What a great question, Larry! Actually it's so good that it merits an entire article, but perhaps we can do a down payment on one.
     If a loudspeaker has low sensitivity that doesn't mean it's a bad speaker, only that you will need more amplifier power to drive it. Even so sensitivity is relative. A sealed "acoustic suspension" speaker like the celebrated AR2 has an efficiency of 2%...it produces 2% sound for 98% heat. But even a highly efficient speaker like the Klipschorn has an efficiency that hovers around no more than 15%. Those figures look so bad that no designer wants to use them anymore. Instead, they us sensitivity figures. If the rating is 91 dB, that means that if the speaker is fed a 1 kHz tone at 1 watt, the sound level one metre in front of the speaker will be 91 decibels. This rating method lends itself to self-serving creative measurement, but we don't mean to suggest that this is why it is used.
     There is a trade-off among small cabinet size, extended low-frequency response, and high efficiency. Essentially you can have two out of three, and it is the designer's job to pick which two. At the moment very high-efficiency speakers are in fashion, because they can be used with high-quality but low-powered amplifiers. Of course, a tweeter like the Revelator doesn't "know" how big the cabinet is. It is, however, connected to a crossover network part of whose job it is to match the efficiency between woofer and tweeter.
     Impedance is another matter. We might want to have a perfectly resistive impedance at a constant 8 ohms, but because drivers and crossovers have capacitance and inductance this is nearly impossible to achieve. The impedance of an "8 ohm" speaker may dip to 3 ohms at one frequency and soar to 100 ohms at some other frequency. Swings that extreme are tough on an amplifier, and especially a solid state amplifier, and so the speaker designer has one more job to do: keep the impedance within reasonable bounds. Different designers make very different choices yet manage to get good results.
     There are many paths to Heaven. And to The Other Place as well.

     My speakers have two sets of posts for biwiring or biamping. Would it be better to biwire using "decent" cables or use only one set of "very good" cables? 
     Also, spades of banana plugs? It seems to me you favor bananas, but if I were constantly swapping speakers and/or amplifiers for comparisons...
Ken Hicknell, KITCHENER, ON

     Yes, exactly, Ken, though we have other reasons to favor bananas. They are of standard size, or at least they are supposed to be, whereas spades are whatever size and shape the designer wishes. To add to the fun, some binding posts are nearly impossible to tighten adequately, and don't stay tight in any case.
     In general we favor one great cable over a mediocre biwire pair. Sometimes the answer is not quite that simple, though, which means that the answer may change depending on the individual cables.

     I am writing regarding an article in UHF No. 77 which describes how to transfer LPs to high resolution 24/96 DVD. It took me a long time to prepare for this, as I first had to acquire a 24/96 recorder, install a DVD writer and purchase the software. The software you recommended was Roxio's Easy Media Creator so I purchased an EMC10 Suite (the latest version) but guess what — it does not support 24/96 audio. It took almost two weeks of communicating with Roxio for them to finally admit it. 
     I did however find another progam which works nicely and costs only about half as much. It is Audio DVD Creator from Goland Tech. The free trial has limited use and is good for 30 days during which time you can permanently activate it for $39.95. I find it quicker and easier to use than the Easy Media Creator suite which has a lot of programs imbedded in it, each designed for a different purpose. I suppose I will one day find another use for EMC10 (photos, video, 16/44.1 audio etc.), but for now Audio DVD Creator is the one for me. Just thought you should know.
Lloyd Marshall, WHITEHORSE, YT

     We appreciate the information, Lloyd. It appeared logical that Roxio's Easy Media Creator for Windows should be a feature-for-feature match for its Toast software for the Mac. But Roxio is a strange company, and since it went to the bother of giving the two programs different names, we should have guessed they might not be identical in other ways.

     I have a question concerning the purchase of a moving coil cartridge.
     I am using a Copland CTA 305 preamp, which only takes high output moving coil. If I understand correctly what I have read in your mag, a low output is much better. If I were full of money this question would be irrelevant because I would purchase an Audiomat phono stage and a low output MC.
     So I have the Copland, and I use a Clearaudio Master Solution with a Satisfy tone arm. I already own a Benz Ace high output cartridge. I wish to upgrade to a better cartridge. If I purchase a low output I won't be able to afford more than the Moon LP3, or the Rega Fono. Would either of these still bring out he advantage of the low output, or should I  look mainly to high output cartridges? 
André Avon, SAINT-JEAN SUR RICHELIEU, QC

     We haven't listened to the Moon LP3 phono stage, André (the Moon LP5.3 reviewed in UHF No. 83 is excellent but far more expensive). We do consider the Rega Fono excellent, about the equivalent of your Copland preamplifier's built-in phono stage, but of course for low impedance (low output) cartridges.
     Perhaps we should make plain why a low output cartridge is superior to a high output MC cartridge, at least in theory. Since it is the coil that moves, it needs to be kept as light as possible, with less wire in it. Because its low impedance is not what a conventional phono stage "expects" to see, it requires either an extra stage of amplification or a transformer. A high output MC cartridge is a compromise: the coil is larger and therefore more massive, with of course more inertia. It may still be very good, but all else being equal it is handicapped by that extra moving mass.
     Have we really answered your question? Perhaps not. If you have the funds available for one of the better MC cartridges, then yes, you are likely to enjoy the difference.

     Congratulations for your magazine! Great!
     I own : a TEAC VRDS T-1 transport and DT-1 converter, a Copland CSA 28 amp, KEF 104.2 REF speakers, UltraLink Discovery home theatre interconnects, MIT speaker cables, and a Van den Hul The Mainstream
     The music is very sibilant with rock or heavymetal, and unlistenable with volume high or medium high. What or where is the wrong component in my system?
     My budget is about 1500.00$. What do you suggest ?
Fernand Fournier, PALMAROLLE, QC

     Our guess is that the amplifier is your primary problem, Fernand. The CSA 28 is an earlier version of the higher-powered CSA 29 we reviewed in UHF No. 69, and it was one of the few Copland products ever to disappoint us. We also found that, with some loud passages, it was nearly unlistenable.
     Its replacement will possibly cost more than $1500, but then again you can probably resell the Copland to someone who doesn't read us. While you're at it you may want to pick up better interconnects too.