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Definitive resource for headphone design?

Dogen

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Happy upcoming new year y’all!
I’ve gotten a copy of Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms by Floyd Toole, and have been educating myself a little on all the factors that go into loudspeaker measurement and design. Sean Olive has done great work as well. Is there a definitive book or resource on headphone design?

The whole field seems to be in its infancy, to this newbie. It seems that most headphones don’t use passive filtering or crossovers, so it’s all down to driver selection and physical design; I could be wrong! Looking at the wide range of performance and price, not always well correlated, I’m wondering what factors really go into headphone design, and why an essentially flat pair would need to be expensive. Is it down to development time and testing? It seems a well performing pair of speakers can be built for not much money. So why the wide variance in performance at every price?

Do we really want flat response, or is some other goal more desired? What effect does the shape of individual ears have? Is headphone design as mature a science as speaker design?

I’d appreciate any pointers to resources that will help me better understand the design and voicing of headphones.

Thanks,
Bob
 

maverickronin

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Is headphone design as mature a science as speaker design?

If it is, it's certainly not well known in the same way.

I get the the impression that it's trial and error for most manufacturers with some of the larger ones having their own black arts they pass down internally.
 

solderdude

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Voicing headphones is done by:
driver design (diameter, motor design, voice-coil and coupling, usage of 'cone' materials)
damping on the rear of the driver and the magnet hole (for dynamics).
Amount of air behind the driver.
Amount of air in front of the driver.
Driver ear distance.
Driver-ear angle.
Driver position opposite the ear.
Damping on the front side.
Porting on the rear side.
Porting on the front side (paper stuff around the driver) or small ports (covered or not)
Baffle design.
Pad design (materials, thickness, diameter, shape).
The goal the manufacturers have in mind (target audience)
Sound signature they have in mind
Financial reasons
Trial and error
Research
For Planars there are factors that are related and other factors that don't work like dynamics.
For electret, electrostat and other driver types (Ceramic, ribbon) and IEM's other things apply.
For closed headphones other constructions is needed than for open headphones.
On-ears yet have different properties to play with.

It's a mix of all these factors + looks.
You can't really say this part does this and that part does that.

It differs completely from designing speakers.

As maverickronin already said... it's a bit of voodoo and black art. In other words... lots of experience is needed as well as capable designers, trial and error... designing, building prototypes, measure/listen, back to the drawing board and repeat till you have created something that some people may like, try to make large amounts cheaply and make a profit. This often means cutting corners.

It's a lot harder than building speakers and electronics.
Speakers are easier to design 'flat' on axis on 1m but depend on room properties and dispersion patterns.
Designing electronics is all about good practices (experience/knowledge) and picking the right components for the design (experience/knowledge)
For headphones different acoustics than speakers/microphones are valid which makes making an 'audibly neutral' headphone difficult.

To modders and owners the beautiful and fun task to tweak a product more to their liking.
 
Last edited:

Headphonaholic

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Voicing headphones is done by:
driver design (diameter, motor design, voice-coil and coupling, usage of 'cone' materials)
damping on the rear of the driver and the magnet hole (for dynamics).
Amount of air behind the driver.
Amount of air in front of the driver.
Driver ear distance.
Driver-ear angle.
Driver position opposite the ear.
Damping on the front side.
Porting on the rear side.
Porting on the front side (paper stuff around the driver) or small ports (covered or not)
Baffle design.
Pad design (materials, thickness, diameter, shape).
The goal the manufacturers have in mind (target audience)
Sound signature they have in mind
Financial reasons
Trial and error
Research
For Planars there are factors that are related and other factors that don't work like dynamics.
For electret, electrostat and other driver types (Ceramic, ribbon) and IEM's other things apply.
For closed headphones other constructions is needed than for open headphones.
On-ears yet have different properties to play with.

It's a mix of all these factors + looks.
You can't really say this part does this and that part does that.

It differs completely from designing speakers.

As maverickronin already said... it's a bit of voodoo and black art. In other words... lots of experience is needed as well as capable designers, trial and error... designing, building prototypes, measure/listen, back to the drawing board and repeat till you have created something that some people may like, try to make large amounts cheaply and make a profit. This often means cutting corners.

To modders and owners the task to tweak a product more to their liking.
I agree 100% with this. From my experience in modding there are so many factors with headphones, pads for instance can drastically change the sound. Many probably think pads are for comfort only but that is not the case. Some headphones sound like garbage with the wrong pads and sound great with others. I've experimented with dampening mods with the Fostex T50RP mk2 and it too can make some noticeable changes.

In my opinion there are some similarities with speaker design (I've never designed speakers but from my car audio experience I know the basics). The air between your ear and the driver I always liken to the room in which you place a speaker (and where you sit). The cup of the headphone being the speaker box analogue. It's obviously not that simple but some stuff carries over. I guess at the end of the day when designing a headphone you are more or less not only designing a speaker and it's enclosure but the room it will live in.
 
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