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post #4921 of 9493

@Bao01:

 

Nice second try!  Fry a pair of 802 Diamonds?  :eek:

 

I think the Audyssey low frequency curve looks pretty good, with the exception of the null at ~66Hz.  This could be improved by either adjusting the sub placement, or by adjusting the sub distances in the AVR menu.  The second approach is called the "sub distance tweak", and varies the phase differences between the subs and the mains, which can improve the smoothness of the frequency response in the vicinity of the crossover.  I would try this before adjusting the sub placements.

 

If you need to move the subs around, remember that a very small distance can produce significant frequency response differences.  For example, when I am experimenting with sub placements, I place s strip of masking tape on the floor and mark intervals of 3" on the tape.  I then move the sub 3", measure, then another 3", measure a second time, etc.  Repeat in the other direction.  One direction or the other may result in a shrinking of the 66Hz dip, and hopefully not introduce a peak or dip elsewhere.  It's largely an iterative, trial-and-error process.

 

The full-spectrum response looks really quite good.  Congratulations!

 

Next steps:

 

1.  Try to improve the 66Hz dip with the suggestions above.

2.  Generate Waterfall graphs to assess modal decay times (consult the Guide).

3.  Generate Impulse graphs (ETC) to assess room reflections in the spectral frequency range (consult the Guide).

4.  Post results!

Gear mentioned in this thread:

post #4922 of 9493
^
That dip is nothing to worry about. I would first look at sub+L and sub+R and points within the listening area to get a better understanding of the overall variance.
post #4923 of 9493

OK, I experimented with using the REW Signal Generator and RTA to tweak the sub distances, as per the instructions posted earlier by Markus.  While the process is reasonably straight-forward, I'm not sure it is any easier than the method most of us have been using so far.  Let me explain.

 

First of all, I haven't noticed very much of a difference in applying the sub distance tweak for the past several months.  It could be the current position of my speakers, or the amount of treatment in the listening room, but on a number of recent calibrations, I cannot improve the frequency response that is a result of the Audyssey-set sub distances.  On the positive side, the frequency response measures reasonably flat, and sounds very good.

 

So, the default distance for Sub1 on my system is 11.9'.  I can fine-tune the frequency response by varying the distance by about a foot in the negative direction.  Here are three screen shots of what the RTA looks like:

 

 

 

 

The RTA is set to 1/48 smoothing.  Which one looks better?  Hard to tell, isn't it?  Here are the same three distances, with smoothing at 1/6:

 

 

 

 

I think 11.4 looks best, but the differences are subtle.  Here are the same measurements using the conventional method:

 

 

 

Which one looks the best?  Again, hard to tell.

 

So, why do I think the RTA method is actually less useful (for the distance tweak)?

 

1.  The RTA line is showing a 32-point average.  Every time you tweak the distance, you need to wait 30-60 seconds for the graph to "settle down", i.e. to generate a 32-reading average with readings spaced 1 second apart.  This is somewhat tedious.

 

2.  There is no way to overlay two readings like there is with the conventional method.  I find overlays much easier to compare than looking at two 1/48 smoothed RTA screen shots.  YMMV

 

So, my question to anyone who is interested--does the RTA method represent a significantly better way of doing the distance tweak, or simply an alternative way that is not necessarily better?  And if the latter is true, does this warrant inclusion in the Guide?

 

I suggest you try the RTA method yourself before drawing a conclusion.  I appreciate that Markus shared this with us, and I still think the RTA method will be very useful for sub placement.  However, I did not test this out, because moving subs around is a real PITA.

post #4924 of 9493
Quote:
Originally Posted by AustinJerry View Post

Which one looks the best? 

11.0 to me smile.gif
post #4925 of 9493
Quote:
Originally Posted by AustinJerry View Post

........
2.  There is no way to overlay two readings like there is with the conventional method.  I find overlays much easier to compare than looking at two 1/48 smoothed RTA screen shots.  YMMV
........

I've only used RTA a little, but I think you can overlay curves by using the "save" feature in the RTA function. When you click save, IIRC it saves the current plot (at the instant you click save) to the REW workspace. You can save as many as you like, and then go to the REW workspace and select the graphs that you want to compare. let me know if that doesn't make sense and I'll try to clarify.
post #4926 of 9493

Taking advantage of my energy today, a did another test that some might find interesting.

 

Here is the issue:  What is the difference if someone purchases a USB mic from someplace other than CSL, and downloads the calibration file from the vendor website?  Both Dayton Audio and Mini-DSP allow a customer who has purchased a microphone to log into the support website, enter the mic's serial number, and download a calibration file.  Is this calibration file better, inferior, or the same as the custom calibration files from CSL?

 

I ran the test for my UMIK-1 (although I also have a UMM-6, and could run the test for that mic as well, if anyone is interested).  Here are the results:

 

 

I used the CSL 0-degree cal file (Blue), the 90-degree file (Red), the non-CSL cal file downloaded from the web page (Green), and no calibration file (Black).  For all three measurements, the mic was pointed towards the ceiling (90-degree orientation), which is the normal orientation for REW measurements.

 

The most pronounced differences are in the higher frequencies above ~10kHz.  For lower frequencies, the differences among the calibration files are small enough that there should be no concern.

 

Bookmark this post so you can answer the question, because it is bound to come up over and over again.....


Edited by AustinJerry - 2/11/14 at 7:28am
post #4927 of 9493
Quote:
Originally Posted by J_P_A View Post


I've only used RTA a little, but I think you can overlay curves by using the "save" feature in the RTA function. When you click save, IIRC it saves the current plot (at the instant you click save) to the REW workspace. You can save as many as you like, and then go to the REW workspace and select the graphs that you want to compare. let me know if that doesn't make sense and I'll try to clarify.

 

 

Yes, that does work, thanks.  When you click on the Save button, the current RTA graph is saved over on the left side, just as if you had run a normal frequency sweep.  Then by selecting several graphs in the Legend, an overlay is accomplished.  So one of my concerns has been addressed.

post #4928 of 9493
Quote:
Originally Posted by AustinJerry View Post
 

@Bao01:

 

Nice second try!  Fry a pair of 802 Diamonds?  :eek:

 

I think the Audyssey low frequency curve looks pretty good, with the exception of the null at ~66Hz.  This could be improved by either adjusting the sub placement, or by adjusting the sub distances in the AVR menu.  The second approach is called the "sub distance tweak", and varies the phase differences between the subs and the mains, which can improve the smoothness of the frequency response in the vicinity of the crossover.  I would try this before adjusting the sub placements.

 

If you need to move the subs around, remember that a very small distance can produce significant frequency response differences.  For example, when I am experimenting with sub placements, I place s strip of masking tape on the floor and mark intervals of 3" on the tape.  I then move the sub 3", measure, then another 3", measure a second time, etc.  Repeat in the other direction.  One direction or the other may result in a shrinking of the 66Hz dip, and hopefully not introduce a peak or dip elsewhere.  It's largely an iterative, trial-and-error process.

 

The full-spectrum response looks really quite good.  Congratulations!

 

Next steps:

 

1.  Try to improve the 66Hz dip with the suggestions above.

2.  Generate Waterfall graphs to assess modal decay times (consult the Guide).

3.  Generate Impulse graphs (ETC) to assess room reflections in the spectral frequency range (consult the Guide).

4.  Post results!

 

The dip at 66Hz is very narrow bandwidth - I bet it's mostly inaudible in real life.

 

@bao01 - if you want to try the sub distance tweak, this document contains all the info you need:

 

https://dl.dropboxusercontent.com/u/9653266/Audyssey%20Sub%20Distance%20Tweak%20Procedure%20Oct%202013.pdf

post #4929 of 9493
Quote:
Originally Posted by jim19611961 View Post


11.0 to me smile.gif

 

 

In honor of Jim, 11.0 it is!  Did you flip a coin, Jim?

post #4930 of 9493
Quote:
Originally Posted by AustinJerry View Post
 

 

So, my question to anyone who is interested--does the RTA method represent a significantly better way of doing the distance tweak, or simply an alternative way that is not necessarily better?  And if the latter is true, does this warrant inclusion in the Guide?

 

I suggest you try the RTA method yourself before drawing a conclusion.  I appreciate that Markus shared this with us, and I still think the RTA method will be very useful for sub placement.  However, I did not test this out, because moving subs around is a real PITA.

 

I don't think the RTA method is meant to produce a 'better' result, but it is much easier IMO. The old method was to set a distance, run a sine sweep, save the measurement, set a distance, run a sine sweep, save the measurement set a distance, run a sine sweep, save the measurement, rinse and repeat ad infinitum, or at least for as many different sub distances as you felt made a difference. Using RTA, all one has to do is adjust the sub distance and observe... this makes it much more like the OmniMic method I used to use, which displays the graph in real time. I certainly find the 'real time' method much easier to use. But the results should be more or less identical whichever method is used.

post #4931 of 9493
@ AustinJerry: Wouldn't adjusting the Auddessy set sub distance to improve frequency response effect the time at which the bass reaches the MLP potentially making it out of sync?
post #4932 of 9493
Quote:
Originally Posted by AustinJerry View Post
 

Taking advantage of my energy today, a did another test that some might find interesting.

 

Here is the issue:  What is the difference if someone purchases a USB mic from someplace other than CSL, and downloads the calibration file from the vendor website?  Both Dayton Audio and Mini-DSP allow a customer who has purchased a microphone to log into the support website, enter the mic's serial number, and download a calibration file.  Is this calibration file better, inferior, or the same as the custom calibration files from CSL?

 

I ran the test for my UMIK-1 (although I also have a UMM-6, and could run the test for that mic as well, if anyone is interested).  Here are the results:

 

 

I used the CSL 0-degree cal file (Blue), the 90-degree file (Red), the non-CSL cal file downloaded from the web page (Green), and no calibration file (Black).

 

The most pronounced differences are in the higher frequencies above ~10kHz.  For lower frequencies, the differences among the calibration files are small enough that there should be no concern.

 

Bookmark this post so you can answer the question, because it is bound to come up over and over again.....

 

Interesting test, Jerry.  IIRC, isn't the mic bought from Dayton Audio pretty much the same price as buying it fully calibrated from Herb though?

post #4933 of 9493
Quote:
Originally Posted by Sean Spamilton View Post

@ AustinJerry: Wouldn't adjusting the Auddessy set sub distance to improve frequency response effect the time at which the bass reaches the MLP potentially making it out of sync?

 

That's the point. The idea is to adjust the sub distance so that the phase relationship between the sub and the mains is optimised. Usually, Audyssey does a poor job of this because it never measures the combined response of the sub + satellites.

post #4934 of 9493
Quote:
Originally Posted by kbarnes701 View Post

Interesting test, Jerry.  IIRC, isn't the mic bought from Dayton Audio pretty much the same price as buying it fully calibrated from Herb though?

The Dayton Umm-6 I bought from a 3rd party distributor was 89.95 CAD .. ( and shipping time was much improved as there was no customs to be held at ).
post #4935 of 9493
Quote:
Originally Posted by kbarnes701 View Post
 

 

I don't think the RTA method is meant to produce a 'better' result, but it is much easier IMO. The old method was to set a distance, run a sine sweep, save the measurement, set a distance, run a sine sweep, save the measurement set a distance, run a sine sweep, save the measurement, rinse and repeat ad infinitum, or at least for as many different sub distances as you felt made a difference. Using RTA, all one has to do is adjust the sub distance and observe... this makes it much more like the OmniMic method I used to use, which displays the graph in real time. I certainly find the 'real time' method much easier to use. But the results should be more or less identical whichever method is used.

 

 

Well, as I said, I think you need to try it before you come to a conclusion.  The 30-45 second delay waiting for the average to finish makes at a slow process as well.  And on a Denon AVR, one must access the speaker distance menu, scroll down to the line for the sub, make the distance tweak, and then exit the menu before the change is actually applied.  This is tedious as well.

 

I was expecting something as simple as clicking the distance slider up and down and seeing an immediate effect in the RTA graph.  The 30-second averaging delay is like audio memory--if a change is not instantaneous, it is hard to remember what the previous value was.  YMMV

post #4936 of 9493
Quote:
Originally Posted by AustinJerry View Post


In honor of Jim, 11.0 it is!  Did you flip a coin, Jim?

I flipped all the 3 sided coins I had and they all said the same thing wink.gif
post #4937 of 9493
Quote:
Originally Posted by bao01 View Post


Pics of room are in my gallery:
http://www.avsforum.com/g/a/2276097/my-theater/

It is perfectly rectangular:
Length: 28.5 ft
Width : 22.2 ft
Height: 8.0 ft

for a total of 5062 cubic feet.

Carpet on floor. No room treatments.
System is along long wall but not perfectly centered along the wall - it is about 6 feet off center - see pics in my gallery.
The rear of the front speakers are 24" from wall and the speakers are quite deep.
The two front speakers are just under 8 feet apart, tweeter to tweeter.
The MLP is 8 feet from each front speaker.
The MLP is 10.4 ft from front wall and 12 ft from rear wall.

Any comments welcome.
thanks

Hi Bao,

After looking at the pics of your room I have to say I'm astonished (read = green of envy). I love that room, it's fantastic, ...but I have some objections on your system configuration. Any home theater geek will start off by telling you the most important thing is to have a symmetric layout. Now you say (and show) an off-set layout.

Why?

Why don't you make use of that beautiful room by extending the speakers and subs and MLP placement by making full use of all the boundaries of that room? You have every possibility to do it as per the Book, don't you? Now it's an acoustical challange for you, for your speakers and last but not least...for Audyssey!

Some "suffer" from having hall-ways and openings and kitchen to the side of their room, but you are excempted from all those hinderings allowing you to do the most important arrangement I would call a perfect cold-setup, all before running Audyssey and starting your new life with REW.

Whaddaya think? wink.gif
post #4938 of 9493
Quote:
Originally Posted by jim19611961 View Post

Quote:
Originally Posted by AustinJerry View Post


In honor of Jim, 11.0 it is!  Did you flip a coin, Jim?

I flipped all the 3 sided coins I had and they all said the same thing wink.gif

I was thinking Jim might prefer the slightly higher gain at low frequencies...and I do mean slightly! tongue.gif
post #4939 of 9493
Quote:
Originally Posted by AustinJerry View Post

I haven't noticed very much of a difference in applying the sub distance tweak for the past several months.

You've obviously reached a point where nothing can be improved anymore just by varying distance settings.
Quote:
Originally Posted by AustinJerry View Post

1.  The RTA line is showing a 32-point average.  Every time you tweak the distance, you need to wait 30-60 seconds for the graph to "settle down", i.e. to generate a 32-reading average with readings spaced 1 second apart.  This is somewhat tedious.

Play around with the FFT length and averages. This will speed things up at the expense of frequency resolution and accuracy.
By the way, I didn't propose an "alternative" method. Measurements are tools. You need a hammer for a nail but a screw driver for a screw.
Quote:
Originally Posted by AustinJerry View Post

2.  There is no way to overlay two readings like there is with the conventional method.

Sure, just click the "Save" button in the RTA window. The curves show up in the main window.
Quote:
Originally Posted by AustinJerry View Post

moving subs around is a real PITA.

True but physics doesn't care about such things. We all have to decide for ourselves how far we are willing to go for good sound reproduction. Once you've reached that point you need to stop thinking about it and start enjoying what you have. If you can't then no measuring technique will reduce the amount of PITA you're feeling.
post #4940 of 9493
How can I tell if I ruined my 802 Diamonds? Me so sad. frown.gif

I just got back from shopping:

The Guitar Center: Mogami Gold 50 ft balanced XLR cable: $109.00
Radio Shack: SPL meter ($49), USB 2.0 3 ft extension ($17)
Harbor Freight: little dolly for JL Audio Fathom f113 ($14)

Now i am all set to do something. I just don't know what yet. smile.gif

ok, ok - i will read the sub tweak.
My thought was to try one in the middle of each long wall, facing each other.
The left one is already close to middle of its long wall and now with my new cable and dolly, i can move the right one to middle of opposing long wall.

Is that a good idea?

ok, ok i will read the guide. smile.gif
Edited by bao01 - 10/6/13 at 1:15pm
post #4941 of 9493
Quote:
Originally Posted by Sean Spamilton View Post

@ AustinJerry: Wouldn't adjusting the Auddessy set sub distance to improve frequency response effect the time at which the bass reaches the MLP potentially making it out of sync?

If you look at the transfer function of a real speaker in a real room you'll find that bass is "out of sync" anyways. Some food for thought: http://bobmccarthy.com/phase-alignment-of-subs-why-i-dont-use-the-impulse-response/

Hope that Jerry doesn't read it wink.gif
post #4942 of 9493
Quote:
Originally Posted by mogorf View Post

Hi Bao,

After looking at the pics of your room I have to say I'm astonished (read = green of envy). I love that room, it's fantastic, ...but I have some objections on your system configuration. Any home theater geek will start off by telling you the most important thing is to have a symmetric layout. Now you say (and show) an off-set layout.

Why?

Why don't you make use of that beautiful room by extending the speakers and subs and MLP placement by making full use of all the boundaries of that room? You have every possibility to do it as per the Book, don't you? Now it's an acoustical challange for you, for your speakers and last but not least...for Audyssey!

Some "suffer" from having hall-ways and openings and kitchen to the side of their room, but you are excempted from all those hinderings allowing you to do the most important arrangement I would call a perfect cold-setup, all before running Audyssey and starting your new life with REW.

Whaddaya think? wink.gif

Thank you! That is very nice of you to say so.
To be honest i really like it as well. I like listening to music on weekend afternoons when the room is super bright. For music listening, it's just more pleasant than a dark room imo.
But for movies i have to wait until dark - no big deal for me.

I will try the "perfect" symmetric layout but its gonna kill my lower back.
There is a small desk with a big computer monitor on it where i surf and drink coffee and look out the picture windows into a valley but i can sort that out.



I'll get a small portable desk or something.
Edited by bao01 - 10/6/13 at 1:28pm
post #4943 of 9493
Quote:
Originally Posted by kbarnes701 View Post

That's the point. The idea is to adjust the sub distance so that the phase relationship between the sub and the mains is optimised. Usually, Audyssey does a poor job of this because it never measures the combined response of the sub + satellites.

Ahh ok... I guess I haven't gotten to the phase adjustment stage of my REW learning curve yet. I've just ( as you know ) been working on the frequency response curve ( to be continued when I buy my second sub ). I just assumed that moving the distance in the AVR would keep the same FR of the sub, but change the timing at which the same FR hit your ears - thus putting it out of time with the Fronts - of course I guess I'm getting confused between phase and frequency response. I must do some more reading on this.
Quote:
Originally Posted by markus767 View Post

If you look at the transfer function of a real speaker in a real room you'll find that bass is "out of sync" anyways. Some food for thought: http://bobmccarthy.com/phase-alignment-of-subs-why-i-dont-use-the-impulse-response/

Hope that Jerry doesn't read it wink.gif

I tried reading it but it lost me about half way through. I think I need to improve my fundamental understanding of how sound waves work before tackling that article again smile.gif Perhaps others could weigh in on it's ideology.
post #4944 of 9493
Quote:
Originally Posted by AustinJerry View Post

@Bao01:

Nice second try!  Fry a pair of 802 Diamonds?  eek.gif

The full-spectrum response looks really quite good.  Congratulations!

Thank you!

And thanks for your patience with a novice. I don't know what my laptop was doing yesterday - it was off the reservation.
post #4945 of 9493
Quote:
Originally Posted by kbarnes701 View Post

Not too shabby a result TBH.  As Jim says, you really need to run again with an SPL closer to 80-85dB. See if the result is similar.
Great thanks for the response. Ill do it again tomorrow when the house is free. Ill report back! Thanks smile.gif
post #4946 of 9493
Quote:
Originally Posted by AustinJerry View Post



Jerry,

I'm wondering why your RTA curves seem to show more detail than your graph above. Are you sure the data is unsmoothed? How long is the sweep and the IR window?
Edited by markus767 - 10/6/13 at 11:07pm
post #4947 of 9493
I am not in front of REW right now, but I believe I duplicated the settings in RTA that were shown in your post. ICBW.
post #4948 of 9493
^
Not talking about the RTA settings but the settings for swept sine measurements. Hit the info button of a measurement and the details are shown.
post #4949 of 9493
Quote:
Originally Posted by bao01 View Post

I'll get a small portable desk or something.
Computer stations on wheels are readily available. For a price ..... wink.gif
post #4950 of 9493
Quote:
Originally Posted by Selden Ball View Post

Computer stations on wheels are readily available. For a price ..... wink.gif

my thought exactly
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