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HASIB'S ARTICLES AND AUDIO PROJECT REVIEWS
SURROUND CHANNEL SPEAKER Introduction This speaker project was done for my Pro-Logic system that need surround channels to feed the surround information's mainly for movies. Before this I don’t have strong willing to get another two speaker boxes in my listening room since my previous system is stereo. For surround channel, it needs the drivers will blend seamlessly (timber matched) with my main speakers and center channel. This speaker project using 4” full range driver. Just one driver. No tweeter driver available on this project because Pro-Logic surround sound information has limited bandwidth – only 100-Hz to 7000-Hz. The Driver For full range driver I use is 4” Sony’s driver that rated about 30 watt maximum input power and 4-ohm impedance. I need two of them since DPL need two surround channels (It is actually mono but acted like stereo). I don’t have parameters such as Qtc, Vas (Small-Thiele parameters) and so on for the drivers, but I have measured it free-air frequency response – quiet good. Frequency response is 85-Hz to 6500-Hz (-3dB). The upper frequency is limited to 6500-Hz but I don’t worry so much. The Box I just make simple box (sealed box). External dimensions are by 27-cm high, 16-cm wide and 23-cm deep. Internal volume is about 0.2838 cubic feet or 8.03 liters. After determined the space that soaked by the driver, fiberglass and speaker terminal, final enclosure volume is 0.21 cubic feet or 7.08 liters. The panels use 11-mm plywood that attached together using nails and good quality wood contact adhesive. I drill a hole about 10-cm in diameter for full range driver and 7-cm x 8-cm for speaker terminal cup. I use lots of wood glue inside the box to seal the joints to keep it air-tight after I mount the driver and speaker terminal cup. The box needs wood filler to eliminate rough joints (panels joints). After the filing was done I use medium grit sandpaper to remove unwanted filler and make the box has smooth surface. For finishes – I just paint it black using wood paint. I need three coats to make it appear good. Just simple solution. I want to make this project as easy and low cost as I can. Using fancy finishes will make the overall cost higher but it depends on your taste – it is personal. Before mounting the driver and speaker terminal cup I insert some fiberglass in the box. I use thumbtacks and stapler to hold it. The driver and speaker terminal cup need a sealant to make it airtight. I don’t use speaker/terminal gasket but foamed double-side masking tape. Smooth move huh. After everything aligned correctly I drill holes for driver/speaker terminal cup and use wood screws to mount them. Just don’t forget to solder a wire between the driver and it’s terminal. That’s it. Simple isn’t it? The Grill I make simple grill for the two speakers. The depth of the grill is about 2 cm and I use curve wood at the side, which looks solid. For attaching the black cloth I use stapler, care is needed here to avoid misalign. It is much simpler if you have a friend to hold it before you stapled it. The Result I can say much, it sound good, informative and has enough SPL for surround channel. Also it can do music well too for Hall mode. Honestly the surround speaker sound closely matched to main and center speaker on test tone sequence. Completed project picture
Fig1 - Surround Channel Speaker Well, excuse me – just one picture and sorry about the picture resolution too. Maybe someday I will supply new picture(s). Muhammad Hasib bin Md. Nor July 2001 Any Comment And Question Email to : hasib_tangkak@yahoo.com
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