This is V interesting, as I am going to hear horns for the first time this very weekend. A new friend has invited me to listen to his system which includes the RF-7 Klipsch Speakers with [Dean xover]. His system also includes a Rotel RB 1090 power amp, Audio Research SP 11 pre amp and a Sony DVP NS9000ES SACD player [upgraded to level 5 by Vacuum State]. Anti-cables for speaker wire and Cat Cables Kingcats for interconnects. Velodyne DLS 5000R sub, & eight ASC Tube/Bass Traps.

As far as your numbered bullets:

1. I can't remember.... are the dimples to lessen chuffing from the port?

2. Resonance is typically bad when associated with cabinets, and rigidity is typically a good thing when speaking about speaker cones. As far as horn applications, I could only guess.

3. It would have to be measured. I know wave guides are V popular for use in cone and dome tweeters recently for increasing dispersion angle, and they are made of ABS plastic in some cases.

Defraction of the sound wave due to the baffle edge is a main concern in typical 'box' type speaker design and performance. It can easily be modeled and tested. ( I have actually mounted the tweeters off-center of the vertical axis on my own speakers to distribute the defracted frequency over a wider range and not have it concentrated at one specific frequency).

Adding dense wool around the tweeter is a method often used to deal with defraction in the higher frequencies.

4. Rounded ports for LF are typically preferred, but again, as far as I know, chuffing is the biggest culprit with squared ports.

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I got one answer from a horn expert and he stated that smooth horn surfaces (independent of the composition of the horn) are key. I never really "knew" that, so I'll take his informed word on it!

Yes, smooth transitions are a must to lesson defraction.
Also, this is one reason you see todays speakers seem to be so narrow compared to the laargest driver diameter. There is less baffle to interact with the sound wave.

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What would it do for the sound of a horn if the actual horn itself was dimpled like that?

The dimples on the B&W ports supposedly add velocity which results in less port noise. Since a port and a horn function differently from each other I doubt that dimples would matter much one way or the other to most horns.

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2) When you listen to a horn speaker, how much of the sound is affected/produced (?) by the surface of the horn, anyway? I don't even know how to begin to answer that question. Without resonances figured in, would the material the surface of the horn is made of make a difference? Would a wood surfaced horn sound different from plastic or metal? Again, this is assuming no resonance effect. I would think that "smooth is smooth" with regard to the horn surface, eh?

If there is no resonance, there is no sound other than the wave front produced by the driver. Therefore all materials would be the same. That, however, is not how the real world works. The throat of a horn resonates. You can construct the horn to resonate less or, as some manufacturers choose, more. Metal is not in favor since it doesn't lend itself to molding as easily as more "plastic" materials and has a characteristic sound. Though "plastic" is seldom if ever used in the construction of a horn throat. If I remember correctly, the throats of the classic Klipsch speakers were a composite material somewhere between Bakelite and fiberglass, leaning heavily toward fiberglass. I haven't read what the current owners have changed, if anything, in the construction of the horns for the larger Classic Series Klipsch speakers.

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3) How much do resonance effects affect the sound of a horn? I've never really seen modders or manufacturers go after the idea of damping the putside of a horn to make the speaker sound better.

Obviously, resonance is not in the original signal, so it affects the sound you hear. Unless you build a horn throat to intentionally resonate such as a musical instrument would resonate, resonance in the horn itself will cause additive and destructive interference to the original signal. There's not much point in modifying a poorly constructed horn. Most modifiers would seem to prefer to just buy or build a better horn. Building your own horn throat is similar to building your own sailboat. It is a right of passage.

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I recall that old Klipsch horns were metal, and they changed, but I don't if it was because metal horn materials "rang" or if it was a cost saving maneuver.

It's easier to injection mold a "plastic" horn throat with bracing included to minimize problems.

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I was thinking of making a glue/sand or liquidy rubber/sand mixture and then masking off the interrior and driver parts of the horns and then dipping the outer part of the horn into the mix to create a seamless damping layer around the outside of the horn. Any idea what it might do to the sound?

No. It would result in a rather uncontrollable damping material. The problem would be you will modify the sound of the Klipsch in ways that are unpredictable and possibly undesirable. If you like the sound of the LaScala, then that's what you are buying. If you don't like the sound of the LaScala, then there's no sense in trying to modify it to build something you like. Start from scratch with drivers and horns you prefer.

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3) In the big picture of the La Scala, you can see that the horn mounts are on the back of the speaker's baffle (see picture above.) Would either...

A) Moving the mount so it is flush with the baffle make a difference?

Yes, you would shorten the length of the horn's throat which would shift the efficiency of the driver, creating a mismatch beween the various driver/horns in the system. It's possible you could also change the dimensions of the horn mouth which would shift the low frequency cut off of the driver/horn combination. One of the advantages of a horn loaded midrange or tweeter is the natural frequency response roll out determined by the dimensions of the horn mouth. Below a determined frequency the response rolls off gradually and this mechanical roll out can be incorporated into the crossover of the speaker making the need for high order electrical crossovers unnecessary. Changing the dimensions of the horn would change that roll out point and alter the crossover of the speaker system.

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B) Sanding out a continuation of the horn's shape into the baffle make more of a difference, or could I do more harm than good?

Unless you know what changes you would affect, it's better to not pull out the Dremel tool just yet. You are buying the LaScala because you prefer it's sound. You can find the math to determine what changes you might affect. But then you won't have a LaScala.

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C) Applying a damping layer like felt around that inner baffle area make a difference?

I assume you mean around the horn's mouth and appplying the felt to the wooden front baffle. It shouldn't make any difference to the LaScala. Another advantage of a horn loaded driver is the directivity of the horn. The shape of the throat/mouth determines the dispersion of the horn, but typically a horn produces a very directional sound. Unlike a dome shaped driver which theoretically produces sound in a 180 degree field, a horn is meant to place sound in a particular area. You choose a horn based at least in part on its particular dispersion pattern. This somewhat specific dispersion/directivity makes them quite good at getting sound into a specific location and at keeping unwanted sound away from unwanted locations. If you were to try using a dome tweeter in an auditorium, most of that 180 degree wide dispersion would be wasted power which would result in unwanted reflections. A horn can "place" more acoustic energy into a more specific area and avoid those same reflections. There is virtually nothing to damp directly to the sides, top or bottom of the horn's mouth.

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4) For the bass, would creating a "rounder" path for the horn's travel passage be a good idea? You know, taking the sharp angled apsects and maybe putting in some "curvier" inserts to make the "horn's" path maybe less reflective?

You would then be shaping an expotential horn as opposed to a straight horn. The effective length of the horn would change slightly, though, considering the dimensions of the LaScala, not sufficiently to justify the more difficult construction and the less rigid final product. Paul Klipsch built with plywood for several reasons, one of which was its ability to create simple structures. The LaScala was specifically designed as a P.A. speaker which eventually found its way into the home market. (Though the similar but higher priced furniture grade Belle Klipsch was the better speaker while still using a double fold bass horn and identical mid and high frequency drivers to the LaScala.) The dimensions of Paul's designs were technically correct while being built to minimize waste material. Building an expotential bass horn would add considerably to the waste material or would significantly alter the sound of the LaScala. If you want the benefits of a longer horn throat, buy the corner loaded Klipschorn. The "sharp angles" of the bass horn have little influence on the wave path unless the horn is very poorly constructed.

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3) How much do resonance effects affect the sound of a horn? I've never really seen modders or manufacturers go after the idea of damping the putside of a horn to make the speaker sound better.

I recall that old Klipsch horns were metal, and they changed, but I don't if it was because metal horn materials "rang" or if it was a cost saving maneuver.

Many klipsch heritage owners with metal horns have wrapped them with a material called "Dynamat". This stuff is often used by car audio nuts too, for things like lining the inside of sub boxes or even the inside of a car trunk. I've also known some to wrap rope caulk around their metal horns. The plastic horns have molded in ribbing and most people leave them as is.

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3) In the big picture of the La Scala, you can see that the horn mounts are on the back of the speaker's baffle (see picture above.) Would either...

A) Moving the mount so it is flush with the baffle make a difference?

B) Sanding out a continuation of the horn's shape into the baffle make more of a difference, or could I do more harm than good?

C) Applying a damping layer like felt around that inner baffle area make a difference?

According to Paul Klipsch, whether the horn is mounted on the front or back of the baffle "doesn't make a dime's worth of difference" in the sound. It was originally mounted on the back simply because it was more feasible from a manufacturing point of view. The grill cloth would have been pushed out by the lip of the horn unless they would have then also flush-mounted it into the baffle.

I think all current heritage models do have front-mounted horns. I suspect it was done more to appease audiophiles and the marketing department than anything else. Although, that said, IMO it can't hurt!

As for beveling off the plywood around the horn to create a more seamless path, I would be very careful not to get into the mounting screws that are coming through from the back. Besides, like PKW said, "it wouldn't make a dime's worth...yada-yada.

The concept behind a horn type speaker is to match the speaker cones impedance to the impedance of free air.
This will maximize energy transfer providing maximum output power with minimum input power. There are various types of shapes to get from the throat end to the final opening, each having advantages and disadvantages. Yes, they all are curves, but it is the rate of change of the area that is important and not just the shape of just one dimension.
Because of the size of a low frequency wave length a properly designed low frequency horn is not pratical. The length and opening of the horn will be larger than most rooms. True that one would not want the surface of the horn to resonate.

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The length and opening of the horn will be larger than most rooms.

Or, as with any corner loaded bass horn, it will be the room.

Thought I would share a pic I found while surfing analog stuff......

[The image linked to is a composite of three photos taken by Richard Foster and stitched together by Steve Clarke of The Analog Dept].

Nice, but kind of unimaginative.

http://www.soundsolutionsaudio.com/forum/index.php?showtopic=10834

Thanks Jan!!!!
Now I have to clean my Bombay gin & tonic off of my monitor.
PPPPFFFFHHHHHHit!@@#!@#!%%

Can we please get some measurements from J.A. on this?
I can be pretty sure that this system is not time aligned.

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Thought I would share a pic I found while surfing analog stuff......

I can just imagine the crossover network for these monsters.
Hey, is this what they mean by "the wall of sound"?

Great story, Budda!

Please feel free to ramble any time!

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That

I am guilty of 'stacking Advents'.
Gosh, what we did in those old college days..........

Can't remember whether it was Stereo Review or Audio magazine. I saw a picture and description of a system that uses, if I remember correctly, three 11'x11' horns that was cast in concrete, with the midranges/tweeters etc., arrayed in front (not time-aligned either?), the entire horns facing into a large room. The system and listening room was literally another house. They were running the system with a bank of Phase Linear power amps.