The factory dash/rear 2.6" speakers are 8 ohms. All the quality replacment 3.5" speakers are 4 ohms.
Will this cause any problems with the factory head unit amp? I'm not sure which aftermarket head unit i'm going with yet but I would like to change out the dash and rear factory speakers for now. The door speakers have already been replaced.
Thanks!!!!
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2007 FJ - Titanium Metallic, AT, CQ, Upgrade Package #2, GY, 2Q, EL, C7, K&N Air Filter, Westin SS Step Tubes, Audiovox Alarm with Remote Start. 03/30/06
Most likely not. 4 ohm is 1/2 the resistance of an 8 ohm. Does not mean the speaker will play 2x as loud. Means the amp in the head unit can deliver more power to the speaker. Usually 2x the wattage but from this head unit I doubt it. Might see 25% more wattage to the speaker. Will it play louder, most likey not. Will it sound better, not because of the impedence, but yes because it is a better speaker. Lower impedence means more distortion from the amp as well. So keep that in mind. As does more heat. Hope this helps.
Most likely not. 4 ohm is 1/2 the resistance of an 8 ohm. Does not mean the speaker will play 2x as loud. Means the amp in the head unit can deliver more power to the speaker. Usually 2x the wattage but from this head unit I doubt it. Might see 25% more wattage to the speaker. Will it play louder, most likey not. Will it sound better, not because of the impedence, but yes because it is a better speaker. Lower impedence means more distortion from the amp as well. So keep that in mind. As does more heat. Hope this helps.
If you change the speaker to 4 ohm you will increase the power output of the headunit by roughly double. This increases heat, distortion, and strain on the factory amp outside the specifications it was designed for. Assuming that both sets of speakers (4 and 8 ohm) have the same sensitivity the power output would nearly double; however, better speakers will likely have more sensitivity than the stock ones. Long story short, the speakers will play considerably louder and may not be well matched to the rest of the system.
Here is an example of the two speaker configurations assuming that the maximum voltage of the FJ is 14.4 Volts:
I also need to check the wiring diagram to see if the two front sets are run in parallel, as the would complicate things. Let me get back to you all in a minute.
After a little more research, it seems the the front dash speaker (8 ohm) and the 6x9 door speaker (4 ohm) are wired in parallel on the two front channels. This would give you and impedance of 2.66 ohms. Because it is a parallel system, the affect of adding a 4 ohm speaker is less. By adding a 4 ohm dash speaker with a 4 ohm door speaker the total is 2 ohms, thus the difference is .66 ohms. I retract my prevoius statement that this would overdrive the head unit. Slight difference, but not enough for concern.
The same seems to hold true for the rear. The ceiling exciters are 4 ohm and the rear pillar speakers are 8 ohm. Replacing the rear pillar speakers with 4 ohm would yeild the same effect. The reason toyota has done it this way, is to limit the amount of power that goes to the small 2.6" high range speakers in the dash and in the rear pillar. A 8 ohm speaker will receive a little less than half of the wattage that a 4 ohm speaker would in a parallel wired system (the 4 ohm speaker has less resistance).
Long story short, 4 ohm full range speakers can be added to the dash and pillar without ill affect. Although, they will play a little louder than the 2.6" 8 ohm speaker do now.
Keep in mind that having 1/2 the resistance as befor and twice the power does not make it play twice as loud. Does a 200HP car go twice as fast as a 100hp car? Is not gear ratio, weight, dynamics etc all come into play. Any who. Being in the business of Audio since 1989 adding twice the power into a speaker only increases its SPL output by 3dB. Not really enough to notice. Now if you increase the amp power by a factor of 10, at this point you can double the SPL output to twice as much. If my math serves me right it would take 1000 watts of power to make a speaker play twice as loud as a 100 watt system would. To get twice louder without 1000 watts, you can double amplfier power and speakers from 100 watts + 8 speakers to 200 watts 16 speakers. One other way is to find speakers that have a higher effeciency rating. Finding a speaker at 100dB 1 watt 1 meter will play a lot louder than a 90dB 1 watt 1 meter speaker hence not needing to upgrade to bigger amps. That is what I look for when purchasing speakers outside of the way they sound first and for most. I think this has already been covered a 1000 times over befor. PS: Amps put out watts not the speakers. Speakers put out SPL in the form of DB. I always laugh at people who ask, "Hey man, how many watts do them speakers put out". Then I ask' "do you mean how many watts will the speakers handel". Also the best way to blow a speaker is send a square wave into the speaker. That is called distortion. If your speaker can hanel 100 watts you will more likely blow the speaker sending it only 50 watts than you would sending it 150 watts. With 50 watts the volume control is maxed out per se' with a larger 300 watt amp the 150 you put into the speaker the volume might only be 1/2 up with no distortion and still delivering clean power. I always have my amps rated at twice what the speakers are rated at handeling. This is called head room. I never will run out of power or risk blowing my system.
Just to clarify, I think we are talking about to different things...I was referring to head unit/amplifier output not speaker output. I was only saying that the speakers will play louder due to sensitivity and slightly more power in this arrangement.
After a little more research, it seems the the front dash speaker (8 ohm) and the 6x9 door speaker (4 ohm) are wired in parallel on the two front channels. This would give you and impedance of 2.66 ohms. Because it is a parallel system, the affect of adding a 4 ohm speaker is less. By adding a 4 ohm dash speaker with a 4 ohm door speaker the total is 2 ohms, thus the difference is .66 ohms. I retract my prevoius statement that this would overdrive the head unit. Slight difference, but not enough for concern.
The same seems to hold true for the rear. The ceiling exciters are 4 ohm and the rear pillar speakers are 8 ohm. Replacing the rear pillar speakers with 4 ohm would yeild the same effect. The reason toyota has done it this way, is to limit the amount of power that goes to the small 2.6" high range speakers in the dash and in the rear pillar. A 8 ohm speaker will receive a little less than half of the wattage that a 4 ohm speaker would in a parallel wired system (the 4 ohm speaker has less resistance).
Long story short, 4 ohm full range speakers can be added to the dash and pillar without ill affect. Although, they will play a little louder than the 2.6" 8 ohm speaker do now.
Thanks.......That's exactly what I was looking for. I ran this by one of the guys at work last night and the first thing he asked me was if the speaker pairs were wired in parallel or series. He also said that would make a difference.
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2007 FJ - Titanium Metallic, AT, CQ, Upgrade Package #2, GY, 2Q, EL, C7, K&N Air Filter, Westin SS Step Tubes, Audiovox Alarm with Remote Start. 03/30/06
1985 Chevrolet Corvette
2007 Harley Davidson XL 1200N
Last edited by MSgt.1091 : 08-26-2006 at 06:56 AM.
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