H21 LB 15 Sag Full-Range drive unit.

High efficiency 21cm (8")



Improved version of the famous H21 LB 15 using:

- a new and unique voice coil made from silver wire insulated with 15 micrometer silk. This avoids almost completely the production of MDI ( Micro Discharges of Interface ) and other interferences.
- a lighter paper cone
- a brass phase plug
- a lower Fs

High efficiency 21 cm ( 8" ) wide range unit, paper cone, SN12 lead-free bronze basket and ring, pole pieces are made of very soft steel with less than 0.20 % carbon in a pot shape with central ALNICO 3SC magnet : the full magnetic field is located within the gap and protected from other magnetic interferences like TV emissions.

Each driver part is thoroughly controlled and measured all along the manufacturing process. Each driver is put through an intensive pre-running and then measured in order to match pairs with a maximum tolerance delta of 0,1gr. on mobile equipment mass, 0.1 Ohms on d.c. resistance, 1Hz on resonance frequency. These matched drivers are then numbered and provided with a lifetime warranty ( first owner ) .


ø voice coil = 25 mm
h = 8 mm 2 layer silver-silk
M = 4 gr
dB = 98
G = 1,2T alnico 3SC
Power = 15 W rms
fs = 40 Hz
re = 12,8 Ohm

Qes = 0,65
Qms = 6,10
Qts = 0,59
Vas = 97 litre
Z = 15 Ohm
Zmin = 14,4 Ohm
Zmax = 155 Ohm
D = 176 mm

hole diametre = 202
5 screws ø 5 x 72°
on r = 108
Net weight = 4,2 kg
Packed weight = 6 kg





These values are indicative only and are representative of typical measurements in our anechoic chamber. One should always keep in mind that the naturalness of reproduction, balance and musicality cannot be described by those measurements and only partly derive from them.
For improving performance and manufacturing quality, Phy-HP reserves the right to make changes in specifications without prior notice.