Why are low impedance speakers harder to drive than high impedance speakers

If one did a study of speaker size versus nominal impedance for speakers with good bass extension, I suspect an correlation would be seen between speaker size and impedance. Also a correlation between size and efficiency for certain.

Bottom line is way more people these days prefer speakers with smaller form factors that still do extended bass well to fit into their lifestyle and that puts more demand on the amps to do the work needed. Granted that there is also a motivation for makers to make speakers smaller as well to keep costs down and profits up.

Its much harder technically to get a lot of good sound out of a smaller package than a larger one. It requires higher quality drivers capable of more output with low distortion be designed. A lot of speaker innovation these days revolves around exactly that. Smaller speakers with better sound is the holy grail to a great extent. Some do it much better than others. Granted though it does COST more to make a larger speaker of certain high quality than a smaller one. more of anything always costs more.

Add in that amps are more efficient than ever and can do more work with smaller packages and less electricity and the story is complete.

Lower power tube amps SETs in particular but OTLs and others as well have to rely more on the speakers to pick up the slack and do the work more efficiently. That’s the speakers problem then, not the amps. But all buyers need is for the amp speaker combo together to be up to the task however that is achieved.

So not really a fair thing to judge the world from the perspective of low powered tube amps. Its a different paradigm as Atmasphere accurately refers to it that one can choose from if it fits their needs better, but obviously only a small % of even high end audio enthusiasts choose to go that way for good reason just as some do. Those are the facts. Its nice to have a choice of two different ways to do about things and still get excellent results. One side will never be made to see things the others way. Each is focused on doing things a different way for good reasons. Each approach will have its pros and cons compared to the other but pundits will naturally attempt to stage the comparison in terms favorable to their preferred approach.

Atmashere, the OP said nothing of ESL's. I did make mention of :  "Most typical speakers....".

Perfectly stated Charles. Many roads...

Dave

you took my statement out of context. Here is what I actually said:

Yes- it was not to contradict you, but to use the phrase as a talking point, as I see that approach recommended a lot. Then later people sell off the gear in search of that holy grail... I think if you start with the grail first you're less likely to sell and waste the cash.

Atmashere, the OP said nothing of ESL's. I did make mention of : "Most typical speakers...."

Correct- in fact by 'most typical' is about 95% of the market. In high end, its still about 85% and so is 'mostly accurate' :)

For those outside of that percentage (Charlesdad's speakers are box speakers but they are an example) that voltage thing just does not work. This is entirely due to the designer wanting the speaker to work with a particular kind of amp. In Charlesdad's case, the speakers were originally envisioned on a set of our M-60s and later that manufacturer started making SETs, which work much the same way. SETs in general are much happier on higher impedance loads despite often having 4 ohm taps and they tend to make constant power rather than constant voltage owing to zero loop feedback.

In a tube amp, the 4 ohm tap is not an efficient way to use the output transformer, which often means not only less power (lost due to heat) but also less bandwidth, sometimes up to an octave lost on the bottom end. So its often really worthwhile to avoid low impedance speakers with tube amps even if you have the taps on the output transformer!