How much power is enough power

[Goliath]

Your 800 diamond is a good example in theory. I say in theory because I would think that people who own such speakers probably have a large room and enjoy music with great DR, so a 50W amp probably won't do it. OTOH in my smaller 2 channel room and I enjoy <75 dB average loud, I would not hesitate to drive it with my smallest amp or even my old AVR-3805

Fair enough. I know a handful of people who own the N802's, have relatively small rooms and don't sit very far from the speakers. Not only that, they don't listen at crazy SPL either. In each case they have 300 watt+ power amplifiers into 8 ohms, almost doubling into a 4 ohm load - suffice it to say, they cost an arm and a leg. But it would be interesting to know, in their case, what the maximum power draw actually is at their maximum listening level. IME, it would probably be a fraction of the amps capabilities.

Of course you get some people who claim big power is needed even at low listening levels and I've never really understood that. Still don't.

 

[avengineer]

The thing about a portion of the impedance curve being low is that signals don't stimulate that portion all the time. The need for "high current" would exist for very high level peaks with energy distribution centers in the low impedance portion of the curve, which is most likely statistically less probable than most people think.

 

[Goliath]

Speaking of the AVR-3805, that's a pretty decent amp even if it's quite old today.

 

[fmw]

I guess when people keep on saying that low impedance speakers need huge current reserves I wonder how that determination was made without considering all the other variables that determine how much power is actually needed, and listening levels is probably the big one.

Most likely by reading magazine articles and internet posts. The more appropriate statement is that amplifiers can overheat if operated into a low impedance at full power for enough time to do the job. Virtually none of us use our amplifiers at full rated power for long enough to overheat an amplifier. If we did, we would suffer hearing loss. I'm not sure why you think B&W speakers are "challenging." In my experience driving them is pretty straightforward. I used to drive my 802 matrix speakers with a 50 watt per channel amplifier. Perhaps things have changed over the years and I'm just out of touch.

Amplifiers don't "sing." They amplify. They take audio frequency waveforms and increase their amplitude. If they aren't powerful enough for the application, they clip and the sound of a clipping amplifier is pretty obvious. Simply having more reserve power doesn't affect sonics as long as the amplifier doesn't clip. It simply provides more reserve. There is nothing wrong with having more amplifier than you use. But you shouldn't expect more power by itself to improve the sound of a system.

 

[Goliath]

The thing about a portion of the impedance curve being low is that signals don't stimulate that portion all the time. The need for "high current" would exist for very high level peaks with energy distribution centers in the low impedance portion of the curve, which is most likely statistically less probable than most people think.

Yes, because music has a crest factor - it's not as if people are listening to steady state sine waves at low impedance which is what you get with amplifiers on a test bench. I've always been interested in this. Probably the most extreme example I can think of is that I recently had a debate with someone over this. The guy has Tannoy Kingdom speakers (around 98 dB 1 watt) and he claims that his Krell 600 watt into 8 ohm amplifier was not cutting it. He was using Yello as a test for his source material.

He also said his listening levels were not terribly loud. Now a case like this is extreme because it's really unbelievable. 600 watts, seated 4.5 meters away, 98 dB 1 watt speakers and he said the amplifier was not cutting it. Apparently the Kingdoms can reach down to 12 Hz and have impedance minimum of 2 ohms or below. Still, I can't imagine how such a thing could be possible with such a super sensitive speaker using a monster amp like the Krell. Long story cut short, he replaced the Krell with bigger Mcintosh monoblocks and he says they run like a dream.

 

[PENG]

Speaking of the AVR-3805, that's a pretty decent amp even if it's quite old today.

You've got that right, that thing has a very decent size transformer in it. One thing I like about Denon is that they are not shy to shed weight by employing/embracing technology, unlike EMO who tend to make their stuff as heavy as they can. There is no way I would buy a 75 lb (the original) XPA-5 and only end up with a 1200 VA transformer and 60,000 uf total capacitance, my 40 lb Marantz has pretty much the same in it but 35 lbs lighter. I do have respect for their XPA-2 and the newer ones though.

 

[Goliath]

I'm not sure why you think B&W speakers are "challenging." In my experience driving them is pretty straightforward. I used to drive my 802 matrix speakers with a 50 watt per channel amplifier. Perhaps things have changed over the years and I'm just out of touch.

The measurements for the B&W 800 Diamonds can be found here :

B&W 800 Diamond loudspeaker Measurements | Stereophile.com

According to John Atkinson, these speakers are power hungry. But I really don't know what that means.

 

[PENG]

The measurements for the B&W 800 Diamonds can be found here :

B&W 800 Diamond loudspeaker Measurements | Stereophile.com

According to John Atkinson, these speakers are power hungry. But I really don't know what that means.

Come on now, you know he's talking about the impedance dips coinciding with large phase angles, surely you do, and stop pretending will you..

 

[Goliath]

Come on now, you know he's talking about the impedance dips coinciding with large phase angles, surely you do, and stop pretending will you..

But how important is that really and can one really say these speakers are power hungry and furthermore, can one make a universal claim that these speakers need a big amplifier? My thinking is that no, you can't. Or ... it depends.

 

[ImcLoud]

Yeah but who operates their systems in that way?

Someone who likes to learn the hard way, When I had my 5 ch Polk system which was a pair of LSi25's an LSiC center, and a pair of LSi9s for surrounds, it made short work of a couple $900 yammy AVR's (Thank you- Best buys return policy), so I went up a couple rungs with a high end Denon, which held in there but ran HOT, and then I finally went with separate B K amps and they ran great, speakers noticeably sounded better, no more burning chipset smells, and they lasted. Then I sold that 5 channel to my brother who burnt out his Marrantz in short order....... Them speakers sounded so good when played loud, you didn't need a large amp just something strong a decent 150w per ch amp did fine...

But I know when I put a movie on, like I will do after dinner tonight, (I bought Pain and Gain on Amazon, wanted to see this since I watched the docu drama about the true story- some people are really sick..) I am going to play it loud like Im in a theater, I wont hear the kids fighting, I won't hear the phone ringing, my wife saying how the movie is too violent and has too many swear words, I won't hear the neighbors lawn mower, I won't hear anything except the music, dialog, and sound effects from the material on my TV, and life will be good for 128 minutes, I will zone out and nothing else will matter... I just need that once a week to keep my sanity, there will be so much sound that I won't even be able to think about anything except the movie.... Now for me the amp section in a 500w avr just won't get the job done, my 1000 watt amp and dual vtf2's will do just fine though...

My brother in law comes over to watch a movie and now knows better, the first few times he said "wow, thats loud, wow isn't thats too loud" and then something else that I couldn't hear because every time I heard him talk I turned it up more... He got the point, I don't want to talk during a movie, I don't want to discuss how you used to have a car like that, or how you had a friend who did the same thing as the main character, or how you remember when you were that age, blah blah blah blah.. Turn it up until it hurts, then go back 1db...

 

[Irvrobinson]

As to the presence of clip protection, it's not likely in this case. The maximum short term power is a fraction of a dB more than steady state (135w vs 150w), and the power spec is done at .08% THD. A clip limiter has an attack and release time which affect both the effectiveness as a clip protector, and distortion. To be an effective clip protector it needs to attack and release fairly quickly, which would preclude .08% at full power by quite a ways. Also, clip protection limiters are not frequency selective. Clip protection limiters are not typically found on AVRs, but are much more common in power amps, where there is usually a front panel indicator when they are active.

How do you figure clipping limiters increase distortion? Regardless of how they're triggered, which can be comparator circuitry or simple voltage level triggers, clipping limiters are effectively just gain reducers. I'm not seeing how they introduce distortion.

Not all amps that have clipping limiters have LED indicators for their operation. I'd had some that don't, and have one now that doesn't give any indication of the clipping limiter being in operation.

Some clipping limiters have reaction times and some don't. The voltage limiters typically do, like 100ms or so, but the ones that use comparators usually work continuously and without a significant lag.

Regarding your discussion of the amp specs, that tight window between the FTC and peak power ratings is what led me to think there might be voltage limiters in the design.

I agree that AVRs don't typically advertise clipping limiters, but the voltage limiting type are so simple that I've always wondered if receiver designers just slip them in with the nine hundred other features in an AVR.

 

[Adam]

I agree that AVRs don't typically advertise clipping limiters, but the voltage limiting type are so simple that I've always wondered if receiver designers just slip them in with the nine hundred other features in an AVR.

Would that circuitry be easy to spot?

 

[Irvrobinson]

Would that circuitry be easy to spot?

No, unless you were a circuit board designer and they used discrete components for the limiter.

 

[Adam]

No, unless you were a circuit board designer and they used discrete components for the limiter.

In that case...no.

 

[Goliath]

So looking at the B&W 800 Diamond measurements, would you guys say it's a challenging load? That you need a super duper high current amplifier for them? Or that you need a super duper high current amplifier assuming certain conditions are met, conditions that most people gloss over?

 

[fuzz092888]

So looking at the B&W 800 Diamond measurements, would you guys say it's a challenging load? That you need a super duper high current amplifier for them? Or that you need a super duper high current amplifier assuming certain conditions are met, conditions that most people gloss over?

It's definitely not an easy load. Especially when rated at 8 ohms with dips down to 4 ohms and -52degree phase angles.

Not like this one

 

[Irvrobinson]

It's definitely not an easy load. Especially when rated at 8 ohms with dips down to 4 ohms and -52degree phase angles.

Perhaps, but I doubt any reasonably robust solid state amp would have a problem with them, especially any amp likely to be used with $20K speakers.

 

[fuzz092888]

Perhaps, but I doubt any reasonably robust solid state amp would have a problem with them, especially any amp likely to be used with $20K speakers.

No disagreement there

 

[Goliath]

It's definitely not an easy load.

Okay, but is it not an easy load at any given SPL, or is it not an easy load at more spirited volume levels, or not an easy load assuming assumption 2 + lots of challenging deep bass material, or not an easy load assuming you're in a gymnasium, or a combination of assumption 2, 3 and 4?

So what kind of amp would you need to drive these speakers? Most entry-level AVR's can deliver 100 watts+ into 2 channels using continuous sine waves into 8 ohms and have some reserve into 4 ohms, although admittedly don't double down. However using resistive loads and continuous sine waves is about the most challenging and stressful test that an AVR will ever face in its lifetime and given that musical signals have a crest factor and are many times less stressful than bench testing, AVR's can usually have quite a bit more headroom than what you see on the bench.

Or do you need a big hulk of an amplifier because that's what people normally use?

 

[Irvrobinson]

Okay, but is it not an easy load at any given SPL, or is not an easy load at more spirited volume levels, or not an easy load assuming assumption 2 + lots of challenging deep bass material, or not an easy load assuming you're in a gymnasium?

So what kind of amp would you need to drive these speakers? Most entry-level AVR's can deliver 100 watts+ into 2 channels using continuous sine waves into 8 ohms and have some reserve into 4 ohms, although admittedly don't double down. However using resistive loads and continuous sine waves is about the most challenging and stressful test that AVR will ever face in its lifetime.

Or do you need a big hulk of an amplifier?

The answers have been posted here already, amplifier requirements can be calculated to a certain degree.

Are you asking your last question just to generate conversation? Would anyone try to drive $20K speakers with an entry-level AVR?