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The info is correct, but I'm not sure at this point how they have pulled this off - We don't have any in-stock right now - so I don't have one I can get to for inspection.

I have a couple of people trying to track down the info on this.

I'll update as soon as I know more.

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Jeff Kitchen replied on Thu, Jul 23 2009 2:08 PM

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So here is the skinny on this one (super cool stuff):

Infinity has a patent on the first ever woofer with 3 voice coils. Using the switch in one position the voice coils are wired to provide a 2.1 ohm load, and in the other position it is a 4.3 ohm load.

I don't have the details at this point on the individual voice coil impedance - however, this is not really that much of a concern, as there is only a single input on the subwoofer - so the 2-ohm and 4-ohm figures are really the ones that matter.

This provides a whole new level of flexibility to building a system.

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TigerHeli replied on Thu, Jul 23 2009 2:57 PM

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I am not seeing how they work this.

The math is simple enough, in series, the impedance sums,

so if 4.3 is the series impedance:

3x=4.3

x= 1.43,

but in parallel, that results in a 0.47-ohm load.

if 2.1 is the series impedance

3x=2.1

x=0.7

but in parallel, that results in a 0.23 ohm load.

I made the assumption that all voice coils were the same impedance and power handling, you could do something with series-parallel wiring and one voice coil handling more power than the other two and maybe come up with something that works, but that doesn't seem extremely practical.

Actually, this would be easy to do with a dummy VC, and that COULD be what they are doing -

I think this would work:

The sub is DVC-2-ohm and each VC supports 350W. In the 2-ohm position, only one VC is connected and the single voice coil handles 350W. In the 4-ohm position, the second VC is wired in series with the first and the sub could handle 700W, but if you connect 350W to it, each VC sees 175W, which is okay. Or ...
The sub is DVC-4-ohm and each VC supports 350W. In the 4-ohm position, only on VC is connected and the single voice coil handles 350W. In the 2-ohm position, the second VC is wired in parallel, and again, the sub could handle 700W at 2-ohms, but instead each VC again sees 175W, which is okay.

Of course this is possible with any DVC subwoofer, but usually brings up the issues highlighted by Scott Neill here, but perhaps Infinity has found ways to work around this, or perhaps they have decided a more marketable solution was worth the drawbacks.

Just supposition on my part, though ....

Thinking more about this ....

The easiest and most practical solution would be to simply design the sub as SVC and have one 350W 2-ohm VC and one 350W 4-ohm VC, and a selector switch to choose between them. That could well be what they did, would probably be patentable, and would be the easiest solution.
If they told you it was three voice coils, perhaps it is one 350W 2-ohm coil and two 175W 2-ohm coils (or all 4-ohm coils) and the selector chooses between the one 350W or the two 175W coils. That would be more honest with what they told you, but not sure what it gains you over the two coil solution above.

2002 Ford Focus Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

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TigerHeli replied on Thu, Jul 23 2009 3:04 PM

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Either way - it's nice to have a sub that is the same power handling at 4-ohms or 2-ohms to make up for all the times people bought a sub and amp only to find they weren't compatible at the required impedance.

2002 Ford Focus Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

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Jeff Kitchen replied on Thu, Jul 23 2009 5:00 PM

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Still digging, but here is a bit more of the story:

It has a simple switch/jumper which uses either all three in parallel to offer a 2ohm load, or 2 in series then parallel to offer a 4.3 ohm load.

Hopefully we will have more info on exactly how this works in the next week or two -

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TigerHeli replied on Thu, Jul 23 2009 5:24 PM

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Clever ....

That ALMOST works but not quite (one of the electronics theory guys correct me if I am wrong).

I think you mean two in parallel, then series ....

For the parallel, I just guessed at numbers off the parallel site.

Turns out three 6-ohm VC's give you a 2-ohm load.

Two 6-ohm VC's in series gives you a 12-ohm load, and 12-ohms in parallel with 6-ohms gives you a 4-ohm load.

Sounds great so far ....

Here's the problem ....

Let's say I have a 300W regulated amp.

At 2-ohms, the load splits evenly between the VC's so we see 100W on each voice coil.

At 4-ohms, in parallel, more current goes to the lower impedance, so the single VC sees 200W and the dual VC's split 100W total or each gets 50W - not good.

Lets look at it the other way, though:

Two 6-ohm voice coils in parallel are 3-ohms and in series with the remaining one are 9-ohms, so that idea doesn't work either.

Again, I am assuming that all of the VC's are the same impedance and power handling, and that might well not be the case ...

It's interesting, though!!!

2002 Ford Focus Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

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TigerHeli replied on Sat, Jul 25 2009 7:21 AM

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Okay, I played with the numbers and I figured out another way it could work, but I ran into the same obstacle:

If we try:

Three VC’s in series for 4-ohms
2 VC’s in Parallel and 1 in Series for 2-ohms.

The first config gives us that each VC is 1.333 ohms, so 300 W @ 4-ohms splits evenly at 100W per VC.

The second config …

Two 1.3333 VC’s in parallel is half the impedance or 0.6666-ohms. Add the remaining VC in series and you are at 2.0 ohms.

However, in a series circuit, the most power goes to the higher resistance, so again, the single 1.333-ohm VC sees 200W and the 1.333’s in parallel see 100W total or 50W each. Not good.

The other options I thought of didn’t even come close to working out:

3 VC’s in parallel for 4-ohms makes each VC 12-ohms,

3-series gives you 36-ohms

2S+1P=8-ohms

2P+1S=18-ohms

3VC’s in series for 2-ohms gives you each VC=0.6666, but

3 VC’s in parallel = 0.22 ohms

2S+1P=0.44-ohms

2P+1S=1-ohm

It also occurred to me that if we don't assume non-identical voice coils, what Infinity could be doing is simply "under-rating" the sub.

For example - let's assume the sub is wired per the previous post (which makes the most sense).

For 350W subs, each VC should see 117W.

But in the 4-ohm config, one VC will see 233W.

Let's assume instead of each VC being 117W, all of them are 233W (or even that one of them is 233 and the others are 117W, that would work also).

I am not enough of a subwoofer engineer to know what the downside of sending half of rated power to a voice coil, but assuming it doesn't matter there are only two "drawbacks" to this:

In 4-ohm mode - if you "push" the sub (say you run a clipped signal or a 500-600W amp), you will always burn up one voice coil first, and always the SAME voice coil.
In 2-ohm mode, in reality the sub should handle at least 466W, and maybe as much as 700W, but is only rated for 350W (at least voice-coil wise, the suspension and surrounds might not be designed for that). That isn't exactly a bad thing, as newb's to the hobby are always thinking that running more power at lower impedance is a good thing, so this gives the sub some "cushion" for that.

If that is truly what is happening, it's not necessarily a bad engineering idea, but it is a bit deceptive on the marketing (although so is Kicker selling you a 900W amp when it is claimed to do 750W), but that kinda fits the bill as well - Not to totally bring up the dead horse again, but this is the company that did the following:

2.7-ohm speakers really were (probably) a good engineering decision, and I have to believe Infinity's engineers understood and selected that number based on the fact that most 4-ohm stable amps would support it. If they had said "We are introducing a line of 2.7-ohm speakers and here's why this is an improvement ..." I would have been all for it. The problem I had was saying "Our speakers are 2-ohm so they get extra power from your receiver." And then only after people mentioned that the receivers said not to run under 4-ohms - "But they are 4-ohm compatible, b/c when they heat up, they are closer to 4-ohms", and only when that didn't totally fly "Okay, the DC Resistance is 2.7-ohms and most decks will be fine with that".

Closing thoughts:

Two-ohm has been the standard for subwoofer amps for probably a decade or more now (starting now to shift toward 1-ohm, but not there yet), and 4-ohm has been the standard for bridged amps for even longer. If it were really simple (and this isn't THAT revolutionary), someone would have done it previously. (It's possible, but unlikely, that Infinity had this solution five or more years ago and just waiting on the patents).
I don't know, but I think my idea of having a single voice coil design sub with selectable 2-ohm or 4-ohm voice coils has merit. BA did something similar with their sub where the motor and suspension were separated. The drawbacks I see are:
- One voice coil goes unused, so you are paying extra for parts you may never need and may wear out.
- Undoubtedly, at some point, someone would mistake it for a DVC sub, and 4-ohms in parallel with 2-ohms is 1.33 at the amp and an unbalanced load on the VC's - not good, but someone would have to not have the documentation and guess incorrectly to do that.

FWIW....

2002 Ford Focus Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

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J Ro replied on Wed, Aug 5 2009 9:37 PM

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I've been very patient for the specifications for these subs to show up on infinity's website, but so far nothing. I couldn't speculate any further about how they did it, but selectable impedance would be a desirable feature if it works. If they also incorporated the variable Q feature, i'd be buying them in bulk tomorrow!

I just hope the subs don't end up with wildly variable theille-smalle parameters that make them unpredictable. If the voice-coils indeed have different impedances, it would likely skew the characteristics enough that a box it works great in at 4 ohms is suddenly all wrong at 2 ohms.

Anyone notice the photos for the 10 and the 12 is identical?

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New Product Update 7.22.2009

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