8 ohm speaker hooked up to 4 ohm post ?

Not every speaker maker measures their speakers the same way... with the same measuring equipment... or in similar rooms... I don’t think. Nor do I believe every maker uses or has anechoic chambers. Not all have the resources to do so either. Botique speaker makers can and do, still produce very good units however.

Therefore, one seldom knows what's what unless you go by Stereophile's measurements... and John doesn't measure every speaker set ever made.

If you aren't prone to pushing the volume knob all the way to the right, trying another set of output taps shouldn't pose much of any issue.

Given my lead in statement here, it would seem one should try other output taps if there is any doubt what ever, and try what’s available on their tube amps, to see what is best for their situation. Without so doing, mistakes could well be made... and or wholesale changes could ensue too... eg., swapping out amps, speakers, etc.

Two examples:
BW 9NT 90-91db, 8 ohm nominal. Why do these units usually require higher powered amps with such attractive numbers being presented by the manufacturer? I once owned both the 7NT & 9NT and both had similar specs… both responded best to amps which had loads of power available… eg., BK220 Ref, Krell KAV 250. I used other amps under 200 wpc with far less positive results. I quit trying amps once the Krell was on board.

Silverline Sonata IIIs... reportedly 93 db @ 8 ohms... not dropping below 6 or 7.
Sorry but I must disagree with those specs too, by virtue of practical applications.

I thought it was due to my mono block tube amps for a little while, but then began to drive other speakers on hand whose specs were verified by the manufacturers and practical use.

, I don't know for sure about the impedances of any speaker as I’ve never measured them, but the ‘easy’ to run Sonatas work best off the 4 ohm taps IMO. There was no loss of dynamics, no real change in loudness, but they sounded thin and edgy on the higher taps... little if any bass and no body worth mentioning.... like they were somewhat starved for power. This assessment is not inclined to a listening preference at all. Simply a matter of fact.

With a couple solid state amps, which have no such choice of out put taps, they play fine, and only the differences between ss and tubes are then realized. The thinness and tilted up sound was gone.

Additionally, I've connected the tube monos to other 8 ohm speakers I have on hand, and I've discovered no such issues. Put them onto the appropriate taps and all is well.

Consequently I feel the amps are doing fine using either output tap accordingly to the presented load.

The only speakers I own which differ from these steps are my sonata IIIs which act far more like 4 ohm speakers than 8 ohm speakers under real world situations.

One other note many have already noticed I’m sure, is that in regard to speakers, the more drivers a loudspeaker system has the more likely they will be of lower impedance.

Tonight, just to reconfirm, I'll reconfigure the Sonatas onto the 8 ohm taps and get back here with the results.

Until some consistency in how speakers are to be measured, amongst loudspeaker makers becomes evident, and no one embelishes the numbers perhaps, I feel the end user should find out for themselves which output is best suited to their given situation. Albeit some consistency in the manufacturing portion too.

BTW, there are any number of opinions on many manufacturers’ products consistency with regard to this “cottage industry at it’s finest”, routinely and that sole item may account for such apparent exceptions.

Hotsauce's comments are correct if the volume control setting is identical for the two different configurations. However, it will not be, because the listener presumably will adjust it to reflect the lower output voltage on the 4 ohm taps and the higher output voltage on the 8 ohm taps.

Also, keep in mind that speakers are probably damaged more often by underpowered amplifiers than by overpowered amplifiers. The clipped waveform that can result from an underpowered amplifier being driven hard contains high frequency spectral components not present in the original music waveform, which the speaker's crossover will route to the tweeter, not uncommonly resulting in damage to it. The chances of something like that happening would be increased by connecting an 8 ohm speaker to the 4 ohm tap, because the reduction in volume may tempt the listener to increase the volume control setting such that musical peaks exceed the voltage swing that the 4 ohm tap is capable of.

That said, as long as you exercise reasonable caution with the volume setting you are very unlikely to damage anything either way. But given the impedance curve of the particular speaker, which goes below 8 ohms only briefly, and stays well above it at many frequencies, I would expect the 8 ohm tap to provide best results.

Regards,
-- Al

It won't hurt a thing..... try it.... they may sound better.

Adding to my previous post, if you connect a true 8 ohm or so speaker to the 4 ohm taps, you will be increasing the impedance seen in the plate circuits of the output tubes (on the primary side of the output transformer). That will not harm anything, but will tend to move the operating point of the tubes away from what the designer intended.

Most "8 ohm speakers" have actual impedances which are lower at most frequencies than yours, and also dip well below 8 ohms at many frequencies. Given that your speakers are atypical in that respect, I would not generalize too readily from the positive results others have sometimes reported when they connected to the 4 ohm taps.

Regards,
-- Al

I have a similar question to the OP. When I called the dealer of Prima L. last year to buy the PL2 model, the dealer told me to connect my previous 8 ohm speakers (Totem Sttaf) to the 4 ohm taps! He told me the speakers will sound better!? I did not ask why, and until now, I still don't know why!