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-   -   The One and Only Full Range AMT (http://www.diyaudio.com/forums/full-range/156466-one-only-full-range-amt.html)

RayCtech 9th December 2009 01:25 PM

The One and Only Full Range AMT
 
In my search for a true Full Range driver I did not find any drivers that was satisfying..

First I designed a 8" driver, but it could not do more than 10kHz.
To be true this driver could have been a full range unit with 20kHz or more bandwidth, but due to I managed to reduce resonances and breakups to virtually zero it was 10kHz I got.

Most or possibly all full range drivers are possibly not able to deliver much bandwidth if resonances and breakups are controlled.

My investigation shoved that most drivers have an addition of 6 - 12 dB of their true output witch are resonances and breakups.
This starts from the frequency where the voicecoil assembly and the cone assembly have their resonance - typically between 600Hz and 1200Hz.
This are seen as a dip in level and a bump on the impedance curve.
Above this resonance the whole system are unstable and a rising level vs frequency can often be seen.
If the added resonances and breakups are severe the level drops at closer to 18dB/oct when the response falls towards the highs.

So my quest for the perfect full range driver in sense of a 8" dynamic driver ended there...

Then I designed a AMT driver with full range in mind.
After a lot of investigations regarding materials and physical sizes I was limited to a maximum size of the diaphragm.
I designed a diaphragm that was 1mm below the maximum size that could be produced.
Neodym N52 magnets was the strongest I could source and settled for that.
The poleplates was the next issue to be solved and I tried laser cutting first but got problems with warping, and I ended up with ordering some special stamping tools.. Due to limitations with the stamping process both the back and the front plate are made of two 3mm plates that are stacked.

One AMT driver (front plate) measures 240mm x 90mm and have a diaphragm that are 560 cm2 in area, and the Xmax are 1mm.
Compared to a 8" driver with 220 cm2 this AMT have (560/220x1) a calculated Xmax of 2.5mm. The impedance of the AMT are 8.2 ohm.
The AMT measures "flat" from 100Hz to 18kHz and drops of controlled in both ends.
Due to this I will be using five AMT with a crossover at 125 - 250Hz.
One AMT above the crossover frequency and four below.
In a horn enclosure I expect a resonse down to possibly 25Hz.
Due to this I have made a version of the AMT with five diaphragms (front plate measures 240mm x 300mm).

So fare I have finished the cabinets and finished the first AMT driver, the four remaining AMT elements in each driver will be finished shortly, but the combination of the enormous resolution of the AMT and the slow fall in level downwards gives an impression of a system that have nearly all the bass needed.

Due to this I will soon make a system with four or eight AMTīs in a line source with a wave-guide for a truly full range AMT without any components (crossover).

I will post some pictures and measurements shortly...

Zen Mod 9th December 2009 01:30 PM

:worship:

mikadosan 9th December 2009 01:41 PM

Waiting for the pics then... :D Sounds too good to be true then... :D

RayCtech 9th December 2009 01:47 PM

3 Attachment(s)
Some photos..
Front and back of the one element AMT,
and the five element AMT (on element mounted) in the horn cabinet (down firing horn).

NB! this was the first prototypes so please do not look to closely on the finish..
The folding of the diaphragms have been improved in several steps...

c2cthomas 9th December 2009 01:51 PM

Awesome!!! SoCal Surfers would say "Duuuuuuude - U R outa-sight":wiz: or as we would say here in the "south" (southern states) "Shieeeeeeeet" :up:

I have my ESS AMT1's - but this is something even the best minds have not been able to accomplish in the 40 years I have been around - so Incredible!

We of course await photo's and info. To be valid you will need independent confirmation and testing of the device so I am putting myself on the list of people you should provide some "test units" to!!! :rolleyes:

Crazy Serb will try to beat me to 'em though - I know I can count on that! :D

feyrerm 9th December 2009 03:13 PM

Is there a paper on the web with diagrams and schematics on the theory and design of this type of speaker. Things such as the diaphragm makeup, circuit layout, magnet placement would be helpful. I'm thinking of trying a diy amt as well.

Thanks

jkeny 9th December 2009 03:57 PM

Fantastic, Ray, I wasn't aware that you had built these yourself - I thought that the AMT's were a commercial driver that you had mounted into horns!
This is DIY par excellence! A viable new DIY driver based on AMT theory is not something trivial - I commend your technical prowess :)
Looking forward to the details of this build :)

PS Your complete system would appear to be as resolving as can be achieved with current technology - SDTrans192 SD card player -> Sabre DAC (to be decided) -> Balanced JFET LU1014D poweramp -> AMT speakers - Awesome !!!!!

cocolino 9th December 2009 04:02 PM

Wow
 
Quote:

Originally Posted by RayCtech (Post 2007342)
In my search for a true Full Range driver I did not find any drivers that was satisfying..

Then I designed a AMT driver with full range in mind.

There usually isn`t any "news" in the loudspeaker world, be it commercial or DIY, that catches my interest for more than 5 minutes .....but.....an AMT capable to play from 150Hz upwards would be really something very, very special.
Can`t wait to see some more details about the construction, data and hopefully measurements eventually.
I`ll definitely follow this thread closely!

RayCtech 9th December 2009 04:16 PM

Quote:

Originally Posted by feyrerm (Post 2007436)
Is there a paper on the web with diagrams and schematics on the theory and design of this type of speaker. Things such as the diaphragm makeup, circuit layout, magnet placement would be helpful. I'm thinking of trying a diy amt as well.

Thanks

The patents Oskar Heil issued are easy to find and are possibly the only help you will get...

When I was searching for someone that could manufacture my diaphragms I was amused time after time..

I got some samples of AMT diaphragms, and when I compared those with the patent papers - they was bluecopies of the drawings in the patents.

Due to my implementation of AMTīs are my own and I have used my own "head" - my AMTīs are more different then like all other implementations.
The layout of the diaphragms are so different from the patents that the manufacturer of the diaphragms was sure they could not work.

And as I am using materials that never have been used in AMTīs before, the manufacturer had to implement a new production process and both the film and the conducting materials had to be special ordered.
As my diaphragms only are 12.5 micron thick I was told time after time that a AMT could not be made, and certainly not a 560 cm2 diaphragm that was intended for playing bass. I was also told that it was not possible to use so strong magnets as the neodym N52 magnets I use either together with the thin diaphragms.
All this may be true if I had copied the patents.

But the diaphragms are the easiest part.

The holding/folding container for the diaphragms was also very difficult to find someone to manufacture.
They are made of good old "pertinax" and are 3D CNC machined by a company in Germany.

I have two other AMTīs finished as designs - a 2000 cm2 bass transducer with Xmax of 2mm, and a complementary midrange / treble AMT with a expected bandwith of 50kHz or more.

As the AMTīs I have now are extremely difficult to assemble they are not yet suitable for DIY.

RayCtech 9th December 2009 04:23 PM

Quote:

Originally Posted by cocolino (Post 2007484)
There usually isn`t any "news" in the loudspeaker world, be it commercial or DIY, that catches my interest for more than 5 minutes .....but.....an AMT capable to play from 150Hz upwards would be really something very, very special.
Can`t wait to see some more details about the construction, data and hopefully measurements eventually.
I`ll definitely follow this thread closely!

I will post measurements later this evening.


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