Jim Williams wrote: Fri Mar 13, 2026 7:51 pm
Here's another hypothesis that I think may apply to heavywall mouthpieces as well as other gizmos:
There's an analogy between radio transmitters & receivers and brass instruments. We could view a brass instrument/player/mouthpiece as a tuned circuit. With my ham radio gear, the transmitter feeds power to the antenna. With a tuba, a player is feeding power to the tuba. Devices like heavywall mouthpieces may well serve to increase the "Q" (response quality factor) of the tuned circuit. A high-Q system will enhance power transfer (from transmitter to antenna or from tuba player blowing into a mouthpiece) on frequencies it is set for, at the cost of attenuated power transfer on frequencies removed from the focal point. This might explain why players feel better slotting when using a heavywall mouthpiece. It is enhancing certain frequencies and attenuating frequencies away from the focal point. I could go on with more, but I'll stop here...anyone with knowledge of radio electronics, please feel free to chime in.
But my two cents is that most of these gizmos increase the Q of the tuba. What remains unknown--and never stated by the gizmo makers--is what parts of a signal are suppressed when the gizmo is used, with what consequences. Are harmonics attenuated? If so, which harmonics, by how much, and with what effect on the sound?
Someone could look at a waveform produced by a tuba WITH the gizmo vs. the waveform produced by the tuba WITHOUT the gizmo, holding everything else constant, and determine what the gizmo has changed in the waveform.
Adding MASS of any kind to a brass instrument is kinda like adding a capacitive hat to antenna. Response to input will change.
This will be my boring dissertation on the topic of the thread, not just a response to Jim’s theory. Run away now. You have been warned.
Jim, you have to consider the frequencies. An RF transmitter will be sensitive to effects in two very different frequency bands—base-band audio (for radio, 200-3000 Hz for typical single-sideband operation) and a carrier frequency that maybe be anywhere from 1.8 to 1200 MHz. And on the receiver side, the receiver will be mixing that signal with one or two intermediate frequencies (70 MHz and 455 KHz for the traditional up-conversion triple heterodyne method). With all those frequencies in play, there are all sorts of opportunities for oscillation (ringing) well above hearing that can cause audible intermodulation distortion. Most of that, however, is “heterodyning”—the result of imperfectly reconstructing the base-band audio from the single sideband—and not intermod at all.
But there is no carrier frequency or heterodyne reception in a tuba. The lips produce frequencies in the range of maybe up to 20 KHz, most of which is attenuated out because the tuba only resonates harmonic frequencies with any strength.
The mechanical ringing of a metal mouthpiece shell is all over the map. I cannot get multi part threaded mouthpieces to ring at all—the threaded connections seem to damp oscillations altogether. A Conn Helleberg (light) rings at about 4.7 KHz, a one-piece brass Sellmansberg (heavier) rings at 5.7 KHz, and a very heavy Mike Finn 4 rings at 5.9 KHz. But to get them to ring at all, I have to strike them with a metal striker when they are floating on a soft, fibrous surface that minimizes contact. In a tuba, the taper shank damps those frequencies almost completely. Those gooey lips pressed up against them damp what remains to a dull broadbanded thud.
I don’t think there is the slightest shred of acoustic content in a tuba tone that reaches anywhere near 4-6 KHz, and even if ringing there mixed with tuba tones, the intermodulation would have to be well over 60 dB down, and I’d bet more like 100+ dB down if it exists at all. In other words: inaudible.
And I doubt that anyone’s lips can feel vibrations of 4-6 KHz, even assuming those vibrations wouldn’t be completely masked by the mechanical buzz vibration, which it would be.
But even if they did, I have not heard anyone opine that threaded mouthpieces affect the sound (as long as the parts are tight) and those threads have about as profound an effect on the resonance of the metal as making it out of plastic.
Also: Brass rings more than stainless steel. Did anyone ever notice that?
Various theories have been postulated about the effect of the resonance of the air inside the mouthpiece; the “popping” frequency heard when you slap a mouthpiece opening with your palm. Popping frequencies for my largish collection mouthpieces range from 390 Hz to 430 Hz, with those being the peak of a fairly broadbanded hump. (The Redhead is still asleep, thank goodness, else she’d have just shook her head as I was popping mouthpieces into the spectrum analysis app on my phone). I found no consistent correlation between popping frequency and mass or material, nor did I see the slightest presence of the ringing frequency when popping those mouthpieces that didn’t already damp ringing. Popping frequencies are definitely within the harmonic envelope of tuba sound, but they are all about the same despite that the mouthpieces themselves behave quite differently.
Mouthpieces are the first impedance-matching device downstream from the lips, and the interior shape affects all sorts of standing waves at frequencies that do work on the high-frequency noise in the buzz. The more of that noise (harmonic and enharmonic distortion, in electronics terms) it lets through, the more zip there will be in the sound, though enharmonic noise may detract from it. Brass instruments need (especially) harmonic distortion to cut through air and room noise effectively. Trumpets and trombones have high levels of harmonic content in their sound.
Examples of that abound. Moog famously made a mistake in the sine-wave oscillator amplifier for the Mini-Moog Synthesizer of the early 70’s, which caused significant second-order harmonic distortion. Musicians loved it—it made it much easier to amplify to rock-band levels and compete with electric guitar sounds.
Listening to Mason Soria’s sound compared to the excellent grad student he was teaching revealed one difference between excellent and world-class: His sound had that little bit of additional zip that gave it more meat and carrying power. That zip was increased harmonic content, not “darker”, or “more rich in fundamental.” I think people who say such things as I put in quotes have never looked at a frequency spectrum analysis. Mr. Soria’s sound had that zip even playing very softly.
I can think of no physical reason for the material or mass of the mouthpiece to affect that result, as long as the mouthpiece is stiff enough not to vibrate in the popping frequency range or below. I have to conclude that interior differences account for observed effects, assuming those effects could be detected at all in controlled testing. Bias is unavoidable, though, as Rob pointed out, a placebo effect is still an effect. It just can’t be attributed to the feature as claimed.
Rick “thinking we had this discussion 20 years ago at that other place” Denney
