Theatre 4Pi

Brendon Lees, Wayne Parham's Theatre 4Pi Loudspeaker Build.

imageIn this article Brendon Lee gives a description of his build and listening impressions of the 4Pi Loudspeaker kit.  This kit is available here for a princely sum of $380 dollars.  Comprising of a 15’ woofer and horn tweeter, this kits background is routed in the PA market both in parts count and appearance.

The original design was by engineer Wayne Parham, the kit components can still be purchased here.

This article is republished with kind permission of Brendon Lee and was originally published on his Geocities website.

Completed without using the stock Eminence PXB-1K6 High Pass Crossover.

The speakers have come alive after extensive bracing and re-doing the passive crossover and hook-up wires.

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My 1st attempt with building the speakers resulted in poor sound quality as I ran them without any bracing. The photos should give a good idea of how they look inside un-braced.

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Rear edges are routered so the rear baffle board fits flush. However, part of the poor performance may be that the rear baffle board is not secured enough.

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The H-290 horn flare had to be drilled formed so that the hex bolt would fit through the stock hole. I don't imagine how other users would of got around this design flaw without carving it.

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My 1st attempt to wiring the crossover. I've pulled all of the guts out and replaced the inductors and resistors that are of lower wattage.

I've also gone with regular multi-strand 12 gauge copper wiring as the solid core wires muffled the sound.

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Fully revised xover. Resistor sets are only rated 20 watts which is more than enough for my SoZ amp. C5 is 15uF instead of the 20uF others have been using.

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I can't stress the importance of bracing. The braces are Douglas Fir and are 1" x 2" top/bottom side/side and 1" x 1" on front / back. Taking a closer look and you can see where the braces are glued and crossed over. The rear baffle board is also glued up. Note that the solid core wire has been replaced. I would love to experiment more later with different hook-up wires but will be patient.

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Not what you would really call an audiophile room. The sound is just what I expected from horns - quick, dynamic and sound incredibly clean when played at higher SPL. What I've noticed is the bass seems to keep up with the horn driver when I turn the volume up ; something I find that many smaller speakers can't do.

I should add though the bass at normal listening levels isn't too pronounced - possibly lacking for most listeners. May need more compensation on the PSD-2002 driver? Maybe the bass response may improve as they break-in.