That looks like a typical nearfield sweep for a high inductance driver like Fi makes and has nothing to do with it being an IB driver. You can see the basic response measurement of the Fi SSD 18" driver at data-bass.com and it looks almost identical.Does this look like a typical nearfield sweep for a IB subwoofer?
- All processing turned off in the receiver. (pure direct mode)
- nothing in the path to the amp. Reciever---->EP4000
- Mic a few inches off the cone