What does some "dead tones" in the low register indicate?

[sidenius]

I just borrowed my bands Melton Eb tuba to playtest up against another Eb tuba and my own B&S Cc tuba

The Melton plays fine except for the tones around concert G1 and A1 which are extremely "dead" (not resonating)
What does that indicate?
Could it be leaks or is it just a poor overall construction?

[pittbassdaddy]

Make sure that you are buzzing on pitch and the airstream is straight down the pipe. Try changing the blow to warm and wide. Try some slide pulling. Try playing in a different room. Try a different mouthpiece if you have one available. If none of that works, then start looking for mechanical issues with the instrument.

[windshieldbug]

too many possibilities to guess

[Donn]

The phenomenon may turn out to be less perceptible out in front, or even in the air vs. physical contact with the tuba. That doesn't make the tone center any easier, but it's something to look for.

I've never been sure what to think about the role of bracing in tuba acoustics, but some people who ought to know seem to think it's very important; I wonder how far a person could take experiments in this area, with hose clamps and stuff to see if any difference can be found?