Subwoofer low frequency extension.

[A800]

And this relates to capacity. How much capacity is needed, then depends on what we see as meaningful spl, at least it should be audible.

At the listening position, audible means approximately:
90dB at 10Hz
80dB at 20Hz
70dB at 30Hz

Tactile feel - to feel the sound physically on your body - starts at around 80-90dB, but is very dependent on mechanical properties of the floor at very low frequencies. This also depends on the properites of the sound field - the intensity and particle velocity.

Those detection levels will be higher if sound at higher frequencies are present, the higher frequencies will mask the ultra-low frequencies.

For realistic spl levels, it makes sense to dimension for around 110-120dB. Then you will be able to play quite loud, and have a nice physical impact.

A subwoofer is measured at a given distance, in specified surroundings, often 2pi/ground-plane. How loud it is in-room at the listening position depends on placement of subwoofer and listener, room size, and room loss. A small sealed room with rigid walls will be louder that a large, open space. Fortunately, room gain increases with lower frequency, in a sealed room. The bad side is that intensity and particle velocity decreases.

So we see that a subwoofer needs more output at lower frequencies to be usable. Since output from all subwoofers decreases as frequency goes down, we see that is will be the capacity at the lowest frequencies that sets the capacity limit for the system. So to get usable extension well below 20hz in a large room, the subwoofers will need to be quite large.

But for most music, those capacity requirements can be relaxed quite a bit, because music rarely has very loud levels of ultra-low bass, typically max spl will be limited by capacity in the 30hz-and-above range.

Thanks for the detailed answer.

 

[Kvalsvoll]

https://www.kvalsvoll.com/Articles/CompactSubwooferTechnology.htm

This one is also interesting.

It is very interesting, but not really relevant to this thread, it is about one specific technical implementation of subwoofers. Questions and discussion may be best suited for the "Desperate dealers forum".

 

[A800]

It is very interesting, but not really relevant to this thread, it is about one specific technical implementation of subwoofers. Questions and discussion may be best suited for the "Desperate dealers forum".

LOL!

 

[RCAguy]

None of those numbers are useful. The only meaningful specification for a subwoofer/bass-system is spl output capacity in the frequency range it is meant to reproduce. Frequency response in itself does not matter.

I have repeatedly explained why and how and what, even wrote an article on this specific subject, I do believe I have posted links to that article also on this forum. For someone with a technical background, this is not very difficult to understand.

But isn't frequency response how consistent SPL output is over the range?

 

[Kvalsvoll]

But isn't frequency response how consistent SPL output is over the range?

Yes, but what we hear is the frequency response in-room at the listening position, at the sound pressure level we listen at. And this response is determined by the room and placement, so we need to do some eq to adjust, so we get a reasonably response at the location where we listen. And to do that, we need a processor so we can adjust, and what we can adjust is limited within the capacity range of the bass- system.

Then we see that the frequency response of the subwoofer/bass-system in itself is not important, as long as there is capacity. In practical situations, the low frequency limit will be determined by the capacity of the bass-system, where capacity drops off to useless below some frequency.

 

[RCAguy]

What we “hear” is our auditory perception, described by ISO:226 2003 (updated Fletcher & Munson). SPL (after room and processing) is not equal to loudness in the subwoofer range. And it also describes why bass system distortion (relatively unaffected by controller and room) is much more important than in the other 8 audible octaves.

 

[Chrispy]

Check these out https://www.audiosciencereview.com/...ith-10-12-and-15-inch-subwoofer-review.17335/