I read a review of another Kanto sub that claimed that in standby it makes"small booms" every fifteen minutes or so and a big boom when it comes out of sleep. Was his unit defective or hooked up wrong or is this expected?
Sounds like a defective sub tbh. In my experience our subs come in and out of standby with no external noise, just a small electronic click from the relay inside the power section. I would consider booming noises grounds for exchange.