12MB700 looks like a perfect copy of 12PE32 from B&C. 

Some calculations told me that that the Paudio SN12MB works better in that small chamber as a closed enclousure with a horn in front, i mean cause of its lower Vas and higer Qts. 

I was looking around and i found a good replacement for my 12MB700, and it is B&C 12PLB100, it is more similar to the P audio one, and it gives me also lower response, my only misgiving is that it looks like a stronger driver, 4 inches (100mm) VoiceCoil Diameter, but also an higer BL., but a less sensitivity. It seems that every parameter describes it more like a MIDBASS/WOOFER than a Higher midbass.

Some other simulations tolds me that the HORN for the 12" driver looks cutted below 1kHz, and it seems strange that in teh plan is suggested to plase X-over in 1,6 kHz. I heard voices from sound experts telling that the horn could handle an X-over below 1kHz, around 700 Hz. I'm quite satisfied with them, but i now need to know the truth :D 

I give u my "spartan" simulation down here. Hope someone could help me..

It was cutted with 180 190 Hz that time..

I'm trying to avoid critical changes. If i could remake my MT121 i would liek to use a 2" driver, capable to handle 800Hz. But i hope that could be another way to solve. I'm searching for a good 12". Also PE32 gives bas response below 190 180 Hz in closed enclousure..

For now i will go with 1" driver, so for now, which driver could behave better in this cab config?

I would like it sound good and could cover 180 Hz cut propelly. It seems mine does not work as it should.

B&C

12PLB100? 12PLB76? 12FW76?

As the others have said, trying to match the horn loaded midrange with a 1" compression driver is never going to work properly.  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 would be looking to bring the crossover point down, maybe 1.2kHz as a starting point.

What are you using as your low mid (kick bass) cabinet up to 180Hz?  That may also be affecting how you're hearing the MT121.

It's also worth bearing in mind that the MT121 is only half of the original cabinet design and is intended to be used in multiples.  One horn at close range may not sound very impressive but several from further back should be.

I mean, the response curve seems to be not so bad, but ears do not completely agree yet.

I got hybrids 18", but now i have a simple 18" relfex as midbass. Overall, my complain was on the hearing of midtops only, IMO them should be more agressiv and "deep" from the 12". I would like to hear them "vibrate" (try to get it :D ).

the only 1" worth using in the mt121 is the bms4550 as you can run it from 900hz....

getting the 12" to play above 900hz forget it....

best 12" 1" combinations ive personally heard used

BMS 12n610 and bms4550

B&C 12ndl76 and bms4550

non budget option

bms12n610 with the bms 4590 2" 1" coaxil... (the 4590 will easy keep up in the mt122 so prob overkill in the mt121)

no driver in real world will play to 100hz, just not going to happen in the mt, 150hz for most drivers, -6 at 140hz for some drivers...

the box full stop will not allow a driver to play 100hz, your kill the driver. By design its not designed for that frequency....

There are 100's of threads re the mt, and best possible drivers, There is only 1 1" driver currently available in the world worth trying in the mt and that's the bms4550, as its capable of playing from 900hz... if you want 100hz your need to use a suitable high bass cab or a dedicated kick cab....

ive listed already for a b&C the best driver is 12ndl76 from bms its the 12n610,

Ive tested and measured mant many 12" drivers in horns, and listened to many more...

possible 1" horns worth looking at are faital pro lth102 or the rcf

Volume is around 18 L for 1 woofer.

The woofer got small Vas (45 l) high Qts (0.44) and Fs 63 Hz.

All togheter, after calculation, returns me an Fb -3 around 100 Hz.

On the plan is written to HPF the 12" section at 200 Hz, seems legit. The most of the drivers u have showed me give results around 160 230 Hz of Fb. 160 could be a good choice, but why choose it when i could do better? 
So Fb -3 is around 100 Hz, but i will also cut it at 180 Hz, 24dB/oct slope. It means that in 90 Hz there will be -24 dB, but at 160 there will be the add of MB and MT that gives me the right feeling. So, unless it is not a reflex midrange, that could help me reach the lower possible, i would like to choose the best sounding driver for it, like the P audio SN12MB, but i would prefeer to get a better brand. So B&C, 18Sound and RCF are my choice. U still think it is better to place a 12PE32 inside it and cut it at 150 Hz but a right tuned one with the parameters that seems legit for that supersmall box?

Am i the only one seeing the problem here?

If this is the real measurement of the box then you need to attenuate the HF for at least 3-4db to even out the response. 

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").

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.

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.

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.

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 

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?

bob4 wrote: I have measured a MT121 loaded with Fane 12". It had a big dip (=hole) between 600 - 1000 Hz that needs a lot of EQ.

I heard about the same problem. Some ppl who wanted to made crossover on them from an audio shop, finally had the x-over around 700-800 hz cause it was not possible to rise over in that horn. So i'm pleased that this is not hardly happening on mine. 

But the same question: which driver u would use to load this project? 
http://hornplans.free.fr/pas5ma1.html
It is quite different from MT121, but i personally would choose that 12NMB420.