MT122 Plot |
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heinrich
Registered User Joined: 21 February 2007 Location: Calindagan Status: Offline Points: 280 |
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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
Registered User Joined: 13 July 2007 Location: Australia Status: Offline Points: 172 |
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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
Registered User Joined: 05 July 2004 Location: United Kingdom Status: Offline Points: 1026 |
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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
Registered User Joined: 13 July 2007 Location: Australia Status: Offline Points: 172 |
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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
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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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
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
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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
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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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
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
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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-
Old Croc Joined: 03 March 2010 Location: ID/UK Status: Offline Points: 6114 |
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cravings
Old Croc Joined: 30 January 2007 Location: Ireland Status: Offline Points: 7442 |
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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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