Metal cabinet speakers

kenjit, it is easy to build passive cross overs. First class parts are ready available and the math is not that complicated but unless you stay first order phase coherence and efficiency matching drivers with various impedance curves without adequate test equipment is virtually impossible. The easy way around this is to use active cross overs and bi or tri amp. My favorite way of making a very high quality system for friends with a limited budget is to make a D’Appolito array using two 6” drivers up an down from a dome tweeter on a plate sandwich of MDF and solid surface material. I’ll use a simple 6dB/oct cross over and tweak it measuring the frequency response until I get it reasonably flat. Then I’ll cross over to subwoofers at around 125 Hz. You can mount the plates on stand but my favorite stunt is to hang them on chains.

It looked like the ProAc K8 has a metal structure. I found out when I had to remove a bass unit  to replace a broken speaker wire terminal. 

As Erik_Squires noted, Celestine SL600 and SL700 had cabinets made from Aerolam. Two sheets of aluminum with aluminum honeycomb in between. Adapted from aerospace industry. Inert and light in weight and thin allowing a relatively large internal volume. But very expensive and, therefore, used only in small speakers. 

From the AudioMachina website,

“AudioMachina XTAC Master Reference System is designed and manufactured to the very highest and most uncompromising standards in every way, from the smallest parts to the meticulously perfected layout to the manufacturing process to the final finished product. All enclosures are precision CNC machined, in our own manufacturing facility, from 100% aerospace-quality solid Aluminum Block. The XTAC Amplifiers are each made up of solid precision machined blocks, and the XTAC Speaker Modules represent, to our knowledge, the most advanced cabinet design ever achieved in the history of the world: Each XTAC Speaker Module is precision CNC machined, inside and out, from only one solid block of solid Aluminum. Yes, you read that correctly: The XTAC Speaker Module cabinets are one single piece of solid machined metal, with no joints, no separate pieces, no hardware to bolt those pieces together, or anything else that would reduce the insane stiffness, strength, and inertness achieved by making them out of a single solid block of metal. This is but one example, out of dozens upon dozens of examples, all leading to the same conclusion: The AudioMachina XTAC Master Reference System is so far beyond any other loudspeaker ever made, in so many ways, that there is simply no comparison.”

Bad rap MAGICO dude they sold over 750 pairs of A3s as many people love lifeless sounding speakers.The reviews are great because the speakers are great!!What do you have???