Connecting a high-to-low level converter
How do I connect a subwoofer using a high-to-low level converter?
A high-to-low level converter is used when the car’s factory stereo does not have RCA or low-level outputs. The converter instead takes the signal from the car’s speaker wires and converts it into a low-level signal that can be connected to an amplifier.
This is a common solution when you want to keep the factory stereo but add an amplifier and subwoofer.
Where do I get the signal from?
The signal can usually be taken from:
The speaker wires at an existing speaker.
The speaker outputs from the factory stereo.
The speaker outputs from the factory amplifier.
The important thing is that the signal you use actually contains the frequencies needed for the subwoofer.
In some factory audio systems, the signal is already filtered or processed. A certain speaker channel may, for example, lack the lowest bass frequencies. In those cases, you may need to take the signal from another channel or combine several channels.
Is it enough to take the signal from one speaker channel?
Yes, in some installations it may be enough to take the signal from a single speaker channel.
This requires that:
The high-to-low level converter is designed to be used that way.
The speaker channel contains the bass signal you need.
The converter or amplifier can handle the signal correctly.
Keep in mind that a single channel only contains the information from, for example, the left or right audio channel. In many installations, it is therefore better to use both the left and right signals.
How do I connect the speaker-level signal?
When connecting the high-level signal, both positive (+) and negative (−) from the same speaker channel must be connected to the corresponding input on the high-to-low level converter.
Example:
Left channel
Left speaker output + → Converter left +
Left speaker output − → Converter left −
Right channel
Right speaker output + → Converter right +
Right speaker output − → Converter right −
Do not mix the positive from one channel with the negative from another.
Can I connect the speaker negative to the vehicle chassis?
No.
The speaker signal negative is part of the audio signal and must be connected to the corresponding negative wire from the same speaker channel.
It must not be connected to the vehicle chassis or used as a normal ground.
This is especially important in modern vehicles where the speaker outputs are often balanced or bridged. Incorrect wiring can cause interference, poor sound and, in the worst case, damage to the factory equipment.
How do I connect multiple channels?
If the high-to-low level converter has, for example, left and right inputs, you normally connect each speaker channel separately.
Each input should receive its own positive and negative pair from the same channel.
If the vehicle has a more advanced factory audio system, the signal may be split between several speakers. In that case, a converter with signal summing or a DSP may be required to create a complete signal.
How do I know if the signal contains enough bass?
It is not always possible to tell simply by looking at which speaker the wire goes to.
The factory stereo or factory amplifier may already have filtered the signal.
Signs that you may have taken the signal from the wrong source include:
Very weak bass.
Bass disappears at certain frequencies.
Bass level changes significantly when the stereo volume changes.
Bass decreases as you increase the volume.
The subwoofer only plays a limited frequency range.
In more advanced factory systems, the signal may need to be measured or analysed before choosing the connection point.
What happens after the high-to-low level converter?
The converter’s low-level output is usually connected to the amplifier’s RCA input.
The amplifier gain and crossover settings then need to be adjusted correctly for the subwoofer.
Gain is not a normal volume control. It is used to match the amplifier’s input sensitivity to the signal from the converter.
Important things to keep in mind
Always follow the wiring diagram for the high-to-low level converter you are using.
Check polarity before connecting.
Always connect positive and negative from the same speaker channel.
Do not connect the speaker signal negative to the vehicle chassis.
Make sure the signal you are using actually contains bass frequencies.
In advanced factory audio systems, a DSP or converter with signal summing may be required.
If you are unsure where to take the signal from, contact our customer service team with the vehicle model, model year and information about the factory stereo or audio system. Feel free to include photos of the connections, and we can help you assess the installation.