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MT-121 Not completly Satisfied - Mysteries
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LeruSound View Drop Down
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Points: 171 		Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 30 November 2015 at 10:50pm
Originally posted by bee bee wrote:

your looking at the cab the wrong way.... look at drivers to play up as high as possible, almost all 12" drivers can handle 150hz... but very few can play to 900hz in the mt before the frequency waves start breaking up inside the horn...

Yeah, i got it, so i would like to get a driver which can olay the upper 900 Hz freq as well as possible, and in the same time i would like it to play as low freq as possble, just that he can respect the natural cut of the filter without problems.

I now know that there r several mismatches in my past choices, but i would like to know which 12" could give me a good response in that cab. I would like to get a better overall, but i would for first to concentrate on the feeling that i think goes from 140 Hz  to  240 Hz, so X-Over zone from MidBasses to MidTops. 
Sorry, when i told DRIVER i meant 12" and when i say COMPRESSION DRIVER i mean the compression drivers (1" 1.4" 2").
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There is nothing wrong with the 12 inch driver. You need to attenuate the hf driver to match the sensitivity. Passive crossover is not a good solution for this type of cabinets. You would need a delay applied to the hf of about 20cm.
Simplified MT might go higher then the real MT, so 1600hz is not out of the question. You just need to lower the sensitivity on the HF.
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Points: 4553 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bee Quote  Post ReplyReply Direct Link To This Post Posted: 30 November 2015 at 11:18pm
simplified don't go higher Marjan, built and rta'd it... it suffers the same phase cancelation as the standard version.

That plot posted looks very wrong, the 12" section is off too....

from what your saying your trying to get the 12" to do something the box wont allow it to do, when the big issue is your using the wrong hf driver, lack of delay, too much gain on the hf.
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Originally posted by ceharden ceharden wrote:

You need a larger format (3" diaphragm, 1.4" or 2" exit) driver and a large horn flare (the XT1464 from 18Sound would be ideal) to give you the control at the lower end. 


I love the look of that horn!

So beautiful! 

Which driver would you pair it with for the Mt121?
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Edited by LeruSound - 30 November 2015 at 11:54pm
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Originally posted by Heathrow_B_line Heathrow_B_line wrote:

Originally posted by ceharden ceharden wrote:

You need a larger format (3" diaphragm, 1.4" or 2" exit) driver and a large horn flare (the XT1464 from 18Sound would be ideal) to give you the control at the lower end. 


I love the look of that horn!

So beautiful! 

Which driver would you pair it with for the Mt121?

It sounds beautiful too!  So clean and very accurate dispersion control.  With the right driver it's usable down to about 800Hz because of it's size.  I've been running a pair for years in my twin 12" (reflex) cabs with 12ND710.  I've been running an original P-Audio SD740N but there are lots of options from the usual suspects (B&C, Beyma and 18Sound) which will sound great on it.  Just to wander off topic a bit further, I'm rather liking the Titanium Nitride diaphragm offerings from 18Sound at the moment...

Back on-topic, I still don't think the 18Sound driver is the issue.  To be honest, I think you might have slightly unrealistic expectations of what this cabinet will produce.  It's a horn designed to do a fairly narrow frequency range and dispersion.  You won't get much low end from it, no matter what driver you use.  The sealed rear chamber will control and limit the excursion.
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plus 1.....
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I will reapeat it: i am not trying to hear 100 Hz from that horn!! I am just trying to get the best HPF result on the 12". 
Maybe i went wrong posting that plot and spending too much time on the HF section. I will fix that problems for sure, but i would like to talk about the mismatch i hear from people in stead of what the designer wrote on the suggested drivers in the plan.
Volume of the rear closed Chamber = 17.5 L (MT121)

You tell me 12PE32 is good but Qtc=0.47 Fc=226 Hz told me u cut it around 150 HPF
  12NDL76 is good but  Qtc=0.46 Fc=200 Hz told me u cut it around 150 HPF
  12MB700 is good but Qtc=0.5 Fc=198 Hz told me u cut it around 150 HPF

Plans tells   SN12MB  is good     and Qtc=0.77 Fc=107 Hz It is suggested to a 160 Hz HPF
  12MB1P is good     and Qtc=0.82 Fc=103 Hz It is suggested to a 200 Hz HPF
  12PLB100 is good     and Qtc=0.71 Fc=96 Hz I thik it as a choice 180 Hz HPF
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Originally posted by ceharden ceharden wrote:


Back on-topic, I still don't think the 18Sound driver is the issue.  To be honest, I think you might have slightly unrealistic expectations of what this cabinet will produce.  It's a horn designed to do a fairly narrow frequency range and dispersion.  You won't get much low end from it, no matter what driver you use.  The sealed rear chamber will control and limit the excursion.




Love the way u replied me. I think we could be in the same wavelenght :D
Sorry for the poor english but i'm from italy and i'm not using translators for improove.
So, i think that a driver which gives the system an Fc around 200 Hz , cutted 180 Hz cuold be worse than a driver which gives the syestem an Fc around 100 with the same 180 Hz cut.
Mine is now at 200 Hz. Some of you r suggesting me to use others that gives me Fc again around 200 Hz.
I am suggested to use one that gives me Fc around 100, 120 - 140 could be also good for me. Maybe i will have a better punch on it? Dont u think so?
Selenium enginners seemed to thik the same in PAS5MA1. In MT121 the same. Probably the horn will kill what i am trying to get from the 12", but it could be better than before, dont it?
I will compensate from 3 dB the HF drivers, because i would not do it anymore with eq until it seems to be so unbalanced. 
If u think i am so wrong please try to stop me, but give me your opinion, and please try to debate with me but in order to get a practical solution. Why it should be so stupid to provide under 200 Hz response? Will the horn kill the 100 200 Hz band completaly? Do you think it could be useless? Why in PAS5MA1 and MT 121 the plans are planned in order to handle that 100 hz from the rear closed chamber? 

Now it sounds like a conspiracy topic or something that can be heard in Tv at late night Shocked


Edited by LeruSound - 01 December 2015 at 12:18am
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Changing drivers to achieve more low frequency capability (heavier cone, more excursion) will be a trade-off because you will most likely lose midrange efficiency, transient response and reduce the upper usable limit.  You will also be running below the cut-off frequency of the horn, which means that you won't get much more output than the driver in a sealed box with no horn in front of it.

Are you calculating the Fc just for the driver in the sealed rear chamber?  If so then of course you will see lower cut-off frequencies for different drivers.  When you take the horn into account as well, that has a much larger influence over the low frequency response because you will get no benefit from it below it's operating range.

Your options are probably to either have more horns together which will help the efficiency at the low end or just to apply some gentle EQ to flatten the response down to your crossover point.

Can you do another measurement of the MT121 on it's own, with no crossover on high or low please?




Edited by ceharden - 01 December 2015 at 12:56am
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LeruSound View Drop Down
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I will For sure. Try get a look to B&C 12CL64. It seems good to me for this experiment.
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I just found another one that gived me good results: 12NMB420 from 18sound.. I think i will go with them.
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