D-MAN Posted October 12, 2006 Share Posted October 12, 2006 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 Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 There are many Klipsch-related (and/or licensed) rear-loaded horns... Here are a couple... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 A couple "Shorthorn"-like variants... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 More examples... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 The famous Gately "Super-horn" even mentioned by PWK (in a humorous manner as representing a "new breakthrough in horn design", along with his own Shorthorn)... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 The better the LF response, the large the horn... as an example, the Jensen Corner Imperial. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted October 12, 2006 Share Posted October 12, 2006 wasn't quite the one I was looking for...will keep looking. rearloadedfoldedforn4524846.pdf Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 The large Tannoy rear-loader... Quote Link to comment Share on other sites More sharing options...
Guest " " Posted October 12, 2006 Share Posted October 12, 2006 Here we go. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 The Tannoy GRF is far more work to build than the Khorn! It could be that it was intended as a show-horse for the Tannoy Gold-15 coaxial driver, etc. but it stands 60" tall as a single unit and must also weigh a ton! That is a lot of work to build and ship, so if it doesn't compete with the Khorn and its ilk, then I have to wonder, why bother? The answer (apparently) is that it PROBABLY does actually compete effectively. It may not be economically viable, of course, but sonically I suspect that it has its own set of attributes which could make it an somewhat "equal" contender. Anyway, I'm not going to do a full 1/4 wavelength rear-horn, as there are already front-loaded designs that do that quite well. If I was going to do that much work, I'd build a front-loader for that reason - its a sure thing. But it seems that there is an area between the full-size monsters of the past and the too-small modern full-range 1/4 w pipe-types that seems not to be fully explored in the case of modern small Vas drivers specifically for domestic use. I'm not talking PA designs, I am talking about strictly domestic designs, and a different set of issues. DM {edit} The cabinet shown above is what I'm talking about - the full-range driver (Lowther, etc) type with the typically too-small mouth size for an effective non-peaky response. Now, it needs to be understood that peaky response is OK in certain cases, and this MIGHT be one of them. However, I have a couple of tricks up my sleeve to experiment with that issue. If the reactance peak(s) is lined up just right, you've got a wider-bandwidth device instead of a port, with the added efficiency of a horn (if it stays horn loaded across the bandwidth, which in most cases of too small/too short, it won't and will instead act like a 1/4 wavelength transmission line/pipe instead). That particular behavior COULD be purposefully exploited, but that would take some very careful attention, which I think most designers avoid. Look for absorptive material (damping) in the pathway in such a case. Even 1/8th space placement isn't going to give enough boundary reinforcment to even approach a legitimate mouth size in the case of the above horn, IMO. Back to the too-small horn mouth with too-short pathway, it is "acceptable" if only a small "section" of available bandwidth is horn-loaded, especially the case for low-SPL applications like the "lone girl with the guitar"-types, exactly NOT one of my criteria! This is the realm of the small-signal full-range driver (which really doesn't put out alot of low frequencies anyway), certainly not my cup of tea. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 Which brings us to this, the 1950's patent to Glenn of General Electric. A "must read". DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 Alot has been said about the issue of time-delay and comb-filter distortion as being part and parcel of a rear-loaded horn. The same issues are there for a front-loaded horn, too, perhaps even more, as the front-loaded horn of some quality is typically 1/4 wavelength in overall pathway length. For a bass horn, that is likely to be a given that there is going to be phasing issues because of it. Probably less in the rear-loaded variety, as the pathlength is typically shorter. That comes with its own problems, of course. I'm just thinking... Rear-loading allows for a wider bandwidth (albeit lower efficiency) than a front-loaded horn all things being equal. Rear-loading requires physical limiting rather than electrical limiting in upper frequency response. Rear-loading promotes the use of higher Fs drivers, i.e., cheaper. Rear-loading is a wider bandwidth device than a reflex port, more efficient than a drone cone. Combinations of all of the above are possible. Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted October 12, 2006 Share Posted October 12, 2006 what about the JBL ......Scoop ...?? 2-15's, or 1 18 ..... will rattle your fillings Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 For free-standing use - they are all going to end up being "scoops" - that is the most viable "smallest" footprint design IMO. However my criteria is NO PA! If I wanted that, I'd have one already! I suppose you could call my design a "partial scoop" anyway. There is nothing new under the sun. There is a fine line between acceptable complexity and increased performance, and simply not worth it when other designs would work better - somewhere between just a box with holes in it and a front-loaded corner horn. Where that exact point is, I just don't know. DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 This Olson design (RCA) is reputed to do 94db at 27Hz, according to Bill Woods... Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted October 12, 2006 Share Posted October 12, 2006 However my criteria is NO PA! Aaaahh... just make grille for the front ... you'll never be bothered by what's hiding inside Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 Like I said, at a certain point, wouldn't you rather just build a Khorn? DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 Like I said, at a certain point, it crosses a line - for all that size, weight and effort, wouldn't you rather build a Khorn instead? This Jensen enclosure is approaching that point, but I think it is probably still and easier build than the Khorn. Remember the Khorn has a top cabinet to make, too! But this is getting complicated! DM Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 12, 2006 Author Share Posted October 12, 2006 Ah! back to simplicity, and an ability to free-stand or fit into a corner... This is a 1950's Jensen/Cabinart "shorthorn-type" cab licensed by Klipsch. Unfortunately, this won't go very low. However, it was determined to be competitive enough to warrant its existance AND a license agreement! Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted October 12, 2006 Share Posted October 12, 2006 how do you size the Slot ...??? Quote Link to comment Share on other sites More sharing options...
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