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

Wolf probably not but who would not want to know which actually can do it all best and for how much?

Ct I hear most of the indicated bass notes that were added there. Level I hear is down some at 30 hz and harder to discern lower. That is consistent with fletcher Munson. This was with moderate loud volume on my main system Using an older Pc usb feed to mhdt Constantine dac to arc sp 16 pre-amp to Bel Canto ref1000m amps to Ohm F5 series 3 speakers (12 inch Walsh style driver with on board tone level adjustments to room size).

Room size is ~ 22x34 L shape with normal to slightly lower than normal ceiling height and 3 openings to adjacent rooms. I coukd try again with the doors closed as I usually do to max out low bass.

That at was very cool with the visual display. Thanks.

Check out Neat Motive SX1, a petite floor stander that extends down to 25Hz. http://www.neat.co.uk/p_pages/motiveone.php
A great musical speaker that punches well above its price point

Is there a small, inexpensive car that goes zero to sixty in under 2.5 seconds? And I also want it to handle like a Porsche and hit a top speed of 250 mph. And have a full size trunk with the ability to drive underwater and get great gas mileage…for under 1200 bucks...

I'll need to find a way to download that Phil Collins track as a WAV or MP3 to test since I'm using digital room correction. Might be able to get the audio from Youtube to stream over DLNA as well, but I have not looked into it.

In my case, the loudspeakers are close to the walls (18.5" away on-center) for soundstage reasons more than for bass...which I have too much of in this room without correction.

@dsnyder0cnn

thanks for posting the pic of the room. Wanted to share a past experience I had.

Used to have a setup with full range speakers that needed to be close to the rooms side wall boundaries to achieve the low.. lows, with side treatment much like in your picture. I used the mirror technique. I then changed out amps - actually two different amps and noticed something interesting. I was able to move the speakers away from side walls significantly, but did not lose the low frequencies. The amp that could not produce the low, lows with those speakers, was a 300 wpc Class A/b. Both replacement amps that were able to - 600 wpc Class A and 100 wpc Tube Push Pull Amp.
The previous amp was checked out as ok. It also happened (I have sold it since) to be a brand that is very much paired with the speakers used. i found this interesting.

@the OP - Mapman

So ....did you try that Phil Collins In The Air Tonight bass link test I posted earlier through your main rig yet ? Interested to know what happened.

Cheers

Mikapen
I also boost a bit with controls, to accommodate the Fletcher-Munson effect at low listening levels, if i think about it.

There is no doubt to myself, about this effect. It is very important. For the others benefit I post a link on some info to it.

http://ehomerecordingstudio.com/fletcher-munson-curve/

"
What is it?

The Fletcher Munson Curve is a graph that illustrates an interesting phenomenon of human hearing.

When listening to music through your studio monitors or headphones…
As the actual loudness changes, the perceived loudness our brains hear will change at a different rate, depending on the frequency.

Here’s what I mean:

• At low listening volumes – mid range frequencies sound more prominent, while the low and high frequency ranges seem to fall into the background.

• At high listening volumes – the lows and highs sound more prominent, while the mid range seems comparatively softer.

Yet in reality, the overall tonal balance of the sound remains the same, no matter what the listening volume."

I was just going to mention room gain. It will be 3 - 10 db/octave, depending on a variety of things. 
The posts about relying only on anechoic measurements are fine, but they don't translate directly into what you hear in your room.

My REL pair of subs, in my 18 X 35 room, give me flat to 22, down 3db at 20, from an 85db reference. Unfortunately, down 6db at 16hz. And a peak at 28, which I could soften by speaker direction, but I like 28hz (upright bass low frequency).
Luckily, those ratios exist for me at a 65db reference.
In a fairly large sweet spot that covers 4 listening positions. Placement fairly straightforward - optimizing the subs' distance from corners, energizing the room.

I also boost a bit with controls, to accommodate the Fletcher-Munson effect at low listening levels, if i think about it.

I mention these several things, because they are part of the listening experience. Reference level, room shape and size, room gain, floor coupling, preference, size of sweet spot - and don't forget those peaks, which may fool you into thinking that sound levels at your targeted frequency are deficient.

I'd like to be flat to 16, but I also want to be able to move my speakers. In my mind, tweaking sound with placement experiments is thwarted if you have to invite friends to move the monsters.

I like my setup. The RELs are the first subs that mix so easily with my mains. It's not like LISTEN - I HAVE SUBWOOFERS. It's like Wow, what a nice, integrated full spectrum sound I have.

I've managed to achieve fairly flat/clean response in my 15.5ft x 10.1ft room down to 22Hz, but I'm using four 12" woofers and lots of power to do that at greater than 90dB.

What I've found is that interesting musical content below 40Hz is uncommon. Most of what I hear is stage/studio vibrations, an HVAC switching on, a truck driving by, or other low, rumbly noises that were picked up by the mics during recording and not filtered out. While these sonic artifacts are occasionally interesting, they rarely contribute to the musical performance in any helpful way, so I'd probably be better off rolling things off sharply below about 32Hz. Here's a graph of actual measured response at the listening position before and after correction:

http://www.dsnyder.ws-e.com/photos/potn/Loft_Before_After_and_Target.png

Here's a photo of the actual room from the listening position:

http://www.dsnyder.ws-e.com/photos/potn/loft_wide.jpg

I'm confident that I could achieve similar response with somewhat smaller loudspeakers, but I estimate that minimally four 10" woofers or two 12" woofers would be required in total to achieve this level of bass extension without a separate subwoofer.

I had these loudspeakers before the room...they are obviously a bit large for the space, . If I was buying loudspeakers specifically for this room, I would probably have chosen Harbeth 30.1 or Legacy Audio Calibre and would have been quite happy.

What you ask is impossible, as others have mentioned. Get a set of "bookshelf" style speakers or a small(ish) tower speaker and a good sub woofer, REL, Velodyne, etc. When properly matched and tuned, they can best all but the best full size speakers. The wife acceptance factor is usually on the high side. Also do not discount the possibility of higher end in wall speakers for the satellites. The low frequency is more a function of the room, as others have mentioned, getting enough sub woofer is imperative. 

Second the Kii 3's. They were one of my favorites at NYAS, I am afraid to say I enjoyed them more than Harbeth MK40.2's... The technology in the Kii's makes them a good deal.

Are you going small because your room is small? Or are you trying to avoid overbearing speakers? If it's the former, you may have a lot of hump and suckout treatments to do with those long waves bouncing around.

Something different Bass Test  for Phil Collins - In the Air Tonight  

https://www.youtube.com/watch?v=D0U5qunTUJk&index=1&list=RDD0U5qunTUJk

I think this is something that would require high end PA gear comparable to a touring system, to create any legit reproduction of 20 Hz flat response or not..

No small loudspeaker can output 20hz flat. And if you designed one that did its output would be so low to be of no use. 

Shadorne I think we are saying the same thing. 

Mapman
Compensating with equalization is then analogous to using performance enhancing drugs. that is assuming the amp and speakers can handle it.

imo - The smart speaker manufacturer realizes most rooms do not support 20 hz, and builds this EQ into the speakers design for the full range models. The speakers can handle it if they were designed to. In some cases this changes the load the speaker is looking for and actually makes them easier for the amp. I can give an example if you like.

Hartley 18" and/or 24" subs might be flat to 20 Hz. Everything else is a pig in a poke.

@mapman  

There is no need to boost everything to flat of equal loudness as music is produced for human hearing in the first place / so it is balanced accordingly and a speaker should be flat overall.

One issue with flat to 20 Hz is that rooms give a natural 6db per octave boost as you drop below about 40 Hz. So ideally a speaker should have some roll off if it is to perform flat in a room. A speaker flat to 16 Hz like the ohm f-5015 is likely to sound awful in most rooms without EQ.

Wow, those Ohm speakers remind me of my old BIC Soundspan 600 speakers. 

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.

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!

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.

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.

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.

Here is link to info on OHM 5015:

http://ohmspeaker.com/speakers/beta/

Specs say +/- 3 db at 16hz.

I have OHM F5s which is same cabinet, same main driver (12"), minus built in 15" powered sub and is ported not sealed.

Also smaller similar Walsh 2s with similar driver but 8".

F5 can be adjusted to room size but is overkill for smaller rooms only.

Shadorne Barefoot is one I am not familiar with. Those seem to add the powered subs, in fact 4 separate powered bass drivers per speaker in a small package indeed. hard to argue with that. Thanks for identifying those.

Seemingly a smaller package but would they outperform the OHM 5015? Those go for about 10K. Totally different beasts otherwise but with 4 powered bass driver per speaker could be.   They do show -3db down at 30hz in teh specs though which would seem to indicate the size is limiting them to some extent in regards to low end extension if not low end dynamics otherwise.

Barefoot MM27 with two 10 inch woofers, two 5.25" midrange and a tweeter in a compact 20.5 x 9.5 x 15.5 inches cabinet are the closet thing to what the OP claims to want. It is like a bookshelf two way but having two JL fathom 110 built into each speaker - that is four 10 inch woofers!!!

These will easily outperform Ohm Walsh and any other speaker suggested here in terms of low end response, dynamic range and overall clean extreme high SPL - they are without doubt the smallest truly full range speakers on the market.

There are some nice speaker suggestions above and Totem, for example, make great speakers, as do Ohm, but in this rather stringent requirement of smallest and full range there is a clear leader that makes other speakers that "sound big" look like kids toys.

noble100,

Thanks for those kind remarks.

Yes we are on the same page on what is best. Also with Atmasphere on the size factor.

That is why I ask the question. I prefer simple and small, not large and/or many.

Totem Mani 2 has always interested me in this regard with its unique double bass driver design in a reasonably small monitor package.

For floor standers I feel my Ohm Walsh speakers with 8" driver for smaller rooms and 12" for larger are still my personal overall sound quality benchmark in this regard. There is a newer model the 5015 that adds built in powered subs which I suspect has to push the limits as well. But I’m always looking and wondering. Plus I think its an informative discussion in general.

Mapman
Yes 20 hz and dynamic range which is why I tend to think larger drivers and speakers for that. But how small can they be?

Mapman

From my experience depends on multiple factors.

1) Appropriate room size - to allow the bass wave to happen.
2) Capable speaker design/boxes. Physics here isn’t as picky about the shape. But the box volume and tuning (pipes in the box) need to be there.
3) Appropriate amps
4- Appropriate EQ.**

Standalone subs provide you with 2 - 3 - 4. This is why audiophile subs came out of the HT and Car domains and dominate 2 channel setups now - imo.

** Meaning controllable cut off points, phase, and DB control to boost as appropriate for music between different genres, and even within the same genre.  Give this to me in a remote control from my listening position or forgetaboutit !   :^) 

Ever see pics of Fully capable speakers you know go down to 20 hz but for some reason there is a sub or two tucked away in the pic? Some problems with this picture. Well you are hardly ever shown the whole room so anyone who has been through this can understand why it is happening. Could be 1) room is too small or less likely - too big 2) speakers have wife constraints and can not be put on the room loading points 3) amps can’t deliver the goods.
3 reasons at the top of my head.

I also agree with what Tim said about the multiple sub effect and room nodes. Some all out designs go one further and place woofers at the top of the tall speaker to deal with room nodes.

Just some thoughts

Mapman,

atmasphere stated:
" The room will have some influence certainly, but if you really want 20Hz response **with any sort of dynamic range**, its not going to be a small speaker. Note emphasis."

As far as a speaker being relatively flat down to 20hz, with 'any sort of dynamic range'.  I completely agree with Ralph and I seriously doubt many even exist, certainly no small  speakers/subs.  You're chasing a ghost and I think you may know it.

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 and the single solution that has been proven to be successful in evening out and improving bass response in any room(Distributed Array Bass systems).  The room will be THE MAIN influence of how bass is perceived.   Even if your room is as big as a football field, and you have only 2 spkrs/subs along the front wall (and even if they're launching perfectly flat waves at 20hz from  these  2 points) the extremely long 20hz sound waves will reflect off of room boundaries eventually and cause peaks and nulls at specific positions in the room.  Given the exact room dimensions l x w x h and the boundary surfaces' materials, acoustical engineers can determine exactly where you will have peaks and nulls.

Sure, if the spkrs/subs and the listening position are kept in the middle of this huge space and away from room boundaries, these affects will be mitigated significantly but bass response will still not be even throughout the entire room.  The smaller your actual listening room, the more peaks and nulls will exist.  No amount of room treatments (bass traps, absorption panels and diffusing panels) or room analyzers/corrective sound processors (the ones that use microphones at the listening position for measuring and then equalizers to adjust frequencies to remedy inaccuracies like Room EQ Wizard and all the other systems built into receivers)  may be able to help a bit at 1 specific listening position but do virtually nothing for the numerous other positions in a room.  

Only multiple subs (experts say the more the better but a minimum of 3 subs) strategically positioned at setup process determined locations within a room will remedy bass peaks and nulls in a room and each room is unique since every room has different dimensions.  Trying to do this on the back-end with bass traps, panels, mics, analyzing software and corrective equalizing  (with sub locations initially selected haphazardly and literally at convenient open locations along the front wall) surprise, surprise, definitely does not work and is like trying to put out a fire with a squirt gun.....Go Figure!

  I apologize if I sound like I keep beating this horse/drum but the subject has apparently struck a nerve with me and I feel the ned to tell my story.  About 10 yrs. ago,  I  spent countless  hours experimenting with  positioning 1 and later 2 subs trying to get good bass response in my medium sized room with mixed results.  My first breakthrough occurred when I moved 1 of my 2 subs out into the room between my listening chair  and the front wall about halfway down the left wall.  I didn't know it at the time, but I had accidentally stumbled upon my own limited distributed array sub system.  Later, after months of internet research on how to achieve good home audio bass response, I discovered research white papers and articles from Dr. Earl Geddes, who has a PHD in Acoustical Sciences and currently is the  CEO of GedLee LLC which is a consulting firm that specializes in acoustics, audio, home theater and noise control.  This info concerned his research into achieving good bass response in business and home environments for both music and ht.
 I  have also learned a lot by talking and corresponding with James Romeyn of  James Romeyn Music and Audio in Utah.  James studied under Dr. Geddes for several years before opening his own company that trades in musical instruments and is a dealer for Audio Kinesis.  He is the person who convinced me to buy the Audio Kinesis DEBRA distributed Array Bass system and give it  try.

My main point is that my search for a good home audio bass system was not as simple as walking into an Audio store and buying a distributed array bass system.  It  has been more of a long journey that culminated with a satisfying discovery and excellent solution.  I'm writing this reply to illustrate that I've been at the same stage that many Audiogon members seem to be at; that is, posting on this forum searching for answers to their system bass performance woes  and seemingly believing the solution will be to just buy a certain brand and model sub, plop it down at some convenient open space along their system wall, and their system will suddenly have good bass response.

I know you have been a member here for a long time and  know, through encountering and reading many of your posts over the years, that you have a wealth of knowledge on a variety of audio subjects and have always communicated knowledgeably, articulately and conveyed relevant and helpful info in your posts.  

Precisely because of this, I was surprised you posted what you were in search of on this thread.  I thought you would understand the futility of what you were in search of. I was fairly certain that you knew very few speakers are capable of flat response down to 20 hz and the likely hood of finding a relatively small speaker/sub capable of doing so would be  approaching impossibility.

In conclusion, my current thought is that you posted your question  just to have a little fun by finding out what kinds of replies your paradoxical question would solicit.  

  Am I correct?

Thanks,
 Tim

Yes 20 hz and dynamic range which is why I tend to think larger drivers and speakers for that.   But how small can they be?     

Zu has yet to bowl me over in demos in regards to having that low end dynamic "meat on the bones" as I like to say but demos to date have been less than optimum conditions most liklely?

atmasphere
3 dB (down) at 20 Hz which is half as loud at 20 Hz
To be audibly half as loud is usually considered 6-10db on account of the ear being on a logarithmic scale.

actually decibels are already logarithmic; hearing is not on a logarithmic scale. the microphone used to measure the SPL is a listening device and measures what the human ear actually hears. 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.

Headphones are small and can go down to 20hz.  They're pretty small speakers.

3 dB at 20 Hz which is half as loud at 20 Hz

To be audibly half as loud is usually considered 6-10db on account of the ear being on a logarithmic scale.

I really mean  the speaker does not roll off much or at at all at 20hz in a typical room.  How flat it is or not will largely depend on room acoustics from there right?  If it can only be done in a smaller room fine, just say so.  

The room will have some influence certainly, but if you really want 20Hz response **with any sort of dynamic range**, its not going to be a small speaker.  Note emphasis.

^That's why speakers should be anechoic spec'd. It gives us a standard neutral base line. Now you just need to provide us with your specific criterion, so the equation can be completed.   +/- 3 dB seems to be fairly standard, though better is well, better. :-)

I really mean  the speaker does not roll off much or at at all at 20hz in a typical room.  How flat it is or not will largely depend on room acoustics from there right?  If it can only be done in a smaller room fine, just say so.  I'd expect one capable of it in a smaller room to be physically smaller than one for a larger room.

Good stuff folks, keep it coming.

noble I just want to know the small speakers capable of it in a typical room.

I’m familiar with the swarm approach. That’s probably the most effective approach in the end if done right I’d say..

30hz isn’t bad as long as the size is small accordingly. I could probably live with that. But 20hz or even lower maybe is best.

Mapman,

Even if you were to find 2 ch speakers or subs of any size that were flat down to 1hz +/- 0 dbs, the unfortunate truth is that the physics of acoustical sound wave propagation is going to ensure you don't perceive flat bass response in your room, assuming your room has walls, a floor and a ceiling. As long as your spkrs/subs are located along your front wall, there will be uneven bass response in the room; specific spots in your room that bass is exaggerated and specific spots that bass is diminished and even nonexistent.    

Sorry to rain on your parade but I've discovered there is a good solution, called a Distributed Array Bass System, that works amazingly well. These systems are sold under various names (SWARM, DEBRA, etc.).  I have used the DEBRA system for about a year now and I'm completely satisfied with the results. I started an Audiogon thread in June of this year that goes into more detail and requested input from other users (there doesn't seem to be many Audiogon users that employ this bass system).  Here's a link if you're interested: 

https://forum.audiogon.com/discussions/anybody-else-using-a-distributed-array-sub-system

You can also google "distributed bass array system" that will list multiple sources of independent info, including sites on the specifics of how it works, white papers that discuss the theories behind it with empirical data as well as current sellers of these systems.

I should mention that I was initially very skeptical due mainly to the cost ($4,000) and whether it actually worked as well as claimed.  It took months of emails and phone discussions with the seller before I decided to give it a try.  I am now very grateful I bought this system that works so exceptionally well for both my 2 ch music (especially on high-res music files that are thankfully without 'loudness wars' dynamic limitations) and HT. This system has given me solid, deep and tuneful bass that sounds equally good from all 6 seats in my 23' x 18' room.  It is somewhat expensive (I rationalized it by comparing it to the cost of 2 high-end powered subs I was previously considering) and it takes the better part of a day to properly setup in a rather detailed and extensive process.  But I now consider it a bargain and realize the extensive setup process is critical for good results.  
Lastly  a disclaimer, I have absolutely no affiliations, financial or otherwise, in the development or sales of these systems.

Just a very satisfied customer,
    Tim 
 

I thought the OP criterion was clean and flat to 20 Hz?
Perhaps he can specify what flat is to him: +/- dB ?
If the recording can contain it, and my room can contain it, I want my system to deliver it.

Transmission line makes a speaker larger.

The cabinet on Barefoot MM27 is Cabinet: 20.5 x 9.5 x 15.5 inches (521 x 241 x 394 mm)
Overall: 20.5 x 10.5 x 17.4 inches (521 x 267 x 442 mm)

it is flat to 30Hz and will play louder more cleanly than 99% of what people have here.

PMC's, which have a transmission line enclosure, can produce more bass for their size than other designs. 

Vandersteen 5a. Nipple-high at most.

I've heard Mani's and liked those very much.   I recall they had a unique bass driver design.

I'm just interesting in what smaller speakers people have found are truly good down to 20hz and if so why.

I guess they're out of production now, but a meritorious mention for the Totem Mani-2's.  Remarkable bass out of a relatively small monitor.

Atmasphere
The smaller the driver, the more excursion it needs and that's your limit. Bruce Thigpen got around that limitation with his subwoofer fan.

Atmasphere - as you probably know I am a big fan of Bruce Thigpen. I consider him a genius. Bruce' sub is unique, it allows someone to feel a helicopter land in their space at 3 hz if they want. Be prepared to replace some windows, with neighbors knocking on your door.

But even Bruce can't cheat Physics. His TRW sub is using the adjoining space next to the music room - as the box !

Mapman
You know, this 20hz - 20khz audio thing.... imo it gets thrown around like car guys say 0 - 60 mph. How much real music even exists below 30 hz anyway ? Sure, we can look at the chart data.
 
http://www.audio-issues.com/wp-content/uploads/2011/07/main_chart.jpg

But it only tells a small part of what is going on. At least on the forum discussions here. For the real answer, imo, you need to talk to each person to find out what they listen to. Some want to feel no loss in DB below 50 hz with their music. Some want it light and tight. This may be due to an apartment room, fragile kidneys, who knows...... but light and tight is not how live music sounds. 
Also
I can tell you from personal experience the guy that is 50, listening to 2 channel music, is listening to different music, and has different priorities, than my 22 year old son. Now I am managing to convert him slowly. I know this because he keeps asking me for music. But he can't afford a house or his own place. His truck is his room, and it uses two JL Audio subs. And his generation likes the bass loud - real loud. Not because he is deaf. This is because they are using the whole truck as a speaker and standing outside of it when they socialize.    

most things are spec’s +- dB so for example a speaker might be described as "flat" from 20 to 20kHz +- 3 dB. so it could be down 3 dB at 20 Hz which is half as loud at 20 Hz. No speaker is ruler flat thus when most speaker companies state their speakers are flat to 20 Hz they actually mean they are 3 dB down at 20 Hz or even -5 dB down at 20 dB or whatever.  Also if speakers are spec’s in an anechoic chamber their actual performance in a real room will usually vary considerably.

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

Mapman what is your objective here ?

Are you looking for a silver bullet, all in one speaker for 2 channel music, or are you talking about standalone subs.

Very different considerations for both. I am running rooms with both scenarios.

Cheers   


   

Not sure what you mean by "small" and "flat." Zu Definitions go flat to 16Hz. They have a 12"x12" footprint. But they are also 50" tall. AudioNote ANE has bass down to 16Hz, but I think that there is a roll-off; and they use corners to reinforce the bass.

The ohm walshes do quite well in this area. I’ve heard response with test records down to 20 hz with 8 inch ohm Walsh drivers in the past. The smaller ones I have these days are 8 inch and the larger 12 inch. One individual on the ohm thread here reported response down below 20 hz recently I recall.