Another try on bar suspension: foam rubber

After a year, the bar suspension using the insulation foam was again not really satisfying. The insulation foam still made a scraping noise when hit with a heavier mallet, and the sound was also a bit dull: fast deacay, no warm marimba sound.

So I tried a new material: foam rubber (Moosgummi in German). The result is simply great: longer decay, clearer sound, no more scraping noise on mallet impact. So if this stuff holds its form, this is really an alternative to drilling. I used a sheet of foam rubber that was 10mm thick, found it under the motorcycle-seat cushion category.

I've also rechecked the bars' tuning, and it was exactly as I measured it a year ago. I took the opportunity to put the fundamental into exact 443Hz based tuning, again applying a result from I. Bork's paper: The area where only the fundamental goes down is at 42% of the bar's lenght. A small incision here with a hand saw, at most 1mm deep, drops the fundamental by 20cent.

What still remains to be done are the resonator tubes. Let's see!

Update on bar suspension...

Just a short note here, no pics: I've removed all of the foam pads and renewed them, with the same material, but much thinner. I cut them on the sides to be less wide than the groove in the wood, to give the suspension a little free play. Also, the velcro was replaced with double sided tape.

The result: Much better = longer decay time, much clearer sound! The previous shape of the foam pads was too tight on the bars!

I wonder what one could do with a bunch of neodyme magnets...just thinking out loud here ;).

Sound samples!

Finally, the hard facts: What does it sound like? Well, not too bad, I'd say. But hear for yourself, but don't judge the "songs", that's just me hammering a bit on the poor marimba!

• Lower Octave
• Middle Octave 
• Upper Octave 
• Lowest and top octave together 

(The links go to my drop box. Press the download Button - you don't need to sign up for Dropbox. At the bottom of the sign up box, there's "No thanks, just download", press that, and the file gets downloaded to your computer. It's mp3, no tags.)

My impression while listening to this via speakers:

• The bars sound nice, woody, mostly in tune.
• There is still a hissing buzz audible from the foam pads under the bars.
• The attack noise of the mallet is quite strong; maybe I need to use softer foam pads for suspending the bars?
• It should do as a practice instrument.
• I wonder what adding resonators will do to the sound!

So long!

Update on bar suspension

Just a small note: The method of fixing the bars with a velcro strap was not very successful. The small play the velcro connection has made an very audible, high-pitched buzz.

So off came the velcro, and the foam pads are now fixed with double-sided adhesive tape. Also, most of the pads are now fixed with that tape on the wood's side.

Result: Much less buzz, though not completely gone; the bars seem to be vibrating better now, producing a mellow, warm sound.

Sound samples still to come, when playing technique is sufficient for a small demo ;).