Vintage amplifier specifications

I've noticed when I read vintage amplifier specifications, and by vintage I mean 70's,80's maybe 90's, I do not see power output specified at 4 ohms. Did those older amplifiers not do well on 4 ohm speakers so leave that information out or was it not considered a a matter of interest to the buying public. Maybe something else?


I have a vintage Marantz and a vintage Sansui, both stereo receivers. They have main and secondary speaker terminals. This was to have your main speakers and then a remote pair in another location. Most of the units of that era did not have a design that employed multiple impedance outputs ( 4,8,16 ). So they were rated for power at 8 ohms and would state acceptable load 4-16 ohms. Sometimes we’d stack two pairs of speakers and run A and B, or wire two pair in parallel. We were just kids then , but we’d listen for distortion and clipping. New gear has a higher degree of engineering.

So two pair of speakers weren't necessarily amp killers in the days of yore so perhaps those old amps were more tolerant with beefier construction than I suspected.

Now days the low impedance load handled by amplifiers are selling points or bragging rights for manufacturers. Who doesn't love an amp that can "double-down"?

Many amps from the 80’s were rated not only into 4 Ohms but sometimes onto 2 Ohms as well. Big iron from Classe’, Krell, Levinson, Rowland, Threshold, etc.. Some even had more rated into lower impedances then than later on.

2 ohm impedance was the threshold for most designs of that vintage.  Even the original NAD 3020 would tolerate 2 ohm until driven hard and smoked.  Unsound is correct about big iron.  Include Yamaha, Accuphase, GAS and Luxman.

There were speakers of this era that really needed amps capable of delivering into low impedances, such as Apogee, Infinity, Thiel, etc..