Axiom Home Page Forums General Discussion Technical Questions Impedance graph for m80's?

has anyone seen a impedance graph for the 80's??

just curious

It has been posted often...

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

"Soon after that Emo tech support emailed me back and reported that he had talked to an Axiom engineer earlier today who said that the M80's could dip as low as 2.6ohm if driven hard... and since the XPA-2 design is not current limiting, the amp would try to push 800 watts, which would kick the protect circuit."

this is a quote from the emotiva lounge...

Who was the engineer? I don't think the impedance would change due to more power being applied.

here is the link to the post..
I just happend to come across it and thought it was interesting.

http://emotivalounge.proboards54.com/index.cgi?board=amps&action=display&thread=4057

sos.

I've dealt with Emotiva, as most of you know. I can about guarantee you that noone from their company would have taken the time to call Axiom, they only have 2-3 people that answer the phone, Lonnie, Bob, and the owner.

As an Electrical Engineer, I can tell you that the impedance of a load does not dip on higher power (read current or voltage) supplied. Unless of course something fried out in your system and you short circuited.

Impedance is a combination of the "real" load (resistance in the x-axis) and the "imaginary" load (reactance in the y-axis). It does not change as supplied power changes.

I guess there is just a lot more reactance over at Emotiva.

Chet, as has already been pointed out, no electrical engineer familiar with speaker technology would claim that a speaker being "driven hard" could in some way lower its impedance. So the quote from Emo tech support appears to be pure BS.

Sigh... more confusion.

Fogetta 'bout it!

On the other hand I feel vindicated that I am not the only one to experience trouble with the combo of the XPA2 and M80s (with precisely the same characteristics, reference volume in a big (?) room during HT sound effects); I had begun to suspect that my unique system was somehow the culprit. Although I feel better to know it is not just me, I would be much happier, especially with regard to future component purchases, if I understood exactly what the problem was in the handshake between the two components, although I suppose the rational response at this stage would be to continue to avoid what MAY NOT WORK at the level of concrete components, even if at this stage no one can explain why they don't work/play well together, except to point fingers.

Well studying the thread further I am not sure how to explain, flyboy909 experienced a similar problem in a room about half the size (4300 rather than 7300 cu ft) and also during time of moderate playback volume; the only real commonality was not reference volume but rather HT sound effects (given my experience and commonsense logic presumably LFEs). I give up!!! Nah, never, I love a mystery!

so someone is fibbing???

Hi turbo16v,

As JohnK and others have pointed out this is pure BS. In fact, the M80 is a relatively easy 4-ohm load. I have said all along that Emotiva has a problem with its amplifiers and 4-ohm compatibility--whether that's due to inadequate current in the Emotiva power supply or wonky protection circuitry is unknown.

One thing is certain: Emotiva's engineer called Tom Cumberland, Axiom's chief R&D engineer, and acknowledged that there was a problem in the Emotiva XPA-2's protection circuitry and that he thought it could be solved.

If one closely examines the M80 impedance curve, it is much closer to a 5-ohm impedance. The curve is quite smooth and only touches 4 ohms at a couple of points in the spectrum. Much of the time, the impedance is well above 4 ohms.

If the M80 was a difficult 4-ohm load, why is it that entry-level $300 Denon and Sherwood Newcastle AV receivers can drive the M80s to loud, clean playback volumes with no shut-down or problems?

Regards,

I remember when Emo's engineer sent me instructions on how to remove the protective waveform limiter circuit from the amps motherboard, I think NOT.

Yes,it is strange that a regular reciever can run M80s without shut down issues and that Emotiva amps can run other 4 ohm speakers without shutdown issues.I hope whatever the issue is gets sorted out because they are both decent companies and do sound great together.

Suddenly I'm feeling really leery about that UPA-2, and more than about whether it would make a difference or not.

Rotel+M80s=no problems

Like Axiom, Emotiva has a 30 day return policy.If you feel it makes a difference, great.If not you send it back.Myself and my audio buddies have done several AB comparisons with my reciever and a friends reciever both running on their own and with my LPA1 hooked up.To us the improvement was quite noticeable.But you'll have to hear for yourself, every situation is different.

Does anyone here use a NAD amp on their M80s?

They have and work great, no problems.

Tks, Rick.

I just got off the phone with Emotiva, and the support person(Chris I think) told me the same thing, that M80's dip down to 2.6ohm and that causes the AMP to go into protect mode. The only reason I was looking at the amp is because I have M60's and I'm getting a set of M80's and I'm not sure if my RX-V1400 can drive them well.

Emo+M80s=

It would be nice if someone asked them the basis for their statements. Back when I was having issues, Lonnie, one of their chief engineers had never heard of Axiom. What is the basis of their statements, sounds like smoke of callers a$$'s.

There's a fairly easy way to test their claim. Buy something like the IRP1000:

http://www.isotekcorp.com/dataSheets/dataView.asp?ds=irp&orderURL=

It's a power resistor that is capable of handling 400W in free air, and has settable inductive (imaginary) and non-inductive (real) loads. Set them both to around 2.8 ohm (the square root of 8), which would result in an impedance of 4 ohms with a 45 degree phase (half real, half imaginary since impedance equals the square root of resistance squared plus reactance squared).

Hook it up to the Emotiva and see what happens. If it trips, then the Emotiva has problems with a 4 ohm impedance load. If it does not trip, try slowly decreasing the resistance and reactance (non-inductive load) to see where it does trip the amp.

Steve

Electro-Geek Throwdown!

My money's on Steve.

I'm with Randy; unless Emotiva got completely different information FROM AXIOM than has been published elsewhere, or they independently measured M80's and got different results than Axiom publishes, I think the explanation boils down to "it's not us, it's them. And here's some made-up stuff for justification".

So is this a problem with all XPA2 amps or just a select few? Do other Emotiva amps also have issues with the M80s?

paul

All I can say is that I have a receiver (not a dedicated power amp), that is only rated at 120W. It's the Denon AVR-3806. It has NEVER tripped out on me with the M80s. 2 years running, 1/2 inch clearance over the vents. I have never had a problem.

I've had my Rotel amp for going on 6 years, without any problems.

My LPA-1 ran my M80's for a year without a shutdown. Since New Years eve I have been running the XPA-5 without a shutdown. I am thinking about getting the XPA-2 maybe I should'nt!?

Mistico, welcome. Your 1400 can certainly drive the M80s to a very loud level. Despite the Emotiva comment, the M80s are in fact a quite easy load as speakers rated at 4ohms go(possibly a 6ohm rating would follow typical rating practice more closely). You'll find out whether the 1400 drives the M80s loud enough and long enough to fit your normal(almost any amplifier can be forced to shut down)use pattern. There's no good reason to assume that it won't be entirely satisfactory and go off looking for another amplifier at this time.

Thanks, Johnk.
I actually joined the forum in 2004 but haven't posted since. I remember many of you from back then. Good to see many of the same folks still here. Did the forum undergo a rebuild? I had to reregister.

Back to the thread now...:)

I believe the word is "lifers."

Bren R.

Why did I have a feeling that when someone asked about impedance graphs of M80's, that Emotiva would come up again.

For the ongoing record, my M80's work perfectly with my Emotiva LPA-1. Zero problems. None. My system will play louder than I can tolerate (>105db, from my seating position), and sounds lovely. So there is at least ONE example of M80's playing nicely with Emotiva amps. My den is proof. All are invited over to listen. Free beer even.

But of course, others have had problems with M80's + various Emotiva amps. If we grant that both Axiom and Emotiva are being truthful about their products (which I believe they are), then every Emotiva amp should be perfectly capable of driving M80's. But they can't. So that means that either Axiom or Emotiva has a Quality Control problem. Based on my experience with the Emotiva LMC-1 prepro, I'd be betting against Emotiva on that duel.

In my company, if we discover a problem with one of our products, we buy it back from the customer and test the living heck out of it to figure out exactly what happened and under what conditions. We solve the problem. And then we improve our product so that it never happens again.

It's a shame that Emotiva can't or won't get to the bottom of this. But at this point in time, it's a finger-pointing game between Axiom and Emotiva. Of course we're here, so we're mostly going to side with Axiom. And why shouldn't we? Alan, you are exactly right - other 4-ohm-minimum amps don't have problems with M80's. Sooo.....

And yes, I'm sure the A1400 will work perfectly with M80's. It better, considering it's a $3,850 amp.

<---[frantically trying to change flight itinerary]

Does Emotiva use a different design in their power supplies (or in general) than say Denon, Harman Kardon, Sherwood Newcastle etc which have a history of having no issues with the M80's?

Wolf, I believe the amps from Emo that have had issues are the ones that included a waveform limiter circuit. The MPS-1 was the first to introduce this special little nifty pos circuit. I believe the XPA series also have this nice little wonderful high tech option that will shut down your 80's.

You mean the 80s will shut down the amp, right?

yeah, because when they are driven realllll hard, they will drop to below 0ohms, according to Emo Techs.

Oh Dear!! Do you realize what you’ve done!!!!!

If they drop to negative ohms do the speakers start sucking sound out of the room?

Nothing so grand. At that point, the speakers power the amp, and you have a crude, but workable, perpetual motion machine. I could explain it, but you wouldn't understand.

Well, not MARK'S room.

What the inebriated cute rat said.