3-pole (two black loops) 4-pole (three black loops)

The available 4-pole phones; all made by Sharp

Earbuds

HP-SS30-S (silver) retail price in Japan, 2,200 yen.

SS-30 stats:
Drive diameter, 14.5mm
Impedance, 32 ohms
Max.allowed output, 10mW
Sensitivity, 97dB/mW
Frequency response, 20~20,000Hz

HP-SM30-S (silver) retail price in Japan, 2,200 yen.

SM-30 stats:
Drive diameter, 16mm
Impedance, 32 ohms
Max. allowed output, 10mW
Sensitivity, 95dB/mW
Frequency response, 20~20,000Hz

HP-SS30 (right) next to HP-SM30 (left)

Clip-on

HP-MD1-S (silver) retail price in Japan, 2900 yen.

HP-MD2-P (pink) retail price in Japan, 2900 yen.

HP-MD2-A (blue) retail price in Japan, 2900 yen.

all 3 (silver, pink, and blue)

MD-1 & MD-2 stats:
Drive diameter, 30mm
Impedance, 32 ohms
Max. allowed output, 20 mW
Sensitivity, 105dB/mW
Frequency response, 20~20,000Hz

HP-MD5-S (silver) retail price in Japan, 5000 yen.

MD-5 stats:
Drive diameter, 30mm
Impedance, 32 ohms
Max. allowed output, 50mW
Sensitivity, 102dB/mW
Frequency response, 20~20,000Hz

inner ear

HP-MD33-S (silver) retail price in Japan, 3500 yen.

HP-MD33 stats:
Drive diameter, 9mm
Impedance, 32ohms
Max. allowed output, 20mW
Sensitivity, 120dB/mW
Frequency response, 20~20,000Hz

hanger

HP-MD90-S (silver) retail price in Japan, 12,500 yen.

HP-MD90 stats
Drive diameter, 16mm
Impedance, 32ohms
Max. allowed output, 20mW
Sensitivity, 95dB/mW
Frequency response, 20~20,000Hz

All 4-pole 'phones come with a 3-pole to 4-pole converter chord; without it, plugging 4-pole phones into a 3-pole socket will only provide a signal to the left channel.

User experience:

SS30 & SM30: These are stock buds that are available at the retail level. They get the job done.

MD1 & 2: The 1's & 2's have a clean detailed sound. They are louder than the 5's when compared at
equal volumes. I would use them more but the plastic ear-hangers do not keep the 'phones in
place when I walk. During the cold weather, it is not a problem because I wear a stocking
cap over them that keeps them in place.

MD5: This set is more expensive than the 1's & 2's but I think it is for the housing quality rather than the
speaker quality. The rubber-coated metal hangers do hold the 'phones in place better than the
plastic hangers of the 1's & 2's but the sound is not as loud. I do hear the same amount of detail
in the 5's as I do the 1's & 2's but I have to turn the volume higher to match the sound level.

MD33: A very clean and detailed sound; these are the best sounding of the available 4 pole 'phones.
It has taken me several months to become accustomed to wearing inner-ear phones and I
only use them for riding planes and trains; at home I use 66 eggos. I find they aren't good for
walking because they can block out too much outside noise and they are prone to losing their
seal from the vibrations of body motion, whether it be walking or turning my head.

MD90: A strong sound and as detailed as you can expect from earbuds. These are my favorite buds of
any 3 or 4 pole buds I own and I use them with both 3 and 4 pole units. They are lightweight,
they sound good, and the ear hangers keep the buds in place.