There is no denying the thump the LS50W Active Music System is capable of producing, even in a larger room, but for those of you who want just a little more bottom end, the LS50W app has some options.


The -6dB (85dB/1m) frequency range for the LS50W is spec’d to 40 Hz (More), 43 Hz (Standard) and 46 Hz (Less). For enclosures that are basically 12” x 8” x 12” that’s a pretty amazing low-end. 


The LS50W bass response is spec’d to 45 Hz (More), 50 Hz (Standard) and 61 Hz (Less). This is measured as the point at which the response curve attenuates by -3dB from the otherwise relative flat curve. With musical genres like chamber music and most popular music that have natural drums and bass (think everything from the Beatles to The Strokes) there’s not a lot of musical information below 50 Hz. For modern pop, classical symphony and electronic music, a subwoofer may be necessary. However, there is also the matter of quality of bass reproduction as opposed to the quantity of bass reproduction. For music, it’s preferable to have an enclosure that is tight, quick and responsive so the trade-off is depth of bass in order to produce accurate bass. Try out the LS50W without a subwoofer first to see if you think one is necessary.KEF KUBE-2


If you find that a subwoofer is necessary for you to get the most enjoyment from your music, the LS50W has a standard RCA-type subwoofer output for super easy connection to an external subwoofer (we recommend the KUBE-2).


In addition to the subwoofer out, the LS50W app also does a couple of other things to make subwoofer integration simple and optimal.


Bass Extension

There are three settings (Less, Standard and More). Experiment with the setting that sounds best. In a small room you may want to attenuate the bass somewhat by using the Less setting, but before you add a subwoofer, check out the More setting and see how that works for you. Now would be a good time to tell you that in the More setting the bass response of your LS50W approaches the performance of our Reference 1!


High-Pass Mode

The High-Pass Mode allows you to set the bottom end of the frequencies sent to the LS50W Uni-Q drivers. For example, if you set the high-pass filter to 80 Hz, frequencies above 80 Hz will go to the LS50W Uni-Qs and frequencies below 80Hz will go to your external subwoofer. The range is 50 Hz to 120 Hz.


Sub-Out Low-Pass Frequency

This setting allows you to set the frequencies sent to your external subwoofer via the sub-out connection. The range is 40 Hz to 250 Hz and the default setting is 80 Hz. Experiment with you speakers, subwoofer and room to find the best low-pass filter setting for your taste.


Sub Gain

This allows a 20dB swing (-10dB to 10dB) in output gain from the LS50W. It’s always best to run your subwoofer amp as wide-open (full gain) as possible and control the actual output gain of the subwoofer via the upstream device, which in this case is the LS50W app.


Sub Polarity

Nothing kills bass response faster than an out-of-phase subwoofer. Basically, you want your subwoofer driver and mid-range driver to be going in the same direction at the same time (e.g. mid-range driver is pushing out at the same time the subwoofer driver is pushing out). If one is pushing in while the other is pushing out frequencies will get canceled and this cancellation is most noticeable in the bass range.


The best way to visualize sub polarity is to think of a setup where the subwoofer is placed behind the listener facing the front speakers. While the front speakers are pushing out, if the sub is in the same polarity the sub will be pushing out and this will cause cancellations. In this setup you would put the subwoofer out of phase so that it was pushing in at the same time the front speakers were pushing out.