@bobbooo
As I said the whitepaper you are fan of does not show any useful directivity measurements
, since it
only shows the tweeter up to 60° in horizontal dimension. Proper directivity plots show vertical und horizontal planes up to to 360°, like Neuman, Genelec and other professionals do.
Another example:
(taken from:
https://ggntkt.de/en/model-m1/technische-daten/ )
The stereophile plots you are sharing again, do show that this Q-Acoustics is
not constant directivity (CD), since it is to narrow into high frequency. To achieve CD you have to use a waveguide, especially in a 2-way. This is why Neuman, Genelec, JBL and other professionals use a complex shaped front baffles, based on the findings of Toole/Olive/Harman.
My impression:
Q-Acoustics is not true evidence-based design. It seems that marketing dictates the form factor and aesthetics and Mr. Fink had to make the best of it. That's a different approach from aiming for the best performance from the very beginning.
As for the digital/active discussion:
I see no contradiction to my statement – if you strive for max performance you have to go digital and active.
I agree with a
@bobbooo and personally find the complaints levied against Q acoustics kind of odd. I like their speakers, so that's my bias.
We consider the majority of the Harman stereo portfolio to "evidence-based" yet they only publish measurements for a small minority of their speakers. If they do, it's usually pretty hard to find them. I don't think you can really sin Q acoustics for neglecting to provide that information given their speakers do, in fact, seem to measure pretty well within their price brackets.
I don't like the lack of detailed measurements either, but it would be far from the first time I've seen a hifi speaker with good measurements that are hard to find or non-existent.
With the exception of the flagship Concept 300, all of the company's bookshelf speakers cost less than $530 a pair. Somewhat ironically given your argument about directivity, I'd argue the strength of the $315 3020i and $500 concept 20 is actually how relatively well controlled their horizontal directivity is within their price brackets.
If you look at their measurements, the on-axis has a midrange scoop, but it largely remains consistent off axis, pointing to pretty good direcitvity control, and suggesting the dip can be at least partly EQ'd out if you want.
3020i:
Concept 20:
I think those are pretty good measurements for $315 and $530 a pair speakers, respectively. I only have vertical measurements out to 30 degrees for them, but within that window they seem about as well controlled as most of the other 2 ways I've tested.
The Concept 300 costs $4,500, which is pricey, but not at all outlandish by hi-fi standards, especially given it includes the fancy stands. It performs
quite well. It's not the cheapest speaker with such good measurements, but it's far from the most expensive. The KEF Reference 1 costs $7500 for
comparable horizontal measurements.
And as @andreaasman noted, constant directivity is just one way of designing speakers, and arguably not the best one. None of revels speakers are truly constant directivity as far as I know - that shows up as a level DI curve rather than a gently rising one.
In general, Dr. Toole seems to believe wider directivity is preferred to narrow directivity for recreational use at home (as opposed to for mixing engineers and some audio professionals who often preferr narrow directivity). In one part of his book he even suggests somewhat uneven wide directivity might be preferred to better-controlled narrow directivity (within reason).
Indeed, this is supported by the blind test that happened between the Revel Salon2 (wide directivity) and JBL M2 (constant directivity); the Revel won, despite having what I would consider slightly worse directivity (a dip around the crossover).
As for "striving for maximum performance" I also see
@bobbooo's point too: every speaker has design constraints. If we were always "striving for maximum performance," every speaker would have to be large enough to hit crazy high SPLs, cost a bazillion dollars, and likely sacrifice aesthetics along the way. I also prefer active designs, but sometimes passive is simple more practical or cost effective. This does not stop them from being evidence based. And again, Harman's blind test champion is a passive speaker is a passive one, not an active one.
Also, while cabinets are a big part of Q-Acoustics' design, I don't see them marketing their drivers as being anything fancy. They're seemingly unremarkable paper cones.
As far as I'm concerned, once you have decent frequency response and directivity and the price is reasonable, everything else is fair game. So if Q Acoustics wants to make its "hook" controlling resonances, so be it.
Even though I do tend to believe that resonances shouldn't be very audible if they don't show up in the frequency response, based on what
@Frank Dernie has said it seems Q Acoustics and others believe otherwise.
As a counterpoint to myself, while I wish Q Acoustics would correlate their work reducing resonances with blind tests, we know that the detection threshold low-q/wide-band resonances is incredibly low. So even if a resonance is not readily apparent in on and off axis frequency response graph, it doesn't mean it's not still audible. Per Toole, these are some detection thresholds for resonances.
I don't know about you, but a resonance like the one on the bottom right would be quite hard to spot in a frequency response graph.
Moreover, the above thresholds were determined in an anechoic environment, but he says resonances are likely to be more audible in a typical listening room because of the repetition.
So while we don't know just how much of an audible improvement reducing resonances in the hardware makes vs doing so in an active design, it's not hard to see why it can be useful to do so in the hardware like Q Acoustics does.