Current Questions

I believe Krell was first to go for broke in this area. How does this all apply in the world of class D?  Maybe it was Bob Carver whose cube amp broke this open by generating high current capacity without big storage?  

In the chicken versus egg sense, it was the hard to drive speakers, which then became a problem to solve with amps that had the current to drive super difficult s loads.

I’ll quote myself 😎 from post #2:

Which is why those impedance plots are worth a look when considering speakers.

Before I continue, let me say that holmz gets it, i.e. in reference to my post. No BS, no put down or what is too commonly seen on this site, so thanks for that.

I’ll work on being more “common” and lace in put downs and humiliations 😁

(On a serious note, thanks man.)

It is easy to assume that others have the equivilent of a H.S. Electronics shop class or HS physics, but it is apparent that this is not a universal truth.

On the sales side, there is push for saving parts costs and manufacturing costs. And hiding factual performance in specs that make it hard to get to what exactly a piece of gear provides.
That makes it very hard to not be sold garbage or gear that is marginally appropriate.

On the subjective side:

Speaking of twenty, that's Bryston's guarantee. They build their stuff to last, and last it does. Not a shill, just a satisfied customer

^This^ person, and others I have know, speak very highly about the Bryson gear. I do not know much about their gear, except that a lot of people that I respect (and who are use similar speakers) use Bryson.

So if one is disinclined towards understanding the inner workings, then finding what others are using successfully with similar speakers (in terms of amplifiers) is a good strategy… assuming that success often repeats itself. 

A for amps. Amp for Ampere

falconquest,

 After skimming through these many posts about a simple question, your answer has the best potential to answer the basic question asked by someone admits right up front that this isn't exactly his line of expertise. Thanks for that. The fact that some of the posts accurately describe current with the inclusion of OHMS law, or other related truth, does not help the person who is asking in the first place. 

If only thing should be understood here, it is that the speaker’s impedance is what determines whether a particular amp is gong to work or not work.

The equation (V=IR) itself, defines a relationship between resistance and current.

So we need to understand either the I, the current, (which relates to the amplifier) or we need to understand the R (which relates to the speaker).

Which means that:

we either start with amp, and determine what speakers are not going to work, and look at the rest that will.

or

we start with the speaker, and determine which amplifiers will work and which will not, and then go from there.

We can talk about current in isolation, but it seems easier if we started with an example of what speakers you wanted to consider running.

Not to get too technical but in terms of current, since the speaker is a "load" can we not say that the speaker will have a certain current "draw" in order to reproduce the signal being sent?

At a specific voltage and frequency, then yes. The draw is linear with voltage in the equation V=IR or I=V/R.

If the amp does not have the capability of providing that draw, is that what leads to the amp clipping?

There is clipping as in trying to reach a voltage that is too high to achieve as it is beyond the rails.

And there is inability to provide the current. When the current cannot be provided, then the desired voltage will not be achieved. This would be more of a distortion than clipping. (Almost like compression).

In other words, the question isn't so much amp output current but, as some have been saying, the amount of current draw by the speaker. One must understand that and choose an amp that will meet that requirement.

If the speakers draw less, or equal, to what the amp can provide, then all is well.

I have never seen specs. for either but I have experienced it.

The specs for impedance is common for most decent speakers, and maybe half of the speakers show it.

When I look at a toroidal power supply I see a big thing that holds a lot of juice. 

What you should see is a transformer that keeps the magnetic filed inside.

It holds no juices.

I understand the "I" for current and its origin.  Why do all or most electrical items use the letter "A"  example:  1.2A

It is same as referring to resistance as a thing, and the quantity of the resistance in ohms.

Similarly “speed” can be given in Mach number, MPH or KPH, or percentage of the speed of light… etc.

Take a typical amplifier with a set of 28V rails,

V = I R

So I =V/R

A speaker with an 8-ohm impedance would need a maximum of 3-1/2 Amps
A speaker with a 1 ohm impedance would need 28A 
4-ohm = 7A
2-Ohm  = 14A

Which is why those impedance plots are worth a look when considering speakers.

The impedance phase is important too, but beyond the scope of the question… But it gives you something to look forwards to. 😉

 

Yo Holmz, I appreciate the effort but you lost me in the first line. Rails? Volts? In the the equation V = I R, I assume that V is volts but what is the other stuff?

V = Volts

I = Amps

R = Resistance

Still, there may be some gold in the stream. Is current measured in amps? And since low impedance speakers are harder to drIve, does that mean that they require more current, i.e., more amps. Am I right so far?

Yeah

Where does volts fit into the picture?

Speakers are voltage devices, and most amplifiers are.

So when someone says that a particular speaker needs a lot of current, he could just as easily say that a speaker is low impedance and needs a lot of amps. Does that make sense?

yeah mon. exact.

But I’m left with a big question. If it’s true that current is measured in amps, what is being measured? Some kind of energy? What kind of work does this energy do in a stereo system?

This is all what used to be high school physics.

The speaker need to push the air to make sound waves, so it needs force not energy. If that force need to move, and do it a lot, then that called power… Just like engine force in a car is called acceleration, and is from torque. And speed is from power. One is instantaneous and the other happens through time.

The current it what is making the force in a piston speaker with a voiced coil.
But some of the big flat panel speakers are doing the pushing using voltage to make the force. And other big panels use current.

I think maybe the education system is not what it i once was, but a community college 101 course or a private tutor for an hour would pay off.

Best might be to just ignore the physics and enjoy the music.