Are people turned off your website by popups?
Pop up newsletter sign ups, the reason we don't recommend these is they are a barrier to the website visitor, who just wants to access information, products or services on your website.
If you want people to sign up, give them a reason to before hand, then have the sign up page or section in a convenient spot.
Having a separate sign up page, rather than a pop up, means you can post a link to it on social media posts and in emails. You are far less likely to turn people off your website (and inadvertently drive up your website bounce rate) and get more subscribers because you've already given them a reason to sign up!