High Efficiency Speaker Asylum: RE: Good ole John Karlson by bb2 Need speakers that can rock with just one watt? You found da place.

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Posted by bb2 (A ) on July 24, 2013 at 01:36:10

In Reply to: RE: Good ole John Karlson posted by freddyi on July 24, 2013 at 00:51:25:

Yes, instead of doing a number of slots as in the original deisgn I opted for two 70mm holes with the same area. An earlier contruction taught me, that at low levels you could hear the air hiss in the slots. Bit of an experiment but it worked out well.

One good indicator for success is the fact, that cone excursions for the woofer are very small compared toma bass reflex att the same ksound pressure level. These two are *very* efficient. After playing them loud for a few hours it is already apparent, that the 200Hz hump is flattening out somewhat: the woofers were brand new and need playing-in time. Much better now.

Another difference between previous experiments and the present: Insted of using Nitro paint for the inside of the boxes I used a two-component epoxy varnish (messy) resulting in a very hard surface, nearly as hard as the Acrylic curtains: The harder the inner surface, the less resonances. The epoxy varnish is of the type used on concrete floors in industrial environments.

When time permits I shall do some measuring and publish the results. I am sure there is room for mprovement, but the results sofar confirms the thesis: the best of educations and years of experience cannot replace pot luck...

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