Infinity Primus P363 Loudspeaker

Equipment report
Infinity Primus P363
Infinity Primus P363 Loudspeaker

How well a speaker has to work to be satisfying is not an open-ended question. Eventually, speakers will get to be as good as there is any use in their being and when that happens, technological progress being what it is, it will not be long before they are as good as they can be at low prices.

People ought to rejoice in this, not resist it. Music is for everyone. But however one feels about the idea, in the face of speakers that cost tens or even hundreds of thousands of dollars a pair, the whole point might seem very remote at present.

“And then along came Jones”—or in this case, the Infinity Primus P363—and suddenly the idea seems a lot less remote than before. There have been other inexpensive speakers that were startlingly good. Several times in the history of TAS one writer or another has declared some inexpensive speaker to be good enough or even all but perfect (I recall an early NEAR speaker for example, and Harry Pearson’s reaction to the Sound Dynamics 300ti). Nor am I going to suggest that the Infinities as I shall call them hereafter are perfect. They are built to a price point and there are things one could do a little better by spending more on construction. Indeed, there is a sort of cottage hobbyist industry flourishing of people modifying these speakers for themselves or others.

What I am suggesting is that these speakers are both remarkably good and remarkable in the rationality of their design. Infinity has apparently isolated the things that really count about sound and gone after these things while cutting corners—corner-cutting being necessary at the price—in ways that do not matter all that much. The results are startling indeed.

These speakers are very inexpensive. They are four-driver, three-way floorstanders. And they are currently being offered for sale quite frequently for under $300 a pair. (Their MSRP is higher but they are being heavily discounted.)

I am well aware that if I just start talking about the sound—although Neil Gader described a somewhat earlier version of the speakers as “amazing” in his capsule review in a survey in issue 149—people are likely to think that this is just REG being an iconoclast or an agent provocateur, doing for speakers what he tried to do for phono cartridges years ago with his review of the Audio Technica ATML170.

The Technical Story
So I want first to tell you about the technical behavior of the speakers. Lots of you probably think that speaker sound is not well characterized by measurements, but bear with me and perhaps we can clarify this point a bit along the way.

Let’s start with distortion. For all practical purposes, the Infinities do not have any. The distortion is on the order of 55dB down from the signal from 100Hz on up at 90dB (this 55dB down corresponds to around 0.3% or less). The Canadian NRC’s famous speaker-measurement program does not even bother to show in its distortion measurements distortion levels that are more than 45dB down. They clearly think below that level, distortion is inconsequential. On this basis, the Infinities are essentially perfectly “clean,” truly distortion-free. The Eminent Technologies and most electrostatics are even a little lower—maybe 60dB or more down from signal or in the case of the ETs even better at many frequencies. But the Infinities are running about as well as a box dynamic speaker is likely to run in this regard and better than most. And they sound it. The Infinities are really clean and pure-sounding. You want clean midrange; they give you clean midrange.

Next act: The Infinities are really flat in response. Now here one has to be a little cautious. They are not absolutely as smooth in the midband as some speakers that run a single driver from the bass on up to say 3kHz. The Harbeth P3ESR is smoother from say 300Hz to 1kHz, for example. But not by much! The Infinities have a very smooth, neutral midrange, and the very small measured variations around 600–800Hz are just that, very small.

Now what is true is that, to my ears, the whole region above around 1kHz could be pulled down by about 2dB to good advantage. As is, the speaker sounds a little midrange-recessed relative to the upper mids and lower treble, above which response is very smooth and flat but slightly up in level. Many audiophile speakers are, in fact, midrange-forward, so this small recession effect may strike you more than it really should. In any case, such a small reduction of the treble is a trivial thing to do electronically. (Buy an NAD and the controls will be right in front of you.)

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