The bluetooth range is very good. Testing connection with my iPhone8, in my semi open ground floor, the slim+ reaches from one corner of the floor to the other, reaching about 40+ feet with no disconnect. Heading upstairs, the connection stayed until I was another 30+ feet away on a different floor. Note that when paired with my 2017 Retina MacBook Pro, the range is less but that’s more a problem with the MacBook Pro’s bluetooth.
One negative about the bluetooth implementation with the Slim+ is that it does not support multi-point. You have to manually (re)connect each device to the Slim+ if you use it with multiple devices. I switch between my iPhone 8, and my iPad Pro. Note that you do NOT have to re pair the devices, just reconnect. Other, usually more expensive headphones, support multi-point and will remember the last two devices and stay connected to them and switch between them as needed without manual intervention.
Battery and Charging
The battery, together with three buttons, one indicator light and the mic, is in the single control “block” on the right side of the cable. It is light enough that it is not pulling the earpiece out of my right ear, even during a jogging test. The charging port is covered with a flexible rubber piece that is not difficult to open because it has a tiny lip. This is good design because there is nothing more annoying then trying and fail to pry open the charging port.
When battery is running low, the slim+ will give an audio signal as well as black the LED red. I did two run down test and both times the battery lasted for just over 6 hours playing music constantly. The charge time from empty to full is just under 2 hours. During charging, the LCD stays steady red until charged. The LED then turned solid blue.
First, the slim+ now supports AptX. I tested it with my MacBook Pro. The codec showed AptX in the bluetooth display. This should provide better playback audio quality. But note that iPhones do not support AptX. For me, this is only useful when I listen to music on my MacBook Pro.
For my sound quality test, I test them with my iPhone8, as that is the most common usage scenario for me. In general I found that I need to burn the headphones in a bit before it started to sound good. After my first two fully charged and discharge test cycle, the Slim+ has accumulated over 12 hours of play and the sound definitely opened up a lot.
The seal of the earbuds affect the sound quality a lot as well. So make sure you pick the right size earbud and have the earbuds seated in your ear, making a good seal. These are the tracks I used to test the sound quality:
Wasted by Brandi Carlile: This track has a steady bass drum and piano chords background throughout. I find the bass responses good without over powering. I almost wish it is more boosted, as with many headphones, to give it more of an unnatural punch for fun, at least for this track. Her raspy vocal sounds clear and warm. Sound stage is good.
Viva La Vida by Coldplay: This is another fun and complex track. With the recording, Chris Martin’s voice is somewhat muffled by all the instruments. The Slim+ managed to surface his voice enough. It may not be as good as the Klipsch X11, but that costs ten times more.
Exit Music (For a Film) by Brad Mehldau: Switching to Jazz, this track pushes any headphones to render the various instruments clearly. For the Slim+ the cymbal attacks are reasonably good. The very deep double base keeps up except for the very low notes. I find that the Slim+ does not boost its treble and bass like many headphones. I prefer this more natural response, especially for Jazz and vocal pieces. I think this track shows off the Slim+ the most — showing what a $30 or so headphone can do.
Fit and Comfort
The Slim+ comes with four set of tips. The medium one that comes fitted works fine for me. I don’t really need the wings to keep the earbuds in my ear. I did a bit of jogging with them and they stay in fine. The cable is not the flat tangle free type, but I don’t find it posing any problem. The entire unit is light enough. The earbuds are made of a nice soft rubber material that put little pressure, and I can comfortable wear it for an hour at a time.
Does the Slim+ sounds better than the Klipsch X11i? No. Is it more convenient than the BeatX in connection management? No. But remember, this is a pair of sub $30 headphones that sounds almost as good as something that is ten times the price. For day to day use, the sound is natural, the earbuds are comfortable, bluetooth range is extremely good when paired with the iPhone. Battery life is good. I recommend it.