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What type of load is the AR10Pi ?


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Do we have input impedance measurements for all the old AR systems?

10Pi,  11, 5, 2ax, etc.

I have the AR3a but I think that it is for the early version only not the later.

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23 hours ago, DavidR said:

What type of load does the AR10Pi present to an amplifier?

Is this what you're looking for? http://www.classicspeakerpages.net/library/acoustic_research/add_series_1975-1978/add_series_brochures/ar-10pi_brochure/ar-10pi_brochure_pg4.html#previous-photo

It says "4 to 16 ohms nominal, depending on switch position"

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I was speaking to the guy who builds the amps for Bob Latino and was asking if he thought it would drive the 10Pi. He asked if it was a resistive or a reactive load. To be honest I don't know what a reactive load would be in a speaker, thus my thread.

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I felt it was useful information on a few different levels and I spent the time searching for it as common courtesy but, so what, the culture has changed, rite?

AFAIK common AR knowledge says that AR included ferro-fluid  with their AR-9 and no doubt also with the AR-11 and 10Pi in the new series.

I run AR-LST's with an even bigger transformer in the X-over along with nine multiple drivers in each cabinet and never experienced any grief because of it while using transistors. Tubes may not be that different.  I don't recall ever hearing folks complaining of difficulties as many folks were still using tubes when the AR-11 variant was released.

 I believe if you're using a fuse as you should, a blown fuse or 'open' would create problems for tubes.

A good web-search with time will probably offer more info to you.


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A transformer is just two or more cleverly arranged inductors.

Even without a transformer, speaker crossovers contain capacitors and inductors, which are reactive components.

Driver voice coils have inductance.

The only truly resistive load is a bunch of resistors.

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  • 2 weeks later...

I think the question should have been; Does the 10pi have a (fairly) constant impedance? The auto-former will more than likely introduce a huge impedance swing into the impedance curve somewhere. The only way to know is to measure it. My Klipsch La Scala's use an auto-former and the factory crossover had a large impedance swing. I rebuilt them into ALK clones.

The impedance plot below is from an OLA with news caps (and incorrect surround. Notice the high Fs = 52Hz). The impedance peak at 600Hz is not a problem for any solid state amp. However, a vacuum tube based amp prefers a constant impedance for best performance (especially SET Class A amps, with no global feedback).

The peak at resonance can be tamed as well, but it will require a huge inductor . The peak at resonance is not really an issue (a compromise) as long as the rest frequency range is fairly flat.



The below impedance plot (DATS2 software) is from the same woofer (with correct surround; Fs = 39Hz) with a series notch filter. I have several SET Class A amps and they sound better with speakers that have a near constant impedance.



If you tinker with speakers even for one project, the DATS2 software from Parts Express is worth every penny.

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