for what its worth...from Bass Box Pro
Typical Characteristics of a Closed Box Woofer
• Qts greater than 0.3.
• Low resonance (Fs). High moving mass (Mms) and compliance (Vas, Cms).
• Large Xmax (small woofers: 2-4 mm; large woofers: 5-8 mm).
• Moderately strong motor (BL).
• EBP less than or equal to 50.
Typical Characteristics of a Vented Box Woofer
• Qts from 0.2 to 0.5.
• Moderate resonance (Fs) and moving mass (Mms).
• High compliance (Vas, Cms) is not necessary but can be beneficial.
• Moderate Xmax (small woofers:
• Strong motor (BL).
• EBP greater than or equal to 100.
• Avoid woofers with excessive unknown losses.
Typical Characteristics of a Single-Tuned Bandpass Box Woofer
• Qts greater than 0.3.
• Low resonance (Fs). High moving mass (Mms) and compliance (Vas, Cms).
• Large Xmax (small woofers: 2-4 mm; large woofers: 5-8 mm).
• Moderately strong motor (BL).
• Compatible with a wide range of EBP values.
Typical Characteristics of a Double-Tuned Bandpass Box Woofer
• Qts greater than 0.4.
• Moderate resonance (Fs) and moving mass (Mms).
• High compliance (Vas, Cms) is not necessary but can be beneficial.
• Moderate Xmax (small woofers:
• Strong motor (BL).
Typical Characteristics of a Passive Radiator Box Woofer
• Qts from 0.2 to 0.35.
• Moderate resonance (Fs) and moving mass (Mms).
• High compliance (Vas, Cms) is not necessary but can be beneficial.
• Moderate Xmax (small woofers:
• Strong motor (BL).
• EBP greater than or equal to 100.
• Avoid woofers with excessive unknown losses.
Notes:
EBP is the efficiency bandwidth product and it is calculated by dividing Fs by Qes. If Qes is unknown, EBP can be estimated with: Fs / Qts. BassBox Pro provides an EBP indicator on the Parameters tab of the Driver Properties window and on the Driver Locator.
Although vented, double-tuned bandpass and passive radiator boxes do not usually require a woofer with a large Xmax, it won't hurt to have a large Xmax. In fact, a generous Xmax is always good because it reduces a source of nonlinear distortion.
Most vented and passive radiator boxes have a leakage loss parameter (QL) that is around 7. An excessively "lossy" driver can reduce this and should be avoided unless you know how to adjust QL accordingly. Sources of loss through a woofer are a porous dust cap or "lossy" surround.