Infinity Kappa 462.5CFP Compound Driver
A 4×6-inch plate driver that DIY builders kept ordering in pairs - not because it measured flat, but because it measured interesting.
Overview
The Infinity Kappa 462.5CFP is a 4×6-inch plate compound driver, sold in pairs. It never really behaved like a component part. The catalog lists a nominal impedance of 4Ω, power handling of 60W RMS (180W peak), a frequency response of 75Hz - 21kHz, and a sensitivity of 90dB/2.83V/m, which works out to roughly 87dB/W/m. It is not shielded.
Those numbers look reasonable on paper. The measured response is another matter. Published measurements of four sample units showed a response that is neither smooth nor flat, with a notable droop from about 200Hz to 1kHz. That droop is part of the appeal. In a small enclosure it supplies a degree of diffraction spreading loss compensation that a builder would otherwise have to design around. The best listening axis sits about 20° off the tweeter centerline, toward the woofer, and that quirk shaped every enclosure design built around this driver.
The 462.5CFP is a compound plate: a woofer and tweeter share a single 4×6-inch mounting face. That made it useful for compact satellite builds, and awkward for anyone expecting a conventional two-way layout. AudioXpress (June 2003, p.61) noted that the driver's low driver count and the absence of a complex crossover requirement made it a natural starting point for simple satellite designs - at least in its unmodified form.
What Builders Actually Did With It
The most detailed surviving documentation of this driver comes from the DIY community that adopted it, not from Infinity. Published construction articles developed five small satellite types around the 462.5CFP, all prototyped as floor-standing designs, though stand mounting was possible with some. Box types #1 and #2 mounted the compound driver with the drivers side-by-side. Box types #3 and #4 stacked the woofer above the tweeter.
The side-by-side arrangement, as documented, produces a very wide sweet spot. Listeners reportedly could not agree on a winner between the two, preferring one or the other depending on the music. The side-by-side boxes, in unmodified form, were judged acoustically inferior to the stacked pair. With a redesigned crossover, they became fine-sounding satellites suitable for stands.
Two of the best-regarded satellite designs came out of major crossover redesigns on the 462.5CFP. Those redesigns pushed the builds out of the "simple and low-cost" category. Builders were warned not to run these nominal 4Ω systems below 100Hz.
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The Crossover Problem
The 462.5CFP is a plate driver, not a finished speaker, and that distinction matters more than it first appears. A compound driver of this type presents a builder with two radiating elements sharing one baffle cutout and one set of mounting holes — 4×6 inches, with the drivers mounted side-by-side or stacked depending on the enclosure. The trade-offs between those two arrangements are acoustic, not electrical, and they show up in the polar response rather than on-axis.
The driver's measured behavior — that 200Hz-to-1kHz droop, the uneven top end — meant that a straightforward first-order crossover was never going to extract the best from it. The published designs that used the 462.5CFP in unmodified form were, by the authors' own assessment, the weaker of the bunch. The better-sounding builds required a redesigned crossover network, which is why the "simple satellite" framing only held for the entry-level versions. Once you committed to a proper crossover, the cost of parts climbed and the project stopped being a budget exercise.
Reception and Practical Notes
Contemporary coverage of the 462.5CFP treated it as a driver of opportunity rather than a polished component. Its response was not smooth, and the documentation says so plainly. What it offered was a packaging format — the 4×6 plate — that let builders put a two-way system into a very small box without cutting two separate holes and without designing around a large baffle step. That is a real engineering convenience, and it is the reason the driver kept appearing in satellite designs long after its measured curves would have disqualified it from a conventional two-way project.
The unshielded construction is worth flagging for anyone considering these near a CRT display or in a home-theater context; the documentation is explicit that these drivers are not shielded. The 4Ω nominal impedance also means they present a demanding load, and the recommendation against running them below 100Hz reflects the reality that this is a satellite driver, not a full-range solution.
For collectors and DIY builders today, the 462.5CFP is a niche item. It shows up as loose pairs rather than as part of a finished Infinity speaker, and the people who want it tend to want it for a specific reason: they are building or repairing a small satellite design that was documented around this exact driver. The published construction articles remain the best reference for anyone attempting that, and they are candid about the driver's limitations as well as its usefulness.