I was working on a 3 inch mid dome Neodymium motor project where I could achieve inductance of as much low as 0.05 at 8 ohm and at 4 ohm its 0.04 as much as a tweeter. Extensive amounts of copper is used to achieve this but also at very affordable price. The discussions are going on for using silver plating on the top plate with anti corrosion coating on it.
Currently the entire top plate and bottom cup part has got .1mm copper plating.
Irrespective of the cone breakup of the dome the motors ability is giving as much as 10khz flat response so that the motor is not complained that the inductance is pulling of the freq extension.
Just very happy to reduce that levels and we are thinking to apply patents on it.
Haven`t measured the harmonic distortion yet we believe they must be extremely low but we are incorporating the highend suspension system to avoid the rocking modes which plagues most of the 3 inch domes the only dome that we know who is using suspension is ATC.
Linear suspension
Suspension open on both sides to have compression free operation
Voice coil vents provide some more reduction in the compression.
Spoke to the companies who are providing the suspension and they said larger the suspension more will be its linearity. 167mm Overall suspension diameter.
76.4 Voice coil diameter.
The moving mass is still 2.78gm
Qts .36
BL 8.10T
Sensitivity 95.41db
Qms 7.5
Voice coil former Very Rigid black glass Fibre with Nomex collar
Copper clad aluminium wire
Heatsink attached from behind to cool the motor.
Neodymium magnet N40 ( higher grade ) with dimensions 50 x 12 mm
Underhung motor
Linear displacement +/-.45mm
The problems what is observed or to be considered from the competing mid domes
The suspension is very small ( not really that linear )
Ferrite magnet ( not as good control as what the Neodymium magnets can give )
Coating of the suspension: I see almost all domes observed in the market except very few that the overcoating on the dome is not only done on the mid part of the dome but also on the suspension which kills the free movement of the dome.
Lets see
pic of the dome and the suspension type ( size of the suspension will be much larger than shown here but the material is same )
The speciality of the suspension material is the threads woven has very low twisting tendencies at higher excursion. Since the excursion of the mid domes are lower it works perfectly linear.
please let me know your opinions or questions
Currently the entire top plate and bottom cup part has got .1mm copper plating.
Irrespective of the cone breakup of the dome the motors ability is giving as much as 10khz flat response so that the motor is not complained that the inductance is pulling of the freq extension.
Just very happy to reduce that levels and we are thinking to apply patents on it.
Haven`t measured the harmonic distortion yet we believe they must be extremely low but we are incorporating the highend suspension system to avoid the rocking modes which plagues most of the 3 inch domes the only dome that we know who is using suspension is ATC.
Linear suspension
Suspension open on both sides to have compression free operation
Voice coil vents provide some more reduction in the compression.
Spoke to the companies who are providing the suspension and they said larger the suspension more will be its linearity. 167mm Overall suspension diameter.
76.4 Voice coil diameter.
The moving mass is still 2.78gm
Qts .36
BL 8.10T
Sensitivity 95.41db
Qms 7.5
Voice coil former Very Rigid black glass Fibre with Nomex collar
Copper clad aluminium wire
Heatsink attached from behind to cool the motor.
Neodymium magnet N40 ( higher grade ) with dimensions 50 x 12 mm
Underhung motor
Linear displacement +/-.45mm
The problems what is observed or to be considered from the competing mid domes
The suspension is very small ( not really that linear )
Ferrite magnet ( not as good control as what the Neodymium magnets can give )
Coating of the suspension: I see almost all domes observed in the market except very few that the overcoating on the dome is not only done on the mid part of the dome but also on the suspension which kills the free movement of the dome.
Lets see
pic of the dome and the suspension type ( size of the suspension will be much larger than shown here but the material is same )
The speciality of the suspension material is the threads woven has very low twisting tendencies at higher excursion. Since the excursion of the mid domes are lower it works perfectly linear.
please let me know your opinions or questions
Attachments
Congratulations with an exiting looking driver. I guess it is Kurt Müller parts....
You have made a good motor, but I dont see how you can hold a patent on it. from what I understand this is how many 1" dome motors are made. By the way I finde the softparts much more difficult to get right. Good luck on you design. Will you show some frequence responce meassurements? Will you go start selling it?
You have made a good motor, but I dont see how you can hold a patent on it. from what I understand this is how many 1" dome motors are made. By the way I finde the softparts much more difficult to get right. Good luck on you design. Will you show some frequence responce meassurements? Will you go start selling it?
For limited period of time if any requests roll in we might consider to sell..
the inductance reduction plays major part on
Freq response
Transient response
Linear impedance
constant Q parameters in over the broad spectrum of the bandpass of the crossover
Lower harmonic distortion especially critical in the midrange
Glass fiber former for low mech losses and high Qm for high resolution
Nomex collar for sweeter upper midrange
Freq response will follow soon
Any inputs or suggestions are welcome..
If anybody is interested in group buy I can ship these...
Looks nice!
The only thing is that Xmax seems a bit limited compared to some other 3" domes.
The Volt VM752 (very similar to the ATC 'S' version) states an Xmax of 3mm compared to the 0.45mm of yours. It is however somewhat more expensive than the non-S ATC.
Volt uses double suspension and generally their published data errs on the conservative side.
Next to nothing seems to be known of the PMC dome which is made by PMC themselves and not sold separately.
The only thing is that Xmax seems a bit limited compared to some other 3" domes.
The Volt VM752 (very similar to the ATC 'S' version) states an Xmax of 3mm compared to the 0.45mm of yours. It is however somewhat more expensive than the non-S ATC.
Volt uses double suspension and generally their published data errs on the conservative side.
Next to nothing seems to be known of the PMC dome which is made by PMC themselves and not sold separately.
While I'm no expert on drivers I noticed that your proposed dome mid has very little xmax considering you propose it as a midrange driver. If I assume it would have ~ 20 square cm sd then if I have my math correct the 100 dB breakpoint is at about 950 hz which is very high.
The ATC dome has +-3 mm xmax, so it has the same breakpoint at ~ 300 hz which is more useful as a midrange driver.
The ATC dome has +-3 mm xmax, so it has the same breakpoint at ~ 300 hz which is more useful as a midrange driver.
Rythmsandy, what means Nomex collar. I know nomex is a material. My English might be to limited.
Does the copper plating really work, it seems thin compard to a copper cap.
It seems to be a nice driver. Do you know Tang Bands 3" dome, it seems to follow a similar design concept.
The measurements on the excellent Tang Band 3" dome can be found at the link below. If you can beat that, you've got something. Xmax needs to be sufficient to support operation down to 500-700Hz, e.g. 2mm one-way at 10% down on the BL curve. You will reduce the driver efficiency if you open up the gap, so maybe there is a compromise at just over 1mm... If its a neo motor then the Q can be allowed to rise without problems. Will this have a built in chamber or open back?
Zaph|Audio
It's the third one down. Measurements are found using the "Comparison App" link, found just above the driver listings.
Last edited:
The proposed xmax is being limited by the top plate thickness which is 4mm at the moment we have another option of using 9mm top plate and resulting in the following parameters..
Linear excursion +/-3mm from the motor ability but the diaphragm ability is being limited to +/-1.8mm max excursion.
so we have used 7mm top plate to make it 1.95mm linear hence the dome xmax limit is reached.
but the sensitivity is dropped to 91.57db but I think its still fine.
This version of the motor is not as expensive as ATC or Volt but we are planning in around USD $190
Regarding the collar ( it contributes the signature )
http://circuitcellar.com/wp-content/uploads/2012/02/Klasco-p1-Voice-Coil.jpg
Our dome is much lighter than the ATC or Volt
Double spiders are not recommended as the linearity is disturbed
Copper platting of .1mm on the entire surface is huge no part is left uncovered so its beneficial in getting the inductance down to some level so we have used super heavy copper rings hence reduction of the inductance..
PMC uses scanspeak dome midrange which is overhung top plate is just 2mm and the inductance could have been better than .13mH
Face plate is plastic change it to metal or spruce you will notice the difference between both the changes. It has the same principle of horn material.
Linear excursion +/-3mm from the motor ability but the diaphragm ability is being limited to +/-1.8mm max excursion.
so we have used 7mm top plate to make it 1.95mm linear hence the dome xmax limit is reached.
but the sensitivity is dropped to 91.57db but I think its still fine.
This version of the motor is not as expensive as ATC or Volt but we are planning in around USD $190
Regarding the collar ( it contributes the signature )
http://circuitcellar.com/wp-content/uploads/2012/02/Klasco-p1-Voice-Coil.jpg
Our dome is much lighter than the ATC or Volt
Double spiders are not recommended as the linearity is disturbed
Copper platting of .1mm on the entire surface is huge no part is left uncovered so its beneficial in getting the inductance down to some level so we have used super heavy copper rings hence reduction of the inductance..
PMC uses scanspeak dome midrange which is overhung top plate is just 2mm and the inductance could have been better than .13mH
Face plate is plastic change it to metal or spruce you will notice the difference between both the changes. It has the same principle of horn material.
PMC only uses the scanspeak in their cheaper speakers, the more expensive ones use PMCs own dome mid which is made in their factory. It is if anything a bit more substantial than the 9kg Volt but since they don't sell it separately there are is no detailed info available at all. I suspect it to be very similar to the Volt or the 'S' ATC.
yeah PMC uses scanspeak dome midrange in their entry level speakers but the IB2s and top of the professional monitors have got their own dome thats good part. Technically they can still incorporate that design for lower end also instead of paying it to scanspeak so that they make more value for the product. I dont think it would cost them more for them.
I have even seen the PMC proprietary dome assembly couldnt find a suspension. http://hifi-unlimited.blogspot.in/2011/12/pmc-factory-tour-part-ii-hifi-trio.html For the kind of coating what they have did I suspect the mass is higher than 3gm for the dome but when the mass increases without the suspension there will be spurious motion which affects the IMD alot and also the decay will be long.
Last edited:
I just have a question from my end as what sensitivity would you prefer 91.5db with complete underhung with xmax being +/-2mm with max mech limit being +/-2mm?
or
95.5db with underhung but with xmax being +/-0.45mm
in fact we have designed the 95.5db at 8 ohm for the auditorium installed applications
for home hifi we prefer the 91.5db as we wouldnt require that much sensitivity in home applications.
But with 95.5db we can use it with two woofers each with 87db at 8 ohm in parallel to achieve 93db at 4 ohms and the mid as its 8 ohm will do 92.5db as a slight dip of .5db in midrange doesnt make the mid sound forward and tad there in between the bass and highs and sits there rather jump out of it...
or
95.5db with underhung but with xmax being +/-0.45mm
in fact we have designed the 95.5db at 8 ohm for the auditorium installed applications
for home hifi we prefer the 91.5db as we wouldnt require that much sensitivity in home applications.
But with 95.5db we can use it with two woofers each with 87db at 8 ohm in parallel to achieve 93db at 4 ohms and the mid as its 8 ohm will do 92.5db as a slight dip of .5db in midrange doesnt make the mid sound forward and tad there in between the bass and highs and sits there rather jump out of it...
I guess that depends on if you want to market it as a a midrange driver or an upper midrange driver.
Thanks for the link, it really is a beast that PMC dome.
Personally I'd prefer 2mm Xmax as clean power is fairly cheap these days and I'm really only interested in active speakers.
For home audio the usual midrange sensitivity need not exceed 90dB. Even 87dB would be OK. If the midrange is only used above 500Hz the passband will be 99% above the baffle step. On the other hand, if the thermal power limit is low then high efficiency is helpful.
I also would like to see Xmax that is at least 1.5mm.
Why is the dome (suspension?) limited to 2mm Xmech? Is that a hard limit, e.g. the moving parts hit the top plate, or is that where the suspension stiffness increases rapidly?
This fails to include the effect of the baffle step, which is a loss of up to 6dB at lower frequencies. The woofers may need to be as much as 6db higher in sensitivity because at low frequencies they are radiating into twice as large a "space" as at middle frequencies. If you put the woofer right at the floor you can get back most of the loss, but that is not always the design of a loudspeaker.