KRK’s S10.4 powered studio subwoofer is built around a 10‑inch woofer utilising the company’s distinctive yellow glass‑aramid woven cone material. Power comes from a 160W Class‑D power amplifier with automatic mains voltage selection, and there are four switchable crossover filter options (60Hz, 70Hz, 80Hz or 90Hz) so that the sub can be matched to other monitors, not just KRK’s own models. KRK suggest that for use with smaller monitors, start with the highest frequency setting and then adjust to a lower setting if required. For larger monitors, the third or fourth position is recommended. A bypass control jack, which can be operated via an optional footswitch, routes full‑range audio to the main monitors while disabling the sub. The manual includes useful information on setting up the subwoofer and on matching it to the monitors being used with it.
Housed in a reinforced, front‑ported MDF enclosure with rounded edges and finished in a black‑vinyl wrap, the S10.4 measures 341 x 479 x 310mm and weighs in at 15.88kg. The driver faces forward and there’s no grille protection, so you need to place the sub where you aren’t going to put your foot through it. The vertical port slot shape is engineered to reduce turbulence.
There’s plenty of power on hand for small and medium studios, with a maximum SPL of 117.2dB and a low‑frequency reach down to 30Hz. All the connections are made on the rear panel, where there’s a choice of XLR, quarter‑inch TRS jack, and RCA phono connectors for both the inputs and the outputs (to feed active monitors or an amplifier in the case of passive monitors). There’s a polarity switch and a ground‑lift switch, and a rotary control sets the volume. Below this is the four‑way rotary switch to select the crossover frequency. There are also two switchable input sensitivity settings to accommodate studio or consumer levels, and a standby switch. Power comes in on the usual IEC connector with a rocker power switch above it, and the power LED shows green when the sub is active or orange in standby mode.
Bringing in the KRK S10.4 filled out the bottom octave in a very natural, clean‑sounding manner without having any detrimental effect on the stereo imaging.
Evaluating the effectiveness of a subwoofer is always somewhat subjective as its placement and the acoustics of the room in which it is operating have a significant influence on the end result. In my own studio I found placing the sub just off centre between the two monitors gave reasonably consistent results. In terms of level, I’d recommend setting the sub so that you miss it if it is turned off but at the same time its presence isn’t too obvious when it is running — if you add too much it might sound impressive but your mixes won’t be accurate; the purpose of a sub is not to make the bass louder but simply to extend its frequency range downwards. My 8‑inch studio monitors have a pretty decent bass response anyway, but bringing in the KRK S10.4 filled out the bottom octave in a very natural, clean‑sounding manner without having any detrimental effect on the stereo imaging. Being able to bypass the sub and to hear the main monitors without the sub’s high‑pass filtering is also very useful, so buying a footswitch for this purpose is a good investment.
In a typical home studio, there’s more than enough level on hand here to keep pace with most nearfield monitors in the 5‑ to 8‑inch range, and while I wouldn’t normally recommend a sub for use in very small rooms, especially those with imperfect acoustics, at least this gives you the option of moving the sub to find the location that delivers the most even bass response, even if your main monitors have their placement dictated by the room layout. Should you have small monitors in a small room, then it may be worth looking at the smaller KRK S8.4. On the other hand, if you are working in a larger space with bigger monitors, then look at the KRK S12.4 or KRK 12sHO.