K horn backs

[HIFI4EVER]

Hello,

 

I am looking at putting some backs on my speakers.  

 

Why do some K horns have side grills that go all the way to the floor and some like mine have notches in them at the bottom?

 

For the backs what is the stock paint used?

 

Do people use nutserts or just screws?

 

 

[Coytee]

I thought they all had notches to allow them to fit around any wood trim that might exist on the floor?

 

Be interesting to see what those in the know have to say.

[HIFI4EVER]

I'm thinking the photos I seen are of sealed backs, meaning... '60's/'70's.

[rplace]

12 hours ago, HIFI4EVER said:

I'm thinking the photos I seen are of sealed backs, meaning... '60's/'70's.

 

Just a bit of info incase you are not fully up to speed. Apologies if I'm telling you what you already know.

 

Khorns have been around for along time ('46 IIRC). The sealed backs are relatively new starting with one of the anniversary versions (70th I think). Lots of info if you search a bit on sealing the backs on a pair that does not come from the factory that way. I'm not aware of anything form the 60/70s that came from the factory with sealed backs, but I could be wrong. Others will surely chime in if I am.

 

The side grills are purely cosmetic and those notches are in fact to clear any baseboard trim or molding. That said on standard khorns (not sealed backs) the "tail piece" which runs vertically and touches both walls when snug in the corner is also notched. Various years of khorns have different things, like weather stripping, on that tail piece to make a tighter seal to the wall and thus make the last part of the horn more complete. Many use different materials like pipe insulation to get a better/tighter seal where that tail piece meets the wall. I personally doubled it up in the notches and think it helped. YMMV. While I've not sealed the backs on my 87 khorns I've concluded most who have retrofitted theirs are more than happy with the results. I'm not 100% clear on if you need to extend the top/bottom of the khorn prior to making your sealed backs to function like your wall would or if an approximately 3/4 inch reduction in volume all around by putting your backs "inside" matters. I'd like to hear more thoughts on that myself.

 

There is a completely different approach referred to as False Corners, but I don't think that is what you mean. A search of that will yield many results if you are curious.

 

Hope this helps!

[profsbg]

If you use weather stripping or double up on pipe insulation in the notched area is the seal good enough to not see a flashlight beam directed through the notches?

 

Most implementations of pipe insulation on the tail pieces that I have seen follow the edge , and do not double up at the notches . Hence the notched area is not really sealed, assuming no baseboard trim or molding. Naively, I would guess this significantly affects the seal and possibly the output, assuming proper output requires a good seal.  Yet it is popular to use the pipe insulation this way.  Any thoughts or data on this? I have a crude measurement rig but I am not very confident using it.

[HDBRbuilder]

The Klipschorn "tail-board" is actually a reflector of the upper and lower bifurcated horn lens pathways just ahead of it, and those two pathways JOIN on the FACE of the "tailboard" where they again become LEFT and RIGHT bifurcated pathways when reflected forward to each side of the bass bin.  The "notches" were added so that the baseboard moldings used at the time the Klipschorn was designed would not NEED to be removed in order to fit the K-horn into a room corner.

 

Having those notches to begin with are just a consumer "convenience", but not really necessary nowadays, IMHO, because so many homeowners nowadays have the ability to custom-cut any notches needed on the tailboard by using all manner of tools readily available which originally required a coping saw to cut at the time the Klipschorn went into production.

 

Almost anybody can get a pretty tight fit of a factory-NOT-notched "tailboard" by using, for instance, a Dremel tool to make the notches needed for a custom fit of the tailboard to the molding used in the corners in which they intend to put the K-horns.  A dremel tool with appropriate bits, some sand paper, and some touch-up black paint, and you are done.

 

The notching, if needed, could even BETTER be done by whomever is installing them, if bought from a dealer new.  The only problem is that if they ever get put into another room/house, with smaller baseboard moldings, then there would be gaps to fill from the earlier notching which was already done.

 

I would be VERY INTERESTED in reading about some K-horn owners' efforts to seal a K-horn bass bin to a room corner whose walls are stone or other masonry, such as brick.

 

It may well be one of the more humorous posts about the task if well-written. 

 

Even funnier might be how the bass itself coming FROM the bass bin in a corner of masonry walls, especially STONE masonry, was affected by the soundwaves being forced through a bifurcated pathway which was relatively smooth on the bass bin sides and rough on the masonry sides...there would simply HAVE TO BE some difference in what your ears pick up, I am sure.

[HIFI4EVER]

I think the photos I was seeing are of kits r people that modified their khorns.  I am aware of the factory sealed backs.

 

I am looking at having a new tail board, bottoms and  backs made.

[HIFI4EVER]

What kind or grade of plywood is usually used?  

 

What is the stock black color?

[WMcD]

A lot of questions.

 

By nutsers I believe you mean the brass device which has a bore to take a machine screw and a coarse threaded outer.  I tried them a few decades ago when I made 3/4 ply SK's with backs  It was very difficult to get the nutsers square into the edge of a 3/4 inch piece of ply, and get everything to line up.  I eventually gave them to my nephew. He could not keep them and eventually they were donated to a church group in Texas.

 

A long time ago I took a look at the claims for the K-Horn patent.  U.S. patents are not required to point out the "point of novelty."  But in many claims it appeared to me that it was that the walls of the room were part of the structure but independent from the horn.  Therefore a K-Horn with a built-in back was not covered by the patent and to some extent would avoid it. 

 

Of course the patent term ended and PWK did not market a closed-back unit even then  Rather, he present the artificial corner.  I can't help but think it was an inventor's pride.  Also, some clever fellow even at the start could put a closed back on K-Horn and challenge him to sue.  Essentially, if PWK put a back on his K-Horn, it would not be his patented K-Horn.

 

It seems to me that the build of the K-Horn would have to work with base boards in those days.  However, baseboards are not used in modern construction too much and the theory that an external trihedral wall structure is needed for patent protection, or right to sue, was long gone.

 

I'll point out that the Jubilee has a sealed back and no cut out for base boards.  So to with the newer K-Horns.

 

WMcD

 

WMcD

 

 

[Schu]

Wouldn't a enclosed back, that supports PwK's original intent, need to extend well past the plane of the front panel?