Corner speaker identification...

[Audible Nectar]

Does anyone here recognize this? It's a pic a friend sent to me - he was curious what it is. The location makes it tough to look behind it - just wondering if the model is obvious to anyone here. It looks like an early Klipschorn/Speakerlab/EV/Altec.

[ben.]

Off the top of my head, it looks like a Patrician. Try poking around at www.hifilit.com

[hwatkins]

Also take a look here:

http://community-2.webtv.net/KerrB/VINTAGETUBEAMPHORN/page4.html

[fini]

I am going to (once again) show my ignorance, and ask the question: Why, in the Klipschorn (and the Patrician and other horns) is the cut-out in the panel to which the woofer is attached not round? I have seen this also with front-firing horns as well (Altec VOTs). Intuitively, I would guess it has to do with controlling the directivity of the sound waves as close to the source (the woofer) as possible. Have there been attempts to shape the woofer itself differently?

[HDBRbuilder]

Fini,

That more-or-less rectangular slot in the woofer motorboard "loads" the woofer (puts the soundpath under pressure) into the throat of the horn lens, and provides some directivity to the initial bends in the horn lens (in this case, the "splitter" directly in front of the slot which begins the bifurcated pathway of these types of bass horns). If you notice on these bass horns, the splitter is in the same parallel plane as the slot in the motorboard.

Early on, PWK tried a "rubber throat" at that point in the motorboard, with the idea that the 12" driver he used at that time would "read the throat size" and would "adjust itself" to the load needed for the frequency bands being reproduced, but it did not work the way he hoped it would, so he went back to the slot as he continued with development of the bass bin, later using a 15" driver. Edit: For more info on this "rubber throat", see Gil's post below.

Look at it this way...it is like having a rifle that has no shoulder to its cartridge. The cartridge shoulders direct the energy of a larger diameter casing to a smaller diameter rifle bore...but bullets are by necessity round (in most cases).

In the case of the bass horn lens, as opposed to the bore of a rifle, the soundpathway immediately becomes rectangular as it expands exponentially towards its mouth. The woofer CONE is much larger than its voice coil assembly and needs to push lots of air, which is compressed (loaded) behind the motorboard so that it fires through the slot, with the slot being the first rectangular plane that the moving air passes through on its journey through an exponentially-expanding rectangular horn lens.

On a LaScala or Belle Klipsch, the bifurcated soundpathway past the motorboard is split on a vertical plane to each side, which makes their motorboard slots vertical; whereas on the Klipschorn and its derivatives, the bifurcated soundpathway past the motorboard is split on the horizontal plane, with half the energy going up and the other half going downward, therefore its slot is on a horizontal plane.

If the horn lens was designed to be round from the motorboard all the way along its axis, then a round slot would work better, BUT round folded horn lenses fired by cone drivers are very difficult to construct using a series of flat wooden panels.

The larger slot PWK tried for a short while, which was twice the width (6" x 13")of the standard slot (3" x 13") on the K-horn's bass bin did not load the woofer driver quite as well (for what he was looking for in performance) as the narrower slot did, so he went back to the narrower slot, which is still in use today. The tests did not show lots of difference, but there was ENOUGH difference, so he went back to the original narrower slot size. There is still debate on whether the wider or narrower slot size is the best performer, but with the particular woofers PWK intended to use in the speaker, the narrower slot won out...if for no other reason that its smaller width provided more structural integrity to the motorboard itself...IOW, the smaller the hole, the stronger the motor-board in resisting resonances perpendicular to the soundpathway.

I am far from being any kind of expert in speaker design (I just build them), but that is what I gleaned from my time at the plant when listening to engineers talk about things they were doing and trying-out. You gotta remember that playing around with different things on the bass bin, crossover networks, etc., was always going on...engineers LOVE to tweak things, test out theories, etc. PWK had tried all sorts of things and he liked to have the engineering staff try out their ideas, too...so they did so. Besides, when those engineers on the staff tried out things, it gave them a chance to become more intimately familiar with horn designs, including HIS horn designs.

The Klipschorn's rectangularly-cross-sectioned bass horn lens both bends AND rotates through its soundpathway. It starts out with its long rectangular axis running left to right after it hits the splitter and bifurcates upward and downward, then AT its bends on these two pathways to the REAR towards the corner, it initially has its long rectangular axis remaining left to right, but ROTATES that axis 90 degrees as it heads towards the corner so that at the point where it exits the slots on either side of the rear of the bass bin its long rectangular axis is top to bottom, then the bifurcated pathway becomes joined to a monopathway at the end of the rear of the pyramid, and as it hits the tailboard where it bends, and exits around each side of the rear of the cabinet, it becomes bifurcated yet again, using the walls and cabinet sides to continue that up and down long rectangular axis, BUT with the final flair extending to the left and right between the cabinets sides and walls. PWK's genius was in understanding how to make the ROTATION of the rectangularly-cross-sectioned horn lens towards the corner work right so that he could have such a large horn fit into such a small space.

The LaScala and Belle Klipsch bass bins ALSO have a rectangularly-cross-sectioned horn lens. The soundpathway is bifurcated in front of the motorboard to the left and right. Its flare rate expands on the vertical axis, which is also the long end of the lens' rectangular cross-section (vertical), until the bifurcated soundpathway hits the inside of the rear corners of the bass bin, whereupon it not only bends forward around the doghouse, but its FLARE RATE ALSO rotates 90 degrees so that its FLARE RATE is left to right (horizontal axis) instead of up and down...BUT, its rectangular cross-section axis REMAINS up and down! The Klipschorn's FINAL flare rate expands outward towards the room walls, whereas the LaScala's (and BK's) expands inward toward the vertically-oriented peak of the "doghouse roof".

The woofer bass bin of the MCM Grande, called the MWM, is a "W" horn, it fires toward the rear with its flare rate from left to right (horizontal-axis), then its soundpathway bifurcates at the rear and fires around the sides, of the center section, BUT its flare rate REMAINS left to right (horizontal axis), with NO 90 DEGREE ROTATION of the rectangular cross-section, OR its flare rate orientation. Because the initial MONO soundpathway on the MWM flares from left to right towards the rear (horizontal axis), its slots are left to right on its motorboard axis, but its slots are NOT as narrow as those on the K-horn, BK, and LaScala. The final flare rate of the MWM as it fires forward is to the outside of the cabinet from left to right (horizontal plane).

The Jubilee fires forward to a vertical splitter that sends its soundpathway bifurcated to the left and right...with its rectangular cross-section long axis running up and down, BUT with its initial flare rate ALSO running up and down to each side. As each side bends towards the rear, the rectangular cross-section REMAINS up and down, but as these soundpathways follow two "S" horns towards the rear and then back toward the front to each side, its FLARE RATE rotates 90 degrees FROM its initial flare rate to each side from the splitter. IOW, the flare rate starts on a horizontal plane from the first rearward bend of the soundpathway.

It is lots easier to explain with the bass bins in front of you than to do it with words. One thing about PWK was that he could THINK about things THREE-DIMENSIONALLY, which is how he came up with his designs! Trying to EXPLAIN it three-dimensionally is difficult, at best, without having the bass bin in front of the audience to SHOW them how it works!

A round horn lens' flare rate expands along its axis continually in a 360-degree cross-section, but when dealing with rectangular-cross-sectioned folded-horn lenses that have the flare rate PRIMARILY on just two opposing sides of that rectangular cross-section, you can ROTATE the flare rate by "twisting" the lens as it meanders around THROUGH ITS BENDS.

Simple, HUH?

[gullahisland]

WOW - HDBRbuilder! I just learned more about PWK's design in the last 10 minutes reading (and digesting) your post than I have in the last several months.

Very concise and infinitely informative.

BTW - Very insightful question, fini.

[Parrot]

Maybe PWK is channeling through Builder? That is some post there, Andy!

[Klipschfoot]

I have started a folder called Klipschnotes into which I shall paste posts such as HDBRbuilder has to offer. This is textbook stuff.

[fini]

Andy,

Brilliant (as usual). I guess I was sort-of on the right track. I need to dig into the Dope from Hope that Artto generously copied. Thanks!!

I've seen links here to a few short PWK video clips. Is anyone aware of any regular longer length video pieces of him talking about designs, etc.? Man, THAT would be a hot seller here...

[WMcD]

I'll give some comments. All are related to getting the K-Horn bass driver to perform up to 400 Hz, where it is falling off.

If the throat cut out was round we would have a problem with path length. The pressure from the center of the driver diaphragm would enter the ducts and travel up and down with some delay because of the propagation distance. But as we get to edge of the round cut out, we'd have the pressure wave from the edge of the diaphragm, which is not delayed. There would be some delay-phase interference.

The bottom line is that we're better having a pressure chamber formed in front of the diaphragm where there is some uniformity of the pressure squeezed out the slot. In the up-down direction, it looks more like a point source.

Long ago I'd published here a theory of why PWK would use a small slot. There was in the literature a theory that a pressure chamber in front of the diaphragm will cause a spring action which can resonate with mass of the diaphragm to keep up the high end. As Andy indicates, the 3 inch versus 6 inch slot makes some difference. Which is better is debatable. And why it is different is debatable too.

But maybe the path lenght of the 3 inch versus 6 inch slot is part of the reason they are different, and not my theory. I'm sticking to my guns on pressure chamber. A three inch difference in delay does not count for much at 400 Hz.

I was not aware of any rubber substance in the throat as reported by Andy. He was at the factory and I just read publications.

OTOH, PWK's orginal design used a 12 inch driver with a small throat. This meant that the inital flare rate was higher than the rest of the horn. The result is that at high frequencies, the driver "sees" a small throat, while at low frequencies the driver "sees" a big one.

If you read the original paper by PWK, this is what he is talking about. Harry Olsen (a big player) had suggested it would improve high frequency response.

PWK called this a "rubber throat". At least in this, there was no rubber, just that the plywood structure presented a different effective throat size because of the flare rates.

The standard K-Horn uses a 15 inch driver and a bigger throat area than what we read about in PWK's initial paper. My read of 15 inch type is that the flare rate overall is an Fc of 48 Hz throughout.

I must make this point again for clarity. PWK's paper describes a plywood structure of varying flare rate. He called it a rubber throat. The production models don't have this. OTOH, the Jubilee does. (Gosh this is getting difficult. I think the Jubilee does only because PWK and Delgato are trying to match the footprint of the K-Horn. Another story.)

Andy brings up some very good points. Even with this uniform 48 Hz expansion, there is something odd going on in the second of the three sections of expansion.

It is the section giving a transition starting at the turns at the top and bottom in the front (horizontal slot) and traveling to the back, where it ends up as two stacked vertical slots at the tail board.

This type of arrangement has not been used in other Klipsch designs. Andy is descibing such. It may be the cause of high frequency problems which were blamed on the throat.

All for tonight,

Gil

[fini]

OK. My brain is officially jelly now.

[wrench_peddler]

Fini, Here is one to think about. What if a square Kicker Solo-Baric 15" woofer were mounted behind the slot? I wish I had a spare bass bin and a 15" Solo-Baric.

[johnnyp]

Gil,

...."The bottom line is that we're better having a pressure chamber formed in front of the diaphragm where there is some uniformity of the pressure squeezed out the slot. In the up-down direction, it looks more like a point source...."

I wish you had written some of my text books. Uniformity of the pressure wave through the slot and into the throat must be important.

The pressure wave is generated by a round, concave (from the slot's perspective), oscillating diaphragm. Because of the concave shape, the distance from the diaphragm to the slot is variable. At the slot extremes, the diaphragm is closer to the slot. Does this mean the sound passes through the slot at the extremes first? I've wondered for a long time if another slot configuration, instead of a rectangular one, would provide a more uniform pressure wave into the throat?

Do you think a lemniscate or "butterfly-shaped" slot (dimensions unknown) could more uniformly load the throat?

[hwatkins]

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On 4/18/2004 12:28:07 AM fini wrote:

OK. My brain is officially jelly now.

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An improvement in some folks opinion....

[fini]

Henry,

This morning it's toast. This should make everyone happy...

[HDBRbuilder]

Gil,

Thanks for clarifying what I meant when I said "rubber diaphragm" instead of "rubber throat". I am aware it was not a rubber material used at that point, and I will change the wording of that section of my post. I spent a lot of time editing and re-editing that post before I posted it, and sometimes I just fail to catch some of the things I write that may be mis-construed by some of the forum folks.

Lots of people don't realize that PWK continued tweaking on the K-horn for his entire life, trying to improve it without sacrificing anything in the process. Many people also don't realize that the early development of the K-horn used a 12" driver...as did the early LaScala. As a matter of fact, the earliest K-horn bass bins developed had the woofer driver in a "box" ahead of the bass bin front firing REARWARD, instead of its being loaded into the pyramid, firing forward. On those early prototypes, having the woofer ahead of the front of the cabinet allowed PWK to test out drivers AND motorboard configurations (such as the slots used for loading the woofer into the bass horn) without having to completely rebuild the cabinet , AND it made doing these things MUCH easier.

The early LaScala versions had the bass bin rotated 90 degrees, with the "point" of the doghouse "roof peak" on a horizontal plane instead of on the vertical plane. This made access to the woofer driver through the side of the cabinet, instead of through the top or bottom on these early versions.

Since the final expansion of the flare rate is between the roof of the doghouse and the side of the bass bin opposite those two sides of the doghouse roof, then the expansion of the wave in those early models would have been on a vertical axis, instead of a horizontal axis...kinda like laying a midrange horn on its side...with the final flare from each side of the doghouse roof peak doing a sort of "crossfire" towards the front, but on the vertical axis. By rotating the orientation of the bass bin 90 degrees, this expansion of the "crossfire" became on the horizontal axis...IOW, better horizontal dispersion. Another advantage of the rotation is that it took the woofer access door off the side of the cabinet, which made it more aesthetically pleasing.

For a time after that change, the woofer access door was in the top of the cabinet, which made changing out a woofer a real PITA, so the change to the access door being on the bottom of the bass bin came about...and this ALSO provided a structural reinforcement at the bottom of the bass bin, further somewhat reducing any tendency for cabinet resonances in that area. Another advantage to having the door on the bottom was "wear and tear" to the bottom of the cabinet...REMEMBER, the LaScala was designed as a stage speaker...so moving it around on stages, dragging it and such, caused lots of "wear and tear" on the bottom of the cabinet. Prior to the change to having the woofer door on the bottom, in order to replace a damaged bottom it required "major surgery"...whereas by putting the access door on the bottom, all that was required was unscrewing the worn out panel there and replacing it with a new one...IOW...no glued and nailed-on panels to remove while trying not to tear up the cabinet.

[HDBRbuilder]

Fini,

You asked about making rectangular woofer drivers. Well, there have been some square and rectangular woofer drivers made over the years, but the cost of making them is ENORMOUS when compared to the cost of an "off the shelf" driver. Remember, PWK did NOT make his own drivers, and he intended to keep costs of his speakers to the consumer down by usng more affordable drivers that were already in manufacture...with, if necessary, minor adjustments to the manufacture of these "off the shelf" models to meet his particular specifications needs. That way he did not have to bear the burden of being the sole purchaser of these out-sourced drivers for his speakers. Small purchases of unique drivers means HIGH COST per unit.

One interesting aside on woofer shapes are the ones Yamaha developed in the early 70's for a series of speakers they marketed. Yamaha got its start by making string musical instruments, in particular...PIANOS. They developed an aluminum alloy casting for the strings of their pianos to be mounted to, and were successful in making it work. Prior to that time, the strings were mounted to wooden frames. Their use of this aluminum alloy casting greatly reduced the cost of wood and labor used in the building of their pianos. The fact that they soon built their own aluminum foundry to cast these frames led them to take on other aluminum casting work, such as aluminum engine blocks and such...which eventually led them into making their own engines...then motorcycles...etc. Anyway...back to the point here.

In the mid-70's they developed a woofer cone shape that mimicked the soundboard shape of a grand piano, and touted that heavily in their marketing for those speakers using that woofer shape...saying things like "we have years of experience in building pianos famous the world over...now our speakers have some of that technology and experience in them". Needless to say, those speakers were quite expensive just because of the unique woofer cone shape they used, and they did not do well in sales back then...especially when folks blew a woofer and had to swallow the cost of replacing that expensive thing!

Another interesting aside about how Yamaha got into the electronics end of things. It started out with electronic musical instruments... originally a few electric guitars, and particularly electronic pianos! One story is that back in the 1960's, Stevie Wonder wanted an electric piano to use while touring, instead of hauling around a fill-sized grand piano (meaning he had to have the thing re-tuned prior to each appearance after it had been CAREFULLY unloaded!), but nobody was making what he wanted...so he contacted Yamaha with his specific wants and needs, and they built one just for him. With the research and development for that piano out of the way, that got them started in manufacturing easily portable electric pianos..which led to complex electronics manufacture, which naturally led to the rest of their electronics story. Remember, back in the mid-60's, Yamaha was doing well in both their musical instruments AND in their small motorcycle exports, so they had tons of money to commit to expansion into other realms!

[tubelover]

Thanks for the information on the La Scalas