josh_kaprun wrote:ok, no sparring. this post is about doing tweaks, not arguing about impedence.
Sorry, too late.
Remember, though, that nobody owns the thread. Threads wander around, and sometimes nuggets emerge as a result. Sometimes not. Skip past it if you aren't interested.
Rick "thinking a little frequency-domain science won't hurt anybody" Denney
Hmm. The flat 5th partial syndrome. After reading bloke's comments, last night I made some observations and measurements. A BBb tuba is roughly 18 feet long, give or take a few inches to compensate for bore, flare, etc. 18 feet is 216 inches. 216 divided by 5 is about 43 and a fraction. So I measured 43 inches down from my bell rim. On a regular conventional bell 186 that distance is right about the big ferrule attaching the bell stack to the bottom bow. On mine, with the shorter retrofitted upright detachable bell necessitating a longer main tuning slide, that puts it just under the ferrule. As a result, the node for C, being a whole step lower pitch, is under the ferrule starting into the bottom bow curve, at about 48 inches.
Then I got out my tuner. Surprise, surprise! D is flat as you might imagine. But Db is only slightly flat, and C is right on.
So, I wonder if the bell stack proportions and bottom bow were re-engineered to either change the taper slightly at that point, or redo the positioning of the ferrule, if that would solve the flat 5th partial problem? This is since the ferrule adds mass and creates a mechanical incontinuity, and the mantra, added mass damps vibration and changes characteristics (mechanical impedance, as described above).
OK, I also know that the terminal node is actually slightly beyond the rim of the bell, effectively slightly lengthening the horn, but even allowing a couple of inches for that, on my particular example, the D node is still at the ferrule and the C node is still along the bottom bow. On a conventional 186 BBb, they are all in the neighborhood of the bell stack ferrule.
josh_kaprun wrote:ok, no sparring. this post is about doing tweaks, not arguing about impedence.
Come sit beside me, grasshopper. Listen and learn as the tuba men joust about. It is all a part of the vast knowledge that must be acquired to be rightly called a tuba man.
I was just explaining last night in a band officer meeting why the (french) horns should not be seated in front of the bass drum or the timpani. Unless you have sat there and felt the whack on your chops when the percussion gets excited, you wouldn't believe what disturbances in the frequency domain can do to the waveform inside the instrument.
It's not exactly a tweak; but I've had good success exchanging the original Mirafone bells for the old Conn monster Eb bells. If you looking for a more robust "American" sound, that'll do it for you. It's also a great fix if the Mirafone bell is trashed. I have a few of those old Conn Ebs sitting around if anyone needs a bell switched out on their Mirafone tuba. It'd probably work on some of the Cervenys, Meinls, Alexs and other Euro horns too.
What exactly is the different between the stock Miraphone bell and the old Conn Monster Eb bells that makes a change in the sound? Does it affect the way the horn plays? projection? tuning? weight?
josh_kaprun wrote:What exactly is the different between the stock Miraphone bell and the old Conn Monster Eb bells that makes a change in the sound? Does it affect the way the horn plays? projection? tuning? weight?
To begin with the Conn bells are 20" diameter. They're a thicker gauge brass and a different alloy. The throat of the Conn bell is wider. They typically give a broader sound but still with clarity and crispness of attack. I think this leads to better projection and presence in the sound. It also seems to improve the way the horns slot. The horn takes on a totally different character of sound with the Eb bell. Personally, I like the change, but it's probably not everyone's cup a' tea.
It doesn't seem to mess with the tuning.
Of course this is all pretty subjective, and we were going from horns with original bells that had been pretty much trashed. It was bound to be an improvement in those circumstances. I agree with other posts that if your original bell is in good shape you should think twice about exchanging it for a Conn bell. It's not a cheap operation, but, unlike some surgeries, it is pretty easily reversable.
