Thanks for the link.
I started reading the review and quickly stopped. The reviewer, Julie Mullins, said things right from the start that brought me to a full stop. (I marked in bold some of her comments that I find objectionable. Those who read on, will no doubt, find other equally objectionable comments.)
I'm a sucker for materials, whether it's finishes for loudspeakers and other audio equipment, a shoe's fine, supple leather, a crisp cotton shirt, or a cozy cashmere scarf.
Apart from their inherent sensuousness, materials can make a difference in the sonics of audio components, especially loudspeakers.
Exotic wood enclosures are old hat. Carbon fiber isn't exotic anymore. Glass seems an odd choice for a loudspeaker enclosure—but that's the choice made by Perfect8 speakers, which I encountered at T.H.E. Show in Newport Beach a few years back. And then there are the Jörn speakers from Denmark, which are made of iron; America's OMA uses iron, too, in some of their designs. Fischer & Fischer uses enclosures made of slate.
I quickly skipped to the Measurements page. Right away, I saw John Atkinson said some unexpected things:
My initial measurements were performed on one of the original samples auditioned by Julie Mullins, serial number TIB0010. After Acora found out that the first samples had been incorrectly assembled with the tweeters wired in the wrong polarity, which resulted in a massive suckout in the crossover region [3,000 Hz], they submitted new samples. I performed a complete set of measurements on serial number TIB0021. Except where noted, all the following comments apply to the new sample.
Wiring a tweeter with the opposite polarity is an easy mistake to make – for an inexperienced DIY amateur. I've made that mistake myself, once and once only. Acora, a commercial speaker maker, did that. And it was with speakers that it sent for a review by Stereophile!!! That's beyond amateurish, it's dumb. I already dumped on the reviewer, so I'll avoid piling on. But I wonder what she said about sound in the crossover's range. Others can feel free to look for any further nonsense in her review.
Atkinson next says things about the cabinet resonance that TLS Guy already pointed out. As I've grown to expect from Atkinson, he minimizes any audible effect they might have. I think that large resonance peak in fig. 2 is UGLY looking, and will likely sound as ugly as it looks. But you wouldn't know it from Atkinson's words.
There are two very slight discontinuities between 700Hz and 1kHz in the traces in fig.1 that imply that there are resonances of some kind present at these frequencies. When I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I found a single resonant mode just below 900Hz on all the panels (fig.2). The use of a very dense enclosure material has pushed this resonance higher in frequency than is usually found in a conventional loudspeaker this size. Although the frequency of the resonance is close to that of the musical note B5, its Q (Quality Factor) is very high, which means it should not affect sound quality.
Atkinson said this about the port's output, the red trace in fig.3.
The port's output (fig.3, red trace) peaks between 40Hz and 100Hz, though the clean upper-frequency rolloff is disturbed by two high-Q resonant modes between 600Hz and 800Hz. As these twin peaks are low in level and the port faces away from the listener, I doubt they will have any effect on sound quality.
The second port peak at 800 Hz is close to the cabinet's resonant peak at 900 Hz. If they overlap, that will sound bad. I think it will be audible at higher volumes. It could be fixed by using a port with flared ends, or larger diameter.
Atkinson said nothing at all about the large peak centered around 900 Hz (fig. 3 black trace).
But he did point out the uncorrected baffle step response problem. However, he failed to say it will have audible results.
And, typical of Atkinson, he did point out the existence of the elevated (3-5 dB) tweeter response above 4,000 Hz, but dismissed it's effect on the speaker's overall sound. Saying that it "matched the level of the midrange peak" is unforgivable. That midrange peak is caused by unwanted cabinet resonance, something you do not want to hear.
The response, averaged across a 30° horizontal window centered on the tweeter axis, is shown as the black trace above 300Hz in fig.3. Though the response in the crossover region is flat, there is a broad peak in the upper midrange, which implies a lack of baffle-step compensation in the crossover. The tweeter's output between 5kHz and 20kHz is 3–5dB higher than it is in the presence region, almost matching the level of the midrange peak.
I could go on, but I'll go straight to his final comment about these speakers.
I was intrigued by the Acora SRB's use of a massive enclosure, but I was puzzled by some aspects of its measured performance.—John Atkinson
These speakers cost $15,000 per pair. I'd be more than puzzled by some aspects of its measured performance.
For fun & games, read the comments at the bottom of that page.
