Recent advances in substrateless all-silicon microphotonics are leading towards a much-needed general-purpose platform for compact integrated devices and systems for terahertz waves. Devices of this sort are innately efficient, as high-resistivity intrinsic silicon exhibits near-negligible absorption in the terahertz range. On the other hand, this platform offers no capacity or potential to directly implement active devices such as sources and detectors of terahertz signals. Hybrid integration presents a viable means to address this shortcoming, by incorporating a separately-fabricated InP integrated circuit together with silicon microphotonics. In this work, we present a two-channel coherent receiver for terahertz waves that is composed of a pair of self-oscillating-mixer-based resonant tunneling diode (RTD) detector chips and a silicon photonic diplexer. This device is deployed in terahertz-range communications experiments, where it is shown that aggregate data rates in excess of 50 Gbit/s may be supported. Finally, a viable approach to physically package the hybrid-integrated terahertz receiver, and electrically interface the RTDs with standard coaxial ports, is presented.