High Efficiency Speaker Asylum

Posted by tomservo (M) on April 12, 2024 at 05:39:54

In Reply to: RE: Late 90's did the small driver large baffle, RadioShack FE102 ? posted by Edp on April 10, 2024 at 15:33:45

No need to wait, a lens is easy to explain if one thinks in terms of time.

Imagine a convex lens (thick at the center, thin at the edges), the velocity of light in the glass is slightly less than in air and so if one imagines a flat plane of photons entering the glass (an optical plane wave) , the thicker the glass, the greater that photon is delayed relative to the outer edges.

The light that exits the glass that entered as a flat plane is now a converging wavefront (coming to a focal point) with the "F" number being the ratio of the diameter to focal length..

With Sound on the other hand the velocity of sound in air only changes with temperature so using different materials to cause a delay is out but one can use a longer / shorter path lengths for that purpose.

Consider the potato masher lens or a slanted plate lens. Both of these deal with a horn that has a very narrow pattern up high, the lens progressively delays the edges vs the center and this produces a more curved wavefront (wider dispersion angle) at the exit.

The Paraline is a reversed situation the driver radiation is radial 360 degrees but easier to imagine if one had say 20 equal length tubes attached to the driver exit who's exit ends are lined up in the straight line. This way the sound radiates from all the tubes at the same instant and arranged in a "line". Now, imagine that there are no tubes and it is the equal distribution of pressure that causes the distribution.
Hope that helps.
Tom