I see no reason that frequency makes a difference. The important part is that the directivity not change radicaly with frequency, no matter where the crossover is. That requires that the directivity matches.
Louder than??? What other setup you comparing it to?
Far as I know, Geddes confines sound to a 90deg cone.
Are we comparing to a 180 degree cone? (IE: driver in
a flat wall)???
A meaningful question might be: With otherwise identical
Geddes waveguides, how many dB lost to the foam plug?
Respectful that the plug does something useful in return
for said losses, are they significant?
Far as I know, Geddes confines sound to a 90deg cone.
Are we comparing to a 180 degree cone? (IE: driver in
a flat wall)???
A meaningful question might be: With otherwise identical
Geddes waveguides, how many dB lost to the foam plug?
Respectful that the plug does something useful in return
for said losses, are they significant?
In free air with no walls or floor or ceiling, it probably doesn't matter.
Since I don't know of any such listening room except maybe anechoic
chamber... Even outdoors, you have the ground (and possibly other
array'd loudspeakers creating virtual reflections, same as walls).
My point being that such unavoidable reflections from outside the
intended listening cone might become more obvious to the listener
if the excess dispersions are grossly different over frequency.
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I think he meant to ask how much gain it provides to the compression drivers nominal sensitivity. For instance, this DDS horn is listed with a nominal gain of 5,9 db.
The link only takes me to USSpeaker homepage, no specific product.
You refer perhaps to "DDS CFD ENG 1-90 PRO"???
I see a directivity factor of 9.3, and an absurd 112.31dB SPL claim
with no specified driver... Where you seeing +5.9dB? We lookin at
different waveguides, or additional spec from another source?
A 90deg corner waveguide would give a theoretical +6dB over
driving a simple halfspace. I think a round cone would not fully
illuminate the axis corners of a full quadrant. The "gain" by this
exclusion should be higher, but reality always losses something.
You refer perhaps to "DDS CFD ENG 1-90 PRO"???
I see a directivity factor of 9.3, and an absurd 112.31dB SPL claim
with no specified driver... Where you seeing +5.9dB? We lookin at
different waveguides, or additional spec from another source?
A 90deg corner waveguide would give a theoretical +6dB over
driving a simple halfspace. I think a round cone would not fully
illuminate the axis corners of a full quadrant. The "gain" by this
exclusion should be higher, but reality always losses something.
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The question is ill posed as I am not sure what is being asked. For all practical purposes the "gain" depends only on the compression ration of the diaphragm to the throat and the nature of the waveguide makes very little difference. Thus this gain is fixed by the driver. When a drivers sensitivity is given its usually on some sort of a horn and for the most part at the lower frequencies this will be the same for any horn or waveguide. There will be a difference at the upper side of the passband due to directivity effects. For example my waveguides are true CD all the way across the passband and so they tend to drop in axial SPL when compared to a normal Horn which is not CD at this upper edge. The foam has a loss of about 2 dB at 10 kHz dropping to nothing measureable at 1 kHz. This is about all I can say about "gain", and would suggest, instead that "sensitivity" be used instead as it has a more well defined meaning.
OK, thanks . Lets make yousome more, "big" idea was to use waveguide to "transform" some 90dB dome (or ring) hifi tweeters into 95-96dB region...
Of course - this is what a compression driver is! It is conceiveable to just place a waveguide over a dome, but unless its a flat piston there will be interference effects and in the end a phase plug will be required to extend the HF. Then you have a compression driver, except that the compression driver usualy has a larger diaphragm than the throat and hence more output and better thermal capability.
I've built a few horns and waveguides that use the foam treatment that Geddes has invented, and I noticed that it changes the apparent location and size of the horn or waveguide.
I have a theory on why this is, and was curious if anyone else has noticed as well.
Here's a pic to illustrate the theory.
Basically, in a conventional horn, the sound appears to emanate from the mouth of the horn. It's also very "big." The dimensions of the sound source appear to be the size of the horn mouth.
In a foam lined horn or waveguide, the sound appears to emanate from somewhere a few inches back from the mouth, and the apparent size is much smaller. The difference is particularly noticeable in the Summa, where the mouth has been treated to reduce diffraction, and the depth of the foam plug is over a foot long.
Here's my hypothesis. Firs we know about the Haas Effect. "When two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first. To the listener, this creates the impression that the sound comes from that location alone due to a phenomenon that might be described as "involuntary sensory inhibition" in that one's perception of later arrivals is suppressed."
In a horn, the reflections generated inside the horn can exceed the energy generated by the device itself. You can see this in a frequency response plot, where the amplitude of the device will increase by as much as 10db.
In a nutshell, by "soaking up" reflections with the foam, and diffusing reflections at the mouth with a roundover, the Summa "shrinks" the apparent size of the sound, and "pushes" back the soundstage.
Hopefully the picture helps. The photo at the right are my Summas - you can see the roundover and the foam in the profile. The photo at the left is a set of Geddes speakers being built, and you can see the dimensions of the waveguide. In the illustration, you can see that reflected energy is attenuated by going through the foam. At the mouth reflections are further diffused by the roundover. One analogy that I like to use is the idea of looking at a cars headlights in the fog. The fog makes it impossible to perceive the depth of the headlights, and their size is distorted. But if you remove the fog, you can perceive the depth and distance of the headlights. The inventions that Geddes has provided remove the fog.
I believe this may help to explain why listeners have reported that the Summas don't "sound" as big as they look. A lot of horns have a very "large" presentation. If you didn't see the Summas before your eyes, and you only listened to them, you would think they were a much smaller speaker. They image like a mini-monitor.
I have a theory on why this is, and was curious if anyone else has noticed as well.
Basically, in a conventional horn, the sound appears to emanate from the mouth of the horn. It's also very "big." The dimensions of the sound source appear to be the size of the horn mouth.
In a foam lined horn or waveguide, the sound appears to emanate from somewhere a few inches back from the mouth, and the apparent size is much smaller. The difference is particularly noticeable in the Summa, where the mouth has been treated to reduce diffraction, and the depth of the foam plug is over a foot long.
Here's my hypothesis. Firs we know about the Haas Effect. "When two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first. To the listener, this creates the impression that the sound comes from that location alone due to a phenomenon that might be described as "involuntary sensory inhibition" in that one's perception of later arrivals is suppressed."
In a horn, the reflections generated inside the horn can exceed the energy generated by the device itself. You can see this in a frequency response plot, where the amplitude of the device will increase by as much as 10db.
In a nutshell, by "soaking up" reflections with the foam, and diffusing reflections at the mouth with a roundover, the Summa "shrinks" the apparent size of the sound, and "pushes" back the soundstage.
Hopefully the picture helps. The photo at the right are my Summas - you can see the roundover and the foam in the profile. The photo at the left is a set of Geddes speakers being built, and you can see the dimensions of the waveguide. In the illustration, you can see that reflected energy is attenuated by going through the foam. At the mouth reflections are further diffused by the roundover. One analogy that I like to use is the idea of looking at a cars headlights in the fog. The fog makes it impossible to perceive the depth of the headlights, and their size is distorted. But if you remove the fog, you can perceive the depth and distance of the headlights. The inventions that Geddes has provided remove the fog.
I believe this may help to explain why listeners have reported that the Summas don't "sound" as big as they look. A lot of horns have a very "large" presentation. If you didn't see the Summas before your eyes, and you only listened to them, you would think they were a much smaller speaker. They image like a mini-monitor.
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Hey John
I would tend to agree with your comments as being quite plausible and pretty much what I believe as well. But its just a guess. I do know this. When people hear the Summas at my home, where they are hidden, they invariably comment on how "big" they actually are when they see them. Clearly the impression IS of a much smaller speaker.
I would tend to agree with your comments as being quite plausible and pretty much what I believe as well. But its just a guess. I do know this. When people hear the Summas at my home, where they are hidden, they invariably comment on how "big" they actually are when they see them. Clearly the impression IS of a much smaller speaker.
I think rather than how big or small a loudspeaker sounds, it is more important to reproduce the size of the recorded image.
Years ago I went into a store that had a pair of $100K speakers. The saleman played a recording of a single guitar soloist/vocalist. He seemed to think they were the cat's meow. I said I thought it made the person sound as big as the wall in the room and walked out. They may have been impressive for a full orchestra, but not soloists.
Years ago I went into a store that had a pair of $100K speakers. The saleman played a recording of a single guitar soloist/vocalist. He seemed to think they were the cat's meow. I said I thought it made the person sound as big as the wall in the room and walked out. They may have been impressive for a full orchestra, but not soloists.
