impedance vs sensitivity

Atmasphere - I read that speakers, before SS became popular, had much higher impedance (32 Ohm or even higher)?

Yes Kijanki, in the 1950s 16 ohms was common and there were 32 ohm speakers as well. Four ohms really didn't get popular until sometime in the 1970s.

Atmasphere

Regardless the rated impedance of the loudspeaker, doesn't the curve of it's impedance linearity play a more important role?

I mean some speakers, my own included profess an impedance level of 8 ohms... but in practice, delve to far lower means in common usage.

From merely the numbers/specs of an amp or a loudspeaker system, can one derive some methodology for pairing amps to speakers, or vice versa?

For instance, with your amplifiers, do you forewarn anyone as to the speakers with which they are not at their best? ....or are there such speakers?

About the only guidelines I've been able to hang my hat on are these... with 250wpc SS power, there aren't too many speakers such an amp won't drive well. ...and conversely, if a tube amp has 100+ wpc, speaker choices are pretty broad too.

The difficulty I've run into has been matching amps and speakers when the power levels of the amps get below 40 or 50 wpc.... or the speakers have exceptionally tall impedance, and a SS amp is the power plant.

The former interests me greatly, the latter not as much, though I thought to include it as the antithesis of the formers train of thought.

Thanks...

Atmasphere - If you can remember 70's it means you weren't there. I remember The Beatles playing on 30W VOX amps and people tossing LUXMAN tube amps to get beautiful and modern transistor amps. These SS amps often had rated unmeasurable THD and IMD distortions and had a lot of power but sounded like crap because of deep negative feedback and tons of TIM distortions.

Yeah- those LUXMAN amps were pretty cool!

Blindjim, Here is how it seems to work: regardless of the amplifier, there are speakers it will work with and others that it will not. In the case of an 8 ohm speaker that has dips, the dips are of no consequence to a tube amp as long as its a crossover we're dealing with. What **is** of consequence is when the impedance maintains a sustained drop, for example when there are dual woofers in parallel (like in the B&W 802). There is no tube amp in the world that can play a B&W 802 properly (there are some that do OK) on account of that issue.

Here's why- if you use the 4 ohm tap, there will be ringing in the mids and highs because the output transformer is not loaded correctly. If you set for the 8 ohm tap, you won't be able to get enough power to the woofers- it will likely be a good 4-6 db down! The B&W was designed for an amplifier that can make constant voltage into any load (double is power when impedance is cut in half).

Conversely a transistor amp of 250 watts cannot make bass on an ESL (Sound Lab for example) because the impedance of the speaker is a lot higher in the bass than it is in the mids and highs. That transistor amp might be limited to no more than 30-60 watts into that load!

So matching is important, and yes, we do try to check and see what a potential customer is using on this account. Of course I like getting a sale, but it will do no-one any good if the amp won't work with the speaker, so I've had to steer sales away from us a number of times in the past on this account. After years of this, I realized that there was a bigger issue- that equipment matching, tubes vs transistors, objectivist vs subjectivist are all the same conversation- thus the link I dropped earlier.

Making power with tubes has always been expensive, and I have really come to value efficiency in a loudspeaker as long as it does not impair detail and bandwidth. That is a sometimes a tall order, but the speakers exist, but probably a topic for a different thread.