I first saw this type of driver in the Advent 6003 that debuted back in 1982 (this was Advent's first 3-way model - man, what a controversy among Advent fans when it debuted!).
Here is a description w/photos
What motivated my question concerning 34 year old technology is that during the last few years I've seen some tweeters with similar construction (though the "surround" portion was not nearly as large). Here's one.
BTW: when (gently) pushing on the radiating surface of the midrange back then, I was quite surprised that it felt much stiffer than a conventional soft-dome midrange & actually was closer to a typical cone's stiffness.
Here is a description w/photos
What motivated my question concerning 34 year old technology is that during the last few years I've seen some tweeters with similar construction (though the "surround" portion was not nearly as large). Here's one.
BTW: when (gently) pushing on the radiating surface of the midrange back then, I was quite surprised that it felt much stiffer than a conventional soft-dome midrange & actually was closer to a typical cone's stiffness.
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The Community M200 is constructed similar to the Advent midrange, as it the midrange in the Avantgarde Trio.
http://www.communitypro.com/sites/default/files/M200A.pdf
An externally hosted image should be here but it was not working when we last tested it.
http://www.communitypro.com/sites/default/files/M200A.pdf
So, going by the quantity of responses, either there are no advantages for this driver (vs. a conventional dome or cone type driver) or there just isn't enough data with which to form a solid opinion? Advent used that design up to the mid 90s so I'll assume it performed adequately......or maybe they continued to use it mainly for marketing reasons because its design was derived from the tweeter Henry Kloss used in his classic 2-way systems in the 70s a.k.a. the "fried egg" tweeter.
Not the 1st to do so. Older Advents (the fried egg tweeter), Wharfdales (a lovely clear purple), the famous CTS tweeter all had similar drivers at some point.
dave
I appreciate the info Dave. Though I'm sure it's because of the march of technology i.e. substandard designs were weeded out, until around the early 90s(?) it seemed there were many different driver technologies out there besides cones & domes. While I don't want to stick with "old tech" simply for the sake of nostalgia, I am still interested in why particular driver technologies were offered for sale & then abandoned.
I don't think that the tech has disappeared, it has just evolved. The small FRs we use as tweeters can be considered HF radiating dustcap with a huge surround that lets them get down to where many of the issues with XOs can be disappeared.
dave
dave
Advent 6.5i FR
Hi there: I have a pair of Advent 6.5i drivers labled "lCT loudspeaker, Made in USA" (although the literature said they were made from English patents)...purchased about 1980. The coated paper cone is smallish 3-1/2" in a 6-1/2" frame, an inverted top hat plastic whizzer is attached to the cone, a funnel shaped plastic thingy is stationary in the center and not connected to the cone or whizzer ( a 3mm hole is center of the conical shape ) (ICT technology ?). Large ferrite magnet, foam surround, 4 ohms impedance. I believe the power was rated at 75 watts each although the label says 125 watts. Any clues about these, seems to fit into the discussion of 1970's audio. ...regards, Michael
Hi there: I have a pair of Advent 6.5i drivers labled "lCT loudspeaker, Made in USA" (although the literature said they were made from English patents)...purchased about 1980. The coated paper cone is smallish 3-1/2" in a 6-1/2" frame, an inverted top hat plastic whizzer is attached to the cone, a funnel shaped plastic thingy is stationary in the center and not connected to the cone or whizzer ( a 3mm hole is center of the conical shape ) (ICT technology ?). Large ferrite magnet, foam surround, 4 ohms impedance. I believe the power was rated at 75 watts each although the label says 125 watts. Any clues about these, seems to fit into the discussion of 1970's audio. ...regards, Michael
Hate to 'necropost' (& with a long post at that) - but I came across this thread whilst researching the technology behind the mid-range drivers in my speakers (I have a pair of Diatone DS-77Z speakers with hybrid cone/dome squawkers: the 'dust cap' is omega-phase surface hardened titanium, whilst the cone is a honeycombed weave of PAN & aramid fibres, terminated in a surround of two tangentially offset fibre reinforced polymers). What I found out about cone/dome hybrid mid-range drivers might be of interest to the OP.
Some background, though. I became curious about the design considerations behind cone/dome hybrid mid-range drivers for two reasons.
Firstly, the mid-range drivers in the Diatone DS-77Z speakers sound great! When I bought them I got a chance to listen to them side-by-side with a pair of Yamaha NS-1000M speakers out of the same playback chain, & the mid-range from the Diatones sounded as good as, if not better than, the Yammies (at matched volume levels).
Secondly, if cone/dome hybrid squawkers can sound so good, why don't you see this type of mid-range driver being used more often?
So this what I found out about hybrid cone-dome squawkers.
Ethan Winer has this to say in 'The Audio Expert': "In some speakers, a rigid aluminium dome in the center of the cone improves the response at frequencies toward the upper end of the driver's range. The metal cap is attached directly to the voice coil, so it can vibrate more or less independently of the main cone. Being metal and dome shaped, it's also less likely to deform than a paper dust cap as it vibrates. A metal cap therefore serves as a secondary radiator. But unlike a whizzer cone, it's better damped by virtue of being bonded securely all around its outer edge. The metal cap is often damped with thin open-cell foam attached to the back side to further reduce resonance. It can also serve as a heat sink, conducting heat away from the voice coil to the surrounding air better than a paper dust cap. When a voice coil heats up, its resistance increases. This causes the driver to draw less current for a given applied voltage, which reduces efficiency & in turn lowers the output SPL. This effect is known as 'thermal compression'. So in this case, a metal center cap does more than simply keep dust out of the tiny gap around [the] voice coil."
Winer's point about a domed dust cap 'smoothing out' 'peaks' in the frequency response at the upper end of a cone driver's passband is graphically illustrated on printed pages 9-10 of Vance Dickason's 'Loudspeaker Design Cookbook' (7th ed.)
Martin Colloms refers to these 'peaks' in the 4th ed. of his 'High Performance Loudspeakers' (on printed pages 182-183, mainly) in a discussion of the relative merits of mid-range cones vs. domes, & elsewhere in-text.
For example, on printed page 179, Colloms writes: "The dust cap may influence the performance of LF units, though its effects are usually more noticeable at mid frequencies". He also states (on printed page 182) that "... dome units give their best results in the upper mid range and cone units in the lower range". A hybrid cone-dome squawker with a physical crossover between the two radiating elements (implemented by means of attachment of the dome to the voice coil or coil former & attachment to the cone) could have been a way for a high performance speaker maker (like Diatone) to harness the 'best of both worlds' whilst avoiding many of the pitfalls of domes vs. cones that Colloms refers to in his discussion of mid-range drivers on printed pages 181-189.
In Adrianus Kaizer's doctoral dissertation 'On the Design of Broadband Electrodynamical Loudspeakers & Multiway Loudspeaker Systems' (1986, available here), the author uses modelling techniques based on the Wigner distribution to show (on printed pages 49-55) that mounting a (dome-shaped) vibrating dust cap in the centre of a cone-shaped radiator 'smoothes out' the on-axis SPL of the driver towards the top of its working range, & reduces the spreading of its transient response in the time domain (so that the transient response of a cone with a large vibrating dust cap mounted at its centre approaches the transient response of a rigid dome-only driver). Kaizer's work seems to bear out the idea that, with the right design, combining a cone-shaped radiator with a (secondary) dome-shaped radiator (mounted as a rigid dust cap in the centre of the cone) might give mid-range driver performance which is the 'best of both worlds' (& at a lesser cost than rigid mid-range dome drivers, which typically require large & expensive magnet structures to achieve optimal performance).
In a nutshell, cone/dome hybrid mid-range drivers seem to be about extracting a mid-range dome like level of performance from what is essentially a cone with a larger-than-normal dust cap functioning as a secondary radiator, at a lower cost (than the cost of manufacturing a mid-range dome driver with comparable performance characteristics).
Some background, though. I became curious about the design considerations behind cone/dome hybrid mid-range drivers for two reasons.
Firstly, the mid-range drivers in the Diatone DS-77Z speakers sound great! When I bought them I got a chance to listen to them side-by-side with a pair of Yamaha NS-1000M speakers out of the same playback chain, & the mid-range from the Diatones sounded as good as, if not better than, the Yammies (at matched volume levels).
Secondly, if cone/dome hybrid squawkers can sound so good, why don't you see this type of mid-range driver being used more often?
So this what I found out about hybrid cone-dome squawkers.
Ethan Winer has this to say in 'The Audio Expert': "In some speakers, a rigid aluminium dome in the center of the cone improves the response at frequencies toward the upper end of the driver's range. The metal cap is attached directly to the voice coil, so it can vibrate more or less independently of the main cone. Being metal and dome shaped, it's also less likely to deform than a paper dust cap as it vibrates. A metal cap therefore serves as a secondary radiator. But unlike a whizzer cone, it's better damped by virtue of being bonded securely all around its outer edge. The metal cap is often damped with thin open-cell foam attached to the back side to further reduce resonance. It can also serve as a heat sink, conducting heat away from the voice coil to the surrounding air better than a paper dust cap. When a voice coil heats up, its resistance increases. This causes the driver to draw less current for a given applied voltage, which reduces efficiency & in turn lowers the output SPL. This effect is known as 'thermal compression'. So in this case, a metal center cap does more than simply keep dust out of the tiny gap around [the] voice coil."
Winer's point about a domed dust cap 'smoothing out' 'peaks' in the frequency response at the upper end of a cone driver's passband is graphically illustrated on printed pages 9-10 of Vance Dickason's 'Loudspeaker Design Cookbook' (7th ed.)
Martin Colloms refers to these 'peaks' in the 4th ed. of his 'High Performance Loudspeakers' (on printed pages 182-183, mainly) in a discussion of the relative merits of mid-range cones vs. domes, & elsewhere in-text.
For example, on printed page 179, Colloms writes: "The dust cap may influence the performance of LF units, though its effects are usually more noticeable at mid frequencies". He also states (on printed page 182) that "... dome units give their best results in the upper mid range and cone units in the lower range". A hybrid cone-dome squawker with a physical crossover between the two radiating elements (implemented by means of attachment of the dome to the voice coil or coil former & attachment to the cone) could have been a way for a high performance speaker maker (like Diatone) to harness the 'best of both worlds' whilst avoiding many of the pitfalls of domes vs. cones that Colloms refers to in his discussion of mid-range drivers on printed pages 181-189.
In Adrianus Kaizer's doctoral dissertation 'On the Design of Broadband Electrodynamical Loudspeakers & Multiway Loudspeaker Systems' (1986, available here), the author uses modelling techniques based on the Wigner distribution to show (on printed pages 49-55) that mounting a (dome-shaped) vibrating dust cap in the centre of a cone-shaped radiator 'smoothes out' the on-axis SPL of the driver towards the top of its working range, & reduces the spreading of its transient response in the time domain (so that the transient response of a cone with a large vibrating dust cap mounted at its centre approaches the transient response of a rigid dome-only driver). Kaizer's work seems to bear out the idea that, with the right design, combining a cone-shaped radiator with a (secondary) dome-shaped radiator (mounted as a rigid dust cap in the centre of the cone) might give mid-range driver performance which is the 'best of both worlds' (& at a lesser cost than rigid mid-range dome drivers, which typically require large & expensive magnet structures to achieve optimal performance).
In a nutshell, cone/dome hybrid mid-range drivers seem to be about extracting a mid-range dome like level of performance from what is essentially a cone with a larger-than-normal dust cap functioning as a secondary radiator, at a lower cost (than the cost of manufacturing a mid-range dome driver with comparable performance characteristics).
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