High efficiency speakers vs Low, pros and cons

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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Aroc asks an interesting question. I'm hardly an expert but as I've come to understand it, the first speakers were actually extremely efficient. The early years of vacuum tube amplification required efficient single driver baffle mounted speakers. Musical, but pretty crummy frequency response. Later came the "great" multidriver high efficiency horn speakers (Klipsch's, Altec's, JBL's, etc).

The less efficient sealed box designs utilizing multiple drivers and power robbing filter components happened to come at a time when we saw higher output tube and transistor amplifier designs. Efficiency was no longer a big deal. The culmination of this was probably the small closed box mini-monitors that utilized complex power hungry crossovers and a sealed box to create "bass" from much smaller than expected drivers. (I played with these designs for awhile in the early 80's. The crossovers were complex and the resistor networks in them often became quite warm to the touch at moderate listening levels. Lots of the amplifier power was used to warm the room! I recently acquired a blueprint copy of the KEF 101 crossover from the factory and that extremely complex 2-way crossover included 25 components including a relay and an LED!)

Vented box designs promised better efficiency with even lower bass. (Unfortunately it's not always well executed.) That has sort of made them the predominant design for the last couple of decades. Now, with audiophiles falling into various camps that favor everything from SET's with single digit wattage to solid state designs with nearly 4-digit outputs, speaker designers are free to create what sounds best to them with the knowledge that proper amplification can be found for nearly design.

Sean is right, unless you're running a SET amp, choose any reasonably efficient speaker. Other than that there don't seem to be an absolute pros and cons to high efficiency. If your amp is unhappy with low impedances, checking the impedance curve of a speaker is important before buying. Again, I'm certainly no expert but those are the only numbers I pay much attention to. I buy what I enjoy listening to.