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MT122 Plot

Printed From: Speakerplans.com
Category: Plans
Forum Name: MT122
Forum Description: Discussion / Questions about the MT122
URL: https://forum.speakerplans.com/forum_posts.asp?TID=24135
Printed Date: 09 December 2022 at 9:48am
Software Version: Web Wiz Forums 12.05 - http://www.webwizforums.com


Topic: MT122 Plot
Posted By: Rog
Subject: MT122 Plot
Date Posted: 18 February 2009 at 5:55am
Hi,
 
I get asked how low will the MT122 play all the time, so thought I would link to this post that has a plot I did of an MT122 a long time ago.
 
http://www.speakerplans.com/forum/forum_posts.asp?TID=15865&KW=MT122&PID=153570#153570 - http://www.speakerplans.com/forum/forum_posts.asp?TID=15865&KW=MT122&PID=153570#153570
 



Replies:
Posted By: Rockin
Date Posted: 18 February 2009 at 8:34am
Wow they go down to 125Hz well. Very nice


Posted By: Timebomb
Date Posted: 19 February 2009 at 1:52am
Nice one Rog, theres another plot you did of a single 12" MT horn here:

http://www.speakerplans.com/forum/forum_posts.asp?TID=11586&KW=boke&PID=106434#106434 - http://www.speakerplans.com/forum/forum_posts.asp?TID=11586&KW=boke&PID=106434#106434

Can you remember if the plot you did of the MT122 was in half space or free space? 

Just finnished the last of my punishers today and im hoping i can use them with the single mt112s i have, not tryed it yet, ive been running the punishers up to 120Hz this week with some reflex tops, sounds quite good but some very tight kicks can make the punishers sound a little rough so will try a 100Hz cross to the MTs tomorrow, the MTs kick hard as i remember, hoping 3 MT 12"s to 6 punishers will work nicely as i can fit that lot in 1 van load.


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James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk


Posted By: jonny4288
Date Posted: 19 February 2009 at 5:17am
that plot is useful, thats exactly how my mt122 are constructed, with the two 12" coupled

nice one!


Posted By: heinrich
Date Posted: 23 February 2009 at 6:51am


so at what frequency will it start to comb filter?

for a wild guess is it 900hz and above?


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.....power is nothing without control....


Posted By: norty303
Date Posted: 23 February 2009 at 6:29pm
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
 


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My laser stuff: http://www.facebook.com/SubsonicSystems" rel="nofollow - Frikkin Lasers


Posted By: heinrich
Date Posted: 24 February 2009 at 1:42am
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
 



as we could see on this pic, lobing in the vertical plane at 900hz would be much improve...?



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.....power is nothing without control....


Posted By: norty303
Date Posted: 24 February 2009 at 1:28pm
My pic was based on separation based on the original plans.  As you can see its not really an issue in the vertical plane.  Obviously it will be better with the horns right next to each other, but its not exactly bad to begin with!

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My laser stuff: http://www.facebook.com/SubsonicSystems" rel="nofollow - Frikkin Lasers


Posted By: heinrich
Date Posted: 26 February 2009 at 6:06am
I was also hoping that Rog could write his views why the two 12" were arrange in that way,
since I coudn't find posts concerning this....



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.....power is nothing without control....


Posted By: norty303
Date Posted: 26 February 2009 at 9:01am
I'm guessing its to do with acoustic centres, in the same way that line array cabs have the HF at the centre followed by mid and LF towards the outside.  Ultimately its about practicality, ensuring that the various sections are close enough within their respective passbands to couple effectively.

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My laser stuff: http://www.facebook.com/SubsonicSystems" rel="nofollow - Frikkin Lasers


Posted By: heinrich
Date Posted: 27 February 2009 at 3:12am
mmmmm......ok

I was actually thinking of doing it the same way it was measured with the 12's close together...


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.....power is nothing without control....


Posted By: psytron
Date Posted: 12 March 2009 at 12:38am
here is my plot of a MT122 using std design and SN12b




Posted By: heinrich
Date 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 
 
 
 


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.....power is nothing without control....


Posted By: psytron
Date 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...


Posted By: roborg
Date 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.


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What I cannot create, I do not understand


Posted By: psytron
Date 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 - http://www.speakerplans.com/forum/measurements-for-USB-and-MT122_topic24814.html


Posted By: MarjanM
Date 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?


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Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Tony Wilkes
Date 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


Posted By: MarjanM
Date 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.


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Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Tony Wilkes
Date 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.


Posted By: mykey-
Date Posted: 27 December 2010 at 3:01pm
my guess it's a MT-122 with 2 extra selenium 1'' horns painted F1 stylee?
http://img507.imageshack.us/i/62001160791855862912561.jpg/">




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BbbBBRAAAAPppBBBBbgushhhhhhhhssshhhhhGrAbRAAAAAAPPPPPp = Dubstep


Posted By: cravings
Date Posted: 27 December 2010 at 4:03pm
yeah... and some hardware fitted along the sides for wheelboards maybe?



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