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Easy Spec Check

72.224.232.198

Posted on December 7, 2020 at 14:11:25
Posts: 885
Location: Maine
Joined: August 16, 2011
Hi,
Just got the new Stereophile.Without even reading the reviews my eyes went right to John Atkinsons graphs.
The Acora Acoustics SBB's frequency graph on page 66, Fig.3 looks like a camel's back.I know their granite and cost 15 grande without stands.
The KEF LS50 Meta's graph,page 117,Fig.4 looks like Johny Unitas's flat top and those go for !,500.I know there made in China,but they are KEF.
I don't know what your ideas are on that but it does raise a Hifi flag with me...take care Mark Korda.

 

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Long-established, engineering-based manufacturer vs. small hobbyist-gone-to-the-dark-side upstart, posted on December 8, 2020 at 13:31:08
Brian H P
Audiophile

Posts: 765
Location: Oregon
Joined: December 18, 2012
KEF has a long, history of innovation, research, and development, and the facilities, resources, and knowledge to design just about any frequency curve they would want into their speakers. What they want, obviously, is maximum fidelity to the source signal: the most neutral and accurate on-axis response possible, along with low distortion, low cabinet resonance, and excellent off-axis dispersion. Priorities they share with Revel, Dynaudio, and other science-oriented brands.

Acora is a new, small manufacturer which seems to be focused primarily on one design feature -- non-resonant granite cabinets -- perhaps to the neglect of other aspects such as proper crossover design. JA's measurements show a lack of baffle step compensation, a large peak in the critical range centered around 900Hz (due to internal waves reflecting back through the woofer cone, because of inadequate internal damping?), and a the sort of goosed-up treble response that has become all too common these days. One can infer from this that the speakers will sound overly lean in the bass unless placed close to a wall, and have a strong (even "shouty") midrange emphasis and a bright treble response. Subjectively, this will result in a sound perceived initially as "fast," "lively," "exciting" (Ms. Mullins uses similar terms in her review), but which is ultimately likely to become stressful and fatiguing. She says something about how they engage "active listening," which is another way of saying you can't really relax and get comfortable with them.

The Acora speakers feature wonderful Scan-Speak drivers in wonderfully non-resonant cabinets, but perhaps could benefit from a more competent crossover design. At their price -- about 10x that of the KEFs -- they deserve it. Their "eccentric" voicing may please a few ears initially, but ultimately may limit their appeal. No question I would choose the KEF in a heartbeat.

 

RE: Long-established, engineering-based manufacturer vs. small hobbyist-gone-to-the-dark-side upstart, posted on December 8, 2020 at 14:04:40
pictureguy
Audiophile

Posts: 13495
Location: SoCal
Joined: October 19, 2008
Just a spitball here......I have NOT heard the Acoura speakers.

But it occurs that a company without access to some very Expensive items, like an Anachoic chamber or who knows what else, may USE a review to gain knowledge of their product. Stereophile has both a large background in speaker measurement but also keeps their equipment used fairly current....

Treat the review as a 'reality check'.

I'd expect a 'Mark II' version of the Acora with some substantial modifications. Maybe fix that crossover? Reduce that 900hz peak, maybe?

It would appear they have some fundamentals 'right' but maybe need some voicing help as well as maybe some crossover assistance, too?
Too much is never enough

 

Agreed. The Acoras are potentially wonderful speakers., posted on December 8, 2020 at 16:06:16
Brian H P
Audiophile

Posts: 765
Location: Oregon
Joined: December 18, 2012
Superb drivers and beautifully made enclosures. Need some work on the crossovers (it certainly shouldn't be hard to wrangle a more acceptable response from ScanSpeak drivers!) and probably some lining/stuffing to reduce internal reflections.

They would still be a limited-availability specialty product from a small manufacturer, built with expensive materials and methods, and therefore necessarily costly, but with a less "eccentric" frequency balance could perhaps have wider appeal among well-heeled audiophiles.

Anyway, congrats to the designer for the heroic enclosures. I do wish him success, as the stone cabinet approach has much validity.

 

RE: Agreed. The Acoras are potentially wonderful speakers., posted on December 12, 2020 at 07:39:25
Posts: 885
Location: Maine
Joined: August 16, 2011
Hi Brian and Picture Guy,
I finally read the article on the Acora Acoustic SRB by Julie Mullins.She does a great job but I would like to add some stuff.Julie says that granite is well damped.I worked with granite for 4 years.Some as a tombstone installer and then making and installing golf course hole markers.I've been in many family vaults made out of granite.The sound is not damped in there,it bounces.I don't know what Acora uses for internal dampening but it's got to be good and alot.
The different sides and top and bottom with the enclosure might have individual resonances.Acora said they are joined with an epoxy.Epoxy hardens like a rock.When we would attach a granite headstone to a granite base,the part lying on the ground,granite too, we would use a non hardening but brutally strong stuff called Stone Set.It was just like modeling clay.My job was to roll up ropes of it to make a gasket (air tight) around the base onto which the headstone gets placed on.I had to break a gasket of a 90 year old stone and it was still pliable to my putty knife.That stuff was dampening, I can't see hardened epoxy as a good connector of granite parts.This may have added to the camel humps in the response as much as the blamed crossover.Just an idea...
Granite warps? thats a new one on me.
Black granite from Africa? Maybe thats why the high price of the Acora.The best and cheaper granite if not from Canada comes out of a town called Barre Vermont and other places in N.H.There are all sorts of different choices in the appearance of color in granite.It comes in any color as long as it's black.I know you were joking but that did die out with the model T and Henry Ford over 100 years ago.
I found Julie's description about different sounds she observed from different groups outstanding but I got the impression she wasn't going to sell the house to get a pair.
These are just some ideas from an old Granite Grunt who likes Dynaco speakers....thanks for listening....Mark Korda

 

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