[freddyi]

a few years back -- two components: series cap and shunt inductor, usual "boost" price of lower Z but may not be as low as using a transformer to reflect a lower Z   -- I had a 300 watt rated Samson amp violently "ratchet" due to ~2.3 ohm dip triggering protection whether vented or open baffle - in contrast a 50 watt rated NAD amp sailed along  -  LF slope adds an order - this could reduce out of band excursion. plus could protect a driver if an amp's rail dumps.  I may have heard some saturation of the Erse coil (?)

for comparison 'd like to see half-space plots and Z-in of various T-bass

effects upon Madison X21


500uF/20->30mH applied to a 12" PYM1298 in little Karlson box vs un-equalized X21 - the little K could play with more upper bass impact than the 21" OB

[panomaniac]

Running your woofer thru a series cap with shunt inductor?  Hmmmm....

Isn't that a 2nd order high pass, or am I missing something? 

[freddyi]

its an underdamped 2nd order network and provides 6-8dB of "boost"  - - - look at the graph of its effects on the Madison X21 open baffle woofer- -- theres not much free lunch in passive "boost" but getting it centered might make sense  - - - look at the input Z of Graham's circuit - -one user showed a drop to ~ 1ohm - that's pretty low for some solid state amps.  high source Z such as SET w/o feedback would not source the needed current for either circuit to work..

[Graham Maynard]

Hi Freddy,

Thinking about your circuit, the series capacitor is going to lead to extreme LF phase shift between voltage and current around driver-baffle Fs, and maybe this is what was triggering output sensing on the Samson.

My experience of driving any LS through such a low value series capacitance is that the LF becomes too resonant and does not sound good.

Yes there can be an impedance dip with my 'T'-bass circuit, but it remains within about 50 degrees and at circa 2.5R with an 8R driver should not be a problem prior to driver over-excursion limiting the undistorted SPL.   
The biggest problem would be laying hands on a transformer just to try it.   
http://www.gmweb2.net/new_page_1.htm

Cheers ........... Graham.