Single or pair?
First of all, it's a good idea to look at the price on the product page for the product in question. For the 1723 Surround S, it will say 1,599 USD/pair. The reason it shows as 1 in the cart, is because there is a difference between the left and right speakers. That means these have to be sold as pairs and cannot be sold as singles. This is the case for all our surround speakers and for the 1961 height speakers
The reason for the 1961 bookshelves showing as 1, is because these are packed as a pair in a single box. That means these cannot be sold as singles either. This is also the case for the 1961 Monitors.
The 1723 Towers - and all of our other speakers not mentioned above - can be sold as a single speaker, which is why it shows as 2 in the cart. A surefire way to tell if you've added too many or too few to your cart, is to compare the price on the product page to the "Subtotal" price in your cart.