Company Address: P.O. Box 30315, New York, N.Y. 10011.
Personal involvement in high-fidelity sound reproduction has diminished over the years. Most audio components have become so sophisticated, with such things as microprocessors, memories, digital signal processors, and infrared remote controls, that even if a listener had the desire to put in time and effort to improve the quality of his system, he would find it difficult to know where to begin. That's too bad, because audio used to be more fun. It has changed from a hobby, where one could actively participate in designing and building audio components and reap the reward of personal satisfaction, to a more passive recreational pursuit. Some people may complain about the lack of science in many o the "tweaks" we hear about, and certainly there are many silly things being promoted, but the reason for their popularity is at least partly due to the fact that many audiophiles want to be actively involved in the pursuit of good sound reproduction.
One of the last components of high fidelity sound reproduction that is still available for personal input is the loud speaker system. If you have an interest in getting actively involved in audio, a great way is modifying an inexpensive one. If you have any trepidations, consider the SoundAid Kit.
The SoundAid Kit, which costs $30 contains all the materials and instructions necessary to guide you through some simple modifications intended to improve the sound quality of a pair of Realistic Minimus 7 loudspeakers. The Minimus 7 has enjoyed a long life compared to other speaker models offered by Radio Shack. It is listed on page 19 of the 1992 Radio Shack catalog and is reasonably priced at $49.95 apiece; have seen it in the company's monthly flyer for as little as $29.95. The Minimus 7 is an 8-ohm, two-way system with a 1-inch dome tweeter and a 4-inch woofer. The enclosure, a die casting with a wall mounting bracket on the rear, measures 7 1/16 inches high x 4 7/16 inches wide x 4 5/16 inches deep. The system weighs 4 1/2 pounds and has a perforated metal grille. Optional mounting brackets are available for $17.95 per pair.
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KIT EVALUATION
GENERAL COMMENTS: A good way to get involved in improving the sound of a loudspeaker system with minimum expenditure while learning something at the same time.
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The SoundAid Kit includes eight sheets of damping material that mea sure 7 3/4 inches long, 3/4 inch wide, and about 3/16 inch thick; two 4.7-µF, 150-V Solen capacitors; a small plastic jar (not shown) containing a white liquid to coat the 4-inch bass cone, and a brush to perform this operation. The instructions are clear and the steps easily performed. A Phillips-head screwdriver is needed to remove the bass driver, and a soldering iron and some solder are needed to remove the original gray capacitor and replace it with the new Solen capacitor. Needle-nose pliers might be handy for removing the capacitor leads but aren't essential.
The first step is to remove the grille, which can be pried off easily because it is held in place by small pieces of sticky damping material. Next, the bass driver is removed to give access to the inside of the cabinet. After re moving the acoustic material, you apply the slabs of damping material to the inside walls of the cabinet by merely pressing them in place; they are sticky and will adhere quite easily. The next step is the replacement of the capacitor, which is a reasonably easy task. After this is finished, the acoustic material is inserted back into the cabinet, and the woofer is replaced. The last step is to coat the woofer cone with the white liquid. If you want to experiment, you can put on a light coating, listen to the results, and then put on another coating after the first coat has dried. This will allow you to hear the change more gradually.
I asked a number of people to listen and write down their comments while comparing an unmodified Minimus 7 versus a SoundAid modified one. Since I had previously determined that the lowest bass was unaffected by the modification, I saved time by using program material that would allow the actual differences to be heard more clearly. I played recordings that featured brass, strings, and voice. I also used the interstation noise from an FM tuner, because it is an excellent way to hear subtle colorations very easily.
Some of the listeners' comments about the sound of the unmodified Minimus 7 were: "Sharper sounding," "more nasal," "unable to listen to it for long periods," "shrill," and "more forward." Comments about the SoundAid modified Minimus 7 included: "Smoother," "more natural," "tolerable," "clearer on voice," and "more definition in middle register." From these comments it is clear that the SoundAid modification improved the sound quality of the Realistic Minimus 7.
I also made a number of technical measurements on the modified and unmodified systems, and the results tended to verify that the SoundAid Kit really does do some good things. The response of the bass driver is better between 1 and 2 kHz because there is less cone breakup. The Solen capacitor improves the sound between 3 and 5 kHz by increasing the tweeter output in this range and making the sound cleaner. The increased tweeter output does increase the level of the baffle reflections in this range, however. You might want to experiment with using some felt or foam material around the tweeter. Because the grille causes some loss of high frequencies above 9 kHz, the sound might be even better with the grille removed if you've added the felt or foam.
I recommend the SoundAid Kit to anyone who has a desire to get more involved in the fun part of audio but feels cautious, inhibited, or even timid about trying something as daring as modifying a speaker cabinet or painting a woofer cone. Try it. Let's bring some fun back to our audio hobby. By the way, as an added incentive to buying the Minimus 7s and modifying them with the SoundAid Kit, these systems make very good rear-channel loud speakers in surround installations.
-Edward M. Long
(adapted from Audio magazine, Jul. 1992)
Also see:
Win Research SM-10 Speaker (Auricle) (July 1992)
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