[steve f]

Question for Maggie experts. I was wondering about the moving mass of a MMG or 1.7 type of speaker. Cones always have a mms measurement. Is there an equivalent for planar magnetic speakers?

[GT Audio Works]

Hi Steve,
Not sure if there is a mms measurement for planars. The comparison of the two is apples to oranges.
Mms for a cone driver takes into account the weight of the cone as well as the weight of the voice coil, surround and spider as well as the weight of the air acting on the cone. A planar driver such as a Maggie has no surround or spider, and the voice coil is spread out linearly across the entire radiating surface of the driver. The magnetic engines of each drive operate differently.
A cone driver is heavier for its given area, but its motor design with its greater voice coil windings as well as its greater magnetic flux and tighter gap create a greater push with more excursion.
A planar driver has more area but the voice coil is spread out over the entire driver area. The number of passes or winding that lie between the gap between the magnets are much less, one or two in the case of the Maggies. The magnetic gap and the voice grids distance to the gap is much greater. This leads to less motor efficiency but the larger area of the driver and its greater area of driven surface is more efficient in translating the input signal to acoustic output. The larger diaphragm area couples to the air more efficiently along with the dipole operation and radiation pattern allows the driver to radiate the sound to the listening position more efficiently.
These advantages are thought by many including myself to enable the planar driver to outperform the dynamic cone driver.
Greg

[steve f]

Thanks Greg,

That follows my line of thinking too. I was wondering if a planar magnetic had a weight/formula range for the diaphragm to provide maximum performance. I never heard of one, and it may not exist.
I know the point is moot for ESLs as diaphragms weigh less then the air they work against.

Are you exhibiting at the California Audio Show?

steve

[GT Audio Works]

No...too far for me...I'm in NJ

[Roger Gustavsson]

Magneplanar type of drivers does not have a very low moving mass, like electrostatics. The low(est) frequency drivers have a moving mass of about 40-90 grams. The tweeters have higher moving masses than conventional dome drivers. The ribbon drivers have very low moving masses.

[josh358]

Thanks Greg,

That follows my line of thinking too. I was wondering if a planar magnetic had a weight/formula range for the diaphragm to provide maximum performance. I never heard of one, and it may not exist.
I know the point is moot for ESLs as diaphragms weigh less then the air they work against.

Are you exhibiting at the California Audio Show?

steve

Well, they still obey the same formulas, they're free air drivers with mass, compliance, electrical and mechanical damping, etc. However, the design trades are different. For one thing, you have a flexible rather than rigid diaphragm so adding mass to obtain rigidity isn't practical or necessary. So at higher frequencies, you essentially want the lowest mass possible to minimize unwanted resonances and have sufficiently extended frequency response past the crossover point.

At bass frequencies, dipoles are usually underdamped to compensate for the 6 dB/octave dipole cancellation. So you'd need enough stored energy for the acoustic dipole equalization.