In the 1970s Hafler promoted "passive pseudo-quadraphonics", an inexpensive method of recreating ambient sounds at the rear from ordinary stereophonic recordings.
This passive method worked fairly well compared to the matrix decoders of the period, which attempted to reconstruct a surround sound field from a two channel recording.
Added later was the rugged DH-500 stereo amplifier, which was rated at 255 watts per channel and saw great success in home, studio, and live environments.
The new designs were less vulnerable to thermal runaway, allowing them to operate reliably at higher power without requiring expensive protective circuitry.
Hafler products were also a solid foundation for improvements through later upgrades and modifications, installed both by DIY hobbyists and small specialist audio companies.
Private Equity Firm, Regimen Partners, have acquired Radial Engineering Ltd. and its diverse catalog of brands that include Primacoustic, Tonebone, Reamp, Hafler, Dynaco, Jensen Transformers and Iso•Max.