Axiom Home Page Forums General Discussion Home Theater Outlaw and Emotiva products...?

As SK mentioned, it was not always about how loud I was playing material. It did seem to be about dynamics possibly. I remember many movies when I was not listening at unusual levels, say -20 to -15 on the Denon dial, 0 being reference. During some movies that had explosions and bombs going off, normally one of my 80's would shut down, followed by the second one a short time later. The MPS-1 had basically seperate monoblocks for each channel.

Also, I remember times when I was listening to regular classic 80's type rock form about 13ft away at about 85-90dB's on the meter, when they would shut down.

I also compared my Denon 2805 alone rated at 100watts/ch, to the MPS-1 with a variety of different types of music. The Denon would keep going all the way MAX on the volume knob +18 or so, and was maybe introducing some clipping that I was not detecting, and it still sounded pretty good, never shut down.

On the other hand, the MPS-1 would shut down around 0 to +5 on the dial. Was very clean and no clipping, but would go lights out. Something wrong when a beefy amp with ratings to blow away the Denon, would shut down when driving such efficient, easy to drive speakers.

Also, some people seem to forget this problem is not common to only Axioms. I know of at least 2 others that owned Rocket bookshelf speakers having the same issue, they were 4 ohm as well.

The LEDs may not have had time to react to the peak. The amp's protection circuit could have cut the amp out before the LEDs had time to illuminate. The LFE cutout does not surprise me. It takes more instantaneous power to produce a lower frequency tone than a higher frequency tone due to the longer wavelength of the low frequency tone. There could be many reasons for the trip. It could be that the amp's RMS rating is good, but it's dynamic power (as limited by the protection circuit) can't cut it.

Absolutely, that was my impression and the point I was attempting to make, it was the peak and not the average volume level (the led readout), Casey01 asked how loud you had to crank up the amp and I think the answer is not very loud, it was not an issue of pushing the parameters of the amp in terms of a high volume application (e.g., heat shutdown).

Hmmm... I'm not sure about the MPS-1, but the problems concerning the XPA-2 almost make sense according to Emotiva's explanation, that the M80's actually dip down to 2 ohms when pushed really hard. And am I wrong that the protection system is 2 fold... A. it's there to protect the amp from over working, and B. it's there to protect the speakers? So in the event discribed, it detected a huge pull from the source, and didn't want to send all that power to the speakers and damage them? Of course the XPA-2 couldn't know that the speakers hooked up were Axiom M80's and could handle all that power and then some, all it would know was that it was more power than it was 'supposed' to send to the speaker.

I could be wrong, but that's how I've always understood protection systems like those to run anyhow.

As JohnK, Alan, Steve, and others have mentioned on another thread, how hard you push a speaker will not lower the ohm rating of the speaker anywhere across the frequency range, it does not work that way.

Thats the thing about a good lie spin. It is based on a kernel of what might be the truth.

We have at least two independant measurements of the M80 (audioholics, goodsound network) showing that the M80 never really drops below 4 ohms.

From what others here have posted this is not an issue with all of Emotivas amps have this issue, but the xpa-2 certainly does.

From what Alan posted, one engineer from Emotive admitted they had an issue with the proteciton circuit. Whats a company to do if that problem is not easy to fix?

I didn't want to bring it up, but in reality, increased power could result in an impedance change if the increased power caused the load to substantially heat.

Unfortunately for Emotiva's claim, it would increase, not decrease the impedance of the load.

I see. Well I certainly don't know enough about ohms to know how it works, so I'll just have to accept their knowledge on the subject as fact.

One thing I was wondering about though... I've always held an amps THD (total harmonic distortion) rating as a measure of it's quality. But when comparing the RPA-2 against the XPA-2, the RPA's THD+noise is .035 percent (not atrocious, but certainly not top notch either) and it's the so-called 'audiophile' amp of the two. Then the XPA's THD+noise is .007, and it's considered to be beefy, not the finess amp of the two. So why do all the reviews on the RPA-2 talk about the clarity as compared to the XPA-2 when it has 7 times the harmonic distortion?

That has me scratching my head.

They start discounting the amp...

http://emotiva.com/xpa2.shtm

Nobody has ever been shown to be able to hear the difference between anything like .037 and .007 THD. Once you get below 1% (and considerably higher than that once you get outside our audio sweet spot) you can't tell the difference.