Closer Acoustics Bi-Amp Interface

Passive line-level cable splitter for wideband + bass systems

What is it?

The Closer Acoustics Bi-Amp Interface is a high-quality passive line-level interface designed as a dedicated Y-splitter cable.

It features a fixed low-frequency crossover, created for purist bi-amping systems where simplicity, coherence and signal integrity are the highest priorities.

It allows a single source (Phono, CD Player, DAC or Streamer) to feed two integrated amplifiers simultaneously:

• one amplifier driving the wideband (full-range) loudspeakers,
• a second amplifier driving the dedicated bass modules.

All filtering is performed at line level, using a carefully tuned passive RC network integrated directly into the cable.

There is no DSP, no active electronics and no power supply involved.

Intended system topology

This interface is designed specifically for systems based on a wideband driver supported by a separate bass module, powered by two integrated amplifiers with independent volume controls.

• The Wideband Amplifier receives a full-bandwidth signal, with no filtering.
• The Bass Amplifier receives a low-pass filtered signal.

This preserves the fundamental advantage of wideband systems:

• no electrical crossover components between amplifier and wideband driver,
• no energy storage or phase disturbance in the midrange,
• a single driver handling the most sensitive part of the audio spectrum.

Key advantage: No L-pads in the signal path

Unlike traditional loudspeaker crossovers, the Bi-Amp Interface allows precise level matching between drivers without using L-pads or resistors in the loudspeaker signal path.

In conventional systems, matching a high-efficiency wideband driver with a bass module requires dissipating excess energy as heat, which inevitably reduces dynamics and immediacy.

With the Bi-Amp Interface:

• the wideband driver remains directly coupled to its amplifier,
• dynamics, micro-detail and tonal openness are preserved,
• level matching is performed at the amplifier level, not in the loudspeaker signal path.

Electrical concept

Pure Path

The wideband branch is designed for maximum transparency, keeping the signal path as direct and unencumbered as possible in the midrange and high frequencies.

Tuned Bass Filter

The bass branch incorporates a precision-tuned passive network, providing a smooth 6 dB/octave low-frequency roll-off.

Input Impedance Requirement – IMPORTANT

The bass filter is tuned for use with bass amplifiers featuring an input impedance of 47 kΩ or higher.

Using an amplifier with lower input impedance will shift the crossover frequency and increase insertion loss.

If you are unsure about your amplifier’s input impedance, please consult the manufacturer or contact us before installation.

Verified Performance

        Measured and verified using the CLIO measurement system.

A representative frequency response plot is included.

Professional Build

Constructed using low-capacitance professional cabling and original Amphenol RCA connectors for stable, low-loss signal transfer.

Available versions

Bass 72 Hz 

A balanced and musically natural crossover point tuned to match OKHO wide band unit, offering weight, scale and coherence without compromising the character of the wideband driver.

Bass 43 Hz

Optimized tuning for OGY monitors.

Polarity note – IMPORTANT

Due to the electrical phase behaviour of a first-order passive line-level crossover, the bass section must be connected with inverted polarity.

This means:

• the loudspeakers driven by the bass amplifier must be connected with reversed polarity

(positive to negative, negative to positive at the loudspeaker terminals).

This configuration ensures optimal acoustic summation in the crossover region and the most coherent integration between the wideband driver and the bass module.

How to connect

1. Connect the input of the Bi-Amp Interface to your source (Phono, CD Player, DAC or Streamer).

2. Connect the branch marked BASS 72 Hz (round enclosure) to the amplifier driving the bass modules.

3. Connect the remaining branch to the amplifier driving the wideband loudspeakers.

4. Use the volume controls on both amplifiers to achieve precise level matching between wideband and bass.

Important:

The BASS branch must be connected to an amplifier with 47 kΩ or higher input impedance to ensure correct crossover frequency and proper level behaviour.

Practical note: multiple sources

As the filtering is integrated directly into the cable, we recommend using a separate Bi-Amp Interface for each source.

This avoids additional switchboxes or preamplifiers and keeps the signal path as short and interference-free as possible.

What this product is NOT for

• Not intended for bass amplifiers with input impedance below 47 kΩ (unless a custom version is specified).
• Do not connect between an amplifier and loudspeakers.
• Not intended for power amplifiers without volume control.
• Not a substitute for a DSP crossover.