Axiom Home Page Forums General Discussion Home Theater XPA 2 Now! A Keeper?

Well I was sort of underwhelmed with the XPA 2 for the first day and a half watching/listening to compressed Directv HD and 1 or 2 poorly recorded CDs but then tonight I bought the bluray Hulk and Wow! What a mind blower! I was totally sold. It's funny too, you know my best friend who watched Iron Man and Hulk (multiple times with his son?) in the theater thought Iron Man was better and Rotten Tomatoes gives Iron Man a 93% and Hulk only a 67% approval rating but it made perfect sense after tonight why a number of posters here liked the Hulk better, the Hulk soundtrack is so much more engaging/fulfilling to my ear from an audio sensory perspective.

Here's the problem--the XPA 2 kept going into protect mode, not for sudden loud sounds but whenever there was a crescendo.

Problem #2: I think I might have messed up one of the inputs when I was unpacking the amp to keep from dropping it, I'm afraid 87 lbs (?, or whatever) is a bit unwieldy and that would be my main critique of the amp so far; as I get even older with even more back issues I would/will need a maintenance crew to move things around; hmmm, I wonder how I am going to the muscle the ep800 into position, I have wood floors doncha know and sliding things is an issue, of course we have felt pads glued onto the bottoms of all furniture, is that just as good sonically as the rubber feet on all this "audiophile" equipment (axiom, emotiva)?

So far on the Emotiva lounge the XPA5 has been causing red light of death issues for random folks and it's been blamed on cabling (something I need to experiment with) but no one has had trouble with the XPA2 so maybe the damaged RCA input is my problem. I can experiment with cable connections as well, is there such a thing as an RCA/unbalanced to balanced input adapter? Maybe if I avoid the busted RCA input I will be OK--I have questions though: at first the red lights were all on the left side, which is the side with the loose input, then they shifted to the right side, in which the input is OK. There is zero noise at any volume, so there is nothing so crude as that going wrong.

Also reading the Gene Dela Salla article where he was having trouble in some sort of test mode (?) when sweeping from high to low (20k to 20hz) but not on stereo playback, and it seems to me that he may not have tested the amp that much for HT (?) as opposed to music, might that correspond to the shut down on crescendo issue I am having, given that HT tends to boom out the lows increasingly during exciting sequences? More or less a random thought, but I had to wonder why the impact of sheer volume did not seem to trigger a protection/default shutdown by shaking something loose, if power alone was the issue.

Of course this has all been so exciting that I keep listening to the movie at high volumes and haven't even been annoyed by the frustrating interruptions, I would even like to keep the amp if I can work through the problems, isn't that always the way, things go wrong on Friday evening, just as soon as there's no one to call?

Well if any one has any info re: emotiva protection issues that would be cool, but as a disclaimer I must point out that since the input appears to have been damaged and no one else has reported the issue for the xpa 2 the positives I am experiencing may stand and the negatives may be irrelevant and hopefully will be resolved . . .

Wow, why does this not suprise me. I'm sorry for your problems. Over a year ago I had similar issues with the "king of the hill" MPS1. Driving two m80's it kept shutting down. Emotiva would send me new amps to put in the chassis, and guess what, they would shut down. They wanted me to cut some limiter circuit off the boards to bypass this protection. I think not, after 3 months of screwing around, they graciously let me return them for a full refund. Sure sounds familiar.

Have been driving my 80's with Odyssey Audio monoblocks ever since with no issues. And just to let you know, my Denon 2805 would reach much higher levels with no clipping before the MPS-1 would say goodnight.

I also would like to mention, I was not listening to what I call very loud levels. Even during explosions in movies, they would shut down.

My guess is that your using 80s?

I was afraid you were going to say that, I knew you had problems with the MPS-1, so much for the "new architecture" perhaps, maybe it's just the same limiter circuit.

What I keep wondering though is since I have changed so many variables at once it's become pretty hard for me to trouble shoot even conceptually what may be going wrong. It seems to me now since last post from observing/listening the rest of the movie that it may only be when the LFEs kick in that the amp shuts down, is it possible that when I am running a sub and have a crossover set to spare the M80s and/or with M80s are set to small that the problem will abate? I could test those variables now and of course I will but it makes me wonder. I still don't understand how the protection circuits work, are they sensitive to the situation in which the speaker is not able to handle the power X frequency equation, e.g., high power X LFE beyond speaker capacity blow out the woofer time?

I think the issue lies with the interaction of the M80s/emotiva protect circuit, so to speak. The M80s impedence may dip too low at a certain frequency thus causing the Emotiva to shut down, which makes me think Emotiva is a little too protective with their circuit, as there are many receivers that do not shut down with the M80s.

Hmm thanks for the feedback, that makes sense, if you are right it may be a death knell for the combo of the XPA2 and M80s, funny though because a number of people are running the XPA5 without problem I believe some folks with the M80s, maybe just the M60s. I was hoping the difference in electronics between the XPA and MPS series was the culprit, the irony to me initially with all this was that the MPS1 has lower maximum output than the M80s are rated, I was hoping that the issue had more to do with a quirk with the MPS amp, perhaps not. The other monkey wrench is the fact that the emotiva folks state that the xpa2 is "a whole 'nother level" than the xpa3 or xpa5 architecture, perhaps the new level includes the protection circuit from an earlier (mps) level.

Sat, the Emotiva may be a mystery to me, but in general protective circuits take effect either because of too much heat(unlikely in your case)or too much current. LFE occasionally appearing during movies does require more current, but even well-designed receivers(e.g., Randy's 2805)should be able to handle this at reasonably loud levels. Yes, taking some of the load off with a "small" setting and probably a 80Hz crossover for the M80s should help, but it's disappointing if the amplifier needs the help.

OK thanks, that helps me better understand the basis of the problem, Dela Salla recommends having a dedicated 20 amp line to support this amp but I'm not sure even that would help, e.g., I just unplugged the amp from the power conditioner and plugged the amp into the wall (emotiva recommends plugging the xpa2 directly into the wall, presumably to draw current without obstruction) yet playing the same content the amp seems even more volatile, as if it is drawing even more power, which appears to trigger the protection circuit even more easily in response to a spike in power given dynamic HT content.

Must be time to try the A1400 for at least one set of M80's

Wish I had the dough, that's why I've been trying to take the low road.

Low road? I must be in the tunnel under it

So I plugged the amplifier back into the power conditioner and have been watching the amperage drawn, the protection circuit on the emotiva reliably kicks in once the measured amperage goes above 13 amps for the entire HT system (i.e., once it measures 13.3--13.8, inaudible BOOM!), the house was built in 1989 (we moved here from an apt in 2005, yay!) and I suspect it's underpowered from past experience with the AC going out, I seem to remember most of the power lines in our home other than the wiring for 1 or 2 major appliances being rated at a maximum of 10 amps, I'm thinking an electrician might be able to help, especially given that I'm anticipating an EP800 on or about 11/17, I could be looking at trouble if I fail to upgrade the power lines, why does it never end (ah, what would I find to do if the project ever ended? ).

Perhaps the M80s are thirsty and the home wiring can't keep up!?

Good one! I wished I lived in Canada, I loved those days when I still lived in the Northeast and cherished nature over what has always seemed to me an insane form of urban accomplishment (you move to the city for the wife, no?). Now the "sweet spot" to me signifies going totally over the top to future proof and avoid buyer's remorse without leaving me destitute. Bring me back to that lake (Dunmore?) in Vermont any day . . .

I guess when you compare $800 to $3850 the emotiva still is a good deal, if I had the cash I would have pulled the trigger on the A1400 and put myself out of this misery long ago . . .

If I were a rich man . . .

Reading these recent posts on amp/power issues, I guess I should be happy my HT is in a small room and don't need the extra power.

Maybe it can be returned for a few Outlaw Monoblocks or their 5 channel amp. I never hear of problems with them....

The M80s are a fairly easy 4 ohm load. Any amp that couldn't handle the M80s wouldn't be on my list for sure.

Hey Rick. Where is that graph from. I want it as a reference the next time some joker posts on audioholics that the M80 is a 2ohm speaker.

Ya know what Fred, Ive had that graph for so long I don't remember where I got it. Just copy it from my post and save it.

Come to think of it I believe Ian did a post here some time ago with a slew of different graphs, that's where it come from.................I think.

Sigh, I thought I would try the lazy man's way first. I guess if I park it in my online photo collection it will be hard to loose.

Hi Fred,

That graph is from the National Research Council lab in Ottawa, where Soundstage.com does many of its speaker measurements. If you go to Soundstage.com and then access their measurements, you can scroll down to the impedance vs. frequency charts for lots of speakers they've tested, including the M80s.

Yes, the Emotiva amps do have issues with low impedance high-current loads, as do some other manufacturers. Often a two-channel amp will do much better than a multi-channel amp, largely because the multichannel versions can't handle the heat issues. One Axiom owner had five M80s and went through a number of multichannel amplifiers, all of which would shut down driving the five M80s to extremely loud levels (those were Outlaw and Parasound multichannel amps). He settled on a two-channel amp for the mains and a separate three-channel amp, if memory serves.

Regards,
Alan

My memory sucks Alan is right...................I think

With tiled or marbled floors throughout ... ouch!

<-- Smacks forehead.

Thanks Alan. I've only been to the soundstage.com site a few thousand times. It seems to have the most comprehensive collection of anechoic measurements around.

It's a complicated site to navigate. It always takes me forever to find the measurements page. I'll post the link if I figure it out. . .

Hi,

OK, here's the link to the M80 v2 measurements and impedance curve:

http://www.soundstagenetwork.com/measurements/axiom_m80v2/

If you just go to http://www.soundstagenetwork.com/measurements you can access all the NRC speaker graphs for speakers that Soundstage has measured at the NRC.

Regards,
Alan

wow... I was really thinking it would be good to buy one of these XPA2's also. And to think audioholics gave it such a rave review... hmmmmm.

oh well, I need to buy an ep-800 first anyway... and a diamond ring before that.

The other alternative is to look for a good used amp on Audiogon.

You can usually find good deals on Acurus (A250 or A200X3) or ATI
AMPS there. I've had both brands and they never shut down on me.

Actually, he used 4 2 channel Parasound Halos. Of course, he was regularly driving them to 115 dB+

Thanks, Ken.

You actually experienced his setup and the 115-dB-plus SPLs, right? I had running communications with Denis as he went through various combinations of multichannel amplifiers.

Alan

It is intresting to look at the different measurements. The M22 which no one appears to ever have an issue driving, has a pronounced dip to 2 ohms, so much for my theory.

Does the high-current-draw-shutting-down-the-amplifier problem have anything to do with the fact that the electrical wiring in my home I'm pretty sure is not rated to handle the current being drawn? If I upgrade the wiring to 1 or 2 dedicated 20 amp lines, might that solve the problem? It doesn't make sense to me that it would except through some kind of instability phenomenon, e.g., when I plug the amp directly into the wall and presumably even more power is available it almost seems to cut out faster. I may need to upgrade the wiring anyway given the load I am already running and what with the ep800 on the way, but I was just wondering if there was any theoretical reason to expect that it might help.

I would think that by law, if an amp required more than a 15 amp outlet could put out, it would have a 20 amp plug. AFAIK, this one does not. Sounds more like a design flaw to me than a problem with your house wiring.

Alan, I don't think we ever took it to 115dB when I was there--I'm pretty sure we topped out at 105, and that was quite loud enough for me.

SatKartr,

I don't think the wiring in your home would have any influence on the performance of the amplifier cutting out, unless the circuit into which you had the amplifier plugged was clearly overstressed--you'd have indications of that with lights on the same circuit dimming on peaks if thr circuit was overloaded or inadeequate.

Alan

Oh, you mean like what happens when my laser printer prints something?

This is more or less unrelated to the conversation at hand, but I wanted to comment again on how nice it is that people like Alan from Axiom actively participate in these discussions, even when discussing problems that Axiom customers are having with non-Axiom products. It definitely keeps me coming back as I find that I'm always learning new things as I peruse the forums. <group hug over>

Jason

It sucks when one person has a problem with somthing that a hundred people before didn't and it turns people off. I have said this before and will say it again. my mmc1 and xpa5 are wonderful at running my m80,vp150, and qs8's. I have never had a problem with anything from emotiva. The louder I turn it up the better the m80's sound and the xpa5 seems to never run out of juice. As soon as the xmc1,cd player and dual subs are on the market they will probably end up in my living room.
I have been thinking about the ep350 and ep500 for a few years now but the thought of duals at 999.00 that come with a cool seperate amp and auto room correction. seems like a dream. maybe it is... only time will tell, I just have to wait for a audioholics.com review. To sum it up i think axiom and emotiva are both great companys that bring great products to consumers at amazing prices. They also stand behind their stuff and have great customer service.... Thanks

You are correct, of course, Turbo... I shouldn't have said design flaw, I should have said issue with this particular unit.

It was not my goal to turn people off, merely to find answers, by posting here on the board I have learned that high current appears to be the trigger for the unit going into protect. I haven't given up on the xpa 2 yet and plan to contact emotiva early next week. No one on the emotiva lounge has responded to my query suggesting it seems to be an unusual problem with regard to the xpa2, and could in fact be a fluke.

Alan states that a number of amps, not just emotiva, have not paired well with the m80s so it is also an Axiom issue to understand just what type of amp works well with the m80s. The xpa2 is supposed to be "completely stable into 4 ohms" and with the power rating it is hard to understand what the problem could be. Perhaps it is coincidental or something unique to my setup, time may bring answers or not, I will let you all know what happens.

With a 30 day risk free trial I think it was worth it to check out the amp and it is quite an amazing piece of electronics, I'm still hoping the issue can be resolved. Hopefully Lonnie will extend the trial period if necessary as he did for Randy to give me a chance to solve the mystery. Turbo I'm glad you spoke up as you did before, people need to know that emotiva can work well together with axioms, especially since you are running the m80s. I was tempted by the dual subs as well, the price/value equation is just amazing with emotiva!

If I had the money I would buy an XPA2 just to see if I get the same results as you or I could get lucky and have no issues and one very cool amp, but Christmas is coming and the wallet is very dry at the moment.

If the wallet is dry, may we infer you've made a significant non-audio purchase you've been hinting about for some time now?

Jason

Non-audio purchase, you sure that was me? I am still recovering from too much summer spending on my new patio and some work out on my parents property.

Sorry about that... it's late and clearly I need to go to bed... I was thinking of David (Terzaghi) and his continued hints that if he buys more speakers before buying a ring there will be serious hell to pay.

Definitely time for bed!

Jason

Too much time in the room of death coupled with lot's of speakers and a cool named amplifier, and all the other fun toys. Get some rest.

I thought maybe my wife had me posting something in my sleep just so she could say she had witnesses!

When I was having problems with my RPA-1, Emotiva told me that they have run tests with M80s and they can dip to 2 ohms.

If this is the case I would like to see an updated impedance graph from Axiom. The one I posted shows they dip nowhere near the 2 ohm mark.

That is interesting. When I was having issues a year or so ago, Emotiva had never heard of Axiom. There was also a guy with 4ohm Rocket bookshelfs shutting down his mps1.

Here is my long post, near the end you'll find MadScientist, that is Lonnis from Emotiva adding in to the conversation.

http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=162446&fpart=1

Hi SatKartr,

When I said ". . .that a number of amps, not just emotiva, have not paired well with the m80s" and you replied "so it is also an Axiom issue to understand just what type of amp works well with the m80s", I want to clarify my comments.

It is only under extreme conditions, such as the SPL levels that you are trying to reach, SatKartr, as well as some other Axiom M80 owners (sometimes multiple M80s) that some separate power amplifiers, Emotiva included, shut down or overheat. For the vast majority of users, the Emotiva, Parasound and Outlaw amplifiers will drive the M80s without problems.

It all comes down to a matter of current flow through the output devices at extremely high sound pressure levels, and the ability of the amplifier's heat sinks and/or fans to dissipate the heat generated by lower impedances. The M80 is "nominallly" a 4-ohm speaker and does not dip below 4 ohms anywhere over the audio spectrum.

In terms of heat dissipation and high SPL levels, prior to the development of Axiom's A1400-8, there was a memorable party at Ian Colquhoun's home. At the time he was running five Denon monoblocs at 350 watts per channel into the M80s, dual VP150s and five QS8s, plus two subs, an EP600 and an EP500. At one point in the party, the level controls advanced farther and three of the five Denons shut down. I was using earplugs all evening and even with the ear plugs I retreated into the woods outside Ian's house! The SPLs were deafening. That evening was the genesis for developing the A1400-8, as Ian had grown tired of the Denons shutting down at extremely high listening levels.

I'd also point out that there is no substitute for expensive output devices that can handle very high current flow into lower impedances without overheating. That's what we use in the Axiom A1400-8 and that's also why the amplifier is relatively expensive. In order to reach a particular price point, other manufacturers may choose devices that are much less costly and will be fine in most playback situations for most listeners--but not all.

Regards,

Alan

Thanks Alan for the clarification, sorry if I misconstrued your comments.

That party does sound very memorable! Ian must be quite over the top.

I'm not sure the amp is overheating though. I picked up an spl meter and am measuring 90-100 dbls in HT (doesn't happen with music at this spl) when the protection fault kicks in, which can happen within a minute or so of initiating a movie (e.g., the intro to Hulk).

Thank you everyone, I appreciate your help and efforts to increase my knowledgeability, at this point it clearly seems to be an Emotiva issue so I will pursue it via their tech support, and of course will let you all know if there are any solutions found.

Hmm. Is 90-100db for short periods of time considered extreme?

I'd say not, my Rotel can do that for long periods of time and only get warm to the touch.

Thats what I thought. It sure seems like a defective unit.

Well let's don't forget I inadvertently smashed one of the inputs before plug in so the jury is still out . . .

BTW the most poignant aspect about your post to me was the anecdote about retreating to the woods in the middle of Ian's party. OMG I miss Vermont, I used to love serene nature as a backdrop every day and took it so much for granted!

At least Dallas squeaked out a win today so I won't be living in Mudville tomorrow .

Yup, I agree having serene nature as a backdrop every day is really beautiful, and northern Ontario where Axiom is located is very calming. But I can't take the brutal winter and relative isolation up there for long periods of time.

I love my visits to Axiom but after 10 days or so I need the hit of the city and urban life.

Regards,
Alan

I'll be curious to hear what Emotiva has to say about this. They're probably getting tired of Axiom owners breaking their amps. Not sure what these sorts of posts say about their designs though...

I agree with the others. I don't think it's your home wiring. If you're pulling too many amps, I'd think you'd see lights flickering or you'd start flipping breakers. Although would it be possible to pull enough amps that you'd start to affect the voltage? I am NOT an electical engineer - so someone please correct me, but aren't volts and amps related? Could an amplifier go into shutdown mode if it was pulling so many amps that the voltage dropped too much?

For the record, I've never had any problems with my cheap LPA-1 driving my whole system, which includes M80's. I can turn the volume up far past the point where it hurts my ears. No problems at all.

Hi Peter,

Yep, volts and amperes are certainly related. I'm not an electrical engineer either, but in theory if there is a voltage sag in a circuit, it would seem feasible that overly aggressive protection circuitry might shut down an amplifier.

Protection circuits can monitor any combination of current flow, voltage and thermal factors, so depending on their implementation, they may react quite differently from one brand or model to another.

JohnK may weigh in here at some point. I'll also check with Tom Cumberand, Axiom's R&D "conehead" (as he refers to himself) who is an electrical engineer and an amplifier designer of long experience.

Regards,
Alan

I wonder how much the voltage would have to sag, I seem to remember the volts ranging between 119 and 122 at least according to my meter, probably closer to 119 when the amperage jumped up, I'll have to watch for that, but there did not seem to be much of a significant dip.

Lonnie asked me to try different cables as a diagnostic.

I changed the interconnects, same problem.

I switched speakers to Polk Reference 10bs and the speakers began to pop, crackle, and fry but the amp did not go into protect.

I used the speaker cables that were connected to the Polks to connect the axioms to the xpa 2 and problem recurred.

It's sad that I've forgotten pretty much everything I learned in my circuit analysis I&II courses. Sad.....

Here's where it stands, look like I may be at a deadend:

Today at 1:52pm, satkartr wrote:
I changed the interconnects, same problem.

I switched speakers to Polk Reference 10bs and the speakers began to pop, crackle, and fry but the amp did not go into protect.

I used the speaker cables that were connected to the Polks to connect the axioms to the xpa 2 and problem recurred.

One other issue: the left unbalanced input to the xpa2 seems loose, kind of droops downward, I think this may have become damaged when I first wrestled the amp out of the box, however I'm not sure this is relevant in that there is no hum or noise at any volume and I have tried running the right channel only and it still goes into protect.


Lonnie responded:

Looks like you found the root cause of the problem. If the amp does not go into protect with different speakers on it, but does when you connect the Axioms. Ipso-facto the Axioms are the cause. Now I don't know if a particular driver is bottoming out and shorting or if the crossover networks have an overlap with an impedance dip or perhaps the crossovers are just heating up and the parts are changing value, but something in the speakers is the cause and I would contact Axiom and see what they say

In my tests, the MPS-1 would not shut down when cranking up my Qs8's (6ohm) to the same level as the 80's (4ohm). Emotiva also blammed the Axiom 80's as being the problem. However, others with Rocket 4ohm floorstanders and bookshelfs had the same problem. Back then I think the amp was not able to drive 4ohm speakers, even though the Axiom's don't fall below 4ohm.

Not sure about this new design.

Get some M60's.

This is just me but if I were in the very same situation I would send the damn thing back and look else where. It's so easy to blame another product and not look into the actual cause of the problem.

I bet a $300 H/K 2 channel receiver would push those M80s just fine.

I am leaning that way, especially as those comments seemed pretty nonresponsive, I may play with the crossover setting first to see if I would have the same problem once I'm running a full 7.1 system, but I'm not sure what the point would be, if the amp can't be counted on to deliver.

Although I use a 2 ch Rotel 200 watt amp for the 80s with an H/K 75 watt AVR635 running everything else in the past I have had the H/K running the 80s to pretty darn loud levels for fairly long periods of time without a hitch and for the past year or so it has been running an 8 ohm VP100 parrelled with a 6 ohm VP150 (3.45 ohms) perfectly fine.

I know a Rotel amp will run those 80s easily.

You got that right BrotherBob

I was going to add "Ain't that right Rick", but I didn't want folks to think I was talking to myself ... again.

I can also vouch for the Outlaw Monoblocks. I can run 115 - 120 db's for as long as I can stand in the house...for about 40 min. after a few beers. I've only done this a few times folks...mostly around the time I got the amps to see how far I could push them.

The amps got toasty... but no shut downs with the M80's. Alot cleaner than the 3805 alone at high levels. I wouldn't consider an upgrade unless Axiom comes out with a 2-channel version (or 3) of the A1400-8.

Was the blood running out of your ears the first sign that the music *might* be a wee bit loud?

I believe anything Outlaw will run the 80s with no problems.

I couldn't sit in front of them the whole time. I live alone, so I also roamed around house while enjoying the music. Beer makes you brave...

SatKartr,

That's a pretty disappointing response from them... you can turn their logic around on them and tell them that if the Axioms DO NOT shut down your AVR when connected directly, but do shut down when connected to the Emotiva, "ipso-facto the Axioms are not the cause, the amp is!" (but maybe I'm just a smart a$$ and would enjoy writing them an e-mail like that after their sub-par effort to assess the problem...)

Jason

SatKartr,

You shouldn't have to be fooling with crossover settings to see if it helps at this point. That beefy amp you have should Not be shutting down. My advice is to look into getting a replacement, so you'll know for sure whether you've got a bum amp.

That's the next test actually and your logic actually makes perfect sense. I'm curious to see what kind of SPLs I can get out of the Yamaha, I just picked it up as a bookmark until I can decide exactly what pre/pro I want to go with.

I suspect maybe Lonnie is acting so lackadaisical since he went through all of this with Randy and the MPS-1 so now he may have a defeatist attitude regarding the M80s. It also seems funny because the MPS-1 is rated at 300 wpc into 4 ohms versus the xpa2 with 500 wpc into 4 ohms, so I wonder how the protect circuit works such that I can't even generate 90-100 dbls during HT, that surprises me.

I'll be interested to hear what you think about how the Yammy drives them. Please let us know.

By the way, is the family back yet or are you still off the leash?

Jason

They arrived a few hours ago, so the leash is back, well I suppose someone has to keep me in line.

Well Sat, as I commented before, the Emotiva remains a mystery to me. There were all sorts of discussions of measurement procedures both on the board and in PMs when Randy was investigating the problem. The resulting numbers weren't anything that should shut down even the typical modestly-priced receiver rated in the 100 watt area.

Protection circuits(besides eventually operating when the temperature would get too high)first operate when the measured current is out of line with the voltage being supplied at the time. One form of Ohm's Law is I=E/R, and if the measured current is some big number in relation to the voltage, that can only be because the resistance has become very low(i.e., a short somewhere in the wiring), and the circuits will immediately shut things down. Power supply sections are limited as to the maximum voltage that they can supply, and since power is the product of voltage times current, if not enough voltage is available for a given amount of power the current would have to increase so that the power equation is satisfied. This increased current measurement again would cause the protective circuits to shut down.

How all this seems to be a problem with the Emotiva/M80 combination at not extremely high sound levels remains unclear. I would be inclined to view the shut-downs as simply being God's way of telling you not to use that amplifier.

I have a feeling this chapter is removed from most electrical engineering textbooks. . .

I think I'm beginning to hear the Big Guy loud and clear.

What surprised me about all this was that Randy had problems with the MPS-1 but others with the RPA and XPA architecture have not had problems pairing the M80s with Emotiva.

Your post has piqued my curiosity though, you state, "if the measured current is some big number in relation to the voltage," are there any standard examples of what a large amperage would be or is it all relative? It seems like the amplifier is going into protect when the current goes up to around 6 amps above baseline (it shuts down when amperage reaches 10-13 amps for all devices connected to the HT electrical circuit with 4-6 amps being the reading when the HT system is on but idling), that level does not seem that extreme to me, but I have no sense of what might be the normal rage.

I was hoping for a long term solution, i.e., headroom for any conceivable situation including even if we moved and our HT was in a bigger space, looks like it's time to search for a Plan B.

If I recall, Lonnie told me the MPS-1 had a "waveform limiter" circuit that was protecting the amp. I don't believe the other amps, or current designs have this circuit, not sure.

Lonnie provided great support and customer service during the 3 months I tried the amp. However, I just could not grasp the feedback saying it was the 80's, or I was driving the amp to its design limits. The 80's are very easy to drive, efficient speakers, that don't fall below 4ohms across the FR.

Something just was not right in my case where an amp with seperate monoblocks with those specs should even flinch. Now the Denon did show some signs of a clipping at +10 to +15 but never shut down. The MPS-1 sounded fantastic with no hint of clipping at all, however it would just shut off for no apparant reason.

My current Odyssey monoblocks (based on German Symphonic Line engineering) A/AB just keep going and going an going.

Sat, when you're rocking out on the XPA-2, at the point it's cutting out, what are the status LED meters doing? Are they pegged at the far the ends of the scale? I'm just curious if you can tell that the amp is being stressed (pegged-meters) or if it's cutting out early.

For the EE guys, is there any way that Sat could hook up an ohm meter to his system to monitor the resistance when the XPA cuts out? It seems that would answer the whole question. <4ohm = M80 problem, >= 4ohm = XPA problem.

The bizarre thing here is that the folks at Emotiva can build an amp that works. They know how to do it. As I've said, I have no problems with my LPA-1 + M80 combo at these 100db+ 'reference' levels we're talking about. None at all. And there are several others around here with the same setup. And the LPA-1 is/was their cheap amp.

But it makes no sense to me that their flagship multichannel MPS-1 and their top-end stereo XPA-2 can't drive M80's. It was absurd when Randy went through this, and it's still absurd that Sat is having the same problem. Since Emotiva claims the M80's are the problem, I'd love to see that data. They need to explain *why* the M80's seem to break some of their amps.

But from a troubleshooting perspective, I can see where Lonnie is coming from. It's still not the best response but I understand it. Since you changed speakers (were the Polks 4-ohm too?) and the XPA worked, then that points to the "problem" being the M80's. That "problem" is easily solved by getting your money back for the XPA and getting a different amp.

Either we're discovering that some M80's have an unusual impedance dip that's too much for their amps, or we're finding that some Emotiva amps aren't meeting their published specs with respect to 4-ohm speakers.

Thanks for the ideas, I will check out the LED thing, the amp is sort of off to the side and turned sideways so I have not monitored what the leds are doing when the amp cuts out, I will obviously have to do that (smacks forehead).

I did email Lonnie back yesterday that the speaker comparison was inaccurate because the Polks are 6 ohm speakers, he has not responded back yet.

The ohm meter idea also sounds promising if there's some practical way to hook it up, I will look into it.

I find it deeply satisfying whenever JohnK can combine theology and audio.

::bows to audio gods::

Well I finally caved in and plugged the Axioms into the 663 and the same thing happened only this time the Yamaha shut itself off at the peak.

I knew some of the Yamahas were not a good fit with the Axiom but the plan was to use the 663 as a pre/pro only, it's interesting that the Yamaha website states that their amps are stable down to, but not below, 4 ohms. I guess it doesn't mean much with such a low end model, an Amazon user states that the the 3800 drove the m80s no problem.

So my far pre/amp gambles have not paid off, it looks like I'll have to up the ante just to experiment more.

Still have to hope there is not something wrong with my power situation that is interfering with high current audio, since this is now 2 amps that have crapped out when push comes to shove, although I suppose the second example doesn't mean much . . .

Two different amps, both shutting down at high volume. Interesting. Could it be at all possible that you somehow have a defective M80 that's causing the problem?

Do you have a friend or family member with a Denon, H/K, Rotel etc. Something that is known to drive the M80s well.