Bars, Resonators. Their behaviour and how to act with it.
Bars, resonators and their tuning.
Base of the vibes' sound ofcourse are the bars, and in a huge amount the (tuning of) the resonators.
I'll try to explain in the next article how to tune the bars, how to tune the resonators, and how to get the best benefit from the resonators.
It is widely know that vibe bars have their fundamental tuned, and the first overtone to a double octave.
At general, the overtone can be tuned up to G5 (some brands can go up further). Above that bar, the first overtone isn't cared for anymore and drops more with every next bar.
With the regular 3 octaves (F3-F6) vibraphones, this tuning is good enough.
However, going down to C3 (3.5 or 4 octave vibes), just tuning the fundamental and the first overtone isn't enough.
With the metal vibraphone bar, the 2nd overtone is heard too significant.
Also the 2nd overtone lies within the range of the instrument (which is not the case with a 3 octaves F-F), and therefore should be tuned.
Not tuning, or not tuning accurate, will make the low range bar sound like a milk bottle.
From the marimba world we see that it is common to tune this 2nd overtone to a major 3rd (triple tune, which is mostly done at the range lower than the C3), so it is a good option to use this same tuning to the vibraphone bar.
We are able to triple tune our bars up to F#4, sometimes up to G4.
However we do change from a major 3rd to a minor 3rd at D#4. This is because the size of the bar doesn't offer room to tune the major 3rd above that range.
When starting tuning, ofcourse the harmonics (overtones, partials, or whatever name is used) are pretty random, and it is up to the tuner to line them all up to a usable musical bar.
For example, after the first cut (done by the CNC machine) of our low C3, its' harmonics can be spread as:
- C#3 +40cents
- C#5 -20cents
- F6 +45cents
Now by removing material at the bottom of the bar, we can drop pitch of any of these harmonics.
- tuning the 2nd overtone, also affects 1st and fundamental
- tuning the 1st overtone, also affects fundamental
- tuning the fundamental, also affects the 2nd
So when removing material, it is important to find the right spot at the bar, so that each harmonic drops with a controlled pitch.
The more we reach the final destination, the closer to each other the harmonics are, e.g. at almost the final stage, the harmonics can be spread as:
- C3 +15 cents
- C5 +5 cents
- E6 +2 cents
As you notice, the lower partials/harmonics don't pass the higher partials/harmonics downwards. Once e.g. the C3 has passed the C5, it will be more difficult to get the harmonics nicely in line again at the final destination.
So it is important to work with the higher overtones first.
The tubes underneath the bars, don't produce sound themselves. They are there to boost the volume of the bars by having the vibration of the bars getting the air inside the resonator tube to vibrate.
By tuning the tube to the pitch of the bar (done by moving a cap at the bottom), the vibrating air will add up to the vibration of the bar, and thus increase volume.
The length of the tube is as such choosen that it only increases the volume of the fundamental tone.
The closer the resonators' pitch is to the bars' pitch, the more (fundamental) volume we're getting out of the bar.
However, this is in a very close harmonic area.
If the tubes' pitch is more than half a semitone from the bars' pitch, then forget about any resonance.
There is only a certain amount of energy available in the bar: energy that comes out as volume and length (sustain).
Increasing volume means decreasing sustain.
It would be valid to think tuning the resonator to an exact pitch of the bar would be the best way to do.
But it isn't!!
Having both pitches to an exact match, will cause a huge boost and causes a really big drop in sustain.
Specially in the high register of the bar range, the bar itself doesn't have enough mass to continue ringing. But also the low register can have sustain dropped from 20 to 3-4 seconds at most.
We found that the best pitch for the resonators is just below the bars' pitch.
In a perfect environment, bars and resonators have the same pitch as what they had when leaving the factory.
drop in temperature causes a raise of pitch to the bars, and a drop of pitch to the resonators.
Raising the temperature causes drop of pitch to the bars, and raise of pitch to the resonators.
Already with 3-5 degrees celcius this is noticable, specially in the lowest range C3-C4.
So the vibe only sounds best when it is in the same environmental temperature as where it was tuned.
A massive sounding low range in a 3.5 or 4 octave instrument sounds thin as soon as it is colder or warmer than it's tuning temperature, but also a 3 octave F-F vibe has noticable differences in the range F3-C4.
This means that when using the instrument in several environments, it is best to be able to adapt the resonators' pitch to the bars' pitch. This can be done by adding tunable stops to the resonators.
Ofcourse using tunable resonators means you have to know how to use and tune.
Unlike a marimba, with the vibraphone it is not just a matter of getting the best ratio of volume and sustain.
We also have to deal with the fan that's at the top of the resonator.
As soon as this fan closes, the pitch of the tube drops. So in fact there is a fan angle where the boosting of the volume actually starts happening. With tuning the resonator, it is vital to have all the fans start acting at the same angle.
Having the resonator pitch too low, means you don't get enough boost, having it too high means you can have the maximum boost at 45 degrees (meaning you've doubled the vibrato frequency, as there are 4 positions where the fan is at 45 degrees).
Tuning the resonator.
It takes time to become an experienced resonator tuner, but once you know how to, retuning resonators can be done fast.
First you need to do is checking the current pitch of the resonator. This is done best by blowing across the tube, just beneath the bar. Make sure you're blowing in the proper tube!!
It is OK for this moment to listen if you're just in the neighbourhood of the bars' pitch.
If you're not, and if the resonators' pitch is too low, the endcap needs to be raised. If pitch is too high, the cap needs to be lowered.
Once the pitch is near the bars' pitch, it comes to fine tuning the tubes.
Remove the bars and blow just above the tube. Raise or lower the endcap untill by ear you've reached the bars' pitch.
In our experience you're then pretty close to the end result.
When you've reached the proper pitch, put back the bars.
This will drop pitch of the resonators just a bit, and in most cases just enough to get the best ratio of "volume/sustain/fan intervean".
But we're not there yet!!
Press the pedal to get an undampened bar.
Hit the bar and listen carefully.
Now, while the bar still rings, grab the end of the bar inbetween thumb and fore finger, and hit the bar again.
Focus on the sound coming from the resonators ISO the sound coming from the bars (which is rather difficult, and you need to focus really good). You may probably have to squeeze and unsqueeze a couple of times to get focussed and to learn to what you need to focus on.
If you're experiencing a drop in "air"-pitch, the tubes are still a bit too low. Raise the endcaps just a small bit, untill there is hardly any drop at all anymore.
If you've followed the whole procedure, it isn't likely that the pitch of the tube is too high.
When finishing this whole procedure, you've created the most effective sound coming from your vibe.