Recent Posts

21

General Discussion / Partially Completed Vibraphone, parts for sale - make me an offer

« Last post by TomD on August 06, 2015, 12:06:30 PM »

We've gotten halfway through this project and my son has lost interest. 
http://www.buildavibraphone.com/get_vibraphone_plans.html

Would like to find a good home with someone interested in completing it. The wood frame is built, the PVC tubes are cut and tuned, and the aluminum metal bars are rough cut (but not tuned). I have most (if not all) of the remaining parts. We were doing a high quality job, over $1000 in parts cost. Willing to accept any reasonable offer - I need to get this stuff out of my garage.

I'm in the San Francisco Bay area. 

22

General Discussion / Vibraphone fans

« Last post by geo.jenner on June 16, 2013, 03:26:51 PM »

Some experiences from building a vibraphone.

To make the fan we used a 4l can of olive oil (Spanish, naturalmente).  Make sure you finish the oil first.

One 4l can had plenty of material to make all the fans. Also looks coo to see the olives going around.

To shape the fans I didn't use the method in the instructions.  I got two blocks of wood and drilled a 6mm hole through the join, so when you separate them there is a groove on the top of the block that fits the fan axle.  You then place a fan blank over the groove, push on small piece of 6mm steel rod, then bend the wings back flat with the wood.

I don't know if the surface density of the steel is more or less than the aluminium sheet Jim uses, but the tremolo effect it gives is deep enough that my kid says it sounds like a vibraphone (I myself have never even seen one before - the kid is the percussionist)

George

23

General Discussion / Vibraphone Motors

« Last post by geo.jenner on June 16, 2013, 03:18:55 PM »

Well we've finished our vibraphone and it's pretty great

But I can't find a good motor.  I've got probably the same motor as Jim ($21 from Jaycar) and it's too noisy.  Seriously I need to knock about 30dB off.  The instructions point to the forum to share ideas, so here I am.

Has anyone got alternatives.  I went to the wreckers yesterday to look at wiper motors, as they use helical worm gears, which are apparently a lot quieter.  The bloke wanted more than I was willing to pay ($35 to $100, depending on the model).  I'd rather get http://www.motiondynamics.com.au/worm-drive-motor-12v-50w-45-65-rpm-5-29nm-torque.html new for $51.

I've asked the diy robot people, and all their gear motors are similarly noisy, but they suggested an AC motor from a turntable.  Interesting idea by I don't know where to start on that one. Might need a double pulley system to get the speed reduction.

In the meantime I might try to wrap what we've got in wavebar or something like that.

Any more ideas?  I'm desperate for my kid to play jazz with me, but he insists he needs the vibrato.

Thanks
George

24

Instrument RESONATORS & tuning / Re: Resonator Length

« Last post by Jim McCarthy on May 18, 2013, 12:31:02 AM »

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

25

Instrument RESONATORS & tuning / Re: Resonator Length

« Last post by Herb on May 17, 2013, 03:38:58 PM »

Thanks that helped, the other thing I would like to know, does the temperature affect the bars and the resonator's equally, in other words do they stay in tune to each other. 

26

Instrument RESONATORS & tuning / Re: Resonator Length

« Last post by Jim McCarthy on May 13, 2013, 01:33:55 AM »

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

27

Instrument RESONATORS & tuning / Resonator Length

« Last post by Herb on May 11, 2013, 06:31:32 AM »

Hi Jim,
Is it possible to use a Resonator with a smaller diameter (say 40mm instead of 50mm). Is there a formula to work out the rough length to get close to the right pitch?  Does it make any difference to the sound?

28

Instrument BARS & tuning / Re: Timber for marimba bars

« Last post by Jim McCarthy on April 30, 2013, 06:21:42 AM »

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

29

Instrument BARS & tuning / Re: Timber for marimba bars

« Last post by Thomas on April 29, 2013, 06:42:29 AM »

I have access to two types of eucalyptus where I live. The wood is well seasoned (air dried over two years)
1) is E. robusta (red gum)
2) is E. globulus (blue gum)
Jim, have you any experience with these species? or know of anyone who has.
A third option I have is mesquite (Prosopis pallida) which is what I am most likely to begin with. I'll be happy to share my results, just wondering if you have prior experience with any of these.

30

Instrument BARS & tuning / Re: New graduation of bar lengths

« Last post by Jim McCarthy on April 09, 2013, 09:32:47 AM »

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.