What is the 1/8 rule for headphone impedance?

The 1/8 rule states that the amplifier output impedance should be no more than 1/8 of the headphone impedance for flat frequency response. For 32-ohm headphones, the amp output impedance should be 4 ohms or less. Higher output impedance can alter frequency response, especially with multi-driver IEMs.

What is damping factor and why does it matter?

Damping factor is the ratio of headphone impedance to amplifier output impedance. A higher damping factor means the amplifier has better control over the driver. A damping factor of 8 or higher (matching the 1/8 rule) ensures the amp can properly control the driver and maintain flat frequency response.

Why do some headphones have high impedance (250-600 ohms)?

High-impedance headphones (like the Beyerdynamic DT 880 600-ohm) were designed for professional equipment with higher output impedance. They are less sensitive to output impedance variations, tolerate longer cable runs, and can sound more detailed. However, they require more voltage to reach the same SPL.

Can high output impedance damage my headphones?

No, high output impedance will not damage headphones. However, it can cause frequency response colouration (especially with multi-driver IEMs where each driver has different impedance at different frequencies), reduced bass control, and slightly lower maximum volume.

AudioCalcs

Impedance Matching Calculator — Headphone & Amp Damping Factor

Calculate damping factor and output impedance matching for headphones and amplifiers.

Headphone Impedance

Amplifier Output Impedance

How We Calculate This

Damping Factor

Damping Factor = Headphone Impedance / Output Impedance

1/8 Rule

Output Impedance ≤ Headphone Impedance / 8

This ensures a damping factor of at least 8, which keeps frequency response variations below approximately 1 dB.

Voltage Division Loss

Loss (dB) = 20 × log10(Z_load / (Z_load + Z_source))

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard formulas. Always verify results for critical applications.