Biamping typically means using two amplifiers per channel so I did not know you were talking about "active" biamping. I don't think the CX-A5000 has individual analog gain volume dials. You could use the level trims (digital) but you then will be limited to the typical 0.5 dB resolution so I guess that won't work.
I guess I should have explained that I don't use passive crossovers...
Here is a link to the definition of Bi-amping.
https://en.wikipedia.org/wiki/Bi-amping_and_tri-amping
Quoted from the above link.
"However, the passive crossover itself is inefficient, so splitting the frequencies electronically before these are amplified is a way to avoid this problem. In such a case, an amplifier each powers a frequency range determined by an active crossover to each of the drive units. The technique is primarily used in large-scale audio applications such as sound amplification for concerts, in portable
powered speakers and by hi-fi enthusiasts"
"Most audible differences are subtle. If at all noticeable, benefits of bi-amping cannot be realized if passive crossover networks of a speaker system are not removed.
[1] Benefits include transients are less likely to cause amplifier overload (clipping) and/or speaker damage, and reduced intermodulation distortion, elimination of errors introduced by low frequency passive crossover, reduction of load to the load presented to the power amplifier, better matching of power amplifier and speaker driver and others.
[2]"
I was hoping that the CX-5000 had internal gain controls that were accessible when bi-amping, but apparently it doesn't. Gain controls are required to match the outputs of the horns to the woofers in my setup. If I don't adjust the gains then my horns will be almost 20db louder than my bass bins.