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Multi-Way Conventional loudspeakers with crossovers

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Old 4th August 2010, 06:47 PM   #7011
g3dahl is offline g3dahl  United States
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Wow, you guys have really made some great contributions and given me a great learning opportunity! Thanks to the amazing graphical analysis tools excellent explanations, I'm beginning to make sense a lot of things that I have been previously exposed to but not really understood.

Many thanks to all of you!

I'm finally at the assembly stage with the HF horn supports. More glue-up this afternoon, and painting the grill frames for the woofer cabinets. I'll take more pictures when there's something worth looking at.

Gary Dahl
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Old 5th August 2010, 05:30 AM   #7012
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Come on Gary, quit building and get back to theorising with the rest of us!

Seriously though, great contributions by all over the last several days - signs of progress on all fronts.

I've just downloaded the new REW V5 Beta measurement software from Home Theatre Shack: Getting Started with REW

Looks good so far. Any comments?
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Old 5th August 2010, 06:53 AM   #7013
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by dantheman View Post
Of course ideally, the data is gated but look at the impulse and tell me where the first room reflection point is....

Dan
If there is enough high frequency absorption, then the room relfection is not as evident looking at the impulse, that is why the person doing the measurement better know where his first reflection is going to come from and estimate the gate This is also the reason I stopped using additional absorption material when I measure in an everage room, so that I can see the location of the first reflection easier.

Wavelett transform is a valuable tool to help access how hifidelity the system is because you can do a wavelett transform on any input music, then do a wavelett transform of the output. If you can make these two match like fingerprint matching, then you have a pretty good playback.
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Old 5th August 2010, 03:05 PM   #7014
Pano is offline Pano  United States
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Soongsc, can you post an example of this? Even a bad example would be OK.
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Old 5th August 2010, 03:41 PM   #7015
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Quote:
Originally Posted by soongsc View Post
If there is enough high frequency absorption, then the room relfection is not as evident looking at the impulse, that is why the person doing the measurement better know where his first reflection is going to come from and estimate the gate This is also the reason I stopped using additional absorption material when I measure in an everage room, so that I can see the location of the first reflection easier.
((((SNIP))))
I've done this for quite some time now. Originally I tried to damp it, and I was able to get the floor reflection mostly out of the measurement but not entirely. Now I just leave it undamped to make it easy on me to see. No estimation necessary.

Now that I have the spectrogram, I may go back to damping. I will still measure one undamped just get a clear view of where the gate should be.

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Old 5th August 2010, 04:07 PM   #7016
soongsc is offline soongsc  Taiwan
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Originally Posted by panomaniac View Post
Soongsc, can you post an example of this? Even a bad example would be OK.
I don't have examples of the wavelett thing for display yet, if that's what you are asking for. But you can use a fixed window size throughout the file. The thing that would be convenient is to add a pulse at the beginning of the music as a sync indicator. Run wavelett transform for the original file, the run the wavelett on the file recorded by the mic. The comparision time frame will be pretty long compared to running wavelett on the impulse.

For the absorption thing.
blown up x16.
Attached Images
File Type: gif no absorption.gif (16.4 KB, 357 views)
File Type: gif less absorption.gif (13.9 KB, 355 views)
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Old 5th August 2010, 04:23 PM   #7017
mige0 is offline mige0  Austria
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Quote:
Originally Posted by john k... View Post
I would still like to see the frequency response with the start of the window moved as shown here (pink line):

Click the image to open in full size.
Quote:
Originally Posted by JohnPM View Post
I think someone posted that earlier, but here it is (1/24 octave smoothing):
Attachment 182692
John, any conclusions or theories to share ?

Michael
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Old 6th August 2010, 08:13 AM   #7018
JohnPM is offline JohnPM  United Kingdom
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Originally Posted by mige0 View Post
John, any conclusions or theories to share ?
Sorry Michael, no special insights from me, I just happened to have the IR WAV files as part of something else I'm looking at, haven't really been following the substance of the thread.
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Old 6th August 2010, 10:05 AM   #7019
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Quote:
Originally Posted by mige0 View Post
John, any conclusions or theories to share ?

Michael
Just the obvious. It seems to agree with what George was saying about damping the room and reflections. It really isn't obvious to me, by looking at the impulse, that this is a driver resonance, an inverted pulse indicating diffraction as the origin, or a reflection for which the high frequency content has been absorbed. The FR plots shows that there is significant attenuation of the high frequency content.

But the problem is that there is just too much room "noise" in the data to separate out what's really going on in the first 4 or 5 msec. Like I said, I'd like to see the FR with a a 5 or 6 msec window and then move the first mark to 2.5 msec so the window was shortened to 2.5 to 3.5 msec. I don't use Arta so I can not process the impulse on my own. (Demo of Arta won't allow importing the impulse file.)
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Old 6th August 2010, 12:41 PM   #7020
mige0 is offline mige0  Austria
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Originally Posted by john k... View Post
Like I said, I'd like to see the FR with a a 5 or 6 msec window and then move the first mark to 2.5 msec so the window was shortened to 2.5 to 3.5 msec. I don't use Arta so I can not process the impulse on my own. (Demo of Arta won't allow importing the impulse file.)


Ok - got it:


Full dampening
Click the image to open in full size.
Click the image to open in full size.



Less dampening
Click the image to open in full size.
Click the image to open in full size.



Zero dampening
Click the image to open in full size.
Click the image to open in full size.


(You are in urgent need to add a *.wav import feature to SE ! )


Michael

Last edited by mige0; 6th August 2010 at 12:50 PM.
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