Oh BTW, I came across this for those speakers:
Infinity - Car Audio

Tweeter level adjustment - The 6832cf also features a tweeter level adjustment located on the front of the speaker and can be set at the reference level of 0dB. If the speakers are located low in the doors or if you are looking for a brighter sound, set the tweeter at +3dB.

Just an FYI. As I think I will leave the factory tweeters disconnected and bump the tweeter on the infinity after a slight directional adjustment.

As I too believe by leaving the factory tweets connected that the impedence will be affected...it's ohms law!

 

Laws get broken all the time. There once was a time when this mattered a lot more than it does today. The built in amps in these systems are far more forgiving in impedance mis-matches. 2ohms to 4 ohms is no big deal. Adding extra tweets, no big deal. Phase is more important so make sure to keep the +s and -s straight.

 

FishingNut,

Did mine on a supercab... remove the two screws for the window, the upper seatbelt bolt then you can pull off the upper panel. This will give you access to the screws and one plastic pop rivet that will remove the rear panel, it lifts up like the front doors. You also have to take of the bottom seat belt screw.

 

Thanks PITS, polarity is another law that I also believe in

So I will make sure to get the polarity right.

 

Thanks pvanvalin, reps coming at you for that....

 

Going the other way is where more damage is done...i.e. Using 2 Ohm speakers on an amp meant for 8Ohm. The lower the impedance the more current is drawn. It can cause an AMP not meant for it to overheat and blow the finals. This is much less of an issue at the higher frequencies (like adding a second tweeter or having a tweeter with a mismatched impedance) as the amount of current drawn is inversely proportional to the frequency. At the lower frequencies, such as where a Sub operates, it can be disastrous.

Simply dropping in a speaker with a lower impedance than the AMP was built for will definitely get an AMP to put out more power than it was putting out previously. However, the transistors, wiring traces on the PCB, and all of the rest of the components are designed for a given power output. I doubt Ford's headunit is overbuilt to handle that for the long term. AMPs that support this will state it. They will say that they put out X Watts at 8 Ohms and Y Watts at 4 Ohms. If it doesn't say 2 Ohms in the specs then I strongly suggest not hooking up 2 Ohm loads for the long term.

Best results will be obtained by matching the speaker's impedance to that recommended of the amp.

Also, the impedance of a speaker has nothing to do with its efficiency. You can easily get a 4 Ohm speaker that is less efficient than an 8 Ohm. Many speakers are offered with multiple impedance values to allow an installer to custom build a speaker set fed off of one amp output. For example you can wire 2 8 Ohm speakers in parallel and have a net impedance to the amp of 4 Ohms. This is commonly done in sub boxes where someone wants 2 10" woofers because they don't have the room for a 12" or 14". You can get 2x10" 8 Ohm subs, wire them in parallel, and have a system impedance of 4 Ohms. It looks to the amp like a single 4 Ohm speaker.

You go buy a set of $3,000 speakers for a home Audiophile system and they are most likely going to be 8 Ohm and believe me they are plenty efficient


---Aaron

 

For those of you that don't have a factory tweeter and are not looking for a set of separates (a speaker with a physically separate tweeter) I recommend the following speakers:

Kenwood KFC-C6894PS

They are 3-ways and all three components are mounted biaxially on the speaker. This will not give you as good sound quality as the Infinity's mentioned on this thread but for $79.99 from crutchfield they are a great deal. They are also a true 6x8 speaker so they should have a little more woofer surface area then the Infinity's that are 5x7s. That should give you a touch more bass. I guarantee the tweets wont be quite as good however.

If you want to save a few bucks they are a good alternative to the Infinity product IMHO.

---Aaron

 

I would agree with most of what you are saying Aaron as I have been in the elctronics field for 30+ years (started real young - 1977 - US Navy) and am pretty knowledgeable on the subjecft. Dude you should have seen the system I put together in the late 70's when I was stationed overseas in the Pacific. And also have a couple of Onkyo A/V systems with all Polk speakers, but I would not call myself an audiophile by any means. And like most here on this thread I do love my music and occasionally do like it loud.

So I will not be rocking these things out constantly, therefore the statement about less is worse does apply but probably not to me. And I also believe that the 2 ohms will be closer to 4 due to the gauge wiring utilized in the vehicle as per the statement that was made by Harmon Kardon:

True Four Ohms— All Reference speakers feature two ohm voice coils. Original factory-installed speaker wiring in many cars is 18-22 gauge. This wire, and heating in the voice coil when power is applied, increase the impedance “seen” by the amplifier or head unit. The impedance of Reference Speakers has been adjusted to compensate for this increase and can be safely driven by any head unit.

 

I had seen that statement on the Infinity's as well. It doesn't wash with me as wire is a purely resistive load while speakers are inductive. As an electronics guy you would know that a schematic of that circuit would show the wire as a fixed value resistor and the speaker as an inductor (coil). One cannot change a circuit's impedance by adding a resistor...so I am just not sure how they can make that statement.

The only thing that would make sense to me is that since these are just 5x7 or 6x8's they figure they are never really gonna do much below 120Hz anyways so the additional power draw from the amp would be minimal at best at frequencies above 120Hz...and the lower frequencies where the current is greatest the wire would have a pretty large voltage drop and the speaker can't do anything in that area anyways.

Impedance matching is definitely more important when dealing with the low freqs a sub would put out than it is with these little 6x8 door speakers.

All said, it is still a concern with a factory head unit as I am confident Ford doesn't put a lot of money in those puppies with the bean counters and all!

It is definitely a good thought though.

---Aaron

 

This is not exactly true. Impedance (Z) = Resistance (R) + Reactance (X) * j (where j is the imaginary component of the reactance). j is +90 degrees for an inductive load and -90 degrees for a capacitive load. This is because an inductor looks like a short to DC and an open to AC, while a capacitor looks like an open to DC and a short to AC.

Z=R+jX

Reactance is non-dissipative and results from the inductance or capacitance component of the load. The reactance component is only present in an AC system (which an audio circuit most certainly is). A reactive load does not result in real power dissipation.

Resistance is dissipative and is seen in either AC or DC circuits, which is why you have to add it to the reactance component. A resistive load results in real power dissipation.

Straight wire is inductive, and for 20ga wire has an inductance of approximately 20nH per inch, so there is a reactive component to the wire as well.

 

Yes, but resistance != impedance. If the wire is 2 Ohms it is 2 Ohms at all frequencies (ignoring the reactance component of the wire which I address below). Unlike 2 Ohms of impedance which is 2Ohms ONLY at 1KHz. It varies (as you obviously know) at other frequencies. There is a difference in behavior between a 4 Ohm speaker and a 2 Ohm speaker with a 2 Ohm series resistor. The point I was making is you cannot throw a 2 Ohm resistor in a circuit with a 2 Ohm voice coil and call it an 2 Ohm voice coil. Doing so is called Marketgerring. That is where marketing people start to come up with engineering terms that don't work to try to get people to buy things.

I intentionally ignore that factor for the discussion. I do so for two reasons. The first is that it is negligible. If we start bringing that into the equation we should also start looking at air temperature, purity of copper etc.

However, if you are mentioning the reactive property of a straight wire you should also mention the capacitive properties of the TWO wires running to the speaker together. While a straight wire has reactance a pair of wires has capacitance. I think if you look at the two of those properties together and the affects they will have on each other we can safely ignore any reactance properties of a single conductor in the path.

Good discussion although it is really all academic at this point! None of this will matter for a little 6x8 speaker.

 

I totally agree with what you are saying. I understand that ideal resistance is non-frequency dependent. The point I was trying to make is that I think your statement is a little unclear about is the difference between impedance and reactance. Reactance is TOTALLY frequency dependent, Resistance is TOTALLY NOT frequency dependent, but impedance is a combination of both resistance and reactance. So it has a frequency-dependent component and a non-frequency-dependent component.

I agree with you that perhaps my response has taken the discussion a bit too far on the academic side when you are talking about a real-world audio system problem. My only point was to clarify the terminology.

Also I agree with you that at audio frequencies, the wire inductance can probably be considered negligible, but it can become a factor at higher frequencies and long wire lengths .

-los341

 

Yes, my original statement was definitely unclear and it is my fault. I often refer to the frequency dependent components collectively as impedance and refer to the non frequency dependent component as resistance especially when talking to people not familiar with electronics. It is technically inaccurate but is common slang as you probably know. Starting to split up capacitance and reactance would have lost what audience this thread had left

I still think what Infinity and Harmon/Kardon is saying about their speakers is a little disingenuous. Saying they can use a 2 Ohm voice coil because the feed wire has 2 ohms of resistance and it is a 'True 4 Ohm Coil' (their terminology, not mine) is completely incorrect. A 2 Ohm voice coil with a 2 ohm fixed value resistor will not behave like an actual 4 Ohm voice coil. That was the point I was trying to make.

Again, good discussion though. I am going to head out to the garage and finish the install on my backup camera now. Man this 6.7L rocks!

---Aaron

 

To those replacing the rear speakers, I have seen reference to a high pass filter. I have not taken mine apart but, but was curious if this filter is in front of the mid, or between the mid and the tweeter.
The reason I ask is that I am installing the Infinity 6832, and was wondering if this would "kill" the built in tweeter on the Infinity speakers, or it just sends High frequencies to the factory tweeter?

 

I did mine on a supercab and did not see a rear tweeter, only a front one...did I miss something or is this another "difference" between the crew and super cabs?

For example my sub woofer is under the rear seat behind the driver, not behind the rear seat. But I know why, as there is no room behind the seat on a super cab .