If you're shipping speakers, you'll want to know which freight class to use. Speakers generally fall into one of two categories: low density or high density. Low density items are less than 1 pound per cubic foot, while high density items are more than 1 pound per cubic foot.
The vast majority of speakers are low density items, which means they will fall into Classes 50-150. These classes represent the least expensive way to ship your goods. If your shipment is less than 150 pounds, you can use Class 50. If your shipment is between 151 and 300 pounds, you can use Class 100. And so on up the scale.
However, there are some types of speakers that are considered high density items. These include subwoofers and certain types of PA speakers. If you're shipping these types of speakers, you'll need to use a different class - most likely Classes 175 or higher.
When in doubt, it's always best to check with your shipping company to determine the best freight class for your particular shipment.