A little history, a little electricity, and why ohms matter
Look at the specifications for a pair of headphones and you'll find a number followed by a symbol that looks a little like a horseshoe: 32 Ω, 80 Ω, 300 Ω.
It's easy to skim past it. After all, there are more obvious things to consider. How do the headphones sound? Are they comfortable? Do they reveal the details you're looking for?
But that small number tells you something important about the relationship between your headphones and the amplifier driving them. It's called impedance, and understanding it can help explain why some headphones work beautifully with one amplifier and less convincingly with another.
The concept isn't new. In fact, impedance has been part of the story of electrical sound reproduction since the earliest days of telephones and radio. To understand why it matters today, it helps to start at the beginning.
Before headphones were for listening
Long before personal listening became a familiar part of everyday life, headphones were working tools.
Telephone operators used them to monitor conversations. Radio experimenters relied on them to hear faint signals. Early radio receivers often needed headphones that could reproduce a signal using the relatively limited electrical power available from the receiving circuit.
These weren't the headphones we know today. Many early designs used electromagnetic receivers, and some had very high electrical impedances compared with modern consumer headphones. Impedances in the thousands of ohms were not unusual in early radio headphones.
That made sense for the equipment of the time. The receiver, the circuit driving it, and the headphones had to work together as a system. The goal wasn't simply to make a headphone with a particular number on its specification sheet. It was to convert a weak electrical signal into audible sound using the technology available.
As radio and audio electronics developed, so did the ways engineers amplified and delivered signals. Vacuum tubes made it possible to amplify signals more effectively, while transformers helped connect circuits with different electrical characteristics. Headphones evolved alongside these changes.
Eventually, headphones moved from the operator's desk and the radio enthusiast's workbench into the home, the recording studio, and the listening room. Their designs diversified, too. Some were made to work with portable devices, others with studio equipment, and others with dedicated headphone amplifiers.
That history left us with a wide range of impedance ratings—and a useful reminder that headphones have never been designed to work independently of the equipment around them.
What impedance actually means
In simple terms, impedance describes how much a circuit opposes the flow of alternating current. It's measured in ohms, represented by the symbol Ω.
Resistance is part of impedance, but impedance also accounts for the effects of capacitance and inductance. These effects can change how a circuit responds at different frequencies, which is one reason impedance is particularly relevant in audio.
Headphones convert an electrical signal into movement that produces sound. Their drivers present an electrical load to the amplifier, and that load influences the voltage and current the amplifier must deliver.
A headphone rated at 32 Ω generally draws more current than a 300 Ω headphone when both are supplied with the same voltage. Conversely, the 300 Ω headphone generally requires more voltage to reach the same electrical power level.
That's the basic trade-off: lower-impedance headphones tend to demand more current, while higher-impedance headphones tend to demand more voltage.
The word tend matters here. Impedance alone doesn't tell you how loud a headphone will play, how much power it needs for a given listening level, or how good it will sound. Sensitivity matters, too, along with the amplifier's capabilities and the headphone's design.
The number is useful, but it's only one part of the picture.
Low versus high: Is one better?
Not inherently.
Modern headphones cover a broad range of impedance ratings. Many portable and consumer models are designed around relatively low impedances, often somewhere between 16 and 80 Ω. Some studio headphones use ratings around 250 Ω, while certain high-impedance models are rated at 300 Ω or more.
These are common examples, not strict categories. There is no universal boundary separating a portable headphone from a studio headphone, and impedance alone doesn't determine a headphone's intended use.
Lower-impedance headphones can be easier to drive from devices with limited voltage, provided the amplifier can supply enough current. That's useful for phones, laptops, portable players, and many modern headphone outputs.
Higher-impedance headphones may suit amplifiers capable of delivering greater voltage swing. Some were designed with traditional studio equipment and amplifier circuits in mind, where those electrical characteristics made sense.
Neither approach guarantees better sound. A well-designed 32 Ω headphone can be excellent. So can a well-designed 300 Ω headphone. Their impedance ratings simply describe different electrical requirements.
Why the amplifier matters
An amplifier's job is not just to make a signal louder. It also needs to deliver the voltage and current the headphones require, while maintaining control of the signal.
If an amplifier cannot provide enough voltage, a high-impedance headphone may struggle to reach the desired listening level. If it cannot supply sufficient current, a low-impedance headphone may place demands on the amplifier that it wasn't designed to handle.
There is another consideration: the amplifier's output impedance.
This is different from the headphone's impedance. Output impedance describes the electrical impedance presented by the amplifier itself. The relationship between the two can affect how much of the amplifier's output voltage reaches the headphones.
When an amplifier's output impedance is high relative to the headphone's impedance, the voltage delivered to the headphone can vary with frequency as the headphone's own impedance changes. Depending on the headphone, this can alter frequency response.
For many modern solid-state headphone amplifiers, a low output impedance is desirable because it helps maintain consistent electrical behavior across a range of headphones. A commonly used guideline is to keep amplifier output impedance below one-eighth of the headphone's nominal impedance, although this is a rule of thumb rather than a universal requirement.
Some tube amplifiers behave differently. Their output stages and output transformers may be designed around particular load ranges, which is why the available output connections or impedance settings can matter.
The important thing is to consider the amplifier and headphones together, rather than treating either specification as a measure of quality on its own.
Sensitivity: The other half of the story
Imagine two headphones: one rated at 32 Ω and another rated at 300 Ω.
It might be tempting to assume that the lower-impedance model will always play louder. But that isn't necessarily true.
Sensitivity describes how much sound a headphone produces for a given electrical input. Manufacturers commonly express it as decibels of sound pressure level per milliwatt (dB SPL/mW) or per volt (dB SPL/V).
A headphone with higher sensitivity can produce more sound from the same input under the conditions used for its rating. A less-sensitive headphone may require more power or voltage to reach the same listening level.
The measurement unit matters, too. A sensitivity rating given per milliwatt isn't directly interchangeable with one given per volt without accounting for the headphone's impedance.
This is why impedance by itself is a poor shortcut for determining whether a headphone is easy to drive. A more useful assessment considers impedance, sensitivity, the listening level you want, and the amplifier's available voltage and current.
In practical terms, if you're choosing an amplifier for a particular pair of headphones, start with the manufacturer's recommendations and check that the amplifier can comfortably meet the headphone's requirements.
Where tubes and transformers enter the picture
Vacuum tubes have their own electrical characteristics. Many tube circuits can provide useful voltage gain, but their output stages don't always behave like the low-output-impedance circuits commonly found in solid-state amplifiers.
Transformers offer one way to bridge that difference.
An output transformer can match the electrical characteristics of a tube output stage to the load it is intended to drive. Its winding ratio affects the relationship between voltage, current, and the impedance reflected from the connected load back into the circuit.
That last point is worth understanding. The transformer doesn't change the headphone itself. Instead, it transforms the load as seen by the amplifier, allowing the circuit to operate within a range for which it was designed.
This is one reason output transformers have played such an important role in tube audio equipment for generations. Their design is part of how the amplifier delivers its signal to the load, not simply a component added at the end of the circuit.
In a headphone amplifier, the intended load range matters. A transformer and output stage designed for one range may not behave optimally across every possible headphone impedance. Matching the headphone to the appropriate output or setting helps the amplifier operate as intended.
Finding the right match
At Coffman Labs, the Lore offers headphone impedance options intended to accommodate a range of headphones, including models in the 8–32 Ω and 128–300 Ω ranges.
Those ranges provide a starting point for pairing the Lore with different headphones, but the nominal impedance rating isn't the only consideration. Sensitivity, the headphone manufacturer's recommendations, and the amplifier's specified operating range all matter when choosing the appropriate connection or setting.
If you're unsure where your headphones fit, check their specifications first. If the manufacturer provides guidance on amplifier compatibility, use it. And if you have questions about a particular pairing, it's worth asking before assuming that a higher or lower number is automatically the right choice.
The aim isn't to find the biggest number or the most specialized equipment. It's to give the headphones what they need to perform as designed.
A small number, a bigger picture
Impedance has been part of audio for well over a century, evolving alongside the equipment used to capture, amplify, and reproduce sound.
It's a practical engineering specification, not a ranking system. Higher impedance doesn't automatically mean higher fidelity. Lower impedance doesn't automatically mean easier to drive. And neither tells you whether you'll enjoy the way a pair of headphones sounds.
What impedance does provide is a useful piece of information about how headphones interact with an amplifier. Add sensitivity, output capability, and the design of the amplifier itself, and the picture becomes much clearer.
The next time you see 32 Ω or 300 Ω printed on a headphone box, you'll know there's a little more to that number than meets the eye.
It's not a score. It's part of the conversation between the headphone and the amplifier.