Apologies to all that have offered help, but I fear my memory has confused things more than it should.
Let me try and clarify.
My OBs are 3 way, built by a very gifted designer. Initially it had Saba Greencones in midrange with crossover to an Altec 416B at about 300Hz. All these were driven by a 45 triode amp. Although sounding great I convinced myself that there had to be an even better midrange driver to improve things further.
After much experimentation I found that either a Supravox vintage T215 RTF 64 or SEAS Exotic W8 both improved on the SQ of the Greencones. Each had its own flavour and better still each reached comfortably below 300 Hz without distortion. This allowed me to scrap all passive crossover components on the midrange driver with corresponding improved SQ. Please note, this can only be achieved with drivers that roll off suitably without distortion
Playing just the midrange and tweeter together was the sound I wanted. I just needed to get the bass dialled in, bearing in mind that the midranger was now contributing well below 300Hz.
So I added more inductance to what was the low pass filter to try and achieve 100Hz. At the same time I was lulled into thinking that a modern 15" driver with high Qts like the Eminance Alpha could do a better job in OBs, so I bought a pair. I had by now moved to a dedicated amp for the bass, being the ICE 1000wpc, to achieve higher reserves of power, better damping factor and control of its own volume.
Now after much measurement, and listening, the Alphas went back in the box and the Altecs once again took centre stage.
Currently I am running the midrange without crossovers and settled on 300Hz low pass on the Altec. This gives meat to the lower mid frequencies and gently dialling up the volume of the bass lets me hit the sweet spot.
The bass is good and strong but the driver barely moves. This phenomenon I rightly or wrongly interpreted as not dishing out the bass frequencies, hence my initial question.
