The Soul of a Music Box- The Comb

The Soul of a Music Box - The Comb (Vibration Plate)

The Comb is the Key Component in Generating the Great Sound Quality

The supplier of our comb is Kyooh Precision Industry Co., Ltd., which is located in Taichung, Taiwan. This company has manufactured the combs for various types of music box for more than 40 years. Their technique in producing the comb is originated from the Japanese music box brand, Sankyo. Not only the steel comes from Japan’s unique steel material, the use of tiny and thin damper on each tooth of the comb also comes from Japan. The tiny damper is pasted on the back side of the comb. You may not know that this thin damper plays an important role in determining the sound quality of a music box.

The comb of Muro Box was an upgraded version based on the existing comb produced in Kyooh Precision Industry Co., Ltd. Our team has spent a lot of time refining this thin damper in order to enhance its durability without sacrificing its great sound quality. This story presents what we have invested in improving this tiny but vital component.

The Feature and Limitation of a Music Box

Have you wondered why music boxes always play slow melodies? Is it because the slow melodies sound more romantic or it is simply due to its mechanical design’s limitation?

I think the real reason is that the comb of a music box has its limitation in mechanical design, so it is not suitable for playing fast melodies that repeat plucking the same notes, which will generate a sharp clicking sound. Therefore, when a melody has to pluck the identical note many times, its tempo needs to be adjusted to slow it down in order to make it produce pleasant sound.

Let’s use a simple test with a rule to explain its mechanical design’s limitations. If you keep a ruler’s one side attached to the table’s edge and use your finger to pluck the other side that is hanging in the air. Then, when you get a pen to use its tip to touch the vibrating ruler, you will hear a sharp collision sound. This sound is like the noise you will hear in a music box when it plucks one note continuously at a fast speed. This noise comes from the next pin to touch the vibrating tooth of the comb before its vibration ends from the previous plucking.

The function of the damper on the comb is to work as a cushion to reduce the noise from the pin’s collision on the vibrating tooth of the comb.

In other musical instruments, for example, a piano has its own unique Damper Pedal to serve the similar function. It is responsible for the end of a note, to make it a smooth sound.

However, because the size of a music box is smaller and simpler, there is no perfect solution for its damper design yet. If you are interested in learning more about how a damper works in a piano to maintain its sustaining sound effect, please watch the video below.

The Limitation of the Damper

If the damper solves the clicking sound problem, why do music boxes still play slow melodies? It is because the damper only alleviates the problem. For example, with a damper, it may reduce the shortest repeating interval of notes from 2 seconds to 1 second, but it is still not enough for a music composer’s needs.

The damper is subject to wearing. The most fragile part of the music box is the damper. A Sankyo branded paper strip music box has an official life span of 400 hours due to the damper start wearing. The music quality dropped after the wearing happened.

The following picture is a close-up shot of the damper from the music box brand “NICOLE FRÈRES”. The metal string at the tip of the comb is the damper. From the photo, we can see that many of the dampers are damaged. The durability is a great challenge in music box’s damper design.

Can We Fix the Problem Without Using Dampers?

Ok, if the damper is an issue, are there any other solutions that can be used instead? I believe the answer is Yes. For example, if production cost is not an issue, the bigger and more expensive music boxes have dual-disk or dual-comb design, and I think it is aimed for the problem we are discussing. To see a music box with multiple combs in performance, please watch the following video: https://youtu.be/AUmz4GnxuB4

It is an intuition that double the comb can double the volume, however the true benefits are far beyond that. For my understanding, the major goals for the multiple combs are for two purposes: consecutive notes and sublime harmony.

It is related to consecutive notes because the following note can be plucked from a different pin/comb, and it avoids the problem of the following pins from collision on the previous vibrating metal tooth

However, Muro Box N20 cannot use this design, simply because of the cost. We hope everyone can enjoy Muro Box easily if they love music boxes. We don’t want it only to be affordable for limited wealthy people.

Sublime Harmony

Sublime harmony is not related to the problem of noise in fast melodies that repeat plucking the same notes. Nevertheless, it is an interesting phenomenon so we want to share it with you.

Luxurious music box had the feeling of the “vibration” of the tones that oscillated in the space. This is not just because it has a better quality wood case, it is mostly due to the use of two teeth that are not exactly tuned at the same frequency but are slightly out of tune a bit. More accurately speaking, two teeth are different in exactly 14 cents (100 cents = 1 semitone). If you are interested in this topic, please take a look at the following video. Our future N40 model will use this technique in our comb design. (Thanks to Siegfried Pattyn for providing this great suggestion.)

The Challenge of Muro Box

We have set the goal of supporting the fastest 4 consecutive notes per second by consulting the music arranger. This speed is not adequate for heavy metal rock, nevertheless it is enough for most of the pop songs.

Even if we set a moderate goal of music speed, it is still extremely hard to reach this target, and is way beyond our initial imagination.

There is no turning back, we have to move on. Because the consecutive notes noise has a great impact on the experience of music listening, we have people leave comments in our YouTube video questioning if the music box is broken to have this noise.

Following is a video clip of our earlier prototype playing music. It didn’t have the damp yet to reduce the consecutive notes noise.

In the beginning, we misunderstood that the cause of the noise came from some unknown defects of the electromagnet, and we made an assumption that it will disappear naturally after we optimize the structure of the cylinder. Unfortunately, the problem finally breaks out in our last stage of the mass production, which caught us off guard and greatly impacted the product delivery.

That was devastating to our team. We have spent years on making a programmable cylinder for Muro Box, now we have to make the comb on our own, too? If the problem cannot be solved, then we have to reduce the max speed of the melody, then this music box makes no difference to the model made 100 years ago. What should we do?

How Muro Box Solves the Problem

We start from modifying the shape of the original damper, and hope to make it more effective. Soon we realize that if it is possible by just tweaking the shape, it will be done already by the original designer. It is just a waste of time.

We then have a second thought on the material of the damper. The original damper is made of PET. How about changing the material to something with better vibration absorption? Unfortunately, our comb’s supplier won’t be able to support us if we modify the production processes. We had to find a new material supplier to make our own sample for testing.

With the help of a die-cutting factory in China, we designed a new mold and started to test various kinds of plastic material. PVC, Mylar, PC, PEEK…, we have evaluated and tested everything they have in house and nothing worked. Fracture, wearing, deformation, and weak bonding, all kinds of issues occurred and more than you can imagine. We have exhausted every option and the result is worse than the original PET. We have to believe the original designer’s wisdom that they already found the best solution. We still have to use PET.

Then we googled all available PET suppliers, finally we contacted a supplier in China who has a thicker PET film that we requested. Finally, we are back on track on the damper testing.

Finally the First Good News

“It Works!”

Finally, after we switched to the thicker PET, we reduced the noise from the consecutive notes to not be noticeable. We felt so happy, and we immediately sent the sample to our comb’s supplier, Kyooh Precision Industry Co., Ltd., to try it again in their assembly line. The damper is bonded to the comb using UV resin, and we are going to use the thicker PET in their UV resin bonding procedure.

Unfortunately, we received a call from Kyooh that the damper we chose had become deformed due to the heat from the UV lamp. We shared the bad news to the supplier in China for possible alternatives, and surprisingly, they suggested their competitor’s product to us.

The Next Miracle Happened

Through their recommendation, finally we met the famous Japanese PET film supplier, Kimoto.

During the first business meeting, they were very confused about why a music box manufacturer needed their support. PET film, due to its wear resistance characteristic, is frequently used in the LCD Panel and Touch Panel. These areas are totally different from what a music box manufacturer may use.

However, they still generously support us with enough High Temperature PET raw films for us to continue on the damper experiment.

Hard Lesson Again

Finally, after endless going back and forth between all sorts of problems, Muro Box finally embraced its first official shipping date (This is our first ZecZec crowdfunding in Taiwan in 2018 before the 2020 Indiegogo campaign). Just a few days later, the first report from our customer brought the bad news. The damper fell off from the tooth of the comb. Our UV resin cannot subtend the extended music playing usage scenario in Muro Box.

We immediately stopped the product shipping, and put the Muro Box back to the stress test table to fix the quality issue. Our new stress test standard is to continue playing the Muro Box for 16 days, 24 hours per day. This length of stress test time was suggested by Kyooh.

We started experimenting with all kinds of industrial adhesive gum. From Super Glue, Epoxy to UV resin, we tested every possible kind of glue we can get. However, the working condition of the damper is extremely hard. All kinds of extreme conditions, like tiny contact surfaces for the glue, excessive duration of vibration of the comb and rubbing by the cylinder’s pins. The most difficult part is the joint of dissimilar materials of plastic and metal. All methods we tested were failed.

Everyone in our team was depressed because we have faced years of difficulties and setbacks, and even in the last stage before shipping we still ran into such a challenge.

Reborn

We already spent a few months on the damper. We started from the original design of Sankyo, replaced it with various materials, and still unfortunately did not reach our acceptable quality standard. We finally understood that we have to think out of the box to get through this nightmare. We decided to abandon the existing design and started a new design from scratch.

We gave up using plastic to absorb the vibration and used a stainless steel damper to increase the durability instead. We added an extra layer of soft material between the damper and comb to further reduce the force and reduce the noise.

We ask Kyooh to conduct the durability test and sound test on our new damper, to ensure that on top of the extended life time, we still maintain the sound quality of the comb. At the same time, Kyooh developed a new tuning method for this specific comb of the Muro Box N20.

Epilogue

We are fortunate to receive encouragement and support from many people, and endless support from our key suppliers. We redefined the manufacturing process and material of the damper to make it beyond the capability of the existing one. We have patents of the new damper design in R.O.C (M594783) and China (202020038579.1).

Although only a part of the damper’s development process is documented here, we believe that you should be able to realize how much effort is required to design a good damper to resolve the noise from consecutive notes.

This is why the Muro Box is such a valuable possession. It is a gift from so many people’s endless effort, and only comes to life after countless miracles happen.