Chances of overheating an amp rated for 4 ohms when running a 3 ohm Center channel speaker

P

PENG

Audioholic Slumlord
I recall the 1 ohm test was Dynamic Power, not continuous power.

But I don’t know if it’s 20 ms or 200 ms dynamic power.

But in reality, though, both 20ms and 200ms are much less than 1 second of time. 1000 ms = 1 second. So does it truly matter? :D
I am sure no AVR can output 170 W into 1 Ohm continuously. AVtech probably follow the IHF protocol.

I mainly listen to classical and jazz, so I would like to see 200 ms as the minimum for dynamic rating. The 20 ms is just better than nothing. Yes both are very short duration it 200 ms can probably cover the most music transient peaks.
 
P

PENG

Audioholic Slumlord
Very few loudspeakers have greater than 60 degrees phase angle, and they typically only get that bad within relatively narrow bands. Yes phase angles need to be considered, and I have pointed that out years ago, not long after I joined this forum, and noticed the frequently referenced P=VI power formula without mentioning the power factor, but I also feel that the related issues might have blown out of proportion at times. Reality is, never mind real power amps, even receivers are not blowing up regularly, not in the old days and even less chance now that most of the newer models are electronically protected against damages due to thermal overload, overcurrent, and short cct.

As far as I know, mid level receivers such as D&M and Yamaha's seem to standardize on output devices rated 15 A and every D&M units now come with fans build in. So everyone can relax and enjoy, just go easy on the vol up button and protect our hearing.
 
M Code

M Code

Audioholic General
The majority of AVRs use fans as to stay within UL/CSA/CE temperature standards....
Fans are much cheaper than adding more inches of expensive metal heat sinking..

Just my $0.02... ;)
 
R

RussellS

Enthusiast
I now have time to comment on this thread.

It goes back to points that are difficult, that I have often alluded to over the years. This does relate to the fact that bench testing of power amps with resistive loads is of limited use and hides a lot of problems.

Amp and speaker manufacturers would rather not talk about, and most others, for that matter as it is complex. Viewing a speakers impedance curve alone is also of limited use. You have to consider the relationship of current and voltage as well as impedance. This is the thorny issue of power factor. This gets us to the fact that the speaker amp interface not only makes a difference as to how amps sound, but more importantly whether a given speaker is likely to blow up an amp.

The OPs question is a classic case in point. The Magnepan speakers present an almost constant resistive load with phase angles close to zero throughout the range. So there will not be retained energy in the output devices. So even though the impedance may be 3 ohms, I would say those speakers are very unlikely to blow up his amp. I would not worry about the possibility of them doing so.

Since the inception of getting to know Peter Walker of Quad and tinkering with the early 405s, I have had a huge interest in these two issues. First is designing speakers less likely to blow amps up and secondly making amps more stable under a variety of loads. This was also a great interest of Peter Cooke's, founder of KEF. He carefully designed his crossovers to avoid amp busting loads. This is also a major reason that I think that amps actually belong in speakers. I firmly believe that speaker and amp should be designed as an integral unit.

I referenced this article previously. It is an important if difficult to understand issue. All of you would do well to try and understand it, and what it that that makes different speaker designs, and different speaker combinations potentially lethal to the amp.

So if your amp or receiver blows up more likely than not the responsibility lies with both amp and speaker, whatever the speaker manufacturer says the "nominal impedance" is. I don't think there was ever a more useless and misleading spec. than a quoted speaker impedance number.

I have not been very active here of late, as I'm busy working at our new home built. I will try and post an update on the projects there this weekend if I can.
Your post is the type that makes me glad I found this site. High-end stereo stores seem more like car dealerships where they push products that have the highest commission and never provide the buyer common sense audio advice. (maybe that is just the way audio stores work in general) One must have more than a marginal understanding of equipment before making the investment.

I was considering selling my current amp and buying a multi-channel amp. From what I can gather from your post, it would seem that I could switch from an Audio Research DS450 to a multi-channel amp like the ATI AT525NC amp and still have enough power to drive the Maggies. If I am even close on that concept, just give me a thumbs up. thx.
 
mtrycrafts

mtrycrafts

Seriously, I have no life.
Wow.

I thought the “Power Cube” measurement was gold standard. But it only use 20 ms of power, not continuous?
Well, it is as it measures power with phase shifts.
Audio Precision has the power cube device
https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/
This apparently does both but didn't mention the burst duration.
Researching the Internet indicates a 20 ms duration, 20dB signal drop for 480 ms then 20 ms.

I believe The Audio Critic described their bursts as 20 ms.

So, unless the AP test specifies or shows the two cubes, continuous and burst, not sure what to assume.

And, sine wave test tone measuring is very hard on amps compared to music signals. I would not sweat it.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
Reality is, never mind real power amps, even receivers are not blowing up regularly, not in the old days and even less chance now that most of the newer models are electronically protected against damages due to thermal overload, overcurrent, and short cct.

So everyone can relax and enjoy, just go easy on the vol up button and protect our hearing.
Interestingly enough, I think the majority of the population (who only own AVR and have never owned separate amps or speakers with built-in amps) do just relax and go easy on the volume knob.

It’s the audiophile crowd (the minority of the population) who actually needs to relax, take a step back, smell the roses, not overthink, and enjoy. :D

Like you said a few posts ago, any AVR can power even a 1 ohm load as long as the volume is not too high.

Listen to sensible volume, protect your hearing, and enjoy. :D
 
R

RussellS

Enthusiast
Or, one will have a very short life span of their hearing being golden. ;):D
As one who performed live music while standing in front of a horn section in the 70's can attest, yes exposure to loud music does take its toll.
 
P

PENG

Audioholic Slumlord
Your post is the type that makes me glad I found this site. High-end stereo stores seem more like car dealerships where they push products that have the highest commission and never provide the buyer common sense audio advice. (maybe that is just the way audio stores work in general) One must have more than a marginal understanding of equipment before making the investment.

I was considering selling my current amp and buying a multi-channel amp. From what I can gather from your post, it would seem that I could switch from an Audio Research DS450 to a multi-channel amp like the ATI AT525NC amp and still have enough power to drive the Maggies. If I am even close on that concept, just give me a thumbs up. thx.
Don't let anyone convince you the AT525NC is not powerful enough for your Maggies, unless and until the following calculator tell you otherwise.

https://myhometheater.homestead.com/splcalculator.html
 
highfigh

highfigh

Seriously, I have no life.
So....longer duration like 200ms or more is better than shorter duration, but you think 20ms is “close enough”? :D
Depends on how well the heat sinks can draw heat from the output devices. If the amp can live through a long term event, yes- I think it would be better but I don't know if it's actually necessary.

Rockford Fosgate used Power Cube to show their amps' ability to handle difficult loads (and I have a folder full of Power Cube results for various brands of car power amps) but I don't remember if they spec'd it for a particular duration.
 

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