Quick answer: Wire pole 1 positive to the amplifier positive and pole 1 negative to the amplifier negative. On a four pole connector, pole 2 positive and negative carry the second circuit for bi-amp. In bridge mode the output is taken from pole 1 positive and pole 2 positive, which is the exception that catches most installers. Confirm every cable with a continuity test before use.
Speakon Wiring Diagram: NL2, NL4 and Bridge Pinouts
A speakon wiring diagram is only useful if it tells you which pole does what and where the exceptions are. The convention is simple: pole 1 carries the main circuit, pole 2 carries a second circuit, and bridge mode breaks the pattern by using two positive poles. Most wiring faults come from applying the normal pattern to a bridged amplifier, or from wiring only one pair in a four pole cable and then reconfiguring the system later. A written diagram and a continuity test settle the question before the cable reaches a stage.
How the Speakon Pin Convention Works
The connector numbers its contacts as 1 plus, 1 minus, 2 plus, 2 minus and so on up to the pole count. Pole 1 is the default circuit for a single amplifier channel, which is why a two pole plug works in a four pole socket. Pole 2 exists so that one cable can carry a second channel to a bi-amp cabinet or a second loudspeaker. The convention is consistent across two, four and eight pole bodies, so a diagram learned on one transfers to the others.
Pole 1 Is Always the Main Circuit
Treat 1 plus and 1 minus as the pair that must always be connected, whatever else the cable carries. A cable with only pole 2 wired will appear dead on a normal amplifier and will confuse anyone testing it, because the connector fits and latches but no circuit exists. Mark the main pair on both ends when building stock.
Pole 2 and the Second Pair
Pole 2 is used for the high frequency section in a passive bi-wire cabinet, or for the second channel in a bi-amp system. It is also the pair that carries the bridged output on many amplifiers, which is the source of the confusion described below. Never assume pole 2 is spare; check the amplifier manual for the channel in question.
NL2, NL4 and NL8 in Practice
A two pole connector has only 1 plus and 1 minus, so there is nothing to get wrong beyond polarity. A four pole connector adds the second pair and with it every opportunity for a swapped or missing connection. An eight pole connector extends the same logic to four circuits, usually for amplifier racks feeding multi-way cabinets. The physical body grows with pole count, which affects cable diameter and assembly space rather than the wiring logic.
Two Pole Wiring
Connect 1 plus to the amplifier positive terminal and 1 minus to the negative. At the cabinet end, 1 plus goes to the driver positive and 1 minus to the negative. Check that both ends use the same convention, because a cable wired with the pair reversed at one end inverts that cabinet against the rest of the system.
Four Pole Wiring for Bi-Amp
Wire 1 plus and 1 minus to the low frequency amplifier channel and 2 plus and 2 minus to the high frequency channel, then match the cabinet plate so the internal crossover or direct driver connections land on the same poles. Label both ends with the pair assignment. A four pole cable with only pair one connected is a latent fault in any bi-amp system.
Bridge Mode and Its Wiring Trap
A bridged amplifier combines two channels into one, and the output is no longer referenced to ground in the usual way. On a speakon output that means the signal appears between pole 1 positive and pole 2 positive. An installer who wires 1 plus and 1 minus as usual gets either silence or a fault, depending on the amplifier protection. This single exception accounts for a large share of bridge mode failures.
What Bridge Mode Changes
In bridge mode one channel drives the positive side and the other drives the negative side of the load, so both output terminals are live. The load sees twice the voltage swing of a single channel. That also means the cable carries the bridged current on two positive poles, and the negative poles are not used at all.
The Most Common Miswiring
The common error is a cable built for normal stereo use and then plugged into a bridged output. Nothing looks wrong, the connector latches, and the result is no output or a protection trip. Label bridged cables clearly at both ends and keep them out of general stock, so the fault cannot be repeated.
Checking the Diagram Against the Cable
A diagram is a claim about a cable, and the cable has to be tested. A continuity test with a meter proves which pin reaches which conductor, and it takes less than a minute per cable. Do it at build time, then again after any repair, and keep a simple record. The test also catches the failures that a listening check misses, such as a strand bridging two poles that only shorts when the cable is flexed.
Continuity Test Procedure
Set the meter to continuity or resistance, probe from the tip of each pole at one end to the corresponding terminal at the other, and confirm a reading near zero ohms. Then probe between adjacent poles to confirm no short. Finally flex both ends while watching the reading, which reveals a conductor that is only partly clamped.
Symptoms of a Wrong Pinout
One cabinet quieter than its pair, a channel that works only when the plug is rotated, bass present but no high frequency, or a protection light on one channel all fit a pinout or polarity error. Swap the cable for a known good one first, because that single step separates a cable fault from an amplifier fault.
Speakon Pin Assignment by Pole Count
| Connector | Pole | Circuit | Typical use | Wiring note |
|---|---|---|---|---|
| NL2 | 1 plus / 1 minus | Main | Single channel | Only pair available |
| NL4 | 1 plus / 1 minus | Main | Channel A or full range | Always connect |
| NL4 | 2 plus / 2 minus | Second | Channel B or bi-amp high | Connect for bi-amp only |
| NL4 bridged | 1 plus / 2 plus | Bridged output | Single high power load | Exception to the pattern |
| NL8 | 1 to 4 pairs | Four circuits | Amp racks, multi-way | Label every pair |
| NL8 bridged | 1 plus / 2 plus | Bridged output | High power subwoofer | Same exception applies |
Real-World Application Scenarios
A club system with passive cabinets uses two pole connectors, and the wiring diagram is simply polarity at both ends, which is why the install never has a channel fault. A touring rig running bi-amp cabinets uses four pole cables with both pairs wired, and each cable is labelled for pair assignment so a technician can swap one without opening the cabinet. A subwoofer rack running bridged amplifiers keeps a separate set of bridged cables with the 1 plus and 2 plus configuration, stored apart from the standard stock. In each case the diagram is written down rather than remembered.
Related Guides on This Site
The cable itself is covered in speakon cable and the both-ends case in speakon to speakon cable. Polarity practice is explained in speaker cable polarity, and plug assembly in speakon plug.
Frequently Asked Questions (FAQ)
Q: Which speakon pins are positive and negative?
A: Pole 1 plus is positive for the main circuit and pole 1 minus is negative. On a four pole connector, pole 2 plus and 2 minus carry the second circuit. In bridge mode the output uses pole 1 plus and pole 2 plus.
Q: How do I wire a speakon for bridge mode?
A: Connect the load between pole 1 plus and pole 2 plus. Do not use pole 1 minus or pole 2 minus for the load, because both output terminals are live in bridge mode and the usual pair will not work.
Q: Can I use a four pole cable on a two pole socket?
A: The plug body may fit the socket, but only the poles the socket provides will connect. If the cable uses pair two and the socket only has pair one, the circuit is open and the cabinet appears dead.
Q: How do I test speakon wiring without a special tool?
A: Use a multimeter on continuity. Probe each pole at one end to its terminal at the other end, then check for shorts between adjacent poles. Flex the ends while watching the reading to catch a partly clamped conductor.
Q: Does it matter which way the pair is wired?
A: Yes. A reversed pair inverts that cabinet against the others, which cancels bass where two cabinets overlap. The error is easy to miss on a single box and obvious once two cabinets share the same space.