Some help on building a Khorn copy.

[simonms]

Hi Folks,

I am a newbie round here so hope that you can help me on this well trodden subject. Over the last few days I have been trawling this forum for info regarding a Khorn copy particularly threads regarding Speakerlab plans and builds.

I want to try and build a pair as I have recently re furbed a pair of Belles and really enjoyed the project and want something a bit more challenging.

....oh and Khorns are not easy to come by in the UK.

I specifically want to know about the Speakerlab K bass bin as this is going to be the key I feel to achieving my goal of building something akin to the Khorn.

I have the plans for the Speakerlab K but am aware there was a speakerlab SK- Which of these plans would you say is the best to use?...and are there any other plans that would come recommended?

I plan on using the Crites 15 inch woofers with a 3x13 inch motorboard cut out and have a workshop with a nice big tablesaw- has anyone got any hints or tips on the build as there are some difficult angles to cut for perfect joins-glue types, saw types ( I was looking at a festool plunge saw ), etc.

There seems to be some using 1/2 inch, and some using 3/4 inch ply and some using a combination of the 2 i.e !/2 inch for the internal horn and 3/4 inch for the cabinet sides and tops...what is the opinion on the best contruction method here?

The speakerlab plans seem to lend themselves to closing in the backs with the top and bottom being the same size...good idea?

Just looking for any advice you may have really regarding your experiences and feelings about such a build in preparation for my own.

And if there are any other recommended plans-I would be happy to pay you for them if useable.

Thanks in advance Simon.

[T.H.E. Droid]

Just to clear up a misconception, all the Speakerlab K models were designated SK's. There were different sub designations such as SKs, SKi, SKf, SKu, etc. for differnt setups. Speakerlab sold built speakers, driver kits with plans, knocked-down kits, and unfinished but built systems. The only option in terms of drivers was getting the HT350 tweeter instead of the HT3500, and over the years the Speakerlab K crossover evolved between open frame and cased designs.

One thing I don't like about the cabinet design is the tweeter placement off to on side of the midrange horn. That makes the speakers asymmetrical, which implies that it's possible to end up creating room modes that are uneven from left to right, which can screw up your soundstage. I prefer the symmetrical vertical arrangment of the Klipschorn. Of course if you are building your own K's, simply make the mid/high cab front taller and place the tweeter over the midrange horn.

I have had both Khorns and K's, so I can compare the contruction. My K's did have side sheets, which I liked, but they do add a lot of weight to an already heavy speaker. Depending on how you will place them in your home, you can use side sheets or omit them, a luxury when you build your own.

One thing I really dislike about the Speakerlab design is the monolithic slab front, which incorporates the midrange/tweeter driver mounting panel in the front panel of the bass cabinet. When compared with the removable "top hat" section of a Klipschorn, the Khorn seems very elegant and the Speakerlab rather crude. I recommend you try to copy the Khorn design of a separate mf/hf upper cabinet if you can.

Construction wise, use the best quality solid-core 3/4" plywood (not sure what the metric designation is for that in UK) that you can buy, especially for the inner woofer cabinet, which will develop the highest pressures. Pay close attention to the quality of the joints and that they are well sealed. About the only place I can see using 1/2" plywood is the side sheets, and I don't even recommend it there. You can probably get by with good MDF for the top and bottom sheets and parts of the top hat.

As for special tools, about the only place you'll use that expensive plunge saw is cutting the driver slots. A good table saw with sleds and angle jigs is your best bet and generally those accessories you build yourself.

Crites components are fine, but I recommend you have Bob build you a second order bass low pass filter instead of the first order design he includes on the A/4500 crossover. I found the stock second order low pass filter worked better and made the bass response much cleaner. You might even want to consider some of ALK's high slope designs to better separate the frequency bands. Low order crossovers can result in a lot of modal distortion where both drivers are producing the same frequency, and at best the Khorn design has some real challenges when it comes to room modes and phase distortion. His tweeters are excellent and resolve the problem created by the delicate EV tweeter, which is namely having to be crossed over at too high a frequency. As Bob explains, that pushes the frequency response of the midrange horn to it's limit. Bob's CT125 tweeters are very happy producing down to the 4500 hz range, which keeps the midrange horn running in it's optimum range.

Good luck on your project. Take your time and do a good job and you'll create nice furniture that everyone (except probably your wife) will enjoy. My wife called my SK's "the packing crates" and she has named my Khorns "the black monoliths." In fairness, I have given her the living room, which now it looks like Laura Ashley and Martha Stewart were wrestling for a hand grenade when it exploded.

[PrestonTom]

It would be an ambitious project. There are double bevels and depending on your skill-level these could be a challange.

My friendly advice is to consider building a Jubilee bass bin. There are a number of sketches that have been posted and some of them are better than others. I don't know that any of them are completely accurate, but it would probably get you close enough. It can be done on a table saw, and a radial arm saw would be useful in conjunction.

The adavantage of the jubilee is that it is an easier build (although not trivial), a better bass bin and could more easily incorporated into a two-way system (if that is important to you). The difficulty is finding a proper HF section to mate it with. IMO, that is the major problem with the DIY Jub projects.

[Coytee]

To build on what Tom said...

Two pair of Jubilee's (that I know of) in UK.

Ralph has a pair in Slough and Simon has a pair in Norwich.

Might be worth hearing first

[simonms]

Many Thanks T.H.R. Droid for your thoughts-this really is a great place for supporting Paul's timeless designs-the key seems to be seemlessly putting these together so jigs and slowly slowly approach will be the order of the day. We have 3/4" Baltic Birch over here in 8x4 sheets so wil need 4 or 5 of those.

I will bear in mind your recommendation of 3/4" for the entire build.

I will build the top hats as close to the originals as i possibly can as the speakerlab top look too small for the bass bins visually for me but I have a feeling that will be the easy part.

On closely comparing my spaekerlab k plans to some construction pictures by North Reading Engineering it seems that there are some, how do i put this "clumsy" areas for example the Speakerlab plans have 4 tabs at each corner of the bass chamber which are the start point when construction begins but the NRE plans have a rather more refined length of ply that runs the whole length of the chamber with 3 triangular cuts on each and 2 triangular cuts in the ajoining bass bin which seems a more robust design to my eyes-I can e-mail the pics if that is hard to picture.

I am just after the best result possible with the bass bin section as all the drivers and crossovers would be wasted if partenered with a poor bass horn.

Thanks again Simon......more advice please everyone!

[simonms]

Thanks Preston Tom and Coytee,

Yes I have read in many threads that the Jubelee is an easier build but I like the Khorn's looks and I like a challenge too and I am confident that albiet with a few trial cuts and jigs that I can do it-I am meticulous and have really bad ocd when it comes to these matters.

I agree about the various baffling options for matching drivers etc- this has prevented me from starting other builds but there seems to be some great options available for horns and drivers-I have the original K 33 Bass units a set of horns from my belles with thek55m plus tweeters but I think I willbe using Beyema drivers and Volti horns in the top hats.

oh...T.H.E. Droid we also have the Laura Ashly problem LOL surrounded by patchwork quilts and Knitting I'm 35!

Regards Simon

[garyeanderson]

Have you read this topic? The 9th post is a link to John Warrens K horn
build.

http://forums.klipsch.com/forums/t/153084.aspx

The 3/4 (19mm) plywood is only the 38 1/2 x 31 1/4 that is the front of the
bass bin, the rest of the sheet stock 1/2 inch or 12 mm plywood.

My guess is that not having a Klipschorn to look at will present you with a handicap.
Photos do not convey the same info as looking at the bass bin. I have built
lascala and cornwall clones and I
think I will pass on the K horn build. I have found them locally though for
less than it costs to build so the situation is different. Good luck with the
project what ever you decide on.

[simonms]

Many thanks Gary,

Yes there are pit falls by not having an original to work from but I have a few knowledgable people who are helping me with detailed e-mail and photos. The 3/4" and 1/2" ply is what is confusing me somewhat as there seems to be conflicting plans and statements-my 1983 Belles have 3/4" Birch on every exterior panal and I won't the exteriors of my Khorn copies to look that robust too-but the internals could be built with 1/2" is seems like there is not a difinitive answer to this even my Speakerlab K plans contradict themselves. I am drawing up my own plans based on these Speakerlab plans to familiarise myself and think I will specify that all interior contruction to be made with 1/2" and Outside cabinets with 3/4", lets see what people think of this idea.

I will also be closing in the backs and building grille frames from 3/4".

Your comments are very welcome.

KR Si

[garyeanderson]

HDBRbuilder has always offered a nice point of view from an employee standpoint and in many other ways too. His posts are worth reading and sometimes re-reading. This is the search I did to find a post

http://forums.klipsch.com/search/SearchResults.aspx?q=hdbrbuilder+AND+klipschorn+AND+build&o=Relevance

with it I found this post that I have read before

http://forums.klipsch.com/forums/p/12643/94435.aspx#94435

worth reading I think

Please do build yours, just be as prepaired as you can.

[Invidiosulus]

Have you read this topic? The 9th post is a link to John Warrens K horn

build.

http://forums.klipsch.com/forums/t/153084.aspx

The 3/4 (19mm) plywood is only the 38 1/2 x 31 1/4 that is the front of the

bass bin, the rest of the sheet stock 1/2 inch or 12 mm plywood.

My guess is that not having a Klipschorn to look at will present you with a handicap.

Photos do not convey the same info as looking at the bass bin. I have built

lascala and cornwall clones and I

think I will pass on the K horn build. I have found them locally though for

less than it costs to build so the situation is different. Good luck with the

project what ever you decide on.

I thought that the back pieces of the woofer chamber were also 3/4" on John's build. There are certain pieces that are relatively easy to change to 3/4" without messing up a bunch of other measurements. The speakerlab plans add a brace on the two trapezoid pieces that make up the back of the woofer chamber. I would certainly build as much has possible out of 3/4" to keep the cabinet resonance down. Don't let the Jub toting naysayers discourage you from building a set of khorns.

[simonms]

Thanks very much for the replies so far, Gary you are off course correct to tread carefully and the links were very helpful in forming an approach to the build-I think my passion for the originals will drive me forward here and in some respects am attracted to the complicity of the build-I had considered Jubilee's and Jamborees but feel that the Khorn will be better suited to my space-I think there (for me) a fine line between HiFi and PA systems if that makes sense when it comes to big speakers and the Khorn would sit in my space beter and although big would not overpower the room with size.

Aesthetically I prefer the Khorn-it just seems "right" as most succesful designs do.

HDBbuilder's offerings are a credit to the site-i have trawled through 50+ threads and his consistent understanding and help are really helpful to me as well as a facinating insight into the workplace at Klipsch.

Invidiosulus-thanks yes I need to move on with positivity as working with the 3 set of plans I have although all good there are things that I prefer fromone than the other so drawing up my own plans is a headache and will take me a while,but thats part of the fun I guess.

I have been looking closely at the pics on the North Reading Engineering site and they seem to be using 3/4" ply throughout, and as you said cabinet resonance would be a worry for me with 1/2". I am more drawn towards using 3/4" throughought so would be interested if anyone feels that this is a good idea or not....I'm certainly drawn up my plans implimenting 3/4".

I am preparing for a few practical fails in the workshop before they come together!

Thanks all so far...really helpful, nice to be a part of such a passionate bunch!

[garyeanderson]

A picture of KD-FR 4L 874 and 4 L 875

The motorboard that is held in place with a pair of channel iron bars is 3/4 the rest is1/2 or 12mm. the motorboard was eventully done away with sometime after 1976, my 79 does not have one.

The photo timed out (3 or 4 times) loading so I will reply with more singles

[garyeanderson]

another

[garyeanderson]

Any plans you redraw with 3/4 or 18mm will be different than the
Klipschorn. I think you are missing out on a lot not having one to look at. By
looking at the actual cabinet you can see how the Klipschorn gets its rigidity
and strength. The Klipschorns on John Warren's Site have a few mods

http://community.klipsch.com/forums/p/113603/1144775.aspx

are a modified Khorn, If I were you I would start making
full size foot print drawings of the various speakers and try them in your
corners just to see what the difference in the sizes of them against where you
have to place them Once lost in a corner they are almost lost. I had the
Cornwalls in front of the Klipschorns and someone pointed at them and said
"big speaker!" then I pointed out the Klipschorn hiding behind it. The
front of the lkipschorn is about 29 inches (750mm) out of the corner, I think
that this is your critical dimension as far as room placement goes. Have fun
with the project and don’t hesitate to change your mind, as things will come up
that were not as expected.

----------------------------------------------------------------------------------------------------

September 28th 9:13 am

I edited the line below out of the text above, the statement is Wrong and I think that correcting it is best I checked 4 L 874 Klipschorn and it has both upper and lower horn flairs as part of the back volume. I hate being wrong but like to learn, checking on statements I make shoud be done before an not after the post. Oh well, times move on!

"it appears
that John has used the top and bottom ramp chambers to expand the back volume,
Klipsch has these ramp chambers closed off."

Gary

-------

[simonms]

Great!, Many thanks, Yes reading further today it does seem that the motorboard is somthing that I may not use but I think I will try it with and without to see which I prefer-also some interesting notes about the 3x13" cut out in the motorboard with regards to rounding out the 3" cuts to follow the line of the drive unit.I am also looking at a plan from the Volvetreter web page that is metric and seems closer to the North Reading Engineering build than the Speakerlab k.

Thanks again-hugely appreciated!

Si

[Nat Denkin]

Great!, Many thanks, Yes reading further today it does seem that the motorboard is somthing that I may not use but I think I will try it with and without to see which I prefer-also some interesting notes about the 3x13" cut out in the motorboard with regards to rounding out the 3" cuts to follow the line of the drive unit.I am also looking at a plan from the Volvetreter web page that is metric and seems closer to the North Reading Engineering build than the Speakerlab k.

The motorboard makes it much easier to install or replace woofers!

I built the Speakerlab K (in 1984) and replaced them with Jamborees last year. They fit about the same in corners. When using 3/4" Baltic Birch, measure the thickness; mine was closer to 17.4 mm and the differences add up when you want a tight fit. Enclosing the Speakerlab K is highly advised especially if your walls are sheetrock. I was quite happy with the sound using Crites 1526c woofers, ALKs trachorn (Atlas drivers), Beyma CP25 tweeters and ALKs universal network. After 26 years of looking at the Speaker Ks, I just wanted a change.

A real downside of the Speakerlab K is that they have essentially no resale value. Used Klipschorns might be a good alternative when you add up the real expenses of DIY. If you know how to make compound bevels, the Ks are a good project, otherwise, you might be better off with either the Jubilees or Jamborees that have few difficult cuts.

Enjoy the project,

nat

[simonms]

Thanks for the input Nat-is the pic by your name your speakers? Lavera horn ontop of jamborees? I considered this myself but I am no expert with cross overs, do you feel that the Jamboree is a beter sounding speaker to the speakerlabs? How would you describe the difference in sound?...and did you build them?

Gary, many thanks for all your advice and pictures-really helpful, it does seem that a few designs have internals made from 1/2" and exteriors with 3/4" so am re drawing with that in mind but do worry about cabinet resonance (oh the motor board is made with 3/4" to).

All the more reason to make sure they are joined glued and sealed accurately-it does seem closer to the original design though.

Thanks all any other thoughts welcome.

Si

[Marvel]

I was quite happy with the sound using Crites 1526c woofers, ALKs trachorn (Atlas drivers), Beyma CP25 tweeters and ALKs universal network. After 26 years of looking at the Speaker Ks, I just wanted a change.

nat

nat,

What Atlas driver were/are you using?

Bruce

[LarryC]

I suggest you carefully review this thread, which I wrote after restoring the original geometry of a 1962 K-horn bass horn: http://forums.klipsch.com/forums/p/38731/350047.aspx#350047. I think it would be difficult to cram 3/4" ply into the original K design, without changing the geometry and causing unintended acoustical side effects.

In particular, I'd be cautious about using either a 3/4" motorboard or a separate mounting board, and about using ply thicker than the standard 1/2" in either place. I found that, when I updated my drivers and xover, I had to get rid of the separate mounting board to eliminate an upper mid-range peak at around an estimated 600 Hz.

It apparently had to do with changes in acoustic capacitance caused by the horn throat's having a thicker passageway, according to D-man, who'd studied this in great depth. I haven't seen him on the forum for a long time.

[simonms]

a LarryC, you are on the money with everything you have said, this thread may seem a little chop and change re my build but I am learning more every day (there is alot of it to learn), I'm just taking it slowly as as much as building them I am fascinated with history and design as much as anything.I am in the process of drawing up my plans and they are changing day to day but I am going down the road of 1/2" ply for the internals and IF I use a separate motor board for the bass driver (I have not seen a plan yet that does not use one) I will try both 1/2" and 3/4" so that I can hear whats happening but I suspect after reading about this that I will not use a motor board at all- it will be interesting to hear what the differences are just to put what has been written here into perspective.

At the moment I am intending to utilize 3/4" ply for the front, sides and tail board but off course with your expert help this is all subject to change but I hope I am on the right track with the planning process-it really helps to draw this plan up as its a design that you have to get your head around and I think that is important when it comes down to the practical build (i still expect to have a few failed cuts etc as Gary has warned)....well Morandi said of his painting "I expect to fail 9/10ths of the time but its the 1/10th that is important". I like that sentiment as it is shows intent and understandind of a creative process and one that I may be wise to adopt.

Is D-Man Danna? He was kind enough to send me the plans for the Jamboree and his posts are full of insight shame he does not post so much noe - seems a wealth of knowledge!

Ta Si