John Warren

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Hmmmm..OK, you win, $40/W Beam Tetrode amps RULE!! And what's even better, just with a flick of a switch we can shut down that pesky screen grid and instantly convert our amp to a $125/W killer SET. Anyway (yawn)....If the LaScala was manufactured by ANYONE else it would be dead and buried by now, forgotten like the LEE National Catanoid and the University "Dean". Hell, I don't even think PWK likes it.

Quite a fancy amp for a PA speaker designed for a train station in PA.

But PWK was not talking about cornerhorns was he? ------------------ JDMcCall He was discussing his cornerhorn.

"For large scale sound reproduction a pair of horns may be stacked in a corner, or arranged side by side against a wall eliminating the restriction of using a corner. Some space advantages of such an arrangement appear to exist over the conventional theater units" P. Klipsch in "A Low Frequency Horn of Small Dimensions" J.A.S.A., Vol 13, Oct 1941 page 144.

If any of one of you guys saw "The Mountain" in Framingham, MA (Bose HQ) you'd think twice about poking fun at Amar Bose. If he wanted too, his organization could easily engineer superb loudspeakers, they have the money, the clout, the staff and the resources. But for what purpose? Why go to the trouble?

I have a pair of 288B drivers. Belonged to 1005 multicells. As a combination, I didn't like them. The 288B were not the problem, it's a good unit capable of a linear response to about 12kHz, it's the horn. They were top-hats to a pair of "Voice of the Drive-in" units I purchased years ago at a church auction. Still have the 288Bs, sold the rest of it. Good driver.

If the reduced LaScala (exponential, wall placed, 10" driver), has 1.6 sq. ft mouth, these are the first order design parameters I would expect: fc 125Hz (linear response 140Hz up to mass cut-off of driver) throat 16.5" sq. horn length; 2.46 ft. doubling distance 7.5" air chamber volume behind cone: 360 cubic in. These numbers indicate that the response should drop off rapidly after 140Hz from wall placement. How significant are the deviations of the reduced LaScala from these numbers?

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at first glance the horns look thin and flimsy to me. it's hard to judge just looking at the pics but given the size 16"x31" i'll bet that they're pretty thin-walled which means more dynamatting.

Shock-late k 33 looks ugly but does a decent job in the k-horn. would rather see a cast rather than the stamped frame.

Some intersting catalog items. There was once a time when you could send a check for $713 back in 1956 to Leonard Radio in NYC and get an EV Patrician delivered to your door a few weeks later. That works out to something like $7K in 2000. University Classic is shown first. This is the low-boy configuration that used the C 15W showm in the earlier posts. And of course, the Klipshorn is shown. Q-man, I've included a picture of the "real" Jensen Imperial (Lenny1). Dig the funky elliptical brass work on the grille. This was a very popular accent in the big dollar units. Anyone have any history on Leonard Radio? I have a few catalogs from them. They were before my time.

I have attached a few pictures of a recent acquisition, a University C 15W woofer. The speaker is shown on the right. For commparison purposes a Klipsch K 33 (1982) is shown on the left. The C 15W incorporates a 6lb 4oz Alnico V magnet, total motor assy 17 lbs. At that time only the Tannoy 15" dual concentric contained more Alnico V magnet material than the C 15W. The dual 50 watt voice coils are aligned by two spiders. The frame is cast Al and the overall weight of the speaker is 27 lbs. Some "vintage" EV woofers were heavier but the weight was do to iron not magnet. Fs around 25cps. Designed for theater applications the unit was also found in the famous "Classic" low-boy/high-boy exponential horn developed by Abraham Cohen at University.

Never, never, never pay the price on the tag. Find the manager, make an offer 15% lower and if he he thinks about you're in, otherwise just walk. I bought a Toshiba Cable Modem from Circuit City, list was $250 before rebate, I offered $210 and the salesman settled on $230 before rebate. Some of this stuff has huge margins and the smart salesman will work with you, just ask. The more expensive the easier it is. They more you do it the easier it gets. You can always beat the internet price. If you paid full price for that new McIntosh, you paid too much.

Shocklate-Looking at the RCA unit, a 40Hz horn radiating in free space needs 62 sq. ft mouth, positioned at center of floor requires a 31 sq. ft., flat against a wall needs 15 sq. ft and in corner a 7.5 sq. ft. The horn pictured has a mouth area of 44 sq. ft. so maybe designed for floor placement(?). I don't know LaScala dimensions but the mouth looks like 2x1.5'=4.5 sq. ft. so positioning it against the wall gives you a 70-75Hz horn cut-off. Needs bass augmentation. The original application was for PA so bass output was not considered a primary design goal.

the k-33-e has two paper gaskets stacked together for total thickness ~5/8". there is no seperate spacer. the woofer is bolted directly to the 1/2" baffle board using 4 bolts. there is no chamber between the cone and throat. earlier units had the woofer mounted to a 1/2" thk 16" sq. board that was then mounted to the baffle with a rubber gasket in between. the board had a slot in it that matched up to the slot in the baffle, no round hole. initial slot cut-out was 6"x13" now is 3" x 13". old units where made with extra geometric stiffening like I showed in the DIY khorn pics elswhere in this section.

You can blowout the threads in the wood if you over-tighten screws or insert the screws such that they "start" new threads, ending up with screws that don't batten down the access panel. Unless the woofer sounds bad justlooking at it won't tell you **** unless you want to verify that it is a K-XX-E or whatever. I'd just leave it alone and only go in there if you've really think you have to. Also, that magnet does a great job at pulling your screwdriver tip right into the cone.

Tony, What you think is the "wedge" in the pic is actually a mid strip that runs down the middle of the throat. It "bifrucates" the throat. The wedges (there are actually two) are at either side and run parallel to the long axis of the slot as you mentioned. Scroll to the bottom right of -008, you should get a glimpse of what the throat looks like.

johnnyp-the mid-range horns for these were cone loaded wooden Tractrix horns using a JBL LE-5A 5" cone transducer similar to the design put forth by Bruce Edgar. Tweeters are a pr. of EV T-350's, the big brother to the T-35 variant sold by Klipsch, LLC. John

John P- The triangular holes on the side opposite the woofer access are needed to gain access to the volume of air located in the ramps. Look at -004X. The volume in the ramp is accessed by the triangular cut-outs on the baffle. In this design the volume of air behind the woofer includes the volume of air in the top and bottom ramps. That is the reason for the little 30° notch shown next to the screw in -004X. It's a vent. The cut-outs on the woofer access side of the baffle do nothing since I did not make the rails symmetrical. Direct access to the volume in the ramps is possible. The plans call out for two V-notched rails but it is obvious that the woofer access port would be blocked. For symmetry I just V-notched both sides of the baffle. As you can see, the baffle board in this pr. is somewhat different than the present Klipsch design. The 3/4" thick plywood plate resting atop the baffle initially was to be removable but getting a good seal (wood flex) is difficult. Since throat construction is the most critical part of the design, it must be rigid so I went the other way. I installed 8 c'sunk T-nuts into it, painted the entire side with glue and then bolted/clamped it to the baffle board. It result was a rigid, 1 1/4" thick baffle. The face of the plate that the woofer bolts up against gets one coat of poly as did the throat, more for dust control than anything else. To get further stiffening the woofer is then bolted down with 8 machine screws. This is why I'd like to see a cast frame woofer, better stiffening. I am currently constructing two pairs using 1/2" and 3/4" marine grade 14-ply Birch plywood. Each will have 1 1/2" thick baffles and 3/4" thick boards that make up the V behind the woofer. These panels should not be made out of 1/2" per the current factory practice, they resonant like crazy.

John--Animal glue is made from animal remains (bone, marrow, cartilige, hoof and hide). It's been in use for 500+ years. I use it because it has 5 main advantages over synthetics-it's slow to set (a must making a K-horn), it's a gap filling glue, it forms a true chemical bond to the cellulose fiber in wood, you can modify the viscosity by heat/cool and it's expansivity is similar to wood which is why 300+ year old furniture and musical instruments hold together to this day. It's drawbacks are that it has no resistance to water, it has a short shelf life (3-6 months), it's set time is sensitive to humidity and it's expensive. Also, when wet it's acidic so fasteners should be made from stainless steel. The moisture resistance is improved by shellac or poly. Tite-bond sells animal glue called "Liquid Hide Glue". It's in a brown bottle that has a date stamp on it, use within 6 months. I've used it and it works great. For this project, I used a flaked form of glue (add water), a glue pot and a set of brushes.

gffod

Here are a couple more. Notice the "tangs" that anchor the side of the horn to the baffle in pic -026. This is the method used in early vesions.