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

So by and large, @atmasphere re-expressed my explanations for output impedance with a lot of discussion about tubes and distortion.

I may not agree with some of it, but the truth is, voltmeters don’t get pleasure from listening to music. Humans (and cats) do. So while I can say with precision that most solid state amps are more accurate, as far as measurements are concerned, I cannot tell you which you should buy instead of a boat, gun collection, or second home. :)

Tube amps behave and sound different, and some sound quite wonderful. If that’s the sound you are entranced with, you should go that route, but your range and choice of speakers will be different.

I agree that the idea of picking a speaker first is not the right way to go. You should find out which team you want to bat for first. Overall do you like very good solid state, or do you like tubes, and if either, what are their qualities you like?

Also, what is your real listening style? Do you really sit in a throne for 3 hours at a time in front of two speakers alone? Is it usually background music? Do you sit with your partner, friends, etc?

All these matter. :)

Best,


E

I think choosing speakers first has it's advantages. More so than with other components speakers need to be paired more carefully with the room in which they will be placed. More so than with other components speakers are the most colored components, and vary in sound more so than other components. As such it behooves one to make sure those colorations are the least offensive. Working backwards from the listening position will less likely box oneself into technological obstacles. 

I agree with Unsound’s post just above. And while I consider myself to be a "speakers first" kind of person, as he is, I don’t see that as being inconsistent with Ralph’s statements, including:

Often people have a preference about tubes and transistors- the speaker **must** be chosen to take that preference into account!!

Again, this all comes down to intention. Is your intention to get the system to sound as good as it can or is it more important to simply play loudly? If the latter [correction by Al], than some of the lower impedance speakers and higher power transistor amps will be of interest; if the former, then you will be very careful to be matching the speaker to the amplifier (and not the other way ’round) and most likely avoiding lower impedances in general.

As I see it this is saying essentially that what kind of amplification one anticipates using, now or in the future, is one of the major factors to consider in choosing a speaker. That is not quite the same as saying "amplifiers first," rather than "speakers first." Or so it seems to me.

It should also be noted, btw, that there are some speakers that will be equally suitable, or at least comparably suitable, for use with nearly all types of amplification. In those cases the resulting sonics will depend mainly on the intrinsic sonic characters of the speakers and the amp (as well as on speaker-room interactions, of course), with amplifier-speaker interactions contributing minimally if at all. Such speakers will typically have impedance curves that are relatively flat and do not have severely capacitive phase angles at any frequency, and combine relatively high efficiency with the ability to cleanly handle copious amounts of power.

Best regards,
-- Al

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.

 Ralph, you mentioned 'former' twice in the last part of your post.

Ach!

That should read:

Again, this all comes down to intention. Is your intention to get the system to sound as good as it can or is it more important to simply play loudly? If the latter, than some of the lower impedance speakers and higher power transistor amps will be of interest; if the former, then you will be very careful to be matching the speaker to the amplifier (and not the other way ’round) and most likely avoiding lower impedances in general.

-as Al corrected.

So while I can say with precision that most solid state amps are more accurate, as far as measurements are concerned

Erik, I don't think this statement is correct, and here's why. If you look at the specs, the lower distortion and apparent constant voltage characteristics of most solid state amps looks great! The problem is, that bit of paper ignores how our ears perceive sound.

This takes a bit to grasp! To give you some idea, most of us know that the ear employs a logarithmic approach to sound pressure. This is why we use the VU scale of decibels.

So take this concept, but apply it to harmonics. The ear seems to use something that looks very much like a logarithmic approach when it comes to how sensitive it is to harmonics- being less sensitive to lower orders and far more sensitive to higher orders on what looks much like an inverse logarithmic function.

The fact that the ear is more sensitive to higher orders has been known for decades and should not be a matter of debate! This is very easy to prove with simple test equipment.

Add to that the fact that the ear is tuned to be most sensitive to bird song frequencies (Fletcher-Munson). This fact arises out of evolution and is millions of years old- birds are the first warning of a predator in the area!

So the fact is that if the ear does not care about the lower harmonics so much, then logically we should be designing to eliminate the higher orders, especially since the tools that the amplifier designer has in the tool box all have certain limitations. For example, as I stated earlier (and as been stated by Norman Crowhurst, a universally recognized sage), loop negative feedback is known to add additional harmonics and IM distortions (the harmonics can go as high as the 81st and the intermodulations occurring at the feedback node in the amp). In this way an amp with feedback will usually sound brighter than an amp without, even though on the bench they both measure flat.

So what is more 'accurate'?  Low distortion on paper is meaningless unless we also know what it is that makes it 'low'. Its one thing if we can see the lower orders in the harmonic distortion spectrum. But if we are to take how the ear perceives sound into account, the higher orders should really be a lot lot lower than they are currently with all 'low THD' amps. And by that I mean **at least**  2 orders of magnitude! 

Just seeing 'low THD' doesn't cut it.

****This is ignoring how the ear works!!!**** (fist bangs tabletop)

The fact is that as far as the ear is concerned, the distortion of most amps with seemingly really low THD is that the distortion is higher. Its easy to hear too- which is why tubes still exist in the marketplace 60 years after being declared obsolete. Its why the tubes/transistor thing has been going on longer than the internet!

(if the tubes weren't doing something right, they would have been gone long ago. How many flathead V8s are still in production? If you got 'none' then you probably also know its because they are obsolete. There is a huge difference between being declared obsolete and actually **being** obsolete!)

In essence, the bench specs are an excellent example of the Emperor's New Clothes. This is because you have to ignore the obvious coloration of brightness/harshness/brittle in order to really say that its more accurate. The bench spec thing still has its roots in the 1960s and has not changed much since then (its mostly based on an idea of low distortion and flat frequency response while totally ignoring what the ear perceives; its actually tuned to the eye rather than the ear).

Put another way- we like to think our amps are low distortion because that is how they look on paper. That appearance is false- we're not measuring the right thing. Try to wrap your head around the fact of the ear's crazy sensitivity to higher ordered harmonics and use **that** as a baseline instead. If you can make that translation, you will see that most amps are fairly high distortion and not accurate at all.