Miata Mailing List: December 1997, Message #212
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From: 	MHathaway@IVSinc.com

Subject: Radio mod.  for the Do-It-Yourselfers

Date: 	Tue, 2 Dec 1997 17:08:21 +0000



	Howdy Gang,



	As many are aware, there are certain modifications to the stock

radio (older ones, anyway) which can vastly improve the headrest speaker

sound.  This mod. was brought to our attention by Jeff Anderson (perhaps

others presented it earlier, but I am unaware of their work).  He has

been offering his services to make this modification for a modest fee,

which is reasonable.  My question is this:  has anyone else (or Jeff

himself, if he is willing to divulge his secrets...) messed around with

the stock radio amp section, to determine what has to be changed to

effect the HR speaker improvement.  I ask for the benefit of the

tinkerers who would like to make THIS upgrade and are technically able

to (I suspect there are many of us on this list), and would also enjoy

the feeling of "doing-it-themselves".



	I have taken a look at mine (specifically the amp section, which

hangs off the back end of the radio), and it appears that there are

several capacitors which, if changed to caps of smaller size, would

allow more bass to get to the HR speakers.  These caps are in parallel

to the speakers, and go to ground on their other ends.  Unfortunately,

they are not clearly marked as to capacitance, and there seem to be

identical ones on the speaker lines going to the front speakers.  This

puzzles me, since I would expect to find smaller ones on the front

speaker lines, since they take greater bass levels.  I suppose that

these caps might not be the filter caps, and that this filtering occurs

further upstream, before the chip that is the last major component

before the signal leaves the amp.  



	Any thoughts?



	Mac

	'90 MBRG