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My treasure – "Wrinkles like grooves brings audio wisdom" - 'Playing with speakers (Part 2)' By Otomeijin (Dec 16, 2005)
If you become an audiophile, you will come to think about trying and using various speakers. Of which, the horn SP was familiar to me through the school athletic meet. This is why a stereotype that the sound quality is kind of very horn(?) as commonly said got ingrained in my mind. So I had a little trouble understanding its use for HIFI.But I got concerned a bit when I thought there are many good things about it, such as the high efficiency of alteration in percussion sound and the good linearity for loud sound, and it's been utilized and developed for outdoor PA system or theatrical acoustics. It was by the Goto horn system I mentioned before in the issue 'A Salon in a Vision' when I first recognized how wonderful the horn was. The horn (handed down from my brother-in-law) I first used was Pioneer PT-3 and driver MU-20, MH-300 multi cellular horn SP. Here says "Cut-off 300-cycle (Hz). I remember that I used it a little while when I had a monaural system and for a few years when I had a stereo set. After that I kept it to deck my room with since it looked pretty snazzy. Let's see "fake/Kaitaishinsho" this time.

It's been carefully made of wood as you can see in the picture; the driver unit is pretty small, isn't it? The horn at the opening is 52cm in width and 24cm in height, and 8 cells made from plywood are being neatly arrayed. There are cracks everywhere now due to dryness. The body is painted in brown and black outside and gold inside. A floss silk has been put in the back of each cell to control the sound quality. And please do not separate the horn throat and the wooden part, where are fastened down by a thread, from each other since it is rusty and seems fragile.

The unit is 9cm in diameter. The throat is 22mm in bore diameter though; it would be like 1 inch since it says throat class 1. The diaphragm is probably made of some bakelite, which is far from fragile and won't budge an inch even if you flip it. Even the phonograph has a diaphragm looking like a wedge shape edge made of aluminum. So I remember that I got disappointed somehow after disassembling this one. As for the sound quality, I remember that the setting was difficult due to hog-backed type feature and the mediant was more like offensive to the ear (and sounded like clang clang). So I packed the above-mentioned floss silk. Because I got disappointed in the sound quality once and good-quality equipments like Goto horn was expensive, I moved on to the "playable" flat SP like I wrote before.

There is a 4-holed equalizer put in the mesh of the driver's screw mouth. The design is pretty rational since it will become separated into 2 pieces when the 4 assembly screws are removed. I put the felt that is pasted onto the magnetic field center pole for sound absorption. I wonder if this was effective. Well I only had this kind of ingenuity. A driver of today is equipped with a sound path and an equalizer on this pole piece side to improve the depth of the horn by reversing the sound(?).

The well-made horn won't create horn-like sound in the first place. It actually produces really unconstrained and soft sounds. Of course the devastating sounds from cymbals etc are sharp. Even if its directivity is high, that is not a big deal in a small room we usually have. After a lot of SP playing, I think that the horn is necessary for HIFI after all. Although my system consists of cheap stuffs now since I cannot still afford the (expensive) Goto horn, I am going to fully utilize all of such stuffs including equipments of my own making. If you don't mind me giving you some tips, you should introduce the horn type for as low sound as possible. Because the transient characteristic is good and the presence of sound improves leaving the sound energized. When I introduced the mediant-bass horn of my own making, I had to make sure if the sound was from the same system and replay the same CD over and over. And when I disassembled the Sunsui tweeter, which opened up an opportunity for me to work for this HiFi Do Online Newsletter, and turned one of them up to make sounds, the presence feeling of tweeter was gone as I expected. And the harsh feeling that I could hear a little bit became softer. The way of sounding seemed to have gotten wider. In addition, the sound became much mellow and matured when I put the elastomer resin under SP recently.


It's been 50 years since I tried this kind of God-knows-what (unscalable) things and these days I almost came to figure out the verisimilar soundscape. (In my opinion, although the flat SP is good, it has no advantage over the horn in terms of the stable sound volume and the sense of power.) And if I summarize, you should enhance a bass system with as large box or surface as possible even though you may face some residential issues. The bass supports the acoustic field. In most cases, the small system cannot express such an acoustic field. Anyway please get your kind of acoustic field even if you have to take a lot of trial and error. I think you can take it easy just as I did. I will write about a guidance(?) of making the horn in the final issue of this year on December 30. So please look forward to it. To be continued.

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