"Bear" subwoofer
The subwoofer replay is unforgettable with its powerful and deep diving effect. With the popularity of home theaters and the continuous improvement of people's ability to appreciate audio and music, it seems that more and more fans are obsessed with subwoofer playback.
I still have an idle Hivi S10II speaker on hand. I used it to make an inverting subwoofer. After adjusting and listening, the subjective feeling is good. I would like to communicate with all the fans here.
The advantages of low-frequency replay of inverting speakers have been introduced in the article and will not be repeated here. The size of this cabinet is designed based on Hivi product data and with reference to Nanjing Liang Xiyue's SBD software. The focus is on improving the low-end frequency response, see Figure 1, and the relevant parameter curve is shown in Figure 2. The board is a 1.8cm thick medium density board (it is better if it is 2.2cm thick), with built-in ribs, 1cm thick sound-absorbing felt, the speaker opening is facing down, and the speaker panel is glued with two pieces of medium-density board plus nails. The foot height is 8 cm.
Because the ultra-low speakers will produce fast and powerful airflow movements, when using ordinary cylindrical resonance tubes, the sudden sudden compression and expansion of the airflow at both ends of the inlet and outlet will produce a blasting sound, which affects the low-frequency playback effect. The manufacturers all use the "double bell mouth" type resonance tube, which has a "transition zone" that is compressed and expanded when the airflow passes, thus overcoming the blasting sound of the airflow. However, it is difficult for amateur producers to find this kind of resonant tube. This box uses a simple manufacturing method and even achieves the effect of a professional manufacturer's "dual horn" resonant tube, as shown in Figure 3.
The box is simple in structure and easy to manufacture, but the process must be meticulous to ensure airtightness. According to the actual conditions, it can be designed to be active or passive (if it is active, the volume of the cabinet should be slightly increased). About the active system "Electronic News" and other publications are introduced, the producer can choose.
The speaker is placed on a wooden floor. If it is placed in a stone or carpet room, a medium-density board with the same area as the bottom should be placed between the box and the floor.
After the actual sound test, this box is placed in the author's 20 square meters living room, which is matched with a 6.5-inch bookshelf speaker, and is driven by an earthworm current mutual feedback DC power amplifier (150W) to play DVD discs. The effect is good (not good to use adjectives, fear Suspected of bragging). The local cost of this box is about 400 yuan. There are already 10-inch active subwoofers manufactured by the Huiwei factory on the market. The retail reference price is 1,400 yuan, which can be compared with it.
The efficiency of this box is high. Generally, the power amplifier of about 100W can be driven. This box is also suitable for other domestic brand high-quality bass units, but it should be appropriately adjusted according to its different technical parameters.
Finally, give the box a name-look at the stupid appearance, and call it "bear subwoofer"! 
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