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measurements for USB and MT122

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psytron View Drop Down
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    Posted: 10 March 2009 at 11:55pm
hello hello :)

Well i have finally taken some measurements of my system via "Room EQ Wizzard" -( great free prog )


details of system under test -------------

1x USB Definimax loaded (standing upright/tall)
1x MT122 sn12b and cp750ti loaded (upright ontop of usb)

USB powered by 1 channel of ca-20 (sound standard)
MT122 phonic 2500 for sn12b's (2 in ll from one channel (4ohm total))
              phonic 1500 for cp750ti
ultradrive for processing

Measurement devices -----------------
emc8000 mic
Eurorack ub1002 for mic phantom and preamp duties
crappy usb soundcard calibrated via loopback in software.


Mic was on a stand level with and pointing at the comp horn about 5m away on axis.

situation a back yard with scattered trees behind mic (2-3m behind) level grass floor, with a wood/brick house +5m behind stack not directly on axis (15deg off??? )

graphs to come...

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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: 11 March 2009 at 12:11am
smooth = 1/3rd octave for all images that are smoothed.

oh and db reading are not calibrated to exact db so use graphs relatively :)

---------------------------------------------------------
USB no eq, crossover, nor filters






USB no eq, crossover, filters but smoothed




Edited by psytron - 11 March 2009 at 12:15am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 2:43am
Mids SN12B no eq, crossover, nor eq.


 

sn12b as above smoothed




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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 2:46am
cp750ti crossed at 1.2khz no eq





cp750ti as above smoothed


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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 2:51am
As you can see there are some peaks and troughs around 150hz for both the mids and the usb i believe this to be an artifact of the location (reflections etc) and probably not caused bu the speaker/box combination.
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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: 11 March 2009 at 2:55am
after setting the crossover points and a bit of fiddling with some eqs and delay this is what i came up with...







here it again smoothed to 1/3 octave




Any questions or suggestions are most welcome :)

enjoy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 3:59am
nice work!

now that you have the program and mic etc. you can phase up your system properly and may find that the dip at 150hz will go away (i presume this is where you are crossing over).

place the mic 1 to 2m away from the stack in line with the bottom of the mt122/ top of usb. Put zero delay on both mids and usb. Invert the mids polarity and start scrolling up the delay. You should start seeing a dip forming at the crossover point. find the delay with maximum dip then un-invert the mids - hey presto they're in phase.

Do the same with the tops and you will find them sounding a lot nicer.


Edited by davey t - 11 March 2009 at 4:04am
Minirig portable soundsystem movement
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 4:01am
any pics?!

where abouts in australia are you? I may be heading over to sydney soon :)


Edited by davey t - 11 March 2009 at 4:02am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 11 March 2009 at 9:23pm
Thanks for the comments Davey T the USB is a nice box :)

I used the behringer emc8000 mic.

I am unsure as to wether the dips around 150hz are from phase issues between USB and the mids in the MT122. my reasoning is such .....

-The dips and peaks occur in BOTH the USB and MT122 even when the other is not playing (see chart below)
-I have set the delays and the minimum troughs are associated with a setting of  USB = )ms SN12b in MT122 = 4.80ms (1.65m) and the cp750ti from the MT122 = 5.68ms (1.950m).
these delays were not found using the method you describe (although i like you method) they were found using the berry's auto eq to get an estimate then adjusting for the minimum peaks/troughs.

here is a graph of the USB and the SN12b from the MT122 both were recorded independantly and the graphs overlayed but the spl level is obviously wrong (uncalibrated).



Note the shapes of the dips are very similar from about 120hz to 160hz is this the Floor or something ???


here are my crossover settings

USB hp 50hz 48db but 
          lp 161hz 24db l-r

MT122
 SN12b hp 124hz 24db l-r
               lp  1.2khz  24db l-r  
CP750ti hp 1.2khz 24db l-r


does this sound within the realms of being correct???


Edited by psytron - 11 March 2009 at 9:32pm
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harold View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote harold Quote  Post ReplyReply Direct Link To This Post Posted: 22 August 2009 at 12:06am
IS this with a horizontal mt122?? And do you have picture??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote orangeberet Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2009 at 1:23pm
Really nice job! The cancellation is not posible with the floor, because they will give you different values for the mids and the sub, because of the different distance to the ground, I think. Here you can see an example of cancellation, I don't know the height of the speakers and the mic, so I have written 1,7 m.

My WEB     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psytron Quote  Post ReplyReply Direct Link To This Post Posted: 24 August 2009 at 8:20am
usb was standing up and the mt122 was on top standing up.

I like ur diagram orange beret and those dips are still a mystery to me....

will have a go at 2x usb with a mt122 on top and see what happens ;)
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