Speaker impedance patterns - how to read them?
A tube amp, as a voltage amplifier, likes a regular impedance pattern. All power amplifiers are actually voltage amplifier, but tube amps typically have higher output impedance, which makes the output vs. frequency load dependent. Please see the first graph’s black trace for a very typical example: https://www.stereophile.com/content/doshi-audio-evolution-monoblock-power-amplifier-measurements I am aware that solid state, powerful amps are built to compensate for modern speakers’ complex impedance patterns, I would not use this phrasing. Solid state amps tend to be more ideal voltage amplifiers, with a lower output impedance. There is no particular compensation, unless you mean a feedback loop, which tube amps can have too. They aren't compensating, they are lacking things like output transformers, which reduces the output impedance of the amp. When looking for suitable speakers for a tube amp This is actually a little complicated as a lot goes into this. The sound of your room, and your personal preferences may complement each other quite well. There are some general guidelines, which is to avoid speakers who dip below 4 Ohms, and those with sensitivities lower than 92 dB or so. Generally also avoid ESLs or you’ll lose all the treble. Of course, you may have an overly bright room, or amps which are less sensitive to this. |
Keep in mind that a higher impedance speakers, say one that peaks at 10 or 12 Ohms but is rated at "8 Ohms", will require more voltage to drive it than one that peaks at 8 Ohms. It won't need as much current at 10 or 12 Ohms obviously, but it will require more voltage. The only way you can get more output voltage is to use a higher wattage amplifier if you going solid state or use a higher impedance tap if you are using a transformer coupled output stage, such as most tube units. Remember the Dahlquist DQ-10's? They had a relatively low impedance dip but also had a high impedance midrange, so they required both higher current and higher voltage to drive them properly. Not too many amplifiers back in the day could do both. |
“One time recently we had some really inefficient little speakers in here, 87dB I think they were. My 20wpc Raven Blackhawk not only had no problem driving them to a nice loud level, it made them sound a helluva lot better than a 100wpc ss amp that was also used. Enormously better. So ” How entirely errrrr ....... Believable ... Not |
