There's no replacement for displacement.
You can get some very good low end with small drivers in a transmission line enclosure. But you can't get level and transient response. Can't do it.
Which is why you want sub-woofers. And not just one or two. Each sub creates standing waves in a room. So the frequency response is uneven throughout the room. So what you want to do is to have multiple subs, so that their respective standing waves even things out in the room. I have three subs for that reason.
If you want more level, you need bigger drivers. If you don't need higher levels, you can get away with smaller drivers. My subs have 10" drivers for instance, but with three of them, it meets my needs.
You can get some very good low end with small drivers in a transmission line enclosure. But you can't get level and transient response. Can't do it.
Which is why you want sub-woofers. And not just one or two. Each sub creates standing waves in a room. So the frequency response is uneven throughout the room. So what you want to do is to have multiple subs, so that their respective standing waves even things out in the room. I have three subs for that reason.
If you want more level, you need bigger drivers. If you don't need higher levels, you can get away with smaller drivers. My subs have 10" drivers for instance, but with three of them, it meets my needs.