Planar speaker characteristics

Hi all.

I'm new here. I have owned and operated a small Pro Audio company in NZ since 1973. My forte is R and D and product manufacture but this became very difficult for any NZ Prosumer electronics company way back in 1985 when our govt moved the goal posts in a draconian manner, thus destroying manufacture as we had always known it. Such was their utter stupidity as they could have done things differently in a way that could have worked for everyone involved.

However, since then I have engineered a 6 neo magnet high frequency planar driver, primarily for high performance applications but shelved it prior to the Covid saga for various reasons, one of which were problems acquiring a suitable diaphragm material. We initially tried DuPonts Kaladex which although did tick some of the boxes, the mass was to high and the product rolled off at around 17kHz. I have since reviving this project, learned that ideally we should be testing polymer film, gluelessly laminated to aluminium foil, at 25 x 25 microns. Glue melts which is why its not wanted. High temperature resilience is essential to accommodate the very high SPL's these things produce. Can anyone collaborate this material type and point me in the direction of a suitable supplier for this or equivalent material please? Any assistance would be much appreciated. Please ignore this post if you haven't a clue what I'm talking about.

@dprincipato: As a long-time owner/listener of planars (both magnetic-planars and electrostatics), I think you should know that the number one rule for owning them is that if you are not able to place them 5’ or more away from the wall behind them you may be better off with non-dipoles. If you have the 5’ available, read on!

Tall line source loudspeakers do a few things most point source designs don’t: image height and scale. Voices are reproduced at life-size height (mouths are roughly 5’ above the floor), and instruments as full-size images. With many box-enclosure loudspeakers you are looking down upon the singer(s) and instruments, as if you are listening from the balcony. And large instruments (grand piano, drumset, etc., as well as the huge image of a full symphony orchestra) are miniaturized. With non-planars the image appears to be squeezed through a hole in the front wall the size of the loudspeaker enclosure. With planars the singers and instruments are just hanging in space. Planars sound more "open" than many non-planars.

But planars are not without their own problems. Being dipoles, the planar rear wave creates a situation non-dipoles are less subject to: comb filtering. The rear wave travels back to the wall behind the planar, is reflected off it and travels back to the panel, where it interacts with the front wave. That interaction can cause all kinds of phase problems, resulting in peaks or dips in frequency response. Planars can take some experimenting with positioning to optimize. But what loudspeaker doesn’t?

On the other hand, planars have an inherent advantage over non-dipoles because of their dipole radiation characteristics. The front and rear waves are of opposite polarity, so when the two waves meet on either side of the panel, the waves cancel each other (+1 plus -1 = 0), creating a "null" on either side. With no output in that left-to-right plane, dipoles create fewer room modes (resonances). And planars may be placed closer to side walls than can non-dipoles, as those side-panel nulls result in less side-wall reflections.

Planars often also sound less like a combination of various drivers (woofer, midrange, tweeter) than do non-planars, as all the planar drivers are almost always of a very similar if not identical nature. And planar crossovers are usually far simpler than most non-planar designs, often just simple 1st-order filters. That enables planars to create sound more consistent top-to-bottom than most non-dipoles. As the pianists hands move down the keyboard, the timbre of the piano remains consistent. "Cut from the same cloth", as the old expression goes.

Magnepans are often the only magnetic-planar design mentioned in discussions about planars, but they are not the only ones. Eminent Technology presents some stiff competition with their LFT loudspeaker, which I recommend checking into. Some LFT-8b owners are former Magnepan MG3.7 owners; it’s that good, and for half the price. And, the LFT-8b modulus-of-impedance is much more tube amp-friendly than are Maggies. Maggies are a 3-4 ohm load, the LFT-8 ohms. And if you bi-amp, the m-p panel itself (with reproduces 180Hz to 10kHz, with no crossover!) is an 11 ohm load, great for tube amps.

@bdp24 

This is an old thread but your post should be a sticky. You covered a lot of ground just perfectly.