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

Gotta be the single-panel Maggies, Wolf. But the old 3-panel Tympanis have plenty of bass, and of a very high quality There are people using the two bass panels of Tympanis as woofers, and even as subs!

QUAD ESL’s have even less bass than Maggies, but are not nearly as big.

Check out the Neat Audio Iota Plus speaker recently reviewed in Stereophile this month by staffer Ken Micallef. 

However, careful,...... John Atkinson, the magazine's technical guru was disappointed by their " measured performance", and Micallef's enthusiasm for the product is somewhat over the top.  The speaker should do 40Hz cleanly and without boom, according to him.  Good Luck locating a Neat Audio dealer where you can audition them.   

BTW, the speakers are a midget floor stander at 17 inches tall  (on their 1.5 inch spikes). Interesting product,  but not inexpensive   

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Mapman,

In Germany a chap called Matthias has been customising Ohm speakers for some years now and he does an active version of the "5000" series (with John’s approval). In Germany, this is a good idea because their Omnidirectional market is much stronger than anywhere else and the competition prices can take your breath away (German Physic, MBL etc).

Looks like John has fully embraced the idea and is scaling up. ;^)

One implication of the Fletcher-Munson curves is that the ear is quite sensitive to changes in SPL at low frequencies (recall that the curves bunch up in the bass region). Thus a 5 dB change at 40 Hz or so is subjectively comparable to a 10 dB change at 1 kHz. So a small change in SPL makes a disproportionately large change in perceived loudness in the bass region.

The ear’s sensitivity to small changes in SPL in the bass region implies that it’s pretty good at detecting the unnaturally lumpy bass that most rooms impose on speakers. Which in turn implies that we can expect significant subjective improvement from adopting an approach that smoothes out the in-room bass. While I’m an advocate of distributed multisub systems, ime improvements can show up simply from locating the bass sources in a speaker (the woofers and ports) at different distances from the room boundaries as much as is feasible.

As for fairly compact speakers that can do 20 Hz, I once loaned a pair of high-efficiency stand-mount speakers (about 1 cubic foot internal volume) to an equalizer manufacturer for an audio show. He planned to use a subwoofer system as well (not one of mine). The subwoofer crapped out the first day of the show, which would have been a disaster, but this guy was pretty resourceful. You see, my speaker had a large woofer (12") with good excursion (9 mm) and high thermal power handling (900 watts music program). So he used a powerful amp and dialed in a lot of EQ and as I recall he got ballpark 20 Hz bass after all, according to his measurements. Of course this was in a boomy hotel room, which in this case was helpful.  Now I didn't sell the speaker packaged with his equalizer so my example doesn't really count, but it does illustrate one way to get 20 Hz at useful SPL from a fairly small box: Aggressive equalization of a woofer that can handle it. 

Duke

dealer/manufacturer

Wow tostado, a piano tuner! Man, that takes a real good ear and lots of training. I worked with one pianist who wasn’t much of a player (he grew up in the era of the British Prog Bands, hence couldn’t play rhythmically to save his life) but was a competent tuner, which is what he ended up doing as a career. Surprisingly, a lot of real good guitarists had a hard time tuning before the invention of the electronic tuner. They would get each individual string close, but chords would still sound sour. The only guy I played with (R.I.P.) who was great at tuning a guitar had perfect pitch, and playing with him spoiled me for most others. Pianos, with two strings per key and many more keys than the six strings of a standard guitar, are much, much harder to tune. Twelve-string guitars are notoriously impossible to keep tuned for very long, especially the thin-necked Rickenbackers. Jim McGuinn was always out of tune on live Byrds shows!

But yeah, real low frequencies don’t sound like a "note" being played. And a lot of criticism of subwoofers sounding fat, bloated, slow, etc., is more the result of "room boom" (dimension-related resonances/standing waves), the very low frequencies the sub(s)are playing exciting the room modes/nodes that aren’t excited without the sub(s). One of the benefits of dipole woofers and subs is that they excite fewer of those room dimensions (the length not the width, if firing down the length of the room), the result being less room boom. Harry Pearson long preferred the bass panels of the Magneplanar Tympani loudspeakers (a dipole, of course) for their very taut, lean bass and midbass, in preference to omnipole dynamic cone woofers in enclosures. Some fanatics still use the Tympani panels as woofers/subs, and GR Research in conjunction with Rythmik Audio offers an Open Baffle/Dipole sub that uses a pair of 12" woofers mounted in an "H-frame". State-of-the-Art bass!

The Kii Three was designed to provide extremely deep bass from a relatively small and surprisingly lightweight cabinet. An additional objective was to create dispersion characteristics equalling those of a flush mount monitor, notwithstanding the relatively narrow baffle. The smaller the loudspeaker front, the earlier (higher in frequency) the speakers dispersion will become omnidirectional – an unwelcome property in loudspeakers that studio planners go to great lengths to avoid.

Room acoustics issues appear predominantly at low frequencies and when trying to achieve precise stereo imaging. While the latter can be optimized by comparatively simple measures, taming the low frequencies takes a much larger effort (see also our special edition Room Acoustics and Studio Design, June 2016). This is where the Kii Three comes in, creating a consistent cardioid sound field all the way down to just short of 50Hz, then gradually becoming omnidirectional below this point. With the Speaker placed close to a wall and thus at an acoustically benign boundary distance, the resulting level increase below 50Hz can easily be treated in a compensation filter.

All this complex signal processing costs the user dearly – not financially, but by introducing a latency of 90 milliseconds which would disqualify the Kii Three for any kind of real time work in the control room. To avoid this, the monitor can be set to a low latency mode by pushing a button marked “P/R“ on the back panel, reducing the latency to only a handful of DSP samples plus the DAC latency for a total value in the one millisecond range. The low latency mode replaces the highly complex low frequency filters by simplified algorithms, leaving the sonic properties of the monitor basically unchanged. The only tradeoff is reduced precision at low frequencies, but at a very reasonable magnitude with only small impact on aural evaluation.

• LF extension without distortion figures is kind-of meaningless
• Most sounds below ~32Hz are from environmental noise rather than music
• Room size and in-room response is a huge factor. It’s one thing to achieve flat response to 20Hz in a closet or Honda Civic vs. a 5,000 cu. ft. listening room
• We have not very clearly defined "speaker". For example, the DuNu DN2000J is a lot smaller than the Triton II+ and are fairly flat down to 5Hz with low distortion. It can do this because the "room size" is only a few cubic mm.

The lowest frequencies produced by almost all musical instruments are not as low as commonly believed. For instance, whilst 28Hz was above stated as being produced by an upright bass, that instrument's lowest note---the E string played "open", is actually located at 42Hz. The 4-string electric bass (often incorrectly called a bass guitar, even by John Atkinson, who should know better) produces that same note and frequency as it's lowest.

There are a few instruments which produce frequencies lower than 42Hz, including pipe organ, grand piano, and contra bassoon. Some recordings made in very large spaces---cathedrals, concert halls---contain the very low frequencies those rooms support. The ability to reproduce those very low frequency "room sounds" is one of the benefits of good subwoofers. A good recording of a pipe organ played in a cathedral will contain the "shuddering" sound that combination produces. It is an enormous, massive, thrilling sound!