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Lawson 'lite'
On this page we discuss how the wall thickness of your horn influences its' playing characteristics. To read a brief description of our newest addition of lighter weight horns to our model lineup, please visit our models page. Most musicians have an intuitive sense that a lighter instrument plays 'lighter' or more responsive, and consequently a heavier horn should produce a 'richer tone'. We have found that if only the lower bell branch is reduced from .020" thick to .016" there are significant changes in the instruments' response as well as tonal quality. In order to make meaningful comparisons from a player's point of view, we asked David Bakkegard and Peter Landgren both of the Baltimore Symphony to play a G4 written on the F horn, open and without a hand in the bell on three types of double horns. The first, used as a basis for comparison, was one of our standard large bore Fourier models, with a bell branch thickness of .020"; the second was a design similar to many smaller bore types of instruments, usually noted for their ease of playing; and third a Fourier model with a bell branch thickness reduced to .016". The two musicians played as loud as they could for as long as they could.. Instead of using a dB meter to keep loudness consistent, we had them play with a small capillary tube inside of their mouth and connected to a manometer which monitors oral pressure. We've found this to be better than a sound level meter because it indirectly indicates what we are really interested in, a constant air flow. The flow and the time they can play at a constant flow can be associated with the amount of the lip opening which in turn is associated with the internal dynamics of the instrument. The following graph is three oscilloscope tracings of a very typically loud note G, on the staff.
The .016" belled horn is green and on top; our standard weight bell branch, .020" is blue, in the middle; and a prototype small bore horn is colored red, on the bottom. The graphs are displayed so that differences in the envelope of the notes are easily seen. The envelope is a gross characteristic of a played note and represents the changing amplitude in milliseconds as time progresses. The much discussed startup or rise of the note begins in the first few milliseconds, followed by a long sustain of up to approximately 6 seconds for Peter and David playing as hard as they could, then the decay of the notes in the last few milliseconds as they ran out of air. Comparing total times the players could continue, the lighter weight bell branch, green, certainly was longest but the amplitude of the sustained portion was not quite so loud as the heavier belled horn, blue. We believe that this phenomenon is interpreted by the player as 'blowing resistance', hence the lighter material would feel less resistant. Unexpectedly, the smaller bore horn which initially feels very easy to play had the shortest sustain time and the most variable envelope. The initial few milliseconds of startup was most stable in the lighter belled instrument.
It would be nice if we could slow things down so that we could easily perceive these subtle differences as audible. Unfortunately, if we slowed down the recording as you would slow down the playback speed of a tape you would notice a severe lowering of the pitch. However, with some routine digital signal processing we can expand the time parameter so that we can hear the differences without a change in pitch.
Click on the two different recordings for an audible sound of the first few milliseconds of a typical sampled note played by Peter Landgren who played for us the famous horn passage from Mendelsohn's Nocturne. E flat, top of the staff, is the focal note and the two recordings are just the first few milliseconds. It's important to note that Peter was unaware of the recording so that the characteristics of the instrument were not affected by any subtle adjustments he may have wished to make. We compared the .020" thick bell and the .016" thick bell.
Here's a graph visually comparing the two waveforms. The heavier bell branch is blue, on the top.
Carefully listen for the 'burble' at the beginning of the recording with the heavier (.020") bell branch. This is the moment where the feedback from the instrument interacts with the lips and gradually settles into a synchronous vibration. A player would interpret this as a slightly slower response, but this does not necessarily mean anything is wrong, because if we look at the longer sustained portion of the note, we would find that the overtone harmonics are stronger for the heavier belled horn. The three sound spectra graphs below represent the harmonic overtone series for all three instruments as sampled from the original waveforms shown in the first graph.
These graphs show the strength of vibration (amplitude) of the lip and air column harmonics in the horn as the instrument is played and present a very objective, clear picture of important playing characteristics musicians discuss all of the time. Characteristics like response, tone color, and stability are all represented. The horizontal axis represents frequencies of the played harmonic (the first peak) and its' multiple overtones; the vertical axis is the amplitude, and the Z axis is time. Comparing the above three spectra, clearly the bell weight makes a difference in tone, initial response and also a playing characteristic we term lock-in or stability of the note. For example, the small bore instrument has comparatively higher energy in the upper harmonics but consequently less amplitude at the played harmonic (the first peak). The light weight bell is noted for most of the energy distribution being concentrated at harmonics 1 and 2 and fairly quiet at the upper harmonics. Because of the lack of measured amplitudes of the overtone harmonics we believe that the thinner bell branch is responsible for redistributing some of that energy towards the frequency of vibration of the lip and its' first overtone. From a player's perspective this will result in a more stable note going forward in time and a feeling of less 'resistance'. This is evidenced by observing the lack of variation in the played harmonic (the lowest peak) going forward in time, along the Z axis, for the .016" bell branched horn.
In order to give the reader an entertaining, audible demonstration of the differences between the two weights of instrument being played, you might wish to click the button below. Please be advised, this is a 1 Meg .mp3 file so it will take a little while to download at 56K and you will need an .mp3 player to hear it. Most Windows media player versions can play these, else you will need a program such as WinAmp, Realplayers jukebox or SoundBlasters media player. What you are hearing is the first part of Meglio by Henry Mancini with the lead voice split between synthesized versions of our light weight belled horn and the standard weight. A little explanation is required here. The manner of synthesis is very important because, similar to what we did above with magnifying the audible startup, here we have taken a brief characteristic sound sample from each horn being played by Peter Landgren, then ran an algorithm called looping which repeats the waveform over and over and finally, changing the envelope characteristics of the notes, specifically the attack and release times. You would find that these parameters are more important than the small variations in tonal spectra between the two instruments. As measured the heavier belled instruments startup time for the note which Peter played from the Nocturn was just under one tenth of a second or 100msec. The lighter version's measured startup was around 50 msec, same with the releases. We set the synthesizer settings for these parameters to 0 msec for the lighter one and close to one second for the heavier one in order to really make it obvious how much this controls what we hear. See if you can identify the four changes between the two instruments in this brief passage.
To summarize, we believe this clearly shows there are significant differences between instruments with different wall thicknesses; and that the bell branch is most responsible. The heavier bell yields a little louder sound with a somewhat richer overtone series and certainly is more mechanically sound, while the lighter material seems to have a quicker, cleaner response, lighter tone and 'locks-in' a little better. The type of music generally will dictate the optimum instrument. Chamber or ensemble musicians may find a lighter instrument fits that style better; whereas, a heavier horn might make sense for larger classical groups, but it must always be kept in mind that the player has enormous control over the instrument's characteristic sound and response and even a small change in a mouthpiece or one of its' parameters like depth of cup or throat diameter can heavily influence the way a horn responds.