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

sorry 56.5ft typo

http://www.stereophile.com/content/thiel-cs35-loudspeaker-specifications#4SSuUmxSowLoD8Ce.97
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What are the smallest speakers that are clean and flat down to 20hz?

Also what bass driver or drivers do they use?

Thanks.
mapman

Without being EQ'ed the lowest bass I have heard from a large sized bookshelf, has been a pair of Sonus Faber Extremas, that have an ABR using a Kef B139 with voice coil for switched resistive damping to tune to the room, with a pair of Krell 250 monoblocks up them.

Cheers George 

Yg Acoustics Kipod II Signature. Bass is covered by only an 8" driver in active sealed inclosure.  Deep, deep bass. 

The Excellent Deavialet Phantom is that type of speaker yhat can place with grace 
Or knock or thump you in the chest 20hz test tones confirmed . my brother bought a pair of yhe easy release models from last year thin 2- 6inch pistons in a automobile  like a Ducati twin engine horizontally apposed and and unit is only as big as a soccer ball but can knock out the sound pressures !!

Kii audio model 3s. 

Check out Gershman Acoustics Avante Garde. Gets to 20hz or close and is not large at all.

Physics can be a pesky thing, and the mutually exclusive nature of including "small" and "clean at 20 hz" in this post does seem a little paradoxical. I use 2 RELs in my hifi rig and they're sort of smallish I suppose, as are the drivers in my Silverline Preludes (3.75" woofers)…I have a 92 lb 500 watt Mackie studio specific sub (in my studio specific studio) with 2 12s (active and passive) that supposedly does 19hz…but it's on the large side. So, no free lunch. 20hz…hmmm…large Wilsons maybe?

Barefoot Monitors are probably the smallest high performance speakers.

The MM27 has the smallest footprint and can compete with speakers many times their size.

Headphones!

Grado made a line source array that they showed at CES one year, just for fun. It made decent bass but it had a lot of drivers in it. Seems to me it was over 6 feet tall and they won't be manufacturing it.

Otherwise you're simply going to have to have a big speaker.  My speakers go to 20Hz and have two 15" woofers. You probably can do it with one. The smaller the driver, the more excursion it needs and that's your limit. Bruce Thigpen got around that limitation with his subwoofer fan.

Click on the link below and then products (TRW-17):

http://www.eminent-tech.com/main.html

From the page:

A conventional speaker cones displacement must increase four times for each halving of frequency to maintain the same output. This is why conventional cone woofer companies are trying to develop “long throw” woofers. Although inefficient, cone woofers work fine above 40Hz. Below 40Hz however cone woofers quickly run out of travel and the output diminishes rapidly.

I would consider looking at the DIY site from Troels Gravesen. Lots of his kits show the speaker response and the room response, followed by the final outcome.  You could find it illuminating.

http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm

Best,


Erik

Clearly larger active or powered speakers or speakers with integrated powered subwoofers are best able to do it but I’m wondering more about purely passive speakers even if only in a smaller room.  I realize room acoustics play a big part.   I'm also wondering more about low end extension and  distortion levels assuming other external factors will need adjustment for truly flat response. 

FYI, there’s a rule of thumb, that for any given driver, going down an octave causes 10x the linear cone travel. So, if you attempt 20 Hz with a 6" driver you’ll need it to move a foot back and forth or something ridiculous like that. :)

This is why larger is better. Those who argue they are slow or not musical have not been able to integrate them properly which has nothing to do with the quality of the driver but not managing the room acoustics and EQ properly.

You may also find this resource helpful:

http://bass-db.gforge.inria.fr/BASS-dB/

Also look for Room EQ Wizard where you fill find many bass geeks to discuss things with you.

Having adequate drivers for a subwoofer is very important, but to my ears, the quality of the EQ matters much much more. So, JL to me is one of the best off-the-shelf subwoofer makers. Of course they use a high quality sub driver, but their auto-EQ is perfect.

Personally, I do my own EQ, so I’m quite happy with Hsu VTF-15H MK II for $1,300 (including EQ). If I had all sorts of money and no time, I’d go with JL.

Best,


Erik

Hi Mapman,

Clean and flat = big driver. Best I've had is a 15" Hsu which was flat to 16 Hz after acoustic treatments and EQ.

However, it's really important to understand, below 400 Hz or so, your room becomes a very important part of "clean and flat" so much so that getting to the lowest octave is a completely different ballgame. The lower you try to go the bigger the dragons. This is why smaller 2 way speakers are often preferred to full-range.

It can be done and it's glorious, but it's not trivial. If you aren't willing to spend the time or hire qualified help, you are often much better off with limited output speakers.

Best,


Erik

How clean and at what SPL?  

Very few speakers of any size (that I know of) maintain clean output (call it 10% THD) at 20hz at 90 db.  If you really want that kind of performance from a small speaker, you'll almost certainly need a subwoofer.  

Some people might argue that 30%+ THD is clean enough at 20hz (where hearing is very insensitive).   That may be true, but it means that any answer to your question will be awfully subjective (and you'll still probably need a subwoofer).