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MT122 Plot

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heinrich View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote heinrich Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2009 at 1:51am
if you have noticed the two dips in between 100hz and 200hz ,
it may not happen if the 12's are just right next to each oher , its the effect of some lobing in the vertical plane.........
but if the 12's are just even closer, side lobes are steered more forward adding up and becomes the member of the main lobe thus more acoustic output at 100 to 200 hz....
 
GURUS please correct me if I'm wrong......Star 
 
 
 
.....power is nothing without control....
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psytron View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2009 at 12:16am
mic was at the same height as the 2" horn so i doubt those dips are from lobeing. I believe them to be an artifact of my measuring / setupand not the actual speaker...
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roborg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2009 at 2:47pm
Originally posted by norty303 norty303 wrote:

It shouldn't comb filter (to the detriment of any sound) if its crossed over correctly as the 12"s should not be playing anything by the time they uncouple.
 
Anything will also be in the vertical plane anyway so much less of an issue
 
 
something to add to your pic, a useful little equation from fresnel diffraction for main lobe widths is lobe width in radians=1.22*wavelength/separation, or
 
main lobe width in degrees=1.22*wavelength*360/2/pi/speaker_separation
                                           =1.22*speed_of_sound*360/2/pi/speaker_separation/frequency
 
so for the above picture the predicted lobe width=1.22*343*360/2/3.1415/.38/900= 95.1 degrees, which is spot on
 
 
@psytron, i think you need to make a new measurement, i think there could be a few reflections causing cancellations in your plot.  Also did you make the plot when the cabinet was stacked as you intend to use it?  You'll find once its stacked directly above bass bins & running in phase, the mid-horn output will couple with the upper bass output & give more output than run alone. 
  I've got an mt122/porn horn inspired design with 2 sn12b's & phase plugs and it has very useable output down to 110hz.
 
cheers,
  Rob.


Edited by roborg - 15 March 2009 at 2:54pm
What I cannot create, I do not understand
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psytron View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2009 at 8:29pm
@roborg here is another post with some more graphs and explanations
http://www.speakerplans.com/forum/measurements-for-USB-and-MT122_topic24814.html
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 21 April 2009 at 5:42pm
I have always wandered one thing.
Rog has speced the MT122 box as 40hX25v dispersion. How is that possible with a 60hx40v dispersion horn like the PH2723?
Marjan Milosevic
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Tony Wilkes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 8:09am
I presume the narrow dispersion (40h) is to allow for simple arraying and to match the high-mid dispersion. If they are to be used in singles the horizontal dispersion of the horn is not so important.

Tony
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 10:18am
Tony i understand the need of 40h but that will apply only for the 12 inch section which covers just a bit of the spectrum. From 1KHz up it is actually 60h box.
Marjan Milosevic
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Tony Wilkes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 11:54am
As I understand it the 12"ers are supposed to be crossed at around the 1K mark so the upper dispersion (comp.) is whatever you want it to be i.e. horn to suit.
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mykey- View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mykey- Quote  Post ReplyReply Direct Link To This Post Posted: 27 December 2010 at 3:01pm
my guess it's a MT-122 with 2 extra selenium 1'' horns painted F1 stylee?



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cravings View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 27 December 2010 at 4:03pm
yeah... and some hardware fitted along the sides for wheelboards maybe?

Edited by cravings - 27 December 2010 at 4:04pm
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