Metal cabinet speakers

Just to be a completist, several makers of tiny speakers in the 70s and 80s used metal cabinets on at least some of their models, including ADS, Boston Acoustics, and, of course, Radio Shack’s Minimus 7 line (except the wood-cabinet 7W).

Nobody mentioned Piega Speakers from Switzerland

16v did, just a little upthread from your comment. 

Celestion SL600 and SL700 that have been mentioned are great speakers. I have heard both and use the SL700 myself. The 700 outperforms the 600 in almost every way.

The speakers have an efficiency of 82db for 1w and the impedance dives to below 4ohm below 100 hz iirc. They need an amplifier that can drive them with a lot of current but once you find the right match these speakers are magical (like with the Primare a30.2). I still have an old pair of sl6si (the cheaper mdf brother of the 700) that I connected about a month ago again to compare to the 700. Compared to the 700, the soundstage was blurry, vocals sounded coloured and the imaging was a bit all over the place, even though they're very nice speakers too. The aerolam cabinets are so quiet the image is just painted around the cabinet and very nicely holographic. I will cherish them for long I think.

Baltics far more costly than $40 a cab to build a speaker a 2x8 sheets $70 much more if furniture grade or veneered Aluminum is cheap to use once you set up to use it. Aluminum is about $1900 a ton birch ply more costly plus waist from ply is not able to be resold, unlike aluminum. It is far cheaper to paint then veneer ply, aluminum is light so you save on shipping costs. Why you see many home theater in a box and computer speaker systems using it. More to the design of a loudspeaker than cabinet materials I think focusing on such while overlooking the whole is self-defeating.

The cost of the (aluminum) cabinet is only part of the story. Take a look at the cross section of a Magico speaker and when you see all the bracing that is required, then you’ll see why they weigh as much as they do., and maybe why they cost as much as they do.