D-MAN

A couple "Shorthorn"-like variants...

There are many Klipsch-related (and/or licensed) rear-loaded horns... Here are a couple...

Yeah, I know: If PWK stopped with the rear-loaded Shorthorn/Rebel, then there must be something wrong with the concept? Well, historically, there are way more rear-loaded designs than front-loaded ones. And the Brits (who tend to know their audio) always seems to prefer the rear-loaded variety, even ones that dwarfed the Khorn (large Tannoys, etc), I was wondering if I was- well - missing something because of my PWK-inspired front-loaded-horns-only conviction? So I have been thinking of trying the rear-loaded approach with certain reservations... Here's my design criteria: 1) It has to use AT LEAST a 15" driver. None of this small driver crap for me! It has to "rock out" as least as well as the Cornwall when required. 2) It has to have attributes that the Khorn and my front-loaded designs DON'T have. In particular, probably in the output-to-footprint ratio. It would probably still be larger than the Cornwall, but that is a good footprint size to stick to as much as possible. 3) It has to out-perform the Cornwall and its ilk (ported direct-radiator designs). 4) Since I have corner horns coming out my ears already, maybe a floor-stander might be interesting (think rear-channel HT)... The Jensen Corner Imperial (aka "the Laboratory Standard") has always been intriguing to me, although its size (larger than the Khorn) has been the reason I have passed on it. I have heard some complain that their Khorns don't have quite the "punch" that they desire, but I've heard 1970's SpeakerLab "K"s that totally kicked my tail, so it isn't the design, per se. It's the driver. But I digress... Back to rear-loaded bass horns, seems to me to be a compromise could be made, and the ability to effectively and easily "punch" is part-and-parcel of having a cone blasting at you, ala Altec A-7. What would be wrong with having a wider frequency device (i.e. horn) other than a reflex port hanging off the back of the cone? The recent and rather undersized horns (actually more of a 1/4 wave pipe than a true horn) used by the full-range driver crowd seems a little too anemic to me. I'm thinking at least dual 12's or a single 15" enclosure with a "livable" footprint. Technically, a rear-loaded horn is an easier design as it has a limited bandwidth, efficiency is naturally lower, it can, by design, be "peaky" in its response, and still be more than satisfactory. It's drawbacks are the same as with a front-loaded horn - it is going to be large if it goes low, which of course, is its point. The question remains, can it be done with modern (small Vas) drivers in a "relatively" small(er) footprint design? I'm thinking of giving it a serious shot. Here is my first attempt. DM

Agreed. But correct me if I'm wrong, but its the only magazine left that has anything to do with DIY?! That stinks! It only leaves professional journals which are much more expensive! DM

Makes me wish I had a CNC machine! I think the recessed access panels are the hardest part! JC, looking good. Keep us posted. DM

That is a problem. Personally I think there is too much "dumbing down" going on across the country in lots of avenues. For instance, look at the "quality" and education of the typical government employee, etc. It's not very hard to understand, is it? One should aspire to learn and grow, if the value of the information is to be comprehended and appreciated. I have had enough of the lowest-common-denomenator - none of them has ever improved my life one iota. I come down on Al K.'s side on this, after all, technical discussions, that is, discussions of technical issues which are not specifically conceptual in nature, are not capable of being "dumbed down" or the technical information is lost. In a technical work, what is left other than sounding downright like a layman, i.e., UNPROFESSIONAL? Al is indeed quite right IMO. I too would tell the editor in question to perform certain specific rituals of an unsavory nature upon himself. The lesson I take away from this is that AudioXpress is far too pedestrian in nature to competently present technically-oriented material (which I would want to read), even if it is written in a "generally understandable" form to start with. Sometimes technicality is required to get the facts across. I don't NEED or WANT to feel all warm and fuzzy reading an audio magazine, I want to learn something that I didn't know. Otherwise, its just another bloody fanzine, isn't it? DM

Pics need to be JPG's to upload to the Klipsch forum, as far as I can tell. DM

The Khorn is operating the K33E at about 30% (my estimate) below optimum efficiency by compression. This tends to flatten out the response but limits the bandpass. It crosses over at about 400-450 or so, depending on which crossover point you want. The lower frequency below cutoff are roll off at -12db vs the Jubilee's -18db (if I remember correctly). The Jub will simply drop off below Fc with a more rapid slope than the Khorn, being that it is close to being fully annulled and the Khorn isn't. The Jubilee is operating at pretty much full efficiency for the driver(s). The Jub has a slightly larger throat area (90 sq. in. total) vs the Khorns 78. The Jubilee will theoretically achieve a higher SPL with lower distortion for 3 reasons, one being larger throat area, the second being the rapid flare rate at the throat (almost twice of the Khorn throat flare rate, i.e., 50Hz) and the third being symetrical folding in the same plane. It may also expectedly have better transient response due to the folding and the use of smaller diameter drivers. In effect, the Jubilee has its strong points (its upper bandpass) and its weaknesses, the lower frequencies below Fc. The Khorn has its strongpoints (its lower frequency response), and its weaknesses, namely the upper frequency corner limit. If one was to chose a set of drivers for the Jubilee that wasn't as near to being fully annulled, it is conceivable that the lower frequency range below Fc could be increased somewhat, but the tradeoff would be expectedly be in efficiency across the bandpass, possibly including (at least in part) a reduction of the upper frequency corner. So it depends! DM

Looks fine to me, as long as you have the appropriate security-head driver. I haven't used T-nuts at all in all these years. I use exterior-type wood screws, have to be careful about stripping which means that when tightening, you have to use a manual driver. But in your case, yes, I wouldn't mix types. Another thing, I always use 10-20 threads, never had a problem. I can't imagine what it would take for a driver to strip a 10-20 thread by force! I suppose that certain PA large-format large signal rigs could do it, but that is probably never going to happen in my house! DM

Note: The 1940's plans are for a 12" driver, the Speakerlab "K" plans are copied off a 1970's era Klipschorn bass bin (for the most part) which uses the 15" driver. The Speakerlab K plans are quite good, and contain a few of the enhancements found in the original 1940's plans, and more importantly, are entirely reliable and accurate. The performance is the same as the genuine Khorn. Now, there are 2 separate versions of the Speakerlab "K" plans. The 1970's version is the one that is very close to the Khorn bass bin. The later (mid-late-80's) plans do not have "wings", and therefore are not quite the same animal. There are no original Klipsch plans available for the 15" Khorn that I know of outside of a handful of private owners. Only after-market plans are available, and of those, I would go with the 1970's Speakerlab "K" plans. I wouldn't trust anyone else's. Speakerlab sold the plans and flat-kits for many years, so the actual plans are well researched, accurate, and comprehensive enough for Joe Blow to cut and build them himself. The EV Georgian is another 15" variety of Khorn bass bin, and the plans are available for free downloading. While it is an authentic licensed version of the Khorn bass bin, there are some differences between the genuine article and the EV version. DM

This looks like the "old" forum format! Anyway, I think you will have problems with not having enough screw attachement points on the access panels. I've hacked your picture (attached) to show what I'd do. Figure a screw down about every 4-6 linear inches. You will be mighty suprized as to how much power those driver have if you don't! Better safe than sorry. DM

In a nutshell, they will sound as good or as bad as the gear driving them. That would also include the source material and recording! DM

Holy crap! I hope that includes the drivers! Anyway, far too wide for my current horns. It would take a really wide cabinet like the Jubilee to make it seem "acceptable" for home use, seems to me. DM

I haven't seen any posts on the K402 , price-wise. How much are we talking here? Also, is the width correct, the LS is only 24" across? DM

I do remember my EV T-35 tweets hissing with the old Crown amplifier (back in the day). However, my current system is dead silent at idle, even with your ear right in the horn! So I think it's the amp. Impedance mismatch or possibly noise floor is just too high? DM

While I can see being frustrated by the wait, but it seems to me that they are certainly doing good by you. There is far, far worse companies out there whom you will eventually run into. Microsoft, Comcast, or your bank, for instance? Try their customer service and see how you like it! Thank you sir! may I have another?

I was considering the wiring, and my opinion is that the connectors shown on the top access panel on my horns, should be mounted on the tailboard (horizontally) and run the wire htrough the tail board/wedge assembly into the back chamber. Tie a knot on both sides (if possible) and seal the hole around the wire with silicone. You are wiring in parallel, right? I would wire the drivers with the drivers mounted so the terminals face the nearest access opening. I would also use equal lengths of wire for each driver. But that's just me! If the driver has screw-down terminals, great. If tabs, use pull-off tabs soldered to the ends of the wiring. Do not solder the wire to the driver terminals, ESPECIALLY if you are going to be changing drivers, even occasionally. Otherwise, you will be pulling the wiring out with the drivers every time (rather than attempting to unsolder them in the cabinet prior to removal). Or you could use more wire than you need, so the drivers can be pulled and then unsoldered. Or you could simply not solder the wires in the first place, and problem solved! In other words, think ahead. DM

The flush mount variety shown with access panel in place. The panel is 5/8 veneered both sides. It does not vibrate much at all. The terminal connectors on the access panel (as shown) are probably not such a good idea on the Jubilee, IMO. Notice the number of screws used to tighten the access panel down! Do NOT skimp on the number of screws, or you'll be sorry. It is suprizing how much force the driver has, and how small of a gap that air can squeeze out of. Did you know that the thing can actually have water-tight seals, but STILL leak air? DM

I think the way the stock one does it is the way I have mine, the flush-mount inset variety. That means the access panel is the same thickness as the top/bottom and is screwed to a "lip" set inside the back chamber to line it up flush. There are several ways of accomplishing the access panel - Gil did the "heavy" approach and doubled the top/bottom panels to create the lip. Mine uses 3/4" strips along the inside walls of the back chamber. Then there is the overset-type as seen on the stock Khorn and LS where the panel is oversized and is screwed directly into the top/bottom (in this case). Overset is the easiest to do, of course. In the case of the Jubilee, I don't see a problem as long as the panel is appropriately large so that it forms a solid surface to support the cabinet on the bottom. Entirely up to you which one you go with.

Are you POSITIVE that it isn't the amplifier? To check, swap the speaker cables between the speakers - if the problem moves, it's the amp. This will also tell you whether its a connectivity problem or not. Typically drivers fail catastrophically if overdriven. The cone tearing away even partially from the VC could be a problem, but if that was the case, it should be getting worse the more its played, which is why I've still got questions about it. Pressing on the cone when it is active serves nothing. You need to inspect it for smooth movement in and out when its NOT PLAYING! If possible, remove the driver and inspect it all over for correct mechanical operation, i.e., no tears, smooth movement. DM

Get out the paint... before you put the top/bottoms on... seems like it would be easier for doing the inside channels... DM

Mike, I can't buy into that - they included a reflector, albeit half the size of a full channel variety. Not much savings there! Same labor is involved. I think we can agree that it isn't a matter of economics or ease of building! It's definitely a performance-driven decision, as you suggested, but I would just like to know the EXACT reason, instead of guessing It could definitely be crossover-driven, too. A design hold-over for a particular crossover point and/or slope contour, maybe. That would also allow for preselected drivers (particularily the midrange) to be used, something PWK was known to design for. That is good thinking. Why didn't I think of that?! DM

One would think. However, I've been thinking about this particular case... bear with me here... I am suspicious as to why PWK and Roy would have used full-channel reflectors on all but the front corners of the Jubilee, exactly like the La Scala. Since Roy has never commented on this, left to my own devices, I have come up with some possibilities. 1) It's clear that its not an oversight. PWK did it more than once, and in both cases, it was prior to a change in flare rate. However, the flare rates in question are opposites, in effect - that is, the LS second flare rate is the higher of the 2, i.e., less reactance, and in the Jubilee, the second flare section is the lower of the 2. The one thing both instances have in common is that a change in reactance follows the non-expanding "capacitive" section. I decided that in the case of the LS, the non-treated fold is specific to reducing the upper band pass, allowing for a 6db 1rst order slope to be used. However, the Jubilee design seems to NOT want to limit the upper bandpass, or does it?... 2) the corner in question occur just before changing flare rates (to a lower one) and after the turn, a non-expanding columnar "connector" section is used which transfers the acoustic resistance from one end of the column to the other end basically intact (discounting losses due to viscosity), and the more constricted flare rate following means an increase in reactance is apparent at the "throat" of the second flare section. I suspect it has to due with the capacitance of a semi-treated (radius-type reflector) fold which reduces reactance at the throat somewhat and also tends to reduce the upper bandpass as a by-product. I suspect it has more to do with the capacitance at the throat of the second flare rate to match the impedance naturally caused by the subsequent tighter 32 Hz flare rate. Essentially, it's an impedance-matching device between horn sections of differing flare rates. The question remains, though, does the Jubilee need to restrict any upper bandwidth frequencies? The possibility exists that it may reduce a tendency for "peakiness" in the upper response. Now, the effect of a full channel reflector at the fold SHOULD maintain the waveform pahse and frequency bandwidth virtually intact around the 90 degree bend. The diliterious effect of hitting the side wall in the 32 Hz flare section will THEN reflect the waveform all over, so what is gained by the full channel reflector is now lost... So I'm to the point where I think it doesn't actually MATTER which approach is going to work better. I would guess that it is possible that there would be NO HEARABLE DIFFERENCE in the case of the Jubilee. To further support my case, I have attached an extract from the Jubilee paper, which clearly indiocates that PWK and Roy originally used a full-channel reflector at the front corners. On the Jubilee it was specifically left out... I find it infinitely interesting that they DID use a radius reflector instead for the 90 deg. fold. I don't really have an acceptable explanation for this except what I surmised above. Any input would be appreciated... DM

I agree with Mike. The size required for a true horn of "sub" frequencies would be very large indeed. That's why most horn subs smaller than refrigerators are not complete horns. Most tend to be undersized and rely on placement (walls, floor, etc) in a half-hearted and half-effective effort to make up the last section and form a mouth of somewhat "proper" size. This means that most so-called horn-subs tend to be very foreshortened to maintain a "reasonable" footprint. I would go as far as to say "if you aren't appalled by its size, then it ain't a good horn sub". Unfortunately, this generally entails ehausting the terminus into a capacitive space, rather than extending and maintaining the required expansion that a true horn structure would. Not quite the same as a full size horn in other words. Sort of a pseudo-horn, or partial horn. The natural result of a foreshortened horn is having a very peaky response - however, this is sort-of acceptable in the case of the subwoofer, since the desired sub frequencies generally would be contained in a single response "peak" in an otherwise very limited and very peaky bandwidth. It seems a shame to me that someone with a pair of "good" horns would want a horn subwoofer of inferior performance (comparitively) and think that a horn-sub would give them the extra performance typical of a well designed horn speaker that they are used to. If you really want a sub that badly, get a multiple-driver direct-radiator type, not a partial horn which is a compromise to begin with. DM

I would think that the Kappa-Pros might not be completely horrible in them... Done the math? DM