"Classical" or "Jazz" setup?

"Well, orchestra players need their strings really high off the fingerboard, but us jazz players need low action."
"High action is for jazz, but you have to understand, a classical setup means low action."
'You have to get rid of all that resonance/ring for jazz."
"My teacher said to come here to get a bass, but I looked around and all your basses were set up for jazz."
"You have to have the E string really high off the fingerboard so you can bow it."
"You can't play Spirocores with a bow."
"That bass has a pickup on it so it's a jazz bass."

Is there such as thing as a "classical upright bass" versus a "jazz" bass? In a word: no. Watch my lips: NOOOOO. There's nothing inherent about a 4-string upright bass that would make it incompatible for either use, so is there really a difference in setup? Sometimes, but it's a matter of the individual player's requests. Setup specifics for either jazz or orchestral playing are not actually quantified! 

What is 'setup'? The main components are the shape of the fingerboard and bridge, which control the height of the strings off the fingerboard and the amount of string tension you will feel while playing. There are numerous equally important setup factors such as string spacing and height of the nut, curvature of the bridge, the sound post, and the tail wire. A good setup consists of first, carefully and knowledgeably shaping the fingerboard for minimal camber (scoop) under the strings in order to minimize the tension your left hand must apply in order to sound the notes clearly. The less tension, the faster you are able to play accurately and comfortably, giving you the widest possible vocabulary and expression on your bass. Then, shaping the bridge to complement the fingerboard shape, and adjusting its mass for an optimal balance of resonance and strength. The string height and choice of strings are decisions which fall to you, the player, and aren't inherent to the type of music. Some strings are definitely made to work better (or exclusively) for pizz or arco. For those specifics, see our page about bass strings and our Interactive Bass Strings Chooser.

There are many fine professional bassists who work equally in both classical and jazz ensembles, and while some may maintain two basses with different strings and possibly an electronic pickup, you can be certain they wouldn't settle for a bass they couldn't play with a bow, or with excessive fingerboard camber that made it tiring or limiting to play, so the setup differences would be minimal. They would have invested in their basses for their tone and other values, then have them set up for their particular needs and tastes. Just as they do, you can play on any bass that appeals to you, and request individualized setup or on-the-spot adjustments to your preferences.

What makes a "jazz" bass a great find? Often, a bass that's been played long-term for jazz has phenomenal tone, developed over years of assertive pizz playing. They tend to have an outstanding tone-to-price ratio. They're less likely to have permanent blackening of the varnish in the bridge area from old rosin. They often retain more of their original features, such as the neck set and tuning machines, with fewer modifications that have become more and more standard for orchestral playing.

What distinguishes an "orchestral" bass? If a vintage or antique bass, it's more likely to be found nowadays with the neck having been replaced or reset for more overstand. It's more likely to already have a C extension. Both the modernized neck set and extension can be an asset to any style of playing (usually translating into higher selling prices). There are more numerous antique, famous-maker, carefully conserved stringed instruments traded in the classical scene, but prices get pushed into the stratosphere and the instruments don't necessarily sound or play better.

What will I get if I ask for a "classical setup" or "jazz setup"? Actually, you'll get a lot of questions to dissect what you want. How high do you want the strings, exactly? Have you experimented with having the sound post in a different place? What strings do you want? Etc. Your bass will be inspected for open seams or other needed repairs, and where it may need adjustment or the fingerboard and bridge re-shaped/replaced. There are "standards" for string height and spacing, which we aim to use as a starting point, adjusting to any anomalies of the bass, and then the client's requests. These starting points, since they're based on the physics of how double basses behave, are the same for both classical and jazz playing. There are limits on how much they can be altered and still have the bass play normally. 

Does QBC have "jazz basses" or "orchestra basses"? In a word, yes. We have vintage and antique basses that were formerly set up for jazz players, orchestra players, bluegrass players, and players of multiple styles. By request, all those details can be changed. On arrival, basses are inspected, maintained, repaired if necessary, and adjusted to have the widest possible appeal to bassists of all styles. New basses are set up to be equally playable by any player. We fully expect to be asked to adjust an instrument or to put on a different brand of strings to suit the client.

How will you know which basses are for your style of playing and how you should shop? Simply, by playing them, asking questions, and learning about adjustments and the characteristics of different brands of strings. All questions are viable, and the only mistake you could make would be to overlook a great bass that's potentially your musical soul mate because of a categorical "setup" perception.