Since Steve introduced the readers of the forum to the Lii Audio F-15 drivers, it has pretty much turned the loudspeaker world on its head and caused a large number of music lovers to rethink what is possible ..... especially when used with low powered vacuum tube amplifiers.

I have sold quite a few pairs of my low profile open baffles with the F-15 drivers and there has been a lot of interest in the DIY community as well.

Of course, it would be expected that a 15" driver would be able to make some decent bass and have a fine lower midrange response ..... but these drivers also have a very nice upper midrange and even a very respectable high frequency response ..... with a good amount of air.

I am fond of saying that the numbers don't always tell the entire story and that is true of these drivers. The specs are 50 HZ to 15K ..... but the music is all there .... at least to my ears and the ears of most of the folks who have lived with them.

I originally concluded that the whizzer cone and the phase plug were responsible for the unexpectedly good performance in the upper frequencies ..... but something happened a few days ago that has convinced me that there is more to it than that.

If I wasn't such a klutz, I probably would have never discovered this .....

I was finishing up a pair of baffles to ship to a customer and was leaning over one of the F-15 drivers while inserting a #2 Phillips head bit in my cordless drill. I will blame the following on a "senior moment" and the next thing I knew the bit slipped out of my hand and landed on the cone of the F-15 driver .....

Sure enough ..... the bit actually punctured the cone .....

After I recovered from a nervous breakdown, I examined the cone and discovered that it was thinner (actually MUCH thinner) than I would have expected it to be in a driver of that size.

In my humble opinion, the thickness (or rather the lack of it) of the cone is going a long way in contributing to the speed and seamless response into the upper frequencies. The whizzer cone is also much thinner than it appears at first glance.

It is apparent that the engineers at Lii Audio are some pretty savvy guys (or gals) and a lot of thought has gone into the total design of this driver .....

Well done .....

Randy

BTW ..... I exchanged the "damaged" driver for one in my personal pair of baffles. A little dab of silicon cement on the back of the cone sealed the small torn spot and there is no noticeable degradation in the sound.
I can live with that .....

Unfortunately there are lots of horrific things going on in China so I get where you are coming from. That said there are many solid companies with healthy work environments in China. Who employ skilled craftsmen and tradesmen who earn good wages.

My limited dealings with Leo (the founder and designer) through email, He is a stand up person who treats everyone fairly.

Yes Randy, the cone is deceiving because of the fold at the top of the cone.  Originally I thought the paper was like 1/8" or something, but its really much much thinner.

This is why I put grills over my F15s.   So no