ESB Audio 5.6K2 CX — 5000 Series 2-Way Passive Crossover (pair)

ESB Audio 5.6K2 CX — 5000 Series 2-Way Passive Crossover (pair)

The 5.6K2 CX is the two-way passive network built for the ESB 5.165 mid-woofer and 5.028 tweeter. It divides at 2.1 kHz using 12 dB/oct Butterworth filters on both sections and handles 300 W. Sold as a pair.

Why 2.1 kHz Is the Number

The crossover point is not a round figure and it was not chosen for convenience.

ESB rates the 5.028 tweeter down to 2 kHz behind a 12 dB/oct filter — that is the published limit for this slope. The 5.165 mid-woofer is rated up to 4 kHz. Setting the crossover at 2.1 kHz puts the handover just above the tweeter's rated floor and well inside the woofer's ceiling, which is the correct place for it given the filter order the network uses.

That is what a matched passive crossover buys: someone has read both driver datasheets and picked the point where each is comfortable, rather than defaulting to 3 kHz because it is a common answer.

Butterworth on Both Sides

Both sections are 12 dB/octave Butterworth — a low-pass on the woofer and a high-pass on the tweeter.

Butterworth is the maximally flat alignment: each filter's own response is as flat as it can be through the passband before it turns down. Chosen for both halves of a two-way, it produces a predictable, well-behaved summation at the crossover point, which is what a passive network needs when it cannot be adjusted afterward.

Component Choices

The capacitors use polypropylene or Mylar dielectrics rather than electrolytics. Electrolytic capacitors drift in value with age and temperature; film capacitors hold their value, which means the crossover point stays where it was designed to be over the life of the system.

The resistors are oversized and non-inductive. Oversized so they dissipate the heat of continuous operation without changing value, and non-inductive so the resistor itself does not add unintended reactance to a network whose behaviour depends on precise component values.

These are the parts that separate a designed crossover from a pair of capacitors in line with a tweeter, and they are the reason a network like this holds its tuning.

Tweeter Level Adjustment

A two-position high-frequency control offers 0 or −2 dB.

Two decibels sounds small and is not. Every car puts the tweeters somewhere different — a pillar aimed across the cabin, a sail panel closer to the ear, a door upper behind a grille — and the reflective character of the interior varies enormously between a cloth-trimmed sedan and a glass-heavy coupe. The −2 dB position exists so a system that measures bright in a live cabin can be corrected at the crossover rather than left to be fixed downstream.

Set it by listening in the vehicle, not on the bench.

System Application

The 5.165 and 5.028 driven from a single amplifier channel per side. Buying the drivers as the 5.6K2 kit and adding this network gives the same system as the 5.6K2X, which ships with it included.

A system running the same drivers actively from a DSP does not need this crossover — the processor does the filtering, with adjustable slopes and delay that a passive network cannot offer. This is the right part when the amplifier channels are not available, or when the build is deliberately simple.

Note that the 5.165 is a 3-ohm driver and the 5.028 is 4 ohms. The network is designed around that pairing; it is not a general-purpose crossover for other drivers.

Installation Considerations

The network measures 117 × 72 × 31 mm. It needs a mounting location that is dry, secure, and reachable — the tweeter level switch should be accessible after the trim goes back on, because it is a setting worth revisiting once the system has been listened to.

Terminals accept cable up to 4.5 mm (6 AWG), which is generous for a passive network and leaves room for the speaker cable most builds will use.

Mount it away from power cabling and amplifier heat. Observe polarity on every connection — a reversed tweeter in a 12 dB/oct network produces a cancellation at the crossover point that is easy to hear and easy to misdiagnose as a tuning problem.

Specifications

• Type: 2-way passive crossover network
• Crossover frequency: 2.1 kHz
• Slope: 12 dB/oct low-pass Butterworth · 12 dB/oct high-pass Butterworth
• High-frequency level: 0 / −2 dB
• Capacitors: polypropylene or Mylar dielectric
• Resistors: oversized, non-inductive
• Low-frequency section: ESB 5.165
• High-frequency section: ESB 5.028
• Power handling: 300W
• Cable connector: up to 4.5 mm (6 AWG)
• Dimensions: 117 × 72 × 31 mm
• Sold as: pair

HF Audio Perspective

Passive crossovers get treated as the compromise option, and for a two-way that is not really true.

What an active system buys you in a two-way is adjustable crossover points, steeper slopes, and delay between the woofer and the tweeter. The delay is the valuable part — and in a two-way where the tweeter sits close to the woofer, or where both are in the door, there is not much delay to correct. The gain is smaller than it is in a three-way.

What this network gives instead is a crossover point chosen against both driver datasheets, film capacitors that will still be at their design values in ten years, and one amplifier channel per side instead of two. For a system that is meant to be built once and left alone, that is a legitimate choice rather than a fallback.

The one thing we would not skip is setting the −2 dB tweeter position deliberately. It is there because the vehicle is a variable ESB cannot know, and leaving it at 0 dB by default is leaving the only adjustment on the network unused.