Is it best to control the volume on my iPhone or on my speakers?

My friend and I have been having a long argument that I'm hoping a sound engineer might be able to solve.

When using a device with a simple auxillary output, e.g. IPhone or laptop, and speakers with built-in volume control - is it best to turn the volume all the way up on the device and then use the speakers' built-in volume control dial or the other way round?

Obviously I'm defining 'best' by sound quality. Thanks for your help guys, hopefully I can prove my buddy wrong!

Jimson xx

Turn your iPhone's volume up to the point of distortion, back it off until it no longer distorts, & leave it at that setting, then control the volume with the volume control on the speakers or amp.

= First, what ever audio file you have you should load it up on a audio editor and check to make sure the audio file it's self is not clipping.
= Second, it depends what volume control your messing with (you have to see if higher volume control on iphone/laptop causes distortion, = I would not have it all the way up, %20-%40 below distortion level is good enough). = What AVDADDY said.
= Third, then use the volume control on your speakers.

- If the volume goes over the clipping level, there will a lot of distortion. The closer those volume levels are closer to the clipping level (still below the clipping level), there's still very small levels of distortion. = I have some examples below.
= On my computer, the digital out volume control is greyed out at about %70-%80, they say if it was any higher there may be distortion. You can put the master volume on %100. You can then use the volume control on the speakers. = There may be a line or aux.ect volume control.
= On my computer, the recording volume is set all the way up and that is way to much distortion. You go to put it all the way down and then use the keyboard arrow keys and make it go up about 4 times (less than %10-%5 it's at). Even if it's to low, you can then use your audio editor and amply it below clipping levels.
= On my computer, you should test the volume for headphones and get just right. For live recording you can use the noise suppression effect (for background noise), or for regular (non-live) recording you can always use your audio editor and do a noise removal.ect

Always turn up the source device (iPhone) first, and then fine tune the volume with the external speakers. This gives you what is called "headroom".

Here is a quick way to explain why this is important:

It's your source device's (iPhone in this case) job to send a signal to the amplifier. In this case, the amplifier is built into your external speakers. If you were to turn the volume all the way down on your iPhone, it doesn't matter how far you turn the amplifier up, it will produce no sound, because the iPhone is literally sending the amplifier no audio signal. This would be a huge waste of amplifier energy. Why crank and amplifier and risk overheating it if there's no signal or little signal going to the amplifier to be boosted.

By turning up the volume on your source device, you increase the signal going to the amplifier, and in turn your amplifier doesn't have to work as hard to boost the sound.

I would like to point out however, that while it's not very common on devices like iPhones, cranking the volume up on a source component can lead to distortion (clipping). But in your case, you should be fine to turn it up all the way.