K231 Active Crossover, Front Angle
K231 Active Crossover, On Shelf
K231 Active Crossover, On Shelf 2
K231 Active Crossover, On Desk
K231 Active Crossover, Back
K231 Active Crossover, Open Front
K231 Active Crossover, Front Head on Open
K231 Active Crossover, Rear open
K231 Active Crossover, Rear angle open
K231 Active Crossover, Open Side
K231 Active Crossover, Open with shield
K231 Stereo 3-Way Active Crossover

K231 Stereo 3-Way Active Crossover

$ 599.95

May-15-2024: Notice to our customers: We're currently running a short back-log of about 1-2 weeks. We will process orders in the order they come in. We apologize for the inconvenience. Thank you, SA

Transform Your Sound System with Professional Grade Active Bi-Amping or Tri-Amping.

The K231 Stereo Electronic Crossover significantly improves the audio quality of your sound system by separating the high, mid and low frequency sounds using ultra low noise, high precision active filter circuits. This allows the use of a separate power amplifier channel for each speaker driver, and eliminates the need for passive crossovers. The result is a massively improved level of clarity and lower distortion of the sound produced. This is called Active Bi-Amping or Tri-Amping.

Our primary goal with the K231 is to bring the massive benefits of high quality analog active bi-amping into the price range that is affordable to the average audiophile. The K231 uses the highest quality audiophile grade components, and has specs that easily match those of the higher priced electronic crossovers such as Bryston and Marchand, but without the huge price tag.

 K231 Features:

  • Linkwitz-Riley filters, 4th order 24dB/Octave or optional 2nd order 12dB/Octave filter slope
  • High precision 0.1% filter components for precise XO frequency selection and ultra low distortion
  • Heavy internal Mu Metal shielding to prevent transformer noise from entering the audio paths
  • Allows you to Bi-amp or Tri-amp your sound system, or add a sub-woofer to vintage audio equipment lacking LFE
  • Supports 4-way or 5-way operation by cascading two K231's
  • All analog design using only the highest quality audiophile grade components:
    • Burr-Brown op-amps ~ Legendary audiophile grade op amps with .00005% Distortion
    • Metalized Polypropylene Film capacitors with 2% precision
    • Metal film resistors with 1% and 0.1% precision
    • ALPS metal film potentiometers
  • Crossover frequency and slope is selected through pluggable 'XO Modules'
  • Wide range of XO Modules are available to support any crossover frequency
  • Optional Sub channel L/R mixer to support a mono sub-woofer channel
  • Supports both Balanced and Unbalanced audio signaling on all inputs and outputs
  • Sub, Mid and High output gain front panel adjustments
  • Baffle Step Compensation, with adjustable gain and selectable baffle size ranges
  • Made in USA
  • 45 Day No-Hassle Return


  • THD Better than 0.00068%
  • THD+N: Better than 0.0074%
  • IMD : Better than 0.0088%
  • SNR: 120dB
  • Channel Crosstalk Less than -83dB
  • Frequency Response: Linear from 10Hz - 250KHz
  • CMRR (balanced input): Better than 70dB
  • Input Impedance: 75K ohms unbalanced, 150K ohms balanced
  • Input Signal Max: 5.5V
  • Insertion Gain: Adjustable -9dB to +8dB
  • Filter Topology: Linkwitz-Riley, Constant Voltage, 4th Order, 24dB/Octave
  • Enclosure: Aluminum Extruded Chassis
  • Dimensions: 6.5”W x 6.5”D x 2.5”H
  • Shipping Weight: 2.5 lbs
  • Power Supply: Internal Analog Bi-polar, 20,000uF total filter cap
  • AC: 115/230 VAC, using standard C13 plug

 Audio Signal Inputs:

  • Stereo Balanced: ¼” TRS Jacks
  • Stereo Unbalanced: RCA jacks

 Audio Signal Outputs:

  • Stereo Balanced High, Mid, Low: ¼” TRS Jacks
  • Stereo Unbalanced High, Mid, Low: RCA Jacks

Preview the K231 User Manual (.pdf)

We stock the following XO Module frequencies. When ordering, please specify your desired 'Sub' and 'Mid/High' crossover frequencies, as well as the slope (12dB or 24dB/octave) in the 'Special Instructions' box on the shopping cart page:

    • Any multiple of 5Hz from 30Hz-100Hz (e.g. 30Hz, 35Hz, ... 100Hz)
    • Any multiple of 10Hz from 110Hz-200Hz (e.g. 110Hz, 120Hz, ... 200Hz)
    • 250Hz, 275H, 350Hz, 450Hz
    • Any multiple of 100Hz from 300Hz-4000Hz
    • Any multiple of 500Hz from 4500Hz-16KHz

You may want to experiment with various crossover frequencies and/or slopes. This can be easily done with the K231. Simply plug in a new XO Module to set a new crossover frequency.

The K231 comes with 2 XO modules. You can order additional XO Modules here

Questions? Please see our FAQ for many answers.

Trouble? Check out our Troubleshooting page.

To read more about the advantages of active Bi-Amp'ing ~ 'Making the Case for Active Crossovers vs. Passive'

Customer Reviews

Based on 21 reviews
Jim, Lake Ridge, VA

I have been using the Sublime Audio K231 since May 2021 and since then I have tried a couple much more expensive units, as much as $3500, in an attempt to improve my system, however, each time I came back to the K231 and realized it's just better in every way. Primarily I use the K231 in two way mode with a subwoofer and I find the bass tighter and deeper than other approaches. In the past I have used the three way mode with vintage speakers such as Altec 846b, various Klipsch, and others and found my vintage tube amps as well as the speakers obviously love the Sublime Audio K231. As a subwoofer crossover the K231 easily bests both the SPL ($3K) and the JL Audio ($3.5K) units. And as a three way, I find the results are state of the art as well. I am so impressed with this unit that I am in the process of ordering a second unit just to have a backup or to expand my system in the future.

Jim J.

David libby
LRS plus is magnificent with this crossover.

Listening experience, listening to LRS pluses,, play again, this active crossover calibrated for your system in your room. You can easily do now now sit down, put your playing record on and then put your best record playing on. You’re gonna see improvement from the bottom and your eyes because now you can take and round off the high end, just the tilt depending on your room, anyhow enjoy and remember you could purchase from them and you can return it if it doesn’t do as you think it should absolutely great company high review recommended to three of my friends. Tom already purchased good luck guys. It’s only a hobby and expensive one, though I’m a car guy and that’s expensive as well , that’s the two toys I live with my wife listening

Phil McGuigan
Sublime Acoustic K231 in vintage U.K. made system

I had been considering an active crossover for my already bi amped system, feeding some very nice c2000 Castle Pembroke two way floorstanders. The K231 was the best analogue option in my price range. I have paired it up with a Tisbury Audio passive pre amp, and the two work very well together. I actually decided to expand the system to three channel, with a BK subwoofer, only a mono subwoofer at the moment. The crossover came with a few plug in modules to give me options and provide some future proofing. I’ve started with crossover points at 60Hz and 2.7kHz and noticed an immediate improvement in imaging and detail, it’s almost night and day really, and this is against the original speaker crossovers which were known for their quality. The improvements in mid and treble, coupled with the ability to easily run one or two subwoofers at line level, make this active crossover something of a bargain, even considering the additional import duty I paid to get it in to the U.K. In addition, there is an option to use either balanced or RCA connections, due to constraints with the other components I have I’m using RCA, and using short run decent quality cables in an attempt to make up for deficiencies against a balanced set up.
The actual set up and installation of the crossover is nowhere near as daunting as it might appear. I am really pleased with it, and would definitely recommend this active crossover.

Scott Kinder

I started off with some old 1970s JBL 3-way speakers, the Jubal L65 (with the original crossover/dividing networks), and a 2-channel (stereo) power amp.

When I got enough amps (6 channels' worth) to drive my speakers in a tri-amp configuration, I went with the Sublime Acoustic 3-way PCB style crossovers, and there was definitely an improvement in clarity, plus it gave the possibility to adjust the level of each band and set the filter frequency for each crossover point with the plug-in modules. However, it was a bit fiddly, even though I know my way around electronics, to get everything dialed in and find a home for the PCBs (without a nice housing).

The Sublime Acoustic K231 is the product I wish I had gotten from the beginning. The components are clearly top-shelf (just like everything made by Sublime Acoustic). The design is top-notch; no-frills yet elegant, all contained in a stylish metal housing. I enjoyed learning and doing the DIY thing before, but having a product in a box is just awesome. No-brainer.

What a filter!!!!!

This is the best thing I have in my active speaker system. So good that I did replace my amplifiers thinking that in my previous setup, noise was coming from the filters. It was coming from the amplifiers. Seriously, it’s a really good product. Don’t hesitate and they are always answering to emails if you need some help. Thanks

Customer Reviews

Based on 18 reviews Write a review