CNC Throat conversion project & questions

[Dingusboy]

I own and regularly enjoy a pair of Yuichi 290 horns driven by 2445 drivers with the Brush Wellman Be diaphragms.

I bought the Horns from a regular contributor here. He did a great job on the build. The transition piece he made is well done but not exactly as smooth as I would like as it transitions from circle to rectangle. I recently ran some 3/4" Baltic birch plywood to come up with a smoother transition.

The Yuichi has a rectangular throat that is 2.25 x 2. I simply lofted between a 1.95" circle up to those dimensions vertically 3/4". I'm very happy with the results from a physical standpoint as both sides mate with their respective components with virtually no play.

For some reason, I was convinced Yuichi had used a 3/4" transition piece. But no, my memory fails again.

Yuichi used a 1" piece on his design. If someone might chime in and tell me if that 1/4" will be signifigant, I'd appreciate it. It would be some work to make it thicker but not radically difficult.

Any other comments/suggestions on how to improve upon the design are very welcome.

[JeffW]

I like it! I blended mine best I could with a half round file and emory cloth, but it's not nearly as smooth as yours.

If you want to sell a pair, shoot me a PM.

[lowpoke]

@Dingusboy
Has the smoother/cleaner transition made any audible difference in the sound?

[reVintage]

Why not go for the same flare in the adapter as the horn as this would probaly be the smoothest. This is easily calculated as At and Am is known and should theoretically be close to 1,5" length for 290Hz. Making it shorter will reduce low-end response. 1" will give over 400Hz. But it might not alter response that much as it is a very short piece of the whole horn.

[spkrman57]

Count me in when you start doing custom requests!!!

Regards, Ron

[Steve Schell]

Nice job, Dingusboy. I've had to deal with the round to square (or round to rectangular) transition many times. Most often I fill the throat with bondo, dragging a stick or dowel that contacts both surfaces at the same time to establish the profile. I suppose this creates a conical (straight sided) flare throat, but this is often the type of horn I am building anyway. The distance between round and square is determined by calculating the increase in cross sectional area and over what axial distance this increase should occur to maintain the flare expansion. Most important IMO is avoiding any voids or abrupt transitions which might create diffraction and/or reflection.

[reVintage]

Most important IMO is avoiding any voids or abrupt transitions which might create diffraction and/or reflection.

So true. Unfortunately we will have an extremely abrubt transition horisontally in Dingusboys radialhorn. So one should take take a closer look at 2328 where this has been delt with like it should.

As you(and I above) also say, the flare should be the same for the horn and adapter, in this case 4,2cm for Hypex T=0,8 and 3,5cm for Exp.

[JeffW]

So true. Unfortunately we will have an extremely abrubt transition horisontally in Dingusboys radialhorn. So one should take take a closer look at 2328 where this has been delt with like it should.

As you(and I above) also say, the flare should be the same for the horn and adapter, in this case 4,2cm for Hypex T=0,8 and 3,5cm for Exp.

The Yuichi horn is based on the TAD TH4001, and Yuichi made his adapters similar to the TAD aluminum adapters (I have a set of the TAD aluminum adapters). Granted they were pretty rough compared to the CNC aluminum TAD adapters, the CNC wood adapter Dingusboy is making is much closer to the style of the TAD aluminum adapter.

Now whether TAD should have fashioned their adapters differently is a different question, but the lowest recommended cut off is ~600Hz on these horns anyway.

[reVintage]

The Yuichi horn is based on the TAD TH4001, and Yuichi made his adapters similar to the TAD aluminum adapters (I have a set of the TAD aluminum adapters). Granted they were pretty rough compared to the CNC aluminum TAD adapters, the CNC wood adapter Dingusboy is making is much closer to the style of the TAD aluminum adapter.

Now whether TAD should have fashioned their adapters differently is a different question, but the lowest recommended cut off is ~600Hz on these horns anyway.

That TAD did them this way isn´t a guarantee they are made perfect. Why copy, find out if they can be made better instead.

A 290Hz horn is usually crossed over at about 2*Flow( Altec 515 is 270Hz and used from 500Hz). But this should in my opinion go for the adapter too, as it still is part of the horn.

Dingusboy, I suggest makes another that is theoretically correct for comparision.

It would also be interesing to find out how correct the other figures are in the horn.

[spkrman57]

That TAD did them this way isn´t a guarantee they are made perfect. Why copy, find out if they can be made better instead.

I believe that is the basic reason for this thread is to determine what is the best way to make the throat plates.

Regards, Ron

[Allanvh5150]

CNC mill. It would take about 3 minutes!