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Apr 09 2014

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Horny Ribbons, MK II with Panorama

The achieved level of improvement is substantial enough to merit a separate blog entry, about a minor modification recently applied to the HORN-LOADED ribbon tweeters.
Below you shall find some photos of the the new arrangement, the one that made a hell of a difference.

P1110325 b

A fairly simple activity: simply just slide the two angular vertical reflective boards, the inserts, half way out of the wooden box frame, and adjust the angle between them, so that the new angle is much, much wider.

P1110327 b

Now simply push the Ribbon Tweeter into the “insides” of the box (with it’s temporary stand in the form of a crude box of matches). This is possible, as now you have automatically gained some free space from behind, so as to conveniently hide, or house, the ribbon tweeter within. This is possible, as a side effect of pulling the reflector boards as mentioned above “half way out” of the box frame.

P1110326 b

After such modification, the horizontal dispersion characteristic is now much much better, due to the wide angle of the vertical planes. Mind you, I am not talking about measurements. I am talking about ears. In case of any doubt: just simply

LISTEN, and thou shalt HEAR.

Now that I am starting to think about it, I wonder if it makes sense to glue them together with the box frame at all. Maybe just simply leave them, for the time being at least, in a semi-”loose” state (well, OK, they are not totally loose, due to the tight fit into the box frame. Actually, they are quite difficult to move), so as to allow for possible future experimenting with the angles or something. Or maybe some sort of axis with hinges, or something ? We shall see.

As for the vertical dispersion, the issue has sort of disappeared, it resolved itself …  by itself. Whatever the physical phenomena behind it, the problem is solved and the case is closed. So no need to worry about it now.

P1110324 b

Here are some photos of the current setup, and this configuration works best for me at this current moment.

Please note that it is extremely easy to “build” this thing and glue it together.

Simply take three of these boards:  1000 mm x 20 mm (or other) x 32mm (or other) pre-cut supermarket board, and slice them into twelve even lengths:  245 mm.

Why 245 ?  The reason is as follows:  4 x 245 = 980… Add to this 4 times the thickness of the saw blade: 4 x 3mm = 12mm. You end up with just about a totally used up length of the board, using 992 mm of it, with only 8 mm of scrap, or slack, whichever way you want to look at it.

With 12 even pieces, you have preliminary material to build 2 sets so as to test the concept.

4 pieces shall constitute the “box frame”.  Simply glue them together with “Pattex” for Wood.  A medium size carpenters clutch, or press, would come in handy for this.

The other two boards – you shall use as the vertical reflectors.

P1110323 b P1110323 b

The above mentioned inventory does not actually constitute a “full” list of all the wooden parts necessary, as you still have the issue of the lacking piece of wood, or board, to which you shall mount the ribbon tweeter, and then the tweeter, with the board, to be mounted either to the back pane, or, as within this new setup, inserted in some slick manner into the insides of the box frame.  I do not as yet have a ready idea how to deal with “THAT” specific technical detail, but I am sure that it is doable.

One thing is for sure. The final, missing piece of board will need to have a narrow slit cut symmetrically through its middle, of a width that is in-line with the width of the ribbon output channel. The ribbon shall be mounted for BEHIND of this board, so as to make a sealed tight fit, once we press this whole board into the insides of the framed box, so that it comes in good, sealed contact with the “neck” of the “horn”.

By no means am I talking about “very sealed” or or waterproof or something.

This is not a water tank.
A simple “press to fit and seal it off”  will be good enough.

P1110330 b P1110329 b

One thing is for sure. The final, missing piece of board will need to have a narrow slit cut symmetrically through its middle, of a width that corresponds with the width of the ribbon’s output channel.

In my case, each of the two tweeter mounting boards shall need to have the dimensions as follows:

Height = W = The standard width of the supermarket board, i.e. 200 mm in my case – no need to cut along this axis.

Width = W – ( 2 x Thickness ),

meaning the standard width of the supermarket board, minus two times the thickness of the supermarket board.

So in my case, the Tweeter mounting board would need to have a “standard” Height of 200 mm, and then, I need to cut a length equal to 200 mm – ( 2 x 16mm ) = 168 mm.

From this, I would subtract some 1 or 2 mm, just for the sake of making my life easier, when it actually comes down to inserting this mounting board into the insides of the box frame.

So it boils down to 200 x 166 mm.

Easy.

The ribbon shall be mounted from BEHIND of this board, so as to provide for an even front surface and a tight fit, one that seals off any crevices between this tweeter support board and the “neck” of the “horn”.   Once we press this whole mounting board, together with the mounted tweeter, into the insides of the framed box, it shall come in natural contact with the neck of the horn, one that is fairly reasonably sealed off, without any crevices.

By no means am I talking about “very sealed” or water-tight, or water-proof or something. This is not a water tank.  A simple “press to fit and seal it off, with no visible crevices”  will be good enough.

Cheers,

zjj_wwa

 

 

 

 

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