It seems that everyone is bound to have different results, being that we are all listening to various Sansui amps on various brand/model speakers,
as well as listening to all types of music at certain volume levels and so forth, be it phono (vinyl), cd, streaming, etc....
Thus, just considering one spec alone, 4 ohms, is not really alot to go on, especially when impedance is NOT a constant value, and in reality,
it varies higher & lower throughout the audible 20-20Khz frequency range, and of course, its the low dips below 4, that are the main concern,
for which its useful to see the impedance graphical chart for the speaker you happen to own, which will provide this information.
It would be convenient if we could apply the same principles of a home electrical system to an audio setup, being that the typical home runs on 15 ampere circuit breakers, and if that level of current is exceeded, it will cause a breaker to trip (open), and shut off as a protective device to avoid a fire hazard since excess current equates to excess heat, which equates to melted wires and so forth.
For example, you might find that when running a coffeemaker and the microwave simultaneously, it could approach the 15 amp limit, as an analogy to running two pairs of speakers simultaneously which causes higher current on the amplifier due to the impedance drop, and can cause an amp's protection device to activate in order to prevent internal damage such as blown power out transistors, etc..
It depends on the devices, just like it depends on the speakers being used, for some things you can connect multiple devices such as numerous lightbulbs into a power strip and be ok, whereas only two 1800 Watt hairdryers should be enough to trip a breaker.
In the case of the home electrical system, the current can be measured with a Clamp on. You would just need to strip the insulation off of the extension cord in order to isolate the hot and neutral wires so that the clamp-on can read one of them to get the ampere measurement. (obviously you dont want to damage the actual cord of the appliance, so you could just plug into another ext cord and use the ext cord to strip the insulation).
Having described all of this, I was wondering if something similar can be done with an amp and speakers. Can we do a test and hook up a pair of 8 ohm speakers, and then a pair of 4 ohms, and plug the amp's cord into an ext cord, and strip the insulation and take a measurement with the clamp-on to compare how much the current increased, to get an idea of how close the amp is to having its protection circuit triggered?
As I try to give it more thought, it might be more complicated with audio- unlike just a lightbulb which has a filament that behaves as a resistor regardless of ac or DC, , speaker crossover circuits have inductors and caps, which have impedance and behave much differently.
For example, in trying to better grasp the concept of Impedance vs resistance, and ac vs DC, its very easy to see that if we have two 8 ohm resistors in series, they add up to 16 ohms, whereas if we have an 8 ohm resistor and an 8 ohm inductor instead, they dont add up to 16 ohms, its more like 8 + j8, which only folks who have taken circuit theory classes and are familiar with polar and rectangular coordinates from mathematics would understand.
Thus, why impedance over the 20-20K range and how a vintage Sansui amp would respond seems hard to analyze/predict.
Well, if you look at each Sansui amp's operating manual, or the back of the speaker terminals, it will usually state the impedance range, and a good number of them would seem to accomodate 4 ohms, otherwise I dont see why they would have a 2nd set of terminals instead of just one, as if everyone is expected to have 16 ohm speakers so that if both A & B are used simultaneously, then it equates to an 8 ohm load.
But in the real world, I would just say- go by the overall reputation of your speakers which is easy enough to find out online and from the experiences of others. Obviously, if the speaker is an Infinity Kappa 9 "amp killer", then common sense should indicate that a real robust amp is necessary, but if the speakers dont have any abrupt dips and are efficient, etc, should be ok, if any doubts, just start gradually, play the amp at lower volume for a while and see how it goes, then turn it up a bit and so forth and monitor it, and see if it continues to be ok, if so, should be good.
