Which speaker cabinet can I connect to CHUCK?
CHUCK's SPEAKER output delivers up to 25 watts into 4 ohms. You can connect passive guitar cabinets of 4, 8 or 16 ohms — the total impedance must not drop below 4 ohms.
In short: CHUCK's SPEAKER output delivers up to 25 watts into 4 ohms. You can connect passive guitar cabinets of 4, 8 or 16 ohms. The higher the cabinet's impedance, the less power the power amp delivers:
- 4 ohms: around 25 watts
- 8 ohms: around 12.5 watts
- 16 ohms: around 6.25 watts
Important: the total impedance must not drop below 4 ohms.
How to connect the cabinet
Connect CHUCK's SPEAKER output to the input of a passive speaker cabinet. Use a suitable speaker cable. The SPEAKER output is an amplified power output. So never connect it to a guitar input, line input, mixer, audio interface or active speaker cabinet. For those devices, use OUT 1 or OUT 2.
What does impedance mean?
A speaker cabinet's impedance is given in ohms. Among other things, it determines how heavily the power amp is loaded electrically. CHUCK delivers its maximum output power into a 4-ohm cabinet. A cabinet with higher impedance loads the power amp less, but also receives less power.
The power figures are approximate. Speakers don't have a constant impedance across the whole frequency range, so the actual power delivered can vary slightly.
Does half the power mean half the volume?
Half the power does not mean half the volume. Going from 25 to 12.5 watts is audible, but the difference feels much smaller than the numbers suggest. Halving the power reduces the maximum level by only about 3 dB. For roughly half the perceived loudness, the power would have to drop to about a tenth — so from 25 watts to around 2.5 watts.
25 watts versus 12.5 watts: The power is halved. The maximum level drops by about 3 dB. As a rule of thumb, 12.5 watts sound about 81 percent as loud as 25 watts. Conversely, 25 watts sound about 1.23 times as loud as 12.5 watts.
25 watts versus 6.25 watts: The power is quartered. The maximum level drops by about 6 dB. As a rule of thumb, 6.25 watts sound about 66 percent as loud as 25 watts. Conversely, 25 watts sound about 1.52 times as loud as 6.25 watts.
How loud are 25 watts compared with 100 watts?
100 watts is four times the electrical power of 25 watts, but not four times as loud. The theoretical level difference is only about 6 dB. Under comparable conditions, as a rule of thumb 100 watts sound about 1.52 times as loud as 25 watts. For a subjective doubling of loudness over 25 watts, you would theoretically need about 250 watts.
Watts alone don't determine loudness
The actual loudness doesn't depend on amplifier power alone. Other big factors are:
- the efficiency (sensitivity) of the speaker
- the number and arrangement of the speakers
- the cabinet design
- the frequency response and the sound used
- placement and distance
- room acoustics
- the distortion and dynamics of the signal
An efficient 8-ohm cabinet can therefore be louder in practice than a less efficient 4-ohm cabinet, even though it receives less amplifier power.
⚠️ Safety: Do not use a load below 4 ohms. Use a speaker cable, not an ordinary instrument cable. The SPEAKER output must not be connected to a normal amp or line input. Make sure the cabinet can safely handle the power delivered.
Key takeaways
- Suitable cabinets are passive, with 4, 8 or 16 ohms.
- Do not use a load below 4 ohms.
- 4 ohms delivers the maximum power of 25 watts.
- 8 and 16 ohms are allowed but deliver less power.
- Half the power does not mean half the volume.
- Use a speaker cable, not an ordinary instrument cable.
- The SPEAKER output must not be connected to a normal amp or line input.
