I just bought new speakers for my Mac. They are Harman/Kardon Soundsticks III, replacing my old Soundsticks II set, which connected with a USB cable. The new ones end with a plug that fits into only one place on my computer: the headphones port. They make a great sound, but I find it weird that they’re plugged into the headphones port. Is that usual these days?
I guess the unusual thing would be if the instructions do not say what kind of input the speakers connect to. Line-level outputs and headphone outputs are not the same.
ETA does USB even support audio signals? I would expect the USB cable to lead to an external DAC and preamplifier.
Well, there is USB Audio Accessory Mode, but I’m not sure how well it sounds. Perhaps the manufacturer felt the same way and therefore rolled it back to a good old 3.5 mm connector?
You can use a dongle to turn a USB port into a headphone output, assuming that’s what the speaker expects.
OK, I found the SOUNDSTICKS III Setup Guide online. It merely says, “Insert SoundSticks III input cable into the computer or other audio device.”
However, Amazon says “Thanks to its 3.5mm stereo audio connection, SoundSticks III speakers can be used with MP3 players, portable CD players, computers and almost anything with stereo line-level outputs.”
So it indeed needs to be plugged into a line-level output and not a headphone output.
There is little difference between a headphone output and a line level output if you are using it as a line level output. The difference is mostly down to output impedance, something you won’t care about here. (You need a low output impedance to be able supply current and thus deliver power, which is what you need to drive headphones. The voltages for headphones or line level are pretty much the same into no load.)
The first SoundSticks were a USB only device. I still have a pair. But Harmon decided that this was a bit limiting, and moved to line level input. There is a strange tension between USB and analog audio. Early portable devices, like the early iPods - although they had a USB connector were USB peripherals only - and it wasn’t until the introduction “USB on the go” that any device could be both host and peripheral. So iPods could not drive SoundSticks. For a wider market it made sense to move to analog output. Now we see Apple, and now others removing the headphone connector from phones. So you need a digital to analog converter.
Apple of course sell tine Lightning to audio adaptors. Less than $10 and it turns out they put some very expensive audiophool DACs to shame.
Why do you say this? The output of an MP3 player or portable CD player would be a headphone output, wouldn’t it?
That was a direct quote from the description on the Amazon store, and I have no idea why they wrote it that way.
You are absolutely right: I have a SanDisk MP3 player and a Sony portable CD player, and both of them have an output clearly labelled with the “headphones” icon, not the “line out” icon. The CD player has a separate optical output for hooking it up to other equipment, but that one is digital.
If @Francis_Vaughan says it doesn’t matter, I suppose I believe it, though if a line-level output is expecting a high-impedance load and you plug in a very low-impedance load, it seems like you are close to shorting it out and I am not sure why that would be in spec.
I read it as saying the speakers work with headphone outputs (mp3 player, portable CD players, computers etc) AND anything with a line-level output.
As it turns out, I’m thinking of returning the speakers anyway. The frequency response is weird; I have to keep adjusting the volume.
Glad I kept my old Soundsticks II set, even with the blown-out tweeter.
Usually a line level output, whilst it is expecting a high impedance load, is built with a pretty low impedance output. This is to make it as independent as reasonable of the load it sees. The output to input pair crate a potential divider, and the useful voltage that you see at the input is the result of this divider. Most line inputs are of the order of 10k Ohms. Headphone outputs can vary quite a bit, but are typically about one Ohm. You can see them vary from 0.1 to 10 ohms depending upon the designer and quality. Headphones vary a lot too, from about 300 Ohms, like most Sennheiser models, to tens of Ohms for the majority, and down to only a few Ohms for some weird exotica.
If you use 10Ohm headphones with a headphone output of ten Ohm output impedance, you will divide the available voltage in half. But use it on a headphone output of one Ohm and you get 91% of the voltage.
Drive a 10kOhm line level input from even a cruddy 10 Ohm headphone output and you see as close to 100% of the output voltage as you like.
Line level output in most things now is basically an op-amp with a build-out resistor. That resistor sets the output impedance. It is up to the individual designer what they want it to be. They will usually set its value so that a dead short on the output won’t harm the internal circuitry. Maybe 100 Ohms. It isn’t a massive leap away from what a headphone output looks like. Indeed most will drive higher impedance headphones without much difficulty. Perhaps not to ear damaging levels, but tolerably well.