60th Khorn-style backs revisited

[mr-b]

Hi

I'm interested in doing the 60th Anniversary Khorn-style backs
project for my '87 Khorns and wondered if anyone else had done this and if they had any tips on construction?

The original thread
http://forums.klipsch.com/forums/thread/843664.aspx seems to be
locked. :-(

I've got the spec for the wood i.e. 4' x 8' of Baltic (Russian/Latvian etc.) Birch ply at 3/4" (although this seems very hard to source as a single sheet in the UK) - but I'm lost on things like screw size/number, fixing positions, construction process etc.

I showed my carpenter friend the thread pics, but they don't seem to have enough detail for him.

Has anyone else done this project?

[RFP]

Mr. B<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

I believe that Forum member wallflower did this very thing not very long ago as I recall, he collaborated with a woodworker friend to do the job (just as you will?), and is pleased with the result. You might want to contact him through a private message.

I'm sure that others will jump in on this, too...

Cheers,

Rob

PS: Where in the UK are you?

[DrWho]

I showed my carpenter friend the thread pics, but they don't seem to have enough detail for him.

He's probably thinking about it too much.

All you need to do is create the equivalent of a room corner. Fastening it to the khorn is merely a process of finding good places to put screws. I would hope your carpenter friend would know how to do that []

The only concern is that you maintain an airtight seal along the tailboard in the back (where the wall would normally come into contact). Don't worry if the wood doesn't line up perfectly because you can just seal it with caulk or liquid nails or whatever you want to use. The wavelengths in question are too big to care about any minor imperfections.

[gaspr]

If I recall correctly, most who have done this mod have replaced the

existing tailboard with something more substantial. I think

that most have filled in the bottoms as well.

[mr-b]

He's probably thinking about it too much.

Heh - well actually I'm glad it's not the other way round! I want to minimise the use of glue/caulk etc. if at all possible so I can return it to near-stock if necessary. I wouldn't know what to do about the holes though. Also my friend doesn't know the intricacies of khorn construction so I'd hope that some ppl here would know of any potential pitfalls. I really don't want to be guessing on this.

Yes, the thread's pics at http://forums.klipsch.com/forums/permalink/843664/839729/ShowThread.aspx#839729 show the tailboard as being replaced.

However we found it hard to gauge from the pics how the sides meet the new base blocks or how the new bases and braces are fixed to the existing base.

[wallflower]

I've got lots of pictures of the process and some words of advice to share. It would be easier to talk over the phone. Send me your phone number in a PM and we can talk.

Regards,

Jeff

Edited...

I just realized you're in the U.K., so I guess we'll need to communicate via email, unless you want to coordinate a time to call me.

Jeff

[greg928gts]

I would recommend polyurethane construction adhesive as well as screws to attach the plywood. This will eliminate unwanted buzzing noises. Since you want to be able to return yours to stock someday, maybe you could use a thin, adhesive backed weatherstrip wherever the plywood will contact the cabinet.

Greg

[Guest " "]

"well actually I'm glad it's not the other way round! I want to minimise the use of glue/caulk etc. if at all possible so I can return it to near-stock if necessary"

Well, if you want to minimize cosmetic issues to your bass bins........use the method I used during the 80's.

1.) cut 4 pieces of wood in the shape of the top section, 2 for each cab.

2.) cut out 3 vertical pieces of wood to fit the left side, area behind the tail board and the right side of each cab, but make the lenths about 1/8 of an inch higher.

3.) assemble the vertical panels onto the tops and bottoms you cut out in step 1.)

4.) slide you bass bins into the assemble, put you top sections on top.

[gaspr]

"well actually I'm glad it's not the other way round! I want to

minimise the use of glue/caulk etc. if at all possible so I can return

it to near-stock if necessary"

Well, if you want to minimize cosmetic issues to your bass bins........use the method I used during the 80's.

1.) cut 4 pieces of wood in the shape of the top section, 2 for each cab.

2.)

cut out 3 vertical pieces of wood to fit the left side, area behind the

tail board and the right side of each cab, but make the lenths about

1/8 of an inch higher.

3.) assemble the vertical panels onto the tops and bottoms you cut out in step 1.)

4.) slide you bass bins into the assemble, put you top sections on top.

Wow Fritz, what a great idea. You could even turn a C style k-horn into a B style using your method...I like it.

[Guest " "]

gaspr

yeah, it looks professional as well.

[tk49]

mr-b, I'm the woodworker that did wallflower's mods. If you want, your woodworker can contact me, I'ld be happy to visit with him/her.

Using a tablesaw is a must for a good fit, you can get your patterns and angles off the top hat. The tail piece was the only part that required some modifications. If you are willing to mod the horizontal base bin pieces then the tail piece attachement is relatively simple. I found that their attention to detail/fit on the tail piece was'nt as great as the nice cabinet work on the front.

As far as fitting the tail piece to the false walls we found that a closed foam sealer that is used between pickup toppers and the truck bed worked excellent. It's about 1/4" thick and has addhesive on one side.

Let me know if you have addition questions

Tom

[Kudret]

Tom,

Shipping would probably be too expensive, but would you consider selling these as kits for those who are less talented when it comes to woodworking?

Kudret

[mr-b]

gaspr

yeah, it looks professional as well.

Interesting! So these are false corners but with their "wings clipped"?

Got any pics?

[JBryan]

This may not apply to you but I made the old-fashioned wings similar to what PWK described. He suggested that the panels needed to be flush with the front of the Khorn to complete the bass horn (approx. 4'). I cut 2 pieces of 4' x 8' x 3/4" birch ply and 2 pieces of 4' x 8' x 3/4" MDF in half (actually I cut 3/4" to one side to allow for the overlap but I doubt it matters). I sandwiched vibration-absorption material (like Dynamat) between the birch and MDF and spread wood glue on all surfaces and put 1 1/4" wood screws every foot to ensure a tight, secure fit. You can also use 2 x 4s between the panels but I didn't have that kind of the space. Using a square and the actual bass bin, I fitted the 2 panels together, added another strip of "Dynamat" where the panels meet and used 4" teflon-coated deck screws to attached them together. I didn't glue the panels together because the panels weigh over 50lbs each and it'd be impossible to get them out of the house without cutting 'em up. That's the wings...

Next, I bought enough walnut boards to cover the bottoms (and tops but that's not called for w/Khorns). Of course, you can also use another piece of birch ply with or without the MDF and attach the panels as above. If you cut at the corners of the ply panels, you can fit the bottom panel inside the wings and the panel will stick out a bit from the bass bins or attach them under the wings and it'll be closer to flush with the bin. I recommend the bottom panel - especially if you have carpet.

After adding additional pipe insulation to the bin's rear panel and placing the bins in the wings as snug as possible, I determined the angle and measured the space between the bass bin and wings and used the spare walnut (or birch ply) to make 4 braces/per bin. Although its probably not the best solution, I placed 4" corner braces (like the ones used on drawers and shelves) and placed the braces so I could utilize the existing screws and wing-nuts that are used to attach the screens to the bass bins. This would allow me to remove the wings and return the Khorn to its original condition without any extra glue or screw holes should the need arise. This part is a bit tricky compared to the rest of the project but with a little patience, it works like a charm. Using the 4" corner brace as a guide, I placed it on the screw pertruding from the bass bin and spun the wing-nut on a few turns (not too much as you'll need to turn the nut for a tight-fitting brace), marked the screw holes on the wood brace, removed the corner brace and attached it to the wood. I re-attached the wood brace with the wing-nut and using a level, marked where it met the wing panel. Then it was just a matter of measuring from the top and marking the drill holes on the other side. I used 2 3" cabinet screws per brace. I then tightened the wing-nuts as snug as possible  - the tighter the better. I would say the braces are just as affective as the bottom panel - I highly recommend both.

I think that's it. I had to make the wings for my project but I'm happy with the results. The finished product can be seen in my avatar. 

[tk49]

Kudret, I have considered the kit idea, biggest consideration, is it a one size fits all? I need to do more research.

Tom

[rmlowz]

Hello gaspr,

Would you happen to have a picture of your false corners so I could show them to a cabinet maker? Me and wood do not get along at all. I want to have some built. I just ordered a pair of Khorns and they will be on both sides of the screen not in the corners.

Thanks,

rmlowz

[gaspr]

Sorry but I do not have any false corners. Maybe Speakerfritz has some pics of his??