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Multi-Way Conventional loudspeakers with crossovers

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Old 9th April 2014, 07:12 PM   #191
noah katz is offline noah katz  United States
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Seems like if it was 30" wide it would hold directivity (-6 dB/45 deg) much lower than the ~1.5 kHz shown in the sonogram.

What device is your impressive sonogram from?
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Old 9th April 2014, 07:53 PM   #192
ScottG is offline ScottG  United States
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Quote:
Originally Posted by gainphile View Post

Click the image to open in full size.

This is the AV8 (as seen below) polar, NOT the elliptical PSE-144 "unity" type.
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File Type: jpg IMG_6658.jpg (71.0 KB, 759 views)
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Old 9th April 2014, 07:55 PM   #193
ScottG is offline ScottG  United States
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This is the PSE-144's elliptical "unity" horn horizontal polar:
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File Type: gif PSE-dir-h.gif (54.6 KB, 763 views)
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Old 9th April 2014, 07:59 PM   #194
ScottG is offline ScottG  United States
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In both cases the scaling is so large that it's of little use.. plus, I believe both are normalized plots.
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Old 9th April 2014, 10:19 PM   #195
Flaesh is offline Flaesh  Russian Federation
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They have some interesting shaped horns
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wow! I invented such shape for corner placement 2 years ago but havn't made it ..
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Looking at the finish they appear to be molded in the Isengard ..
Nevertheless I like them. Remains me from the old days when 'high tech' was measured in kilograms
looking very beautiful! and the price is moderate..
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Old 9th April 2014, 10:23 PM   #196
noah katz is offline noah katz  United States
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Scott,

Thanks for the plot, that's more like it.

Not sure what you mean by the scaling, looks normal to me.
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Old 9th April 2014, 11:25 PM   #197
ScottG is offline ScottG  United States
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Originally Posted by noah katz View Post
Scott,

Thanks for the plot, that's more like it.

Not sure what you mean by the scaling, looks normal to me.


You're welcome! (..the prior plot looked odd to me as well. )


The major problem is the plot's db range. It's MUCH to "broad" - with a single color (Red) that spans a large range of spl - a full 12 db on the AV8 plot alone (..and who knows how much on the PSE-144).

Even the "pattern" plot (as opposed to the color "sonogram" plot), is really "broad" - with 16 db interval scale (..and made worse with measurements derived from 1/12 octave smoothing).

The range should have been closer to 1db (with color gradations based on that), and the initial measurements should have been at most 1/24th octave smoothing. As both plots are currently displayed you only see the very "broadest strokes" of polar behavior.
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Old 10th April 2014, 12:31 AM   #198
gainphile is offline gainphile  Australia
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Quote:
Originally Posted by ScottG View Post
This is the PSE-144's elliptical "unity" horn horizontal polar:
OOPS Silly me

Yes this one is the correct Polar Plot of PSE-144

Click the image to open in full size.

Click the image to open in full size.
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Old 10th April 2014, 08:03 AM   #199
Juhazi is offline Juhazi  Finland
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You guys who are complaining about the scale in these - Please note the HUGE DIRECTIVITY INDEX this horn has. It is a totally different animal to conventional loudspeakers, even Geddes's Summa/Abbey.

But I agree with you so that it would be better to have a standard for these. Perhaps soon we will see better comparisons done by RedSpade or gainphile...
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Old 10th April 2014, 09:59 AM   #200
paulspencer is offline paulspencer  Australia
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The scale is chosen so that a contour line shows up that corresponds to the beamwidth (-6 dB). If I were to force the PSE-144 sonogram to follow a particular standard, you would not so easily and intuitively see how its dispersion compares to the 80 degree nominal target.

The darker regions around 5 - 7k (15 - 35 degrees) meant I had to change the scale for this to occur. The plot is normalised and so it makes this region look like a peak off axis. In reality, it is a dip from 0 - 15 degrees.

I should also point out that the more recent plots of mine aren't comparable to earlier ones, which had much more smoothing and a shorter measurement window. This provides greater resolution in the data, but to achieve it I had to place the horn so high up in the air that it became a bit of a hazard. We had a little gust of wind ... "it's falling" and I turned around to see a horn almost ONE METRE wide (36") about to come crashing down onto the ground.

Let's just say plans are underway to build a new measurement system.

There are many practical challenges in taking measurements like these. In this case, the thing needs someone to hold it in place, as the mouth sits on the pivot point of the turntable, so the weight is sitting at the back and makes it unstable. Otherwise, the angles are incorrect and the distance to the mic changes each time. A speaker this wide requires greater mic distance to pick up baffle effects, meaning the speaker has to go up higher again. Further, the smoothing applied by the software is added to any gating. If you generate an ungated sonogram, the dispersion in the low midrange region is different. Short measurement windows smooth the data even more.

So you have a person holding the horn and turntable the whole time and speed becomes important. Hence, I use a normalised plot with a quick DSP crossover that is put together quickly.

One surprise with this horn is that it's less imposing than the pyramid MDF prototype that went before. WAF would be better than you might expect, although there are some women who call anything bigger than Bose an interior disaster.
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