Speaker ratings, how to interpret?

Bomarc: Well, as usual, it's hard to say clearly all you mean in these short posts and, when you make the distinction between "specs" and "measurements", I tend to agree with you. Sometimes I think some folks around here are measurement adverse and so I periodically go off the deep end.

Sincerely, I remain

T, If you still need a few internet sources let me know.

I remain,

Not going to say very much except emphasize that this is REALLY an important question you ask. One of the most important issues when it comes to matching equipment. When an amp lacks for power for a given speaker/circuit it "clips". I think clipping is the most important distortion issue in stereo. It's not a matter of playing loud - the ability of your amp to deliver power(voltage & current as discussed in previous posts) will determine how you music sounds when it peaks - even at moderate levels.

The power output of the amp is determined by the load (speaker) impedence and the available voltage and current of the amp. Voltage, current and impedence work together.

Some speakers present a difficult load. If your amp is a one ton truck you do not want to put a two ton load in it. Many great "2 ton" speakers get poor reviews by people trying to move them with "one ton" amps.

Nominal impedence does not tell much. Impedence changes with frequency and certain resonant frequencies of the speaker itself. As noted above, an impedence curve of a speaker often looks like a mountain range.

My experiece is that if you are in the normal range of spending (under 10k) its best to get 1) an effecient speaker and 2) one that presents a decent load throughout the frequency range. This makes the amps job a lot easier. High impedences offer little chance for real power delivery. For example, an amp rated at 200W @ 8 Ohms will typically deliver only 3 Amps of current at best into a 12 Ohm load.

If you are new to audio/electricty this all may sound strange. If you are starting out think of it in terms of water instead of electricity. Electric potential is a pool or water near a hill. The hill represents the impedence of you speaker. The pressure needed to pump the water up the incline of the hill is voltage. The size of the pipe will obviously controll total amount of water that can go throught at a pressure (current).

The steepness of the incline may change just like music. Dynamic music causes steep inclines. The water (electric potential) does no good it you do not have the pressure (voltage) to get it up the incline. If your amp doesn't have the voltage it will clip. Sounds bad. Likewise, when there is no incline (low impedence) your amp may have design limitatioins on the amount of current it can handle when the water runs free so to speak. Current and Voltage abilities are built in design parameters of the amp.

Sincerely, I remain

Bomarc, With all due respect, the only dimensions that matter are not if it will fit on your shelf and whether the shelf will hold it. Specs can't tell the whole story but they have a lot of important things to say and some basic mistakes can be avoided by paying attention to them. Listening is not the whole story. I agree that ultimately the ear has final say but the ear cannot tell if the speaker is bad or if the amp is underpowered or if the room is acoustically poor or if there is some other design problem involved. You need to use and respect both. You cannot rely on specs in the marketing material.

Sincerely, I remain

Sean: I haven't read stereophile for awhile because I shook my head over a couple reviews a couple years ago. You find them helpful and among best nowadays? Maybe I should take a second look. The only thing i been reading regularly is audioXpress.

Sincerely, I remain