PA Top with AMT

Moritz Bachmann

New member
Nov 7, 2019
Hey guys,

although we never designed speakers by our own (we mainly built speakers with building kits), I´m trying to set up a PA System with Hi-Fi qualities together with 2 friends.
"Unfortunately" we decided to go with Pro AMT´s from Mundorf, precisely the 197PP27R-7- H (see PDF below) and the Beyma MC700ND series, for testing we bought both, the 10" and the 12" Version. Unfortunately because we found too late Peter Morris´ DIY TOP, which might not have the HF as perfectly clear and precise as the AMT (- they got an absolutely insane impulse response and very low distortion compared to Compression drivers) but seems to be the best solution for a high quality Speaker we found on our long search through the internet.

Now, there are many possibilities for us, and maybe some of you could help us going into the right direction.

We want to try out our own designs for sure, even if it is just for learning - double 10"/ 12" in MMT (MTM seems not to be an option as it´s not possible to arrange the two Mids even near half the Wavelenght for a crossover to the the AMT)

Therefore we would also build the double 10" design from Jaroslav Mikyska from the "Double 10 and Horn" Thread to see which fits better for our application (Sound Quality is still a little more important than extreme SPL), and also there, a very low crossover frequency is required

Maybe someone can tell me from the Datasheet of the AMT if it could be possible to go with the Crossover low enough to match the DIY Top, still we will also ask Mundorf what they think (We got the Version with fan, so they should be capable of taking some Watts also in the lower end without burning instantly- but if they do, it would be a lot of money burning)
If there is a chance to use this AMT in the PM Top, that would be absolutely perfect of course, even if the AMT might be the limiting factor in SPL then...

Let me hear what you think about our plans, and what design you would suggest for our application / Speakers

Thank you all in advance for your help!
Cheers, Moritz

(I´m not sure if the attached pdf works- it would be page 19 of the following link


Last edited:

Stef Smits

Apr 4, 2017
I think the AMT still is not suitable for the PM cab. Even though power handling is up, efficiency is still not that high.
However I don't see why not use a MTM arrangement (if going the dual 10/12 range). Such crossover problems do also occur if you use MMT.
  • Like
Reactions: Carl Klinkenborg
Oct 25, 2018
Bideford, Devon. UK
The Mundorf AMT bears more than a passing resemblance to the Beyma TPL150/H as far as specs go. A friend and I have been using the Beyma units on our separate systems for a few years with single 10" ported mids, and I would say this is about as much as they will keep up with, even crossed-over at 1.8kHz, where the subjective sound quality was much better, bizarrely, than at 1Khz or lower, indicating just how good the mids are.
Now I am building a pair of PM90s as I plan to cover a larger audience, since the AMT route (unless a line array) is a dead-end output-wise and are quite unsuitable drivers for the PM90/60 unless output is reduced to a ridiculously low level (around 110dB max. if crossing-over at 600Hz) making the project wholly pointless.
The single ported Beyma 10LW30/N drivers I use (they're very nice!) produce an honest 120-odd db/m from 100Hz at maximum power which matches well with the AMTs flat-out. This combination I feel fulfills the 'HiFi PA' requirement but it's as far as one can go, and multiple upper bass/mid drive units, or those with higher output would be overkill and wasted expense in my opinion.
I am quite apprehensive regarding the sound quality of the BMS coaxials compared with Beyma AMTs (which are the best-sounding HF drivers I have heard with quality that does not degrade at high levels) since the BMS distortion levels look horrendous in comparison, but one has to ask oneself whether or not they are audible. I truly hope not...
I believe that Peter Morris built line arrays using Beyma AMTs which I am sure were absolutely wonderful, but you would need deep, deep pockets to reproduce this setup, and perhaps a larger van...
I'm sorry if the above is not what you want to hear, but there's no messing with the laws of physics unfortunately! Good luck with your project whichever route it takes you, and keep us posted.

Peter Morris

May 8, 2011
Hi Carl,

My line array uses Beyma TPL200, they are 2 dB more efficient and take 2 dB more power than the TPL150 making them more or less a match for a typical 1” compression driver. The low frequency driver is a 300/600 watt 8” Eighteen Sound with a “dog bone” shaped phase plug.

Yes the TPL’s sound better than a BMS4594HE but have no were near the output. The distortion level of the HE version is very good, noticeably better than the standard version.

@ Moritz -To get the PM90/60 to work you need a horn and driver that can go down to around 600 – 700Hz at full power like the BMS4594HE or the BMS464.

FWIW EM Acoustic Halo – C uses a Pro AMT from Mundorf

Moritz Bachmann

New member
Nov 7, 2019
Thank you all for the response, I didn´t really expect the AMT to work in the PM90/60 well- still i wanted to know your opinion.

We already built a test box for the 12" (20L, tuning frequncy around 65Hz) and crossed it at 100Hz to our sub and to the AMT between 700 and 1200Hz- everythink fine here, although the AMT is alwyas a little too intense, from most points of view, also we are missing a lot of output in the lower mids- therefore we hope the double arrangement, probably with the 10" will have more output between 100 and 300Hz.

At the moment we try to figure out which size and tuning frequency fits the 10" and 12" best, but we are struggling a lot to get them flat to even 100Hz, the start to roll off at ~130Hz.... (Box size varied from 35 to 25L (we will test down to 15L) and always 60to 80Hz tuning frequency in 5Hz steps.) We measure with REW and the recommended MiniDSP UMIK-2 Mic, at 1,5m height, free field. In the distance we moved from 15cm to 1m, the further we move, the earlier the rolloff starts. (?)
We will post some measurements tomorrow, but maybe someone can already find a problem why we dont get it played under 100Hz?