Reference earphones

Posted on Feb 7, 2014

There are 3 basic types of earphones, each with their set of benefits and problems. Small transducers that are inserted into the auditory canal. This leaves only a few millimeters of a mismatched acoustic transmission line between the vibrating diaphragm of the transducer and the eardrum. This cavity should be sealed or have very slow air leakage to the outside world in order to prevent bass roll-off.

Reference earphones
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This also provides a high degree of isolation from ambient sounds. To achieve this requires that the canal phones have been slightly wetted with water before insertion. They tend to be uncomfortable but can be accurate transducers if the transmission line resonance has been equalized. Their bass response is highly dependent upon the seal of the ear canal. The ear cushion wraps around the pinna so that the transducer and the outer ear form a sealed cavity. The internal geometry of this cavity varies between individuals, which makes measurements of headphones unreliable. The cavity has multiple resonances, which makes equalization difficult. The seal of the cavity affects the bass response and the resonances. They give isolation from ambient sounds and are much more comfortable than canal phones, but I begin to sweat wearing them and they tend to be heavy. I have no use for them. Here the ear cushion rests lightly on the pinna and any cavity formed between transducer and pinna is relatively open. Cavity resonances are attenuated, but there is also little isolation from the outside world. they are easily equalized. The problem is with the bass response. They are usually light and comfortable to wear. I place earbuds in this category. Inconsistencies of their placement in the outer ear and a lack of seal makes the bass and higher frequency response unpredictable. They are popular but not useable as reference phones. They might...

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