The Advantages of a Ring Radiator vs. Conventional Domes? (Concave/Convex)

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Hey guys,

I've been interested in trying out some ring radiators lately (Due to the fact that they are a variation on the conventional dome design and are said to offer some advantages when compared to them), however, I've been having a hard time trying to find out what the advantages of them are when placed against the more traditional concave/convex type of designs.

Other than the fact that they've have got an integrated phase plug (which, for whatever reason, seems to have worse off-axis response than your usual dome...) I haven't been able to find out their advantages.

If you guys could help me figure this out, it would be greatly appreciated

Much love/Many thanks in advance for your guys' help.
 
Hey guys,

I've been interested in trying out some ring radiators lately (Due to the fact that they are a variation on the conventional dome design and are said to offer some advantages when compared to them), however, I've been having a hard time trying to find out what the advantages of them are when placed against the more traditional concave/convex type of designs.

Other than the fact that they've have got an integrated phase plug (which, for whatever reason, seems to have worse off-axis response than your usual dome...) I haven't been able to find out their advantages.
The ring allows a large voice coil with a diaphragm that can use less area than a dome shape diaphragm of the same diameter. Less area =less mass, less mass is better for HF response and transients.
Though the JBL 075/2402 "bullet" has narrowing HF response, there are ring radiator tweeters using various horns that have excellent dispersion.
 
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Besides the "integrated" phase plug , their main advantage vs. (any type) dome tweeters is the lack of the bell resonance mode (dome breakup) which is present on ALL dome types regardless of material and shape used. With standard 3/4 and 1" tweeters it is happening somewhere between 22 and 40 kHz with a magnitude of 3-12 dB (the harder the dome material, the higher the resonance peak is) so basically it is inaudible, but its subharmonics and the related distortions are definitely yes.
Ring radiators are almost completely free of that kind of problem, and while they are not perfect either, their uppermost range is definitely cleaner and more extended than most dome tweeter's. Nice example is the SB29RDC from SB acoustics (or the XT series from Vifa, Scan Speak also has a range of them)
Below are two examples, the first one is a high-end dome, the other is the excellent Satori tweeter of SB.
 

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Less area =less mass, less mass is better for HF response and transients.
Agree on HF response, but less mass does not necessarily mean better transients. Transient response is primarily determined by whether there are resonances within the pass band and how they are damped.

A disadvantage of ring radiators is that they start to beam at a lower frequency than hard convex domes.
 
The center of the soft dome tweeter moves in antiphase relative to the rest of the dome, somewhere in the 12 to 15 kHz range for a 1" dome, and 15 to 20 kHz for a 3/4 inch dome.

The Vifa XT19, a 3/4" ring radiator, has a high frequency dispersion similar to a one inch dome tweeter.
 
A disadvantage of ring radiators is that they start to beam at a lower frequency than hard convex domes.
An advantage of a compression driver (whether the diaphragm is a ring or a dome)is a horn or waveguide of the desired pattern can be used.

Another example of a ring radiator that does not beam is a JBL 2402, it has a 100 degree uniform pattern out to 20 kHz.
 

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I don't classify the SB29 as a ring radiator (may be misconception on my part)

But the fixed dome 'cap' eliminates the antiphase breakup - I see this as a far more pronounced problem in soft domes.

The Vifa rings seem like completely different animals (to me) they don't seem like a dome with a fixed centre (maybe they are, haven't held.one in my hand...)
 
Thanks for the responses everyone
(Based on what I've read - the advantages are less mass, and as such, extended HF response. The downside is that, perhaps counter-intuitively (at least to myself) they'll begin to beam earlier/have worse off axis response)

As an abstract question, do you guys think we'll ever see a ring radiator midrange (2-3" type of deal - kind of like 2-3" dome midranges)
If so, why/why not?

Thanks for the thoughts everyone.
 
3 Reasons

Hey guys,

I've been interested in trying out some ring radiators lately (Due to the fact that they are a variation on the conventional dome design and are said to offer some advantages when compared to them), however, I've been having a hard time trying to find out what the advantages of them are when placed against the more traditional concave/convex type of designs.

Other than the fact that they've have got an integrated phase plug (which, for whatever reason, seems to have worse off-axis response than your usual dome...) I haven't been able to find out their advantages.

If you guys could help me figure this out, it would be greatly appreciated

Much love/Many thanks in advance for your guys' help.

Firstly, the ring radiator does not exhibit the break up modes of a dome diaphragm of otherwise comparable performance.

Note, however; that the [Sd] of a ring radiator will always be smaller than that of a dome radiator of the same moving mass when that of the suspension, voice coil and former are included.

Secondly, a ring diaphragm has two compliances controlling its movement instead of just one for the dome design. This feature suppresses the occurrence of diaphragm rocking modes at lower frequencies inherent in single suspension moving systems.

The challenge here is getting a balanced elasticity between the two compliance rings as the outer ring is necessarily larger than the inner ring.

The third advantage is that ring geometry permits two such rings to occupy the same compression chamber where they may be operated in opposition to each other using separate voice coils.

This feature has been successfully exploited in JBL D2 Compression Driver designed by Alex Voishvillo.

The issue here, is getting air tight seals between the many rings that are joined to form the driver compression chamber and phase plug. If an air seal fails here, driver output is all but lost.

WHG
 
To be clear here, I see no reason why the directivity of a ring diaphragm would have to be any different than that of a dome. Its all in how the phase plug and the waveguide are designed.

The ring - supported at both its inner and outer edges is far more rigid structurally than a dome. But it also has less radiating area for a given outside radius, and since it has two compliances, it will have a higher fundamental resonance than the dome. If one is seeking a good LF response from the driver then a dome is likely to have the advantage. If one wants to extend the HF response then the ring will have an advantage. I prefer a single driver for the upper range and the rings just can't get down low enough to cover the range I seek. If you can live with the higher crossover point then the rings work fine.
 
Hey guys,

I've been interested in trying out some ring radiators lately (Due to the fact that they are a variation on the conventional dome design and are said to offer some advantages when compared to them), however, I've been having a hard time trying to find out what the advantages of them are when placed against the more traditional concave/convex type of designs.

Other than the fact that they've have got an integrated phase plug (which, for whatever reason, seems to have worse off-axis response than your usual dome...) I haven't been able to find out their advantages.

If you guys could help me figure this out, it would be greatly appreciated

Much love/Many thanks in advance for your guys' help.

Just to be clear, as I am confused a bit by some of the answers, are you comparing the ring radiator (compression driver) to a conventional dome compression driver, or to a dome tweeter?
 
Yes there might be a little confusion here, I think the thread starter was thinking about these types, (see pics.) not the ring radiator type compression tweeters.
BTW.: The SB29RDC has No integrated phase plug, it is almost ruler flat from 1k to 20kHz, runs up to 40k, and its off axis performance is pretty good, even compared to some big-name tweeters.
 

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Ring radiator, closed back or open back ?

Hi there: looking at a Vifa XT 25 ring radiator tweeter now. I can not tell if it is a closed back device or open back requiring an enclosure design. The magnet is exposed and is observed to be situated in a plastic tube. If it is closed back, then the driver can be inserted through the face board and occupy space in the same enclosure with the woofer.
Any help would be appreciated. ...regards, Michael
 
It may be worthwhile to examine and compare the Peerless XT25 (ring) and DX25 (dome). In particular, the extended low frequency versions, the XT25BG and DX25BG respectively.

I say worthwhile because AFAIK (which is very little) the motors and faceplates/waveguides are nearly identical. It's the easiest pair of models I know of where you can make a comparison with the fewest variables.

Best,


E
 
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N.B.

Hey guys,

I've been interested in trying out some ring radiators lately (Due to the fact that they are a variation on the conventional dome design and are said to offer some advantages when compared to them), however, I've been having a hard time trying to find out what the advantages of them are when placed against the more traditional concave/convex type of designs.

Other than the fact that they've have got an integrated phase plug (which, for whatever reason, seems to have worse off-axis response than your usual dome...) I haven't been able to find out their advantages.

If you guys could help me figure this out, it would be greatly appreciated

Much love/Many thanks in advance for your guys' help.

Design Advantages Include:
1) The ring with its two compliances is less prone to LF rocking motions, can support a larger xmax, and the two compliances need not be collectively as stiff as just one.
2) Due to the inherently shorter span, transverse beak-up modes start at a much higher frequency.
3) The ring configuration lends itself to the use of dual opposing diaphragms which yields a mechanically stable system where vibrations are not transmitted to the attached baffle/horn assembly.

The design challenges that remain include:
5) Getting inner and outer compliances to measure equal.
6) Getting a coherent and dispersive wave-front at the horn exit that is essentially frequency independent within the units pass-band.
7) For present designs, that do not realize their full performance potential, a three-way system topography is required to incorporate them, with all the attendant problems associated with having to deal with a second frequency overlap region.

The most notable Large Format Driver of this design are the BMS 4599nd
Overview

and the JBL D2
D2 Dual Diaphragm Dual Voice Coil Compression Driver

Regards,
WHG
 
Hi there: Thanks to all for information on ring radiators, I have a pair of Vifa XT 25 sc90-04, which will be used with a my pair of Seas ER 18rn-TRD (7-inch extended range, low vas, with Fs=30hz, mounted in a TL or MLTL). Haven't decided if the mass loaded type... will it just cause the TL sound to be similar to a BR. Planed Xover to be around 5 to 6K. The Seas has fine mid range sound, although ragged at the intended xover. thanks again...regards, Michael
 
Mount the Vifa XT 25 sc90-04 to a waveguide and you'll have no issues with a XO somewhere between 2000-3000Hz. The SEAS will thank you for that ;)

This guy has put a pair of XT25 tg35-04's behind a parts express 12" waveguide with a crossover at 800 !!! Hz.
C-C spacing looks quite terrible though.
 
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Design Advantages Include:
1) The ring with its two compliances is less prone to LF rocking motions, can support a larger xmax, and the two compliances need not be collectively as stiff as just one.
2) Due to the inherently shorter span, transverse beak-up modes start at a much higher frequency.
3) The ring configuration lends itself to the use of dual opposing diaphragms which yields a mechanically stable system where vibrations are not transmitted to the attached baffle/horn assembly.

The design challenges that remain include:
5) Getting inner and outer compliances to measure equal.
6) Getting a coherent and dispersive wave-front at the horn exit that is essentially frequency independent within the units pass-band.
7) For present designs, that do not realize their full performance potential, a three-way system topography is required to incorporate them, with all the attendant problems associated with having to deal with a second frequency overlap region.

The most notable Large Format Driver of this design are the BMS 4599nd
Overview

and the JBL D2
D2 Dual Diaphragm Dual Voice Coil Compression Driver

Regards,
WHG

Seems like a fresh approach for maximum output - if one needs that. The earlier BMS ring CDs didn't work so well, but these newer dual ones do - at least for maximum output. I wouldn't use that BMS above about 2 kHz, but below that down to about 200 Hz it seems to work very well.

The JBL doesn't show any data.

But these drivers aren't really necessary for home use. Kind of overkill.
 
The ring - supported at both its inner and outer edges is far more rigid structurally than a dome. But it also has less radiating area for a given outside radius, and since it has two compliances, it will have a higher fundamental resonance than the dome. If one is seeking a good LF response from the driver then a dome is likely to have the advantage. If one wants to extend the HF response then the ring will have an advantage. I prefer a single driver for the upper range and the rings just can't get down low enough to cover the range I seek. If you can live with the higher crossover point then the rings work fine.

The ring will have less radiating area for outside radius, but more area per VC radius. This gives more surface movement from less VC weight.

To your first sentence, the VC has less distance, at any one point, of surface to control. This goes to elimination the fore mentioned points out of phase on the surface, from surface ripple.
 
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