Does the passive crossover network in the JBL SRX715s also have built-in eq'ing? In full-range mode, I tweaked the PEQs with the biamped tunings recommended in the Driverack 260, and they didn't sound as good with these settings in comparison to leaving the PEQs flat. Comparing the biamp tuning to the flat passive tuning was very similar sounding, so I was wondering if the passive crossover network also had some built-in eq'ing. Thanks.
In full range mode you're going through the high pass and low pass filters (collectively known as the crossover) in the speaker, which likely includes circuits to match the output of the horn to the woofer. Horns are typically more sensitive (more output per watt) than woofers so usually it is necessary to pad down the HF so the output is matched to the LF. There may be other tweaks going on as well in the passive crossovers.
Based on JBLs schematic, biamp is directly to the drivers so the external crossover needs to take into account the difference between sensitivity of the horn and of the woofer. The -9dB across the HF mentioned by Jon Cooper is almost certainly for this reason. Again, there may be other things as well factored into the biamp tunings and passive crossovers.
Bottom line is the biamp PEQ recommendations are not applicable to full range operation of the speaker.