A new filing shows that Apple started working on effective speakers for the small space within the new 24-inch iMac from late 2019.
The new 24-inch iMac
If you've been around Macs long enough, then it's a given. The Mac mini has terrible speakers and the iMac has excellent ones.
The Mac mini's aren't so bad that you can't use them, mind. And the iMac's speakers are no match for a HomePod stereo pair.
But generally, this is the consensus of opinion about Mac speakers and the perception hasn't changed with the design of the new 24-inch iMac. Even though that chassis is now so slim that the headphone jack had to be moved to the side because that's the only place where there's room.
You don't redesign something so much without effort. You definitely don't get to redesign it and keep good speakers without a lot of people.
"Speaker Assembly" is a newly-revealed patent application, originally filed in December 2019. It lists 12 inventors, including the prolific Paul X. Wang. His previous work includes related a related patent application on bringing HomePod-style environment sensing to the MacBook Pro.
"Over the past several decades, electronic devices have drastically advanced in their functionality," says Apple in the patent application. "Computer parts have been miniaturized, while also increasing in the amount of performance they can deliver."
"The reduced dimensions of these various components may offer more efficient use of space," continues Apple, "[and] greater flexibility in the placement of components within a housing, reduced housing size and use of material, smaller device sizes, greater ease of transportation and use, and other options for device design."
Yet of course smaller devices and smaller space for components is not ideal for loudspeakers.
Detail from the patent showing an iMac and some internal speaker assembly
"One challenge is to provide integrated speaker assemblies that maintain a broad frequency range and desirable acoustic performance levels, while also having a reduced size," says the patent application.
Apple says that the key problems concern the "limited space available for a back volume," which it also refers to as "speaker volume" -- in terms of space, not loudness.
"[This] is the empty air space in communication with the speaker that can provide air to push against to prevent the speaker from being overdriven," continues Apple. "The acoustic performance in the low frequency audio range can be dependent on the back volume size."
There are also issues to do with power as a large speaker diaphragm in a small speaker volume space reportedly has to be significantly stiffer. "A stiff diaphragm can require more power to produce a desired output as compared to a more flexible diaphragm," says Apple.
After describing woofers and tweeters, and after detailing dimensions for some speaker systems, Apple's patent application gets down to the business of the iMac. It just doesn't use that name.
"In some examples, the display at least partially defines a first exterior surface of the electronic device," it says, "... and a distance from the first exterior surface to the second exterior surface is between 9 mm and 13 mm."
The 24-inch iMac is 11.5mm wide.
"The speaker enclosure includes a five-sided box configured to be sealed to the housing to define the speaker volume," proposes Apple. "A wall of the speaker enclosure can include a flexible portion configured to oscillate and a rigid portion at least partially surrounding the flexible portion..."
Despite not mentioning the word iMac once in its 14,000-word text -- nor even Mac -- all the patent application drawings show the new iMac design. The descriptions, though, are clearly intended to cover all possibilities, including a larger iMac, or another device like a MacBook Pro.
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