There's a lot more bass in a 6.5" driver than most of you think

Reminds me of a debate between Paul Klipsch and Edgar Villchur at a national meeting of the Acoustical Society in NYC during which Klipsch said something like "I don’t care if you push it with a broom, you still have to move the air" arguing radiating surface v excursion.

In the process of setting up my subs I was surprised that the display revealed the in-room response of my KEF Reference 1s extended to 30 Hz before dropping sharply. I supplement them with a pair of Velodyne HGS-15s crossed 4th order at 40 Hz.

I have a highly-damped bedroom with a pair of (terrible?) inexpensive speakers with 6 in. woofers (vented). The highs aren't great I'll admit -
as in not very smooth. THAT is the real challenge- the upper mids and higher frequencies never sound "just right" without some major technological effort (and the associated expense). But the bass coming out of my cheap speakers is remarkable. Jazz bass is very clear, and pipe organ is pretty good as well. In the "other room" I have a very large pair of speakers with built-in powered 15in. subs, so I think after 30 years of listening and upgrading I know what bass is by now. I agree- an 8 inch (or larger) driver is quite a bit better, but your room and your choice of music will either make your listening a relaxing experience, or you'll be reading "Magico reviews" and saving up for the day you can afford a pair. IMO outboard Subs are for movies anyway, unless your room is enormous. 

french_fries:" IMO outboard Subs are for movies anyway, unless your room is enormous."

Hello french_fries,

       I suggest that your belief that outboard subs are only for movies, is a very clear indication that you've never heard a high quality 2-channel music system with well integrated subs or that you lack the knowledge to properly implement subs seamlessly into your own system, perhaps both?
      My intent is not to overly offend you, my intent is to suggest that you may not be aware of what you're missing.  It's been my experience that  the main characteristics that differentiates listening in person to music played live (I'm referring mainly to a smaller type settings and not to large arena type settings) and listening to music on most home audio systems, are the the accurate, detailed and highly dynamic reproduction of the bottom 2 octaves of deep bass (about 20-32 Hz)that is experienced as being felt as well as heard.
     Sure, the bass can still be perceived as very good without the bottom 2 octaves but it's not the same powerful, dynamic experience that is felt as well as heard and closely resembles the deep bass of music heard live and in person. 
     There's also the issue of, even if one utilizes large main speakers with large woofers (or even multiple large woofers) and the speakers are rated as having accurate deep bass extension down to about 20 Hz, this does not mean this deep bass is necessarily perceived at your designated listening seat.  This is due to what I mentioned earlier in this thread; 
basically that the main speakers are precisely placed in the room with the midrange/treble transducers positioned in relation to the listening seat for very good midrange, treble and imaging performance.  The major problem is that the woofers are affixed in place in the same cabinet, typically below the midrange/treble speakers, and cannot be independently positioned in the room and in relation to the listening seat which is required to optimize bass performance at the listening seat. 
      It's highly unlikely that the optimum performance room positions for the main speakers' midrange/treble and bass drivers, in relation to the listening seat, all just happen to be at the same exact floor spot in the room, with all speakers vertically aligned in the main speakers' cabinets. Outboard subs, being capable of being independently placed in the room and in relation to the listening seat, are ideal solutions for attaining high quality bass response performance at the listening seat.   
     Using large speakers with large woofers and the midrange/treble drivers in the same cabinets, there's no guarantee that room bass modes (causing bass peaks, dips and nulls) won't exist at the listening seat. Outboard, independently and properly positioned subs will guarantee there are no bass modes at the listening seat.  
      French fries, if you'd like I can describe exactly how to utilize 2 subs in your system/room to attain very powerful, dynamic, detailed, fast, smooth and natural bass performance at your listening seat that integrates seamlessly with whatever main speakers you have.  If you're open to using 3 or more subs, I can describe how to get near sota bass performance throughout your entire room, not just at your listening seat.

Let me know,
      Tim

’Cutting Edge Design’ starting with your existing 6" drivers.

look at the directional pair of monster woofers at the bottom of these 22k beauties:

https://www.audiogon.com/listings/lis9i01e-evolution-acoustics-mm2-full-range?utm_campaign=Saturday_Email_20200125&utm_content=saturday_email_20200125&utm_medium=email&utm_source=zaius

Your existing mains, (6" driver or two): Probably in cabinets or stands to get the tweeter at seated ear height. No way to get a directional pair of woofers matched with their l/r origin.

Cut your tall enclosure, reseal the bottom, put it on a self powered sub-woofer, same l/r. Or, toss the stands, put them on the pair of sub-woofers.

Of course you need to figure out vibrational connection/isolation, but that’s easy isn’t it. Hah.

Mains with tall cabinets ’shortened’ will have less volume, BUT, the 6" no longer trying to produce bass, so, larger volume, or disruptive or non-directional port not needed.

As I Punned, ’Cutting Edge Design’.

In Chicago audio show (2016) I have heard, rather small tower speaker, from Penaudio (Serenade) with two 6" woofer, and it was unbelievable bass !