frequency range for instrument vs speaker

>After seeing this link in another thread, I wonder about this. Let say that you don't listen to any classical instrument/music, normal rock and pop with no heavy synthetizer, just drum, guitar, etc, it seems that there isn't really any need for speakers that go much below 40Hz, considering that the lowest instrument, the kick drum (I assume it is the same thing as bass drum?) only go down to 50Hz.

You may still want speakers that play much lower because you need larger drivers for dynamics at higher bass frequencies and the consumer market expects such speakers to have low frequency extension which makes getting one without the other difficult.

Maximum excursion limited SPL from a monopole operating into free space at 1 meter is

102.4dB + 20log(displacement) + 40 log(f) with displacement in m^3

or

102.4dB + 20log(travel) + 20 log(area) with travel in meters an area in meters^2 if you prefer.

Output at the maximum linear excursion into full space for various representative drivers one meter away is as follows at 120, 80, 40, and 20Hz. Many drivers have less excursion and lower output. Subtract 3-5dB getting to your listening position in a typical living and more for a larger space.

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer.

Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB
12" Peerless 830500 483 x 12.5 121dB 114dB 102dB 90dB

Where jazz sounds great at 85dBC average and good recordings have 20dB of dynamic range peaks are hitting 105-107dB a meter from each speaker. Feeding _Take Five_ through 60Hz second order Butterworth IIR low-pass filters I noted right channel low frequency peaks 10dB down from that; although that's still 30 times the acoustic power you can squeeze out of a 6" driver at 40Hz.

You may even want sub-woofers in spite of not being a bass-head. They're one way to get displacement past 100Hz without compromising with a larger mid-range that won't mate as well to most conventional dome tweeters. They let you have the SBIR bass null caused by the front wall reflection (at 1130 / 4 / distance in feet which is 70Hz at 4 feet and 57Hz at a more audiophile friendly 5 feet) out of the speakers' pass-bands. Multiple sub-woofers are also an effective way to minimize the big peaks and nulls you get below the room's Schroeder frequency somewhere in the 100-200Hz range for most domestic spaces.

Drew, thanks for your information. I certainly don't disagree that giving bass extension can help to improve midbass performance as well. However, I don't think that it would answer my question regarding playing music that contains fundamentals that are only 50Hz or above as to what kind of sound, information or contents those recording contains that are below 50Hz? I am not trying to pick on recording studio, sound engineer regarding equalization or anything like that but actually try to understand more about what I hear.

06-18-12: Suteetat
Drew, thanks for your information. I certainly don't disagree that giving bass extension can help to improve midbass performance as well. However, I don't think that it would answer my question regarding playing music that contains fundamentals that are only 50Hz or above as to what kind of sound, information or contents those recording contains that are below 50Hz?

You make a good point that if speakers are strong, linear, and honest down to 40 Hz (not 50--it's just not low enough), you are going to hear most of the music and the system will come across as having excellent bass. However, a great number of speakers actually start rolling off around 100 Hz and have pooped out around 50-60 Hz and they are definitely missing something. Even augmenting such a system with a sub that itself rolls off at 36 Hz will make a positive and noticeable difference.

Furthermore, not all kick drums' fundamental tone is around 50 Hz; it depends on the drum size and the tuning. My vintage Slingerland 14"x22" has a lower thump than that, and many kick drums today are much larger, like 20"x24". Even the fundamental on a snare drum can provide a workout for a good woofer.

Another thing: the low E of a 4-string electric bass is around 42Hz, but many rock/pop bass players use a 5-string, whose lowest note is about 32 Hz. It's just one whole note above the bottom A of a standard piano. If you have a system that's truly flat to 40 Hz it'll sound strong on rock and pop, but if it's flat to 30 Hz you'll hear the difference on many recordings, especially later ones.

For me, having a flat response down to at least 30hz is also for hearing the space the music was recorded in. I like listening to a lot of live recorded jazz tracks and such and find the low bass replays the resonance of the particular room of the performance. i.e, one live jazz album I have sounds as if it was played in a venue in a high rise building on a windy day. There is just that low frequency resonance that you get in such a building. Or I was once listening to a track of a choir in an old large church and there must of been a truck passing the road outside the church. It had that unique sound of outside traffic noise passing through the thick stone walls of an old church.

Maybe some people think such sounds will subtract from the music... but to me it adds to the sense of 'being there'. And individual tracks have their unique character that regard.

Johnnyb, thanks for your information. That's exactly the kind of info I am looking for. Any idea how low those bigger kick drum can go down to? I also have not been able to find much information about the big bass drum that are used in some classical music such as Verdi's Requiem, Stravinsky's Firebird as far as their frequency is concerned.