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How To Choose A Subwoofer
How low can you go? 


by Phil O'Keefe



Ever thought about adding a subwoofer to your studio monitoring system? A lot of people can benefit from a sub in a variety of ways, but hesitate to add one due to acoustical concerns or just not knowing where to start. Sure, if the company who makes your monitors offers a matching subwoofer that is designed to pair with them you have at least some point from which to start in your subwoofer search, but how do you know if it's the right match for your needs? How big of a sub do you need to best match up with various sized monitor speakers?





What can a sub do for you?

Let's take a look at some of the reasons you might want to consider adding a subwoofer to begin with.

  • They can increase the range of frequencies your monitoring system can reproduce, making it easier to hear what is happening in the lowest octaves of your mixes.

  • They can be impressive to clients. After all, while we engineers are concerned with accuracy, some clients just want to hear it bump!

  • A sub can be great for simulating what your mixes will sound like at a Rave or in a dance club.

  • A sub as part of a surround monitoring system, in partnership with a suitable multi-output audio interface will allow you to explore the world of surround sound mixing.

  • They're fun!



Do you need a subwoofer?

Not everyone needs a subwoofer. If you work primarily on dialog editing, a subwoofer is going to have little appeal for you, but others will have far greater use for one. Here are some questions that may help you decide if you should consider adding a sub to your monitoring setup.

  • Are you working on Dance, Electronica, EDM or similar genres that place a lot of emphasis on the low end of the frequency spectrum?

  • Do you have smaller nearfield monitors with relatively limited low frequency response?

  • Are you working on film scoring projects or video soundtrack or corporate A/V projects? These will oftentimes have sound effects with considerable low frequency content that may benefit from being played back through subwoofers.

  • Do you work in 5.1 surround, or would you like to explore surround mixing? If so, a sub is essential.

  • Do you have a hard time hearing what is going on in the low frequency range of your mixes? Do you have a hard time differentiating the kick drum and the bass? If so, a sub may be able to help you.



How big of a sub do I need?

For this, let's compare three different sized subwoofers. Since Harmony Central is a Gibson Brand, I was able to reach out to KRK (one of our sister companies) and get a loan of three different sized subs - the KRK 8s, KRK 10s and KRK 12s. I used two different sets of ADAM monitors (S3-A's and A7's) along with a pair of Gibson Les Paul 8 studio monitors and a set of KRK Rokit 4 G3's with the various subs, and set up in various rooms in my studio and home to get a feel for how they would work in various combinations and environments.


First, let's take a look at the features all three models have in common…

All three KRK subwoofers use front loaded, vented drivers driven by efficient Class D amplifiers. The speakers and amps are mounted in stylishly curved cabinets with protective steel grilles and have unbalanced RCA inputs, as well as balanced inputs and outputs on both 1/4" TRS and XLR jacks. You connect the stereo outputs from your mixing board or sound card / audio interface directly to the inputs and then the outputs connect directly to your studio monitor speakers.

An onboard crossover is built into each of the KRK subwoofers, and a single knob sets the frequency below which the signal will be amplified by the sub, and above which will be routed to the connected studio monitors. This is a fairly common feature, but an important one - subs that feature a crossover at a single fixed frequency are less easily adapted to your monitors and room.

Each KRK subwoofer also has a volume knob. This controls the volume of just the subwoofer itself, allowing you to adjust its volume so that its relative level is matched to your studio monitors.

The back side of the KRK 10s, showing the various inputs, outputs and controls. The other two models are similar.


All three models have an Input Sensitivity switch to further optimize their operating range, and a Polarity switch allows you to flip the polarity of the subwoofer to match that of your studio monitors. There is also a standby switch on all three models. You also will find a Ground Lift switch on all the KRK subs, which can be useful for dealing with ground loops and hum.

One of my favorite features, which again, all three KRK subwoofers share, is the footswitch jack. While you can get by without one, you'd need a monitor controller that has a spare output for just the sub. With the KRKs, you just connect a cable and a footswitch (not included) and you can turn the sub on and off whenever you wish with just a stomp of your foot. When you turn it off with the footswitch, the KRK subs bypass their internal crossovers and route full-range audio out to your studio monitors. I consider this to be an essential feature - you simply must have the ability to run your monitors both with and without the sub, and the ability to switch between the two configurations quickly and easily in order to get the maximum benefit from owning a subwoofer.


Now let's look at where the three models are different...

KRK 8s


The smallest of the three is the KRK 8s ($581.64 MSRP / $349.00 "street"). With an 8" glass aramid composite woofer with a 1.5" voice coil and an amp that pumps out up to 109 watts (continuous), it is designed for use with nearfield monitors with 4" - 8" drivers.  The KRK 8s has a frequency response of 35 Hz - 133 Hz, and a low pass frequency range of 30 Hz - 205 Hz. Max peak SPL is 112.8 dB. The unit measures 13.3" H x 11.57" W x 14.25" D and weighs in at 26.01 pounds.

KRK 10s

 

The KRK 10s ($664.97 MSRP / $399.00 "street") is a mid-sized sub that is recommended for use with studio monitors with 4" - 8" woofers. It has a bigger 10" glass aramid composite woofer with a beefier 2" voice coil. The low pass frequency range is from 50 Hz - 130 Hz and the frequency response is 31 Hz - 110 Hz, so at the upper end of its range it's less able to cover some of the low-mids than the 8s is, so it's somewhat less well suited to pairing up with really small monitors that are seriously hurting in low and low midrange response. The amp is also beefier, and provides 160 watts continuous, giving the 10s a max peak SPL of 117.2 dB. It's physically a bit bigger too, measuring 15" H x 14" W x 16.06" D and weighs 34.5 pounds.

 

KRK 12s

 

The KRK 12s ($1,331.61 MSRP / $799.00 "street") is the big boy of the three subs that I auditioned, and it weighs in at 66.5 pounds and measures 18.11" H x 15.94 W x 22.64" D. With 240 watts of continuous power, it can hit 119.9 dB peak SPL. The KRK 12s has a frequency response of 29 Hz - 97 Hz, and a low pass frequency range of 55 Hz - 170 Hz. Because of its larger physical size it may be more difficult to find just the right place for it in smaller, more cramped rooms. It is recommended for use with studio monitors with 6" - 10" woofers. For those needing even "more" KRK also offers the 400W 12sHO sub ($1,499.00 "street), which I didn't check out this time around.

 


Things to watch out for

The KRK subwoofers don't include a footswitch, which makes sense because not everyone wants or needs one (and including one would increase the cost of the subs), but I think a footswitch should be considered an essential accessory unless your monitor controller has the ability to integrate a sub and control it independently of the studio monitors. It is simply too important (and useful) to have the ability to quickly turn the sub on and off while you're working to skimp and forgo getting a switch.  

How are the acoustics of your room? Many small rooms have serious acoustical issues in the low frequency range, and very few are adequately acoustically treated, again, especially in the low frequency range. Adding a subwoofer (or using full-sized monitors with excellent low frequency response) can excite the room and exacerbate the problems.

Larger subwoofers can present challenges not only in terms of driving the room too hard, but in terms of finding a suitable place to set them up.

Adding and using a subwoofer will take some adjustment in terms of how you work. All rooms have acoustical problems and "lie" to one degree or another, so it's essential that you take the time to learn how well-crafted music sounds in your room in order to be able to create mixes that will translate well to various playback systems outside of your studio.


So how do they pair up and compare - and how big of a sub should I get?

Ideally you want to try to match the size and power of the subwoofer to your existing monitors, just as the existing monitors should be sized and powered appropriately for the room you're working in and the volume levels you like running at. A sub that is underpowered and unable to keep up with the monitors is pointless, while an over-sized, high-powered sub is overkill if you're working with small, low-powered monitors in a smaller room.

If you have a big, well-treated control room with big, high-powered monitors and you like to bump it hard and play it loud, the KRK 12s is the obvious choice. Physically it's a BIG sub, and has loads of power - in fact, it's just a bit too much for a lot of situations and when paired with a lot of speakers. Of the speakers I had available to test with the three subs, I thought the Les Paul 8 Studio monitors and the ADAM S3-A's were best able to benefit from and keep up with the KRK 12s. With the smaller monitors, the 12s was really overkill.

In a similar way, the KRK 8s was just a wee bit too small to feel like it was sufficiently big and powerful enough to really excel when paired with the larger and more powerful Les Paul 8's or S3-A's, but in a smaller room it worked very well to fill out the bottom of the mix when partnered with the Rokit 4 G3's and ADAM A7's, and the resulting monitoring system remained nice and compact too, and was less likely to cause excessive low frequency buildup in the smaller room than the larger subs.

Of the three subwoofer models from KRK that I tried, I think the KRK 10s was my favorite. Extremely versatile, it hits the sweet spot in terms of power, physical size and low frequency "reach", and the price point makes it a terrific bargain. Some people will want an even larger sub, and if you're working in a large sized and properly treated control room, the KRK 12s will no doubt be the unit you'll want to go with, but I think the 10s is the one that will appeal to the widest range of users. Don't discount the 8s though - if you've been trying to get by with a set of small nearfields with 4" - 6" drivers, the 8s will be a revelation for you and show you things that are going on in the low frequencies of your mixes that you'd never be aware of without it.

While conventional wisdom tends to frown upon the idea of using a subwoofer in a smaller room or home studio, there's really nothing that says you can't do so - just as long as you're aware of the potential issues and are willing to use that bypass switch whenever it's appropriate, there's really no reason not to add one to your monitoring system. Ultimately it comes down to knowing your room and equipment and using whatever aids you in your quest for better recordings and mixes. If you can hear the lows better and that helps you EQ and lock the kick and bass together better than without the use of the sub, that's plenty of reason right there to add one to your studio. -HC-

 

Do you have questions or comments about this article? Want to discuss the subject of studio subwoofers? Then be sure to join the discussion in this thread in the Studio Trenches forum, right here on Harmony Central!



Resources

KRK 8s ($581.64 MSRP / $349.00 "street"), KRK 10s ($664.97 MSRP / $399.00 "street"), KRK 12s ($1,331.61 MSRP / $799.00 "street")    

KRK 8s subwoofer product page    

KRK 10s subwoofer product page    

KRK 12s subwoofer product page    


KRK subwoofer setup sound files   

KRK Subwoofer Placement and Setup Guide (PDF file)    


You can purchase KRK subwoofers from:

Sweetwater   

KRK 8s    

KRK 10s  

KRK 12s  


B&H Photo Video  

KRK 8s      

KRK 10s    

KRK 12s    










__________________________________________________

 




Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.  

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