Model 3.8

In designing the Pietra Model 3.8, the goal was to retain the essence of the Model 3.10 while reducing the footprint and providing a bass response more suitable for smaller listening spaces. The goal was achieved in 2016, enabled by the use of a new 20cm aluminum cone bass driver well-suited to the target 50 litre enclosure volume. The proven transfer functions from the 3.10 required only minor corrections to account for the reduced baffle area, whilst maintaining uniformity of the radiation pattern at extreme horizontal listening angles. The Model 3.8 uses the same world-class midrange as our Model 3.10, with a neodymium ring magnet motor system and underhung voice-coil. Neodymium magnets provide a field that is roughly 10 times stronger than ferrite magnets, and generate the high flux-density required to make an underhung coil feasible. The underhung design ensures the magnetic flux seen by the voice coil is constant over the excursion range, thereby reducing nonlinear distortion.

The 3.8 prototype served as a testbed for development of a new transducer modeling algorithm that is the subject of ongoing research. This algorithm combines (1) an advanced electrical motor model developed at Scan-Speak that describes the transition from inductance to semi-inductance with (2) a suspension compliance and damping model that describes viscoelastic creep. This approach corrects deficiencies in the traditional equations for box modeling that are implemented in low-frequency modeling software. Some aspects of this research were presented at ALMA 2017, and more theoretical aspects have been submitted for publication in JAES (Journal of the Audio Engineering Society).


hf transducer 2.6cm, Beryllium done
midrange transducer 12cm, neo motor
bass transducer 20cm, aluminum cone
sensitivity 86dB @ 2.83V, 1m
minimum impedance 4.6 Ohms @ 92Hz
crossover frequencies 400Hz, 2.5kHz
weight 120kg
dimensions (hwd) 116cm x 33cm x 36cm
cabinet material black galaxy granite

$13,500 USD      Sales