Why would Audio Physic use Seas aluminum cones rather than magnesium? Practically all their recent models use one or two 15 or 18 cm Seas aluminum cone drivers as a midrange or bass/mid in their two-way systems. Differences to regular Seas L15 or L18 models seem to be black rather than clear finish of the cone, the use of a cylindrical rather than pointed phase plug, and a red rubber ring that is glued to the back circumference of the cone (supposed to dampen break-up resonances, but I don't see how a strongish rubber surround wouldn't do the same job).
Their top model, the Kronos, which costs way more than most engineers make per annum, uses a 22 cm aluminum cone midrange. It is a coax which has a Scan Speak revelator suspended in front of the (shortish) phase plug. As for the midrange, the only difference apparent from the text in those high-gloss audio magazines is the use of a titanium rather than aluminum VC former in order to lower mechanical losses (but Kapton would do an even better job, so what is the point of titanium? mechanical stability?).
I can understand that they don't want to pay for the Excel series cosmetics such as copper back plates. Maybe they are using Excel motors, who knows? But at the prices of their regular top line and particularly the Kronos, they should be able to afford magnesium cones. Their resonances would be higher, and they would be lighter for the same stiffness. Knowing that Mr Gerhard used to advocate first and second order XOs, and given the use of 19 mm Vifa and 25 mm Vifa and Scan ring radiators for tweeters which don't like to be crossed over too low, I really wonder if the famous red rubber ring is enough to suppress the cone resonances we all know aluminum cones have in abundance. Or is there a special advantage to aluminum that magnesium cannot offer?
Their top model, the Kronos, which costs way more than most engineers make per annum, uses a 22 cm aluminum cone midrange. It is a coax which has a Scan Speak revelator suspended in front of the (shortish) phase plug. As for the midrange, the only difference apparent from the text in those high-gloss audio magazines is the use of a titanium rather than aluminum VC former in order to lower mechanical losses (but Kapton would do an even better job, so what is the point of titanium? mechanical stability?).
I can understand that they don't want to pay for the Excel series cosmetics such as copper back plates. Maybe they are using Excel motors, who knows? But at the prices of their regular top line and particularly the Kronos, they should be able to afford magnesium cones. Their resonances would be higher, and they would be lighter for the same stiffness. Knowing that Mr Gerhard used to advocate first and second order XOs, and given the use of 19 mm Vifa and 25 mm Vifa and Scan ring radiators for tweeters which don't like to be crossed over too low, I really wonder if the famous red rubber ring is enough to suppress the cone resonances we all know aluminum cones have in abundance. Or is there a special advantage to aluminum that magnesium cannot offer?
For Midrange it must be for cost.
Magnesium, due to its lightness, slow sound transportation, and natural dampening from low hardness, would seem the best metal for cones with modest physical stress. i.e. tweeters, midranges and low Xmax high efficiency woofers. A Mg bell would not ring very well.
Titanium is significantly heavier, denser, and stronger, than magnesium. This would make Titanium well suited to subwoofers.
Aluminum's physical properties are close to magnesium. Al is 1.6x heavier, but has lower tensile strength unless alloyed, and absorbs less vibrational energy. Aluminum is much cheaper than magnesium. Most Al alloys, like 6000 series, have higher tensile strength than Mg. Al cone break-up modes are slightly worst than MG due mainly to the higher mass/strength ratio.
Carbon fiber appears to be the best long term cone material for midrange and high efficiency woofers. The ideal carbon fiber cone would likely be a curve-linear profile woven from continuous fiber before thermoset in resin. When a Tiawan company invests in this technology, we could see a new plateau in cone technology. Today, most carbon fiber cones use coarse random fibers in resin, or a cut sheet glued into a linear profile.
Today, low cost Kevlar fibers are smoother and easier to weave than carbon fiber, and hence top labs like B&W have been able to bring up manufacturing lines for woven midrange cones. The weaving technology, cone profile, and resin strongly determine the break-up modes.
element ....Density.....Velocity....Young... Rigity...Bulkmod..mineral... Brinell..Tensile Strength
Titanium ......4057...... 4140...... 116...... 44...... 110...... 6...... 716...... 345
Aluminum ......2700...... 5100...... 70....... 26....... 76.... 2.75..... 245...... 179
Magnesium ...1738 ......4602 ......45 .......17 .......45 .....2.5 .....260 ......275
Beryllium .....1848 .....13000 .....287 ......132 ......130 .....5.5 .....600 ......300
Carbon Fiber ..1780 .....3200 ......250 .......38 .......80..... 2.6 .....235 ......276
DensityKg m-3
Velocity sound m/s
Young’s modulus /GPa
Rigity modulus /GPa
Bulk modulus /GPa
Mineral hardness
Brinell hardness /MNm-2
Tensile Strength MPa
Magnesium, due to its lightness, slow sound transportation, and natural dampening from low hardness, would seem the best metal for cones with modest physical stress. i.e. tweeters, midranges and low Xmax high efficiency woofers. A Mg bell would not ring very well.
Titanium is significantly heavier, denser, and stronger, than magnesium. This would make Titanium well suited to subwoofers.
Aluminum's physical properties are close to magnesium. Al is 1.6x heavier, but has lower tensile strength unless alloyed, and absorbs less vibrational energy. Aluminum is much cheaper than magnesium. Most Al alloys, like 6000 series, have higher tensile strength than Mg. Al cone break-up modes are slightly worst than MG due mainly to the higher mass/strength ratio.
Carbon fiber appears to be the best long term cone material for midrange and high efficiency woofers. The ideal carbon fiber cone would likely be a curve-linear profile woven from continuous fiber before thermoset in resin. When a Tiawan company invests in this technology, we could see a new plateau in cone technology. Today, most carbon fiber cones use coarse random fibers in resin, or a cut sheet glued into a linear profile.
Today, low cost Kevlar fibers are smoother and easier to weave than carbon fiber, and hence top labs like B&W have been able to bring up manufacturing lines for woven midrange cones. The weaving technology, cone profile, and resin strongly determine the break-up modes.
element ....Density.....Velocity....Young... Rigity...Bulkmod..mineral... Brinell..Tensile Strength
Titanium ......4057...... 4140...... 116...... 44...... 110...... 6...... 716...... 345
Aluminum ......2700...... 5100...... 70....... 26....... 76.... 2.75..... 245...... 179
Magnesium ...1738 ......4602 ......45 .......17 .......45 .....2.5 .....260 ......275
Beryllium .....1848 .....13000 .....287 ......132 ......130 .....5.5 .....600 ......300
Carbon Fiber ..1780 .....3200 ......250 .......38 .......80..... 2.6 .....235 ......276
DensityKg m-3
Velocity sound m/s
Young’s modulus /GPa
Rigity modulus /GPa
Bulk modulus /GPa
Mineral hardness
Brinell hardness /MNm-2
Tensile Strength MPa
At a NY audio show many years ago I asked the Audio Physic designer (from Germany) why he chose to abandon the great sounding Seas magnesium cones. He briefly replied that magnesium cones "weather" (I understood him to mean the spotty whitish surface oxidation that can occur -- I my experience this oxidation may seriuosly affect appearance but is not audible (I have several pairs of older EXCEL cones that apparently don't have the newer protective coating).
However, it seems that appearances are just as, if not more, important to manufacturers as the audible performance -- especially when selling expensive speakers...
However, it seems that appearances are just as, if not more, important to manufacturers as the audible performance -- especially when selling expensive speakers...
Most probably that was Joachim Gerhard (now designer at his own brand), if I'm not mistaken he is also a member here, maybe he can respond.
The look is why so many speaker companies use the terrible sounding Accuton drivers and the Seas magnesium cones, which are good speakers indeed, but require too many sacrifices at the crossover and implementation stages.
Anyone who has started using the Seas Exotic midwoofer/tweeter? its not that easy to find an alnico woofer/tweeter neither with this design in these days, however it looks ugly and this will mask the shineness of the speaker and most audio morons would not buy it.
Anyone who has started using the Seas Exotic midwoofer/tweeter? its not that easy to find an alnico woofer/tweeter neither with this design in these days, however it looks ugly and this will mask the shineness of the speaker and most audio morons would not buy it.
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