As far as I understand, in a ceramic motor, maybe as much as 50% of the magnet's field energy is wasted outside the pole piece/plate. A neodymium motor has a more concentrated magnetic flux with less leakage and a more "intense" field in the voicecoil gap.
With less stray leakage around the voicecoil gap in the neo motor, I guess that the magnetic field just above and below the gap is relatively weak compared with the field inside the gap, while a ceramic-motor will have a stronger leakage and a more gradually decrease of field strength just outside the gap (?).
If this is right, does it mean that a voicecoil in a neo-woofer will stop more brutally when it reaches its Xmax, compared to the voicecoil in a ceramic-woofer which will have some stray field force to push against as it exceeds its Xmax?
I'm asking, because I don't know what mid-priced 8" midwoofer to choose as a woofer in a small 3-way standmount; the Satori MW19 or the Wavecor WF223.
Seas Excel, Scan-Speak, Accuton, Wavecor and Audio Technology – known for making midwoofers with deep, powerful bass – use ceramic magnets in overhung motors and neo magnets in underhung motors. And then you have Peerless NE and Satori midwoofers with overhung neo motors, known to be excellent "200-2000Hz drivers", but they are no hard-hitting woofers, they don't have the high SPL macrodynamic punch and bass power of same sized Scan-Speak Revelators. Partly because of the chosen motor structure?
Is there any logic in this? Can this explain the difference between the Satori WO24 woofer and the MW19 midwoofer? And does this mean that the MW19 is less useful as a woofer in a 3-way?
With less stray leakage around the voicecoil gap in the neo motor, I guess that the magnetic field just above and below the gap is relatively weak compared with the field inside the gap, while a ceramic-motor will have a stronger leakage and a more gradually decrease of field strength just outside the gap (?).
If this is right, does it mean that a voicecoil in a neo-woofer will stop more brutally when it reaches its Xmax, compared to the voicecoil in a ceramic-woofer which will have some stray field force to push against as it exceeds its Xmax?
I'm asking, because I don't know what mid-priced 8" midwoofer to choose as a woofer in a small 3-way standmount; the Satori MW19 or the Wavecor WF223.
Seas Excel, Scan-Speak, Accuton, Wavecor and Audio Technology – known for making midwoofers with deep, powerful bass – use ceramic magnets in overhung motors and neo magnets in underhung motors. And then you have Peerless NE and Satori midwoofers with overhung neo motors, known to be excellent "200-2000Hz drivers", but they are no hard-hitting woofers, they don't have the high SPL macrodynamic punch and bass power of same sized Scan-Speak Revelators. Partly because of the chosen motor structure?
Is there any logic in this? Can this explain the difference between the Satori WO24 woofer and the MW19 midwoofer? And does this mean that the MW19 is less useful as a woofer in a 3-way?
You can download FEMM and try it for yourself.
As for the bottom end, well, the RS225 is hard to beat, even when you take cost out of the equation.
As for the bottom end, well, the RS225 is hard to beat, even when you take cost out of the equation.
If you are planning to run your speakers near or at xmax you better get more drivers or a larger one or both
I think....
SB_Acoustics engineers optimized the 9" WO24 and the 8" SB23NBAC designs as pure woofers, typically used in a 3-way TMW design, each with a crossover optimized for woofer bass plus room equalization below the baffle step frequency.
SB_Acoustics engineers optimized the 7.5" MW19 design to perform well in a SEALED midbass in a TM with modest baffle step compensation like I built, and also for modestly deeper bass as a PORTED woofer in a 2 or a 2.5way TMM design.
2.5 way == similar M-W tone -plus- lower cost passive crossover parts -plus- same baffle width as M.
A well designed TM-WW with the 9" WO24 or 8" SB23NBAC should perform best. Passive W inductors are expensive. I bi-amp with sealed passive TM and sealed active (TM) - W.
Celef: yes, I agree, from the lower midrange and down, size & numbers matter more than (almost) anything else. And I think that's why the "new" type of extreme midwoofers from Purifi and SS Ellipticor measure Bls +/-8mm at AudioXpress. When Nick Mason hits the snare drum in some passages on The Wall, midwoofers move a considerable distance, even at normal listening volumes, most of them easily exceeding their linear Xmax (in a normal loudspeaker). And that’s the core of my question: will stray field differences above/below the gap in different motor structures influence on the drivers linear Xmax? I don't know, but I know that linear Xmax matters a lot, and that is why I've always had preferences for 6-7" midwoofers from Scan-Speak and Seas Excel, with linear Xmax around +/-5mm, and with enough force to back it up.
LineSource: thank you for clearing things up. The WO24 is a 3-way woofer, and the MW19 is a 2-way midwoofer with t/s parameters suitable for sealed cabinets. I think Mr. V. Dickason once said something about placing the crossover either below 200Hz or above 650Hz, to secure a natural reproduction of the lower fundamentals. I don't like to cross low, good sounding inductors becomes large and expensive, the midrange driver has to be a 7" midwoofer in a large cabinet, and there is always the risk that the low crossover will mess with the systems bass-impedance rollercoaster.
So I prefer to build 3-ways with highish crossovers in the 600-800Hz region. Up until now, I've used Seas W18e and W15cy, and SS 8545, 8530 and 8531 as woofers, and midranges like the old Seas MCA11 and the new Eton 3-212. Now I look for a suitable and moderately priced 8" 40-800Hz 3-way woofer, and are looking at WO24, MW19 and Wavecor WF223. I think the WO24 has limitations above 200Hz, the MW19 has limitations below 200Hz, and that the WF223 (or the RS225) may be the best 8" 40-800Hz alternative?
LineSource: thank you for clearing things up. The WO24 is a 3-way woofer, and the MW19 is a 2-way midwoofer with t/s parameters suitable for sealed cabinets. I think Mr. V. Dickason once said something about placing the crossover either below 200Hz or above 650Hz, to secure a natural reproduction of the lower fundamentals. I don't like to cross low, good sounding inductors becomes large and expensive, the midrange driver has to be a 7" midwoofer in a large cabinet, and there is always the risk that the low crossover will mess with the systems bass-impedance rollercoaster.
So I prefer to build 3-ways with highish crossovers in the 600-800Hz region. Up until now, I've used Seas W18e and W15cy, and SS 8545, 8530 and 8531 as woofers, and midranges like the old Seas MCA11 and the new Eton 3-212. Now I look for a suitable and moderately priced 8" 40-800Hz 3-way woofer, and are looking at WO24, MW19 and Wavecor WF223. I think the WO24 has limitations above 200Hz, the MW19 has limitations below 200Hz, and that the WF223 (or the RS225) may be the best 8" 40-800Hz alternative?
If I understand correctly, you require a high sound pressure level and therefore conclude that your woofer will travel beyond its xmax. If so, it might be possible to prevent the woofer from exceeding xmax by redesigning the loudspeaker system. Would it be possible to pick a woofer with a larger air displacement, increase the lower cut-off frequency of or use a vented box to reduce cone excursion?
The way the magnetic field drops off outside of the magnetic gap already is included in xmax, assuming that xmax is defined as the excursion at which Bl has dropped to 82% of its peak value. Beware that different manufacturers have different definitions of xmax. What happens beyond xmax is described in the Klippel graphs Bl(x) of the particular woofers. Maybe you can find some Klippel analyses of ceramic and neo magnet woofers. Without these data, only guessing remains.
The way the magnetic field drops off outside of the magnetic gap already is included in xmax, assuming that xmax is defined as the excursion at which Bl has dropped to 82% of its peak value. Beware that different manufacturers have different definitions of xmax. What happens beyond xmax is described in the Klippel graphs Bl(x) of the particular woofers. Maybe you can find some Klippel analyses of ceramic and neo magnet woofers. Without these data, only guessing remains.
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