Rebuild the door into a speaker...Speaker replacement [Why a professional can rely on]

There are many specialty stores called "car audio pro shops" in the world. If you go there, you can leave the upgrade of the car audio system with confidence. In this special feature, we explain the contents of the value of these specialty stores and how to utilize them.

Car doors are not in good acoustic condition!?

First of all, he explains various reasons why you can rely on a professional when replacing speakers. And this time, I will explain how professionals can "turn doors into speakers."

So far, we have introduced that there are some difficult processes in installing car speakers, but there is another very important process. It is to "adjust the acoustic condition inside the door". To tell the truth, this process is critical in the speaker installation work. Depending on whether or not this is done generously, the quality of the final sound will change.

Because the car speaker is a product only as a speaker unit, but in this state it is still a semi-finished product as a speaker. A speaker consists of a speaker unit and an enclosure (box). So, in car audio, the door of the car plays the role of the enclosure, but since the door is not made as an enclosure in the first place, it is necessary to make it into an enclosure.

In addition, this work is called "deadening". Or it is sometimes called "door tuning". This is because it is a physical sound tuning. In order to accomplish this, a wealth of experience, knowledge, and technology are required. Professionals have more than enough of them. So you can do this exactly.

What are the acoustic disadvantages of car doors?

Next, I will explain the situation of the car door. The doors aren't designed as enclosures, so acoustic conditions aren't great. There are mainly two bad points.

The first is that the inner iron plate is thin. Imagine a home speaker. Speakers are usually made of wood with some thickness, and are solidly built. This is because the speaker unit must be firmly fixed, and the sound energy emitted from the back side of the speaker must be securely contained inside. If the body is delicate, it cannot fulfill those roles.

On the other hand, even though car doors are made of iron, the iron is thin and not strong enough to be used as a speaker box. It is too weak to solidify the foothold of the speaker, and furthermore, it vibrates and emits sound due to the sound energy emitted from the back side of the speaker. By the way, it is impossible for the enclosure to resonate with home audio speakers. The sound generated by resonance definitely muddy the sound emitted from the speaker. Such things are never supposed to happen.

The second point that is not good for contention is "low airtightness". Some enclosures are not hermetically sealed, but if they are hermetically sealed, they require a high degree of sealing. This is because I want to completely shut in the back side sound. Here's why you might want to. When the sound inside the box leaks out, a phenomenon called "cancellation" occurs. The movement of the speaker diaphragm when viewed from the front and the back is the opposite relationship, and the sound waves have opposite waveforms. In this way, even if the sound is the same as heard by the ear, when the sounds that have opposite waveforms interfere with each other, they cancel each other out. We need to prevent this.

However, since the car door is not highly sealed, it tends to cancel more or less. Professionals change the situation inside the door to prevent this from happening as much as possible.

There are three main types of work performed in Deadening!

Next, let's take a look at how professionals turn car doors into speakers. The work that is done can be divided into three main steps. The first is ``attenuating the sound energy emitted from the back of the speaker'', the second is ``making the iron plate less likely to resonate'', and the third is ``improving the sealing of the door''. .

So, in "deadening", first, the sound energy emitted from the back side of the speaker is attenuated by absorbing and dispersing it using materials called sound absorbing and diffusing materials.

Then, a member called damping material is used to make the iron plate less likely to resonate. In addition, work such as closing the maintenance hole called "service hole" inside the door will make it difficult for the sound from the back side to reach the front side.

However, there are many differences in the details of these tasks for each car audio pro shop. Each shop carries out "deadening" according to its own theory, and prepares the acoustic condition inside the door.

It should be noted that the more you put in "Deadning", the more perfect it will be, but it's also ant to keep it light. If you do it generously, it will cost more, so if you start with a light content, you can focus your budget on the cost of the speaker. Ultimately, the better you do it, the better the quality of sound output and the better performance of the installed speaker unit, but it's okay to proceed step by step.

By the way, the professional will proceed the process efficiently even if you work step by step. He always chooses and implements the best possible method within a limited budget. In addition, it is easy to understand the effect of each work step by step. And you can enjoy the evolution of the sound. In that sense, there are advantages to taking steps. Please use it as a reference.

That's all for now. Next time I will continue to explain why professionals are reliable. stay tuned.

Shozo Ota | Writer After graduating from university, worked at a publishing company and built up a career as a magazine editor. After serving as editor-in-chief of car magazines, interior magazines, and car audio magazines, he retired from the company he worked for about 20 years and went freelance. Currently developing a wide range of writing activities centered on car audio, car navigation, and other car electronics. I am also working on music activities as my life work.