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RE: Fostex Super Woofer fw880 amplification options...

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In Reply to: RE: Fostex Super Woofer fw880 amplification options... posted by kef on August 02, 2024 at 19:54:23

Hi
Driving it is not a real issue but what to do with the driver might be.
The T&S parameters for an fW800 are at the link below. I couldn't find an 880. These would let you model the response for what ever box you want before building.

A Qt of .69 at Fs of 25Hz, suggests a an infinite baffle (very large box volume) would turn this into a monster. IF you had a closet you could use or could take advantage of an adjacent room for a back volume, that would give you in room response pretty flat well below 25Hz!

https://www.madisoundspeakerstore.com/approx-31-woofers/fostex-fw800hs-31.5-super-woofer/
woofer (Open in New Window)

Follow Ups:

RE: Fostex Super Woofer fw880 amplification options... - Paul Joppa 07:46:16 08/11/24 (1)
To put some numbers on it, Vas = 1500 liters (53 cubic feet) and will get you down to 35Hz at QT = 1.0. The suggested minimum 500 liters gives a 3dB peak at 50Hz, falling off below that.

The frequency response graph shows another +5dB resonance peak at 50Hz, but that may be a measurement anomaly.
- RE: Fostex Super Woofer fw880 amplification options... - tomservo 14:10:09 08/11/24 (0)
  That's what i was getting at indirectly, a qt of .69 in very close to maximally flat already, raising the resonance raises the Q as well so like the response curve shown, is under-damped.
  IF one could use an adjacent room as the back volume, then not only would the drivers response go lower but would no doubt tie into the room gain slope that low too, potentially extending the low corner another octave or more for free.
  edit;
  If one had an amplifier that had an output impedance adjustment like some "old days" amps had, like one at Grommes back then, one could adjust the output impedance either positive or negative. Making it positive gives the woofer a higher Q but negative output impedance makes the woofer have a lower Q.
  More important back then to accommodate different size cabinets, before one could design based on the driver's T&S parameters.
  
  Edits: 08/12/24

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