Messages

Well that formula - 1/4 wavelength -0.61r is as close as you can get in my experience. A couple of things to think about if it doesn't seem to match reality. 1. measure the actual frequency of your bars - bars are not always in tune so can drift away from resonators. 2. Be sure to consider both tuning standard (ie A440? 442?) and temperature/humidity. Remember W=V/F where F=frequency and V=velocity of sound - but that will differ depending on the air temp and humidity. Plugs can have a "seal point" that is not quite as it seems. Ideally we are looking for a perfect flat resonator floor that seals at the exact boundary -  but that is often not the case. That top surface of the plug closest to the bar is where we are measuring to of course - but if the shape is slightly concave or convex or has a bump or if the seal point is a bit further down in the middle of the plug... it will make the direct measurement inaccurate.

My best advise if you are making new plugs, is to make adjustable ones so you can move it till you get it working well with the bar. The simplest way is to use a holesaw to cut out 2 SLIGHTLY undersize disks of 3/4" plywood - find an O ring that is pretty much a perfect OD fit to the ID of your tube (thicker is better like about 3/16" or 1/4" rubber diam) Insert and glue in a nut to your top disk - bolt with a couple of locked nuts from the bottom so tightening the bolt squeezes the O ring to lock position and enough bolt protruding to use as a handle. That's about the simplest and cheapest way.

Hi there Quentin - great to have you on board!

Hi John - sorry I can't help you - this forum is just for percussion related discussion - I personally don't know enough about guitars to answer that!

Hi there Almonte!

SO do you mean whilst tuning the bars/resonators??? Or do you mean on stage - or in your home perhaps?

I've both performed and built now in both extremes of climate - from South Australian Summer to Canadian winter... so I have developed a few strategies for most scenarios now!
Jim

Oh - right - yes I have seen  this many times. Usually though historically it tends to be on cheaper Orff instruments where the bar dimensions are less than ideal for the fundamental bar pitch. I am surprised to see it here. As far as I am aware this is a method used to control a completely different type of overtone - a TORSIONAL mode.  have personally never had an issue with a marimba bar made to pro standards that required this technique - though from time to time with diatoninc school instruments.

HI there FanYang - good to have you here!
I'm not quite sure what you are referring to when you say "X" gap - can you possibly explain that a little more?
You also say that there is some material removed from under the bar but at the END of the bar - you mean on the outer side of the string hole? If so that would have the effect of RAISING the bar's pitch - not lowering it. Generally speaking when raising the pitch of a bar it is almost impossible to control which modes get raised by how much - they all get raised together. One raises them all then brings them down selectively by removing material at the various select points BETWEEN the nodes. Even so - raising should not really have to be done at all - generally if this is done, it means there was an error in the initial tuning stages.
Jim

Unfortunately the Simple glock guide is exactly that - a guide for a simple glock. It is not really similar to the instrument you would use in orchestral situations, rather more the sort of generic metalophone that you might find in schools etc. For an orchestral glock you would be better suited to go for thicker bars - like about 10mm - and high carbon steel is best rather than aluminium - though some do use various aluminium alloys like the 2024 that is commonly in use for vibes. You would also be better off going with a bit more length for the bars at the top.

Getting a set of measurements is not so tough really - you just go with an arbitrary length that works well for the tuning - for your top note and your bottom notes. Then you lay out your black note and white note rows with the correct spacing between (can be just done on paper of course as you have not actually cut the bars yet!) The bar lengths in between the top and bottom are simply a linear graduation - so literally rule a line between the ends of the top and bottom and you have the lengths in between. This is the method that will correctly give you bars that have nodes lining up over your struts in the end.

If you want to extend the SG plan - then just do exactly this - line up the bars that are given... then rule a line further down, and get your lengths that way.

Hope that helps!
Jim

Temperature changes are very much the enemy of bar percussion tuning!
The situation is worse than the bars and resonators not being affected evenly - they are affected in the opposite direction to each other! An increase in temperature will make the bars go DOWN in pitch, but the resonators go UP in pitch.... therefore it is quite important to fine tune both as close to the final playing room temperature as possible. For example when fine tuning bars I tune them to perfect correct pitch, then place the bars in a temp controlled room - just my lounge room with the air con on set to 21 degrees - and leave them for at least 10 minutes there to equalize. Sanding the bar will create friction and warm it up, so after ten minutes in the room I take it back to the sander and quickly touch tune it again as it will have gone up in pitch above the zero mark a little. I repeat this a couple of times to make sure it ends up correct. I make sure I tune resonators in the same room.

The whole point of having that adjustable height on resonator banks, is to compensate for temperature variations. Sometimes if we play the marimba at higher temperatures it will start to sound a little off - the resonators and bars get out of tune with each other so the system becomes less efficient and we hear a sound that is both less harmonious and less fat sounding. This is a common enough scenario as stages sometimes get warm because of lights etc and studios often just heat up! Warmer temps mean that the resonators get too sharp in pitch for the bars.... bars go down and tubes go up.... so by raising the tubes up a little closer to the bottom of the bars we can actually make those tubes flatten in pitch to better match the bars "high temp" pitch. This is because of a kind of proximity effect. You may have noticed that the pitch of a tube will go down if you partially close the mouth of the tube..... having the tube mouth a little too close to the bar has this same effect... and in this case we are using this effect to our advantage.
Jim

Hi Herb.
Well ideally we try to match the internal diameter of the resonator as closely as possible to the width of the bar. The reason for this is that wider resonators take more energy away from a bar than smaller ones.... because of this they sound louder... but for less time. Wider bars also produce more energy than narrow ones though... this is why bars get wider as they get lower - to compensate for a human's reduced loudness perception at lower frequencies. So matching the resonator diameter to the bar width tends to keep the sustain and volume even and correct sounding over the instrument range.

That being said.... we certainly don't have to be too fussy about this. There are many reasons why a smaller tube might be used - most commonly because matching the INTERNAL diameter often means with thicker wall pipe, that the EXTERNAL diameter of a matching end cap ends up wider than the bar plus 1/2" gap between bars - meaning they don't fit in the space!

So using a smaller diameter tube is just fine. The difference will be not so noticeable at all with just 20% difference in diameter. A slight decrease in oomph from the sound if you really had to specify a difference... and perhaps a fraction more sustain if you really listened critically.

For this difference - don't even worry about the length change - it will be so small as to not worry. Technically you get the length from: 1/4 of the wavelength of the note minus 0.61R where R is the pipe radius. So you see the difference in diameter makes very little difference to the length in this case. In fact you will get a BIGGER difference because of changes in air temperature.

Really even with this calculation, I have found that you actually need to tune your resonators if you want them accurate - you can't just cut to calculated length. It will be very close, but tuning is better. There are just practical imperfections that affect the results. Try to tune in a room at a constant temperature that is what the instrument will be played at - I usually go for 21 degrees Celsius.

Hope this helps!
Jim

Hi Thomas
Most types of Eucalyptus generally are pretty dead sounding - very little for brightness. A lot of the "Zimbabwean style" instruments in Australia have bars made from "Australian Oak" - which is actually some form of Eucalyptus - although I forget the exact name. The reason is more that it is the best from what is commonly available in hardware stores - and a durable one at that. It certainly does not compare to proper tone woods though. I would be interested to hear about any results you get with the mesquite though.... I guess you can always use the waste shavings or any bars that don't turn out to add that smoke flavour to the BBQ anyway!
Jim

You pretty much have this correct actually!
Yeas you can take a random length - or guess - for your top and bottom note.... just as long as the material you use at that length is appropriate to the note you need to end up with - so it needs to be higher in pitch by a reasonably significant amount so you can lower it to pitch during the tuning process.

Yes - in your case take your white note bars only.... and go from your hypothetical 10" to 20" - divide by NINETEEN - not twenty - the first bar in the row is your starting bar. The result is 0.53" and is the graduation. So bar one in 10" - bar two is 20.53" bar three is 21.06" etc etc.

If you like you can also do this by physically getting the measurements. Take your top bar and bottom bar and place their ends against a flat wall or similar - space them apart by 18 bar widths (the number of bar that will be between. Then you can take a ruler or other straight edge and line it up from the end of one bar to the other. - Now at each bar width along the wall you can measure from that point to the ruler and you will have your bar length for that bar.

Well yes I would definitely recomend the 2024 in your situation then. As previously mentioned the "simple glock" guide is really aimed at a result probably similar to those less than awesome instruments you already have. Don't get me wrong it works fine - but its concept was as a simple and inexpensive instrument rather than a pro sounding one. The PV vibes is a different story and you can get a pro result there of course. If you want to get a truly pro glock sound - I would also reccomend slightly longer bar sizes - particularly in the top end - so you would have to work out a new "graduation" of bar lengths - and thicker stock also - go for at least 1/4" thick metal and anything up to 1/2".

Hi Neena
Well it all depends - strictly speaking a pro grade glock is generally made with steel bars rather than aluminium. There are aluminium gloacks made and in those cases it applies much the same as it would for a vibraphone. The SG simple glockenspiel mentioned in the makeamarimba.com website is exactly that - a simple instrument, and as such it does use aluminium bars - and what sort matters very little. If you want a pro glock though go with thicker steel bars.

For the vibes - well it is not quite true that the material is less critical - it is true that the bars do have resonators to amplify the sound - but because of the lower pitch range they also require it more. The fans will not really help the tone in any way - they just provide the vibrato effect.

For a vibraphone the T number - which is temper - can be important - but not as important as the actual alloy type itself. ANY alloty will make a tone - no doubt - but if you want a well known standard - go for 2024 T3 - this is what used to be called "Duralumin" in the old days in the aircraft industry, and it is the exact alloy that Musser have/do use for their vibraphones. A very common grade of aluminium in construction is 6061 - usually either T5 or T6. Both are ok - they are more corrosion resistant and heat tolerant than the 2024 - but not quite as strong and in my opinion the tone is not QUITE as good. The high copper content in 2024 is what provides the strength and sustain. In 6061, the primary alloying componants are silicone and magnesium I think it is - hence the resistance to corrosion and lower tensile strength..... the sustain you get there is more about the temper - a harder temper in that case is best.

Hope that helps!
Jim

It is alive if anyone has something on topic to say!
I myself will definitely reply to any post!

In general the 1/4" bars would be fine. For those specific plans - because the higher bars are quite short, you might find that you end up tuning the whole instrument an octave higher than you would with the thinner bars. That would actually bring it more into line with concert glock pitch range. technically thicker bars will always start higher in pitch than thinner ones, and technically you can lower them as much as you like by simply grinding away more material from the arch - but of course in practice there does come a point where it becomes difficult to lower the bar further without destroying the bar!!! But in general 1/4" thick bars would actually be better - this specific plan I feel you would either end up with an octave higher (which is fine) or you could change the bar dimensions so that your upper bars wer not so short. If you did that you would of course have to change the frame dimensions to suit.
Jim