Ochto 8 Amplifier
Given that the Keystone speaker has 7 drivers, and the Bedrock has 8 drivers, it seemed reasonable to design an 8 channel amplifier to driver each speaker - albeit it with 1 unused amplifier channel when driving a Keystone.
The sensitivity and impedance of all drivers used in the Keystone and Bedrock are approximately 4 ohm, with power specifications such that a the Hypex NC252MP module would be suitable, with a power rating of 250W info 4-ohm, at 1% total harmonic distortion at 1khz when all channels are driven.
So basically - the NC252MP modules are a good option, and cost effective given that a Keystone and Bedrock pair requires 30 channels of amplification.
The other benefit is that we preserve identical voltage gain across all drivers, which would not likely be the case if using different specification amplification for each driver.
Finally, the NC25MP modules do not necessarily require active cooling and it is possible to passively dissipate heat.
Amplifier Case
After much searching, I chose to commission a custom case from Ghent Audio, involving:
- 4 x NC252MP Hypex modules, surface mounted on a aluminium case (contact me for details)
- Use of a breakout board to take Tascam D-Sub cable (8 ch) to 4 x 2ch NC252MP boards
- Power distribution board