Volume difference between radio and Sirius XM?

i don't know if that's the reason, but mine is the same way. also, big difference between cd, usb and radio.

 

Ditto on what bisco said, it's the same with my 2013 model three.

 

Much of the volume difference is due to MP3-like "compression" that's used on CD's and XM (digital) transmissions, but is NOT used on normal AM/FM transmissions.

 

XM audio is modulated a bit more than normal FM, due to many factors. thus the way the radio gets it, is the way it comes in. Kind of like commercials on Cable TV system, they are over modulated so they disrupt your sleeping. the amp in the head unit, amps up the signal it gets equally, so if it comes in at 3 it amps that 15 times, so 45, if it comes in at 5 it amps it to 75. thus louder.

 

I only recently noticed this problem (which I don't quite remember when I was first driving, strangely enough), but it seems like AM is mostly the really low volume one. I'll have to test this in a bit to be more sure..

 

Modulation refers to altering a signal (the content, e.g. voltage of the audio signal you're listening to) by mathematically combining it onto another signal (the carrier, e.g. a high-frequency signal that will sustain being transmitted over radio waves long enough distances for receivers to reliably receive that signal). The original content then gets "demodulated" off the known carrier.

This typically involves multiplying|convolving one signal onto the other. IIR, FM was found to be a better modulation method for maintaining the fidelity of audio frequency ranges commonly used in human singing and music.

Not sure the difference between AM and FM really have much to do with the difference in handling volume gain anymore. At least, this should be a long solved problem. My suspicion would be that any differences are due to something else, like just lack of proper engineering design.

 

So would the same things apply to explain the difference between the music played through my iPhone vs. the (plain old FM) radio? I checked to make sure the volume on the phone was set to maximum. When I used to play music through my phone on my old car, it was plugged in to the aux port, but the volume seemed consistent whether radio or phone. Now that I'm bluetoothing (and my first experience ever doing that), the music on my phone plays way lower than the radio. It's adequate and loud enough when turned up, but I did wonder why it was so much lower, and it is alarming to switch between them if I don't remember to turn down the car stereo first before switching back to the radio.

 

Ha, it kind of looks like it. I promise I'm not!

 

They'd added an intro signal processing course requirement by the time I went back to complete my EECS degree. For better or worse, I stuck with focusing all on CS so only ever learned the basic theory (math) behind signals. It has turned out to have unexpected benefits in for potential exploration of interdisciplinary pursuits: image processing, market analysis, information processing.

Music from our iPhones is typically .mp3, a digitally stored and compressed format that's decompressed on-the-fly and played back. AM/FM radio is still an analog transmission path, as far as I'm aware (there're actually places along the data path where it goes through both, but when we think of one as being "digital" vs "analog" it's in a critical portion where information loss is most likely to occur like in transmission|reconstruction.

My understanding though is that perceptible volume differences are issues of simply not accounting for automatic volume gain adjustments at a higher level of design, or, more likely in my mind, accounting for it, but it not being robust. An example of this latter would be if some manner of "resetting" the entire audio source appliance clears the problem up and this behavior occurs due to some unanticipated sequence of events we've happen to hit upon. I wonder how common this issue has been reported in the Audio forum..

 

I'm pretty sure I remember AM not suffering this when I drove it off the lot. I actually thought it was just the particular local Chinese AM station for my mom to listen to. Really gotta test the other AM stations now to confirm this (the current state, at least). For the record, CD and BTSA all work with volumes in the 20s. PiP base audio system here. Hmm.. really damn odd..

Yeah, it's got relevance to data|info storage as well. Compression techniques too. Shannon(-Nyquist-FamousGuy3-FamousGuy4) information theory all says stuff about what "information" is, what peak theoretical limits to how much they can be compressed is an' all. Also shows up in networking topics, comm of any sort, obviously..

 

Yeah, the Chinese station is a mix of talk and music (and also likely due to a combination of cost-cutting and music stations having more revenue from ads for FM bands--there're some local Latin stations also appearing on AM more). The bluetooth source audio seems pretty decent but I don't really carry music on my iPhone, an' haven't really looked into the EnTune app the car keeps goin' on about having.

 

Each source has it's own volume level memory. Not sure if you've noticed that. Probably not what you mean but thought I'd mention it. Indeed I have my XM volume level on 18 or so and my Bluetooth streaming/iPod source volume level on 25-30.