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Door Speakers


padgett

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a) Barney's instructions in the FAQ were right on with one minor exception, my '88 had screws that took an 8mm socket, not philips. Would take 15 minutes except that nothing takes me 15 minutes.<P>B) The $12.99 speakers at Pep Boyz etc that say "OEM replacement" are not. sound quality is poor and muddy even to my hearing impaired ears. They also lacked spacer rings or grilles and magnet was about half the size of the OEM ones (cone on original was completely separated around edges). Am still amazed at how good the sound is in the new GM cars I get from Avis - what is the secret ?)<P>c) door retainer thingies are not the yellow ones with ruffles, are black and strong and on metal braces not sunk in carboard. Did not even need my fastener tool.<P>d) Need to be careful removing the plastic covers over the screw at each end of the grab strap - are fragile.<P>BTW is it proper for the volume to drop very noticably when switching from radio to tape ?<p>[ 09-03-2001: Message edited by: padgett ]

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i would try the GM originals next...my '90 Riviera and '88 Reatta both have the same speakers and i made the mistake of replacing the fronts with R. Shack's in the Reatta. The R. Shack speakers are 8 ohm instead of 4 which is a mismatch right out of the box. The Riviera door panels took the yellow things...8 in each door....20 to a packet (GM part # 20*10161510...a little better than $1 ea.) The Reatta black ones, as you said appeared to be designed to be reusable except that i had to re-epoxy one of the "U" brackets to the door panel and tie wrap the separation on another. In audio amps the optimum sound is achieved by proper matching of the design. In other words if the amp output is 4 ohms then an 8 ohm speaker will draw more than designed current...and will surely distort the intended frequency response and RMS distortion levels and will probably half the capability of the power output transistors. On the other hand a 2 ohm set-up would double the output wattage and cause excessive power output transistor temperatures. Never run the amp (channel) with no load as this will eventually burn out the power transistors (unless the input(volume) is off) sometimes even with protection circuitry. The speakers GM uses are 4 ohm 4-1/4" (measured from inside cone) acoustic suspended woofers crossed over with a tweeter to handle "highs". Because they are acoustic suspended (meaning they are mounted with foam around the cone) the speaker excursion is greatly extended and as a result lower true bass is achieved without the distortion created when the speaker flexes from ridged mounting to the frame. This also creates easier control of the "free-air resonance" which is the frequency that the speaker inherently wants to spike or boom at causing unwanted muddiness. i believe that GM has taken basic audio requirements and very effectively designed a system that is vehical specific...that is to say that the equalization, wattage efficiency(amp power output to "db" pressure created from speaker power absorbion), and the cross-over woofer-tweeter combo all contribute to a very good sounding system out of the box. Outside this environment though....it's garbage. <BR>The receiver section is usually a higher pre-amp gain because they can get away with it and maintain specs...and most AM & FM program material is compressed anyway so there's no danger of damaging transit response clipping (distortion). The tape player on the other hand is bound by the individuals program material and lower pre-amp output to the power amp maintains a lower distortion rate and wider frequency response within specs. That is to say if the specs specify 30 watts RMS (continuous) from 20hz - 20,000hz with + or - 3db deviation....then it better be that or the feds will nail you for lying (they can cheat by narrowing the hz or increasing the +/- db adver. specs). Plus the line level output of the pre-amp section reflexs a lower level than the taped program material...because it was calibrated for optimum signal to noise ratio, causing a difference in levels between the receiver and tape player. i'll bet that some CD players don't have this problem because it is easier to maintain specifications. For you tape player people i would recommend the Radio Shack tape head demagnetizer (44-1165B) about 12 bucks and tape head cleaner (44-1113D) and dual-tipped cleaning sticks (44-1093) and i guarantee your player will sound like new again (louder and with more frequency response).

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