Bowers & WilkinsPi7 S2

How we test sound quality

We rate sound quality using a professional panel of five expert listeners with a range of ages and musical tastes. They listen to nine recordings for each pair of headphones, which cover a wide range of music and radio genres, giving a rating per recording and an overall verdict (not an average).

How we test features

Our lab professionals assess a range of factors, including whether there are different sized ear pads or buds provided, the ability to make and receive phone calls and whether cable controls are present.

How we test external noise cancelling

Our expert listening panel and lab professionals assess how well the headphones cancel out noise from your surroundings, such as aircraft and railway noise. To do this, they use recordings including one of the London Underground, both on trains and on the platform. The assessment is done in two ways: a consensus rating from the five member listening panel, and a 'lab conditions' rating using a synthetic ear. Rating only applicable for active noise cancelling headphones.

How we test acoustic seal to your surroundings

Our expert listening panel and lab professionals assess how well the headphones prevent sound leaking out to their surroundings. This is done in two ways: firstly, we ask our five member expert listening panel to note how much sound they can hear while the headphones are playing next to them. Second, we measure the sound leakage objectively using an external microphone. It's particularly important to choose headphones with a good acoustic seal for travelling, to avoid annoying your fellow passengers.

How we test comfort

Each of the five members of our professional listening panel, who have a range of ages and ear sizes, gives a rating for how comfortable they find the headphones to wear, and we take an average.

How we test durability

Our lab professionals assess for how well built the headphones are. For wired pairs, the focus is on the strength of the joint between the headphones and the cable, as this is where many cheaper wired headphones fail. For wireless pairs, the focus is on the strength of any moveable joints. We made our durability test for wireless headphones more rigorous from May 2018, so the star ratings for wireless headphones from then onwards aren't comparable to wireless headphones tested before.

How we test battery life

We play music continuously at a reasonable volume until the battery runs out. A five star rating is 2020 minutes or more, and similarly 1540 minutes for four stars, 1060 minutes for three stars and 580 minutes for two stars. Anything less gets the minimum one star rating. For truly wireless headphones, it is the battery life of the earbuds only, excluding recharges from charging cases - this means that even the best truly wireless headphones tend to get a mediocre score here, as the per-charge battery life is low compared to other types of headphones. Since truly wireless headphones are convenient, battery life doesn't affect our overall score for a pair of headphones (although anything particularly bad we'd make a Don't Buy).