[jenkinsontherun]

Hi all,

This will be a thread dedicated to those wanting to learn the theory behind audio. Topics can range from materials, electricity, etc.

Andy

 

[Kentajalli]

-If I have a small electronic device with AC adaptor @ 12V and 3A, why wouldn't the wattmeter at the wall say 36W (since 12V x 3A)
That is the max rating of the adaptor, meaning it can output a max. of 3Amps at 12V - you connect it to a small device and it may draw 0.1A .

-Not related to the first question, but why is watt not as simple as VxA. I heard this somewhere, and it clearly goes against the basic science equation P=VxA
It pretty much is that, if you can measure the voltage drop and the current correctly.

-what makes an amp work (bit by bit, not explained all at once of course)
An amplifier takes power from the socket, cleans it, gets it ready for use. It uses the signal input, say from your CD, which is tiny, as instructions to output the ready-power it has on tap from the wall socket to the speakers! if the CD signal goes up, the amp funnels more power to the speakers, if the CD signal goes down, the amp funnels less - so it just takes instructions from the input to vary its output - so remember, at all times, you are listening to the powersupply section of your amp.

-why does a headphone diaphragm vibrate (what does "driving a headphone" mean)
the diaphram has a motor built into it that responds to the power coming in from the amp, so the amp is doing the driving.

-why do speakers play louder when I turn up the volume knob
The volume knob controls how much input signal goes into the poweramp, the more you turn it the more the poweramp shoves power into the speakers, the more the diaphrams move.

Welcome - no charge!




Thank you very much!
Andy

 

[SilverEars]

VA is actually just multiple of VA at an instance like KVA for AC. But, watts is power in RMS for AC or DC for constant supply.

 

[jshaevitz]

Physics professor here. Happy to answer questions via email.

 

[jenkinsontherun]

Thanks for the large support you guys. @SilverEars Yes! this was the point I was pinpointing at. Does it have to do with something of consumption vs demand?

@jshaevitz A professor was the last person I'd expect responding to this thread! I'll send you an email soon, thanks for offering to help.

@Kentajalli Would it be appropriate, based on your answer, to call a voicecoil/magnet combo a motor?

 

[Kentajalli]

@SilverEars Yes! this was the point I was pinpointing at. Does it have to do with something of consumption vs demand?
technically, it is consumption + wasted energy that the wattmeter would read. so if the equipment consumes less, the meter reads less. for safety in this case it should not go beyond the 3A rating.

@Kentajalli Would it be appropriate, based on your answer, to call a voicecoil/magnet combo a motor?
Absolutely! what is a motor? a device that converts electrical energy into mechanaical energy - doesn't have to be rotational.

 

[jenkinsontherun]

@SilverEars Yes! this was the point I was pinpointing at. Does it have to do with something of consumption vs demand?
technically, it is consumption + wasted energy that the wattmeter would read. so if the equipment consumes less, the meter reads less. for safety in this case it should not go beyond the 3A rating.

@Kentajalli Would it be appropriate, based on your answer, to call a voicecoil/magnet combo a motor?
Absolutely! what is a motor? a device that turns electrical energy into mechanaical energy - doesn't have to be rotational.

Cheers

 

[Ryokan]

Probably easily answered by some:

Why is a group of 100 people shouting much louder than 1 (if the one person has a loud voice and the others don't individually shout louder)?

 

[jenkinsontherun]

Probably easily answered by some:

Why is a group of 100 people shouting much louder than 1 (if the one person has a loud voice and the others don't individually shout louder)?

Interesting question, I believe this is related to the fact that two speakers won't be perceived to be twice as loud as one?

 

[SilverEars]

Probably easily answered by some:

Why is a group of 100 people shouting much louder than 1 (if the one person has a loud voice and the others don't individually shout louder)?

I think the sound waves from multiple people if overlapped causes constructive interference, thus amplifying the sound.

https://techblog.ctgclean.com/2011/10/ultrasonics-sound-interactions-of-sound-waves/

 

[jenkinsontherun]

Upped to $40USD/month. I did some quick math and it turns to around 1-2 hours, as I don't expect to ask you questions every day.

If you are unsure, please send me a msg. I don't need a 1000% expert on the subject, just someone who knows enough to explain it in technical terms, and able to answer follow-ups on those technicalities, so just beyond the surface understanding level.

 

[jenkinsontherun]

Bump

 

[jenkinsontherun]

bump

 

[miketlse]

-Not related to the first question, but why is watt not as simple as VxA. I heard this somewhere, and it clearly goes against the basic science equation P=VxA
It pretty much is that, if you can measure the voltage drop and the current correctly.

If you are talking AC, you have to include the power factor as well, because inductance in the load can cause the voltage and current to be out of phase.
This is a big consideration for firms which have a lot of motors connected to their power circuits.
Also a factor if you are driving headphones or speakers, which represent inductive loads.

 

[jenkinsontherun]

If you are talking AC, you have to include the power factor as well, because inductance in the load can cause the voltage and current to be out of phase.
This is a big consideration for firms which have a lot of motors connected to their power circuits.
Also a factor if you are driving headphones or speakers, which represent inductive loads.

https://www.electronics-notes.com/articles/basic_concepts/inductance/inductance-basics-tutorial.php

Found a decent article but didn't read in-depth yet.