This is kind of where I went off track on compression drivers vs dome tweeters, because I am not sure what the phase plug would be on a dome tweeter.
In general, I am in agreement. If it is a compression driver, there is no real phase plug needed, in the traditional sense. It needs the noninterference dong in the middle, like the ring tweeter in the above picture, but since the front to back distance of the diaphragm is so short, there is no path length that needs to be aligned. Then the waveguide is the same as a conventional dome compression driver.
With a dome tweeter, it seems to me that people look at the shape, and feel like it radiates in all directions, when in fact it has the same back and forth motion as a cone, and the same principles of physics, with beaming at higher frequencies. The only advantage is the much smaller radiating origin.
I also wonder if the front to back distance of a dome tweeter will induce phase problems from one point of the driver to another, much as a cone does when it gets out of its comfort zone frequency wise.
Just looking at the posted pictures, the ring radiator has much less diaphragm depth. This has to be an advantage. In addition to the shorter length not having the surface ripples.
I have appreciated the analysis given in many of the posts above. That has been worthwhile. I am NOT a subjectivist.
But for what its worth I saw an interview with one of our local (Australian) upmarket domestic speaker designers and I can recall him saying that he preferred the sound of ring tweeters and think they were Vifa. I value his opinion and a ring tweeter has been on my "to get" list since then.
But for what its worth I saw an interview with one of our local (Australian) upmarket domestic speaker designers and I can recall him saying that he preferred the sound of ring tweeters and think they were Vifa. I value his opinion and a ring tweeter has been on my "to get" list since then.
OEM only as yet, but personally I wouldn't bother about either the BMS or the JBL D2, if you could have this for £499.95:
An externally hosted image should be here but it was not working when we last tested it.
Attachments
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Setting aside, for a moment, the resonant modes of the cone or ring ...
I submit that a ring must have a worse off-axis response than that of a disc (of the same outer radius) ... even though the area of the ring may be less than that of the disc.
1. Imagine two discs ... a small radius r1, and a larger radius r2. The off-axis response of disc r2 will, of course, be worse than disc r1, as frequency increases.
2. But we may consider disc r2 to be comprised of disc r1 plus a ring, with inner radius r1 and outer radius r2
Note that the ring we "added" to disc r1 to create disc r2 has degraded the off-axis response, compared to disc r1
3. Let's now compare disc r2 to ring r2-r1: We "created" the ring by subtracting disc r1 from r2 ... in other words, by subtracting that part from disc r2 with the "better" off-axis response. Therefore, as i see, the off-axis response of disc r2 must degrade, as we subtract disc r1 to create the ring r2-r1.
Does that make sense to anyone else? It's kind late, and i'm all juiced-up on cold medication ...
I submit that a ring must have a worse off-axis response than that of a disc (of the same outer radius) ... even though the area of the ring may be less than that of the disc.
1. Imagine two discs ... a small radius r1, and a larger radius r2. The off-axis response of disc r2 will, of course, be worse than disc r1, as frequency increases.
2. But we may consider disc r2 to be comprised of disc r1 plus a ring, with inner radius r1 and outer radius r2
Note that the ring we "added" to disc r1 to create disc r2 has degraded the off-axis response, compared to disc r1 3. Let's now compare disc r2 to ring r2-r1: We "created" the ring by subtracting disc r1 from r2 ... in other words, by subtracting that part from disc r2 with the "better" off-axis response. Therefore, as i see, the off-axis response of disc r2 must degrade, as we subtract disc r1 to create the ring r2-r1.
Does that make sense to anyone else? It's kind late, and i'm all juiced-up on cold medication ...
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ScanSpeak and Vifa are major names with ring radiator tweeters. I don't have personal experience, but I copied this from home pages Tweeter – Scan-Speak A/S
I fail to see the supremacy of ring radiator...
Ring radiator
The Scan-speak R2904-700009 tweeter is the new flagship tweeter in the Scan-speak line. This tweeter incorporates many innovative design concepts.
The first notable difference is the use of a phase plug. The dome is attached to the phase plug, so the radiating area is now concentrated around the voice coil. This offers more control and reduces distortion and loss that occur at the center of the dome on dome tweeters. The phase plug also acts as a wave guide, reducing high frequency cancellations. A specially designed venting system uses a needle to cut down on turbulence in the air cavity. Better dynamics are achieved by not using ferrofluid, voice coil cooling is performed by the venting system and conduction through copper rings. The new SD-2 neodymium magnet system improves transient response.
Dome tweeter
The Scan-speak D2904-710003 tweeter is a 1" soft dome with wide surround, using the same chambering as the Ring Radiator.
The carefully designed dome and surround result in a linear response and an exceptionally good off axis response. Note the smooth roll off on the low end, making this tweeter a good choice for simple slopes
A specially designed venting system uses a needle to cut down on turbulence in the air cavity. Better dynamics are achieved by not using ferrofluid, voice coil cooling is performed by the venting system and conduction through copper rings. The new SD-2 neodymium magnet system improves transient response.
I fail to see the supremacy of ring radiator...
Ring radiator
The Scan-speak R2904-700009 tweeter is the new flagship tweeter in the Scan-speak line. This tweeter incorporates many innovative design concepts.
The first notable difference is the use of a phase plug. The dome is attached to the phase plug, so the radiating area is now concentrated around the voice coil. This offers more control and reduces distortion and loss that occur at the center of the dome on dome tweeters. The phase plug also acts as a wave guide, reducing high frequency cancellations. A specially designed venting system uses a needle to cut down on turbulence in the air cavity. Better dynamics are achieved by not using ferrofluid, voice coil cooling is performed by the venting system and conduction through copper rings. The new SD-2 neodymium magnet system improves transient response.
Dome tweeter
The Scan-speak D2904-710003 tweeter is a 1" soft dome with wide surround, using the same chambering as the Ring Radiator.
The carefully designed dome and surround result in a linear response and an exceptionally good off axis response. Note the smooth roll off on the low end, making this tweeter a good choice for simple slopes
A specially designed venting system uses a needle to cut down on turbulence in the air cavity. Better dynamics are achieved by not using ferrofluid, voice coil cooling is performed by the venting system and conduction through copper rings. The new SD-2 neodymium magnet system improves transient response.
Here is an explanation from the inventor of both the Vifa XT ring radiators, as well as the ring shaped membrame tweeters (SB Acoustics). It's about the causes of interference in double annulus membrane tweeters :
"A speaker system known comprising a membrane consisting of two dome shaped annulus arranged coaxially. The coil is attached to the connection between the inner and outer annulus and arranged in an air gap in the driver motor. The centre portion of the inner annulus is fastened to an upper portion of the loudspeaker driver motor. As the coil moves up and down in the airgap, sound will emit from the surface of the membrane. The emission direction will be substantially perpendicular to the surface of the membrane, in each point on the membrane. In action the inner annulus will thereby emit sound (waves) towards the center from the portions of the membrane being angled towards the central portion of the membrane. These sound waves will instantly interfere with sound waves deriving from the same membrane part diametrically opposite on the membrane. This interference will cause a certain degree of distortion in the resulting “sound picture”.
A number of suggestions in the art of how to make membranes with improved characteristics are suggested and among these are also a number of ring shaped membranes having two or more dome-shaped annulus arranged concentrically around a central portion, see discussion above. These particular embodiments are designed in order to provide the possibility for higher sound pressure, better distribution meaning more even and more realistic sound distribution utilizing a larger membrane surface area within a smaller space. In a number of these prior art constructions, they have been provided with a sound plug centrally in the membrane in order to fasten the membrane to the chassis centrally. Furthermore, the design of the plug has been carried out in a number of different manners in order to avoid disturbances and/or interference in the response of the membrane and the sound emitted by the membrane. It is however a drawback of these constructions that the plug in the centre takes away part of the effective membrane area and thereby, part of the ability of the loudspeaker construction to emit sound. Membranes using plugs, become less sensible whereby, an altogether relatively larger membrane area is needed in order to reproduce the sound satisfactory. This in turn creates new problems in that larger membranes tends to distort, wobble and/or be prone to internal wave propagation, which are phenomena detrimental to the quality of the sound."
"A speaker system known comprising a membrane consisting of two dome shaped annulus arranged coaxially. The coil is attached to the connection between the inner and outer annulus and arranged in an air gap in the driver motor. The centre portion of the inner annulus is fastened to an upper portion of the loudspeaker driver motor. As the coil moves up and down in the airgap, sound will emit from the surface of the membrane. The emission direction will be substantially perpendicular to the surface of the membrane, in each point on the membrane. In action the inner annulus will thereby emit sound (waves) towards the center from the portions of the membrane being angled towards the central portion of the membrane. These sound waves will instantly interfere with sound waves deriving from the same membrane part diametrically opposite on the membrane. This interference will cause a certain degree of distortion in the resulting “sound picture”.
A number of suggestions in the art of how to make membranes with improved characteristics are suggested and among these are also a number of ring shaped membranes having two or more dome-shaped annulus arranged concentrically around a central portion, see discussion above. These particular embodiments are designed in order to provide the possibility for higher sound pressure, better distribution meaning more even and more realistic sound distribution utilizing a larger membrane surface area within a smaller space. In a number of these prior art constructions, they have been provided with a sound plug centrally in the membrane in order to fasten the membrane to the chassis centrally. Furthermore, the design of the plug has been carried out in a number of different manners in order to avoid disturbances and/or interference in the response of the membrane and the sound emitted by the membrane. It is however a drawback of these constructions that the plug in the centre takes away part of the effective membrane area and thereby, part of the ability of the loudspeaker construction to emit sound. Membranes using plugs, become less sensible whereby, an altogether relatively larger membrane area is needed in order to reproduce the sound satisfactory. This in turn creates new problems in that larger membranes tends to distort, wobble and/or be prone to internal wave propagation, which are phenomena detrimental to the quality of the sound."
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This sentence uses a line, a point and a surface and I don't follow what it means. Do you mean that the average distance from points on the voice coil to points on the surface is less with a ring that a diaphragm driven at its edge? Yes, this is true and the reason why rings work better at HFs.
But the resulting smaller voice col limits their lower frequency capabilities.
Surface ripple? Do you mean breakup? A ring does not eliminate cone breakup. It will tend to move it higher in frequency, but not eliminate it.
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