What are the smallest speakers that are clean and flat down to 20hz?

As far as 'the room will have some influence certainly'.  I completely disagree with Ralph on this because he is seriously underestimating the effect  the room has on bass response and has chosen to ignore the mountain of scientific data compiled on this subject

I think actually we're on the same page. But Mapman is talking about 20Hz response and so am I. That's a bit different than **perception** of bass, which is very much affected by the room (for example I have a room resonance at 26Hz in my room, which tends to reinforce bass impact, but its at 26Hz no 20Hz. I tend to be very literal it that helps...). IOW the room isn't going to change the actual frequency response of the speaker, although it will affect to a large extent the **perception** of bass coming from the speaker.

Duke LeJeurne of Audiokinesis makes an excellent subwoofer system he calls 'The Swarm'. It is a set of multiple subs that can be distributed so you don't have problems with bass in some parts of the room (like the side wall) and not in others (like the listening chair).

As a general rule of thumb I usually regard the room as half of the overall system sound.

If the SPL is 3 dB down at 20 Hz then you will hear 20 Hz as half as loud as any frequency that is measured as 0 dB. If 20 Hz was found to be - 6 dB it would be 1/4 as loud as a frequency at 0 dB.

Actually in the above case being down 3 db it would take double the amplifier power to make up the difference but the ear would not hear the -3db as half as loud. If the speaker were 6 db down then that tends to sound closer to 'half as loud' and would take 4x amplifier power to correct.

geoffkait: If the SPL is 3 dB down at 20 Hz then you will hear 20 Hz as half as loud as any frequency that is measured as 0 dB. If 20 Hz was found to be - 6 dB it would be 1/4 as loud as a frequency at 0 dB.

to which atmasphere replied,

"Actually in the above case being down 3 db it would take double the amplifier power to make up the difference but the ear would not hear the -3db as half as loud. If the speaker were 6 db down then that tends to sound closer to ’half as loud’ and would take 4x amplifier power to correct."

Uh, the microphone hears what the ear hears. Forget the amplifier! You’re making it too complicated. You’re hearing 20 Hz at 3 dB down. Half as loud. Example - Suppose you were listening to a jackhammer and you measured the SPL where you were standing to be 110 dB. Then you stepped backwards - a few steps at a time - until the SPL measured 107 dB it would be then half as loud. 3 dB down.  Case solved.

Actually here is what the ear hears and its far from flat at the extreme top and bottom range of our ears in particular:

http://www.independentrecording.net/irn/resources/freqchart/ear_sensitivity.htm

For example according to this what measures correctly as flat at say 20 hz will be heard down more than 70db by the typical human ear in the worst case at the lower volume limit of human hearing. Less so but still down at higher volumes. So significant equalization/boost is needed to "hear it as flat". How much depends on volume. Same true with the high end.

Whereas a microphone used to measure the levels accurately would have flat response end to end. Our ears are far from that as shown in the chart.

mapman OP
"Actually here is what the ear hears and its far from flat at the extreme top and bottom range of our ears:

http://www.independentrecording.net/irn/resources/freqchart/ear_sensitivity.htm

For example according to this what measures correctly as flat at say 20 hz will be heard down more than 70db by the typical human ear. So significant equalization/boost is needed to "hear it as flat". Same true with the high end."

That’s absurd. You will pay big bucks to hear 20 Hz 70 dB down? Are you crazy? 70 dB down is almost as low as the noise. Besides, you're the one that says it's flat at 20 Hz. Hel-loo!

Its not absurd at all. Its a well documented fact.

Turn the volume up and things are better but still far from flat.

Equalization is the only practical solution if one truly cares beyond that.

It helps to manage expectations though to realize and understand that what we hear is not the same as what measures as flat.

If the speaker rolls off at extreme frequencies, then we hear even less.    

The ability to not roll off at frequency extremes and make things even worse is what separates the men from the boys.

Compensating with equalization is then analogous to using performance enhancing drugs.  that is assuming the amp and speakers can handle it.  That's a different story.   if they can't,  then the results will surely not be good.