What does "Sound Enhancer" do?

In playing with this and reading the many disparate opinions of what it does (apparently, Apple doesn't tell many facts about the effect) here is what I have found (I'm no audiophile, but I do have somewhat of an ear for things).

:: I hear a very distinct boost of of bass and treble.
:: I hear a distinct increase of reverb.
:: It sounds like those artificial "surround" features I've seen on boom boxes and bookshelf systems.
:: At the default (middle) setting, it makes the built-in speakers on my iMac (sitting in a cluttered computer hutch) sound a little better (so I left it on), but at the higher end, the effect is overbearing and hokey sounding.

My suggestion:
If you're looking for the "cleanest digital path" to your system, I would turn it off because, whatever exactly it's doing, it's adding some artificial effects to the signal. Besides, if it's not "enhancing" your listening experience, it's worthless to you.

I use an Apogee Duet also, and it alone provides the biggest improvement I've ever experienced in the sound coming from my Mac. I would leave Sound Check disabled, as it is certainly not intended for "audiophile" applications. It does some EQing to "enhance" the sound when playing tracks through built-in or cheap computer speakers.

^^EDIT^^

Of course by "Sound Check" I meant "Sound Enhancer."

This is a tangent from the main topic...

The Apogee Duet looks like a great device. I run a Mackie 16-channel mixer with the optional FireWire card to output it to an iMac for recording (it works fantastic for that and far exceeds my simple needs - all 16 channels available individually plus main mix on 17/18), but its ability to play back to the mixer is pathetic: it feeds at "full blast" with no gain or fader control on the mixer and no control from the computer at all (if you don't believe me, read the forums on the Mackie site) except the volume control of the application you are using (the first tick of the volume slider in iTunes puts the level about as high as you would want it); and it feeds in through the control-room section of the mixer with the "option" to feed it to the main mix (at full blast). The Apogee Duet looks like a far better device for outputting from the computer. I looked it up on one site and it was about $500. Is that pretty much the going rate for one of those?

After experimenting with, and listening closely to "Enhancer" quite a bit lately, I can safely say that it lowers the midrange as it adds reverb to it, and also compresses the rest of the audio even more than it has already been. To my ears, it takes a lot of the "punch" (dynamics) out of the music. For most applications, it is better to leave it unchecked. However, it is actually handy for late night listening, as you don't have to play with the volume knob as much during musically "loud" moments.
That being said, I found a sweet spot (a little to the right of the 'low' setting) that I've been using more and more, especially when I have company that wants to converse. It seems less intrusive, somehow.
To sum up, I think iTunes should just call it "Compressor" and perhaps avoid some of the confusion regarding it.
ASJ

Yeah, but "compressor" doesn't have sparkly marketing magic of "sound enhancer." 😉

Actually, they couldn't accurately call it just a compressor either because of the EQ and reverb (and possible other) effects. If they wanted to reduce the confusion (and the number of articles and forums on the web "theorizing" what it does), they could just tell us.

I am not sure but I do notice it seems to pump up the reverb for a faux surround sound effect, but personally I leave mine off, I have noticed I can adjust the sound much more effectively in ways I prefer with just the equalizer and raising the preamp levels of the EQ. To me iTunes has always sounded good regardless, and thus needs no "Sound Enhancer", my only beef with iTunes was that although sound clarity and quality was good, it sounded too hollow and faint, regardless of the volume, like how with a clock radio you can turn it up plenty loud, but even then the notes sound shallow and the beats paper-thin. That is no longer an issue once you set the EQ how you prefer and raise the preamp to just under the second highest bar. That is what works for me.

Wags wrote:
Now its a matter of deciding if I want to go thru the trouble of re-ripping my CDs into a lossless format. Wish iTunes would play FLAC.

You could quite painlessly convert your FLACs to Apple Lossless with Max. That's what I did. I now keep my music backed up as a FLAC archive on one hard drive, and as Apple Lossless on another.

The Duet's DAC is so detailed that it indeed makes a significant difference playing back lossless files.

I agree that there is a need to tailor the EQ for most songs in an iTunes collection. But it doesn't make sense to me to use the SAME EQ and/or pre-amp setting for ALL songs, because production and track volume vary so much.
Instead, I right-click on each song I want to alter, select Info/Options, and then assign that song a preset EQ and volume level that it remembers to use every time that song is played.
I've found this to be the best solution for arriving at a close-to "standard" volume and tonal balance for all my tunes.
Unfortunately, however, this is all only for playback. None of these changes to the tracks' sound properties are printed to disc when burning a CD.

In reading up on the FLAC format in Wikipedia, it says that a third-party firmware called Rockbox enables iPod to play FLAC. It lists specific iPod models: 1st-5.5th gen Classic (and some particulars on those), 1st & 2nd gen Mini, and 1st gen Nano.

The Wikipedia article also said that Windows (but no other platform) iTunes can play FLAC "after installing codec from Xiph (Ogg FLAC only)." I presume that means you can only play FLAC files that you converted using the Xiph software.

I would do some more research, but it appears that if someone has Windows iTunes, the right iPod, and Xiph, that you can use FLAC without creating additional formats of your music. But with our iMacs, we're outta luck on that one, Wags.

Rockbox has been around for quite awhile, and works quite well. I used it with my 5G iPod for the first few days I had it, and then iTunes 7 was released, which finally added gapless playback support, so I reverted to the Apple firmware. Rockbox is a great accomplishment, but battery life is atrocious when using it.

I haven't used the Xiph QT software for at least a couple of years, but it indeed used to work with OS X. It never seemed/seems to be up to date with all the changes to QuickTime and iTunes, though, so I don't think it's worth using when direct conversions from FLAC to Apple Lossless can be done on either a Mac or a PC.