Unfortunately, the bass sections of many full-range speakers are dismal compared to a quality sub, both the drivers and cabinet sections. You’re getting into $10K/pair speakers before the bass sections will match the quality of even a $600 sub.
Then add the fact that with full range speakers, the amplifier is taxed with driving the bass woofers as well as the mids and tweeters. High-passing the mains and relieving their amp of the 3 lowest octaves has the same effect of doubling, maybe even tripling the amplifier power.
Also, there’s an advantage in being able to place the bass drivers somewhere other than the same plane as the mids and tweets. This is because the optimal room placement for the mids and highs is often a compromise for the bass freqs, due to their omnidirectional nature and long wavelengths.
The downside to subs is of course integration with the mains. I find it’s much easier with a 4th-order, active crossover between the subs and mains amplifier, something similar to the JL CR-1.
Then add the fact that with full range speakers, the amplifier is taxed with driving the bass woofers as well as the mids and tweeters. High-passing the mains and relieving their amp of the 3 lowest octaves has the same effect of doubling, maybe even tripling the amplifier power.
Also, there’s an advantage in being able to place the bass drivers somewhere other than the same plane as the mids and tweets. This is because the optimal room placement for the mids and highs is often a compromise for the bass freqs, due to their omnidirectional nature and long wavelengths.
The downside to subs is of course integration with the mains. I find it’s much easier with a 4th-order, active crossover between the subs and mains amplifier, something similar to the JL CR-1.