Saturday, January 6, 2024


Eris 8 Subwoofer - click to enlarge

Need to put a little boom in your room? This little subwoofer is up to the task so long as you don't need to play too loud.

Presonus makes several small speaker systems that are a little bit short on bass response. By adding a subwoofer you can add a lot of fullness in the bass frequencies. I added one of these compact and inexpensive subwoofers to our little Eris 3.5 monitor system in Studio-B. This is one of my favorite places for listening to mixes I've created in the main studio. 


Around on the backside of this little subwoofer you'll find a bunch of jacks and controls, lets look at what it's all for.

Inputs and outputs - click to enlarge


The inputs are available as a pair of 1/4” balanced jacks for connection to pro-audio systems and a pair of RCA phono unbalanced which are used for matching the subwoofer to consumer stereo equipment.


The subwoofer has a builtin crossover network which is capable of isolating the bass region and sending the bass frequencies to the subwoofer speaker while simultaneously passing the high frequency sound to a connected pair of stereo speakers. The crossover outputs which drive the stereo speakers are available on 1/4” TRS balanced jacks for pro speaker connections and a pair of unbalanced RCA phono jacks to drive consumer modelss of unbalanced powered speakers. 

Subwoofer controls - click to enlarge


Above the Input and Output jack area is where you'll find the Gain-knob which sets the volume from the subwoofer. 

A variable LowPass Filter knob is provided for adjusting the frequency where you want to transition from speakers to the subwoofer. I'm using my Eris Sub 8 with a pair of Eris 3.5 powered speakers so I set the LowPass Filter knob to around 100 Hz. I adjusted this setting by ear until the response from the Eris 3.5 speakers transitioned smoothly to the subwoofer.

A phase switch is provided which flips the polarity of the subwoofer relative to the speakers connected. This allows the subwoofer to be used with the widest variety of speaker brands and models (not just Presonus speakers).

A HPF (High Pass Filter) switch is provided. This switch cuts the bass to the speakers at the selected frequency on the LowPassFilter knob. Hint: I run my connected Eris 3.5 speakers full range, HPF off, then I adjust the crossover down around 80 or slightly lower to fill in the bottom end with the Sub-8.

These settings can give a flatter overall frequency response when adjusted carefully. With the HPF Off, the connected stereo speakers run full range and the subwoofer output (from below the crossover frequency) is added to your listening experience. This can lead to bass build up in the crossover region; to help mitigate this effect set the crossover point low, to where the bass from the speakers is naturally diminishing.


  • Speaker Size: 8”
  • Paper composite low-frequency driver with rubber surround 
  • 50 watt RMS Class AB amplifier
  • Frequency Response (adjustable): 30Hz to 200 Hz
  • Maximum Peak Volume: 100 dB @ 1m
  • Balanced 1/4” Inputs and Outputs
  • Unbalanced RCA phono Inputs and Outputs
  • Weight 15 pounds


  • Budget price
  • Surprising amount of bass output
  • Reliable performance 
  • Lots of connection options
  • Builtin electronic crossover


None to speak of


This is a versatile subwoofer available in a stand alone package. The features allow it to be used quite effectively with a wide variety of powered speaker systems by various brands. I wondered if it would have enough power, would it be adjustable enough and maybe most important, would it last and be reliable. I've had it in use 24/7 for the last nine months and so far this compact subwoofer has not disappointed. If it breaks down I'll report back right here.

Thanks for reading High on Technology. Good Music To You!

©January 2024 by Mark King. It's not ok to copy or quote without written permission from the author.