Installed new speakers, rears are barely audible
12-02-2009, 09:01 PM
#17
Using a multimeter to measure the DC resistance will give only a ballpark indication of speaker impedance which is usually measured at a frequency of 1kHZ. A reversal of phase will affect bass frequencies only. A mismatch of impedance and/or sensitivity would give maybe a 6db difference maximum which sounds like less than you are describing. Sounds to me like a problem with your amp or fader control.
12-02-2009, 09:14 PM
#19
The front Pioneer speakers that you have are rated at 4 ohms impedance. This is the most common impedance for a standard car audio speaker. If the rears are original, I'll bet they are 4 ohms also. I don't think impedance is the issue.
12-02-2009, 09:28 PM
#20
Rennlist Member
Different speakers will require different levels of grunt to sound the "same". Additionally if there is a seperate "gain" control on the head unit for the different channels (I doubt there is a seperate one) that will reduce the difference.
12-02-2009, 09:52 PM
#21
Should have read your original post more closely. I see that you changed the rears as well. The Kenwoods are rated at 4 ohms also so impedance mismatch is not an issue.
Do I understand that you replaced two speakers on each side in the rear? I'm not familiar with how the hi-fi option speakers are set up. If you put 2 of the 4" Kenwoods on each rear channel, it's possible that there are external crossover components in the speaker circuit which will reduce power to the speakers. The new speakers do not require any external crossover components. They should be fed directly from the amplifier output.
Do I understand that you replaced two speakers on each side in the rear? I'm not familiar with how the hi-fi option speakers are set up. If you put 2 of the 4" Kenwoods on each rear channel, it's possible that there are external crossover components in the speaker circuit which will reduce power to the speakers. The new speakers do not require any external crossover components. They should be fed directly from the amplifier output.
12-02-2009, 10:40 PM
#22
Pro
Join Date: Aug 2006
Location: Schaumburg, IL.
Posts: 548
Likes: 0
Received 0 Likes
on
0 Posts
Check the impedance of the speakers from their spec sheets. BTW, impedance is the same as resistance, we just call it impedance because it's a function of frequency. If your rears are higher than fronts, that could explain it. Then there's the issue of sensitivity that Jeff raises, and that could be it too.
Edit: beat me to it. Probably a sensitivity thing, unless you possibly crossed the wiring.
Edit: beat me to it. Probably a sensitivity thing, unless you possibly crossed the wiring.
Resistance (measured in Ohms) is the opposition to a direct current (DC)
Impedance (measured in Ohms) is the opposition to an alternating current (AC)
The reason a standard multi-meter will not measure impedance correctly is due to the fact that the circuit inside the meter doing the measuring is exposing the outside circuit to a direct current and not an alternating current. So in a speaker/crossover network where you could have a capacitive or inductive impedance, or both, (measuring through coils/inductors and capacitors) a coil with DC applied by a standard meter will show it's resistance not impedance. A capacitor's impedance or resistance cannot be measured with a DC multi-meter at all since DC current will not pass through a capacitor but merely charge the capacitor. The opposition to current flow of a coil varies greatly based on it's inductance and frequency of the AC traveling through it (impedance). The opposition to current flow of that same coil with a direct current (constant or no frequency) flowing through it only varies based on the length and guage of the wire the coil is made of (resistance).
since DC has no frequency and AC must have a frequency (or it would be DC) you are correct. Different electrical components (capacitors/semiconductors/inductors behave in different ways when exposed to one or the other. Resistors behave the same in both instances.
I think Cmat is on to something. Phase is not likely to be the culprit but speaker efficiency and an impedance mismatch together may be enough, certainly if the Hi-Fi option Nokia amp and nokia speaker set were designed for use together.
Nick
12-02-2009, 11:51 PM
#23
Addict
Rennlist Member
Rennlist Member
Join Date: Sep 2003
Location: Saratoga, CA
Posts: 993
Likes: 0
Received 0 Likes
on
0 Posts
Noah: DId you simply run wire from the HU to the rear speakers directly (just for testing), instead of using the original wiring? Pretty easy to check phase the dummy way. Just try the different combos.
Warpig: Nice explanation.
Warpig: Nice explanation.
12-03-2009, 01:18 AM
#24
Rennlist Member
Thread Starter
My understanding was that it didn't matter which attached to which, since there are only two wires for each speaker -- a power and a ground. Do I have that right?
Thanks for everyone's help and comments on this -- much appreciated.
12-03-2009, 02:49 AM
#25
Rennlist Member
Give me **** all you want, but if all you messed with is the wiring, then guess what the problem is!
AKA phase: + to + and - to - correctly for both speakers respectively. There is only one correct way!
All cheap aftermarket speakers are pretty much identical: they are all around 4ohms, except some of the more expensive ones (2.7 for the Polk MMs), and even these work great with most stock head units.
AKA phase: + to + and - to - correctly for both speakers respectively. There is only one correct way!
All cheap aftermarket speakers are pretty much identical: they are all around 4ohms, except some of the more expensive ones (2.7 for the Polk MMs), and even these work great with most stock head units.
12-03-2009, 06:31 AM
#27
Addict
Rennlist Member
Rennlist Member
Sorry for the long post, but I just want to make things a little clearer on impedance by trying to put this in layman’s terms.
If you are defining electrical resistance correctly, Impedance is not resistance.
Impedance is the total opposition to the flow of electricity. Resistance is only part of that. As Warpig stated above, inductive and capacitive reactance are also a part of it.
Please excuse the oversimplified and over-analogized explanation below
First of all Audio is AC current
AC current "reacts" differently in certain devices than DC does. This "reactance" can oppose the flow of electricity. This opposition is called "Reactance"
Different materials let electricity flow better than others. Materials that don’t conduct that well get in the way of good electrical flow. This is called "Resistance"
The electricity doesn’t really care why it is being screwed with, reactance, or resistance; they both just get in its way... or impede it. So Resistance and Reactance make up Impedance.
Resistance is fairly constant, but Reactance varies with frequency, but that isn’t that important in understanding the problem with mismatched speaker impedances in your car stereo.
Speakers
A speaker has a coil of wire on the back of the cone.
When the electricity goes through the coil it creates–or induces–a magnetic field. The back end of the coil will change from North to South depending on which way the electricity is flowing.
On the back of the speaker there is a magnet.
If the magnet near the back of coil is North, then when the coil becomes North the coil will repel from the magnet pushing the coil (and the attached cone) forward, away from the magnet.
When the electricity reverses, the back of the coil becomes South and is attracted to the magnet and pulls the coil and cone backwards.
This moving coil/cone causes alternating pressure waves in the air–Sound
Back to Impedance
The wire in the coil has a bit of resistance to it. This is part of the total impedance. But more importantly, the electricity is generating the magnetic field (this is a reactance)
This magnetic filed is used to do work (push the cone) so in this case of a speaker, you can think of resistance as plain resistance, and reactance as opposition to flow caused by doing work (pushing the cone).
Your amplifier is designed to work best with a certain "load" on it. At this load you get the most efficient power transfer from amplifier to the work (sound output)
Analogizing this with your 993…
There is a basic rolling resistance, friction of bearings and stuff, the tires flexing, ext. that is like the resistance component of an electrical circuit.
Again, impedance is more than just resistance.
When the car is started from a stop the inertia is a huge obstacle to overcome. Think of the inertia as the reactance, the work needed to be done. Between the friction and the inertia a huge impedance is presented to the motor, too high for the motor to overcome on its own.
So a transmission is inserted between the motor and the wheels to bring the impedance load down for the motor. This way the impedance load better matches the impedance the motor is comfortable pushing.
As the car accelerates, the impedance drops, because the inertia (reactance) changes. The impedance becomes too low for the motor.
As the car gets moving faster, the energy is being put out, but the transfer isn’t efficient as motor gets out of the optimum part of it’s torque curve, so you shift to another gear to get back to the most efficient power transfer.
Back to Speakers
Speakers work similarly. If the Amp is designed to push a 4-ohm load then a 4-ohm speaker will give you the best power transfer to the air.
If you put a 8 ohm speaker on it, it loads it down and reduces output (like being in too high a gear in the car)
If you put a 2 ohm speaker on it output can be higher for a bit, but since there is too little a load, amplifier damage can occur because the electricity flows so fast through the circuit it can overheat the amplifier’s internal components. This would be the equivalent of driving around at 6800RPM and never up****fting.
There are a lot of other factors that can contribute to inefficient power transfer, but impedance is a biggy.
But 4-ohm speakers wouldn’t load down your system too much and cause a low output. Too high an impedance would.
4 ohms would more likely be too low, potentially causing amp overheating, not reducing sound output that dramatically.
So I'm with Bart on this one, and I also think he is correct that the factory rears are 12 ohm.
Phase (polarity)
As to what Captain GSR and Ed are talking about, phase, that can be an issue too.
Remember from above, the direction of the speaker cone movement is dependant on the direction the electricity flows through the coil.
But you have two speakers back there. If both speakers are wired correctly then the electricity/magnetism will cause both cones to push out and pull back at the same time (in phase with each other)
However if one is wired reverse the other, then one cone will push out, and the other will simultaneously pull back.
It is a small space back there in the back window, so the push from one speaker combines with the pull of the other and gives relatively little net pressure change… meaning little net sound output.
That sounds like the problem.
Of course modern amplifier design and protection circuits can throw a wrench into all of this speculation.
But my vote is it’s a phase issue.
If you are defining electrical resistance correctly, Impedance is not resistance.
Impedance is the total opposition to the flow of electricity. Resistance is only part of that. As Warpig stated above, inductive and capacitive reactance are also a part of it.
Please excuse the oversimplified and over-analogized explanation below
First of all Audio is AC current
AC current "reacts" differently in certain devices than DC does. This "reactance" can oppose the flow of electricity. This opposition is called "Reactance"
Different materials let electricity flow better than others. Materials that don’t conduct that well get in the way of good electrical flow. This is called "Resistance"
The electricity doesn’t really care why it is being screwed with, reactance, or resistance; they both just get in its way... or impede it. So Resistance and Reactance make up Impedance.
Resistance is fairly constant, but Reactance varies with frequency, but that isn’t that important in understanding the problem with mismatched speaker impedances in your car stereo.
Speakers
A speaker has a coil of wire on the back of the cone.
When the electricity goes through the coil it creates–or induces–a magnetic field. The back end of the coil will change from North to South depending on which way the electricity is flowing.
On the back of the speaker there is a magnet.
If the magnet near the back of coil is North, then when the coil becomes North the coil will repel from the magnet pushing the coil (and the attached cone) forward, away from the magnet.
When the electricity reverses, the back of the coil becomes South and is attracted to the magnet and pulls the coil and cone backwards.
This moving coil/cone causes alternating pressure waves in the air–Sound
Back to Impedance
The wire in the coil has a bit of resistance to it. This is part of the total impedance. But more importantly, the electricity is generating the magnetic field (this is a reactance)
This magnetic filed is used to do work (push the cone) so in this case of a speaker, you can think of resistance as plain resistance, and reactance as opposition to flow caused by doing work (pushing the cone).
Your amplifier is designed to work best with a certain "load" on it. At this load you get the most efficient power transfer from amplifier to the work (sound output)
Analogizing this with your 993…
There is a basic rolling resistance, friction of bearings and stuff, the tires flexing, ext. that is like the resistance component of an electrical circuit.
Again, impedance is more than just resistance.
When the car is started from a stop the inertia is a huge obstacle to overcome. Think of the inertia as the reactance, the work needed to be done. Between the friction and the inertia a huge impedance is presented to the motor, too high for the motor to overcome on its own.
So a transmission is inserted between the motor and the wheels to bring the impedance load down for the motor. This way the impedance load better matches the impedance the motor is comfortable pushing.
As the car accelerates, the impedance drops, because the inertia (reactance) changes. The impedance becomes too low for the motor.
As the car gets moving faster, the energy is being put out, but the transfer isn’t efficient as motor gets out of the optimum part of it’s torque curve, so you shift to another gear to get back to the most efficient power transfer.
Back to Speakers
Speakers work similarly. If the Amp is designed to push a 4-ohm load then a 4-ohm speaker will give you the best power transfer to the air.
If you put a 8 ohm speaker on it, it loads it down and reduces output (like being in too high a gear in the car)
If you put a 2 ohm speaker on it output can be higher for a bit, but since there is too little a load, amplifier damage can occur because the electricity flows so fast through the circuit it can overheat the amplifier’s internal components. This would be the equivalent of driving around at 6800RPM and never up****fting.
There are a lot of other factors that can contribute to inefficient power transfer, but impedance is a biggy.
But 4-ohm speakers wouldn’t load down your system too much and cause a low output. Too high an impedance would.
4 ohms would more likely be too low, potentially causing amp overheating, not reducing sound output that dramatically.
So I'm with Bart on this one, and I also think he is correct that the factory rears are 12 ohm.
Phase (polarity)
As to what Captain GSR and Ed are talking about, phase, that can be an issue too.
Remember from above, the direction of the speaker cone movement is dependant on the direction the electricity flows through the coil.
But you have two speakers back there. If both speakers are wired correctly then the electricity/magnetism will cause both cones to push out and pull back at the same time (in phase with each other)
However if one is wired reverse the other, then one cone will push out, and the other will simultaneously pull back.
It is a small space back there in the back window, so the push from one speaker combines with the pull of the other and gives relatively little net pressure change… meaning little net sound output.
That sounds like the problem.
Of course modern amplifier design and protection circuits can throw a wrench into all of this speculation.
But my vote is it’s a phase issue.
12-03-2009, 12:16 PM
#28
Rennlist Member
Is there a separate pair of wires for the tweeter back there? If so, maybe you connected your speakers to those. That could cause low volume. <<<EDIT: Found the answer in another thread - there are only two wires to each rear speaker.
Regardless, IMHO, forget the rear speakers! Take them out, return them to the store, set your Fader full front and enjoy better sound!
Regardless, IMHO, forget the rear speakers! Take them out, return them to the store, set your Fader full front and enjoy better sound!
12-03-2009, 12:21 PM
#29
Three Wheelin'
Join Date: Feb 2007
Location: Westchester NY
Posts: 1,508
Likes: 0
Received 0 Likes
on
0 Posts
No, they will work but the bass will be minimal. With the 4ohm speakers you put in, those speakers should be lowder. It seems to me that these speakers just need more clean power to make them work.
12-03-2009, 12:31 PM
#30
Most audio amplifiers are voltage sources. They will deliver the same voltage regardless of the impedance of the speaker. The power to the speaker varies as the inverse of the speaker impedance, all other things being equal. If you change from an 8 ohm speaker to a 4 ohm with no other changes, you will deliver twice the power to the speaker.
This only works within the safe operating boundaries of the amplifier. If you go too low in load impedance, currents in the amplifier will exceed safe limits and it can be damaged. Unless it is a high end system, speakers in cars are usually 4 ohms maximum to get reasonable power from the 12 volts available.
As I said, I think the problem has to do with the speaker wiring. I believe the front speakers on each channel have multiple drivers with the hi-fi option but I don't know about the rear. If there are two or three openings in each assembly, then this is a 2 or 3 way system. The output of the amplifier is split up by crossover componts and fed to each speaker...low frequencies only to the woofer and so forth. The speakers you installed are full range and they should receive the direct output of the amplifier without any crossover network. Note that this is also true for the fronts.
How many separate speakers were there originally on each channel, front and rear? This is important because if there are multiple drivers, it is likely internal crossover components are the cause of your low output now.
This only works within the safe operating boundaries of the amplifier. If you go too low in load impedance, currents in the amplifier will exceed safe limits and it can be damaged. Unless it is a high end system, speakers in cars are usually 4 ohms maximum to get reasonable power from the 12 volts available.
As I said, I think the problem has to do with the speaker wiring. I believe the front speakers on each channel have multiple drivers with the hi-fi option but I don't know about the rear. If there are two or three openings in each assembly, then this is a 2 or 3 way system. The output of the amplifier is split up by crossover componts and fed to each speaker...low frequencies only to the woofer and so forth. The speakers you installed are full range and they should receive the direct output of the amplifier without any crossover network. Note that this is also true for the fronts.
How many separate speakers were there originally on each channel, front and rear? This is important because if there are multiple drivers, it is likely internal crossover components are the cause of your low output now.