f6 bandwidth defined?

[kramskoi]

how do we define f6 bandwidth in sealed and vented subwoofers?

[Marzen]

I'm not sure if this is what you're asking, but in general I think you can factor in the following:
A vented enclosure acts as a 4th order HP accoustic filter (24dB), add a rumble filter for an additional 2nd order HP (12dB) & you have a 36dB slope which is rather substantial when compared to the more gradual 2nd order HP properties of a sealed box. Comparing the two would show the vented box having a much narrower bandwidth due the faster rate of roll off.
-Ward

[kramskoi]

I'm not sure if this is what you're asking, but in general I think you can factor in the following:
A vented enclosure acts as a 4th order HP accoustic filter (24dB), add a rumble filter for an additional 2nd order HP (12dB) & you have a 36dB slope which is rather substantial when compared to the more gradual 2nd order HP properties of a sealed box. Comparing the two would show the vented box having a much narrower bandwidth due the faster rate of roll off.
-Ward

Thanks for the reply...i should clarify. I'm wondering whether it (F6 or -6dB point) is measured from Fb or the highest peak in the frequency response.

[Amphiprion]

I always thought it was defined relative to the nominal passband sensitivity.

[Marzen]

I always thought it was defined relative to the nominal passband sensitivity.

Ditto, I've been using an averaged passband level for reference.
Why, are you looking at a design with a large hump at the knee like with a super boom box alignment with a Q >1.2?
-Ward