Magnepan MMG with ICEPower amplifiers

[justdhruv]

is there a reason, why the sweet spot should be this small.

I mean, a normal box speaker has almost a point source, for a tweeter, which fires forward. Where as the MMG has a line source, ( and hence the sound decay should much less, though decay may not have any thing to do with the sweet spot) and which throws sound at the back as well, so it should disperse the sound more than a normal speaker.

[JoeE SP9]

It's not decay it's horizontal dispersion. The quasi ribbon used in the MMG is actually part of the same diaphragm as the rest of the speaker. The horizontal dispersion is not very broad. It is better the further the listener is from the speakers. Unfortunately the smaller rooms they (MMG's) usually get placed in don't allow for "far field" listening. Get 10 feet away from some raised MMG's and the sweet spot is a fairly decent width.

IMO MMG's sound good even out of the sweet spot. They're just better in it.

The rear wave adds to the openness and depth of the sound. It doesn't help with the size of the sweet spot. The wall behind them (any dipolar) should be a mix of absorbing, reflective and dispersive surfaces.

[Feanor]

It's not decay it's horizontal dispersion. The quasi ribbon used in the MMG is actually part of the same diaphragm as the rest of the speaker. The horizontal dispersion is not very broad. It is better the further the listener is from the speakers. Unfortunately the smaller rooms they (MMG's) usually get placed in don't allow for "far field" listening. Get 10 feet away from some raised MMG's and the sweet spot is a fairly decent width.

IMO MMG's sound good even out of the sweet spot. They're just better in it.

The rear wave adds to the openness and depth of the sound. It doesn't help with the size of the sweet spot. The wall behind them (any dipolar) should be a mix of absorbing, reflective and dispersive surfaces.

I agree with Joe on these points -- and the MMG is a remarkable speaker for the money, though it isn't a "rocker".

Horizontal dispersion is limted by the width of the driver. The driver starts to "beam" when the wave length becomes 2x the width of the driver, hence for a 2" tweeter as on the MMG, the speakers starts to beam at about 3500 Hz.