Although I’ve been critically listening to speakers for almost 30 years, I’ve listened and measured for only the last two. I take my own measurements in my home listening room, and help out with measuring the speakers we review in the anechoic chamber of Canada’s National Research Council (NRC), here in Ottawa.
An in-room frequency response (FR) measures the combination of the direct sound of the speakers and of the reflections of those soundwaves in the room. However, as its name implies, an anechoic chamber is treated to eliminate all echoes, resonances, and reflections of any sounds generated in it, so that the frequency response measured is only that of the speaker. From doing all of this measuring and listening, I can now look at a speaker’s FR measurements and get a pretty good idea of whether or not I’ll like that speaker’s sound -- or, after listening to a speaker, I can very roughly predict what the plot of its in-room FR will look like.
For this article I focused on two budget speakers I recently reviewed, and whose sounds I liked and found similar. I wanted to see if I could correlate their measured in-room and anechoic FRs with what I heard in my room. Both speakers are made in France, and are relatively inexpensive, two-way minimonitors; they have drivers of similar sizes and cabinets of similar volumes, and both have been named SoundStage! Reviewers’ Choices: the Focal Chora 806 ($990/pair, all prices USD), and the Triangle Borea BR03 ($549/pair).
Diego Estan with the Focal Chora 806 (left), Triangle Borea BR03 (right), and Focal Sopra No1 (behind right)
I helped measure the Triangle Borea BR03 in the NRC’s anechoic chamber before I took them home to listen to. SoundStage! founder-publisher Doug Schneider insisted I look away when the FR plots appeared on the computer monitor, to keep my home listening unbiased. A few days later, when I’d gotten acquainted with the Borea BR03s’ sound in my room, I measured their in-room FR and saw that the plot presented at least one reason I so liked this speaker: a distinct rise in the presence region of the midrange (500Hz-1kHz), which I say more about below. I called Doug to ask if the NRC’s measurements agreed with my own through the midrange, and he told me that they did.
With Focal’s Chora 806, it was the other way around: I’d become familiar with its sound and taken my in-room measurements before we measured it at the NRC. When I’d first heard the Borea BR03s in my room, I was reminded of the Choras in ways I’ll explain below, which is why I’ve lumped them together in this article.
For each of these pairs of speakers, I took nine measurements at and around the sweet spot position of my listening room, all within 2’ of each other, and averaged them into a single plot. I used my calibrated miniDSP UMIK-1 microphone, connected to a Microsoft Surface Pro 6 laptop running Windows 10 and Room EQ Wizard.
The first measurement is always taken at a point in space precisely between where my ears are when I sit down to listen. I take multiple measurements partially to account for head movements and, more important, to accurately characterize the bass. In most domestic listening rooms, somewhere between 200 and 400Hz is what’s called the Schroeder frequency -- i.e., the frequency below which the bass experienced by the listener is dominated by the interaction of the woofers, their positions in the room, and the room’s size and shape and furnishings, rather than by the design and shape, etc., of the speaker itself. And because we sense deep bass not just with our ears but with our entire body, and because moving the measuring mike even 1’ can result in a very different bass measurement due to the room’s bass modes, it’s best to average several measurements at and around the listening position, to better represent what you’d hear and feel in the lower octaves of the audioband.
The plot below averages my in-room measurements for the Focal Chora 806es (red line) and Triangle Borea BR03s (blue line). Before I describe the correlation of these plots with what I heard, as well as what I heard that these plots don’t show, I’ll first state the obvious: These speakers’ measured FRs are very similar. It’s no surprise that, on the whole, they sounded similar to me.
Not only are these speakers’ measured FRs close -- so are their measured sensitivities, or how much power is required to drive them to a reference volume level. I measured both at the same volume-control position -- the plots above have not been normalized in any way. As you can see, below about 1200Hz the volume levels of their outputs were about the same; above that frequency, the Focals’ output was about 2 decibels (2dB) less the Triangles’, which reflects deliberate voicing decisions in the two designs.
The charts below represent the Listening Window measurements we conducted in the anechoic chamber of the NRC.
The Listening Window comprises an average of five FR measurements taken at these positions: on the tweeter axis (i.e., with the measuring mike pointed directly at the tweeter), 15° to left and right of the tweeter axis, and 15° above and below the axis. In an anechoic chamber, the bass is pretty much the same at all mike positions, because there are no room bass modes to affect them. Instead, we take multiple anechoic FR measurements mostly for the same reason we take multiple in-room FRs -- to account for subtle differences in ear positions due to head movements, and to smooth out small problems created by the diffraction by the speaker’s baffle, to get an FR more indicative of the midrange and high frequencies than a single on-axis FR would be.
Triangle Borea BR03 Listening Window
Focal Chora 806 Listening Window
The Listening Window is also the measurement we use to derive our sensitivity figure, by averaging the speaker’s output from 300Hz to 3kHz. The Borea BR03’s sensitivity turned out to be 86.93dB, and the Chora 806’s was 87.0dB -- almost identical, and correlating well with what I heard in my listening room.
In-room and anechoic measurements compared
As I explained, you can’t expect any sort of agreement between the measurements of a speaker’s in-room and anechoic FRs below the Schroeder frequency, where the sound is as much a product of the room as of the speaker itself. Not only will in-room measurements reveal the bass modes -- peaks and dips in the FR -- produced by any real-world listening space, and which an anechoic chamber is specifically designed to eliminate entirely, but in-room FRs also show room-boundary gain. This is an increase in the speakers’ output of 3dB or more, depending on the room’s size and how close the woofers are to the walls. Bottom line: In a real-world room, a speaker produces more bass output than that same speaker can produce in an anechoic chamber. My in-room measurements show a -3dB point for both speakers in the low 30Hz area, while the anechoic measurements yield -3dB in the 60Hz area. That extra 30Hz or so of bass extension is due mostly to room-boundary gain.
Also visible are similarities in the speakers’ midrange and treble responses in the in-room and anechoic plots. Both show rises in the midrange between 500Hz and 1kHz, although in the anechoic plots this is far more predominant for the Triangle than for the Focal. In terms of treble, the in-room and anechoic plots agree that the Focal produces less output between 4 and 12kHz than does the Triangle. This lower HF output should mean that the Focal sounds less trebly than the Triangle.
Correlating listening with measurements
Did what I hear from these speakers correlate well with the FRs measured in my room and in the NRC’s anechoic chamber? Yes, no, and maybe.
Not wanting to rely on my own aural memories of what I’d heard in the listening I’d done for my reviews of the Focal and Triangle speakers, I listened to them again, playing the same tracks through both, and trying to keep the swaps between speakers to less than 45 seconds. I first listened to a perennial audiophile favorite, Jennifer Warnes’s cover of Leonard Cohen’s “Famous Blue Raincoat,” from her album of that title (16-bit/44.1kHz FLAC, Cypress/Qobuz). I thought the two speakers provided about the same degree of presence for Warnes’s voice, as I’d expected given their similar FRs from 500Hz to 1kHz. But the Focal Chora 806es’ reproduction of her voice and the saxophone was slightly meatier -- both horn and voice had more body, or richness, in the lower midrange. This might be explained by the extra couple dB of output in the Chora’s FR between 300 and 500Hz, both in-room and anechoic.
I also found that the Triangle Borea BR03s highlighted sibilance a bit more than did the Focal Chora 806es. This was definitely confirmed by the BR03’s extra 2dB or so of output between 5 and 8kHz -- precisely the part of the audioband in which sibilants occur, this difference visible in both the in-room and anechoic measurements. A benefit of that extra treble energy, however, was that the Triangles provided more “air” around Warnes’s voice.
In terms of transparency -- the feeling that voices and instruments are right there in the room -- both speakers were roughly on a par. However, an impression of aural transparency isn’t something easily measured. Severe cabinet resonances can cause FR deviations that nonetheless may not be easy to identify in an averaged measurement such as the Listening Window. Rather, measurements of a speaker’s total harmonic distortion (THD) can partly explain its ability (or not) to convey a sense of transparency. Speakers that tend to sound very transparent typically have very rigid cabinets and drivers that behave linearly, which usually translates to very low measured THD. This means that, quite often, expensive speakers with very rigid cabinets and well-engineered drivers have very low THD and sound very transparent. Thankfully, at the NRC we measure speakers’ THD.
My reference speaker, Focal’s Sopra No1 ($9990/pair), is a good example -- it sounds more transparent in my room than either the Chora 806 or Borea BR03, and sure enough, the Sopra No1’s measured THD is lower, as you can see below:
Triangle Borea BR03 THD
Focal Chora 806 THD
Focal Sopra No1 THD
For those unfamiliar with reading a THD plot, the upper trace in each graph is the output of the speaker across the audioband, in dB; the lower trace is the level of distortion, also in dB. The more THD a speaker produces, the higher the lower trace will be, and the more audible that distortion will be. All three measurements were taken in the anechoic chamber at an output level of 90dB, and with the measurement mike 2m away. Above 150Hz, the Sopra No1’s THD is essentially below the threshold of what the NRC’s measuring hardware can detect; the Chora 806 and Borea BR03 show audible distortion artifacts some 30-35dB below the signal.
Next, I listened to a track with solid bass content: “Home,” from Michael Bublé’s It’s Time (16/44.1 FLAC, Reprise/Qobuz). Here, what I heard did not correlate with my measurements of the speakers’ in-room FRs. What you’d expect from the data is the same bass performance, but the Focals sounded as if they were delivering just a bit more extension in the bass than the Triangles, as well as bass that was fuller and rounder.
What I heard in the midrange repeated what I’d heard with the Jennifer Warnes track -- through the Focals, I heard the same extra body in Bublé’s voice and reduced sibilance. This time, however, because Bublé’s range is lower in pitch than Warnes’s, I found the Chora 806es at times bordering on sounding too chesty (i.e., a bit too full in the lower midrange), which I didn’t hear with the Boreas. I see nothing in the measurements that would account for that. Still, both speakers offered the same forward, intimate midrange sound, as well as soundstages of similar width, depth, and height, and effectively equal precision of aural imaging. All told, I preferred the Focals’ sound, if only for the richer midrange, and despite the intrusion of that odd chestiness.
To evaluate bass extension, speed, and punch, I turned to “Run-Around,” from Blues Traveler’s Four (16/44.1 FLAC, A&M/Qobuz). While the two pairs of speakers sounded extremely close, the Triangle Borea BR03s had the edge in terms of speed, rhythm, and punch, the Focals in terms of fullness and extension. The Triangles’ bass seemed to hit my chest with a hint more impact, and to recover more quickly after each bass note. The Focals provided a hair more rumble through my listening chair -- I could feel, in my body, more of each bass note’s sustain. These listening impressions weren’t confirmed by my in-room FR measurements -- the speakers’ bass outputs look too similar -- but I heard what I heard. It’s possible, however, that more and/or different measurements might explain these differences.
Last, I wanted to focus on the quality of the speakers’ reproductions of the treble. I’ve already mentioned that the Triangle Borea BR03 emphasizes sibilance more than does the Focal Chora 806; the Triangle also sounds, overall, a bit brighter than the Focal. Those differences are clearly represented by the in-room and anechoic FR measurements: both show the Triangle’s treble as being more elevated. But what about the shimmer, delicacy, extension, and decay I heard -- that is, not the treble’s quantity, but its quality? Which speaker is better, and is that judgment confirmed by the measurements?
I played “Black Velvet,” from Alannah Myles (16/44.1 FLAC, Atlantic/Qobuz), and focused on the cymbal crash at hard right at 0:49. This is where the extra $441/pair for the Focals pays an audible dividend. The Chora 806’s aluminum-magnesium tweeter is very good, and can easily compete with the tweeters of far pricier speakers; the Borea BR03’s silk-dome tweeter I don’t know as much about. From the Focals I heard more delicacy and shimmer, and what felt like longer decays; the Triangles sounded a little tizzy by comparison. The Chora’s tweeter sounds like very fine sand sifting through my fingers; the Triangle’s tweeter sounds like coarser, grittier sand.
Is there a measurement I can take that would reveal these differences in the two tweeters’ sounds? I’m not sure. I could point to the Triangle’s higher measured THD (above) than the Focal’s between 5 and 10kHz, but I’m not sure that explains it. But I’m also not ready to say that such differences can’t be measured -- it may require something more sophisticated, such as a spectral analysis of the pattern of harmonics in the distortion.
I’ve provided here a somewhat technical take on my experiences with two budget minimonitors I’ve recently reviewed and really liked. I’ve attempted to correlate what I heard with what I measured at home, and with what Doug and I measured in the anechoic chamber of the NRC. In these speakers’ reproductions of the midrange and high frequencies, the correlations between the heard and the measured were clear; however, the audible differences I heard in other areas, such as the bass, escaped the capabilities of the measuring gear.
Will I ever be ready to buy a loudspeaker based on specs and measurements alone? I doubt it. Staring at graphs isn’t as much fun as sitting down in the sweet spot to listen, but I do think that measurements, even if they can’t tell you everything, can at least tell you some things about a speaker’s sound. And the more I learn about them, the more those measurements might tell me.
. . . Diego Estan