Origin of the 'Yuichi' horns - paging Steve Schell

[tomee]

Over on DIY is a thread about some very nice wood horns:

http://www.audioheritage.org/vbullet...396-Wood-Horns

In that thread the question came up about what design are these horns, with the response that they are a Yuichi horn. I realize we all call them Yuichi horns, I suppose because he wrote articles in MJ and now on the web describing how to build them. Some call them TAD horns, although I'm not sure that TAD used this design.
In any case, as far as I can tell the design dates back to at least the 1950s from Vitavox. I attached photos I've found for them. The larger picture is the Vitavox licensed Klipschorn, with the horn design in question (what do I call it?) on top. OswaldsMill audio has a picture of one here:
http://www.oswaldsmillaudio.com/vintage.html

I've been trying to figure out who and when this design first appeared. It's variant of a sectoral horn, with a 'Smith' type exponential (or hyperbolic) horn near the throat, becoming a traditional exponential (or hyperbolic) sectoral horn near the mouth. The design avoids the pinched top-bottom walls a sectoral exponential horn often has in the first third of the horn. I do notice that the Yuichi design does have slightly curved walls vs. the straight walls I think I see in the pics of the Vitavox horn. So far I've found the Vitavox pic as the earliest reference, but the origin may be much earlier - maybe Steve Schell knows?


Attached Images

[Steve Schell]

Tomee I really don't know that much about the Yuichi horns, so you sent me scrambling for info. I checked in with a friend who has built them in the past and he set me straight on a few aspects. He said he would check in here later and fix anything I forget or get wrong.

The Yuichi appears to be a modified form of what is known generally as a radial horn. Invented by John Volkmann of RCA, the radial combines the excellent directivity of a conical (straight sided) horn with the good loading of an exponential horn. In a classic radial, the horizontal pattern has very smooth response with minimal beaming due to the straight side walls. Directivity is compromised in the less critical vertical axis. The top and bottom walls are strongly curved, enough to create the exponential flare.

Typically a radial horn will actually neck down initially in the vertical axis. This is because the side walls diverge so rapidly that the other two walls need to neck down to maintain the cross section. In the Yuichi it appears that the vanes in the throat have enough thickness to maintain the cross section, allowing the top and bottom sides to be parallel in that area.

Many of the Yuichis have a hyperbolic flare rather than pure exponential. I can't speak to the math involved, but basically the flare is slower in the throat graduating to more rapid near the mouth compared to exponential. This affords increased loading at low frequencies and possibly a less severe impedance mismatch at the mouth. Robert Stephens thought so, as he used a similar flare for his multicellular horns.

[eso]

AS far as I know, Yuichi horns refer specifically to the horns designed hand build by Japanese audiophile Yuichi Arai. As Steve mentions below, he primarily used hyperbolic flares in very well designed radial horns.

You can learn all about his designs here, and even download drawing to build your own:

http://www.geocities.jp/arai401204/

In my experience he has always been very friendly and responds to emails as well, although he does seem to travel quite a bit and sometimes takes a while to respond.

The horns pictured in the photos in the lead post resemble some Yuichi designs because they are radial horns with vanes, but I doubt they are Yuichi designs. To my limited knowledge there have been no production Yuichi horns, only those hand built by the designed and those built by others from his plans.I have built a pair of the A290s and another member of this forum now owns them.

Here is one being crated for shipping:



eso

[tomee]

Tomee I really don't know that much about the Yuichi horns, so you sent me scrambling for info. I checked in with a friend who has built them in the past and he set me straight on a few aspects. He said he would check in here later and fix anything I forget or get wrong.

The Yuichi appears to be a modified form of what is known generally as a radial horn. Invented by John Volkmann of RCA, the radial combines the excellent directivity of a conical (straight sided) horn with the good loading of an exponential horn. In a classic radial, the horizontal pattern has very smooth response with minimal beaming due to the straight side walls. Directivity is compromised in the less critical vertical axis. The top and bottom walls are strongly curved, enough to create the exponential flare.

Typically a radial horn will actually neck down initially in the vertical axis. This is because the side walls diverge so rapidly that the other two walls need to neck down to maintain the cross section. In the Yuichi it appears that the vanes in the throat have enough thickness to maintain the cross section, allowing the top and bottom sides to be parallel in that area.

Many of the Yuichis have a hyperbolic flare rather than pure exponential. I can't speak to the math involved, but basically the flare is slower in the throat graduating to more rapid near the mouth compared to exponential. This affords increased loading at low frequencies and possibly a less severe impedance mismatch at the mouth. Robert Stephens thought so, as he used a similar flare for his multicellular horns.

Steve, thanks for getting back on this. I didn't mean to put you on the spot, but I thought that if there is someone who knows the originator or has a patent reference it's you. Along those lines, I'd like to dig further to see if the design was ever patented, and seeing as RCA developed the sectoral horn that's a good place to start the search.

eso, the horns in my first post are definitely not Yuichi horns or production copies of them, as they were produced in the 1950s through to the 1970s by Vitavox. My suspicion is that this Vitavox design is precursor to the well known TAD and Yuichi horns. I'd simply like to know who started it all, and when.
The one shown in your attached picture is stunning! Can you comment on the sound of them, compared to the round horns you list in signature line?

[Ian Mackenzie]

The actual designs appeared in MJ in the the 90's. If someone can obtain one of the articles and translate it l am sure you will find the answer. Or just ask Yuichi. He is VP of an IT CO and is based in Osaka and he travels to the USA regularly.

[Steve Schell]

I have heard that John Volkmann authored an article on the radial horn. This was probably published in one of the major journals of the 1940s, but I've never chased it down. If anybody finds the article or even a citing, please post it to the thread.

[tomee]

Well, I found a patent from 1951 that looks very close to the Vitavox/TAD/Yuichi design: US# 2537141. There are 2 extra struts or vanes, and the throat is longer, but it is essentially the same. Guess who wrote this one! (look at Fig 4 on the 2nd page)

http://www.freepatentsonline.com/2537141.pdf

[JeffW]

I'm not seeing all that much similarity. The top/bottom and sides of the 2nd one appear to be all flat, not curved. All the surfaces of the Yuichi horn that started this quest are curved.

[eso]

Can you comment on the sound of them, compared to the round horns you list in signature line?

The round horns that have been in my system for years have much more 3-dimensional imaging, but at the expense of a smaller sweet spot.

Those Yuichis sound superb, and because of their radial design they sound better off-axis. The same portion of the design that gives better off-axis performance is also responsible for somewhat flattening the soundstage.

Cool find on the old Klipsch patent drawings.

eso

[tomee]

I'm not seeing all that much similarity. The top/bottom and sides of the 2nd one appear to be all flat, not curved. All the surfaces of the Yuichi horn that started this quest are curved.

Hi JeffW,

The similarity I see is in the initial portion of the horn where the top and bottom walls are flat and parallel and have vanes inserted to maintain the exponential expansion of the cross sectional area up to the point where the vanes end, at which point the expansion is done with a smooth curve like the Vitavox/TAD/Yuichi designs or with flat walls and an additional horizontal vane like the Klipsch patent. So far I haven't found any earlier examples of this technique to maintain the exponential expansion in a radial horn. The 'Smith' diffraction horn (which is from the late 1940s?) is similar but uses vanes all the way to the mouth, which has parallel top and bottom walls throughout it's expanson right to the mouth.

This is all just design detail stuff that probably isn't important, but I'm kind of interested in this. I'm curious as to who first thought putting the vanes in rather than letting the top-bottom walls pinch down in a radial-exponential horn. I also find it interesting that people will build (or pay to have built) these wooden vaned-radial horns, yet Altec and JBL made non-vaned radial exponential horns by the thousands that are I sense are thought to not sound as good. I'm speculating there is something in the details about the pinched walls vs. the vanes that favours the sound from a vaned design. Maybe it's the wood?

This all started because I wanted to properly attribute the design to the originator. This goes along with my pet-peave about the name given to a bass-reflex design out there called an 'Onken' that is really a published Jensen design from the 1950's. For some reason it's never called a 'Jensen bass-reflex' on the internet but always called an 'Onken'. I don't know where that started (I'm guessing Sound Practices magazine) but I had the Jensen reflex cabinet plans in my collection for years, and then when the internet came along I find people building these big cabinets and putting Altec 515s or 416s in them and calling them 'Onken'.

[JeffW]

I see your point, but when I called them "Yuichi horns" in the referenced thread, I meant that they were built from drawings signed by Yuichi and (I believe) published under his name. I can't figure out what "MJ" magazine is, but his drawings also reference that publication with an '89 date.

Whether that means the description of building a reverse engineered horn section from wood, or if the shapes/vanes/dimensions are 100% his, I can't say. Seems like his liability would be pretty large if he published drawings under his name that were copied from somebody else's work. I would tend to think that while inspired by earlier designs, these designs are his.

Sort of like I can see the similarity between my car and the original Daimler - both have 4 wheels and an internal combustion engine. But I don't call my car a Daimler, even though it may have been inspired by the Daimler.

[tomee]

I see your point, but when I called them "Yuichi horns" in the referenced thread, I meant that they were built from drawings signed by Yuichi and (I believe) published under his name. I can't figure out what "MJ" magazine is, but his drawings also reference that publication with an '89 date.

Whether that means the description of building a reverse engineered horn section from wood, or if the shapes/vanes/dimensions are 100% his, I can't say. Seems like his liability would be pretty large if he published drawings under his name that were copied from somebody else's work. I would tend to think that while inspired by earlier designs, these designs are his.

Sort of like I can see the similarity between my car and the original Daimler - both have 4 wheels and an internal combustion engine. But I don't call my car a Daimler, even though it may have been inspired by the Daimler.

OK, I see your point too - and I agree. Woodybanks called them A-290 style horns, so I assume he followed the Yuichi design. If I built a set of horns following his plans I should call them Yuichi horns. If Yuichi worked out the profiles for the horns from text-book equations (I expect he did, rather than copy an existing design) and publishes them in MJ magazine then they're his designs. However, if I see a picture of a wooden horn with vanes in the throat area, is it correct to call it a Yuichi, a TAD horn, a Vitavox, or a Klipsch-type horn design, or just a "vaned radial [exponential] horn"? I like the generic term 'vaned radial' more then calling them a 'TAD' or 'Yuichi' horn, which seems to get used as a generic term to describe these horns whether the actual design is known or not. I don't think either originated the idea of a vaned radial - so far that looks to be PWK's idea, and used by Vitavox commercially for some time (over 20 years).

[tomee]

The round horns that have been in my system for years have much more 3-dimensional imaging, but at the expense of a smaller sweet spot.

Those Yuichis sound superb, and because of their radial design they sound better off-axis. The same portion of the design that gives better off-axis performance is also responsible for somewhat flattening the soundstage.

Cool find on the old Klipsch patent drawings.

eso

Thanks for that summary - very insightful!

[JeffW]

However, if I see a picture of a wooden horn with vanes in the throat area, is it correct to call it a Yuichi, a TAD horn, a Vitavox, or a Klipsch-type horn design, or just a "vaned radial [exponential] horn"? Not sure, but I like the generic term 'vaned radial' better then calling them a 'TAD' or 'Yuichi' horn, which seems to get used as a generic term to describe these horns whether the actual design is known or not.

I called the ones in the referenced thread "Yuichi horns", since that's the plans used to create them. "A-290" is the model number Yuichi assigned to that particular design.

I don't know what to call generic wood horns. I guess I'll cross that bridge when I get there.

One last point - if I called a 2" exit compression driver a "TAD-type driver" there would be hell to pay on this site!

Not if it was indeed a TAD driver. No different than calling a Yuichi horn a Yuichi horn.

But it's quite a bit easier to actually track the lineage of the compression driver. Plus, you'll notice TAD doesn't call their compression driver a "Bell Labs-style" or "Western Electric-style", they have model numbers assigned to them. Were their drivers influenced by Western Electric's 555? Absolutely (obviously with other contributors in between). Are they the same thing? Not really.

[tomee]

....
I don't know what to call generic wood horns. I guess I'll cross that bridge when I get there.

It's the use of vanes in the radial horn that I'm trying to track down. I don't care what it's made of.

I also didn't start this thread to correct you or counter your point about Woodybanks' horn in that other thread - sorry if it appeared that way. Just trying to track down the origin of some technical details in these horn designs.