When it comes to using closed-back headphones on an Akai GX625 reel-to-reel, there are several factors to keep in mind. The first is the impedance of your chosen headphones, as some models may require a higher impedance than what is provided by the GX625 to effectively drive them. Additionally, closed-back headphones will generally offer a better noise isolation and reduce background noise from the machine itself.
There are many great options available for all budgets and personal preferences when it comes to finding the right closed-back headphones for your reel-to-reel. Popular choices that provide excellent sound quality at an affordable price include the Beyerdynamic DT 770, Sennheiser HD280 Pro, and Audio Technica ATH-M50x. For those who have higher budgets and are after even more detailed sound quality, consider investing in premium models such as the Focal Elegia or Audeze LCD XC.