More Power or use subwoofer to boost bass for music

To enhance bass you need to try to position the speakers closer to walls to amplify the lower bass, or add subwoofers. The answer is not adding multiple subs or adding bass absorption. The rational approach is to start with proper imaging using a method such as The Master Set. Imaging is key to proper sound from a stereo source. Once the imaging is perfect you can then add subwoofers for the lowest frequencies if you want more bass. It may help to use a computer and microphone to real time analyze the frequencies in your room. Then you will know how far down your speakers go. If you want 20 Hz or below you will need subwoofers. They are tricky but to get 20 Hz and below you have to move air. Lots of air. You will need 15” woofers. The idea of a “swarm” of subs is based on evening out the nodes. It’s an admirable goal but rarely practical. One well placed sub is good but not easy or perfect. Two well placed subs are better but beyond that you are spending a lot to get a little. Like horsepower. Look up Harman Kardon white paper on sub placement. Seminal work. Proper placement of stereo speakers doesn’t necessarily mean the proper placement for bass or subs. I recommend Hsu Research or SVS for affordable well made subs. That way You can afford two or three. Hsu sells pairs of identical subs. Best of luck and keep us posted. 

Hello cool,

     Millercarbon is correct, a 4-sub distributed bass array (DBA) will provide excellent bass performance throughout your entire room and integrate seamlessly with your main B&W speakers.
     If you’re only concerned with attaining excellent bass performance at a single designated listening seat, however, using 2 good quality subs will will work about just as well as a 4-sub DBA.  You may even be able to attain very good bass performance at a single listening seat with a single higher quality, and more expensive, sub that comes with a mic and has room correction software.   You would first optimally position the single sub in your room using the crawl method (you can google it) and then utilize the room correction function to fine tune the results.
     2 subs, even if they’re smaller and less expensive, will generally perform about twice as a single sub, even if it’s larger and more expensive. The benefits of using 2 subs are increased bass power and dynamics when the music calls for it, neither sub is operating near its limits and the bass will be better integrated with your main speakers.     Whatever sub or subs you decide to use, it’s very important that each sub has separate controls for Volume, crossover frequency and continuously variable phase.  These controls are critically important for adjusting them optimally to your room and system.  It’s also beneficial for the subs to have the choice of inputs, rca line level and high level speaker wire.       You’ll also notice an improved soundstage and improved midrange and treble performance of your main speakers utilizing 2 subs.
     I suggest trying a pair of SVS SB-1000 subs or similar Hsu subs for about $1,000/pair.

Good luck,
    Tim

xcool OP

The combined impedance and -phase angle graph shows these 804’s are a hard load in the bass from 60hz to 150hz where all the power is needed
https://www.stereophile.com/images/913B804fig1.jpg
Yet the frequency response shows that they have a slight rise in that area, and should give big bass if driven well. https://www.stereophile.com/images/913B804fig4.jpg

The second page of the Stereophile review often complains about the lack of bass from the 804 D’s. And looking at what they drive them with, it was the same amp as you a 3 channel HT Parasound A31 that has trouble doulbing wattage from 8 to 4ohms, let alone down to 2ohms
https://www.stereophile.com/content/bowers-amp-wilkins-804-diamond-loudspeaker-page-2

I think your amp just like the reviewers, is not up to driving the bass with good current delivery, try something that can, and you then won’t need any subwoofers and the problems they bring to seamlessly blend in to the mains.

Cheers George

Thanks George.   Thanks for the information on Parasound A31.   That is good to know.   Maybe I do need more power to drive those B&W.   I'll checkout the review.

Also, many thanks to others for information on room treatment and multiple subwoofers.    One thing I should have mentioned in my original post, is that I live in an apartment, not small, but average size.  I don't have a lot of options to accommodate multiple subwoofers.   I actually do have a subwoofer now.  It's a very old Def Tech subwoofer from the 90's.   It doesn't have a whole lot of connection options.   I only use it for movies.  I was looking to replace that anyway.   

I do like the option of adding some acoustic panels, and will look into that further.

Thanks!

xcool OP Just found proper test on the A31 as I thought not much current ability into low impedances. The 4ohm wattage should be a lot higher, and they didn’t do the 2ohm as it would have been trouble (bang maybe). Not the amp for these speakers.

 Cheers George

BHK Labs Measurements: Parasound Halo A31 Three-Channel Amplifier

1% THD 232.8W @ 8 ohms, 352.0W @ 4 ohms

10%THD 285.0W @ 8 ohms, 422.9W @ 4 ohms