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Old 23rd May 2013, 04:43 AM   #71
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Yes, please stop using the Brad measurement and trying to justify it. That would be very much appreciated and it'll get me off you back about it, as i was involved in Brads work from the beginning and am who manipulated the measurement files for his XO work. Thank you.
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Old 23rd May 2013, 06:04 AM   #72
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Tuxedocivic, I wrote you a PM. Hopefully this will be an olive branch between us, at least start some understanding.

However, I do not see any reason to complain that Brad's measurements were anomalous. As I said in my last post, and many times before, it is my opinion Brad's measurements showed you accurate data. It was just scaled in a way that made it appear wrong to you.

Here is a crude overlay, stretched to approximate the same scale as the SEOS measurement I made:

Click the image to open in full size.
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Last edited by Wayne Parham; 23rd May 2013 at 06:26 AM.
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Old 23rd May 2013, 06:23 AM   #73
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Quote:
Originally Posted by Wayne Parham View Post
As Evan used to say, "More Data, Less Wank".
The yellow and the blue line graph show evident peaks and ridges
What the graph tells is that those ridges would represent real resonances when
playing.
It's what geddes had investigated in. HOLM is the final thesis.
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Old 23rd May 2013, 06:27 AM   #74
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Talking about the topic, I haven't read it
But we should first define what is a speaker and what's its usage, or purpose.
The first graphs about dispersion are a better rendering, but still are no representative of how a speaker sounds - as every measuration, if it is not precisely referred....
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Old 23rd May 2013, 12:23 PM   #75
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Wayne, you seem overly obsessed with the SEOS and doing whatever you can to find flaws, even if it means using charts you know are incorrect. People can look all the want, but I have never made one bad comment about your stuff. Not one. So why have you been bashing it over all the other models that are out there like the JBL or QSC? Can you please explain? Most guys on here don't know about what you've done on other sites.

If this thread you started is all about helping and teaching, then will you help the DIY community design this perfect 'uniform' waveguide?

I'm willing to help out and get them produced so we can keep the price low. You could help with the design. Like I said, the CNC company in Kentucky will cut us front speaker baffles for around $15, and I'll work on the flat packs. And you've already explained why it might be better in this thread.....so we'd have the best of both worlds to pick from. I believe the OS has it's place, I believe the EOS has it's place. Obviously the SEOS does too. So let's make up something you claim will be better.

Let me know if I can help all of us out or not. If you think we need another horn design, I'll do my best to get it done like we did with the SEOS. And because you've already explained all the merits for why we need this other shape, we can just direct people to your threads for the explanation. The DIY community would then be able to choose between the EOS, SEOS, and then whatever you helped with.

Please let me know if you want to proceed.

Also, for future references, can you please explain to us when a uniform horn should be used instead of an EOS, or SEOS?
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Old 23rd May 2013, 01:05 PM   #76
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I ask you to not use that measurement. You agree to not while justifying it. I say thank you for not. Then you continue to use it.

I'm aware of scale. I'm aware of standing waves in boxes. In your pm you said it may have been the nearfield technique. Brad didnt use nearfield.

I don't care if its close to your measurement. I still believe it is not reliable. Stop using it please.
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Old 23rd May 2013, 01:51 PM   #77
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Hi
To whatever degree this thread isn’t about personal choice, there really is more of value than the oddly frequent use of the word directivity without actually looking at the ramifications of directivity.

While that topic may be relatively new in the hifi area, “where the sound goes” is old news and well understood outside that environment.
While not subjective like music appreciation, If one wants to preserve or transfer information like words or a stereo image then directivity is very important at least within a room.

What does one actually hear in a room? Well you hear a combination of direct and reflected sound and in large scale sound to understand words, one wants the direct sound to be ideally at least +10dB louder than the reflected sound. As the Princeton U 3D stereo lab showed, directivity was the single largest factor in having their interaural crosstalk to work as well (which also depends on transmission of intact information to your ears).

If one is mostly interested in nice looking graphs, probably an accuton dome on a flat baffle would give the nicest looking vs angle I have seen. Some of them are incredibly well behaved sources.

On the other hand, from a “what should the speaker do” point of view, go stand where your R or L speaker is with a protractor.
From your loudspeakers location, how wide and how high in degrees is the primary listening area (like your couch say)? This would be where you want to concentrate the sound because there are no reflections before the sound reaches your ears.

The sound energy going in all the other directions plus the direct sound energy are what makes up the reverberant field in your room and as Floyd Toole’s work showed, generally, people prefer the reverberant field spectrum to be similar / the same as the direct fields spectrum.
This requires constant directivity (same angular dispersion vs frequency) and so a tiny dome or other source with little or no directivity is the easiest way to arrive at constant directivity (but of very little or no directivity).

In this case, the spectral balance anywhere you are in the room will sound very similar to sitting in the sweet spot where you hear (what’s left of) a stereo image. You can enjoy this system anywhere in your room.

You can improve on this by having your listening position in the loudspeakers near field or up close to them, this way the direct sound is automatically louder by virtue of the inverse square law and the reflections set back in time and level because you are close to the source while the first reflections farther away..

You can improve on this also by using directivity, simply reducing how much energy is radiated in the wrong or harmful directions that directly drive the reverberant field and reflections. Now the near field became larger (being the region where the direct sound is significantly louder than the reflected sounds). But also now, the reverberant field’s spectrum is the direct sound plus the reflected sound so as before it is desirable to have constant directivity which is needed to have a similar direct and reverberant spectrums.

An example of not having this, many have probably heard large curved wall horns in rooms and while they can sound great in the sweet spot, elsewhere in the room, they can sound very murky and dark, not very listenable there because of the changing directivity.
The reverberant spectrum in the room is the interaction of the loudspeakers total Power response and so horns which narrow with increasing frequency radiate less and less energy with increasing frequency even though on axis they are flat.

The point of all this is, if you guys are really interested in directivity as it effects what you hear, you need to look at the desired listening angle AND how much energy goes elsewhere vs frequency.

In commercial sound, it in pretty common to compare what is happening 90 degrees off axis and to the rear. I haven’t seen that hifi speakers are measure over the entire sphere but often they measure the front half at least in X and Y..

If one loudspeaker measured -3dB @ 90 degrees off axis and another one was -20dB @ 90 degrees off axis, what does that tell you?
In the first case (-3dB) the energy going 90 degrees off axis is only half the level going forward and so will be strongly driving the room.

The one that was -20dB is only radiating about 1/100 the energy @ 90 degrees off axis and so whatever that response looks like, it only contributes a TINY bit to the reverberant spectrum and so the reverberant spectrum is nearly the same as the on axis spectrum.

If one could make a source that confined ALL the energy into the desired angular coverage, the reverberant and direct spectrum would be identical, this is the “grail” for dealing with room acoustics, Constant directivity WITH a high degree of directivity.
The larger the room, the less absorption there is compared to stored energy and so directivity becomes critical.
So one might ask between the conceptually perfect cases and what governs the results, where does one want to compromise? Obviously even with modest directivity like these horns have an audible and positive effect for some listeners.

For hifi where this stuff is somewhat new and nothing like universally considered, just not having the “Christmas tree” looking map is doing pretty good (having the upper and lower sources have similar directivity at xover) and at least in that domain they appear to be more like one source.
It is perhaps time for hifi to adopt / show / measure 3D polar balloons which show how much energy gores in every direction as well.

How much energy goes to the listener(s) angular position, how much energy is radiated elsewhere, how do those horns stack up or compare from the real / acoustical directivity perspective?
Best,
Tom Danley
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Old 23rd May 2013, 02:51 PM   #78
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Quote:
Originally Posted by tuxedocivic View Post
How do you do that dump truck? I wonder how mine would compare to Bill's measurement. My eyeball comparison doesn't show such a high roll off. I was also using the DNA-360, I wonder if it has more roll off than the 250, but I wouldn't know.
Illustrator and Photoshop. It only takes a moment to do it quick & dirty like this, but then I do work with this software all day for a living. Here's those two, and another two:
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Old 23rd May 2013, 03:19 PM   #79
graaf is offline graaf  Poland
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Quote:
Originally Posted by Tom Danley View Post
As the Princeton U 3D stereo lab showed, directivity was the single largest factor in having their interaural crosstalk to work as well
I don't know about "Princeton 3D" but according to Toole the interaural crosstalk is the single biggest flaw of stereo. We do not want it to work at all.

Quote:
Originally Posted by Tom Danley View Post
Hi
If one could make a source that confined ALL the energy into the desired angular coverage, the reverberant and direct spectrum would be identical, this is the “grail” for dealing with room acoustics, Constant directivity WITH a high degree of directivity.
a coincident FCUFS achieves that goal as well
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Last edited by graaf; 23rd May 2013 at 03:23 PM.
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Old 23rd May 2013, 03:26 PM   #80
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I agree with you, Tom. When I first heard cornerhorns designed with constant directivity tops instead of exponential horns, I knew there was something there. After a while, I realized it was the uniform room coverage, the spectral balance of both the on-axis and off-axis sound. The reverberent field has the same tonal character as the direct sound. You could even walk down the hall and it didn't immediately go "bassy" but stayed balanced. I think the toe-in did something to help imaging too, with the forward axes crossing in front of the listeners. So ever since those early constant directivity cornerhorn experiments, I was hooked. Been making speakers like that for over 30 years now.

Dumptruck, thanks for the overlays.
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