Craig Anderton's Sound, Studio, and Stage

[144dB]

Hey all,

I've got a quick electrical/gear question for you...

My powered studio monitors are rated at 1.0A each, or 2.0A combined for the stereo pair. But the power specs list that amperage at 100W, which I presume is the peak power at the highest level/input sensitivity. I run them with the input sensitivity buried (lowest possible volume setting), and I'm wondering if the current draw is therefore less than 2 amps.

Do powered speakers and amplifiers vary their current draw based on output, or would you expect them to draw the same current regardless of the input sensitivity knob?

I'm just doing some electrical planning and my powered monitors are #3 on the list (behind the PC and my twin LCDs).

Thanks in advance,

Todd

[SoundMuppet]

There will always be a baseline draw when powered up. And then, as volume rises, so will power consumption. Mine get reasonably warm after a little use, but with no music playing, they return to ambient. That heat is from the amps having to push a little harder, and a few other components drawing more power too. If you want to know for sure, get one of those little gizmos that clip over the cable and tell you what the power consumption is. I don't recall the name of them.

[Anderton]

SoundMuppet aces the test.

[MikeRivers]

My powered studio monitors are rated at 1.0A each, or 2.0A combined for the stereo pair. But the power specs list that amperage at 100W, which I presume is the peak power at the highest level/input sensitivity. I run them with the input sensitivity buried (lowest possible volume setting), and I'm wondering if the current draw is therefore less than 2 amps.

First off, 100W is power. 1A is current. The wattage that's given for a loudspeaker is almost never the power drawn from the wall outlet, it's the output power of the amplifier under often unspecified test conditions. Since no amplifier is 100% efficient, the input power will always be greater than the output power.

A class A amplifier is the least efficient since it's biased so that it draws most of the current that it delivers to the output most of the time. You probably know "Class A" as describing a mic preamp which delivers so little power to its output that this is ore of a marketing description (though it's probably true) than an actual useful power consumption design specification. However audiophiles buy 15 W single channel "monoblock" amplifiers that draw 500 Watts from the wall outlet when idle and maybe 550 Watts at full volume.

Most of today's powered speakers use Class D or Class H amplifiers that draw practically no current when idle and can be upwards of 90% efficient. That's how you can get a 1200W amplifier in a single rack space, that weighs less than 10 pounds which, at peak power, draws less than 15A from the wall socket.

Amplifier manufacturers have some creative ways of coming up with power ratings of their amplifiers. Some are honest, but few tell you accurately how much current they draw, and that indeed varies (unless you're talking about one of those monster Class A amplfiers) with the amount of power delivered to the speaker, which is what determines the loudness. I remember seeing a box with "computer" speakers emblazoned with "300 Watts." They were powered from a 12 volt wall wart rated at 1 A (12 Watts). Who're you gonna sue?

The usefulness of the power and current ratings in the spec sheet or marketing materials is largely dependent on the reputation of the manufacturer.

[A. Einstein]

I have to watch my electricity bill, or my S&M hobby kills my budget, for example last night I learned that electrocuting a fat Bavarian Heidi uses more electricity then a slim Chinese beauty.

[144dB]

Hi guys, I should be clear... The label indicates that 1.0A and 100W is the power requirement, not the output.

[MikeRivers]

I should be clear... The label indicates that 1.0A and 100W is the power requirement, not the output.

In that case, plan on 1A. Watts = Amps x Volts x Power Factor so 120 V x 1 A would be 120 watts with a power factor of 1, but power factors for anything but pure resistance are always less than one because the current and voltage aren't in phase so you don't get both peaking at the same time.

[MrKnobs]

Clip on AC ammeters tend to work better for large current draws like air conditioner compressors or DeLorean based time machines. For smaller items like computer monitors this little guy works fairly well, and is actually kinda fun: http://www.newegg.com/Product/Product.aspx?Item=N82E16882715001 Terry D.

[blue2blue]

First off, 100W is power. 1A is current. The wattage that's given for a loudspeaker is almost never the power drawn from the wall outlet, it's the output power of the amplifier under often unspecified test conditions. Since no amplifier is 100% efficient, the input power will always be greater than the output power. A class A amplifier is the least efficient since it's biased so that it draws most of the current that it delivers to the output most of the time. You probably know "Class A" as describing a mic preamp which delivers so little power to its output that this is ore of a marketing description (though it's probably true) than an actual useful power consumption design specification. However audiophiles buy 15 W single channel "monoblock" amplifiers that draw 500 Watts from the wall outlet when idle and maybe 550 Watts at full volume. Most of today's powered speakers use Class D or Class H amplifiers that draw practically no current when idle and can be upwards of 90% efficient. That's how you can get a 1200W amplifier in a single rack space, that weighs less than 10 pounds which, at peak power, draws less than 15A from the wall socket. Amplifier manufacturers have some creative ways of coming up with power ratings of their amplifiers. Some are honest, but few tell you accurately how much current they draw, and that indeed varies (unless you're talking about one of those monster Class A amplfiers) with the amount of power delivered to the speaker, which is what determines the loudness. I remember seeing a box with "computer" speakers emblazoned with "300 Watts." They were powered from a 12 volt wall wart rated at 1 A (12 Watts). Who're you gonna sue? The usefulness of the power and current ratings in the spec sheet or marketing materials is largely dependent on the reputation of the manufacturer.

My audiophile buddy, who has a Lexus-priced sound system but drives a 17 year old Honda (OK, he's got a new Prius waiting in the wings, he just needs to suck the last few miles out of the Honda, which is nearing the quarter-million-mile mark), has been running a pair of Class A 300 watt output tube monoblocks (want to talk about heating up a room?) but sent them back to the maker for a rebuild. To tide himself over while the house-heaters were in the shop -- and check his assumptions -- he picked up a similarly expensive Class D amp (from the same maker!)... Not being all that up to the mo', I was sitting there thinking, Huh? Class D? Isn't that just for big PA systems and the like where max efficiency is the byword? But, I had to admit, these things sounded really nice, better than I remembered the tube amps (hard to do an ABX when one of the devices is on a repair bench 300 miles away). Of course, they're going through some very nice speakers, fed from a very nice control amp, a 'table/arm combo that cost about $10K new, separate CD deck and converters, etc. But, yeah, Class D... not just for pounding the crowd anymore, I guess. BTW, I went looking for info on my original Event 20/20bas -- I suspected they're AB and that appears to be true -- but what I found at the Event page for the 'all-new' 20/20BAS [note change of capitalization!] rather shocked me. While claiming the new speakers are an improvement that retains the unique blah blah blah, I read between the lines a little bit and realized that while "bas" on the original models stood for biamplified speakers -- the "BAS" on the new line-replacements apparently only stands for "bad ass sound"... The explanation is in the specs, they replaced the original 200 watt (130/70) biamp system with an 80 watt single amp! [That said, they managed to eke out a couple more Hz of range at the bottom, taking it down to 35 Hz +/- 2 dB.] Now, for sure, I always found the 200 watt/speaker original biamp system to be wildly overpowered for my needs -- and, AB or not, they stayed warm enough all the time -- enough to add a few degrees to a small room, I'm guessing. Does anyone have any background scoop on Event these days? I was a bit flummoxed by their marketing of the Opal and now I really don't know what to think about them. PS... Isn't it cool that I haven't accidentally closed any threads lately? I wish I could claim that it was because I finally got used to the wackazz way Chrome treats (or doesn't treat) the tab order on a page (which is entirely different than how FF does it and ends up putting your cursor on the "Close this thread" checkbox [if you are a mod which for reasons beyond most of us, I am] instead of the Post Reply button when you tab out of the edit window). Anyhow, I finally managed to clear out whatever the heck it was in my registry that had been hosing up FF since v 10.01 came out in January or February (no matter how many times I tried clean installs of FF)... either that or the latest FF version (up to 15, about one a month!) got 'fixed.' Or something. Who cares, it's great to have FF back on my rig.

[A. Einstein]

the large high resolution speaker start to work properly at 300 Watt, the FM Acoustics 800 amps for the large ones delivers 5000 Watt with ease,

the nearfields work perfect at 5 Watt, for the nearfield I use a digital amp the loudspeaker company recommended

[MikeRivers]

Does anyone have any background scoop on Event these days? I was a bit flummoxed by their marketing of the Opal and now I really don't know what to think about them.

They stopped coming to AES and NAMM shows so I don't see them any more, nor do I see ads for them in what's left of the trade magazines, but apparently they're still in business.

That Opal was supposed to be really something, it got some rave reviews when it first came out (perhaps because they invited some magazine editors out to the factory for an intro) but I don't hear anyone talking about them these days. I think that Adam, probably while Dave Bryce was at the marketing helm, kind of took over that price/performance point in the market.

[philbo]

Hey all, I've got a quick electrical/gear question for you... My powered studio monitors are rated at 1.0A each, or 2.0A combined for the stereo pair. But the power specs list that amperage at 100W, which I presume is the peak power at the highest level/input sensitivity. I run them with the input sensitivity buried (lowest possible volume setting), and I'm wondering if the current draw is therefore less than 2 amps. Do powered speakers and amplifiers vary their current draw based on output, or would you expect them to draw the same current regardless of the input sensitivity knob? I'm just doing some electrical planning and my powered monitors are #3 on the list (behind the PC and my twin LCDs). Thanks in advance, Todd

Idle power (in engineering they call it quiescent power) is generally very low in solid state gear (except class A power amps). It's low enough to be considered negligible. The actual power draw is dependent on the audio input. If you feed it a 400 Hz sine wave at +10 dBm or so (just below clipping), you'll get the maximum power consumption (and draw 1A of current) as listed on the face plate. Note: I do not recommend that you do this, for the sake of your ears, your speakers and the general health of the electronics. Just because a VW Beetle will do 130 mph while falling off a cliff doesn't mean it'll be good for it! So, yes, you are right, it will draw a lot less than 1A of current with no input signal.

[Beck]

Clip on AC ammeters tend to work better for large current draws like air conditioner compressors or DeLorean based time machines.

For smaller items like computer monitors this little guy works fairly well, and is actually kinda fun:

http://www.newegg.com/Product/Product.aspx?Item=N82E16882715001

Terry D.

Yep, these are great! I've got two of the P3 Kill A Watt units for studio use, alternative energy stuff I'm involved with and just general use around the house.

And to the OP, yes everyone got it right in their replies.

[Beck]

rather shocked me. While claiming the new speakers are an improvement that retains the unique blah blah blah, I read between the lines a little bit and realized that while "bas" on the original models stood for biamplified speakers -- the "BAS" on the new line-replacements apparently only stands for "bad ass sound"...

Are you serious? I really don't like marketing people. I have to hold my noise sometimes when buying things because of stuff like this. There's no getting away from it though unless I just built everything myself. Too much work. Funny too because I was just thumbing through an old issue of EM from 1989 as I often do for the fun of it and was reading an ad for AKG K270 headphones... the blurb explaining why you need them because they're digital ready and older headphones just can't do justice to digital sound. That was right at the beginning of all that digital ready bullshit companies were using to pitch products, and some people still actually believe all that nonsense. Needs to be a check box when we buy things that says something to the effect of, "I'm buying this product despite the bullshit I read from the professional liars you employ in your marketing department, not because of anything they've said that would make me want to by this product." Salespeople are all the same... used car salesmen, TV preachers... whatever. Turns my stomach. At one time I had the perception that certain companies were more or less legit and above all this crap, but no not really anymore. I remember when infomercials seemed so over the top because of the blatant misinformation and circus atmosphere, but now everyone is a whore, including the paper mags and websites that allow this sort of marketing into their publications.

[onelife]

First off, 100W is power. 1A is current....

That is true but there is also a direct relationship between power and current.

In the context of the OP we can assume that a circuit that requires 1A plus overhead to produce 100W will require 2A plus overhead to produce 200W (if all these numbers fall within normal operating parameters).

[Red Mastering]

instead of the Post Reply button when you tab out of the edit window). Anyhow, I finally managed to clear out whatever the heck it was in my registry that had been hosing up FF since v 10.01 came out in January or February (no matter how many times I tried clean installs of FF)... either that or the latest FF version (up to 15, about one a month!) got 'fixed.' Or something. Who cares, it's great to have FF back on my rig.

great post! myself I changed my valve power amp (beautiful sounding amp) to class -D Hypex based amp not only my electricity bills went down (apparently with class A you pay as much as 10 times) but Hypex proved to be simply better sounding amp, cleaner, more transparent and precise - much better for working with audio much recommended!

[Anderton]

great post! myself I changed my valve power amp (beautiful sounding amp) to class -D Hypex based amp not only my electricity bills went down (apparently with class A you pay as much as 10 times) but Hypex proved to be simply better sounding amp, cleaner, more transparent and precise - much better for working with audio much recommended!

Welcome to the forum, we have quite a few mastering engineers hanging out here Class A is definitely the least efficient possible circuit architecture, and of course, class D is highly efficient. But I would never have thought that it would make such a visible difference to your power bill!

[MikeRivers]

Class A is definitely the least efficient possible circuit architecture, and of course, class D is highly efficient. But I would never have thought that it would make such a visible difference to your power bill!

Well, you need a really big amplifier and you need to leave it on all the time. I pay roughly a dime per kWh. So lets say your pure Class A amplifiers have about 20% efficiency and 100 watts per channel. That's a kilowatt in, and since class A draws pretty much the same current from the power supply regardless of what's going into it, that's about a buck a day assuming a 10 hour working day.

A Class D amplifier is about 90% efficient, so the same 200 watts would require about 225 watts going in. That's about a quarter a day, if they're delivering full power all day which isn't very likely unless it's a dance club instead of a mastering suite (in which case it'd be about 5,000 watts). So conservatively, figure on a 30% duty cycle and it's less than a dime a day.

That would save about $27/month, enough to cover a triple venti latte a week, or a couple of good beers a week.