Big-Greg hits the nail on the head. People say all the time “my speakers go down to xx hz, I don’t need a sub.” The truth is very few speakers, even larger floor standing speakers, are FLAT to 40 hz. Most have a bit of a midbass hump, which gives a bit of a peak in the 70-90hz range, which then allows a stated -6db point in the 30-40 hz range.
Even those speakers that can dig down into the 30hz range, have limited output and suffer from increase distortion in the bass frequencies. To be able to reproduce decent levels (i.e. 105 db) at 30hz and below in all but the smallest room, with reasonable distortion, takes at least 4 10” long throw drivers, two 12”, or 1 15” (all have approximately the same displacement). Go down to 8” drivers (assuming you can find decent sounding ones with an xmax of at least 15mm) you are up to 8 drivers. You can cheat it a bit with large vented enclosures, transmission lines, or folded horns, but do end up with tradeoffs in group delay.
Many will disagree about the above, but it is nearly always true. Take the Revel Performa F228be, a wonderful, full range, $10,000 pair of floor standing speakers. At 50hz, they are coming off their midbass peak to 0db. At 30hz they are 5db down from flat, and 9 db down from their 80-100hz output. Again, this is measured at lower volume levels, so no dynamic compression.
https://www.stereophile.com/content/revel-performa-f228be-loudspeaker-measurements
$57,000 Wilsons, same thing: https://www.stereophile.com/content/wilson-audio-specialties-alexia-series-2-loudspeaker-measurements
As Big-Greg says it isn’t about boom (which is 60-90 hz). It is the deep, almost inaudible bass, especially in live recordings, which give the sense of a real space. When dialed in properly, you hear no sub, just an increased dynamic range and music that has an amazing foundation.
Even those speakers that can dig down into the 30hz range, have limited output and suffer from increase distortion in the bass frequencies. To be able to reproduce decent levels (i.e. 105 db) at 30hz and below in all but the smallest room, with reasonable distortion, takes at least 4 10” long throw drivers, two 12”, or 1 15” (all have approximately the same displacement). Go down to 8” drivers (assuming you can find decent sounding ones with an xmax of at least 15mm) you are up to 8 drivers. You can cheat it a bit with large vented enclosures, transmission lines, or folded horns, but do end up with tradeoffs in group delay.
Many will disagree about the above, but it is nearly always true. Take the Revel Performa F228be, a wonderful, full range, $10,000 pair of floor standing speakers. At 50hz, they are coming off their midbass peak to 0db. At 30hz they are 5db down from flat, and 9 db down from their 80-100hz output. Again, this is measured at lower volume levels, so no dynamic compression.
https://www.stereophile.com/content/revel-performa-f228be-loudspeaker-measurements
$57,000 Wilsons, same thing: https://www.stereophile.com/content/wilson-audio-specialties-alexia-series-2-loudspeaker-measurements
As Big-Greg says it isn’t about boom (which is 60-90 hz). It is the deep, almost inaudible bass, especially in live recordings, which give the sense of a real space. When dialed in properly, you hear no sub, just an increased dynamic range and music that has an amazing foundation.