A Study on Hilt Sound Resonance

[Sunrider]

This is a thread to condense the information I have discovered in testing of sound resonance in saber hilts.

First I will explain resonance and sound waves, then describe an optimized single speaker setup, then a two speaker solution. Then I will list detailed information and data. Hopefully someone will sticky this so it can be found easily.

What is resonance?

For our purposes it is the ability of the hilt cylinder to amplify speaker output by physical connection to the speaker much like a horn. With only a mouthpiece of a horn there is no resonance. With mouthpiece plus horn we have resonance and sound is louder.

Here is a diagram that shows how different wavelengths propagate differently in the same space.



Of course the main limitation with our sabers is the small size. It's difficult to propagate low tones.

The length of a 60hz wave (which is about the frequency of a saber idle hum) is 19 feet. The length of a 15khz wave (which is about the highest frequency of a saber sound) is 9 inches.

Fortunately we don't need that much length to get good results.

Single speaker resonance chamber rule of thumb is 1.5 times as long as the width of the speaker.

Because the different frequencies we hear are of different wavelengths or differ in size this makes it difficult for a single speaker setup to perform well at all frequencies.

When the speaker is pointed straight out the pommel vent. There is good upper frequency resonance but the lower is lost due to not enough length for the lower longer waves.

When the speaker is pointed inside the hilt. This is often referred to as reverse sound. The lower frequencies perform better but the upper range is easily baffled by internal components. One way to improve the upper frequencies with this setup is make holes along the length of the hilt to release upper tones before they are attenuated by stuff inside.

A major limitation to a single speaker setup is one speaker has a hard time making a wide range of sounds at the same time. This is why we see professional speakers with 2,3, and 4 different size speakers in one box. Sound quality is improved by dividing the different ranges of sound between speakers.

To overcome some of these limitations here is an example of a two speaker setup. The sound quality of this setup was the best found during testing.

Two speaker module







module installed in pommel






The speakers point in opposite directions. The bigger one points to the inside of the hilt from the pommel. The smaller one points out the vent in the pommel. This gives the bigger speaker a longer chamber for lower tones and a small chamber is big enough for higher tones.

A 4.7uf ceramic capacitor is soldered on the positive leg of the bigger speaker then connected to the tweeter. This is needed to only pass higher frequencies to the smaller speaker. Making it only produce higher frequencies. I used a surface mount 0805 size part .

A ceramic cap will pass only higher frequencies to the smaller speaker.

An inductor will pass only lower frequencies to a speaker.

This in turn improves the performance of the speakers.

Here is a good site that will elaborate and let you play around with numbers. Depending on speaker specs you can tailor a setup to your needs.

http://www.bcae1.com/passxovr.htm

It is important that air can flow from the speaker area to vent holes some where down the hilt. The further down the holes along the hilt the better. Only a small path is needed for enough air flow but the better the flow, and the longer the path, the better the low tones will be.

So what this gives you is optimized sound from both ends. A long chamber for low tones and a small chamber is enough for the tweeter. Also more audio input can be applied without distortion.

It is important to mount the speaker firmly and seal the seam around the big speaker for best performance.

Many hours went into testing different configurations. What you see are a 36mm 2w speaker with shielded magnet and a 16mm sony mp3 cell phone speaker JB welded to the back.
Note: this pommel has larger I.D. than mhs parts.

The smaller speaker has a small box around it with a port on the side so it is better protected from the bigger speaker pressures nearby.

The magnets from the different speakers should be separated by non magnetic material. I used a small aluminum square.

The two speaker setup is probably not worth doing unless you are using a high end sound board mostly due to the quality of the sound samples from the low end boards. Also this does not necessarily make a saber louder but more of an improvement on sound quality.

I would make a movie but it would not convey how it sounds.

I will tell you that during testing of 7 different small speakers with ESB I heard stuff that I normally don't.



Here is a link to the thread that the initial round of testing was done. If you want detailed information on how much a resonance chamber can amplify sound from a speaker there is lots of info in there.


http://forums.thecustomsabershop.com...ead.php?t=9608


Hopefully this will give some insight on resonance in sabers.

If there is some thing more to add or explore or questions let me know.

SR