SD + XMAX = SPL ...correct?
03-21-2007, 07:57 AM
#31
Originally Posted by Prolifik
im so lost, if this was a class i'd fail.
As much as all of these theories help, they aren't much good because you are talking about drivers without taking the enclosure into consideration.
When was the last time you ran a sub without an enclosure
03-21-2007, 11:33 AM
#32
Personally, I don't care about efficiency, particularly for a subwoofer.
Efficiency = (B^2 * L^2) / (R * Sd^2 * Mms^2)
How can we increase efficiency? Well, we can increase B (magnetic strenght) or L (length of wire in the field). We can also decrease Sd or Mms (which are closely intertwined...higher surface area will likely lead to more Mms).
However, it is also worth noting that decreasing Sd or Mms will also increase Fs. For a subwoofer, this is not a good thing.
If we increase B or L, back EMF is more likely to be a concern, and if increasing L specifically, then we can probably expect inductance to increase as well, which will hurt your transient rise time as well as your upper frequency rolloff.
As far as what seems to be a good combination for high SPL, there are a couple of things worth considering. Firstly, high BL^2/Re is a good thing and indicates actual motor force potential. Secondly, you need to be able to displace a large amount of air. Does this need to be linear and distortion free? No, not at all, which is why it is simply important to have higher Xmech and Xsus, so that the coil can move far enough without any damage. Third, less power compression is preferred, meaning the more linear the motor, suspension, and DC Re, the better; of course, this has sacrifices as keeping BL excessively linear often requires a sacrifice in net BL^2/Re. Lastly, the enclosure is the truly dominating factor. It is a well-known fact that years of experience are required to make a good spl machine. Knowing how your speaker/enclosure combination interacts with your vehicle is absolutely critical to long-term success.
If you really wish to take SPL seriously, meet up with some others in your area who are interested. If they have experience, soak up all the information you can. If no one around you is experienced, buy yourself a TL and start tweaking.
Efficiency = (B^2 * L^2) / (R * Sd^2 * Mms^2)
How can we increase efficiency? Well, we can increase B (magnetic strenght) or L (length of wire in the field). We can also decrease Sd or Mms (which are closely intertwined...higher surface area will likely lead to more Mms).
However, it is also worth noting that decreasing Sd or Mms will also increase Fs. For a subwoofer, this is not a good thing.
If we increase B or L, back EMF is more likely to be a concern, and if increasing L specifically, then we can probably expect inductance to increase as well, which will hurt your transient rise time as well as your upper frequency rolloff.
As far as what seems to be a good combination for high SPL, there are a couple of things worth considering. Firstly, high BL^2/Re is a good thing and indicates actual motor force potential. Secondly, you need to be able to displace a large amount of air. Does this need to be linear and distortion free? No, not at all, which is why it is simply important to have higher Xmech and Xsus, so that the coil can move far enough without any damage. Third, less power compression is preferred, meaning the more linear the motor, suspension, and DC Re, the better; of course, this has sacrifices as keeping BL excessively linear often requires a sacrifice in net BL^2/Re. Lastly, the enclosure is the truly dominating factor. It is a well-known fact that years of experience are required to make a good spl machine. Knowing how your speaker/enclosure combination interacts with your vehicle is absolutely critical to long-term success.
If you really wish to take SPL seriously, meet up with some others in your area who are interested. If they have experience, soak up all the information you can. If no one around you is experienced, buy yourself a TL and start tweaking.
03-21-2007, 08:45 PM
#39
Well, coil diameter alone does not tell you anything about power handling. Power handling is related to the ratio of mass to surface area; more surface area for a given mass is preferable.
The variables when looking at thermal power handling include: coil diameter, coil height, surface area, coil material, number of layerings, former material, cooling system, etc. Simply saying that a 4" diameter voice coil guarantees good SPL is false, as I can design a speaker with a 2.5" voice coil that will handle more power daily and on bursts than on some speakers with 4" diameter voice coils.
The variables when looking at thermal power handling include: coil diameter, coil height, surface area, coil material, number of layerings, former material, cooling system, etc. Simply saying that a 4" diameter voice coil guarantees good SPL is false, as I can design a speaker with a 2.5" voice coil that will handle more power daily and on bursts than on some speakers with 4" diameter voice coils.
