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Using energy time curve for acoustic analysis: developing a Home Theatre primer - Page 10

post #271 of 287
Thread Starter 
Quote:
Originally Posted by krabapple View Post

Was this thread killed, or did it die of natural causes?


Like many acoustic threads here it took left turns, right turns, and U turns

Last month I added this in post#1, I don't feel this thread has run its full course of usefullness - yet.
Quote:


[edit Feb-28-2012] Plan to re-boot this thread March/April 2012:
Come spring, when I re-do my 130" screen due to humidity induced warping of the screen, , I will totally remove all my existing side wall/ceiling panels and start from baseline of no treatments on the room
(besides my corner superchunks, which all have front facing reflective treatment on them)

I also will do the following:
-Pure reflective room baseline
-baseline of "the mirror tricK", as I did, with side wall 2" panels + 2" air gap
-Pure ETC approach and using 4" panels + 4" air gap at specific locations verified by ETC
-compare and make objective and subjective assessment
All above is being done utilizing porous absorbers.

As to dragonfyr's editing/removing his comments in specific posts for whatever reason....not sure if that happened or not.
post #272 of 287
Quote:
Originally Posted by mtbdudex View Post

As to dragonfyr's editing/removing his comments in specific posts for whatever reason....not sure if that happened or not.


From what I can see, the thread's littered with replies to dragonfyr posts that no longer exist.
post #273 of 287
maybe he went back to the 2D Flatland that is the frequency-domain and took all of his commentary with him!
post #274 of 287
Thread Starter 
I posted this inquiry to the forum operators in the Forum Operations Center area:

Quote:
Originally Posted by mtbdudex View Post

What happened to the majority of member "dragonfyr" posts from the thread Using energy time curve for acoustic analysis: developing a Home Theatre primer ?

Did the server go down and the back-up miss them?

He had 20-30 posts there with good info, now only 7 are left, search that thread based on member name:
http://www.avsforum.com/avs-vb/searc...rchid=21572958


If you do a search on the text "dragonfyr" you can see 19 quoted posts.
http://www.avsforum.com/avs-vb/searc...rchid=21572984
post #275 of 287
So perhaps dragonfyr can again explain why don't need bandlimited ETC? This time I will make a copy of it.
post #276 of 287
Thread Starter 
Quote:
Originally Posted by dragonfyr View Post


dragonfyr;
Did you delete your posts in this thread?
post #277 of 287
Back at this subject now and ... subscribed.
post #278 of 287
Quote:
Originally Posted by localhost127 View Post

source: http://www.hifizine.com/2011/12/list...gy-time-curve/


ETC:




band-limited ETC:




so, with the band-limited ETC, you've not only produced more reflections, but they've also magically increased in gain as well ??

Quote:
Originally Posted by Nyal Mellor View Post


Like I said previously and as you are no doubt aware an ETC (like an impulse response) is dominated by the highest frequency components. What gives you the idea that you would be able to compare an unfiltered ETC to a set of filtered ETCs?


Although this is referring to loudspeaker design it shows that there are multiple ways to analyze the energy decay - impulse response, ETC, filtered ETC, cumulative spectral decay. All have their place http://www.linkwitzlab.com/frontiers_2.htm


Also look here under part 4 absorber placement, you will see the use of band limited ETCs and the same rationale as I mention above for their usage http://www.etfacoustic.com/demoroom.all.html

Nyal, was a satisfactory explanation ever obtained for this question?

That is (bolded part), how are they to be compared?
post #279 of 287
Not that I remember. Of course a band filtered ETC will look different to an unfiltered ETC.
post #280 of 287
Quote:
Originally Posted by Nyal Mellor View Post

Not that I remember. Of course a band filtered ETC will look different to an unfiltered ETC.

Right. But if a fullband ETC favors the high frequency content, when analyzing sliced ETC's, do we need to apply some form of curve to the bands to correct their relation to each other?
post #281 of 287
No, it's just an unfiltered ETC is dominated by the highest frequency components.
post #282 of 287
Quote:
Originally Posted by Nyal Mellor View Post

No, it's just an unfiltered ETC is dominated by the highest frequency components.

When comparing the full band ETC to separate bands of 500hz, 1K, 2K and 4K, the full band looks a lot like 4K plot to my eyes. To say the full band ETC favors the high stuff is an understatement I think.
post #283 of 287
Farfield or nearfield? Try measuring nearfield on axis it should look a lot different
post #284 of 287
Quote:
Originally Posted by Nyal Mellor View Post

Farfield or nearfield? Try measuring nearfield on axis it should look a lot different

Farfield (listening position,approx 8' from speakers).
post #285 of 287
Quote:
Originally Posted by Nyal Mellor View Post

Not that I remember. Of course a band filtered ETC will look different to an unfiltered ETC.



(200us smoothed) (Ignore line at top)

Black = Full range
Purple = 4K
Red = 500hz

An illustration of what I am seeing.
post #286 of 287
The issue is resolved by using broadband absorption, redirection and diffusion.
post #287 of 287
Quote:
Originally Posted by omholt View Post

The issue is resolved by using broadband absorption, redirection and diffusion.

I agree, in principle. I utilize all three of those in my room design. One of the biggest problems here is comparative data. No one posts sliced ETC's at their listening position.
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