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  Emotiva XPA-2 Protect Mode With Axiom M80 Speakers
 

Per roadrunner:

The problem results because Axiom's crossover design does not have a roll off filter on its drivers. It allows them to run untethered far below their ability to produce useful output, but under some combination of circumstances this design allows the impedance to drop below 2 Ohms.

At high volume levels, when the M-80 presents a sub 2 Ohm load, the XPA-2 will go into protect mode to keep from melting the voice coils in the speaker. What happens is that the XPA-2 responds to the drop in load by trying to provide the increased power needs of the load and senses that the wall outlet is incapable of providing enough juice to meet the need... protect mode jumps out to save the speakers from damage.

This would never happen, if Axiom had elected to use a crossover design that would provide a roll off filter to prevent the drivers from impeding on each others designed frequency outputs.

If you want a more detailed explanation of exactly what happens, why it happens, and when it happens call Lonnie at Emotiva. He is the man who designed the amp and is very familar with this problem. He has been in touch with the Axiom engineers and is fully aware of what is going on with the M-80.

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Lonnie's comments as to why the XPA-2 goes into protect mode with the Axiom M80's (or any other speaker that attempts to dip well below 3 Ohms for any period of time). His comments are rather humorous:

The reason is very simple, we do not current limit our amplifiers. If I was to put a current limit in the amp it would pretty much play into a crow bar but that would suck the life out it and it wouldn't have the headroom it has now. Sure it would play loud (loud and lifeless), but that would in my opinion destroy what makes it special. When dropped into a 2.4 ohm load the amp will try to draw a boat load of juice but won't be able too (it is going to try and produce in excess of 1500 watts per channel). The end result is that the rails will dip, distortion goes up and the protect will shut off the amp to protect the speaker from damage.

So are you saying I should limit the amp just so it will play on any speaker???? I mean if you really want it I can have it added to design from now on.

For a more detailed discussion, visit this thread at the Emotiva Lounge.