Add a subwoofer?

Larger subs just have more output but not needed for normal listening volume. Unlike most on this forum I am not a rel fan. Too much cost for not enough low output imo. For myself I like very large subs. 
 

HSU gets good reviews (and measurements) but are huge. If you have the space it might be an option. Rythmic is another good buy. 
 

https://youtu.be/3LP4NomTjaM?si=-b3Tw1EuO-CAwanm

I owned a Klipsch 120SW that I bought new for $300 a few years ago. As I didn't find it particularly musical. It provided some low (29hz) sound, but it wasn't quick or tight. I gave it to my dad to use with his small 2 channel tv setup. Recently, he upgraded the stock power cord to a $90ish Wireworld and uses the Wireworld oasis RCA cable with it. That definitely brought it to life, but I'm not sure I'd still want it for a music only listening system.

Subwoofers add ambience regardless of what your towers can do. I had an interesting coversation with the tech at JL who told me that a subwoofer adds venue ambience even with a vocal only track. He had done blind tests and people preferred the subwoofer on when playing vocals... I found that interesting.

That being said, you want a subwoofer that is quick and articulate for 2 channel listening. Those usually come with a higher price tag....

I was told that the Cornwall has huge bass and I’d need a very large sub to notice a difference.

You were told wrong — the Cornwalls only go down to the mid 30Hz range, which is why you feel like you do about their bass capabilities. Especially for music you’re much better off with two subs, and as @damusicguy mentioned subs not only fill out the bass but also contribute substantially to producing a more voluminous soundstage with better imaging. Once you listen with good subs properly set up you’ll never go back — it’s that significant. I’d recommend these SVS subs as they’re very good performers, are only about 13” square yet go down to an honest 20Hz, include software to facilitate better/easier setup, and they offer a 45-day trial period including shipping both ways so absolutely no risk to try them. Plus you can get a pair of them for as little as $1149 (depending on finish), which is simply a no brainer to me to at least try. I’d bet big bucks you would not be returning them. Hope this helps, and best of luck.

https://www.svsound.com/products/sb-1000-pro-subwoofer

I would add an active crossover to what ever sub you choose. It is as important as the sub (more so IMO). 
 

this apologue model from Sublime acoustics is only $600. I use the K235 that adds balanced inputs/outputs for $1,100 but the units are 95% the same. In my system (McIntosh/JBL 4367) is it transparent with no loss of detail to my ear and no added hiss. 
 

https://sublimeacoustic.com/products/k231-stereo-3-way-active-crossover

james633,

This is what I use to convert my speaker level to balance for use with my JL Subs. The JL subs have an excellent internal calibration for the room placement.

SP-2SX | Jensen Transformers (jensen-transformers.com)

ozzy

If you just want a little more bass, but don't have much money, how about adding a simple Schiit Lokius to add a bit more umph down low?  2 of the lowest bands are at 20Hz and 120Hz so feathering in those controls to taste should give you what you want.

You might want to consider a mighty 8” wonder from B&W, the ASW608. In the video below a gentleman tells of how well the ASW608 blended with his Cornwalls.

I don’t have Cornwalls but I decided to try them in my system. I added two and they are excellent. B&W provides some very good basic DSP options on it for ease of blending with your speakers. They are small, unobtrusive and made well. For an idea of how they look check out my system pictures.

Adding the subs has been the best thing I have done for my system.

Cheers,

Scott

https://www.youtube.com/watch?v=n7YtBFD473U&t=3s

In your case adding a subwoofer is a bad idea. To improve the sound quality you would need to add two 15” subs and a two way crossover. This is much more than you wish to spend. One sub will not keep up with your Cornwalls.

To improve the sound quality you would need to add two 15” subs and a two way crossover.

I disagree with this completely.  You don’t need 15” subs as even 12” subs will be more than adequate in your situation, and using the adjustments on a good sub and proper setup will be more than fine without an external 2-way crossover.  Could it possibly be better with bigger subs and an external crossover?  Yeah, but at much higher cost but you’ll still get very significant performance improvements without those things and to say otherwise is really just silly talk IMHO.  Try the SVS subs risk free as I suggested above and you’ll see just how much benefit you can get for relatively not much $$$.

I have owned Cornwall IVs and LaScala IIs. It is true that you need a big(er) sub to keep up with the 15” drivers. Although I ended up going with HSU,  the owner of Rhythmik steered me away from a pair of 12” subs. I bought a pair of ULS 15 II subs that paired well with both horn speakers.

I second the HSU's. Good value for dollars spent. Take a visit to their website.

The also answer their phone and talk to you.

Great info.  Thanks to everyone.  This will be a journey.  And moving furniture a bit I’m sure. Very cool stuff 

Subs always help unless they aren't set up right.  It sounds like you want to do it right, which means filling in low end information that the speakers can't reproduce.

While the Cornwalls are very efficient, it's not going to be hard to "keep up" with them as some others have said.  I have Klipsch Chorus and Quartets.  I have a Rythmik F15 with the Chorus and the volume level is barely on. 

You could easily get by with a moderately powered 12" sealed sub.  My first recommendation would be Rythmik, but SVS has some very affordable models that would work.  Two subs are better than one, and 12" sealed subs don't take up much space and would be much better than getting a single 15" sub. 

If you want to pressurize the room and feel your bowels shake, you'll need to step things up, but if you just want to fill in the bottom end, you'll be fine with one or two small subs.

@soix You obviously are not familiar with Cornwalls which are capable of prodigious output. They will swamp two 12" drivers. 

I many systems subwoofers do more harm than good. If the OP is a critical listener and continues along the path he is on he will be very disappointed.

You obviously are not familiar with Cornwalls which are capable of prodigious output. They will swamp two 12" drivers. I many systems subwoofers do more harm than good. If the OP is a critical listener and continues along the path he is on he will be very disappointed.

@mijostyn First, the OP has already said he’s not satisfied with the bass he’s getting and is looking for improvement, so clearly their bass output is not all that prodigious in his room. Second, there’s no way a pair of 12” subs that go down to 20Hz -3dB will not add meaningful information that the Cornwalls are simply not physically capable of — that the subs’ drivers are not 15” is determinative of nothing.  And third, he can try the SVS subs with absolutely no risk, and I’d bet big $$$ he would not be disappointed and would not return them.  There are precious few speakers (if any) that wouldn’t get at least some benefit from adding two good 12” subs just to better manage in-room bass issues if nothing else, and the Cornwalls are not “magic speakers” that somehow defy physics and logic.

@soix Hey, I am all in favor of subwoofers and SVS makes a high value 15" subwoofer. The Cornwalls go very loud, just not very deep. The deep has to go as loud as the not so deep. A Pair of 12" drivers will have to work too hard to keep up creating more distortion. Cornwalls require 2 15" drivers or 4 12" drivers. I use 8 12" drivers and my system does not go near as loud as Cornwalls. The reason I use 12" drivers is to keep the size of the enclosure down. Each enclosure gets two drivers. The amount of gain required to give you the visceral experience of a live performance is formidable. 

I use a Rythmic 15 in sealed sub. I high pass the mains at 50 Hz and set the sub crossover to 50 Hz. May old ProAc monitors are "rated" to 27 Hz at  -3db. The integration is seamless and the bass is tight and "musical." IME it is challenging to integrate a sub w/o high passing the mains. The Rythmic gives you a lot of control including a parametric EQ. If you have the $$ two may be great with your Cornwalls. 

@george53 You have a pretty big room so I would suggest no smaller then a 12" and probably two. You haven't mention how you have the room layout and any room treatment. Integration is the key if you know how to mange it.

Thanks to all who offered their thoughts on this.  I went with one SVS SB 1000.  Easy to tinker with settings through the app.  Huge positive change in my system.  I can see where 2 would be peachy, but down the road maybe.   Don’t think I could go back from this.   Kind of magic .  Box disappears but music gets bigger.  I felt compelled to post this, as I’ve read posts/questions here, with no follow up and I wonder how things turned out.  So thanks for the encouragement.

Why not?????

Thanks to all who offered their thoughts on this. I went with one SVS SB 1000. Easy to tinker with settings through the app. Huge positive change in my system. I can see where 2 would be peachy, but down the road maybe. Don’t think I could go back from this. Kind of magic . Box disappears but music gets bigger.

YES! Exactly!!! This is what a good sub(s) can do. It offers SO MUCH more than just more bass. Add another sub and you’ll be equally amazed at what it can do. Subs add ambiance and have presence we can’t know until we get a good one and properly set up it up. Turn the sub off and the music and soundstage just shrinks. It’s amazing. Those who don’t try will never know the difference. Goodonya!!!

Yes!!! That’s the word I’ve searched for.  PRESENCE.  Thanks. 

I don't think there's any doubt a well integrated sub is a wonderful addition.  The problem is usually the work needed to integrate a sub well.  For a novice, success can seem random, and often frustrating. 

soix,

"It offers SO MUCH more than just more bass. Add another sub and you’ll be equally amazed at what it can do. Subs add ambiance and have presence we can’t know until we get a good one and properly set up it up. Turn the sub off and the music and soundstage just shrinks." I couldn't agree more with your post. I often tell people that adding subs isn't just about bass and I believe most systems benefit from "properly" setup subs. I always say, I can't hear my subs, until I turn them off.