I've noticed some confusion lately about terminology with regards to notches. With regards to whether the notch is 'bottomless' or 'top-less' has to do with the lack of resistor usage. When the resistor is used to set the Q of the notch, and ultimately the magnitude of the peak or valley between the Fc points, then these are not of the former mentioned types. What I'm equating below was/has been accepted terminology in the DIY circles since the time I started almost 20 years ago.
A top-less notch is that of an infinite added attenuation (or tank) by using a C in parallel with an L, placed in series with the driver like that of a parallel notch missing the R. The impedance will approach infinity between the 2 Fc points. ie- no top.
A bottomless notch is that of a fully shorted out bandwidth (or trap) by using a C in series with L, placed across a driver. This is like that of a series notch sans R. The impedance will approach 0, ie- no bottom.
I hope this is useful and clears up any confusion,
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