High efficiency speakers vs Low, pros and cons

I have been researching Amps and Speaker for the last few months and I would like to pass along some info here. High efficiency does not necessarily equal high sensitivity. A high sensitivity speaker may still not be efficient and it might require lots of power whereas a low sensitivity speaker might be highly efficient. SET amps like/need high sensivity speakers simply because the low wattage of SET amps cannot be heard otherwise unless they are running through high sensitivity speakers; however, what makes a high sensivity speaker efficient is the impedance swing. An 8ohm speakers that stays true and close to 8ohms as possible is an efficient speaker. Let me clarify. It takes 300 watts at 4ohms to equal the sound of 8ohms at 150 watts. SET amps are not what I would call efficient. This being the case, if the SET is connected to a speaker that swings from 8ohms, down to 4ohms, some of the frequencies will be lost, probably the lower end. This is because the SET will have to push twice as hard to pump current when the loads swings down to 4ohms. Do I have you confused? The SET needs a speakers that is steady; whether it is a steady 4ohm, 8ohm, or 16ohm, or whatever. So, in essence, you could have a speaker with an 86db sensitivity rating, but with a nomimal, steady, 8ohm requirement and therefore be efficient.

This info is why I have chosen to pick out my speakers and then pick out an amp that goes with my chosen speakers. It should work out for me.

Those Von Schweikert DB-100s, what is their impedance swing? Do they have a nomimal rating or do they go between 4 and 8 as most speakers do?

I am still a rookie at this, but I think I am somewhere in the ball park. Experts, how close am I?

Thanks, everyone, for your responses so far. It seems that I've opened Pandora's Box a crack.

Matchstickman - My 100 DB's are 8 ohms nominal and 10 ohms max. They are also 100db at 1 watt at 1 meter, in room.

My amp is a Rogue Push/pull KT88 Tube at 60 watts. Do you think it will be a good match? Von Schweikert says yes.

Richardmr, from my humble knowledge and experience, I would have to agree with Von Schweikert on there answer. Your amp and speakers will probably sound simply fabulous.

Let me shoot this question. Theoretically, why would the first engineers to design a low sensitivity/efficiency (???) (like 84dB/w/m) when ligh sensitivity/efficiency (??) speakers were available? Considering the fact that the first viable amplifiers were diminuitive (3W SETs, etc) naturally speakers that designed around those amps. Since all things being equal (and they never are) a 50W or 150W amp generally costs more than a 3W or 8W one. What would be the driving (pun not intended) reason to reduce sensitivity/efficiency (??) in a new loud speaker design.

Flatter response over wide frequency range?
Cheaper construction or cheaper R&D costs?
A different "sound?"

For example consider a $75-200 loudspeaker from Circuit City. (Essentially a shoe box with some drivers). Why should these designs be 87dB/w/m. Why not make then 97dB/w/m? Since someone that price conscience about loudspeakers probably can't afford a decent amplifier (either SQ wise or power output wise). You'd think the HT crowd would be all over high sensitivity/efficiency speakers, since you could drive 5 our 7 speakers in a big room with just about any A/V receiver.

Tubes vs. SS. Analog vs. digital. MC vs. MM/MI. Active vs. passive. 3way vs. 2way vs. 1way. I realize everything is a trade-off. And no matter what the technology or features, there are generally great executions of all of the above. And it's more about the end result than any specific technology. There are no absolutes. No "magic bullets."

This is just something I've always wondered. What do low sensivity/efficiency speakers "bring to the table" so to speak?

This is a VERY technical question and involves the engineering trade-offs between transient response, bandwidth, driver excursion, cone break-up ( distortion ), power handling, etc... Suffice it to say that if one could achieve "perfection" i.e. all of the desirable traits that we look for in hi-fi with high efficiency, the designer would be a genius that knew how to circumvent the laws of physics. As such, engineers and manufacturers weigh the balance in what they are looking for and design according to what they have available to achieve those goals at a given price point. As such, a medium efficiency speaker offers the best compromise in several areas. On top of that, they are also the most commonly available in terms of selection of drivers, so that is what we end up with as a majority. As others have mentioned, either design can work well in a system IF that system is set up to work as a team. Like anything else though, the team is bound to have a few "star players" ( high points ) and a few sore-spots ( weaknesses ) regardless of the efficiency.

My suggestion is to look for speakers that are at least "reasonable" in efficiency ( 88+ dB's ), offer a stable impedance that is 6 - 10 ohms nominal and will cover the frequency range that you want in a room the size that you'll be using them in. Then again, finding all of these features in one package at a price you can afford is "almost" like having your cake and eating it too : ) Sean
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