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Rick Denney wrote: ↑Mon Sep 13, 2021 9:18 pm

humBell wrote:Not bothering to change anyone's mind (saving perhaps mine in the process, and i think i'm allowed to do that, perhaps even encouraged, and well i's mine anyway) but...

What is a right way of sizing a tuba?

3/4: is that a euphonium?
4/4: what you played in high school.
5/4: won’t fit in the back seat any more.
6/4: that’s a big-a$$ tuba.

Serious: Each manufacturer had a standard instrument, and built their scheme around that. Some (Rudolf Meinl is an example) built larger standard instruments than the norm. Thus, for RM: 4/4 meant .810 bore (?) and 18” bell rotary tuba. 5/4 meant .840 bore (?) and 20” bell. 6/4 meant .890 or something equally horrendous and a 22” bell. 3/4 meant .750ish bore and 15-16” bell. Beyond that, they were roughly similar in terms of their dimensionless ratios (except ratios that include bugle length). The 3/4 was about the same size as a Miraphone 186 or a B&S 102, which those companies called 4/4.

But the scheme doesn’t deal well with differences in proportion. Most piston tubas have a 3/4” bore (or smaller), but vary widely (so to speak) in taper and outer branch size. Believe me, my Holton is an entirely different beast than my York Master was, despite that both have a 3/4” bore.

Schemes have been proposed, but really playing characteristics only roughly correlate with dimensions (as opposed to taper design), so none of the schemes help much beyond estimating what size car you’ll need to carry it.

I once showed a picture of a York Master with the outline of a Grand Rapids York of the same size superimposed on it, to demonstrate their similarities. Chuck Guzis nearly refuted the notion that such a comparison meant anything by superimposing the outline of a Jin-Bao tuba-shaped object over a Miraphone 186. That’s what I mean by design.

Bigger tubas do sound different than smaller tubas of the same shape and general design, but other aspects can make a bigger difference in any particular case.

Rick “there is no right way that is definitive” Denney

Thanks for the long answer, and sorry for going MIA since posting my question.

Yeah i was hoping ordinary size without considering acoustic qualities would be there as a basic degenerate metric. And yes, it is important for making sure it fits in transport.

And it makes sense that within a maker's offered horns, they cna be simplistically consider to be different sizes of a similar enough tuba that sizing should hold as a way to compare them.

And i am not yet ready to open a can of worms.

Another open ended question: are there simple tests like opera singers cracking glasses, or getting good enough at plosives to blow out a candle at a certain distance, what show a level of effectiveness, albeit of little over all use, but easy to try?

peterbas wrote: Isn't this opposite then what the measurements on your website say. The York has more overtones then the Miraphone which makes the York sound more omnipresent.
And thinking about the exponential vs biradial horn thing, it seems that a tuba isn´t really a real horn at all. It is more like a conical tube with like 3 different slopes and only the last 50 centimetres you get something like a hornlike shape.
A true conical horn with an angle of 120 degrees and 5 metres long would have a bell diameter of 16 metres. The conical part of a tuba has like a 10 degree angle being only 50 centimetres at the bell.
The bell is also much to small for the low frequencies, for a 34 Hz note = wavelength of 10 metres the bell should be minimal 5 metres wide for proper horn working.
So I think the horn concept is not usefull for brass instruments.

Also what would be the difference between a wide and narrow tuba (of the same size) look like when unrolled to a straight line. Probably very difficult to distinguish between wide and narrow then.

No to the comparison on my web page being relevant. I never said anything about omnipresence in that article. I talked about what sounded deep, and a deep sound is not necessarily devoid of upper harmonics as some have supposed. It may actually depend on those harmonics.

Omnipresence seems to me about propagation, and that article was about spectral content, not about directivity at all.

And I doubt the importance of bugle shape to directivity. The “horn” is the bell only. The tapered tube and the mouthpiece are the transducer that is presented to the horn. Think of a JBL-Altec bass reflex horn in front of a 15” cone driver, rather than a Klipsch with a long horn in front of a 1” compression driver.

The tapered tube affects the timbre significantly, and also the intonation, but it’s not what primarily controls directivity, I don’t think.

Rick “recalling that Benade talked about this” Denney

humBell wrote:Thanks for the long answer, and sorry for going MIA since posting my question.

Yeah i was hoping ordinary size without considering acoustic qualities would be there as a basic degenerate metric. And yes, it is important for making sure it fits in transport.

And it makes sense that within a maker's offered horns, they cna be simplistically consider to be different sizes of a similar enough tuba that sizing should hold as a way to compare them.

And i am not yet ready to open a can of worms.

Another open ended question: are there simple tests like opera singers cracking glasses, or getting good enough at plosives to blow out a candle at a certain distance, what show a level of effectiveness, albeit of little over all use, but easy to try?

What do you wish such a test would show?

Rick “metrics are based on the stated objectives and the attainment thereof” Denney

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peterbas wrote: ↑Tue Sep 28, 2021 12:11 amThis is not so, the total shape of the horn is what makes it exponential or conical. You can put an exponential end on a conical horn but that wouldn't change it having a constant directivity and the other way around an exponential horn with conical ending will keep its changing angle per frequency directivity. The conical end would yes mess it up at the low side.

In the link you can download the directivity for various instruments. The tuba shows no directivity control below 200 Hz, every frequency is radiated out at 360 degrees.

https://scholarsarchive.byu.edu/directivity/

But most of what makes tuba sound characteristic of tubas is above 200 Hz. A low Bb has a fundamental of 58 Hz, but a range of harmonics are as strong or stronger than the fundamental, and absolutely define the characteristic sound. Everything above the fourth harmonic of a low Bb (which is a lower note than what is played, on average, in most music) is above 200 Hz. In fact, the difference tones of the higher harmonics are what help the listener define the pitch actually being played, which is hard to hear under 100 Hz. The Fletcher-Munson curve shows how much our hearing sensitive drops off at low frequencies, so we need those harmonics to be heard with any clarity.



In loudspeaker design, loading a dynamic driver with a horn absolutely changes its directivity relative to using a different horn. Yes, this is particularly true at high frequencies, but JBL and companies like them put gigantic horns on 18"+ dynamic drivers for PA speakers in large venues for a reason--they dramatically improve efficiency (read: sensitivity).

Rick "who doesn't want a tuba that turns a low Bb into a 58-Hz sine wave" Denney

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Except in PA systems. Loudspeakers with sensitivities of well over 100 dB SPL are common, and still use kilowatts of power for a large venue. Some are directive line arrays, but big, echoey venues still use horns.

Rick “recalling the Grateful Dead ‘Wall of Sound’” Denney

Didn't Phil Spector coin that Wall of Sound before the Greatful Dead did?

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KingTuba1241X wrote:Didn't Phil Spector coin that Wall of Sound before the Greatful Dead did?

The Grateful Dead built a wall of loudspeakers behind them on stage in 1974. Read about it here:

https://en.m.wikipedia.org/wiki/Wall_of ... eful_Dead)



Phil Spector used the term first, but in reference to a completely different thing. For the Dead, it was a literal wall of sound.

Rick “whose incoming stereo amp is relatively cheap and puts out 350 watts/channel—distortion-free power is much easier to get these days” Denney

peterbas wrote: ↑Wed Sep 29, 2021 12:32 am
No sub horns used in the Wall of Sound.

Note that this is an outdoor concert. I think the idea was to create undistorted PA sound that could also be used for stage monitoring, so that Jerry Garcia, et. al., could lose their hearing even faster. The horns of that day would have been Altec-Lansing (Lansing = JBL) A7 Voice of the Theater speakers, which are horn-loaded bass reflex designs that use 18" drivers. But the cabinet is large. These JBL L100's (or whatever they were using) packed twice as many drivers in a given square footage of wall. The A7's would have been louder, to be honest, but also more directive. For the typical outdoor rock concert of 1974 with their six-figure audiences, the sound field would need to be as wide as it is deep. Not at all the challenge for an echoey arena venue. But the guy's Wall of Sound in 1974 wasn't used by anyone else, so clearly there were some things it did not do to everyone's satisfaction.

And then there was the redundancy of having so many drivers and amplifiers. The amps used in the day would have been something like Phase Linear 700's, which weren't called Flame Linear for nothing. I doubt they used tube amps--they would have needed a nearby power station just to heat all those filaments.

Edit: Some calculations. If the back audience member of an outdoor concert was 250 feet from the speakers, they would need an additional 50 dB on the stage to create a given sound pressure level on the back row. If the SPL target for the back row was 100 dB (loud but not rock-concert-loud), they would need 150 dB on stage with this setup. That is immediately injurious to one's hearing. I suppose that's why a lot of the stack goes very high--to get it over the musicians heads. But it's still a dumb design. A horn is an acoustic impedance matching device that improves efficiency by minimizing reflection losses in the near field. With horns mounted to the side or above the musicians, they could put that 100 dB in the far field without destroying the hearing of those who are closer.

Rick "who served occasional duty as a minor roadie back in those days" Denney

That's an incredible smoke and mirrors side show, visually intimidating but yet, marvelous.


Maybe he meant, Wall of Hair?

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peterbas wrote: ↑Wed Sep 29, 2021 1:00 pm
Wasn't the main advantage a dedicated amp+speakers for every instrument, not a lot of power needed since no fullrange frequency spectrum for most instruments (piano excl).
And didn't they use some part mechanical anti-feedback because it would be impossible the play like this otherwise. But they didn't need any monitors for sure.

Horns also distort the sound so nowadays they mostly use waveguides to minimize distortion but they lose the gain for the higher frequencies. (see Geddes OS waveguide°
But with all that digital dsp power today it is easy and cheap to correct the frequency curve. A new RCF 710 is about the same price as a used one I bought 10 years ago and the new one sounds much, much better.

They probably distributed the signal to provide some staging, given how much they spread out on the stage. I have no idea how they managed feedback--I doubt there's a way to null out the spot where the microphone is and still provide monitor levels to the singer. With the usual line arrays that are now used, they are above the microphone and their gain pattern floats over the stage. But then you do need monitors for music that loud. At least the singer must be full-range, though, and usually guitars, drums, and (especially) keyboards are as well. I note a grand piano on the stage--that soundboard must have been dancing.

I include waveguides in the broad category of horns on purpose. Most waveguides are there to improve the directivity of high-frequency drivers to better match the naturally wider directivity of low-frequency drivers. They are focused on minimizing the impedance out to the side so that more radiation will fan out in better match to the low frequencies. That helps keep the first reflections in a room more timbrally consistent with on-axis spectrum, which in turn prevents the room's reflections from coloring the sound unduly. Revel is one of the leaders in those sorts of developments (being part of Harman, they had access to JBL's research facility and anechoic chamber in California, and they also had important access to Floyd Toole and Sean Olive), and their tweeter waveguides are really just wide, flat horns of complex (but mostly bi-radial) shapes. JBL also makes PA speakers intended for venues that are wider than they are deep that use biradial horn loading to minimize acoustic impedance laterally--sound people call them "lips" because of their shape--much of the "inside" of the horn is actually "outside" the horn--something our pancake bells approach. These have the opposite effect of horns that are intended to improve on-axis efficiency and protection from room echo in large reverberant spaces like churches and arenas. But the difference is the way they are shaped, not their presence, and that difference is what has triggered my line of thinking about bell shape and the height of bell stacks, which control directivity (whereas the entire bugle is responsible for on-axis timbral spectrum).

Rick "whose listening space is wide and tall, but shallow fore and aft, and uses Revel speakers to good effect" Denney

Even had I paid to attend (and didn't know about them ahead of time), if I saw that p.a. config, I would walk right out.

Were something like that ACTUALLY used to its capacity, I can imagine quite a bit of physical harm being done.

OTOH, I would wonder if that mess was - mostly - for show...(??)

(a bit like the outside two or three inches of a 26" sousaphone bell ??)

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peterbas wrote:

Rick Denney wrote: ↑Wed Sep 29, 2021 1:44 pm
I include waveguides in the broad category of horns on purpose. Most waveguides are there to improve the directivity of high-frequency drivers to better match the naturally wider directivity of low-frequency drivers. They are focused on minimizing the impedance out to the side so that more radiation will fan out in better match to the low frequencies. That helps keep the first reflections in a room more timbrally consistent with on-axis spectrum, which in turn prevents the room's reflections from coloring the sound unduly. Revel is one of the leaders in those sorts of developments (being part of Harman, they had access to JBL's research facility and anechoic chamber in California, and they also had important access to Floyd Toole and Sean Olive), and their tweeter waveguides are really just wide, flat horns of complex (but mostly bi-radial) shapes. JBL also makes PA speakers intended for venues that are wider than they are deep that use biradial horn loading to minimize acoustic impedance laterally--sound people call them "lips" because of their shape--much of the "inside" of the horn is actually "outside" the horn--something our pancake bells approach. These have the opposite effect of horns that are intended to improve on-axis efficiency and protection from room echo in large reverberant spaces like churches and arenas. But the difference is the way they are shaped, not their presence, and that difference is what has triggered my line of thinking about bell shape and the height of bell stacks, which control directivity (whereas the entire bugle is responsible for on-axis timbral spectrum).

Rick "whose listening space is wide and tall, but shallow fore and aft, and uses Revel speakers to good effect" Denney

Dr Geddes is one of the prominent researcher of OS waveguides.
On his website you can find 2 free books about transducers and home theater. http://www.gedlee.com/Loudspeakers/Loudspeakers.aspx
Interview: https://www.audiosciencereview.com/foru ... dio.22921/

Yes, I know about those papers, and I do have a presence on ASR. Good stuff.

Rick “a good tweeter waveguide makes a speaker” Denney

So if tuba bells were detachable just after the bottom bow, one could (theoretically) show up to a gig with 3 or 4 different bells and then choose the bell that would work best in the available playing space.
But...
would the results be a considerable improvement?

I actually have a tuba for which I have four bells that all fit it, and are all different.
I like one of them the best, but it has drawbacks. The second-best one doesn’t have any drawbacks. I don’t like the other two.
… so one of them (2nd best) mostly tends to get used.
I believe interchangeable mouthpipes have shown themselves to be about the same; their owners tend to use one, and the other one remains in their sock drawer - in new/unused condition.

pjv wrote: ↑Wed Oct 06, 2021 1:32 am So if tuba bells were detachable just after the bottom bow, one could (theoretically) show up to a gig with 3 or 4 different bells and then choose the bell that would work best in the available playing space.
But...
would the results be a considerable improvement?