Many netizens have some idle digital products at home, many of which come with a "sound-emitting" function, that is, they are integrated with "speakers (horns)". So how can we DIY a speaker system relying on these small horns?

In simple terms, our daily speakers only require an amplifier, a horn, and a sound source (usually a mobile phone or computer) to produce sound. The speaker box can be customized based on the size and related parameters of the speaker (horn) through channels like Taobao.

Because whether the sound is pleasant or not, and how the final presentation turns out, involves multiple factors, it falls into the category of "esoteric" and "price发烧 with no upper limit", so this article only briefly mentions the idea and does not provide "professional" guidance or "professional jargon", but only speaks in "plain language". For example, the professional volume of the box needs to be calculated through software with corresponding parameters, rather than just taking a box of a certain size, drilling a hole, and installing the horn to use directly. For us ordinary users, it is too cumbersome, so let's just "roughly estimate" based on feeling.

[1] Front end: Sound source

The sound source, as the name suggests, is the source of the sound signal, which can be a mobile phone, a computer, or various specialized players, including repeaters and radios with sound output.

The quality of the sound source (which ultimately depends on the "sound card") directly determines the audio quality level of the entire system. Therefore, friends who have certain requirements for sound may not be satisfied with the integrated sound card on the computer motherboard, and there are differences in the sound quality levels of different mobile phones.

ALC897 is currently the most common mainstream 7.1 channel high-definition sound card on computer motherboards. Others like ALC662 are early (now almost extinct) low-end motherboards that would use 5.1 channel entry-level high-definition sound cards for listening, while ALC888, ALC1150, and ALC1220 all belong to high-end models in integrated sound cards.**Middle Section: Power Amplifier (Amplifier)**

What is a "power amplifier"? A power amplifier is essentially an amplifier that increases the power of an audio signal.

Due to the very low energy of the audio signals directly output from our mobile phones or computers, without a "power amplifier," it is likely that the speakers will not be driven, and thus we would not be able to hear any sound. The power amplifier holds a very high position in the audio system, playing a decisive role in the fidelity of signal amplification (of course, the sound source and speakers also have a significant impact). A poor-quality power amplifier may ultimately output noticeable electrical noise or other interference. Audiophiles may invest tens of thousands, hundreds of thousands, or even millions to acquire a high-quality power amplifier.

The various speakers we commonly encounter, including very low-end desktop speakers and campus broadcasting systems, actually have integrated (or independently set) power amplifiers inside (or outside) them (which is why they can clearly specify their power), with the only differences being the power level and the amplification conversion effect (sound quality). Students who have worked in broadcasting stations should know that campus broadcasting requires a large number of high-power amplifiers to drive the speakers spread throughout the entire campus. In-ear headphones, depending on specific circumstances, will have signal amplification circuits integrated internally by the manufacturer at the time of production.

The power of our everyday home speakers is generally not high. For residents in ordinary residential buildings, choosing speakers with a power range of 5W to 20W is more than sufficient; playing them loudly is simply a nuisance to others. When we DIY audio systems, we can definitely consider these small power amplifier boards with power levels in the tens of watts, and if they come with Bluetooth functionality, they can wirelessly connect with mobile phones.

*Note: There is no very clear connection between speaker power and "loudness," it's just a matter of the upper limit.

The power of the power amplifier does not need to perfectly match the power of the speaker (loudspeaker). It is fine if it is slightly higher or lower. From the perspective of compatibility, it is generally recommended that the power amplifier's power be slightly greater than the speaker's rated power, as being too much can easily "burn out the speaker." For users who are just "playing around," you don't even need to overly consider the "impedance" (typical speakers and amplifiers will have impedance parameters such as 2Ω, 4Ω, 8Ω, 16Ω, etc.).**Section 3: The Speaker (Loudspeaker)**

The component in a conventional speaker system that produces sound is called a "speaker," commonly referred to as a "loudspeaker" (henceforth referred to as "loudspeaker"). They generally look like the image below. Most are "circular," but they can also come in other shapes (tweeters can have various shapes, while mid-range and bass speakers are typically round). The diaphragm material of the loudspeaker can be made of paper, polypropylene (PP), wool, woven fabric, and so on. This is why you might notice differences in the color or style of the diaphragm across different brands of loudspeakers. However, low-end products often use paper diaphragms, which are easy to drive and cost-effective, but the sound quality may be quite average.

Since the final sound reproduction relies on the loudspeaker, it is equally crucial.

For instance, the mid-range unit of the top-tier optional audio system "Bowers & Wilkins" for BMW (the first in the above image) is exquisitely designed and has a substantial weight. It features a silver woven diaphragm that resembles hemp when viewed up close, and under light, it exhibits a honeycomb-like translucent glow. The silver surface is chosen to maximize the reflective effect when paired with a luminous cover. Previously, Harman Kardon (for BMW) used materials like PP or wool for their loudspeakers, but it seems they have switched to paper diaphragms now.

Loudspeakers can be broadly categorized by function into bass speakers (drivers), mid-range speakers (drivers), and tweeters (drivers); if further细分, there are also super tweeters (drivers), mid-high speakers (drivers), mid-low speakers (drivers), subwoofers (drivers), coaxial speakers, and so on.

A simple description of their roles: Tweeters produce a crisp (clear) sound, better reproducing the effects of pianos or other high-end instruments, but excessively high treble can be harsh to the ears; mid-range speakers enrich the human voice, as most instruments are concentrated in the mid-frequency range, but too much mid-range can lead to a muddy and unclear sound (many people mistakenly increase the treble at this point, resulting in a final sound that is both muddled and harsh); bass speakers add more dynamism to the sound, especially needed for rock music and drum beats. Bass is extremely challenging to reproduce well—poor bass lacks depth and sounds like "Dong Dong Dong," while good bass is elastic, sounding like "Duang Duang Duang." Excessive bass can be overwhelming and uncomfortable.

The loudspeakers in our everyday radios and tape recorders are generally "full-range speakers" (I don't think they deserve this title), as a single speaker has to do three jobs, and the result is that it does none of them well, just producing sound for the sake of it.

The simplest, though not entirely accurate, way to determine the function of a loudspeaker is by looking at its size (excluding miscellaneous desktop speakers). Tweeters have a high diaphragm frequency and are therefore made smaller, often located at the top, typically ranging from 1 to 2 inches; bass speakers need to move a large amount of air, so their diaphragms are relatively larger, usually between 5 to 12 inches, but many desktop speakers have quite compact bass drivers; mid-range speakers can vary in size, generally ranging from 3 to 6 inches, and are commonly positioned below the tweeters.Commonly known speaker brands include Harman/Kardon, BOSE, Dynaudio, Focal, Bowers & Wilkins (B&W), Sony, Yamaha, Bang & Olufsen (B&O), Burmester, and Mark Levinson, among others.

**4** Active/Passive Speakers (Loudspeakers)

In our daily lives, we also come across terms like "active speakers" and "passive speakers."

So-called active speakers refer to a category of products that have an integrated amplifier board (module) inside the speaker. They are commonly seen in home audio equipment. We simply need to connect them to a power source and then plug the audio cable into our computer or mobile phone, and they will produce sound normally.

So-called passive speakers refer to a category of products that do not have an integrated amplifier inside. They are commonly seen in campus public address systems, large stage loudspeakers, conference room speaker systems, and speaker systems built by audiophiles themselves. The input ports of passive speakers are generally reserved for connecting the positive and negative terminals of an amplifier, and as long as the amplifier has sufficient power and enough output interfaces, we can continue to add speakers on top.Passive speakers can be found on platforms like Xianyu, where many high-quality passive speakers are available at relatively low prices in the secondary market. By adding an amplifier later, they can be used normally. Additionally, a standalone speaker can be considered a passive speaker, which can be directly connected to an amplifier board or a standalone amplifier for use.

Where to find speakers?

You can dismantle speakers from unused radios, tape recorders, or various outdated devices with built-in sound functions at home and use them with a small amplifier; you can also directly search for various independent speakers on Xianyu, with prices ranging from a few yuan to several thousand.

The power of radio speakers is generally very low, so you must be cautious when connecting them to an amplifier board to avoid burning out due to excessive volume. These speakers often have detailed parameter markings, such as 2W/8Ω.

With the rise of the car audio modification industry, you might find many affordable good items by searching for car speakers on Xianyu. Taking the widely modified BMW as an example (people sell the original car speakers after modification), the price of the BMW stereo speakers' mid-range speakers (4-inch/4.5-inch mid-range, generally 10W power) varies from 15 to 100 yuan each, and the corresponding silk diaphragm tweeters (10W-25W power) are also priced similarly at around 30-50 yuan each. As we all know, the world-class Bowers & Wilkins speakers are expensive, costing tens of thousands of yuan, but Bowers & Wilkins has cooperated with car brands such as BMW, Ferrari, Volvo, McLaren, and Maserati, so you can find a large number of Bowers & Wilkins speakers from dismantled cars on Xianyu (beware of extremely low prices, as they are likely to be counterfeits, which are rampant).

No matter what kind of speaker you buy, as long as you have a small amplifier board, you can simply connect it with wires (for universal speakers, you can connect the wires randomly, but if it's a car dismantled speaker, be sure to use car-specific wires, which usually cost a few yuan each), and you can start playing sound. If you have purchased the 2.0 amplifier board mentioned earlier for around 20 yuan, it is recommended to pair one tweeter with one mid-bass unit per channel, so that all three frequency ranges can be covered.Because standalone bass units are often quite large (the picture above shows a BMW 8-inch seat bass, 4.5-inch midrange, and 1.5-inch tweeter), they are difficult to daisy chain and challenging to pair with enclosures (you can opt for smaller bass units), so you might consider purchasing a tweeter + midrange and then additionally pairing it with a passive subwoofer. Furthermore, purchasing an amplifier board that can be connected solely to the subwoofer can also achieve perfect full-range output.

If you wish to create a complete speaker system, you can buy corresponding DIY enclosures on Taobao, with prices ranging from tens to hundreds of yuan. DIY speakers typically have dual driver positions, usually featuring 1 tweeter + 1 mid-woofer, unless an additional subwoofer is also paired.

Special Note:

If you are genuinely interested in purchasing salvaged Bowers & Wilkins or other high-end audio units, or even considering upgrading your BMW with B&W speakers, be particularly aware that the current price for an authentic B&W midrange (green label, large B&W, silver woven cone/75W8Ω) is approximately 400 yuan per unit (the 4-inch and 4.5-inch sizes differ only in the outer diameter, with the power rating being the same); the price for the standard B&W in the new 5 series (yellow label, silver or black woven cone/50W8Ω) is lower, at 250 yuan per unit. Additionally, the yellow label metal tweeters (1.5-inch) are around 150 yuan per unit (these are generally considered to be BMW's rebranded Harman tweeters), the green label crystal tweeters (1.5-inch) are around 300 yuan per unit; the top-tier diamond tweeters (1.5-inch) are around 2000 yuan per unit. If you opt for salvaged B&W speakers from supercars like McLaren or Maserati, the prices will be slightly higher, typically around 500 yuan per unit, and they are not interchangeable between vehicles. Lower-priced options are often counterfeit.

Regardless, with a DIY setup like this, coupled with a subwoofer, you can experience Bowers & Wilkins for around a thousand yuan. Midranges, tweeters, and bass can be mixed and matched as long as they are compatible, such as pairing B&W midranges with silk dome tweeters. However, it is recommended to mix and match speakers from the same car brand, as they typically have compatible connectors, and tweeters from the same brand can often be daisy-chained onto the midrange units.

The reason for using BMW as an example for car speakers is that BMW's internal combustion engine sound systems have seen almost no significant changes in nearly 20 years, resulting in a vast supply of salvaged speakers. Moreover, most midranges can be directly daisy-chained with their own tweeters (as shown in the picture above, with dual ports for direct connection). Generally, BMW speakers can also be identified by the color of the sticker on the back: white label for standard stereo (midranges generally cannot be daisy-chained with tweeters), blue label for high fidelity, yellow label for Harman, and green label for B&W (assuming they are not counterfeit). However, currently, BMW also likes to mix high fidelity midranges with Harman tweeters in the same sound system, such as the so-called 12-speaker Harman in the new low-spec X5L and the new 5 series, which is essentially the old high fidelity system with Harman tweeter heads replaced.