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MT122 Plot |
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heinrich 
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Joined: 21 February 2007 Location: Calindagan Status: Offline Points: 280 |
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 Posted: 14 March 2009 at 1:51am |
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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......
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.....power is nothing without control....
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psytron
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Joined: 13 July 2007 Location: Australia Status: Offline Points: 172 |
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Posted: 15 March 2009 at 12:16am |
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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
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Posted: 15 March 2009 at 2:47pm |
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 |
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What I cannot create, I do not understand
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psytron
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Posted: 15 March 2009 at 8:29pm |
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@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
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Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7735 |
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Posted: 21 April 2009 at 5:42pm |
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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? |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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Tony Wilkes
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Posted: 14 March 2010 at 8:09am |
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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
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Posted: 14 March 2010 at 10:18am |
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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.
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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Tony Wilkes
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Posted: 14 March 2010 at 11:54am |
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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-
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Posted: 27 December 2010 at 3:01pm |
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my guess it's a MT-122 with 2 extra selenium 1'' horns painted F1 stylee?
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cravings
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Posted: 27 December 2010 at 4:03pm |
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yeah... and some hardware fitted along the sides for wheelboards maybe?
Edited by cravings - 27 December 2010 at 4:04pm |
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norty303 wrote: