New Infinity Kappa - Page 2

AWehmeyer · 04-08-2008, 06:20 AM

JJ,
First, Nominal impedance isn't a measured parameter, it's a name. Of course, the impedance of a speaker is frequency dependent and the big rise at resonance is a result of back EMF from the coil moving in the gap. The rise at high frequency is due to the inductance of the voice coil.

Second, many OE speakers in newer cars are "2-ohm" models. Replacing those with 4-ohm speakers is hardly an upgrade.

Third, We've never had a report of a damaged head unit driving any of our 2-ohm speakers and we've been selling them for over 3 years.

BTW, damping factor is crap. It's a BS spec invented by marketing folks years ago to help sell the advantages of transistors over tubes. amps don't control the damping of a speaker. Here's why: The damping factor formula indicates that damping factor is the speaker's impedance divided by the output impedance of the amplifier. The only part of the speaker's motor that contributes to motion is the coil's inductance. When current flows through the coil, a magnetic field is generated and it opposes or is attracted to the field in the magnetic gap and that moves the speaker. Inductors also store energy in the form of current. When the signal from the amplifier goes away, the stored energy in the coil's inductance is dissipated and causes the cone to contine moving. (This stored energy causes the coil to move at the speaker's resonance frequency and this is the big impedance peak at resonance. The current that's stored flows in opposition to the current from the amplifier and that opposition is expressed as impedance in the curve you've posted). The idea behind damping factor is that a lower output impedance will cause more current to flow and will dissipate the stored energy more quickly. The speaker will stop moving faster. In practice, this doesn't work because the resistance of the coil is in series with the coil's inductance and the output impedance of the amplifier. The coil's DCR is always much higher than the output impedance of the amplifier and IT controls the rate of current flow. In fact, if the amplifier has an output impedance of .01 ohms and the DCR of the speaker is 4 ohms, the speaker has 400 times the control over damping than the amplifier does.

I think you're referring to "output regulation" (from CEA 2006A) in your post. Of course, the effects on frequency response of any series resistance is frequency dependent and will affect the frequencies where the impedance is lowest more than frequencies where the impedance is higher. In practice, that means a tiny bit more bass and a tiny bit less midrange.

As far as two ohm speakers go, we've just optimized the DCR of the speaker to extract more current from amplifiers. Connected to radios using the factory speaker wire, 2-ohm speakers provide a more optimum load than their 4-ohm counterparts. If the factory speakers being replaced are 2-ohm models, then 2-ohm replacements are more appropriate than 4-ohm replacements. If the factory speakers are 4-ohm models and the factory speaker wires will be used, 2-ohm speakers provide closer to a 4-ohm load when all things are taken into account. Used with a separate amplifier and new speaker wires, 2-ohm speakers provide a more optimum load for 99 percent of car amplifiers.

Is "True four ohms" a marketing gmmick? Hmmm...depends on how you define that. If it's a confusing term, then I'm sorry. I'd prefer that we just said "2-ohms", but I only have so much influence with our marketing folks.

emperorjj1 · 04-10-2008, 08:03 AM

lol ya i guess i know how it is but the whole "true four ohms" thing still makes me mad... i like selling infinity products and using infinity products myself and i completely understand the whole idea behind building a 2 ohm driver. I again prefer a 2 ohm driver for aftermarket amp installs as they will better max out a class A/B amp... it effectively means the consumer can buy an amp half the size.

Now i dont deal as much with SQ and mids amp installs as much as i would like but assuming im doing a factory swap with infinity Kappa drivers and a nice Xtant 404m mids amp. Even using the stock wiring where there is higher resistance then some of the other speaker wire options available im sure you can agree the mids can and will get plenty loud... if Infinity is worried about loosing a few db then notify all the dealers to stock spools of speaker wire and use it. For a $1k install im not going to cry over a few extra bucks in wire.

Overall i dont have problems with the product but IMO the hype isnt nessicary. How long have you guys been making 2 ohm drivers... nothings new. I just hope infinity doesnt become the next MTX (you know what i mean) and hopefully ill never have to think of infinity on that level