actually I could put another little 2 ft one up top.

 

Disclaimer:  My room is STILL untreated.  HST, I would try to go into your room treatment plan with no preconceived notions about what treatments you might use/need.  The REW measurements should be your guide to applying treatments to address your specific issues.  Of course, I think there are some basic treatment ideas (e.g. first reflection points) that might apply universally but keep your options open until you have time to evaluate your "bare" room response.  I'm in my 8th month of "evaluation" so maybe not the best example! :p


sdrucker's Avatar sdrucker 11:49 AM 10-11-2013
Quote:
Originally Posted by AustinJerry View Post

I am of the opinion that an SPL is an essential tool for anyone involved in this hobby. HST, whether you NEED an SPL depends on the calibration file that you received with the mic. If it has a sensitivity parameter, REW will read the parameter and allow you to bypass the mic calibration step.

How do you know if your file has a sensitivity parameter? Since it is a text file, you can open the file using a text editor, e.g. Notepad in Windows. The first line in the file will contain the word "Sensitivity" with a numerical value. If the file doesn't have this parameter, you will need to calibrate your mic in REW before you can use it. Any SPL meter will do the trick.

+1: even though I have the UMM-6 mic's calibration file loaded and/or "confirmed" by REW, I always pull out my Radio Shack SPL to verify that what I'm getting from REW is what it's supposed to be. Even though you can bypass the mic calibration step with the cal file loaded, since I've got the SPL meter anyway, it takes no more than a few minutes to do that extra step. Maybe silly, but I feel better in case it turns out that there's an unseen issue with using the calibration file accurately for some reason. Especially since we tend to forget that both REW and ASIO4ALL are essentially beta software...

The SPL's right next to my tape measure in my kit. Jerry has taught us well the value of OCD...smile.gif
AustinJerry's Avatar AustinJerry 11:52 AM 10-11-2013
Quote:
Originally Posted by jkasanic View Post
 

 

Disclaimer:  My room is STILL untreated.  HST, I would try to go into your room treatment plan with no preconceived notions about what treatments you might use/need.  The REW measurements should be your guide to applying treatments to address your specific issues.  Of course, I think there are some basic treatment ideas (e.g. first reflection points) that might apply universally but keep your options open until you have time to evaluate your "bare" room response.  I'm in my 8th month of "evaluation" so maybe not the best example! :p

 

Also important to add that there is a clear distinction between the modal region (below approximately 500Hz) and the spectral region (above 500Hz), and the approach to treatments for these two areas is quite different.  Bass traps placed at the intersection of two or three walls address the modal region, while full-spectrum panels strategically placed at reflection points address the spectral region.  Waterfall is the measurement for the former, the impulse (ETC) is the measurement for the latter.


jlpowell84's Avatar jlpowell84 12:50 PM 10-11-2013
Quote:
Originally Posted by jkasanic View Post

One thing I might add (particularly in jlpowell84's situation where he has a bunch of new goodies to improve his SQ) is not to underestimate the importance of step one - finding the best placement for the subs prior to any EQ.  I know your excited to run Audyssey and get your Open DRC-AN in the chain but I think most would agree that you'd be doing yourself a dis-service by not spending enough time finding the best location to start from.  It has been shown time and again that the bettter the starting point the better the results.  Have fun...exciting (at least that's what we like to call it down here in the rabbit hole) times are ahead!  Good luck!

Yes I like the rabbit home smile.gif
Yes I will do this first. Basically I have 4 positioning options. I don't have any resistance from her wink.gif. Picture yourself siting in the middle seat of the couch as the MLP 9 ft from the tv. Right now I have one sub on either side of the tv stand. Other options include as follows. 1-Both behind the couch, 2-one up front to the right or left of the tv stand (most likely the right to corner load it) and the other behind the couch, 3-one up in the right confer and the other about six ft down the same wall (could move that placement a few ft either way), 4-I could put one to the left side of the couch and the other in one of the already mentioned places. Now an important note is thank God for the mini dsp because now I have time delay because I only have multi eq XT and no sub eq ht
jkasanic's Avatar jkasanic 12:56 PM 10-11-2013

I'm sure you've read enough by now to know that a couple good starting points on dual sub placement is 1/4 and 3/4 points of screen wall, mid wall on adjacent walls and mid wall on opposing walls.  Sounds like the 1/4 and 3/4 might be a good starting point.  Not sure how much benefit you would see from colocatng behind the couch but that's why we have mics and REW to measure! ;)


jlpowell84's Avatar jlpowell84 01:20 PM 10-11-2013
Quote:
Originally Posted by jkasanic View Post

I'm sure you've read enough by now to know that a couple good starting points on dual sub placement is 1/4 and 3/4 points of screen wall, mid wall on adjacent walls and mid wall on opposing walls.  Sounds like the 1/4 and 3/4 might be a good starting point.  Not sure how much benefit you would see from colocatng behind the couch but that's why we have mics and REW to measure! wink.gif

Well that's basically where they are now.


And we got this graph, although I realized after that the distance setting was not corrected after I moved

AustinJerry's Avatar AustinJerry 01:27 PM 10-11-2013

"Basically where they are now" is not very precise.  If you are going to try 1/4 and 3/4, which is a very good suggestion, and where I have my two front subs, you need to get out the tape measure and position them precisely.  Several inches can make a measurable difference in bass response.

 

And WRT corner placement, this is usually one of the worst spots because it excites all the room modes, which is normally a bad thing.


djbluemax1's Avatar djbluemax1 02:06 PM 10-11-2013
Just a couple of things to add.
1) yes, I've tended to do measurements from 5Hz to 20kHz because I wanted to see how deep the SubM HPs could dig in my room.
2) DON'T turn the SubMs on their side to slide them around. Even a small grain of sand/dirt will scratch them up. Get furniture sliders. They're super cheap (compared to a SubM) and you can even get them at 4a.m. from a 24-hr Walmart.



Max
sdurani's Avatar sdurani 02:15 PM 10-11-2013
Quote:
Originally Posted by jlpowell84 View Post

Other options include as follows. 1-Both behind the couch,
That would be my 1st choice.

BTW, is that an open passageway on the left side of your room? Also, do you have a similar pic of the back half of your room (to show the couch in relation to the side walls)?
jlpowell84's Avatar jlpowell84 02:18 PM 10-11-2013
Quote:
Originally Posted by AustinJerry View Post

"Basically where they are now" is not very precise.  If you are going to try 1/4 and 3/4, which is a very good suggestion, and where I have my two front subs, you need to get out the tape measure and position them precisely.  Several inches can make a measurable difference in bass response.

And WRT corner placement, this is usually one of the worst spots because it excites all the room modes, which is normally a bad thing.

Ok, I will measure. It "looks," like they are close to 1/4 and 3/4. I can shift if needed. I. Was planning on building my own tv stand to make a home for a 212 Noesis center channel and hold my 100lb 7 channel amp as well as my other gear. Like I said I will measure and get as close as possible but I don't think I will have to move very much.

So let me ask, how does the left side of my front wall being open come into play?
jlpowell84's Avatar jlpowell84 02:23 PM 10-11-2013
Quote:
Originally Posted by djbluemax1 View Post

Just a couple of things to add.
1) yes, I've tended to do measurements from 5Hz to 20kHz because I wanted to see how deep the SubM HPs could dig in my room.
2) DON'T turn the SubMs on their side to slide them around. Even a small grain of sand/dirt will scratch them up. Get furniture sliders. They're super cheap (compared to a SubM) and you can even get them at 4a.m. from a 24-hr Walmart.



Max

You made me laugh out loud with the 4 am comment smile.gif. Will do. I've heard Mark has rolled them up the stairs. Top, driver side, bottom, driver side, top, etc.
jlpowell84's Avatar jlpowell84 02:34 PM 10-11-2013
Quote:
Originally Posted by sdurani View Post

That would be my 1st choice.

BTW, is that an open passageway on the left side of your room? Also, do you have a similar pic of the back half of your room (to show the couch in relation to the side walls)?

I will get complete room pics. Actually I have some before anything was in there I'll load here in a few. I'll get pics of our oversized love seat in relation to the walls. I actually would really like your opinions on that. I have heard you want to stay off the back wall because boundary gain but I have also heard 3/4 is bad for cancellations. I'll get pics and we can collaborate. Thanks guys wink.gif
bao01's Avatar bao01 02:36 PM 10-11-2013
Each time you move a sub, are you supposed to update the distance setting in the pre-pro?
I am using "Direct" mode which means no Audyssey but the Integra DHC-80.3 user guide says that spkr distances and levels are used in Direct mode. I am not sure what they are used for in Direct mode. But if you are moving your subs around quite a few feet, maybe you should update prepro distance settings?

thanks
jlpowell84's Avatar jlpowell84 02:39 PM 10-11-2013
Quote:
Originally Posted by jkasanic View Post

Disclaimer:  My room is STILL untreated.  HST, I would try to go into your room treatment plan with no preconceived notions about what treatments you might use/need.  The REW measurements should be your guide to applying treatments to address your specific issues.  Of course, I think there are some basic treatment ideas (e.g. first reflection points) that might apply universally but keep your options open until you have time to evaluate your "bare" room response.  I'm in my 8th month of "evaluation" so maybe not the best example! tongue.gif

Yes I agree. I want to take a strategic approach and not just hang treatments up anywhere smile.gif
djbluemax1's Avatar djbluemax1 02:42 PM 10-11-2013
Quote:
Originally Posted by jlpowell84 View Post

Quote:
Originally Posted by djbluemax1 View Post

Just a couple of things to add.
1) yes, I've tended to do measurements from 5Hz to 20kHz because I wanted to see how deep the SubM HPs could dig in my room.
2) DON'T turn the SubMs on their side to slide them around. Even a small grain of sand/dirt will scratch them up. Get furniture sliders. They're super cheap (compared to a SubM) and you can even get them at 4a.m. from a 24-hr Walmart.



Max

You made me laugh out loud with the 4 am comment smile.gif. Will do. I've heard Mark has rolled them up the stairs. Top, driver side, bottom, driver side, top, etc.
IIRC, the comments about rolling them up a flight of stairs was with them IN the boxes: a testament to how well packed they are for shipping, AND if someone HAD to do that to move them up a flight of stairs, I'd recommend rolling them on the sides without the drivers. There's not much you can damage on the amp plate the way they're packaged.

Once again though, if someone's spending ~$2500 on a sub after shipping, why wouldn't they just get a $100-$150 handcart to move them? I can understand if Mark showed up to help install them and the owner didn't have one and wasn't physically able to help carry them up the stairs. Mark, knowing how well packed the subs are may have elected to do that to save time/trouble.

When I got my first SubM, I promptly bought a handcart from Lowe's (or Home Depot?), knowing that I'd be moving it on my own (happened to be in Chicago so I picked it up and got to meet Mark). I got the kind that can be configured into a trolley, or locked in a 4-wheeled position at a 45-degree angle. Came in really handy when I got my Focus SEs too as these weigh as much or more than the SubMs, but the boxes are even bigger and more awkward to handle.


Max
Selden Ball's Avatar Selden Ball 02:49 PM 10-11-2013
bao01,

Yes, if you move a sub, you need to rerun Audyssey. That's why you should find the best location first.

The distance values determine the amount of delay applied to each audio channel. This is so that the sound waves arrive at the proper phase (as they are in the original audio tracks) at the primary listening position. The delay distance is determined both by the physical distance between the speakers and the primary listening position plus the delay introduced by any electronics in each channel. Subwoofers often include such an electronic delay.

For the best soundstage, the distance values set for the front main speakers should be identical, and the speakers themselves should both be at exactly the same physical distance from the main listening position.

The individual trim levels determine the relative amplitudes the sounds in each channel will have at the primary listening position. The different trim level values are determined by the speakers' different distances, efficiencies, reflected energy, etc.
djbluemax1's Avatar djbluemax1 02:49 PM 10-11-2013
Quote:
Originally Posted by bao01 View Post

Each time you move a sub, are you supposed to update the distance setting in the pre-pro?
I am using "Direct" mode which means no Audyssey but the Integra DHC-80.3 user guide says that spkr distances and levels are used in Direct mode. I am not sure what they are used for in Direct mode. But if you are moving your subs around quite a few feet, maybe you should update prepro distance settings?

thanks
You need to change the distances to get the correct time delays, otherwise, the sound from the speakers and sound from the subs will arrive at different times.

Since the subs inherently have a delay due to internal circuitry, you can't just use the measured distances. You need to run an Audyssey calibration even if you prefer Direct mode. This will properly measure and set the time delays (as distances) as well as trims for the MLP.


Max
Brian Fineberg's Avatar Brian Fineberg 02:55 PM 10-11-2013
Opinion time

Audyssey before or after minidsp is in the chain?

Audyssey was off for measurements. Then i eq'd based on that. Should i go the other route?

1.run audyssey. Take measurements. Eq based on that

2 take measurements. Eq based on that. Run audyssey
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