Can someone explain this wattage and cab situation to me

[Geo]

No, it sounds like a 30 watt speaker, because according to the manufacturer's rating ( whether conservative or not) it is. A conservative rms rating to avoid excessive warranty work is a pretty sound idea for a speaker manufacturer. Especially on a speaker you plan on selling a very large number of as OEM to various amp builders. Now why manufacturers would then try to screw that up by placing the speakers in amps rated twice that amount is beyond me.

I have the head version of this amp. When I checked bias, it was really low. I forgot the numbers but I remember thinking there is no way this head is putting out 50 watts. And quite honestly how many people would be able to tell by volume and sound the difference between 30 and 50 watts? And on top of that, how many people use it full tilt?

IMO opinion though, I would say sound wise, the speaker is very well matched to the amp.

 

[Kagami]

My understanding if the speaker impedance is higher (e.g., 16 ohms) , it will put more load on the tube amp output (e.g., 8 ohms), reducing the amps output to, and the volume from, the speaker.


edit: and if it's a solid state amp they usually don't have an output transformer, and 8 ohm amp into a 16 ohm speaker could potentially damage output transistors at high volumes.

OTL solid state amps will generally have a minimum impedance listed, running a higher impedance won't hurt it reduces power output. Regarding output transformer mismatch impact there's a thread here talking about it: https://www.rig-talk.com/forum/threads/impedance-mismatch-and-its-effect-on-sound-tube-amps.326054/ but it doesn't really impact the output power rating.

I don't think it is related but... Celestion told me speakers can handle twice what they are rated. But they won't last very long.

I try to use at least double what the amp is rated. I have blown several speakers over the decades.

Speakers are usually heat limited by the voice coil which is why high power woofers have a lot of ventilation in their magnet structure so they can keep it cool and work safely at high power. As long as it's not consistent speakers can handle a lot more peak power than rated for consistent output.