Horn loaded woofer question

[wuzzzer]

Here's a question that's been rolling around my skull for a while: Is the sound coming from a woofer in a Belle, LaScala and Klipschorn negatively affected by the fact that your ears don't have a direct path to the sound coming from the woofer? All the angles in the cabinets that bend and shape the soundwave before it hits your ears has to affect the sound.

Please don't take this as a chance to start arguments or that I'm questioning PWK's designs. I've never heard any of the above speakers in person.

[seti]

First thing I would say is try to listen to a couple folded bass horn designs. There is a benefit to large unfolded bass horns but they are hard to fit into homes and even harder to sell. I've heard several over the last two months. I'm a firm believer in bigger is better. The more large folded bass horn or straight large bass horn systems I hear the more it seems true. The benefits of horn loading are many. Hopefully someone will came along and get into the details.

[Daddy Dee]

wuzzer, you ask a most interesting question.

obviously, one result of the Khorn folded horn design is that it is crossed at 400hz to the mid driver. However, on balance, would must consider the "difference" in sound of horn loaded bass vs directed bass (which is much more common in implementation).

The question of which "different" is "better" is always at subjective answer. PWK argued that horn loaded bass is less distorted than direct radiated bass.

It took me alot of listening to both before I came to think HLB is indeed less distorted.

[BusaDude]

Let me qualify my response a little before I answer... My main system (6.1 and 2 channel) for many years was a mix of 4 Chorus II's and 2 Forte II's.

Over the past year I've replaced that with 3 LaScalas across the front. They are newer LaScala I's, with one pair from 2003 (AL-4 crossovers) as left and right... and a pair from 1999 (AL-3 crossover), with one of those as center. When I got the first pair (2003's) of LaScalas in my living room, they sounded completely "different" than what I was used to. It took me a while to figure out that part of what was "different" was related to placement and part of it (I think) is that I can hear some cabinet resonance depending on what is being played.

If you take your knuckles and knock on the woofer cabinet of a LaScala (the sides specifically) it does generate some sound/resonance. Does this "negatively" affect the sound coming out of the woofer horn? Or is this just part of the overall "LaScala" sound? To me, in my room, it was more apparent with the LaScalas along the wall. But the left/right channels are now backed into each corner, like a Khorn would be... and I've now lived with them like this for about 6 months and LOVE the way they sound.

Wouldn't trade them for anything at this point, even though I think the woofer cabinet does impart some "character" to the sound. However, the efficiency and "cleaness" of what I'm hearing through all the horn loaded drivers, though it may include some cabinet resonance, just sounds right to my ears... and "better" than what I had with the Chorus II / Forte II setup.

For comparison, if you knock on a Chorus II or a Forte II, I know you will also get some sound/resonance from the cabinet. And that would also impart some sort of "character" to the overall sound of the speaker while it's playing. And unless you build a speaker out of a completely inert substance, there's going to be some cabinet resonance coming from it while it's playing.

My guess is that the Belle (never heard one) and Klipschorn (listened to a few times) would have less woofer cabinet resonance due to the differences in construction. I don't know how to quantify whether that would be "negative", "different" or something else. Maybe it could be measured via frequency response by inputting a test tone and comparing it to what comes out of the speaker. But test tones aren't music, so that would be another variable to consider.

Guess that was just a long way of saying, "I don't know, but it works for me". Best way to decide, is find yourself a pair of Belles, LaScalas or Khorns and give them a listen.

[wuzzzer]

Thanks for the responses guys. I never questioned for a second that the speakers mentioned didn't sound good but it was just something I had wondered about for a while.

[Edgar]

Take a look at the images here, and you will see that the answer to your question is, "It depends." As long as the wavelength of the audio is large compared to the dimensions of the folds or bends, then the sound wave is essentially unaffected. But as the frequency is increased, and the wavelength is reduced, bad things begin to happen.

At what point are they bad enough to be signifcant? It's a judgment call. Some people say that it's at about 1/2 wavelength. Some say it starts by 1/10 wavelength.

[LarryC]

Is the sound coming from a woofer in a Belle, LaScala and Klipschorn negatively affected by the fact that your ears don't have a direct path to the sound coming from the woofer?

This is probably greatly oversimplified, but I'd always understood that, in a horn, the radiating surface is the mouth of the horn, not a relatively small driver cone or diaphragm tucked away in a labyrinth. That mouth gives a pretty direct path to the ear if you can see it. According to that, the sound heard from the K-horn bass horn comes directly from its entire large frontal area.

Edgar's pics seem to display how a wave front propagates through a horn, and arrives at the large mouth delivering the identical frequency as began at the throat:

That very large vibrating exit surface has much less to-and-fro movement than a smaller driver's cone or diaphragm without a horn. That could account for the lower distortion that some hear in a horn. The sound from a horn mouth is also more spread out, which to me gives it more spaciousness.

Those bends are supposed to limit how high the bass horn will go, e.g., the K-horn bass horn won't produce much above 400 Hz. A straight-axis horn would go higher.

[Coytee]

All the angles in the cabinets that bend and shape the soundwave before it hits your ears has to affect the sound.

I think this is one reason they worked on the Jubilee's....to minimize the interaction (interference?) of all the internal gyrations of the Khorn. The Khorn crosses at 400 (but goes up to??) and the Jubilee is crossed roughly 450 but evidently goes up to about 1,000 hz.

I'd speculate that in an absolute sense, the answer to your question is yes?

you should get to Who's Chicago deal. While there, give a listen to Fyrpwr's Jubilee's and (talk about fun) MWM's.

[wuzzzer]

I wish I could, Coytee. I think I'd be saving every cent I made to buy some Jubilees if I did though!

Some day I'd really like to hear a pair of LaScalas, Belles or Klipschorns. There's a pair of Belles for sale locally for $1100. I suppose I could sell my Fortes and go to a 2.1 setup...

[Islander]

As I understand it, folding the horn has some effect on the sound, but mostly at higher frequencies and not very much at all in the bass range.

Straight bass horns may have a slight theoretical advantage, but they're really big and in most rooms they'd be impractical. To show you what I mean, here's a picture that's been seen here a few times. It shows a pair of straight bass horns that are good down to 30Hz (Goto is a brand of very expensive compression drivers):

[chuckears]

Speaking as a someone who does not own one of the models to which you refer (Fortes were all I could afford way-back-when), but who has listened and loved music and film soundtrack material for over 25 years, I would say that a better question would be, "Do these speakers accurately reproduce the sound which is fed to them?"

From the very small amount of listening experience I have with these (K-Horns for an afternoon), I can say that I have never heard more accurate reproduction; never felt as much that I "am there" listening to the actual instruments, vocals, sounds, whatever was thrown at it.

This sound has haunted me for years, but alas.... no corners in my house, and not near enough cash to burn to make that particular audio ghost go away any time soon...

I am not well-versed enough in soundwave engineering to answer your question more specifically, but if you ever get a chance to hear one of these models (properly placed), you will realize that the question is moot. It just works.

[tromprof]

Here's a question that's been rolling around my skull for a while: Is the sound coming from a woofer in a Belle, LaScala and Klipschorn negatively affected by the fact that your ears don't have a direct path to the sound coming from the woofer? All the angles in the cabinets that bend and shape the soundwave before it hits your ears has to affect the sound.

Please don't take this as a chance to start arguments or that I'm questioning PWK's designs. I've never heard any of the above speakers in person.

Every brass instrument in the modern orchestra, and a few woodwinds (bassoon being one) is in a sense a folded horn (think about how wound up a French horn is, and in the end it is pointing away from the audience), so... Of course it affects the sound but if designed well no problem.

[DrWho]

I don't think anyone will tell you that a folded horn would sound better than an equivalent straight horn (except maybe BFM), but how that compares to a direct radiator system is more complicated....and in my mind depends on the bandwidth you're trying to operate at. As you go lower in frequency, the horn needs to get much larger, so the horns tend to be undersized and that causes other atifacts in addition to the folds. Also as you go lower, the comparable DI gains of the horn go down since a direct radiator in a room corner will end up about the same, which just leaves you at the compression ratio difference - and that will impose other distortions at higher SPL's.

[seti]

I have talked to many horn builders about this and there is a consensus that folded bass horns do not voice very well over 700hz even though the perfomance is out to 1khz? PWK crossed the Jubilee at 600hz.

[Islander]

From the very small amount of listening experience I have with these (K-Horns for an afternoon), I can say that I have never heard more accurate reproduction; never felt as much that I "am there" listening to the actual instruments, vocals, sounds, whatever was thrown at it.

This sound has haunted me for years, but alas.... no corners in my house, and not near enough cash to burn to make that particular audio ghost go away any time soon...

Don't despair! If you've got no suitable corners, just get a pair of La Scalas and a sub and you'll be really happy. [Y]

[DrWho]

I have talked to many horn builders about this and there is a consensus that folded bass horns do not voice very well over 700hz even though the perfomance is out to 1khz? PWK crossed the Jubilee at 600hz.

It's all about lining up the polars and distortion response...

[Islander]

Every brass instrument in the modern orchestra, and a few woodwinds (bassoon being one) is in a sense a folded horn (think about how wound up a French horn is, and in the end it is pointing away from the audience), so... Of course it affects the sound but if designed well no problem.

So should a horn that's round like a snail shell, with its infinite number of small reflections, sound better than one that's made of a series of flat surfaces, with its small number of large reflections?

A curled horn, as opposed to a folded horn. Is one better than the other?

[Edgar]

A curled horn, as opposed to a folded horn. Is one better than the other?

In my opinion, based upon the physics of the situation and not based upon any listening tests: at high frequencies, reflectors should be better; at low frequencies it shouldn't matter (though an argument could be made that curling could be better at really low frequencies). As indicated earlier, the definitions of "high" and "low" refer to the relative sizes of the horn and the wavelength, not to any absolute numbers.

Greg

[PrestonTom]

What the designer is worried about on the folding is that it can act as a low pass filter. It is best to think about it terms of the outside length and the inside length of the walls. If these lengths are very different, then the wavefront can have a max in pressure on one side and a relative min in pressure on the other side (actually opposite sign). This will occur as the wavelenghts are shorter (ie higher frequencies). This can cause the low pass filtering.

A few of things the designer can do to minmize this problem are 1) bifurcate the horn (this is done on many of the Klipsch models, as opposed to some types of "scoop horns"), 2) "reverse" the fold, that is, use a "W bin". Then the "inside", or shorter distance, will then become the "outside" or "now longer" distance. This done on the Jubilee bass bin for instance, 3) additionally any major folds should be done closer to the throat where the "differences in distances" of the inside and outside walls are smaller to begin with.

With a coil or "snail" geometry there is no "reverse" in the folding and the differences in the two lengths simply continue to increase.

The above arguments relate to the low pass filtering, there may be other considerations, or the filtering may not be concern at all.

-Tom

[Islander]

A few of things the designer can do to minmize this problem are 1) bifurcate the horn (this is done on many of the Klipsch models, as opposed to some types of "scoop horns"), 2) "reverse" the fold, that is, use a "W bin". Then the "inside", or shorter distance, will then become the "outside" or "now longer" distance. This done on the Jubilee bass bin for instance, 3) additionally any major folds should be done closer to the throat where the "differences in distances" of the inside and outside walls are smaller to begin with.

With a coil or "snail" geometry there is no "reverse" in the folding and the differences in the two lengths simply continue to increase.

That sounds very logical, Tom. However, if the curled horn had an "S" bend to even things up, factoring in a different radius to allow for the increasing horn diameter along its length, that particular problem could be solved.

Doesn't the horn-loaded Bose Wave clock radio use a sort of zig-zag horn design to produce its "room-filling" sound? You can't argue with Better Sound Through Research ... [][bs]