Using energy time curve for acoustic analysis: developing a Home Theatre primer - Page 10 - AVS Forum
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Old 03-28-2012, 09:40 AM - Thread Starter
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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.
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Old 03-29-2012, 01:31 PM
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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.
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Old 03-29-2012, 01:35 PM
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maybe he went back to the 2D Flatland that is the frequency-domain and took all of his commentary with him!
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Old 03-29-2012, 05:22 PM - Thread Starter
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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

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Old 03-30-2012, 01:30 AM
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So perhaps dragonfyr can again explain why don't need bandlimited ETC? This time I will make a copy of it.
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Old 03-30-2012, 08:18 AM - Thread Starter
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Quote:
Originally Posted by dragonfyr View Post


dragonfyr;
Did you delete your posts in this thread?
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Old 04-15-2012, 03:57 PM
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Back at this subject now and ... subscribed.
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Old 11-18-2013, 05:07 PM
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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?

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Old 11-18-2013, 05:10 PM
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Not that I remember. Of course a band filtered ETC will look different to an unfiltered ETC.

Acoustic Frontiers: design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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Old 11-18-2013, 05:20 PM
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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?

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Old 11-18-2013, 05:28 PM
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No, it's just an unfiltered ETC is dominated by the highest frequency components.

Acoustic Frontiers: design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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Old 11-18-2013, 06:14 PM
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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.

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Old 11-18-2013, 06:43 PM
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Farfield or nearfield? Try measuring nearfield on axis it should look a lot different

Acoustic Frontiers: design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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Old 11-18-2013, 07:16 PM
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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).

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Old 11-20-2013, 08:50 AM
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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.

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Old 11-20-2013, 11:24 AM
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The issue is resolved by using broadband absorption, redirection and diffusion.
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Old 11-20-2013, 11:33 AM
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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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Old 05-21-2014, 05:12 AM
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very helpful thread!

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Old 11-04-2014, 01:39 PM
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Great Thread

Just read this whole thread , lots of good info but I still don't understand how to read the ETC results . All I see are squiggly lines . Someone should make a video on how to take measurements , how to understand those measurements , and how to apply acoustic treatments for those measurements.
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Old 11-05-2014, 11:25 PM - Thread Starter
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Using energy time curve for acoustic analysis: developing a Home Theatre primer

^^ HT-Eman
Hi and welcome to AVS forum, there are videos exactly like you desire on YouTube. Do a search and you will find them.

Have you read the REW help file?
Fantastic resources for various acoustic measurements.

Have you bought a measurement mic already? Which model?

I'm in hospital now recovering from RH hip replacement surgery, hard to search and paste via smartphone.

Here, took me a few minutes sitting in my hospital bed...this from Nyal Mellor.

More general how to take measurements:

Via Mikes brain/thumb interface, LLAP
|Tch0rT| likes this.

Last edited by mtbdudex; 11-05-2014 at 11:58 PM.
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Old 11-06-2014, 02:59 AM
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Mike,
Hope your recovery is swift mate, post Hip replacement surgery..
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Old 11-09-2014, 07:41 PM - Thread Starter
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Quote:
Originally Posted by cinema mad View Post
Mike,
Hope your recovery is swift mate, post Hip replacement surgery..
Thx, I can't drive for 6 weeks, so lot's of re-hab and also reading AVS/other stuff.
I've got a few A/V projects planned to keep the brain active.

I'll also take a different viewpoint on this ETC thread and re-summarize, as my knowledge has grown since started it a few years back.
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