Would like to use PS-2A with a late 60’s Super Reverb. 4X10. 2 ohm load. Assuming this is would to acceptable but checking before I purchase. Realize that there is a 2/4 impedance selector. Thank you.
Yes, the 2/4 setting is appropriate for that application.
Dave
I’m in a very similar position. I know the above says “it’s fine” and the manual says something so similar - but why? What impedance is the 2/4 setting actually?
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All of the Power Station models are configured to accommodate a 2 or 4 ohm impedance when set to the 4 ohm mode (2/4 as listed on later models).
The impedance rating of a speaker is a nominal number derived from a specific test configuration in order to optimize it for use under specific conditions.
Since actual operating impedance varies wildly with frequency, the actual numbers 2 or 4, etc are less relevant that actual operating conditions.
However, as far as safe operational parameters, there is no question that it is safe to run the Power Station with a 2 ohm amp in the 2/4 ohm setting.
Cheers! Gil
Mmmm speaker impedance rating does mean something though hence why it’s measured and advertised in order to properly match speaker(s) to the amp’s output transformer.
I would disagree that speaker impedance varies ‘wildly’ with frequency. It’s pretty easy and consistent to chart and it usually looks like a stretched out ‘U’. Impedance rises as frequency exceeds 2khz due to voice coil inductance - is an example of a predictable (not wild ) impedance vs frequency characteristic. Attenuator manufacturers know this which is why they have bright and bass controls or switches to compensate for the flattening of that impedance vs frequency curve as the load becomes more resistive and less reactive under heavier attenuation.
So let me be more specific. It’s not about safety or being “ok” when the product is this expensive. It’s about this specific case - a 2 ohm output amp: is an attenuator designed to match that load exactly, a THD Hot Plate 2 ohm for example, going to feel and sound, better than the PS2A which yes can operate ‘safely’ but probably has either 4 ohm load at 2/4, or something close 3.X if I was to guess? Thanks
Speaker impedance does mean something. Just not what you think it does. And looking at graphs and charts tell you something specific as well. Just not what you think they do.
We see this all the time. People always disregard the term 'nominal" and the fine print that defines what actually gets tested and why. The thing that is most often overlooked is context.
Speakers are tested at 1W in an anechoic chamber on a fixed infinite baffle and driven by fairly high powered solid state amp (at 1W) at a source impedance in the fractions of ohms which is playing a frequency sweep into the speaker. The result is recorded by a microphone 1 meter away into a computer program that “optimizes” the output in order to provide a comparative result - e.g, a result that can be used against a reference - which is used to grade all speakers on a production line. That’s the context. You can well imagine that the test procedure for a reactive load is a quite different exercise.
“Nominal” is the term used to qualify that the rated “impedance” is contingent on a lot of factors that the end user typically has no use for. This is simply verbiage from one engineer to another.
In order to not go entirely off the rails, a reactive load is a virtual model of an impedance curve. As such its “nominal” value is contingent upon many of the same circumstances that an actual speaker is, but since it’s not a speaker, it is not an exact comparison. Therefore comparing the “stated nominal impedance” of a Hotplate to the “stated nominal impedance” of a Power Station or any other brand reactive load, compared to the “stated nominal impedance” of the specific speaker you are interested in is an approximation at best.
In short, we’re talking about comparing one 1.5 -3.5 ohm reactive load to four 6-10 ohm speakers in parallel (not just the one as would be represented in a graph).
Dave