fjr48 Posted February 23, 2012 Share Posted February 23, 2012 I need to replace the rear speakers in my 1990 Reatta coupe. I don't understand electronics at all, so I would like to ask if using rear speakers that are four ohm resistance will ruin the stock radio. Thank you Link to comment Share on other sites More sharing options...
NCReatta Posted February 23, 2012 Share Posted February 23, 2012 I've used these in a couple Reattas now. Work great. No problems. Direct match up for your '90 too. Amazon.com: Infinity Kappa 6929i 2-Way 6" x 9" Car Speaker - Pair: Car Electronics Link to comment Share on other sites More sharing options...
D-a-n-i-e-l Posted February 23, 2012 Share Posted February 23, 2012 As long as you stay 4out ohm and above you should not have any issue. Link to comment Share on other sites More sharing options...
wws944 Posted February 23, 2012 Share Posted February 23, 2012 The front speaker system is rated at 4 ohm impedance (not DC resistance). So the built-in amplifiers are already capable of driving a lower impedance load.To get slightly technical, impedance seen by the stereo depends on the frequency of the signal. There are impedance peaks and dips - especially in the bass region below 200 hz. So one would want to know the natural resonance frequency, the Fs, of the speaker, how wide that resonance is (Qs), and how it is matched to the enclosure, the 10 cu ft trunk, resonance point(s) and Q, to find the points(s) of lowest impedance. I suspect that GM speced 10 ohm speakers to avoid any impedance drop issues with resonances in the trunk - where much deeper bass can be emitted than from the doors. Or maybe they just had a huge warehouse full of 10 ohm speakers they needed to get rid of... Link to comment Share on other sites More sharing options...
fjr48 Posted February 23, 2012 Author Share Posted February 23, 2012 Thanks to all for the quick and helpful replies. The 4 ohm speakers are much easier to find than the 10 ohms ones. WWS944, the explanation about the amount of bass from the rear speakers, and why was really interesting.I always get excellent help here, this is a great forum ! Link to comment Share on other sites More sharing options...
Guest Recian Posted February 24, 2012 Share Posted February 24, 2012 That could explain why after i put an amplifier in it messed up my old radio. I've been thinking of taking my sub out and putting 6x9 conversion with some good bass speakers. Link to comment Share on other sites More sharing options...
Rawja Posted February 24, 2012 Share Posted February 24, 2012 I switched to 6X9's in the back on my old '89 and now on my '88. Big improvement.Presently running these Infinity Kappa 3-ways in the back (With matching rounds up front):http://www.amazon.com/Infinity-Kappa-693-9i-speaker-3-way/dp/B001HL0UAG/ref=sr_1_3?ie=UTF8&qid=1330117467&sr=8-32 ohm resistance, BTW. The product literature claims the lower impedance results in more volume. Seat of the pants, seems to be true. It seems like i gots way more volume and bass than ever before.I listen to techno-type crap mostly so I like a lot of bass and sparkling highs at significant volume. Left the door tweeters in as well for extra brightness and directionality. Link to comment Share on other sites More sharing options...
Guest Mc_Reatta Posted February 24, 2012 Share Posted February 24, 2012 Rawja, just make sure your amplifier is rated to support the 2 ohm impedance speakers. Most auto amps are anymore, but some may not be. Puts a lot more stress on the output amplifier stages, and will do damage if not designed for it. Also make sure when you mix and match speakers you maintain the impedance value you need. Dual coil speakers and separate bass and treble drivers can get you in trouble if you don't pay attention. Link to comment Share on other sites More sharing options...
Rawja Posted February 25, 2012 Share Posted February 25, 2012 Stock '89 Reatta head unit. (actually the same one swapped from first car to present) 7 years driving 4 ohm all 'round and about 2 years now driving the 2 ohms. No issues. Link to comment Share on other sites More sharing options...
wws944 Posted February 25, 2012 Share Posted February 25, 2012 If I had a '88-'89, I'd swap in the 6x9 boxes as well. Given comparable quality speakers, the 6x9s could be worth an extra half octave of bass compared to a 6.5".As far as driving speakers that are a 2 ohm load, I won't hazard an opinion on how well the Delco amplifiers in our Reattas will hold up. We would have to know which transistors/ICs they used in the output circuitry, details of the circuitry in general, how much heat sinking is there, etc. It may be ok at normal listening levels. But take your car to one of those "db drag races", run it continuously at high volume with the bass turned way up, and you may find otherwise. Link to comment Share on other sites More sharing options...
Rawja Posted February 25, 2012 Share Posted February 25, 2012 ....run it continuously at high volume with the bass turned way up, and you may find otherwise.Only speaking from my experience, so far so good. :cool: Link to comment Share on other sites More sharing options...
Guest blue72beetle Posted February 25, 2012 Share Posted February 25, 2012 run it continuously at high volume with the bass turned way up, and you may find otherwise.WHAT'D YOU SAY?! Link to comment Share on other sites More sharing options...
J3Studio Posted February 25, 2012 Share Posted February 25, 2012 To get slightly technical, impedance seen by the stereo depends on the frequency of the signal. There are impedance peaks and dips - especially in the bass region below 200 hz. So one would want to know the natural resonance frequency, the Fs, of the speaker, how wide that resonance is (Qs), and how it is matched to the enclosure, the 10 cu ft trunk, resonance point(s) and Q, to find the points(s) of lowest impedance. I suspect that GM speced 10 ohm speakers to avoid any impedance drop issues with resonances in the trunk - where much deeper bass can be emitted than from the doors. Or maybe they just had a huge warehouse full of 10 ohm speakers they needed to get rid of ...Nice explanation! Link to comment Share on other sites More sharing options...
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