How to calculate freight class for speaker shippin

I'm thinking of selling some speakers and I'm trying to determine how to determine the freight class. I found some online calculators that give me a freight class of around 75.

Here are the calculations:
Two Vienna Acoustic Beethoven cartons side by side on a pallet.
48 x 30 x 14 (with pallet thickness)
I estimate a weight of 135 plus 40 for the pallet = 175 lb
The online calculators all say about 70 to 80 freight class.

But I'm still confused about the freight class. Does the estimated value of the freight increase the weight factor? If I insure it at $2000.00 does that increase the weight class beyond 70?
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Used home audio speakers are freight class 100 if I recall properly. The problem I encountered when looking at shipping my speakers freight was that the companies would only insure for 10 cents per pound since the speakers were used. So they'll insure your 175 lb cargo for $17.50.

FedEx has a freight service, but they were more expensive than FedEx Ground. I ended up shipping my speakers (150 lbs each packaged) via FedEx Ground from Mobile, AL to San Diego. They arrived undamaged, but I had the original boxes and packaging material. I also beefed up the packages with some plywood inserts as well.

You could always look into taking the speakers to a FedEx Office location and let them package the speakers. It might be pricey, but they're totally on the hook for any damages since they packaged them. Just a thought.
Try the eBay uShip service, and make the buyer do a pick up via his using that service. The insurance issue still exists. I was recently quoted blanket service for two speakers weighting about a total of 100 pounds for a 850 mile trip for $225, including the uShip fee.
Freight class 150. I still have the bill of lading from FreightCenter. Shipped Gershman Acoustic Sonograms a few months back.
My speakers were 48 x 40 x 30 and weighed 215 lbs. They use cubic space to figure things. The cost was figured using the size of a standard pallet. When they came to pick them up, the truck wouldn't fit down my road, too many low branches, so I had to put the boxes in my Nissan and drive them about a quarter mile to the corner and slide them onto the truck.
As far as insuring them, I got info from FreightCenter for an insurer as I set things up. I used Inland insurance, and it wasn't very expensive to insure for 2 grand. The shipper was R&L Carriers, who took them to one of their facilities where the buyer wanted to pick them up. Check out FreightCenter. You can find everything you need. Can even fill out the forms to see if you're satisfied before you commit. I was pleased with them.
Sorry for all of the separate posts, but this comes to me after I think back...
When I got things rolling with FreightCenter, they contacted me to make sure things were right. Once you're happy with how things look, then you can commit. They called multiple times, sent emails to let me know how things were progressing. They are right on top of things and very thorough.
Speakers are class 100, you can insure them for what ever you want, within reason, and you pay a premium for that insurance. Make they are securely packaged on a pallet that fit the boxes, and put a piece of sheet good on top, OSB for an example. Strap the whole thing securely to the pallet and shrink warp after that.

We use Saturn Freight they most likely have a branch in you locale look them up at Satutn Freight Systems Contact your local branch and they will quote you. Residential delivery, Lift gate, (required for shipments over 150 lbs) are extra too, from memory $ 50 for each, so guesstimate for your shipment in the neighbor hood of $ 350 - $400

Best of luck