How an amp can get underpowered?

[adrhc]

Let's suppose I have a 50W (max continuous output power) 6ohms amp and 2 x 100W 6 ohms speakers; the audio source is some computer with an optical output.
What should one do to get his amp underpowered (not that I want that)?

My (faulty) reasoning is below.
Let's suppose the computer volume is set to 10% (aka very low); in this situation, I guess I can switch the volume (is it an audio-volume button or a power/energy button?) on the amp to maximum because the speakers will still play low, right? If I switch the computer volume to 100% then I guess the speakers will ask for more energy from the amp which will have not enough (50W < 100W) - hence it becomes underpowered.

If my reasoning above is bad then the thing I don't understand is how the speakers know they have to ask for more energy from the amp? How do they know how much loud they should play?

PS: I don't own an amp though I read a lot about them, enough to be more than able to setup and use it
PS: I don't want to underpower an amp, I only want to understand the process

 

[Mikado463]

Not exactly sure of what you're getting at. Why would you want an amp to be underpowered ?

 

[PENG]

Let's suppose I have a 50W 6ohms amp and 2 x 100W 6 ohms speakers; the audio source is some computer with an optical output.
What should one do to get his amp underpowered (not that I want that)?

It is not clear what you mean by "...to get his amp underpowered..."

Regardless, you have not provided enough information. For example, a 50 W 6 ohms amp does not say whether the 50 W is average output, or peak output, and it does not say at what distortion level.

Same idea for the 2X100 W 6 ohms speakers mean even less, as for speakers we would also need to know the speaker's actual impedance versus frequency, not just 6 ohms that could be at just one frequency point, and the 100 W could be average, peak, or whatever. And then there is another important spec, that is, the speaker's sensitivity, that is usually given as X dB/2.83 V/m, something X dB/W/m (that's not as useful). For example, a speaker may have sensitivity spec of 84 dB/2.83V/m, that, compare to a speaker with spec 90 dB/2.83V/m, the one with spec 84 dB would need 4 times as much power to make the speaker as loud as the 90 dB sensitive speakers.

If you want to learn more about this, you can google the info, or if you are not confident to find credible info, we can provide you with some links. It is true that Googling may need you to many youtubers or online posters who don't really know the right answers to your questions, but they think they do and would therefore mislead to info that are not quite correct, or even totally false.

If I switch the computer volume to 100% then I guess the speakers will ask for more energy from the amp which will have not enough (50W < 100W) - hence it becomes underpowered.

Again, as explained earlier, that's not enough info, we would have to know the detailed specifications of your amp, is it an integrate amp that has volume control, or a power amp that has no power control? And, for example we would have to know the gain, or input sensitivity of your amp.

If my reasoning above is bad then the thing I don't understand is how the speakers know they have to ask for more energy from the amp? How do they know how much loud they should play?

The speakers doesn't know if they need more, obviously, you are the one who would know.

PS: I don't own an amp though I read a lot about them, enough to be more than able to setup and use it

That's fine, but you do have to at least tell us which amp you want to use as example so we can search for the information/specifications for the amp. Otherwise your questions cannot be answered properly, though we can throw you some very vague response based on some assumed use conditions and specifications of some amp and speakers, that, in my opinion, is not useful at all.

 

[adrhc]

My question presents just a hypothetical scenario based on which I want to understand/learn how an amp can become/run underpowered; just consider any amp with less power than necessary for some speakers which could run those speakers at low volume but would not have enough power to run them at high volume.

For example, this helps me:

The speakers doesn't know if they need more, obviously, you are the one who would know.

It means that the amp button one rotates to obtain more audio noise is intended to only allow the speakers to drain more power from the amp which would also mean more noise (higher audio volume). I guess that rotating/switching that button to max would mean that the amp is allowing the speakers to drain the whole power it can provide; but then how it's possible for the speakers to "ask" for more than the power made available for them by the amp?

Another thing that bothers me is whether the amp can get underpowered if I only change the volume to 100% from my computer (initially set to 10%) while not rotating/switching the amp volume/power button; does the volume change from the computer have any effect?

 

[Mikado463]

Oh boy, I'm really not sure where to begin with you ???

For starters, you need to freshen up on some basics..........

Peng, perhaps you can help out here ?

 

[adrhc]

Based on the above video I add these details (though it really shouldn't matter, it's just a hypothetical scenario ...):
amp has 50W max continuous output power
let's suppose not "dramatic" (average comparing to the market) THD
let's suppose is a class B amp
let's suppose the speakers are Revel Concerta2 M16

 

[adrhc]

But I still don't understand how the speakers could drain more power than an amp could give if the amp is only controlling how much power "flows" to the speakers (no more than the amp is capable of allowing to flow through itself) whilst the speakers can't "ask" for more.

If the speakers would be able to ask for some amount of power, more than an amp could provide, and hence would force the amp to still try to give more, then I would see in my mind an amp struggling and failing in various ways; but it seems the speakers can "ask" for more but they only can receive whatever the amp can provide hence why the amp would ever struggle to provide more? If I compare the amp with a pipe through which it "flows" electrical current then I imagine I can open the pipe 100% but if someone wants more to flow to that pipe it won't harm the pipe if it's not doing something about that, e.g. "push" aggressively toward him the "substance" flowing through the pipe.

It's clear that I miss something probably obviously but maybe the analogy helps you to help me.

 

[ski2xblack]

The pipe analogy is crude. You should investigate "gain staging" in the correct terms.

An amp may become underpowered if you turn the volume up (open the valve on the pipe) higher than the amp can deliver. That depends on speaker sensitivity and desired listening levels. If you want the hypothetical revel speakers to play at high spls, it may require more than 50w. Dynamics may demand considerably more than 50w. (This case warrants a more powerful amp, keeping the speaker's power limits in mind, or more sensitive speakers.)

Another way an amp could be "underpowered" is if the signal feeding it lacks sufficient voltage to drive the amp to full output. If the 50w amp requires 2v for rated output, and the upstream pre-out feeding it can only do 1v, the amp will never put out it's rated 50w. (In this case it's not the amp lacking but rather the pre-amp.)

 

[Cradan]

In your case, you have a 50W amplifier and 100W speakers. This doesn't necessarily mean the amplifier is underpowered. The 100W rating of the speakers is their maximum power handling capacity, not the power they require to operate. They can work with less power.

 

[Eppie]

Cradan is correct. The power rating on the speakers is not recommended power but maximum power the speakers can safely handle. Power requirement is a function of how loud you wish to listen at, the distance from the speakers and what the speaker efficiency rating is. Speakers with lower efficiency will require more power to reach the same volume level. There are SPL calculators on-line that allow you to estimate the required power to reach certain volume levels given the speaker efficiency and the listening distance. As long as the estimated power is below the speaker rating you are fine.

 

[MrBoat]

Wattage was just an indicator for loosely matching speakers to a power source for my use. Since I tend to historically choose double the amount of power I would ever need at my highest expected listening levels, I need to be cautious of not blowing lower rated speakers. I have speakers that are rated at 60 watts RMS per channel, but have them connected to a 120 watt RMS (into 8 Ohms) amplifier. I can tell by the sound of the speakers if I am pushing them too hard. With those, I don't push my luck and will not use them for loud listening.

OTOH, I have speakers rated at 175wpc RMS, hooked up to the same 120 watt amp. By the time I get to say, 50% volume, they are very loud. There is no danger of me hurting anything other than my hearing. I also have a pair of speakers that I connect to this same amp, that are rated at 500 WPC RMS, but have a sensitivity of 98db/2.83v/1m. 2-3 watts on those speakers will run normal people out of the house.

I know more about this technically than I use or even bother to think about anymore. It's just easier for me to stay away from lower rated speakers entirely for anything beyond ambient use. I don't like pushing things to near their limits, or with marketers optimizing efficiencies for me per their pre-conceived price points of trying to give me no more than exactly what I will use. The other gremlin in this is when trying to corner an exacting amount of power or speaker capability on a budget, which almost always means you are going to end up near higher limits across the board.

Best to buy speakers and amps twice (or more) as capable as you can ever use and just not have to worry about anything but your hearing health from there. You'll end up living very low in the distortion range, and low in stress on the amp as well, along with a good amount of future proofing. Every system I have ever put together along these lines, end up lasting for two or more decades and keep me from thinking about upgrades. Every system I have seen, where the user bought 'just' enough power, ended up either failing prematurely, or kicked to the curb once they got past the initial surprise of it just being louder than the last thing they had.

In other words, just go big, or go home. Save up enough $ for the overkill route. Buy the speakers that knock your (and the neighbor's) socks off. This pussyfooting around with trying to nail the most performance on a minimal budget causes more problems (and landfill fodder) than it's worth.

 

[ski2xblack]

I'll second Mr. Boat's rather practical "too much is just enough" and "use responsibly" approach.

 

[PENG]

But I still don't understand how the speakers could drain more power than an amp could give if the amp is only controlling how much power "flows" to the speakers (no more than the amp is capable of allowing to flow through itself) whilst the speakers can't "ask" for more.

On this point, you are more or less correct. As I mentioned before, you are the one who is in control, not the speaker. You control the output of the amp, and the amp drives the speakers, if the amp reaches it's output limit, it won't be able to deliver more current to the speaker. If the amp can deliver more current than the speaker can take, then the speaker will get damage eventually at some point.

So, if you turn the volume to 100%, the amp will be giving them the maximum they are capable of giving. Actually the amp may be delivery their maximum at lower volume, such as 80, 60, 50% or less, depending on the level of the input signal, and the gain of the amplifier. In other worlds, if the input signal is very strong, the amp could be driven to their limit at very low volume, such as 50% or much lower.

but it seems the speakers can "ask" for more but they only can receive whatever the amp can provide hence why the amp would ever struggle to provide more?

No, I will say this again, the speakers cannot "ask" for more, or anything, they are at the mercy of you, it is you who has to turn the volume control up and down to get the speakers to produce the level you like to hear.

As mentioned before, there are other factors to consider, and it can gets complicated quickly, but I assume you are not really looking to get too technical.

 

[lovinthehd]

You can buy an amp with less power than may be ideal for your speakers and your use, so to me an underpowered amp is just a buying decision.

 

[ski2xblack]

Another thing that bothers me is whether the amp can get underpowered if I only change the volume to 100% from my computer (initially set to 10%) while not rotating/switching the amp volume/power button; does the volume change from the computer have any effect?

It may not be terribly audible, but running the source output low and the amp volume high would inevitably suffer a worse S/N than if you turn up the source and use low volume settings on the amp.

 

[mono-bloc]

This thread is a complete waste of time

 

[adrhc]

An amp may become underpowered if you turn the volume up (open the valve on the pipe) higher than the amp can deliver.

@ski2xblack, it seems to me that you are close to my point of misunderstanding.
How can I turn up the apm's volume higher than it can deliver? It's as if I would try to forcibly enlarge the "pipe" to increase its maximum capacity; is this analogy correct? I assume the volume button also controls (directly or indirectly) the amount of energy that flows toward the speakers (aka, there's no separate button for the energy flow).

Another way an amp could be "underpowered" is if the signal feeding it lacks sufficient voltage ...

Let's ignore this possibility because the amp will be provided with the proper amount of energy (if this is about).
My setup will be (let's suppose the amp has the below ports):
- a computer connected with an optical cable to the optical amp's port
- TV connected with HDMI eArc cable to the HDMI eArc amp's port

speakers ... maximum power handling capacity

@Cradan, @Eppie, thanks guys, I feel like I understand this part (from other articles) but it doesn't enough help me.

Speakers with lower efficiency will require more power to reach the same volume level.

@Eppie, let's only suppose that some speakers (2x pair) need 100W for 97db while others need 150W to produce the same 97db. I set the amp to a particular volume level (e.g. 80%) then I test the speakers (in turn) and I expect to have one of these possible observations:

O1. the speakers played at the (approximatively) same noise level (i.e. db amount) whilst they used a very different amount of power; this means 2 things:
- the volume button is not like a pipe valve because, at the same opening level, distinct amounts of energy (aka, substance flowing through the pipe) flow through the pipe
- weird thing: the amp "knew" somehow to allow for more energy to flow through it even though the speakers don't convey to it this information (aka, they don't "ask", directly or indirectly, for the necessary amount of power/energy) - remember that the volume level was set at the same for both speakers

or O2. the speakers played at very distinct noise levels whilst they used the same amount of power; this means 2 things:
- the volume button is not controlling the volume but the amount of energy that flows through it (which also impacts the volume) hence is like a pipe valve
- weird thing: nothing wrong should happen to the amp or speakers if I open the valve at max (aka, amp's volume button at max) and the speakers are capable of handling more than pipe's max

I'm sure I miss something but I hope this scenario will help you help me .

PS: I read about gain staging at https://www.izotope.com/en/learn/gain-staging-what-it-is-and-how-to-do-it.html and I'm pretty sure I understand what is about though I still don't understand (a part of) the underpower issue

 

[cpp]

let's suppose the speakers are Revel Concerta2 M16

Have a read

Revel Concerta2 M16 Bookshelf Speaker Review

It's hard to stand out in a field of sub $1000 bookshelf speakers, but Revel has done just that with their Concerta2 M16 bookshelf speaker. So what is Revel bringing to the table? Read on to find out.

www.audioholics.com

 

[ski2xblack]

@ski2xblack, it seems to me that you are close to my point of misunderstanding.
How can I turn up the apm's volume higher than it can deliver?

Amps can deliver more than their rated power. The problem is that the distortion rises dramatically under such conditions, and *that's* what should be avoided. So a hypothetical 50w amp should be used if and only if you'll never exceed 50w at your most spirited listening levels.

 

[adrhc]

So a hypothetical 50w amp should be used if and only if you'll never exceed 50w at your most spirited listening levels.

@ski2xblack, how do I know what volume level corresponds to what power amount (+/- 3W error margin) for a certain speaker pair?