Alteration of 35AC1 into a subwoofer. The art of audio

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Converting 35AC1 into a subwoofer

The art of audio

The characteristics of the 30GD1 dynamic head, which is used in the very first, legendary modification of the S-90, are quite high. This speaker has only one major drawback - low sensitivity, but there are a lot of small ones. However, the availability and cheapness of this speaker system and its variants make it possible, after a slight alteration, to use it as a good subwoofer.

To increase the return at low frequencies, the volume of the system case must be slightly reduced, which will lead to the appearance of a "hump" at frequencies of 40 - 45 Hz. Since the subwoofer only reproduces frequencies below 100 Hz, by slightly increasing the frequency response unevenness (compared to the original version), bass reproduction can be improved. Figure 1 shows the theoretical frequency response of such an acoustic system.

Converting 35AC1 into a subwoofer
Theoretical frequency response of the acoustic system

The subwoofer can be used in two versions: passive and active. In the first, the subwoofer, together with the left and right channel speakers (satellites), is connected to the existing amplifier through a passive crossover filter, the design of which is given below.

The second option requires a separate amplifier and active filter. An active subwoofer is more convenient to set up, since you can quickly change the reproducible frequency band. Structurally, the subwoofer can be made traditionally, with radiation forward, or it can be done with radiation "to the floor". To do this, on the front panel (it will become the bottom one), it is necessary to install legs 50 - 70 mm long, preferably height-adjustable. In this case, the acoustic design turns from a bass-reflex into a bandpass one, so it will be necessary to adjust the volume of the resonant chamber that has turned out in front of the speaker.

The traditional version requires more accuracy in work, since it is almost impossible to eliminate traces of alteration and other surface defects. After processing, the case remains only to be painted or pasted over with a film that imitates valuable wood species.

In the second option, the subwoofer can be disguised as furniture. To do this, the case will have to be covered with artificial leather or fabric. Under tight-fitting, the side walls of the case must first be pasted over with thin foam rubber - this will smooth out sharp corners and surface defects. You can attach a pillow or tabletop to the top (in the past - the back) wall, turning the "bedside table" into an "ottoman" or "coffee table". On fig. 2 shows the necessary changes in the hull design.

Converting 35AC1 into a subwoofer
Necessary changes in the hull design

The dismantling sequence is as follows:

Remove the decorative overlay along with the treble and midrange heads. Cut the wiring harness from the heads. They remove the plastic box that covered the rear of the midrange head .;
Remove the woofer. Cut wires. Cotton wool is removed.;
Remove the filter switches. Remove the chassis with filters and remove it through the hole for the bass head .;
Carefully dismantle the phase inverter tunnel .;
Then proceed to the alteration of the body. The body is marked for trimming. The upper part is cut around the perimeter with a saw on a tree with a small tooth (so that there are no chips). The back wall of the case - chipboard, side - chipboard and veneer, front - plywood. Sawdust is collected - they will come in handy. Clean the edges along the cut line on the main part of the body .;
The sawn off top is disassembled into parts with light blows of a hammer. On the left and right sides of the separated top panel, a chisel is used to select (more precisely, “gnaw out”) a shelf 10 mm wide for half the thickness of the panel. It would be better to make a mustache connection, but in artisanal conditions it is difficult to process the side panels of the case. The panel must be adjusted so that it closes the case tightly, but without force. The presence of small gaps somewhere is not a problem.

An insert is cut out of the trim of the front panel to decorate the upper part of the hole for the box. If the amplifier will not be installed directly into the subwoofer cabinet, the hole will have to be completely closed with a plywood insert or plug, fitting it into place. It is possible that it is not planned to use a standard switch (but it can be used), then the hole for it must be closed in the same way.

The top panel and insert are attached to the body with EAF epoxy glue (inside) and a few small nails (outside). Reinforcing bars are installed along the perimeter of the panel from the inside of the case. They can be borrowed from the "remains" of the top.

The case is dried in a vertical position ("upside down") for at least 12 hours. So that the glue does not spread through the cracks, you need to caulk them with cotton wool soaked in the same glue. After the glue has dried, you can start sealing the seams from the outside. The body is laid on its side, the edges of the triangular groove are closed with adhesive tape. To seal the seam, the same epoxy glue mixed with sawdust is used.

After the glue dries "to the touch" (after about 8 - 10 hours), the process is repeated for the other side. Then the case is placed "on its back" and the seams around the perimeter of the inserts and the front panel are poured (as a rule, there are more than enough of them). At the same time, you can fill the corners and joints of the rear panel from the inside with either pure glue or mixed with sawdust. Despite the relatively small thickness, the shortened back panel has sufficient rigidity and does not require additional reinforcement.

The resulting monster is set aside for at least three days, so that the resin finally hardens. To cover the internal surfaces of the housing, "polymer-bitumen mastic" or a similar composition is used. This process can be combined with the final curing of the resin. While the resin hardens and the mastic dries, you can do other things. If the subwoofer is with a built-in amplifier, you can use the box that covered the midrange head to mount it.

The middle is cut out of it, and the halves are welded with a soldering iron. It is possible to fuse several pieces of wire across the seam or to fuse an overlay from scraps of the same box. When installing the box, it is necessary to ensure its tight fit to the body. It remains to return the phase inverter to its rightful place, also taking care of the tightness of the joint with the case. For these purposes, any sealant is suitable, even plasticine.

Depending on the chosen design option, the body is trimmed. Puttied seams are processed "on a plane" with a file and sandpaper. Further - a matter of taste and possibilities.

After finishing the case, you can proceed with the installation of the system. For a passive connection option, a crossover filter is required (Fig. 3). It can be placed in the subwoofer cabinet. To turn off the subwoofer, switch SA1 is used. A regular S-90 switch or a toggle switch is suitable for this role. Coils are wound on mandrels with a diameter of 35 mm, winding length 25 mm. They contain 630 turns of PEV-2 wire with a diameter of 1,2 mm. The required wire length is about 150 m, the resistance of the coil to direct current is 2,2 ohms. To reduce it, you can use a ferromagnetic core, but these coils, of course, will be different.

Converting 35AC1 into a subwoofer
Passive crossover circuit

Publication: www.bluesmobil.com/shikhman

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Apple MacBook Pro is the best Windows laptop 02.05.2013

The 13-inch MacBook Pro has proven to be the most reliable laptop to run and work with the Windows operating system. The most reliable vendor was Dell, whose laptops took five places in the top ten at once.

Apple MacBook Pro is the best laptop for Microsoft Windows operating system. This is the conclusion reached by Soluto, who tested the mid-13 2012-inch model along with nine other computers. The MacBook Pro was voted the best because Windows installed on it had fewer crashes, freezes, and blue screens of death compared to other laptops. The version of Windows is not specified on which the tests were conducted, the researchers did not specify.

Also tested were Acer Aspire E1-571, Dell XPS 13, Dell Vostro 3560, Acer Aspire V3-771, Apple MacBook Pro 15 Retina, Dell Inspiron 14z, Dell Latitude E5530, Dell Vostro 3460 and Lenovo Thinkpad X1 Carbon - these laptops ranked from second to tenth, respectively. According to tests, the number of crashes in Windows installed on the MacBook Pro 13 was 0,88 times per week, the number of freezes was 1,06 times per week, while the "blue screen of death" occurred 0,01 times per week. The total score of the car was 1,05 (the lower the value, the better the result).

The Acer Aspire E1-571, which came in second, had 0,74 crashes, 0,40 freezes, and 0,06 blue screens of death each week. The total score is 1,12.

The last 1th place Lenovo Thinkpad X1,69 Carbon had 1,34 crashes, 0,09 freezes and 3,20 blue screens of death each week. The total score was XNUMX.

Why the MacBook Pro has become the most reliable Windows-based PC is easy to explain, and Soluto's analysts make no secret of it. The fact is that on the MacBook Pro, the Windows operating system was installed in its purest form, without third-party software that laptop vendors clutter Windows with. This is reflected in Soluto's statistics: if the MacBook Pro had 60 background processes, then the Acer Aspire E1-571 (second place) had 66 processes, and the Lenovo Thinkpad X1 Carbon (tenth place) had 85 processes altogether.

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