2 channel, left and right speakers only graphs - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 08-19-08, 03:32 AM
jaspal kallar
Inactive

Posts: n/a
Re: 2 channel, left and right speakers only graphs

Thanks to Bruce, Wayne and Mike for your responses.

I can attach the ETC (Energy Time Curve) graphs say but I wanted to check what X and Y axis values I should use. Are the default vales okay?

Left: -1.0
Right: 2.0
Top: 0
Bottom: -120

I've added some some acoustic Triangles (Corners), one in each corner and I did some measurements. I'll will therefore attach the before and after waterfall and ETC graphs.

Once again being new to all this I don't really know how to interpret the ETC graphs?

Thanks,

jaspal.

Old 08-19-08, 09:40 PM
Senior Shackster

Mike Bentz

Join Date: Sep 2006
Location: Chicago
Posts: 438
Re: 2 channel, left and right speakers only graphs

An ETC is showing the relative magnitude and time-arrival of every reflection in your room.

So for example, at time=0, you have the largest spike because that is the direct sound of the speaker (which has the least amount of attenuation since it is traveling the shortest distance). If your speaker is 3 feet from the side wall, then you will see another spike in the ETC at a little over 6ms (depending on how far away you're sitting). Sound travels roughly 1 ft every 1 ms (so 6ms corresponds to 6ft). If your listening position is 10ft from the rear wall, then you'll see another spike at ~20ms.

You could sit down and try to calculate all of the reflection paths in your room, but the ETC will show you exactly what is going on and remove all the guesswork (well most of the guesswork).

Next time I get my laptop fired up, I'll try to post some ETC's in a room I just measured a couple weekends ago. That room had some fairly good acoustics, which makes the measurement a lot easier to interpret and describe. A bad room will be so chaotic crazy that it barely makes any sense at all.

As far as the scales for posting plots...I have always felt that you should choose the scale based on the information you're trying to present. So you're probably going to want to pick a scale that shows the initial energy decaying down into the noise floor. As far as the vertical-axis, I would use a dB scale and normalize the data. All that matters is the reflection intensity relative to the initial signal.

-Mike Bentz

"It's territorial with the soundboard. So you're mixing and some dude comes by spewing opinions and trying to turn knobs. It's akin to going up to an artist and painting over his unfinished masterpiece. You just want to shove your paint brush up his nose and throw the soundboard out the window!"
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Old 08-20-08, 03:56 AM
Elite Shackster
Steven

Join Date: Jun 2007
Location: Midwest
Posts: 1,405
Re: 2 channel, left and right speakers only graphs

So then why can't we look at the REW window for a meter rather than when I move my mouse ever so slightly it is more like 10 meters?
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Old 08-20-08, 06:25 AM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: 2 channel, left and right speakers only graphs

Quote:
So then why can't we look at the REW window for a meter
You can. Just zoom in the X-Axis. It will zoom to a time resolution far greater than you would ever require.

brucek
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Old 08-20-08, 12:04 PM
Elite Shackster
Steven

Join Date: Jun 2007
Location: Midwest
Posts: 1,405
Re: 2 channel, left and right speakers only graphs

For some reason each time I try to set the axis in the windows settings it always goes to fully unzoomed. When I zoom in with my mouse I can't see the top of each to measure between. Is there a shortcut key to zoom only X-Axis?
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Old 08-20-08, 12:56 PM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: 2 channel, left and right speakers only graphs

Quote:
When I zoom in with my mouse I can't see the top of each to measure between.
You've confused me for sure...

ETC is no different than any other graph with regard to zooming.

Just click the plus or minus zoom feature and then use the slider to position where you want to look (as shown in the pic below).........

brucek
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Old 08-20-08, 05:07 PM
Elite Shackster
Steven

Join Date: Jun 2007
Location: Midwest
Posts: 1,405
Re: 2 channel, left and right speakers only graphs

Yes that works thank you. I was trying to use the Graph Limits tab and had some difficulties before.
thewire is offline
Old 09-02-08, 04:05 AM
jaspal kallar
Inactive

Posts: n/a
Re: 2 channel, left and right speakers only graphs

Hello again

I've added acoustic treatments. First I added some Echo Buster Corners and a about one week later I added some Cathedral Sound Panels (for 0-200 Hz). As a reminder I have a 2 channel system and no subs.

I attach below the some waterfall graphs at the different stages. I'm still looking at the ETC graphs. Of course I've used my ears to hear how the sound has changed also but I wanted to see if anybody can see any (great) differences between the graphs below?

First no treatments:

Next, 4 (one in each corner) Echo Buster Corners:

Lastly, 4 (one in each corner) Echo Buster Corners and 4 (one in each corner) Cathedral Sound Panels:

Thanks

jaspal
Old 09-02-08, 06:19 AM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: 2 channel, left and right speakers only graphs

To look for changes in waterfall plots, use its overlay function to compare two at a time.

brucek
brucek is offline
Old 09-02-08, 08:44 AM
HTS Senior Moderator

Join Date: Apr 2006
Location: Katy, Texas
Posts: 8,809
Re: 2 channel, left and right speakers only graphs

Hi Jaspal,

There is no appreciable difference in these waterfalls. That's not necesarily a cause for disappointment, however.

The Echo Busters are designed to prevent upper-frequency reflections. As such, any improvement they get you will not show up on a 15-200 Hz waterfall. For that, a full-range reading would be better. The treatments should show less comb filtering and/or better RT60 times.

As for the Cathedrals, it often takes a lot of large bass traps to show a difference in a waterfall. So apparently you don't have enough of them at this point to register an improvement.

Regards,
Wayne

Wayne A. Pflughaupt is offline

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