thetubeguy1954

With ribbon strip tweeters the longer length ones (say 7" or longer) have diminished vertical plane radiation beyond their length so as you go up in frequency (into the 10-20 kHz octave) you'll get less overlap in their sound fields. Hence, while you'll have an overall efficiency increase lower in the frequency band but as you move upward the sound fields don't overlap so you realize little or no increase. In one aspect this is a blessing since you'll generate no comb line effects as the separation between drivers approaches two wavelengths where cancellation would occur if their fields overlapped.

Do you have radiation patterns or a link that shows the vertical radiation pattern of a Heil driver?

To answer your other question: You likely can lower the crossover frequency a little as distortion effects would be spread among several drivers for a given SPL created. Again more knowledge on how an individual driver performs would give you some clue as to how the array would perform.

Jim

German-Physiks (makers of the DDD "Walsh-Driver" say this about the Heil; "... leaf transducers which include all electrostatics as well as ribbon type dynamic loudspeakers; flat panel speakers such as the NXT and BEST; the Heil air motion transformer which is essentially a class with only one member."

Albert Von Schweikert says on his website "...Albert worked closely with Dr. Oscar Heil, inventor of the Heil Air Motion Transformer (a folded-ribbon tweeter with some of the finest measurements ever recorded)."

So it appears to be thought well of. Now knowing vertical dispesrion is extremely low and the diaphram is essentially a horn loaded ribbon (front & back) with a very wide horizontal dispertion pattern, do you have any other thought about using 4-8 per side?

Thanks, Tom Scata (thetubeguy1954)

I did have some AMTs crossed at 7K in the back room on top of some Altec 416s but recently got some Aristocrats with EV triax which I listen to back here for now.

For grins, chuckles and personal edification I decided to stack the AMTs. Since I have them crossed at 10K I can't tell you how low you might take them. Also 1 pair has original diapragms and 1 pair new. I believe the new can take lower Hz but to my ears the old are a bit better at the top. Slightly different materials I guess.

I still have them stacked because I just haven't felt like getting the soldering rig in there and changing things back. My opinion is that the highs have become a bit sharper, or as I told a friend,"Like breaking glass."

I don't know if it is because there is twice as much area for producing highs, using 2 different diaphragms or what. I am not really answering your question because this isn't really an array and the bottom ones are head high sitting on boxes but there has not been any kind of improvement in presence, placement, soundstaging and to me just a tad bit of too much brightness.

I went to T.H.E. Show in Las Vegas a couple of months ago and listened to the new Oscar Heils which are 2 ways with the dipole AMT on top. I wasn't impressed. The AMT is smaller and the rest of the speaker seemed a bit slow, so it was a bit muddy.

Since these are dipoles and a lot of what you hear is bounced off the wall(s), I don't know if a stack rising from the floor would give you better imaging than just a pair. If you want to play around with these I would suggest that you limit the bandwidth on the ones close to the floor to mids and the ones on top to highs. These do have great mids, but seem to be best used only as tweeters. The diapragm life should be greater by not trying to get over 19Khz range out of them too.

I use a 300B SET stereo amp with a pair of isobaric subs running on SS for bass. AMTs are faster than ribbons, so matching drivers for speed as well as efficiency is important.