Right. The only proper way to hook up subwoofers is with a dedicated two way subwoofer crossover preferably digital. The preamp outputs go to the crossover which will have dedicated main amp and sub amp outputs all line level. This rolls off the main speakers improving integration and lowering distortion in the main speakers. Good bass management systems will give you a wide choice of crossover point and slopes. The best will also automatically correct for phase and time and do room control.
Any other method is challenged one way or another. REL approach is just a cheap way to do it. Their insistence that is is the best is a rouge to sell more subwoofers. They know people who are buying their inexpensive subs do not want to spend more money and/or deal with more complexity. If they recommended the right way nobody would buy their subs. What you have here is a dysfunctional relationship between a manufacturer and it's clients destined to produce mediocrity, an interesting relationship common in the political world. The best subwoofer systems use passive subwoofers. You have to die laughing. You have all these audiophiles spending ridiculous money to keep their electronics isolated but they are fine jamming an amplifier into a earthquake replicating machine wherein the pressures vary from +- 30 PSI. So, why doesn't the industry produce passive subs? Passive subs in most cases are not much less expensive. Plate amps are dirt cheap and they make a lot of money selling them. People love all in one cheap solutions. It is the culture. JL Audio cuts it both ways. They make amplified subs with crossovers like everyone else but for people who want to do it right they make an analog subwoofer crossover to go between the preamp and amplifiers. The DEQX Premate has a wonderful bass management system with which you can set up a SOTA subwoofer system.
Any other method is challenged one way or another. REL approach is just a cheap way to do it. Their insistence that is is the best is a rouge to sell more subwoofers. They know people who are buying their inexpensive subs do not want to spend more money and/or deal with more complexity. If they recommended the right way nobody would buy their subs. What you have here is a dysfunctional relationship between a manufacturer and it's clients destined to produce mediocrity, an interesting relationship common in the political world. The best subwoofer systems use passive subwoofers. You have to die laughing. You have all these audiophiles spending ridiculous money to keep their electronics isolated but they are fine jamming an amplifier into a earthquake replicating machine wherein the pressures vary from +- 30 PSI. So, why doesn't the industry produce passive subs? Passive subs in most cases are not much less expensive. Plate amps are dirt cheap and they make a lot of money selling them. People love all in one cheap solutions. It is the culture. JL Audio cuts it both ways. They make amplified subs with crossovers like everyone else but for people who want to do it right they make an analog subwoofer crossover to go between the preamp and amplifiers. The DEQX Premate has a wonderful bass management system with which you can set up a SOTA subwoofer system.