Here are my observations so far:
Update 17Nov2014: See Tom Ridenour's video: Sharp Low Register This contains great information about bore sizes.
“Should I get a poly-cylindrical clarinet?”
I have had several people ask questions like John's:
Phil, I sent you a message earlier regarding your recommendation for an adult beginner clarinet for someone interested in jazz who has some music background with flute and sax. The Normandy sounds interesting but would I be better off with something newer with a poly-clyindrical bore? A student horn is probably all I need at the moment, but I think I would quickly outgrow it. I am thinking of a wood or hard rubber intermediate horn would serve me best. Don’t want to spend a lot but still want something I’ll be happy with. What would you recommend?
My response to John:
You ask a tricky question! One has to balance financial cost with intonation. Not an easy comparison.
If you are an adult beginner, I don't really think you are going to notice whether you have a poly-cylindrical bore or not. I normally think good straight bore instruments are fine for beginning to fairly advanced players. You won't quickly outgrow a good student model clarinet unless you are an exceptional musician!
However it is good to be precise and understand what a poly-cylindrical bore will give you: First, the biggest difference in intonation happens in a pretty restricted area, namely low D and down to around low G. If playing on a straight bore instrument, you may have to pull out for an exposed soft solo where the lower register is prominent. If you are playing loudly, you will be likely not need to pull out for the passage. Passages like that are infrequent, so I don't consider it a huge point unless you are a semi-pro player or unless you are often playing in the low register with a piano. Secondly, a poly-cylindrical barrel will improve response. You can add a better barrel with almost any student horn.
You will probably be happy with a wooden instrument. If you want extra dark sound, you can go for a Ridenour hard rubber instrument. But you get virtually the same sound with just a Ridenour barrel ($45 on eBay plus $5 shipping) on a wooden instrument.
The most important part of your clarinet will be your mouthpiece and reed. So if you are on a budget, you could go for a student horn but upgrade the mouthpiece.
Knowing that your bent is toward jazz helps. Is your type of jazz centered in the low register? If not, you may enjoy a wide bore clarinet, like so many other jazz players.
Hope this helps! Feel free to ask more.
I have some interesting information from Tom Ridenour:
My question to Tom:
I have several clarinets that I am working on or playing and they have different bore sizes. For instance I have a Selmer Signet with a 15.2mm bore, an Artley wooden clarinet with a 15.0 bore, a Normandy with a 14.85 bore, and more than one French "stencil" clarinets with a 14.5 bore.
Given that I am trying to play all of these with the same mouthpiece, should I get different barrels for the differing bore sizes of the clarinets?
Not necessarily. Overall tuning should be the first determinant. Next, specific tuning and the inner relationships of tuning. I would imagine that the real exception to this list would be the 14.5mm bore clarinet. These are pretty extreme dimensions nowadays. Most clarinets played by professionals are between 14.61 and 14.7mm, because this bore size yields the best tuning over all.
My question: How have your barrels worked to tame the sharpness in the high register on the Selmer Signet or others?
Such problems are due to acoustical design. Nothing in respect to mouthpieces or barrels can really correct acoustical flaws in the upper and lower joints. At best, barrels, mpcs and bells can only reduce the bad effects of bad design. The right hand lower register sharpness of the Signet can't be corrected either. What my barrels do primarily are improve tone, especially the upper register, and remain more stable than wood, so the clarinet plays more the same for you from day to day–they don't crack either.