Current Questions


More and more, I see the word “current” in audio reviews. The reviewers warn me that I’ll “need lots of current” for a given speaker but they don’t explain exactly what it is I need or how many “lots” is. I’ve looked at a few “Electronics For Dummies”-type sites but I’m still confused. A few questions:

 

—What is current?

 

—When someone writes, “These speakers need a lot of current,” what do they mean? Is sensitivity involved? Impedance?

 

—On the amplifier end, what specification measures current?

 

—Are there subjective considerations at work in that spec? The number of watts doesn’t tell me everything about loud an amplifier sounds. Does the number of [whatever measures current] similarly leave things unexplained?

 

—Everyone asks, “How many watts?” No one asks, “How much current?” Is it really so important?

paul6001

Just as well the electron flow doesn't spill out of any unused wall sockets.

And yes, it is important. Otherwise amp could go "poof" when a few undersized power transistors are asked to handle too much power. First the amp would just sound nasty - that's a warning. Power is defined by current x voltage, that is, IV.

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. 

 When working with customers, one goal is to connect with them on the level that they are at and not just spew out your vast knowledge, using terms, definitions, laws, ad infinitum about the product or subject. What seems easy to understand with a background for reference in physics or electronics, is not where most people are at.

 In my case, don't even start with the basics of a tax form. Screw it, I give you the papers and pay you money for that. Explanation will often lead to even more confusion. 

Thank you everyone for trying to drag me into the light. 
 

Unfortunately it seems that the light isn’t so bright. The implication of Terry9’s post—take off the cover and look for this and that—is that there isn’t a spec I can look at and get quick understanding of a given amplifier’s current capabilities. No equivalent of watts as it relates to power. Is that right? Nothing that will give me even a rough idea? Something for fools like me who didn’t write a dissertation on Ohm’s law?
 

I could easily be wrong but it seems that, back in the 1980s and ‘90s, most every amp doubled in power as it moved from eight ohms to four. Like a manufacturer would be embarrassed if it didn’t. I think even my Harmon Karden 330c went from 20 watts to 40 as the impedance changed. (Dropped? Rose?) Is that just a warm, fuzzy feeling I’m getting from the past?

 

4krowme, we went to the same school of income tax preparation. I’d probably be better off if I stayed there for electronics. But I hate to be completely ignorant when talking to a salesman or reading glowing marketing materials. Knowledge is power and I don’t like being defenseless. 

When a speaker is determined to need a lot of current it means it is not efficient at converting amplifier power to sound level.  Therefore you will need greater power than a more efficient speaker would take. This involves both sensitivity and impedance. A speaker having a true 8 ohm impedance and is 90dB sensitive at 8 ohms requires far less current than one that  has 4 ohms impedance and is less sensitive. 

Best i can do at the moment.