Subharmonic Synthesizer: Get Great Low End In Your Mix

Posted by Brian on on 8th May 2016

The bass is where it’s at

Let’s talk about that important low end in music. Whether you are working in a live venue or dialing up a mix in the studio, the low end in your mix delivers a feeling of power to the listener. As musical frequencies go further into the bass range, we begin to hear these pitches not only with our ears but our whole body. There is something very psychologically basal about bass. It speaks to all of us.

Bass management

It’s quite accurate to say that good management of these bottom-most frequencies is much more than half the battle in creating good mixes. This applies to a mix that is drowning in bass or simply lacking enough of anything down there to get the listeners blood pumping. This brings up two important points about bass management:

  • The deep bass range is where rumbles, structural noise and other low frequency artifacts live. These unwanted blights must be carefully removed. They only serve to muddy up a mix.
  • You should not try to turn up something that is not there. All you will get is enhancement of those low frequency artifacts mentioned above.

One of the bass management tools in a mix engineer’s arsenal is a subharmonic synthesizer. These interesting marvels of epic bass-dom are a powerful tool in the right hands. However, if not properly handled, they can create more problems than they solve. Let’s take a look at an example of a subharmonic synthesizer and go through the basics of how to properly use it.

Where to get the goods

DBX 120AThe DBX 120A is a subharmonic synthesizer from a well established audio equipment company. The 120A focuses on the singular task of generating those subjacent frequencies that your inner bass-child is craving. 


A much more feature rich speaker management tool that includes a subharmonic synthesizer is the DBX DRIVE RACK PA-2. The Drive Rack is a speaker optimization tool for use in live venues. It offers driver alignment, limiting, compression and EQ in addition to the subharmonic synthesizer feature we are talking about today. Amongst other nifty features, the Drive Rack allows control of its features wirelessly via a smartphone or tablet. The Drive Rack is quite a bit more expensive than the 120A due to its rich offering of features.

How it works

A subharmonic synthesizer looks at audio content between 55 and 110 hertz. It then creates subharmonic content that is one octave lower than the source. This newly generated material is then divided into two separately controllable bands: 24 to 36 hertz and 36 to 56 hertz. Using a separate level control for each of these bands, the user can dial in just the right amount of girth and bump to please the low end appetite of the audience or to loosen dental fillings if desired.

Using the features

Since the Drive Rack PA-2 offers so many other audio goodies, we will focus on using the DBX120A, which is solely designed for the task of subharmonic synthesis.

The 120A is configured for stereo use. This means that the two audio channels it is equipped with are both controlled with a single set of knobs on the front. Patch into the 120A using the pair of ¼” connections on the back. Processed signals can then be routed to power amps, instrument preamps or even an effects return connection on your mixing console. The particular routing configuration will depend on how you are applying the subharmonic effect to your audio. Note that there is also a pair of RCA inputs thrown in for convenience. You will notice that there are three outputs. Two of these represent a stereo output and the third is for routing bass frequencies to a subwoofer. All of the ¼” jacks will work with either TRS balanced or TS unbalanced connections. The main stereo outputs can be set to deliver full range audio or mids and highs alone.

Once you have your inputs and outputs all squared away for your given application, first use the crossover engage switch on the back panel to choose whether the 120A will send full range audio out of the main stereo outputs or divide and send the low frequency content from the subwoofer output and the remaining mid/high portion from the stereo outputs. A green LED on the front panel will indicate when the crossover is in use. When the crossover is engaged, the crossover frequency select switch on the front can be used to choose 80 or 120 hertz as the crossover point.

Use the two subharmonic band controls on the front panel to tailor the amount of each bass band. You will find that these settings will vary from room to room. A little experimentation for the particular application is often called for. If the sub bass range sounds too growly or contains too much “woof”, try turning the 36 to 56 hertz knob down. If you are blowing fuses and can hear that your woofers are being pushed too hard and may vomit up their cones at any moment, turn down the 24 to 36 hertz knob. While these two knobs are used to fine tune the balance between the two sub bands, DBX wisely included an overall sub range knob to bring the whole synthesis band up or down. Similarly, there is a master level dedicated to the subwoofer output.

I suggest you only use a subharmonic synthesizer in the studio in conjunction with a subwoofer. Without a subwoofer to tell you about ultra low frequency happenings, it’s just too risky to add low frequency content that you partially can not hear. Without a subwoofer, you may inadvertently be creating an ultra low frequency earthquake effect in the middle of your audio track. In live applications, you are free to use a subharmonic synthesizer without subwoofers if you want.

Have fun with it

A subharmonic synthesizer can be used on whole mixes as well as individual instruments. In addition to the various mixes and instruments that may benefit from a subharmonic synthesizer, there are different ways to apply it to each scenario. Changes in routing and application will yield different results.

  • One obvious application would be sound for dance music. If you are a live D.J. and lack those all important decumbent frequencies, the only gigs you will be hosting will be the bunny-hop at the local retirement home. Pump those subharmonic frequencies into your massive wall of subwoofers and grin in delight as each bass hit blurs your vision.
  • A bass guitarist can include a subharmonic synthesizer in his rig to ensure the he alone owns the deepest frequencies. The most efficient way for a bassist to use those ultra low rumblings is to use a dedicated 18” speaker for the subharmonic content.
  • If guitar players would like to sound like they possess the ultimate earth shattering rig of doom, judicious use of a subharmonic synthesizer is one way to accomplish this while also eliciting a few dirty looks from the bass player for invading his territory.
  • As mentioned before, a subharmonic synthesizer can also be used in similar fashion to reverberation at the sound board. This offers the mix engineer the option of applying the effect to any instrument in the mix. Since the mix engineer’s view is focused more on the mix as a whole, this may be the best place for this effect to be dialed in. As is true in all audio mixing, the name of the game is give and take. Massive walls of bass frequencies piled on top of each other do not add up to a good mix. The mix engineer is likely to take this into consideration when sculpting the sound of the band. Each instrument’s bass region can’t be allowed to all live in the same place in terms of frequency. Supporting discrete “sweet zones” for each instrument will help the entire mix sound powerful and clear at the same time. This principal applies to live music as well as mixing in the studio.

Be careful with the power you wield

With great power comes great… No, I’m not going to stoop to that overused cliche. But you do need to understand that if you have a problem with subtlety, a subharmonic synthesizer is probably not for you. Overusing this groovy tool will not result in additional “groovy” for your music, it will only transform it from sheikh to geek faster than greased lightning. Here are a few reminders for safeguarding against this overuse phenomenon plus a few other cautions that may contribute to the health of your speakers:

  • As mentioned before, do not attempt to stack one instrument’s bass region on top of another. This results in low frequency muck. It’s just wrong, very wrong.
  • It is equally important to remove ultra low frequency content from all instruments that do not produce anything usable down there. Free up that delightfully below-ground bass region so you can use it on something that is really cool. The use of low cut filters on each instrument is the order of the day.
  • Do not use a subharmonic synthesizer to process non-musical sound effects such as thunder, gunfire, explosions or your drunk Scottish cousin belching the alphabet. The only explosions you will hear is your subwoofer cones launching themselves out of their speaker cabinet.
  • Use proper power up and power down sequencing. With a subharmonic synthesizer in the mix, those damaging pops produced by improper power sequencing can be catastrophic. Always turn your power amps on last and off first. This will protect your speakers.

A trick up your sleeve

While you should never attempt to use a subharmonic synthesizer to compensate for poor mixing skills, this little beauty can add a bit of awesome sauce to your mixes if handled properly. Brandish this audio tool with caution and make your mixes bump with the best of them.