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Author Topic: Mundorf Pro AMT ribon tweeter  (Read 15724 times)

Jim McKeveny

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Re: Mundorf Pro AMT ribon tweeter
« Reply #10 on: November 09, 2012, 07:53:50 AM »

Nit-picking:

Is the pleated diaphragm polyamide or polyimide? The literature is ambiguous.

DuPont has made noises about discontinuing the production of certain Kapton items.

Pleating the diaphragm in Heil AMT style creates a very obvious stress failure locale. Because of an arcing failure/fire mode - where the Kapton transforms from insulator to conductor - Kapton is no longer permissible for airplane wiring. Enhanced fire potential in a flown wood+other combustibles speaker cabinet is not a good idea.

I'm just spitballing here, but these could be part of the reason why we will not see widespread adoption of the Mundorf AMT.
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #11 on: November 09, 2012, 08:00:27 AM »

Hi Jim, i have no idea concerning the material of the diaphragm. This is Mundorf's cook!!!

Hi Scott, the main problem with AMt's is the power handling and so, dia's deformation due to this. Air is a very bad thermal conductor so, the thermal energy keeps on the wire and the dia. Also, like in the compression drivers, some thermal compression will affect the spl of both.

Use a fan don't mean that AMT are not reliable at the end (I think that most of Mundor's AMT don't have fan cooling). Mundorf decided to do that because he wanted to have less thermal compression than compression drivers, and of course, also to have a better reliability of the AMT transducer.

xavier
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #12 on: November 09, 2012, 08:13:56 AM »

Hi again Jim,

When I started making some tests on the AMT336, Mundorf made around 10 prototypes of motor structure and more than 20 prototypes of dias with several changes to improve spl, THD, TIM, sensitivity and reliability. I burn a lot of dias in our lab, and send these back to Mundorf and than, he analyzed each failure. What I can tell you is that in term of breakdown voltage and dynamics voltage, I reached about 125Vpeak under 11 ohms. That represents about 1420Wpeak with an original power handling of around 150Wrms. Here I talk about only one diaphragm (there are two dias in an amt336). This mean that if you feedup AMT with voltage amplifiers, and not power amplifier, we should reach very high spl with an excellent reliability.

Of course, our LT1 system is still on stage now with the last version of AMT336 drivers, and we made about 20 gigs with the system, and never get failures anymore. Also, AMT are very sensitive to distorsion. The capability of AMT to ''follow'' the signal due to low inertia makes appear very high acceleration if the amplifier get in ''peak''. Peak voltage is comparable to square signal in term of acceleration changes. So, if you have a lot of acceleration, a lot of mech stresses appears. Mundorf worked a lot on this to be sure the wire of the dia will remain stable is time. So, for me, use an AMT means use a high voltage /small current amplifier to benefit of the high acceleration factor of the dia.

your impressions?

xavier
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Jim McKeveny

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Re: Mundorf Pro AMT ribon tweeter
« Reply #13 on: November 09, 2012, 08:22:20 AM »

I visited the cabinet manufacturer website. Seems you are deep into this, and perhaps doing a little underhanded promotion?

If indeed this is a new & fantastic & cost competitive technology, we engineers will soon be quite receptive and vote with our dollars.
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #14 on: November 09, 2012, 08:39:25 AM »

Hi Jim,

I appreciate your remark. Of course, Audiofocus is the company where I'm working since more than 12 years, so, of course I'm deep into this!!!! I started that department alone with my boss, and now, we have our own manufacturing in Belgium. We are a small company, motivated to keep in Europe either if it is hard!!!

Posting here is not to promote AF, I never talked about any price, or available product, or any contact, or any need of distributor... The only system I mentioned was the LT1, and this is just a project, this is not for sale!!!!

I'm sorry to tell you that I came around here just to meet people who made some tests on AMT from several companies, to have your experience with that technology. I'm also here to share my experience in audio field and have discuss with other designers.

Sorry Jim, you missunderstood me...

xa

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Jim McKeveny

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Re: Mundorf Pro AMT ribon tweeter
« Reply #15 on: November 09, 2012, 09:19:48 AM »

Completely off-topic: Spa is my family's favorite F1 site.
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #16 on: November 09, 2012, 09:28:28 AM »

Hey Jim, I prefered your first reply concerning your experience with AMT's than your last reply that is off-topic. It was so interesting to read remarks of different guys here. Do you have something against Belgian people?

xa
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #17 on: November 09, 2012, 09:52:09 AM »

Wow wow, wow...Jim, I'm lost here. You talked about the Spa F1 field...i didn't understand, sorry!!!!! I tought it was a joke because in Belgium, we have SPA that means Société Protectrice des Animaux, that means Animals' Protection Society...LOL, sorr, I I I I missunderstood that!!! I apologize!!!!!

Yes, to be off topic, I went to Spa this year for Porsche days, and this is a nice place. I'm not a racing fan, but this field is impressing...

I would like to go there and see an F1 race but this is already sold out or very very expensive and makes...too much noise.

Did you ever come here in Belgium? How is it possible that your family know Spa?

If you have the time, come around Spa, and visit the nature all around. It's very very cold but so beautifull and not so far from me (around 50km).

CU, xa
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Marchal Xavier

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Re: Mundorf Pro AMT ribon tweeter
« Reply #18 on: November 09, 2012, 10:13:21 AM »

To get back to the original subject, I never said these drivers are THE perfect drivers, I don't say this will make a revolution, I just say that perhaps, they made a lot of improvement to try to reach compression's performances but with a very higher quality. I see that like a bridge between the HiFi and Pro.

I think that Mundorf is very open to deliver samples to make some tests if you want. That should be helpfull for me too because I don't have the time to test all his range. I'm here to share and have infos, to discuss with ''crazy'' people who have theory and practice.

remarks are welcome.

xa
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Art Welter

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Re: Mundorf Pro AMT ribon tweeter
« Reply #19 on: November 12, 2012, 11:35:23 AM »

To get back to the original subject, I never said these drivers are THE perfect drivers, I don't say this will make a revolution, I just say that perhaps, they made a lot of improvement to try to reach compression's performances but with a very higher quality. I see that like a bridge between the HiFi and Pro.

Marchal,
The Mundorf 336PP27F looks like an excellent driver above about 2500 Hz, where it drops off at around 24 dB per octave due to excursion limitations.

Distortion rises rapidly below 2500 Hz, with "bad sounding" odd order distortion exceeding even order.
The 336PP27F requires approximately five times the power misband as a 3" diaphragm compression driver to achieve the same SPL, and the compression driver could be used down to 500 Hz with similar distortion levels as the 336PP27F has at 2500 Hz.

The 336PP27F is touted as a "tweeter for three way application", appropriate terminoligy for a driver that must be crossed at around 3000 Hz to sound clean at high power, less than a decade of operation which covers very few fundamental frequencies other than the upper range of a piccolo.

For a midrange driver to sound as clean, it should be limited to around a decade of operation, putting it's range from around 300-3000 Hz.
This forces the LF in a three way system to cover 30-300 Hz, which then requires the LF portion to be flown.

For professional large scale high SPL applications, it seems that the ribbon driver still is only applicable as a tweeter for four way use.

I see that more like a toll bridge between the HiFi and Pro ;) .

Art Welter
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Re: Mundorf Pro AMT ribon tweeter
« Reply #19 on: November 12, 2012, 11:35:23 AM »


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