ESS AMT-1 Air motion transformers ?!

[promitheus]

Well it´s a long time since I started this thread. I have finished my speakers by now.
I used 2 8 inch HDS205 woofers from peerless.
They sound great.
I am still fixing the crossover because I had a few problems.
The woofers had a 3-4 dB Bumb between 800-3000 Hz so I had to use a parallel L-C-R circuit to flatten the bump. I got a lot more bass. The mids where so loud before that I could here much bass.

At the moment I am concerned with the tweeters. I use them above 2200 Hz with a second order filter. The crossover I found for them has a cap that somehow corrects the output of the Tweeter but I am not sure if it is right.

Does anybody have info on the ESS tweeter. I mean Output to Frequency chart.

[Vigier]

Did you mean something like this?

Grtz, Joris

P.S. I just sent you an email about all the measurements...

[promitheus]

Hi,

thanks a lot.
I think it´s the same as mine. Do you think this is accurate?
Would you correct this or use it as is.
I have read somewhere that the tweeter doesn´t need any compensation because the load remains flat.

[Vigier]

Hi Promitheus,

You know where I got this graph from
There are always some differences between the measurements of Klang&Ton and HobbyHifi, but i think they give a very good indication of what the units do. (usually the T/S parameters differ, but the measurement-graphs are pretty much the same).

To calculate the filter you should measure the output of the unit(s) yourself (to get the best out of the units).
I use those graphs for selection of units, but measure it myself when I have it.

Grtz, Joris

[planet10]

Here is the measured response from the 1st set we used:

dave

[promitheus]

Hi,

thanks for the graphs.
What did you guys do with the crossover?
Did you use the tweeter as is or did you do any correcting?

I use the tweeter with a second order filter at 2200 Hz.

[Dsims5354]

This is the 1st time I've ever posted to Anything(!), so please forgive any protocol errors. In 1973 I purchased a set of Heil AMT 1's after much research and listening. The comments so far are pretty accurate, but there are some serious discrepancies. Yes, the bass wasn't much. But the AMT's were outstanding! They are NOT ribbon or ribbon-like tweeters. In actuality, the convoluted diaphram acted more like 2 groups of bellows acting in seies, but in opposite directions. Hence, a dipole. Mine crossed over at 700hz. And they were seamless and pretty linear all the way past 20khz. Remember, every crossover point is an adventure in phase distortion. Also, the efficiency was 93db/w/meter in the INSTALLED driver........through a fat resister to better the woofer's 91db/w/m! In 1974 I purchased a second 10" woofer and desined a proper ducted port enclosure for them. 'Talk about night and day! Using a 3rd order crossover I acheived 28 - 22khz +- 4db. With small amps of the day clipping their little butts off you could over heat and melt the pleated diaphram. Just use a bigger/better amp. My next speaker project will feature multiple Heils or Ravens. I'm looking for a source for the old ElectroVoice 30W. No, it isn't a 30" woofer: It's only 28.25"!

[EchoWars]

Originally posted by planet10
Here is the measured response from the 1st set we used:

dave

Is that impedence graph accurate???

I have an old pair of the Great Heil's (or so ESS tells me they call them), and had no idea that the impedence was so low. A bit over 3 ohms is, well, suprising...

[hifi]

Its a ribbon (more or less) so one can expect a low and almost perfectly flat impedance. ;o) But how do you like them?

/ Micke - who plans to buy a set of Amt:s

[planet10]

Originally posted by EchoWars
Is that impedence graph accurate???

Made with LMS... i have no doubt it is accurate

dave