When it comes to the sound of your new cello, the qualities that will keep your relationship with it healthy are a big bass, good projection, and ease of playing (speed of response). Nearly everything else can be adjusted quite easily.
Oh! Have I seen so many great cellos rejected because the player didn’t like the string height or the cello was “too bright”. String height can be adjusted down in 20 minutes by a luthier. A different string choice or bridge could darken the cello tone adequately (thought I believe most of the time cellists are making their audiences suffer because their cellos are set up too dark).
But it is so very hard to make a cello with a deep, powerful bass! (K. Michael Krentz instruments all make epic bass.) Most student instruments are quite un-resonant. When a possible better new instrument is auditioned, the added bass, though still relatively weak, is exciting, but only for a little while. Ask the shop owner to let you play the instrument with the best low register in the shop. There is no guarantee that it is actually a great low end, but at least you’ll be better off than comparing it to your present instrument.
When it comes to bass, the deeper the better. Beware instruments that are simply loud in the bass but lack depth. Like a teenage boy singing bass versus a grown man. Owners of instruments like this usually get frustrated with a lack of warmth over time. There is no adjustment to get it later.
It is possible to find instruments with deep basses that lack enough power or pizzazz in the upper registers, so do be sure to check.
If an instrument is slow to respond, it might be made quicker with a tighter sound post or different strings, but to some degree this state is intrinsic to the instrument. It often happens that students keep advancing and only notice they have a difficult to play instrument once they finally start asking a lot from it. Of course, K. Michael Krentz instruments are the fastest on the planet because of their carbon fiber composite bass bar design that makes them much more efficient.
Finally, if an instrument projects well, the player can relax in the knowledge that all their hard work is making it to their audience’s ears. But one of the most common complaints among players is that their instrument is just not powerful enough.
This can be quite hard to gauge in a small space. In fact, it is vital to audition instruments in both a small and large space. It seems to be a universal law that instruments that project really well are not quite as warm in a small space and it is this phenomenon that is responsible for the purchase of so many soft-spoken instruments.
The thing to keep in mind here is that powerful instruments can be fit with warmer-voiced bridges or darker strings or different sound post adjustments that will make it delicious in the small room. But no instrument with projection problems can be made to project more than about 15% more than a “normal” setting. Just like a fast car can go slow, no slow car can go fast and no matter how bright the bridge or strings or how tight the soundpost, your instrument will never turn into a powerhouse. Get the powerhouse, it’s more versatile.