Tim (Noble100)
We are on the same page. However, I would be doing it for the gain in bass definition and overall frequency balance, more than to relieve my primary amplifiers of any stress. The 845PX's normally use a 6db/octave passive crossover in front of two different audio step-up transformers that receive, respectively, bass and treble frequencies after the x-over. This configuration, however, creates a nasty impedance dip at mid-frequencies, in addition to sucking energy across the resistor used in the hi-pass filter. 2-3 years ago, I replaced the treble transformer with a very high quality full range transformer, which enable me to ditch the RC network that creates the hi-pass; I still use an inductor in front of the original SL bass transformer, albeit I replaced the OEM inductor with an 12-ga air core type. This mod hugely improved the efficiency of the speaker; I daresay it could be driven by less than 50W to very loud sound pressures. My OTLs can do about 100W, and they are loafing at all times. It also dramatically improved dynamics. I measured impedance v frequency across the audio range, after the mod, and I see 20 ohms or greater from about 100 Hz to 5kHz. Below 100 Hz, impedance is rising. Above 5kHz, it falls to about 6-8 ohms at 10 Khz. This is an ideal match for an OTL.
I did mention that someone here had pointed out that two of the 4 woofers could go behind the panels. Sorry for not remembering to credit you with that insight. I've known Duke for a long time; I bought my 845s from him. I will give him a call soon. On his website today, I do see the Swarm, but I don't see the Debra system. I'll look again.
We are on the same page. However, I would be doing it for the gain in bass definition and overall frequency balance, more than to relieve my primary amplifiers of any stress. The 845PX's normally use a 6db/octave passive crossover in front of two different audio step-up transformers that receive, respectively, bass and treble frequencies after the x-over. This configuration, however, creates a nasty impedance dip at mid-frequencies, in addition to sucking energy across the resistor used in the hi-pass filter. 2-3 years ago, I replaced the treble transformer with a very high quality full range transformer, which enable me to ditch the RC network that creates the hi-pass; I still use an inductor in front of the original SL bass transformer, albeit I replaced the OEM inductor with an 12-ga air core type. This mod hugely improved the efficiency of the speaker; I daresay it could be driven by less than 50W to very loud sound pressures. My OTLs can do about 100W, and they are loafing at all times. It also dramatically improved dynamics. I measured impedance v frequency across the audio range, after the mod, and I see 20 ohms or greater from about 100 Hz to 5kHz. Below 100 Hz, impedance is rising. Above 5kHz, it falls to about 6-8 ohms at 10 Khz. This is an ideal match for an OTL.
I did mention that someone here had pointed out that two of the 4 woofers could go behind the panels. Sorry for not remembering to credit you with that insight. I've known Duke for a long time; I bought my 845s from him. I will give him a call soon. On his website today, I do see the Swarm, but I don't see the Debra system. I'll look again.