HK now works with ART
FYI: scrosler, the dev for CleanROM, just re-worked the HK mod, made it ART compatible. In v2 he also used the latest Sprint source which greatly improved the bass on HK - IMO.
You can find his mod here: http://www.scottsroms.com/showthread.php?t=5210
I cant post in the Dev forums yet (in the HK mod thread) but wanted to give some tips based on my experiments with testing HK and Boom on the M8 thee past couple days.
Now I dont claim to be an audio expert or anything and didnt get into mobile audio till voodoo sound on the Galaxy S so take my advice as you will.
Impressions of each before I give my tips.
Boom- Good Highs and Lows with leaving the mid lacking some, still ok but If not careful with EQ settings and such you can end up with really blown out bass.
HK - Gives good mids, the bass isnt as good and puts a little more treble in the loud speak than I'd like but nothing too bad (essentially the opposite problem boom has tbh) Highs and Lows can be kind of flat with HK.
Now for my tips if you want to test it and how I set PowerAmp
Before Switching and after Test with these settings
1. In poweramp you need to disable Direct Volume Control
2. Adjust Audio buffer size to +500ms and Thread Priority to +3 (some have reported issues with laggy audio and Poweramp sometimes and this should help)
3.(Optional) I enabled replay gain with the setting of ApplyGain/Prevent Clipping according to Peak with track as source
4.Set your EQ as you like but also test both a Flat EQ.
5. Test on Speakers and Headphones not just one of them.
Now after doing this I noticed that if I used my favored bass/treble EQ with Boom, the bass would get blown way out and essentially overpower everything else turning it to a muddy mess. So then I tried using the mids EQ to boost thee mids a bit with Boom but it just didnt sound right IMO. If I just went with the default Flat EQ I was fine, got good bass and treble but like was said the mids felt lacking. I would say if you continue using Boom I would go with a flat EQ as Boom has the Bass and Treble pretty well taken care of and does really well on the speakers.
Now I've switched to HK, and My first tip with HK is you probably shouldnt use LiveStage as It isnt that great. In testing it seems to be similar to the Environment option in many Audio Driver settings and really doesnt do much for the audio IMO. If you like it thats fine I just dont find it to add much and detracts more than anything. Clari-Fi is a mixed bag, if you have a library full of low to med quality MP3s I would say enable it because it does seem to help some with those. If you have mostly 320kbps MP3 or higher audio then it isnt going to do anything for you and you can disable it. Now with poweramp I used my standard Bass/Treble EQ and It sounds great :] no blown out bass and I also get the advantage of better mids which Boom didnt have. Bass is still a bit less than Boom but with my EQ it helps on the weakness that HK has on the Highs and Lows.
IMO, HK is better over all for me with my Poweramp setup on headphones, but for the built in speakers Boom is definitely better than HK. I leave it to you guys to judge and if there is anyone with more audio experience that has any tips, tricks, etc. feel free to leave it here and I'll add it to the OP. The best thing you can do is test each, dont let me or anyone tell you which is better because it will be subjective.
EDIT: Decided to add some tips for those wanting to get the most out of their headphones. This mostly applies to the over the ear types as i dont normally use the in ear ones. These also dont apply to every pair, my O'Neills greatly benefited from the added holes in the housing (improved the slightly weak bass) some HPs wont and also depends on how open or closed you want them. Do research on the model you have before modding it.
Things you can do to improve your HP audio
1. Many over the ear phones dont give the driver room to breath, they have 1-2 or no holes at all and so not much air gets in. what i did is grab my Phillips O'Neills and a drill with a small bit and added another 10 holes to each housing. (pic below)
2. If there is any fabric covering the inside either (pic below)
a. if its not like my O'Neills with the nice cushions cut a quarter sized hole into the padding so you still have some to go on your ears
b. If it has cushion like mine remove it entirely
the fabric can have a sort of muting effect on the audio which we dont want
3. Open them up (carefully) and look at the back of the driver (speaker) and there should be a paper filter there with some holes (its covering them). Poke holes into the paper filter to let more air in. this increases bass)
4. While they are open if you have some felt to line the housing then do so as well as put a circle of it on the back of the magnet, this will dampen back wave.
Also I figured I would recommend some headphones if you guys are looking for some good HP under 100$
Koss PortaPro (40-50$)
Creative Aurvana Live (50-100$)
Grados SR60i (50-100$)
Koss DJ100 (40-80$)
In Ear Ones
Audio Technica CKM500 (30-70$)
SoundMAGIC E10 (20-40$)
HIFIMAN - RE-400 (100$)
VSonic VSD1 (40-60$)
I know I dont use any of those though, I have Phillips O'Neill Stretch HPs the are crazy comfortable but arent top in their range. Im working on modding mine but most of the listed ones dont NEED it but if you like to tinker the O'Neills are crazy comfy