Subwoofer Recommendations

I am looking for a single subwoofer that will compliment my JBL L100 Classic speakers.  This is my office system and I only want 1 subwoofer (no swarm) to add a little oomph below 50hz.  I will be using it with my McIntosh MA6600 on the second set of variable line outs.  The sub has to accept line in, have a phase control, level control  and adjustable crossover so I can cross it over under 80hz or so.  I will be still running my JBL speakers full range.  Price is up to $1500.00 new or used although keeping it at around a grand would be great.  This is the only way I will hook up the sub and I would like something that does go deep.  I know there are probably hundreds of subwoofer threads but I have never looked at them.  This is just something I came up with today so any help would be appreciated.
Small footprint which is fine in an office.
Can be placed along the wall
( I ordered one )

Thank you for responding but I don’t think the Kef will work with a couple of 6 inch woofers. Doubtful the bass would go low and deep enough. The JBL speakers have 12 inch woofers, I would think I would need at least an 8 inch woofer as minimum but not sure.
Given your requirements, I would look at Hsu subwoofers.
You should be able to find them used and even new, they are very reasonably priced and work well.
I am using a pair with my Vandy VLR's and find them easy to set up and enjoy.
I think you’re making a mistake going with only one sub with your budget as two subs yields much better bass integration and performance.  For $1500 you can get two SVS SB2000 Pros that go down to 19Hz and include integration electronics, or you can cheap out and get a pair of SB1000s for $950 that’ll still get you down to 24Hz.  Even if you start with one, if I was you I’d eventually get a second.  BTW, SVS offers an extremely generous risk-free trial period that includes shipping, so if two subs aren’t a significant improvement you can always just return one.  Anyway, that’s what I’d do FWIW.  Best of luck. 
I have owned this JL AUDIO D110 and I think it will fit the bill. It does not have a high pass filter if that is important to you. The JBLs will run full range. I’ve owned many subs and I thought this one was outstanding!
The  Kef KC62 has two 6.5 inches drivers.
I thought it was like a one   10 or 12 inches driver.
Now I think this is not the way it works.
You want low bass but have specifically ruled out the one most economical way of getting it. You will now proceed to spend more, probably even taking up more space, than the one method that will actually produce the low bass you want. Oh well.

Own goal is hard to image. So I go with
@maxwave, to an extent that is how it works ... the area of a driver (circular) increases exponentially with radius but a greater linear displacement also helps to generate bass at low frequencies.
The cone shape is also a factor.
One > two drivers double cone area and add to symmetry (power output).
Two > balances internal energy.
If you get hung up on 'driver envy' consider the fact that @ 40 Hz the wavelength is 8.6 M or about the same dimension of an interior wall (large room).
@stereo5, sealed enclosures have relatively good output response and if 
given good power will perform very well.
KEF produces extreme HiFi Gear and I personally would not hesitate to trust in the engineering some.
A single sub is smart ... not a mistake.
+1 @nonoise, good review article btw.
+1 @ozzy, Hsu is also very good and possibly a more affordable model.
How did you decide between the sealed vs ported sub on the SB2000?
The main reason was you were only looking for one sub so thought space may be a consideration and two SBs are a lot smaller than two PBs while still getting you under 20Hz (-3dB).  The other is I tend to prefer using a sealed sub for music, but I understand properly-designed ported subs can work as well.  Last, I own an SB2000 I use for HT and it alone can shake my living room when required so two PB2000s seems almost like overkill for music purposes.  So that’s where I was coming from with my recommendation. 

I have two SVS SB 2000’s, as I listen mostly to music.  The ported SP 2000’s provide more boom and were noted to be better in a home theater for movies. 
@stereo5 , you will a 12" sub to produce anything useful below 50 Hz. Just a caution, bass travels...far. When my system is on playing something with a lot of information below 30 Hz things on the opposite side of the house rattle and buzz like crazy. This may cause trouble in an office environment.
I recommend one of the REL subs. They will blend in very well with your JBL L100 Classic speakers.
Take a look at Rythmik’s F15HP, a lot of bang for the buck. If you want to keep things closer to $1K, the F12SE. While I use 4 subs in my main system, unless you’re planning to really rock out while you’re working or have a huge office, I don’t think you need 2 or 4 subs in an office. If you just want to add in some low level information that your main speakers can’t provide, a single sub can work fine in a smaller room. I have 3 smaller systems, each with a single sub (all are sealed subs) and they all sound great for their purpose.
Totally disagree that a 12” is needed for meaning output below 50Hz. Many 8” and 10” options would be suitable for your situation as well. If you’re looking for subterranean bass then sure look at bigger subs. But to blend with the JBLs below 50Hz or so for music, smaller subs could work quite well. I think most people would be shocked by the KEF KC62s performance and it likely would be a great option. I think the REL T7 or T9 options would be a great match too. I personally use a JL Audio E110 and it will shake my entire room if I want it too. No trouble with output from that 10” at all.  And it has a wonderful onboard active crossover along with continuously variable phase control to make blending with the speakers much easier.  Fantastic sub.
How about a MartinLogan 1100x?  Downward or front firing, ARC makes tuning a breeze and the bluetooth app makes fine tuning from you chair child's play.  I'm running one with Heresy IV's with the crossover @ 58hz with ARC on and you cannot even tell where it is.  
cant' tell you how many times I've read audiophiles convert from 40Hz to 80 Hz and be amazed at how good it sounds. 
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Thank you to everyone with some really good ideas.   Today I ordered a SVS SB2000 Pro  12 inch subwoofer.  I should have it within a week and will post about it at that time.  I also ordered a cable from Blue Jeans to go from the output 2 on my integrated to the sub.  I think this will work out fine. 
You need 2 subs to integrate the sound.  I use REL and am super happy with them.  They compliment my main speakers.  Other brands mentioned here are good as well.

I am starting with one sub and if I feel it isn’t enough, I will get another.   

I am starting with one sub and if I feel it isn’t enough, I will get another.  
Couple of things, I also just got an SB2000 pro
reason being its small, app 14" x 14" and a 12" driver with good response.

I run a distributed base setup 3 subs in a well treated room for 
music only, got tired of rebuilding the failure prone plate amps
so pu a new SB 2000 pro, good specs and it works very well.
The app negates the need for a flashlight and looking at things upside down so a plus.

Regarding 1 sub in a room well it depends on the room as to
just how things will work out and naturally your expectations.

I think I'm now a the point in my room where the bass is tight
balanced without much in the way of room modes.

I should add that even in my treated room I use a very simple DSP sub program to decrease inevitable room mode peaks
and that did the trick. 

Good luck 


SVS is the best audio company I've ever dealt with, bar none. As I've said elsewhere, when one of my 1000s went on the blink after five years of service, SVS replaced the electronics for $35 shipping. The sub was up and running 20 minutes after the replacement guts arrived. Great company.
maxwave KEF  KC62
Small footprint which is fine in an office.
Can be placed along the wall
( I ordered one )
Maxwave, the KEF KC62 is an interesting subwoofer system. The design and manufacturing is stunningly innovative and its equipped with what appears to be some unusual but said to be useful settings options.
The word is it plays much larger than its size.

When you've settled in I hope you'll share your sub history and your thoughts.
All the best.   
I received my SVS 2000 Pro ported subwoofer at the beginning of the week.  I had to wait a couple of days to use it as I was waiting for my Blue Jeans cable to arrive.  Once I had it hooked up, I used the SVS app which allowed me to make many adjustments.  I am sure there are more to come.  For now, I settled at 100hz crossover at a 24db per octave slope.  I have the saub volume at -12, phase at 0 and everything seems to have blended well without calling attention to the sub.

I haven't touched the parametric Equalizer  portion of the app yet but I will once everything breaks in nicely.  So far I am pleased with the sound.  I wasn't pleased with SVS though as I bought a new sealed unit which came without the power cord, the quick start guide and the grill had 2 broken pegs so it won't stay on..  A quick call to customer service has those items shipping out on Monday. 

I did question if I was sent a repack but was assured it was a brand new unit.  Does seem suspicious that the 3 items were missing and 2 grill pegs were broken though.