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Looking for an inexpensive solution to improve upon the Bose Premium in my brand new (less than 200 miles) Black Touring MDX, I decided to replace the four door speakers with Infinity 652I speakers. I'm not handy so I decided to purchase/install the speakers at a nearby Circuit City. However, the Audio Manager refused to change the speakers, citing the impedance mismatch - which he said might make worsen the sound - or even damage the headunit. Is damage to the headunit a possibility? Thanks for any advice.
 

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willbrook said:
Looking for an inexpensive solution to improve upon the Bose Premium in my brand new (less than 200 miles) Black Touring MDX, I decided to replace the four door speakers with Infinity 652I speakers. I'm not handy so I decided to purchase/install the speakers at a nearby Circuit City. However, the Audio Manager refused to change the speakers, citing the impedance mismatch - which he said might make worsen the sound - or even damage the headunit. Is damage to the headunit a possibility? Thanks for any advice.
I've change my fronts to Infinities and no problem, and shortly i'll be doing the rears too. Alot of postings on this site, search on infinity, and you will see no one has ever reported a problem. Some sites, such at crutchfield, don't even show the infinity speakers as fitting in the doors.....so far the fit is perfect. On the front speakers, i didnt even have to cut off the little plastic centering nubs for the bose speakers, the back of the infinity has an indent that fit right over them. you don't need circuit city, handy or not, at least for the fronts, they are cake to install. just get an adapter plug at circuit city, the covr pulls off easily and a couple of screws is all that holds the speaker in place. go for it:2:
 

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edepa - Thanks for the encouragement - Did you also install the 200hz bass filter - or is it not necessary? What's an 'adapter plug? Thanks
 

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The circuit city manager does not understand how speaker resistance (ohm rating) interacts with the amplifier. In simple terms, if you replace a 2ohm speaker with a 4 ohm speaker, the 4 ohm speaker will suck less power and make less sound at the same volume setting. This also means the amplifier doesn't work as hard (less amplification). Not only would there be no chance of the speakers damaging the system, it would go the other way in terms of inducing less electronic stress on the system than previously.

Other people have posted that they have not had any problems, but I'm trying to explain the theory behind it. Replacing a 75 watt light bulb with a 60 watt bulb can't possibly harm the lighting fixture.
 

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Great explanation TCMB.....Doesn't Circuit City realize they are loosing money with people who obviously do not know enough about car stereo to handle these situation??
 

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slackass said:
Great explanation TCMB.....Doesn't Circuit City realize they are loosing money with people who obviously do not know enough about car stereo to handle these situation??
You are saying a mouthful, but only scratching the surface when it comes to all the products out there poorly represented by salespeople. That's why it's so important for consumers to educate themselves.
 

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Could not agree more DaleB. I do not claim to know half there is to know about car audio. But, I can do nothing but smile when I go into Best Buy or Circuit City or others and they start sharing there vast knowledge with me and I know that they have no idea what they are talking about. I really should not pick but, give me a break. The poor guy who does not know any better is trusting his or her $20,000 or more vehicle with these people.
 

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Changing to Infinity speakers probably will not damage the head unit, and many have done it successfully.

The circuit city manager however has some valid points. An amplifier is designed for a given impedance (or range of impedance). Decreasing the impedance on most amps is dangerous and can lead to overheating. Increasing the impedance normally does not hurt anything, but can influence sound as the manager stated. The output characteristics will change with the impedance, and things like distortion, frequency response can be affected. On the older Nissan Bose amps, putting normal 4 ohm speakers in place of the bose resulted in near complete loss of the bass. The amp was not deigned to be 4 ohm stable, and frequency response was all over the board at 4 ohms

Above said, aftermarket 4 ohms appear to be so much better than the stock Bose that it is a huge improvement! I just did not want Circuit City to take an unfair bashing on this concern (they are somewhat correct in this case). That is rare enough that we should give some credit.
 

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Calculating System Impedance

This link http://www.dbdrive.net/techsupport/speakerimpedance.htm has a good discussion about speaker configurations with regard to impedance matching. I don't know anything about the product line but they give a good basic explaination.

Another comment about about speaker replacement is ensure you have the correct polarity. I've read that some people are not getting good bass respose from their replacement subwoofer. I know from experience with the 3 subs in my home theater setup that a significant amount of sound is lost if polarity is reveresed. The sub will "thump" in the wrong direction. (not a good thing with a 1000 watt sub)

I've been thinking of replacing my speakers with 2 sets of the Polk EX3560 component speakers and using the included tweeters to replace the Bose tweeters and twiddler but I can't find specific info on the Bose tweeters/twiddler. Anyone know?

I am also considering either the Alpine MRP-F320 40W x 4 + 120W x 1 Amp ($199) or the Alpine MRV-F450 50W x 4 + 200W x1 Amp ($499) from Crutchfield. Does anyone have feedback on these amps?

Thanks,
Bnuke

03 Redrock Touring/Navi
 

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Discussion Starter #11
speaker replacement

Thanks to all, especially TCMB, for the explanation regarding impedance - I really appreciate forum members taking the time to respond to my query. The Circuit City Manager probably meant well, but he did come across as a 'know it all' expert - which, thanks to this forum, I realized he wasn't.
 

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Re: Calculating System Impedance

Bnuke said:
I've been thinking of replacing my speakers with 2 sets of the Polk EX3560 component speakers and using the included tweeters to replace the Bose tweeters and twiddler but I can't find specific info on the Bose tweeters/twiddler. Anyone know?

As suggested by Bruce in earlier posts, I would dump (or disconnect) the door tweeters as well as the twiddler. I did both and run coax speakers (BA in front, Infinity in the rear, and a Polk sub).

They will not help well matched components, and may even detract from optimum performance. Just imagine smaller versions of the cheap Bose in the doors, foggetaboutit!
 

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Re: Re: Calculating System Impedance

DaleB said:


As suggested by Bruce in earlier posts, I would dump (or disconnect) the door tweeters as well as the twiddler. I did both and run coax speakers (BA in front, Infinity in the rear, and a Polk sub).

They will not help well matched components, and may even detract from optimum performance. Just imagine smaller versions of the cheap Bose in the doors, foggetaboutit!
I misspoke my intentions. I want to yank the Bose tweeters and twiddler and replace them with the tweeters that come with the Polks.

I didn't realize that you (DaleB) were using both BA and Infinity. I really like BA speakers. I got a bunch of them for my home theater. Is it better to do component speakers?

BTW, I got to wash my X today. Good-bye road salt!!!
 

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Bnuke,
I just installed some Crystal comps in the front doors. Are they better than coax speakers? Since I didn't have coax in there before, i can't really help there. They are more difficult to install, but they do sound great! It just depends if you are doing the install yourself and how much time you have. Coax's are pretty much drop-in replacements. The comps take a bit longer but I figured in the long run I am ready for amps if I want them. I also like having the tweeters more at ear level. Just my $.02.
 

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Re: Re: Re: Calculating System Impedance

Bnuke said:


I misspoke my intentions. I want to yank the Bose tweeters and twiddler and replace them with the tweeters that come with the Polks.

I didn't realize that you (DaleB) were using both BA and Infinity. I really like BA speakers. I got a bunch of them for my home theater. Is it better to do component speakers?

BTW, I got to wash my X today. Good-bye road salt!!!
I am sure good components would be even better. But the BAs are very nice sounding. An improvement over the Infiinity, but not enough to justify a replacement in the rear doors. I would not bother with components in the rear doors either. Not cost-effective IMHO.
 

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4 ohm clarification

Distortion can be caused by impedance shifts only if the resistance is increased not decreased. A speaker drawing a 16 ohm load from a speaker designed for 8 ohm operation will not cause more distortion, but rather less. Impedance induced distortion is created when the amplifier is unable to supply the speaker draw within a specified THD. A 4 ohm speaker will draw more power than an 8ohm specific amplifier can properly supply, and at comparable volume levels, the sound may become distorted. Using a 4 ohm speaker on a 2 ohm-designed amplifier, as proposed, will lower the effect of distortion, but may require the amp to work at very high amplification levels to reach the same dB volume levels as ohm matched speakers. Frequency response in higher ohm (lower resistance) speakers is only affected in direct relation to volume levels. In affect, you get the same change in frequency response in switching from 2 ohm speakers to 4 ohm speakers, as you would when lowering the volume control. You will simply perceive less bass response, same as lowering the volume knob. The frequency response curve of the speaker does not change with ohm ratings, but more sound means more bass.

Confused?

Using 4 ohm speakers instead of the Bose 2 ohm will lower distortion tendencies.
Using 4 ohm speakers will decrease volume levels at all points of the frequency response curve, you will hear less bass, as well as less of all other frequency productions.
In most cases, it will still sound better than the miserable Bose speakers.
 
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