|
| Symbol |
Description |
| Bl |
Motor force factor in Tesla-meters.
|
| Fs |
Resonance frequency in Hz. |
| EBP |
Efficiency Bandwidth Product, defined by Small as Fs/Qes and is used as a rule
of thumb for enclosure selection. EBP values under 50 suggest the use of a sealed
enclosure. EBP values over 100 suggest the use of a vented enclosure. Drivers with
EBP values between 50-100 are adaptable for use in either type of enclosure. |
| Mms |
Moving mass, including cone and air, in grams. |
| Qes |
Electrical Q, dimensionless. |
| Qts |
Total Q, dimensionless. |
| Vd |
Volume displaced, the product of Sd (the cone area) and Xmax, in cubic
cemtimeters. |
| Xmax |
Maximum linear excursion in mm. |
| Znom |
Nominal impedance in Ohms. |
Additional notes:
- "Range/dB" specifies usable range and P-P passband ripple. This data is from
the FR graphs and may not me the same as the manufacturer's specs.
- "Range" is determined by off-axis response. In many cases, on-axis response
extends much higher.
- Passband ripple is for on-axis response. Typically, off-axis response may be
3-5 dB lower.
- Passband ripple is peak-peak. That is to say the width of the window in
which the ripple will fit. For example, a driver with +/- 1 dB ripple in the
passband would be spec'ed at 2.0 dB.
- On woofers, subwoofers, and mid/bass drivers, the bottom end is determined
by the systems design and so, in the list, is the lowest attainable frequency
in a suitable enclosure.
- The "Fmax" spec is the highest frequency at which the driver should be used
in normal operation. This number represents the minimum of four separate
specs:
- The frequency at which the driver may be expected to being beaming, due to
its diameter. This number may be extended if the driver uses a phase
plug.
- Any point where the FR graph shows signs of distress. This also applies
to drivers with really nasty breakup modes (e.g. metal or Kevlar cones),
where I typically set this number at least two octaves below the first
breakup mode.
- The manufacturer's specs and/or recommendations. Often, these are wildly
optimistic.
- Feedback from people who've used them.
- Passband ripple may include the effect of a Zobel if warranted.
|
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