What’s in a shape?

QLN Signature 3 Bookshelf Speakers; Walnut Pair

One of the best hifi forum pejoratives I've seen is the term “cone-and-dome monkey coffin,” used to denigrate a standard mini monitor type of speaker design.

If you’re presently looking at a set of these, as I am, you can try to imagine an old monkey who lived a long and happy life, laid to rest by his monkey descendants and lowered into the earth entombed in an adorable, BBC-licensed, LS3/5a cabinet.

Why is a BBC monitor shaped the way it is? Why are these mini QLN monitors shaped like a trapezoid instead? Did the BBC scientists miss something that QLN did not?

I’ve noticed trending waves of unique looks, each of which seem to concern a group of companies for a period of time, all throughout the history of audio. First you had Electro Voice and the giant cabinets like the fridge-sized Patrician dominating homes. Years later, Klipsch popularized the corner horn approach, and by the end of that trend, Klipsch had some healthy competition in the corner-speaker game.

In the ‘70s, you had the East Coast Sound, and the Western counterpart. The east coasters all looked the same (sealed, big woofers and dampened paper domes), as did the west coast speakers (horn on top, PA woofer below).

There was a brief era of mega line arrays, ALA Beveridge, Genesis, Infinity, McIntosh and others (McIntosh is still at it).

Then there was the BBC monitor craze. And the monkeys rejoiced.

More recently, there’s been this “trapezoid on top / tall bass reflex bin on the bottom” kind of thing that describes Watt/Puppy and Genesis V and quite a few others.

Where was I going with this?

There are very specific reasons each of those speaker designs looks the way it does. The BBC monkey coffins are small enough to hold a monkey, because they’re focused on midrange clarity and transparency so they utilize a small midbass woofer. And the small midbass woofer needs a small monkey coffin-amount of air behind it to correctly pressurize the cone.

The actual dimensions of the box follow a “golden ratio” which minimizes the parallel, opposing sides ability to form internal sound-ruining standing waves. The golden ratio does a good job, but there are other approaches that work a tad better, like this approach from QLN.

Looking at these beautiful cabinets we can see that the only parallel walls are the top and the bottom, and if I had to guess I’d say the perfect spot for a cross brace inside would be also perfect for diffusing that tiny standing wave. Even without a brace, the slope of the front puts the driver baskets in the way to diffuse the wave, and the intrusion of the port from the back does the same.

Further, the trapezoid allows for a taper, bottom to top, meaning the front baffle is not much wider than each of the drivers themselves. This, as you might know, is fantastic for supporting a vibrant stereo image. Lastly, a reclined front baffle actually vertically aligns the centers of each driver’s motors. As they receive the same music at the same time, they launch their waves together, resulting in improved coherency.

Well-designed speakers deliver refined sound. As you explore the various approaches to discover your preferences, try to dig into the “whys” of the design and see what resonates with you.

These QLN cabinets may be inert due to constrained-layer cabinet construction, but they are resonating with me. How’s that for an audiophile joke. :)