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

Interesting thing is you need amp and speakers together to make sound. Either one alone says nothing. So you can judge each on paper or do measurements but absolutely cannot judge how one sounds exactly without the other. Only the two together and each pairing sounds different.

Then as if that’s not bad enough there is this thing called room acoustics that means the same amp and speaker pairing will sound different depending not just on room but location in it.

However natural selection is at work. Only the strong will survive no matter what.

For best results, practically, in most cases, I think one has to first match speakers to the thing you have least control over changing (the room) and then match amp to speakers.

The room is the biggest determining factor IMHO that determines the viable approach or approaches for getting the best sound results. I’m technology and product agnostic when it comes to good sound from there.

Of course if one is willing or able to do extensive sound treatment and tweaking of the room that opens up even more ways to skin the cat.

Each case is different. No one solution always works or sounds best in the end.  Budget and funds are almost always a constraint.

If one is more biased towards using specific technologies, whatever that may be, that’s fine as well. The only thing that really matters is people like and enjoy their endeavors.

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.

Actually ports in ported speakers are perfect examples of why low impedance is harder to drive.     Impedance at port frequencies is always low.  Check any ported speaker impedance curve and see.   After all the port itself has little or no physical resistance/impedance.   Air blows right through largely "unimpeded".    An amp driving the ported speakers well will result in a stronger air flow. One that cannot drive it well will result in little or no air flow meaning the port is not being utilized well to move air at the lower frequencies that it is intended to enable. 

Ports in ported designs are always a major factor it seems. 

It’s all about the bass, about the bass,. Not the...

well it’s also about size and cost actually.

The reality is low power tube amp lovers have limited speaker choices at least if bass extension matters. Still good ones out there though if a low power tube amp is what one chooses to build around.

Making music especially bass is a lot of work. Somehow combo of amp and speakers must be up to the task else results suffer in comparison. A nice high pressure shower makes for a much better clean. The actual amount of water used might still vary widely though.

I think the trend towards speakers with lower impedance corresponds to the trend for speakers to be smaller yet more full range to fit into people’s lifestyle. Also as we know from experience the best sounding gear is not always the ones that measure lowest in distortion. Lower impedance tougher load speakers just means amps must work harder. Some are able do that much mbetter than others. Newer more efficient amp technologies like Class D perhaps do it best. Class D offers a much larger higher pressure "garden hose" for your speakers.   For example I have 500 w/ch class d amps that can deliver almost 40 amps of current  that are about the size of a shoebox.    My harder load speakers shine and easily surpass my smaller easier load ones with these.