After fixing a few issues caused by his own creation, Stephen Dawson found the Klipsch PRO-180RPC in-ceiling speakers to indeed be a powerful option.

A typical loudspeaker has a sensitivity of 89dB for 1W of input, measured at 1m. Loudspeaker makers always use the ‘sensitivity’ specification, rather than the mathematically equivalent ‘efficiency’ specification. A cynic would suggest that is because loudspeaker efficiency is so very low, everyone would be shocked.

How low? For that typical loudspeaker, for every watt you pour into it, 0.995W are wasted as heat, while the remaining 0.005W becomes acoustic energy in the air. That is, its efficiency is 0.5%.

That brings me to Klipsch. Klipsch started as a US loudspeaker company back in the days when audio amplifiers were powered by valves, and few were lucky to own one capable of producing more than a few watts. So Klipsch made its speakers efficient. A version of one of its very first models, the Klipschorn, is still produced. Its efficiency is not 0.5%, but 20%. (That’s the same as 105dB sensitivity.)

Those reflections were brought on by the Klipsch PRO-180RPC in-ceiling speakers. When I cast my eye down the list of specifications I was startled to see a claimed sensitivity of 96dB (1W/1m). That works out to 2.5% efficiency.

What are they?

The Klipsch PRO-180RPC speakers are not inexpensive. But as we’ll see, they seem to be for people who want the sound quality of standalone speakers, but from speakers which are physically hidden. They come in the usual arrangement for ceiling speakers, but with a couple of differences. First, there are two magnetically secured grille options, both included in the box. One is round and the other is square. Both are paintable of course.

Secondly, the speaker comes in a two-part ABS frame. As with many installation speakers, they are secured conveniently from the front by means of arms which swing out and then clamp in as their front screw is turned. But unlike most, this is on a separate ABS ring. That makes for easier installation since this is quite light in weight. You put that in the 249mm diameter hole and wind in the screws about three quarters of the way. The main body of the speaker then slots over the four screw heads. You twist it to lock it in place and then tighten the screws all the way. To remove it, you only need loosen the screws a little.

Each unit has two drivers. The tweeter uses a 25.4mm titanium dome, while the bass/midrange is an 8” (confusingly converted to 161.5mm by Klipsch) unit with a cerametallic cone. I’m not entirely certain what cerametallic is, and Klipsch isn’t particularly forthcoming. It just says that it “exhibit[s] a very high stiffness-to-mass ratio and superb damping, resulting in a powerful, solid bass foundation”. Apparently, the cone is metal, but with the front and back subjected to a hard-anodizing process, arguably creating a kind of thin ceramic covering. The tweeter is suspended over the cone of the woofer by four arms, and it cannot be steered. There is a variant of the speaker called the PRO-180RPC LCR which has both the tweeter and the bass/midrange firing at a 45-degree angle. These cost $50 more per unit.

Klipsch didn’t specify the crossover frequency, although my measurements suggest that its around 1,900Hz. What is clear is that the crossover network is well made and elaborate, with two heavy duty resistors, two capacitors and two coils. The spring-loaded speaker terminal has holes large enough to accept even banana plugs, which means pretty much any speaker cable likely to be deployed. There’s a switch at the front to change the level of the tweeter by 3dB.

In Use

I got to experience ease of installation twice with one of these speakers. And got quite the surprise about just how loud they would go. Both were due to the failure of one of my wiring rigs. These are just adaptors I’ve knocked up to allow my usual cables, terminated in banana plugs, to be used with various speaker connections. I made larger holes in my sloppy chipboard box – it’s sloppy, largely unbraced, because few installations are going to have well-made baffles – and installed the speakers. And then I set the music to play, intending to run in the speakers for a few hours. Indeed, they ran through a whole album at quite a high level, with little amiss. Okay, there did seem to be some elements missing from the music, but I resolve to work out why later on.

Then I put on Liszt’s piano transcription of Beethoven’s 5^th Symphony at a very high level. The speakers seemed just a little stressed. Not bad, but I feared the modest amp I was using had perhaps run out of power. So I went over to turn down the volume, and noticed that all the music was coming only from the left channel. Fortunately, my worst fears – blown speaker, or blown amplifier channel – were not realised. It was just my lousy wiring. That also explained why some elements had been missed from the earlier music. Clearly they’d been in the stereo channel that wasn’t working.

So I pulled out the speaker. That proved very easy to do. I just loosened off the four screws by a half dozen rotations each, then rotated the speaker housing within the securing ring and pulled it straight back. I fixed the wiring and put the speaker back. Total elapsed time? Maybe two minutes.

Listening

I took Klipsch at its word regarding sensitivity, and used an old 30W per channel analogue Cambridge Audio stereo amplifier. This is still a fine sounding bit of gear. A Chromecast Audio device provided the signal.

Beethoven, as interpreted by Liszt and Glenn Gould, went back on once both speakers were working properly, and I have to say that the result was really quite extraordinary. There was a visceral feel to the strike of the hammers on strings as delivered through these speakers. I still had the volume up too high, but when I put an AC volt metre on one of the channels, it appeared that they were being fed only a couple of watts of power.

I moved on to Introducing the Hardline According to Terence Trent D’Arby, and lowered the volume a little. This time the speakers delivered a good, punchy bass line, albeit with no extreme depths. Where it did have depth was in a sound stage that would have seemed more appropriate for high quality bookshelf speakers. There was a smooth subtlety to the delivery.

With some early ‘80s synth pop – Ultravox and Visage – the bass rhythm was again strong and the music was up front, powerful and controlled.

Some people complain about metal-domed tweeters, preferring the alleged greater smoothness of silk or other fabric domed units. Hmmm. I tested this with the Alban Berg Quartett’s rendition of Schubert’s String Quintet. The strings were smooth and sweet and, well, silky.

A couple of measurements

So, 96dB sensitivity is a very bold claim for any home loudspeaker, let alone installation models. Remember, they don’t have the luxury of carefully designed enclosures to help them, and the horn loading of the tweeter is necessarily very modest. But they did seem to go loud. After I’d been running that Beethoven/Liszt piece for a while at levels peaking just short of 100dB at 1m, I felt the back of the 30W amp driving them and found it was only mildly warm. Which suggests that it hadn’t taken that much power to drive the speakers to those levels.

So I measured. I used 500Hz to 2,000Hz bandwidth limited pink noise to do the measurement, first setting the output to average at 2.83V. This test is less flattering than those normally used to specify home loudspeakers. Nevertheless, I got an incredibly healthy 94dB. That’s a good 6dB higher than what I’d normally expect from a pair of ceiling speakers. Which is to say, they require just 1W to produce a level for which most speakers would need 4W.

I also measured the frequency response of these speakers from up very close. My main aim was to see what they were doing with the bass, but found that the response was extremely smooth, from 57Hz up to 15,000Hz. The bass roll-off was gentle, down by 6dB from the 100Hz level at 47Hz. I could imagine a very solid bass performance from these speakers were they to be mounted in well-designed enclosures.

Conclusion

If there’s a problem with the Klipsch PRO-180RPC in-ceiling speakers, it’s that they may be overkill for some of the jobs they may be called on to do. But that means that they have plenty of capacity for both quality piping of music throughout a home and performing ‘height’ channel duties in an Atmos-equipped home theatre.