There's a couple of versions floating around. One for 2" exit and one for 1" exit compression drivers.

I built a clone of the JBL 2397 horns and use them with my 2445 2" exit drivers. They're crossed at 800Hz to 15" 2235 woofers. The horns and drivers tend to rolloff just below 10KHz, so it benefits from a supertweeter. Can't really expect a 2" exit compression to extend out to 20KHz.

The small smith horn, dubbed "1200Hz Smith Horn" was designed for 1" drivers. You may have to rework the crossover, but this horn may replace the plastic horns used on Pi Speakers.

gar.

1) Most people own or use 1" drivers vs 2". Anyone using Pi speakers could most likely use the horn too.
2) 2" compression drivers are very expensive to buy if you don't already own a pair
3) I already have a 2" version of the horns

Colin, do you have a preference for front-loading or back-loading the work for this group build?

Front-loading would have the group pool some money together to design and built some tools to make the individual builds easier. Examples of tools include pre-fab vanes, cutout and router template, pre-fab throat adaptors.

Back-loading is if we do minimal upfront and let the individual builders build from scratch.

Gar.

If you haven't already, the link below contains a lot of information. Lots of measurements, but also lots of measurement issues. I think the "clean" measurements start on page 6 of the thread. Looking at the data, it seems to do a respectable job up to 16KHz. A compensation network similar to the one on your 4-PI should flatten that somewhat.

I've never built or heard this version of the smith horn, so I'm only going by feedback from the AudioHeritage guys.

Gar.

• 1200Hz Smith at AudioHeritage

From what you've described briefly, it seems the vanes are the most difficult part to construct. Is this true? Also, this is a very critical part of the dispersion mechanism. I would certainly like to see these CNC'd. Beyond that, what else would be terribly difficult for a novice builder? What about the throat plate? Are their commercial ones available?

I would vote for "back-loading" the work. MUCH less hassle.

......Colin