Volti Audio - 2015 Klipsch Khorn Restoration
4.2015 - By Greg Roberts
A few years ago I got an email from someone here in Maine asking if I'd be interested in buying an old pair of Khorns. They belonged to his father, who had just died a few months earlier, and the family didn't know what to do with the "monstrosities". I bought them for a few hundred dollars, figuring I could do something with them someday. Well now that day is here.
They were in very rough shape to say the least, but I didn't care, I knew I was only going to need the raw bass horn carcasses for my project.
My plan is to "build up" new Volti Khorn speakers off these raw bass horns. I'm going to enclose the backs of the bass horns with plywood to form the outer part of the final mouth of the bass horn, something that is normally the corner walls of the room they are in. Using braced plywood instead of drywall as the mouth of the horn will provide a stiffer sidewall to the horn, and a better defined upper bass sound.
Enclosing the backs of Khorns is not a new idea. Klipsch did this on their 60th anniversary model Khorns, and I've done it on a couple of pair to date. I got a chance to test the difference with a comparison between the "FLKhorns" and my own Khorns back when I did the "FLKhorn" restoration. Both sets of Khorns had exactly the same components. The only difference between them was that the "FLKhorns" had enclosed backs and mine didn't. The difference in sound quality was clearly heard. The enclosed backs really helped the upper bass definition, something that is somewhat of a weak point with all Khorns.
I believe that properly enclosing the backs of Khorns means NOT making the horn smaller. If I were to install 3/4" plywood "within" the outer limits of the existing cabinets, that would mean the last part of the bass horn mouth would become smaller by that 3/4" thickness. I think the better way to enclose the backs is to attach the 3/4" plywood to the outside of the existing cabinet structure, which maintains the exact horn size. But this means that the cabinets "grow" in size by the thickness of the plywood used, and then the tophat pieces need to be made larger to keep everything fitting tightly into the room corners. See the "FLKHorn" restoration webpage for more info.
So as I thought about the work that I did before to increase the size of the existing tophat pieces on the "FLKhorns" and the end result of adding those pieces on and how they "shadowed" through the veneer, I made the decision to simply make new tophat pieces for this project.
When building enclosed backs for Khorns, the existing side grill frames are no longer usable and new frames need to be made.
I'm planning to replace all of the old components with new Volti Audio upgrades.
So as you can see, taking this all into consideration, there was no need for me to save any of the components, the tophat cabinetry, or the grill frames. From this point on, it's all a new speaker build with all new tophat pieces, new grill frames and cloth, and all new Volti Audio upgrade components. Should be a very nice set of Khorns indeed.
First day of the project and I took the woofer chamber doors off, the woofer motorboards out, removed the felts on top of the bass horns, removed the metal feet from under the bass horns, and then removed the front trim pieces, which are screwed on from the backside before the cabinets are assembled, so there's no way to get to the screws.
After pulling the pieces off, I used Vise-Grips and broke the screws off, then drove them down in a bit with a hammer and punch.
The tailboards are easily removed.
I used an iron to soften the glue and then a putty knife to take the edgebanding off. Then the cabinets were sanded and areas that needed repair filled with epoxy.
After a couple of days, I sanded these filled areas and re-applied epoxy to fill in gaps. Sanded with a random-orbit sander, 80 grit disc. I had to remove some of the pan-head screws from the cabinets to sand these areas flat.
First coat and sanded
With past Khorn restorations, I've spent a lot of time trying to flatten and smooth the plywood sides of the cabinets, and with mixed results. The plywood used did not have a smooth face, and the grain lines are raised significantly. I never was able to truly smooth these sides out, and in the end, I think the results were not worth the time spent trying. So on this set, I'm only repairing the large chip-outs, holes that I don't need, screw holes from the front trim pieces, and missing edge pieces. Once it's all painted it will look fine. Don't forget, these sides are not seen anyway, except when the owner takes the grills off.
Other than a little sanding of epoxy, the next step is to start cutting plywood. But first, I'm heading to Chicago and the AXPONA audio show where I'll be showing the Volti Audio Vittora speakers. So I won't be getting back onto this project until the end of April.
AXPONA was a very good show for Volti Audio, and the "hole" in my schedule that occurred just a few short weeks ago has closed up in a big way. More work than I can handle at the moment. No complaints though.
During the last few weeks I've been able to get some more work done on the 2015 Volti Khorns. Here
you can see I've cut some 3/4" Baltic birch plywood for the tops and bottoms of the cabinets.
By adding plywood pieces to the tops and bottoms, I'm increasing the cabinet strength while also providing good connection points for the vertical pieces of plywood that will enclose the backs of the cabinets.
Note how the plywood does not extend all the way to the outer edge of the front plywood panel. This is to allow space for the side grills, which will butt up against the edges of the new plywood being installed. I had to decide whether or not to cut the plywood panel so that it went to the outer edge of the front panel and then cut out the necessary piece so the grills would fit, or, to cut the panels back as shown and later install blocks to fill in the top part of the front panel. This is hard to explain, but will be more understandable when you see the photos coming up. Obviously I chose to cut the panels smaller and add the little blocks.
Lining up the top bottom pieces is not as easy at it may seem. The original cabinets are not
perfectly square, and that has caused a small bit of misalignment from the top to bottom panels. But
we'll make it work. Here you see the tailboards in place.
Note where the top/bottom panels stick out from the side of the cabinet. This is the profile of the final horn segment in that area. In other words, this is showing where the corner walls of the room would be, with the cabinets tight in the corners. The plywood that is sticking out gives us the shape and dimensions needed (template) for the braces that will be installed between the side of the cabinet and the new side enclosure pieces we are adding. Sorry I don't have a picture of the braces, but in this next photo you can see the side pieces installed with one of the two braces that will be on each side of the cabinet. All plywood is glued with Premium construction adhesive, which is a polyurethane based glue that has a tenacious hold, as well as the ability to fill gaps.
As we're doing this work, you can really feel the cabinets getting more ridgid, denser, heavier.
I also cut all the tophat pieces from 3/4" Baltic Birch plywood.
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