Kirishima Horn Loudspeakers
Kirishima Double-mouthed Horns
Large double-mouthed rear-loaded horns. Design previously known as Sachiko. Build plans can be found at the Frugal Horn website.
These were built following the published plans, using the recommended Fostex FE206e full-range drivers (now discontinued). The drivers were EnABLE'd. This is a truly great speaker — efficient (96 db/W/1m), dynamic, natural, pin-point imaging, a big wall of sound yet subtle details are not masked. Bass fades quickly below 40hz - I'm OK with that. The cabinets are impressively large, very heavy, and really make a statement in a room. WAF rather low, however my wife soon noticed us having minor celebrity status: "Hi, I've come to pick up little Amy ... pause ... is there any chance I could have a listen to your husband's speakers?"
However (in hifi there is always a however) there was always a hint of "shoutiness" and the noticeable HF roll-off of the fullrangers. So I began to explore the idea of higher quality drivers, in particular the astonishing-looking Fostex FE208EΣ.
The Fostex FE208EΣ wide-range driver comes with the reputation of having a particularly good mid-range — smooth, and detailed. It has no whizzer-cone, and as a result high frequencies are rolled off to the point where a tweeter is mandatory ... actually a supertweeter. The cone is made from banana plant fibre: about 10 times as light as paper giving a very fast driver.
So I switched the main drivers for the Fostex FE208EΣ wide-rangers and added Fostex FT17H supertweeters.
This combination proved very frustrating. I was using a single in-line capacitor to blend in the supertweeter, however trying values between 1.5 and 0.68µF simply seemed to add a variable amount of harshness without the "air" that I had hoped for.
Supertweeters — butterflies sneezing!
Fountek NeoCD 2.0 Ribbons
I then discovered that the budget Fostex FT17H supertweeter has a major shortcoming — its FR falls away sharply above 15kHz (graph). Not so "super", barely even a tweeter — time to move on.
Much research later, a pair of Fountek NeoCD 2.0 Ribbon Supertweeters replaced the FT17Hs and the capacitor tests began again. This was a much happier affair, and I very quickly stepped from 1.5 down to 0.68µF. The added sparkle and air is startling, smooth and dynamic. The Founteks will be incorporated into the cabinets (there is room above the main driver) with Mundorf MCap Supreme capacitors.
It's good to be able to fine-tune the voicing on your speakers, particularly if tube-rolling. So after another bit of research, I acquired a couple of L-Pads. I'm using these to drop the volume on the Founteks a smidgin without hitting the frequency response.
This works a treat, I have been doing it entirely by ear. Turn up the Founteks and listen to a selection of tracks, admiring the sharp sparkle and exaggerated HF. Then find a big choral track (Bach Bm Mass will do nicely) – horribly thin with this setting – and trim back on the HF until the choir has a realistic "weight" to the sound.
This simple process works well, and has given me a setting that works with all the types of music I listen to. While it is tempting to measure the L-Pad resistances and replace each with a couple of resistors, I think I will build the L-Pads into the speakers to allow me to tweak the HF.
Alan Hope, Nov 2012