Handbook for Sound Engineers

Personal Monitor Systems 1423

and are difficult to try before buying since they are
made specifically for one person’s ears. The procedure
for getting custom molds involves a visit to an audiolo-
gist. The audiologist makes an impression of the ear
canals by placing a dam inside the ear to protect the
eardrum, and fills them with a silicone-based material
that conforms exactly to the dimensions of the ear canal.
The impressions are then used to create the custom
molded earphones. Another visit to the audiologist is
required for a final fitting. Manufacturers of custom
molded earphones include Ultimate Ears, Sensaphonics,
and Future Sonics, Fig. 37-11

A third type of earphone is the universal fit, Fig 37-

12. Universal earphones combine the superior isolation
    and fidelity of custom molded designs with the out-of-
    the-box readiness of ear-buds. The universal nature of
    this design is attributed to the interchangeable sleeves
    that are used to adapt a standard size earphone to any
    size and shape of ear canal. This design allows the user

to audition the various sleeves to see which works best,

as well as being able to demo the earphones before a

purchase is made. The different earphone sleeve options

include foam, rubber flex sleeves, rubber flange tips,

and custom molded. The foam sleeves resemble regular

foam earplugs, but with a small hole in the center of the

foam lined with a tube of plastic. They offer excellent

isolation and good low-frequency performance. On the

downside, they eventually get dirty and worn, and need

to be replaced. Proper insertion of the foams also takes

longer—relative to the other options—since the

earphone needs to be held in place while the foam

expands. For quick insertion and removal of the

earphones, flexible rubber sleeves may be a good

choice. Made of soft, flexible plastic, flex sleeves

resemble a mushroom cap and are usually available in

different sizes. While the seal is usually not as tight as

with the foams, rubber sleeves are washable and reus-

able. The triple-flange sleeves have three rings (or

flanges) around a central rubber tube. They are some-

times referred to as Christmas trees based on their

shape. The pros and cons are similar to that of the flex

sleeves, but they have a different comfort factor that

some users may find more to their liking. The fourth,

and most expensive, option is custom sleeves. The

custom sleeves combine the relative ease of insertion

and permanency of flex sleeves with the superior

(depending on the preference of the user) isolation of

the foams. The process for obtaining custom sleeves for

universal earphones is very similar to that of getting

custom molded earphones; a visit to an audiologist is

required to get impressions made. Custom sleeves also

give the user many of the same benefits as custom

molded earphones, but usually at a lower cost, and with

the added benefit of being able to interchange earphones

Figure 37-10. One stereo mix.

Figure 37-11. Custom molded earphones. Courtesy Sensa-
phonics.