In some cases the performance of Apple computers Bluetooth connection can affect the audio quality when used with Bluetooth headphones (like the Momentum Wireless, MM 450-X, MM 550-X, etc.)
Below you will find details on why this happens and some possible ways to overcome the issue.
For the best connection we recommend using a Sennheiser Bluetooth dongle.
BTD 800 USB bluetooth dongle
When connecting Bluetooth headphones to your device it is important that they are connected using the correct bluetooth profile.
The two profiles most commonly used for audio devices are the HSP (or HFP) and A2DP.
Headset Profile (or Hands Free Profile)
HSP (or HFP) is for connecting a headset for communication, like softphone calls. This allows for a signal from the headset microphone to the computer and a signal from the computer to the headphone.
The quality of audio is limited due to a narrow bandwidth, put is perfectly acceptable for voices.
However, if you try listening to music in this profile, you will find the audio is poor quality and the music can sound tinny or distorted.
Advanced Audio Distribution Profile
A2DP is for connecting a headphone for listening to music.
This allows the computer to send high quality stereo audio to the headphones. There is no microphone signal in use.
This audio quality is much better and should be used for listening to music.
The audio codec is the way in which the digital audio data is compressed, before being transmitted to the headphones. As standard, most A2DP enabled devices use the SBC codec. Most Sennheiser bluetooth headphones are also enabled with the APT-x codec, which is generally regarded as giving a higher quality audio transmission.
Your host device (PC, phone, etc.) must also support APT-x otherwise the headphone will revert to SBC.
Connecting to a Mac
When connecting your bluetooth headphones to a Mac, you should check that the connection has been made in the correct profile for the task at hand.
If you are using it as a headset to take calls, the HFP profile should be selected (along with the SCO codec).
If you are listening to music, then the A2DP profile (along with the APT-x codec) is the preferred option.
You will hear music being played whatever profile is selected, but the audio quality of music will be very poor in HFP profile.
Try pairing the headphones and playing some music.
Whilst the music is playing, to check which Codec is selected, hold the option key ("alt") and click on the bluetooth icon in the menu bar. When you hover your mouse cursor over the bluetooth device it will display the Active Codec. So long as this shows 'APT-x' you are good to go..!
If it is displaying SCO then it is still in HFP headset profile. In this case at the bottom of the menu, click on Open Sound Preferences. Click the output tab and double click on the Sennheiser device (e.g. Momentum M2 AEBT). You will likely hear an announcement in the headphones saying 'call ended' and then the music quality will improve greatly as you switch to A2DP profile.
A2DP profile Codec's
If you are in A2DP mode, but you cannot get the codec to switch from SBC to APT-x, you may find that the audio quality is pretty poor still.
This is because the Mac will default to a really low bit-rate on the SBC profile and then slowly work it's way up to a better bit-rate depending on what else is happening on Bluetooth..
The APT-x codec has a fixed 354kb/s bit-rate, but the SBC profile can be much lower, effectively limiting the amount of data that can be trasnmitted. This can manifest itself in audio glitches, drop-outs or distortion.
To make changes to the bit rate, or to force the codec to APT-x, is a little more tricky..
You will need to download the Bluetooth Explorer app ***. This comes as part of the Hardware IO tools for XCode package from the site: https://developer.apple.com/downloads/
Once you have downloaded this, open Bluetooth explorer and select Audio Options from the Tools menu.. Here you have a couple of useful options..
If you want to use APT-x, just select the 'Force use of APT-x' checkbox... You will have to disconnect and reconnect the bluetooth connection before this will take effect.. Once you have done this, check again and you should find you now have the APT-x codec in use and audio quality should be good.
Alternatively, you can control the bit-rate of the SBC codec. It is likely that the 'minimum bitpool' setting is pretty low... increasing this to around 35 is likely to improve the audio quality considerably.
*** note - Bluetooth Explorer is an Apple developer tool.. It should be used with caution as using features incorrectly may harm your device. We have suggested use only of the Bluetooth Audio Options feature and do not endorse use of any other features. If you don't know what you are doing, we suggest you leave it well alone..!!