802.11ac site survey needed if good signal at 802.11a?

[michael murphy]

I have a site that has good 5Ghtz (802.11a) coverage. heatmap so if we are upgrading our APs to 802.11ac , why would I need a specific 8021.ac survey? Does Airmagnet test other features of 802.11ac  and possibly alter my current AP placement and config? If so, what are those factors?

[Scott Fella]

Keep in mind that 802.11a extends further than 802.11ac and more than 802.11ax. So it really depends on if your current ap placements allow for 802.11ac coverage everywhere with some overlap.  What you do t want to happen is that clients only connect to 802.11n in areas because signal is not adequate for 802.11ac negotiation. This will also be something to consider when moving to 802.11ax. 
also when deciding to migrate, you want to remediate issue or concerns from your existing design. If users complain of poor experience in specific areas, then you might need to look at surveying that area and adding additional access point. 

[Tony Rosolek]

Keep in mind that your new and old APs probably use different antennas and might therefore provide different coverage. Which APs do you have today and which do you want to use in the future?

What signal strength does your current installation provide? -70dBm?