Fi voice coils

[afrakes]

I'm looking at buying a single dual 2 fi q 15 to run at 1 ohm but it says online that the true voice coil impedance is actually 1.4 ohms per coil for the dual 2. Does this mean I will really be running at .7 ohms and if so do I need to buy an amp that's stable under 1 ohm??

[skittlesRgood]

the DC resistance is 1.4 and .7ohm, yes.

[mrd6]

Yeah, its the Re for "real" or dc impedance of the coil. But its usually not a big deal going .7 from 1, what amp are you thinking of running?

[Chris Hammer]

I'm looking at buying a single dual 2 fi q 15 to run at 1 ohm but it says online that the true voice coil impedance is actually 1.4 ohms per coil for the dual 2. Does this mean I will really be running at .7 ohms and if so do I need to buy an amp that's stable under 1 ohm??

You will more than likely rise to over 1ohm...maybe even over 2...I would not worry about it at allm Most subs when you use a DMM the coils come out under 1ohm or 2ohm load. my experience anyway.

[afrakes]

Yeah, its the Re for "real" or dc impedance of the coil. But its usually not a big deal going .7 from 1, what amp are you thinking of running?

I was thinking about running anything from aq, sundown, Rockford, dc, etc. something well built around 2000 to 2500 rms

[skittlesRgood]

guys, impedance is not the DC resistance of the coil. those are two separate things. the dc resistance is lower than the impedance. just look at any home speaker on parts-express. you will see an "8ohm speaker" and the DC resistance will be about 6.2ohm.

[caraudionoob]

skittlesRgood is right. Here's more info.

Straight from wiki.

Re - Measured in ohms (Ω), this is the DC resistance (DCR) of the voice coil, best measured with the cone blocked, or prevented from moving or vibrating because otherwise the pickup of ambient sounds can cause the measurement to be unreliable.Re should not be confused with the rated driver impedance, Re can be tightly controlled by the manufacturer, while rated impedance values are often approximate at best.. American EIA standard RS-299A specifies that Re (or DCR) should be at least 80% of the rated driver impedance, so an 8-ohm rated driver should have a DC resistance of at least 6.4 ohms, and a 4-ohm unit should measure 3.2 ohms minimum. This standard is voluntary, and many 8 ohm drivers have resistances of ~5.5 ohms, and proportionally lower for lower rated impedances.

Or in laymen's terms,

"This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load."

(from the12volt.com)

[WillPwn4Food]

I'm looking at buying a single dual 2 fi q 15 to run at 1 ohm but it says online that the true voice coil impedance is actually 1.4 ohms per coil for the dual 2. Does this mean I will really be running at .7 ohms and if so do I need to buy an amp that's stable under 1 ohm??

You will more than likely rise to over 1ohm...maybe even over 2...I would not worry about it at allm Most subs when you use a DMM the coils come out under 1ohm or 2ohm load. my experience anyway.

in what world would you end up going from .7 to over 2 from rise? Maybe to 1 but 2 seems a little excessive.

[bkolfo4]

Man this topic KILLS me every time it is brought up.

DCR is the DC resistance of the coil. It is the resistance of the coil when DC current is applied.

Impedance is the AC resistance of the coil when AC current is applied.

Leave rise out of it. For the 1,000,000 time - every sub has an impedance peak at the resonant frequency of the cone - in the box or sitting on your kitchen table. The peak is not just at that one frequency - the impedance starts to rise below the Fs and falls back down above it. Too many people take power readings and assume the impedance is rising due to the box, but most if the time it is just within this peak caused by the driver's resonant frequency.

Look at this impedance plot for a driver in free air:

It is an 8 ohm driver, but the impedance is as high as 35 ohms!! Does that mean the driver will get less power at 40 Hz? Yes, but does it mean the driver will be lose 6 dB at 40 Hz compared to other frequencies? NO!!! It is just how it works, and unless you are burping at a specific frequency or know the impedance at every frequency you will play, don't worry about it!!!!

In the case above, you played a 40 Hz test tone and said "man look how bad the rise is" and then tried to correct it by changing from an 8 ohm coil to a 1 ohm coil. Now what will happen the first time you play 110 Hz????

Enough for now. . .

[bkolfo4]

in what world would you end up going from .7 to over 2 from rise? Maybe to 1 but 2 seems a little excessive.

Wow.