That's not true at all. They sound bad, that's why NO ONE uses them anymore. Why is that do you suppose? Myth?
Not really true on so many counts. (Exaggerate much?)
They are still the most popular horn types for PA and cinema use. They have the best polar response and most constant directivity (which you should appreciate if directivity control is key, as you say).
Note that, far and away, the largest use of horns throughout the world is in high level coverage of mass audience areas. Use of horns in a domestic situation is a very minor application. For pro use, CD horns of a traditional designs and brands far outrank the use of any "waveguide" type designs. Pros must have well controlled directivity in reasonable coverage patterns (90 x 40, 60 x 40, etc.) Pros can not use a waveguide aimed away from the audience to avoid on-axis response problems.
I have not met any professionals who would generalize that they "sound bad". If they sounded bad they would not be used.
Earl, your argument is always circular:
HOMs are an especially nasty audible effect.
Diffraction based CD horns have high levels of HOMs.
My waveguide is HOM free.
Yet HOMs are hard to measure and I can't be bothered.
David
The measurements Mr. Leclèac'h described includes HOMs but also contains lots of other things mixed together. HOMs originate inside the horn, so the best way to measure is inside.
I'll let the audience judge this one. Its pretty clear where the industry is going. And anyways this is not a professional forum so what professionals like is irrelevant.
So, hard to detect outside of the horn. Tell me again why we are so concerned about them?
David
To tell you the truth David, I think if there is a way to better optimise horn performance, I look into it first. But I have not made a horn/driver combination to my satisfaction yet. No plans to concentrate on it soon this year. However, having posted some goals I think of valid consideration, which would also be part of my own goals when I pick up on it again, I think the measurement method does provide help in the optimisation process. The tradeoff might be what kind of radiation pattern and frequency response, etc., so if you weight more focus on these issues, then you might not be so concerned. It really depends on how you weight these factors in the design.
The most dominant issues I find are that the speakers do not decay fast enough, HOMs is part of the issue, but since you do not have so many reflections in the horn, they do not sustain, so what you will end up hearing is some smear in the focus just like what diffraction causes. If you can get drivers to decay fast enough, then you start to worry about this smear.
FWIW, my interpretation of HOM is different from the way Earl describes it; from his description in his waveguide thread, it is not a "mode" as we interpret in structural, listening rooms, etc., but I do understand his consideration. His foams will help breakup modes just like filling your room with something like that to scale. The way he uses the sub placement acts in a similar manner.
Now if someone says that HOMs are more irritating at higher levels, I would first investigate whether the driver is ferro fluid cooled, these types of cooling do provide a rougher listening experience even at dedicated listening levels.
The most dominant issues I find are that the speakers do not decay fast enough, HOMs is part of the issue, but since you do not have so many reflections in the horn, they do not sustain, so what you will end up hearing is some smear in the focus just like what diffraction causes. If you can get drivers to decay fast enough, then you start to worry about this smear.
FWIW, my interpretation of HOM is different from the way Earl describes it; from his description in his waveguide thread, it is not a "mode" as we interpret in structural, listening rooms, etc., but I do understand his consideration. His foams will help breakup modes just like filling your room with something like that to scale. The way he uses the sub placement acts in a similar manner.
Now if someone says that HOMs are more irritating at higher levels, I would first investigate whether the driver is ferro fluid cooled, these types of cooling do provide a rougher listening experience even at dedicated listening levels.
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Actually the issue of directivity is rather involved and the more asymmetric a horns pattern is, the more dramatic the pattern flip is below the pattern loss frequency.
The reason the old Electrovoice T-35 /T-350 was often run “up and down” instead of the way the horn points is the pattern flip began about 8Khz so most of it’s range it was already flipped.
To avoid pattern flip AND have significantly different horizontal and vertical pattern angles, the simple horn shape no longer applies.
For a horn that had an 80 degree horizontal angle and 20 degree vertical angle must have a mouth that is 4 times taller than it is wide. This is more or less the opposite profile one gets making a simple pyramidal horn and is why none of our pyramid shaped horns at work have an aspect beyond about 1.5:1.
The solution is what people are calling a diffraction horn. That allows the vertical and horizontal angles to begin at the mouth and like an astigmatic lens, there are two focal points, one close and one far.
Just like with the driver exit though, the wave front shape, size and desired upper frequency limit governs how wide that slot can be before it produces modes.
Remember to drive the throat of wide angle horn coherently, it can’t be more than about ¼ to 1/3 wl across and that makes the design potentially problematic here as well as the driver end.
At work, we have several very large full range horns mostly used in sports stadiums, WAY more powerful than concert line arrays and having way more directivity (as in much less sound radiated outside the desired pattern).
In order to get a low pattern loss frequency, the horn has to be large, in order to radiate a great deal of acoustic power, you need to have a lot of drivers. To give an idea, one of these is ten feet tall and four feet wide and has over 100 drivers.
This means using a “diffraction horn” the slot is not only too large but much too large to radiate properly.
The layered combiner we use at work allows one to drive that slot from a number of layers where the sound emerges in the center first and the edges last. One can passively present the final flare with a wavefront that when you get up high, that is already curved to match the exit angle. Thus, a very large diffraction horn’s cd behavior, without the need for diffraction at the slot.
Here is one version of the combiner, using path length delay, this one produces the bottom half of an 80 by 80 horn using three drivers and used in the first of these "large" horns.
Patent US20120328140 - Horn enclosure for combining sound output - Google Patents
Best,
Tom
You posed it as "no one" and categorically as "bad sound". Saying the statements were "over-broad" would be an understatement. 😱
Having heard several designs, those that measured well with good linear decay over a range of axis, did not display any "bad" audible behavior that was a function of the diffraction. Instead the problems I had were always in relation to the limited dispersion. (..I know, ironic given that their use was specifically for greater dispersion.) (..I also had problems with a "forward" emphasis.)
My problem with limited dispersion and the forward emphasis could largely be eliminated with a second unit on the rear for bipolar or dipolar reproduction. (..note this was both in a "live" room with the speakers well away from the walls, and in a "dead" room close to the walls.) ..still, "largely" wasn't enough for me - I seem to require greater dispersion below 5 kHz (..closer to +/- 90 degrees) to get the full soundstage width from the recording.
I'll also note that the JBL design that you criticized for diffraction effects (from the mouth) that Zilch presented to you, seems to be rather well received by a *very* large number people, none of whom I've seen so far are complaining about the horn's diffraction with respect to sound quality (..though I'm sure there are some, I just haven't seen any). Most of the time when I see complaints about the "econowave" - it seems to be more focused on the midbass driver, or like me.. on the limited dispersion. (..Gainphile had this problem.) Speaking of Gainphile and econowave:
Econowave - YouTube
..not bad really given the format and mediocre cam recording. 🙂
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Originally Posted by speaker dave View Post
I have not met any professionals who would generalize that they "sound bad". If they sounded bad they would not be used.
David
It has been pretty clear for the last two decades that line arrays are where much of the pro sound industry has gone.
Other than those using tiny dome tweeters or ribbon transducers, line arrays use some sort of high frequency diffraction device coupled to a horn/waveguide.
In the same two decades, there has been trend for smoother horn/waveguide, transitions for smaller applications, much of the changes seems fashion oriented, but the elimination of knife edges in horns is generally a good trend, and the reduction in diffraction is easily measurable on smoother horns.
Since a reduction in diffraction is fairly easily measurable, and HOMs are not, I'll let the audience judge which is the more important.
Art
I have not met any professionals who would generalize that they "sound bad". If they sounded bad they would not be used.
David
Well, the forum may not be all that professional, but there are a few professionals still here 😉.
It has been pretty clear for the last two decades that line arrays are where much of the pro sound industry has gone.
Other than those using tiny dome tweeters or ribbon transducers, line arrays use some sort of high frequency diffraction device coupled to a horn/waveguide.
In the same two decades, there has been trend for smoother horn/waveguide, transitions for smaller applications, much of the changes seems fashion oriented, but the elimination of knife edges in horns is generally a good trend, and the reduction in diffraction is easily measurable on smoother horns.
Since a reduction in diffraction is fairly easily measurable, and HOMs are not, I'll let the audience judge which is the more important.
Art
I corrected the mouth diffraction on that horn by utilizing open cell foam, shaped to loosely track the profile and provide a termination. This dramatically reduced the ringing and pattern flip at cutoff, and improved the sound substantially.
An externally hosted image should be here but it was not working when we last tested it.
Why would you think that there are no current systems using horns with diffraction slots?? Look again at the JBL Array systems as well the K2 9800, 9900 and Everest. All of the top shelf Synthesis horn system all use second generation Bi Radials which all very clearly have diffraction slots. That said the throats are different than the original Bi-Radials. Their waveguides also have diffraction slots in the Pro boxes as well and similar throats to the horn.
They sound just fine.
Rob🙂
They sound just fine.
Rob🙂
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😎
Now I've seen one. 🙂
I'm betting though that it wasn't *bad* before though. ..Gainphile's demo didn't seem bad to me. 😱
..as a point of reference, I was doing this sort of thing in the late '80s - and usually always had a similar improvement. I didn't have access to open-cell foam though, it was just poly batting integrated into my "grill" cloth cover. I don't think the sound was bad before it, just improved after.. but it's been a rather long time since then so my memory could be faulty. Usually when I had bad sound it was the result of a poor coupling of driver and horn (..visible discontinuity), or the use of titanium drivers with titanium surrounds and solid-state amps. It was slightly over a decade later when I had access to measuring equipment, so I couldn't say what sort of poor objective behavior those horns were contributing at the time.
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This is unfortunate, too bad, a damn shame:
Because:
I find that going to the movies, attending amplified stage performances, often is a horrible experience. The sound is often unpleasant, even PAINFUL to hear, headache inducing, nausea inducing.
I'm thinking the reason is not that the SPL is too high, (though often it is unnecessarily high), because I find really loud sound, if well reproduced, does not sound unpleasant. I do sometimes find, however, that afterwards I have temporary hearing loss - which is disturbing ( but that's another matter) - but not headaches, nausea.
My conclusion, which I think reasonable, is that the sound is loud AND DIRTY. I'm talking about major movies chains and big time theatres - newish venues.
I'm thinking also, that these venues have conventional audio gear such as you mention above - what else would they have? Folk don't get fired for buying what everyone else uses.
"Most popular" does not mean best or even optimal. It might mean mediocre or really dreadful.
Because:
I find that going to the movies, attending amplified stage performances, often is a horrible experience. The sound is often unpleasant, even PAINFUL to hear, headache inducing, nausea inducing.
I'm thinking the reason is not that the SPL is too high, (though often it is unnecessarily high), because I find really loud sound, if well reproduced, does not sound unpleasant. I do sometimes find, however, that afterwards I have temporary hearing loss - which is disturbing ( but that's another matter) - but not headaches, nausea.
My conclusion, which I think reasonable, is that the sound is loud AND DIRTY. I'm talking about major movies chains and big time theatres - newish venues.
I'm thinking also, that these venues have conventional audio gear such as you mention above - what else would they have? Folk don't get fired for buying what everyone else uses.
"Most popular" does not mean best or even optimal. It might mean mediocre or really dreadful.
Frank
I guess that we are just a couple of old farts who have hearing impairments because I hear all the same things. But reading the posts around here and you would think that all is well in the audio world. No need for further investigation everything is just fine.
Maybe we should start our own thread devoted to the myth and fiction of high sound quality - "Why do we need it?"
I guess we don't.
I guess that we are just a couple of old farts who have hearing impairments because I hear all the same things. But reading the posts around here and you would think that all is well in the audio world. No need for further investigation everything is just fine.
Maybe we should start our own thread devoted to the myth and fiction of high sound quality - "Why do we need it?"
I guess we don't.
Hello Earl
It's not so please don't stop. The issue as I see it is the generalization that if it has x it can't be good. The x in this case being any kind of diffraction slot. It's not that simple. What we need is a definitive metric to make comparisons. Generalizations don't work.
Rob🙂
It's not so please don't stop. The issue as I see it is the generalization that if it has x it can't be good. The x in this case being any kind of diffraction slot. It's not that simple. What we need is a definitive metric to make comparisons. Generalizations don't work.
Rob🙂
Actually that was rather the point of the thread, no?
You are the one saying that objective measurements can't be done (because of cost). Therefore you are the one saying that there effectively is no need for further investigation. In fact it's not just "effectively",
-you've actually stated:
"To me there is nothing more to prove."
As far as diffraction and things we are able to measure, I've certainly not jumped to any conclusion. I'm not saying that diffraction is bad categorically; that was you - remember? 😉
A study on diffraction effects with various types of horns/waveguides with respect to objective measurements that we can perform would be interesting. I've certainly heard several occasions where diffraction effects were horrible, and sure enough - they did have horrible measurable decay characteristics as a result.
Investigate away I say! 🙂
Who knows, you might even come to an objective conclusion that others can actually see for themselves.
I think it is important to understand that HOMs can be initiated many ways, for example it could be from diffraction depending on relationship between wave and horn shape, it could also be from driver breakup modes, it could also be any irregularity of wave front characteristics differing from the assumption a horn was designed for. The purpose of measurement is to determine the effect of such terms and try to adjust the design to best reduce diffraction. Since diffraction is unavoidable, if you can allocate such diffraction so that the low frequency diffraction is out of the normal when possible, keep high frequency diffraction as high as possible and at the lip or further out, then additional mechanical reduction can be easier to implement. This is why I feel the LeCleach type expansion is ideal, especially if you use compression drivers. I am confident that if anyone did comparison measurements as I described previously, it would be obvious. What Mr. LeCleach had done also indicates this. Now, if you use a direct radiating driver with a waveguide, you could come out with a different and smaller design. Since it is shallower, you will have less risk of HOMs, and you know the shape of the initial wavefront because that is the shape and velocity of the diaphragm. In order to have a meaningful discussion, you not only need the measurements, but also the simulations to help isolate what is initiated where. it is impossible to get a good feeling of the peeper way to do it unless you get into it, then ask questions along the way, and is why development of something good takes so much time, cost and manpower.
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