- Original article with photos here!
Sound design for large spaces is a pressing issue today: supermarkets and shopping centers, schools, hospitals, train stations, restaurants, and so on. There are two main solutions: public address systems and low-impedance systems. We'll discuss the former today, and more specifically, the DSPPA WL312B enclosure-mounted public address system.
We needed to provide sound for a small to medium-sized restaurant. The total area is no more than 200 m², with a standard layout: main dining room, bar counter, kitchen, bathroom, and utility rooms. Ceiling height is approximately 4 meters. There are 8-9 tables with 2-3-4 seats. In short, a typical setup.
There are several possible solutions, but we chose DSPPA equipment – simple, inexpensive, and effective. You can install built-in speakers, such as ceiling speakers. However, the sound quality requirements here are higher, so we choose the most suitable option – the DSPPA WL312B speaker system (the B at the end denotes the color – black; there are also white versions, which end with a W).
This speaker system is manufactured by DSPPA, a Chinese company founded in 1988 and working in the professional audio industry. They have a fairly wide range of products: mixers, amplifiers, microphones, speaker systems, and more.
70/100V public address systems are a specific type of audio equipment that is widely used for background sound and announcements in large rooms and open spaces. This equipment has its advantages, but it also has disadvantages.
Advantages of public address systems
- A simple wiring diagram, as all speakers are connected in parallel, significantly simplifies installation and calculations. There's no need to worry about impedance matching, as in low-impedance systems.
- High voltage (70 or 100 V) and low current allow audio signals to be transmitted over long distances (hundreds of meters or even kilometers) with minimal power loss and without the need for thick, expensive cable. This is ideal for supermarkets, shopping centers, stadiums, airports, and other large venues.
- Each speaker in the system has a built-in transformer with multiple taps. This allows you to select the required power for each individual speaker, independently of the others. For example, you can make the sound quieter in one room and louder in another simply by changing the tap on the transformer.
- A large number of speakers (up to hundreds) can be connected to a single amplifier, as long as their combined power does not exceed the amplifier's power. This makes the system easily scalable.
- Since all speakers are connected in parallel, the failure of one will not affect the others, making the system very reliable and stable.
Disadvantages of PA systems
- The main drawback is the presence of transformers. A transformer introduces additional distortion into the signal, which negatively impacts sound quality, especially in the low and high frequencies. Such systems are not suitable for reproducing high-quality music, where detail and a wide frequency range are important.
- PA systems are optimized for background music and voice announcements, where high volume is not required. If you plan to use the system for loud music, discos, or live performances, a low-impedance system would be preferable.
They come in boxes like these – note the logo… it’s not DSPPA – and that’s where things get confusing. It seems the manufacturer themselves got confused...
This is how everything is packaged inside – of course, it's missing our beloved bubble wrap... but oh well, we'll make do this time. The box contains two speakers with mounting brackets.
Unfortunately, their website has a wealth of information, but these speakers aren't listed... Although you can send them a request, and they'll provide the necessary information.
There are threaded holes on the top and bottom for attaching the mounting bracket. There are also threaded holes on the back panel. There's also a label and a terminal block, traditionally marked with red and black polarity.
These are small two-way speakers, measuring 242 x 182 x 162 mm. They're lightweight – 3 kilograms. The enclosure is made of plastic (ABS) – thick and durable... but it's plastic! The enclosure shape, viewed from above, is trapezoidal. The front side is covered with a fairly strong metal mesh (in our times, such anti-vandal measures are not superfluous). Under this grille, two drivers are visible: a 5-inch driver for low and midrange frequencies, and a 2-inch tweeter.
Removing the grille reveals a typical driver—it reproduces low and midrange frequencies. Then there's a dome tweeter and... a phased reflex tube (it adds low frequencies that a larger driver can't handle).
Since the manufacturer's official website remains silent, we search online and... find varying data, sometimes significantly different. For example, some indicate a frequency range of 75~20,000 Hz, others 75~18,000 Hz. Sound pressure is 104-105 dB. Sensitivity is 90 ±2 dB. Output power is 30 watts. Maximum peak power is 100 watts. Here you can see that this speaker is only slightly larger than the active Microlab speakers. B70 - read the review at the link.
The speaker cabinet consists of two halves, held together by six self-tapping screws. After removing them, we can disassemble the cabinet and examine the interior.
The cabinet is made of impact-resistant, ductile plastic. The joint fits well, with a step. We can also see reinforcing ribs inside the cabinet; we hope they will at least somehow dampen the resonant vibrations of the rather thin cabinet. The piece of synthetic padding is an attempt to increase the equivalent volume of the small cabinet, reducing the likelihood of cabinet resonances and standing waves (wavelength trickery).
And here is the transformer fed with 100 or 70 volts – this is a step-down transformer, which converts these high volts to low volts to prevent burning out the speaker's voice coils (which also degrades the sound quality).
Here we see two speakers, and they are quite good (by today's standards). I was particularly impressed by the high-frequency tweeter (I honestly expected to see a piezoelectric tweeter with a horn, but here it's a full-fledged dome tweeter) – unfortunately, the markings didn't make it into the photo... The woofer and midrange driver are marked D138-P820 YP73-56-56 on the end flange. The internet is silent about this driver, but now we've at least filled that gap a little. This is the midrange and low-frequency driver. Both drivers have an unshielded magnetic system.
The crossover or crossover network... yes, the most primitive solution is used here: a single metallized polypropylene film capacitor CBB22. 250V 475J – 4.7 µF. It blocks a high-frequency signal of a certain strength (which it can't handle), but at the same time, there's no choke (which would bypass the low-frequency path from the high-frequency signal), so... but it works! Incidentally, such systems are common in vaunted and expensive car audio systems.
We hope the bass reflex is designed correctly, and not just for show...
The DSPPA WL312B PA system is a completely justified choice with an excellent price/quality balance. It has a very wide range of applications. Of course, it lacks low frequencies, but this equipment isn't intended for music lovers. For all other applications, it's sufficient.
Considering the ease of installation and setup, scalability is certainly a significant plus! Furthermore, equipment such as a mixer amplifier, such as the DSPPA MA6200U (we'll write about it soon), is essential.
However, if high-quality sound is essential, low-impedance systems are, of course, preferable.
***
如今，大型空间的音响设计迫在眉睫：超市、购物中心、学校、医院、火车站、餐厅等等。主要有两种解决方案：公共广播系统和低阻抗系统。今天我们将讨论前者，更具体地说，是 DSPPA WL312B 箱式公共广播系统。
挑战
我们需要为一家中小型餐厅提供音响服务。餐厅总面积不超过 200 平方米，标准布局：主餐厅、吧台、厨房、卫生间和杂物间。天花板高度约为 4 米。餐厅内设有 8-9 张餐桌，每张餐桌有 2-3-4 个座位。简而言之，这是一个典型的布局。
有几种可行的解决方案，但我们选择了 DSPPA 设备——简单、经济、高效。您可以安装内置扬声器，例如吸顶扬声器。然而，这里对音质的要求更高，所以我们选择了最合适的选择——DSPPA WL312B 扬声器系统（末尾的“B”表示颜色——黑色；也有白色版本，以“W”结尾）。
这款扬声器系统由 DSPPA 制造，这是一家成立于 1988 年的中国公司，专注于专业音频行业。他们的产品范围相当广泛：调音台、功放、麦克风、扬声器系统等等。
简单理论
70/100V 公共广播系统是一种特殊的音频设备，广泛用于大型房间和开放空间的背景声音和广播。这种设备有其优点，但也有缺点。
公共广播系统的优点
- 由于所有扬声器均并联连接，接线图简洁，显著简化了安装和计算。无需像低阻抗系统那样担心阻抗匹配问题。
- 高电压（70 或 100 V）和低电流使音频信号能够以最小的功率损耗进行长距离（数百米甚至数千米）传输，无需使用粗而昂贵的电缆。这非常适合超市、购物中心、体育场、机场和其他大型场所。
- 系统中的每个扬声器都内置一个多抽头变压器。这样，您可以为每个扬声器单独选择所需的功率，而不受其他扬声器的影响。例如，只需更改变压器上的抽头，即可在一个房间内降低音量，在另一个房间内提高音量。
- 只要扬声器的总功率不超过放大器的功率，就可以将大量扬声器（最多数百个）连接到单个放大器。这使得系统易于扩展。
- 由于所有扬声器均并联连接，因此一个扬声器的故障不会影响其他扬声器，从而使系统非常可靠稳定。
PA 系统的缺点
- 主要缺点在于变压器的存在。变压器会给信号带来额外的失真，从而对音质产生负面影响，尤其是在低频和高频部分。这类系统不适合重现高品质音乐，因为这类音乐注重细节和宽广的频率范围。
- PA 系统针对背景音乐和语音播报进行了优化，这些场合不需要很大的音量。如果您计划将系统用于嘈杂的音乐、迪斯科舞厅或现场表演，则低阻抗系统是更好的选择。
DSPPA WL312B 扬声器系统评测
它们采用类似这样的包装盒包装——注意标志……这不是 DSPPA——这就是容易让人混淆的地方。看来制造商自己也搞混了……
所有东西都是这样包装的——当然，少了我们最爱的气泡膜……不过，算了，这次就凑合着用吧。盒子里装着两个带安装支架的扬声器。
可惜的是，他们的网站上有很多信息，但没有列出这些扬声器……不过你可以向他们发送请求，他们会提供必要的信息。
顶部和底部都有用于安装安装支架的螺纹孔。后面板上也有螺纹孔。还有一个标签和一个接线端子，传统上用红色和黑色标记极性。
这是一款小型两分频扬声器，尺寸为 242 x 182 x 162 毫米。它们很轻，只有 3 公斤。外壳由塑料 (ABS) 制成——厚实耐用……但它是塑料！从上方看，外壳呈梯形。正面覆盖着一层相当坚固的金属网（在我们这个时代，这种防破坏措施并非多余）。在这个格栅下方，可以看到两个单元：一个5英寸单元，用于中低频，以及一个2英寸高音单元。
拆下格栅后，可以看到一个典型的单元——它能重现中低频。然后是一个球顶高音单元和一个……相位反射管（它能增加大型单元无法处理的低频）。
DSPPA WL312B 规格
由于制造商的官方网站一直没有公布，我们在网上搜索……发现各种数据，有时甚至相差甚远。例如，有些显示频率范围为 75~20,000 Hz，而有些则为 75~18,000 Hz。声压为 104-105 dB。灵敏度为 90 ± 2 dB。输出功率为 30 瓦。最大峰值功率为 100 瓦。
从这里可以看出，这款音箱仅比有源麦博音箱 B70 略大。——点击链接阅读评测。
DSPPA WL312B扬声器系统 - 拆卸
音箱由两半组成，由六颗自攻螺钉固定在一起。拆下螺钉后，我们可以拆开音箱并检查内部结构。
音箱采用耐冲击、韧性好的塑料制成。连接处衔接良好，略有台阶。我们还可以看到音箱内部有加强筋；我们希望它们至少能在某种程度上减弱较薄音箱的共振。这块合成填充物是为了增加小音箱的等效体积，降低音箱共振和驻波（波长欺骗）的可能性。
这是供电电压为 100 伏或 70 伏的变压器——这是一个降压变压器，它将高压转换为低压，以防止烧坏扬声器的音圈（烧坏音圈也会降低音质）。
这里我们看到了两个扬声器，它们相当不错（以今天的标准来看）。我对高频高音单元印象尤为深刻（说实话，我原本以为会看到一个带号角的压电高音单元，但这里却是一个功能齐全的球顶高音单元）——可惜的是，照片里没有标注……低音单元和中音单元的末端法兰上标注着 D138-P820 YP73-56-56。网上没有关于这个单元的任何信息，但现在我们至少稍微填补了一点空白。这是中音和低频单元。两个单元都采用非屏蔽磁路系统。
分频器或分频网络……是的，这里使用了最原始的解决方案：单个金属化聚丙烯薄膜电容器 CBB22。250V 475J – 4.7 µF。它可以阻挡一定强度的高频信号（它无法处理），但
时没有扼流圈（可以绕过高频信号的低频路径），所以……但它确实有效！顺便说一句，这类系统在那些备受推崇且价格不菲的汽车音响系统中很常见。
我们希望低音反射设计得当，而不是为了装点门面……
总结
DSPPA WL312B 扩声系统是一款物超所值的选择，性价比极佳。它应用范围非常广泛。当然，它缺乏低频，但这款设备并非专为音乐爱好者设计。对于其他所有应用来说，它已经足够了。
考虑到安装和设置的便捷性，可扩展性无疑是一大优势！此外，像 DSPPA MA6200U 这样的混音放大器（我们很快会介绍）也是必不可少的。
然而，如果追求高品质音质，低阻抗系统当然是首选。
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