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Joined 2009
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Kindhornman,
Yes, we probably are talking past each other and yes, the larger cone will always breakup first given equal design and construction considerations as you said. That however, is rarely the case and besides, both 12" and 15" drivers are well passed their true pistonic region which in this case is an octave bellow their crossover points (these being at around 800-1000Hz in this case I believe).
Theory says that a 12" will have its -6db at 45degrees off axis (90deg beamwidth), at just over 1300Hz and for the 15" this will happen at just over 1100Hz. This pretty much holds true with most drivers for which directivity plots are published.
Maybe what you say, holds true for when one driver is operating in its pistonic regime and the other is in breakup. Like I said before though, this would have to be observed way lower in frequency where directivity is of less importance in as much as we're talking about matching directivities of woofer and waveguide at and around the crossover.
I am sure that you are quoting flat rigid piston data here. Real drivers are not flat and real directivities differ considerably from the flat piston theory.
Interesting. My FOB means "Freight on Board" which is how it is used in inland shipping of a car. It designates where the fright costs are calculated from. For example "FOB Los Angeles" would mean that the freight costs are "on board" the cars cost up to Los Angeles. After that the buyer has to pay for the shipping. I should just not use the term FOB if it causes confusion internationally.
One problem of using abbreviations is what we are seeing here, different uses in different countries of the same abbreviation. As Earl has suggested this is what I have always understood it to mean here in the USA, the cost of the item from the shipping origin, not the final cost at the destination which will include the transit cost to the final location. These costs are usually finalized by the particular shipping company and their given shipping rates.
FOB has always included any pallets or boxes needed to ship and final shipping weight. The only missing component has always been the delivery charge for transportation which is generally unknown until the order is placed with the delivery location.
Not sure how any of this got into the subject of waveguides?
Not sure how any of this got into the subject of waveguides?
Free On Board
FOB means the vendor will load the product(s) ordered onto the carrier's vehicle at no extra charge, nothing more. In this setting, the carrier is acting as your agent, and is responsible to you, the buyer (not the seller), for any damage that may occur during transit.
Regards,
WHG
FOB means the vendor will load the product(s) ordered onto the carrier's vehicle at no extra charge, nothing more. In this setting, the carrier is acting as your agent, and is responsible to you, the buyer (not the seller), for any damage that may occur during transit.
Regards,
WHG
Compression Driver Potpourri
The principal barriers to achieving superior compression driver performance are the availability and cost of two key materials. They are:
1) Beryllium
With its superior stiffness to weight ratio, unsurpassed acoustic properties, and enhanced thermal conductivity, make it the ideal material for driver diaphragms.
And
2) Cobalt
The principal alloying element in Premundur, the high permeability steel alloy used to make high performance magnetic circuits.
Until the cost of these materials is lowered, only marginal improvements in driver price/performance points may be expected.
The derivative works of Bart Locanthi represent improvements to the original Western Electric Designs.
Today, WE units are still being used. See references [1] & [2]
While working at JBL and then later at TAD/Pioneer, Bart implemented the work of Smith on phase plug design [3] and Introduced the use of a beryllium diaphragm in the TAD product line. Nobody ripped-off JBL, who by the way, sold-out to HK.
The origins of the WE designs (circa 1920’s) may be traced back to the works of C.R. Hanna and J. Slepian [4], followed by those of E.C. Wente and A.L Thuras [5].
Regards
WHG
References
[1] & [2] See Attached Files
[3] Smith, B. (March 1953). "An Investigation of the Air Chamber of Horn Type Loudspeakers". The Journal of the Acoustical Society of America 25 (2): 305–312. doi:10.1121/1.1907038.
[4] Hanna, C. R.; Slepian, J. (September 1977 (originally published 1924)). "The Function and Design of Horns for Loudspeakers (Reprint)". The Journal of the Audio Engineering Society 25: 573–585.
[5] Wente, E.; Thuras, A. (March 1978 (originally published 1928)). "A High-Efficiency Receiver for a Horn-Type Loudspeaker of Large Power Capacity (reprint)". The Journal of the Audio Engineering Society 26: 139–144.
The principal barriers to achieving superior compression driver performance are the availability and cost of two key materials. They are:
1) Beryllium
With its superior stiffness to weight ratio, unsurpassed acoustic properties, and enhanced thermal conductivity, make it the ideal material for driver diaphragms.
And
2) Cobalt
The principal alloying element in Premundur, the high permeability steel alloy used to make high performance magnetic circuits.
Until the cost of these materials is lowered, only marginal improvements in driver price/performance points may be expected.
The derivative works of Bart Locanthi represent improvements to the original Western Electric Designs.
Today, WE units are still being used. See references [1] & [2]
While working at JBL and then later at TAD/Pioneer, Bart implemented the work of Smith on phase plug design [3] and Introduced the use of a beryllium diaphragm in the TAD product line. Nobody ripped-off JBL, who by the way, sold-out to HK.
The origins of the WE designs (circa 1920’s) may be traced back to the works of C.R. Hanna and J. Slepian [4], followed by those of E.C. Wente and A.L Thuras [5].
Regards
WHG
References
[1] & [2] See Attached Files
[3] Smith, B. (March 1953). "An Investigation of the Air Chamber of Horn Type Loudspeakers". The Journal of the Acoustical Society of America 25 (2): 305–312. doi:10.1121/1.1907038.
[4] Hanna, C. R.; Slepian, J. (September 1977 (originally published 1924)). "The Function and Design of Horns for Loudspeakers (Reprint)". The Journal of the Audio Engineering Society 25: 573–585.
[5] Wente, E.; Thuras, A. (March 1978 (originally published 1928)). "A High-Efficiency Receiver for a Horn-Type Loudspeaker of Large Power Capacity (reprint)". The Journal of the Audio Engineering Society 26: 139–144.
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whgeiger,
I can tell you that the price for just a !" dome tweeter diaphragm made of Be from Materion is $35.00 for the good guy price. They wanted $40.0 but got them for a bit less, and this is just the raw diaphragm. So you can extrapolate for the larger diameter needed for a compression driver. As far as the Premundur there are quite a few different electric steel alloys but they are all expensive and one of the major manufacturers here in the US, Carpenter Steel wants lots of money and wants to sell by the ton. They would basically ignore anyone wanting to use the material for compression drivers, not enough quantity to interest them.
I can tell you that the price for just a !" dome tweeter diaphragm made of Be from Materion is $35.00 for the good guy price. They wanted $40.0 but got them for a bit less, and this is just the raw diaphragm. So you can extrapolate for the larger diameter needed for a compression driver. As far as the Premundur there are quite a few different electric steel alloys but they are all expensive and one of the major manufacturers here in the US, Carpenter Steel wants lots of money and wants to sell by the ton. They would basically ignore anyone wanting to use the material for compression drivers, not enough quantity to interest them.
Cost Remains the Issue
I am well aware of the costs and who makes what. For complete implementations see ALE [1] and Goto Unit [2] drivers. With the application of modern engineering tools and manufacturing processes, these units could be made better than they already are. The issue remains, the price point at which they can be delivered into the marketplace. Here, material costs remain the principal deterrent to sales volume.
References
[1] ALE Acoustic
Home
[2] Goto Unit
6moons.com - industry features: Goto Unit
I am well aware of the costs and who makes what. For complete implementations see ALE [1] and Goto Unit [2] drivers. With the application of modern engineering tools and manufacturing processes, these units could be made better than they already are. The issue remains, the price point at which they can be delivered into the marketplace. Here, material costs remain the principal deterrent to sales volume.
References
[1] ALE Acoustic
Home
[2] Goto Unit
6moons.com - industry features: Goto Unit
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Here's a measurement of a Klipsch horn with Klipsch's own K69 2" driver (blue) and JBL 2446 with truextent beryllium diaphragm (green). No doubt which is better. Would be fun to try ALE driver(s), but they are not exactly cheap. 1/24 octave smoothing, nearfield indoor.
Attachments
The thing about that use of the high dollar electric steel vs the normal low carbon steel is that unless you are going into saturation or have a limit volume of metal it may prove to be of no real improvement. In a compression driver there may be enough volume of metal that the flux density in the gap is not an issue, there may just be some differences in eddy currents and such. You would have to run some analysis on the magnetic motor to see if the difference was required requiring the high dollar metal. I have done some modeling on a motor I am working on and it has made a difference in a pole piece where there was limited metal mass, but the rest of the motor works just as well with plain low carbon steel. The pole piece was vented and had limited mass and here the upgrade to the higher cost metal would make some difference in gap flux density.