Metal cabinet speakers

I like the idea of a very strong inert metal cabinet. Besides Magico, Steinheim and T+A.. who else makes metal cabinet speakers?
I think a lot of companies have dabbled in metal cabinets but most don't stick with it.  Infinity did it with the intermezzo line and the Prelude MTS.  Thiel had a number of models - powerpoint 1.2, viewpoint.  ATC had a metal line for a while.  B&W had some metal boxes.  My Thiel 3.7s have aluminum baffles and an aluminum top.  
Do you think they move away just because of how pricey it is and how hard it is to manufacturer vs MDF ?
Genelec still does aluminium speakers. ATC did aluminium speakers for many years. Aluminium works well but I believe it is more expensive than mdf and 3 to 4 times heavier. Impractical for anything bigger than a two way monitor due to weight.

Advantageous material for cooling of heat sinks, good damping, naturally corrosion resistant and non magnetic. My six channel amp is extruded and billet aluminium and is extremely heavy (about 50 Kg) but would be even heavier if cased in thick steel!
I'd guess it doesn't provide enough performance improvement to justify the cost.  There are probably other areas where the money spent on metal cabinets can provide more performance.  The companies that moved away from it are capable of doing a lot of different things, have tried various materials, manufacturing techniques.  I'd guess it's more of a sales feature in cases where companies are making entire big square boxes out of aluminum.  Something to talk about that differentiates them from other brands.  
jon is right. Look what Magico has to do to quiet things down. These guys must love to do CNC machining. That would be the only reason to make speakers that way, YG also. Great speakers if you can afford them.
Wilson's solution of using composites to make individual small enclosures is a good one. MDF is just as good you just have to increase wall thickness and keep the enclosures small with rounded edges and flush mount drivers. Finding great drivers is easy the problems come in designing the crossover. 
Wilson's solution of using composites to make individual small enclosures is a good one. MDF is just as good you just have to increase wall thickness and keep the enclosures small with rounded edges and flush mount drivers.

Right. The problem with metals is they may look and seem strong to us while on a microscopic level they are actually vibrating and ringing like crazy. So they work great on one level because they are strong on that level. Being a lot harder than MDF they dampen macro-dynamics a lot less than MDF. Yet when it gets down to the microscopic level, well that is where the real action is because that is where you either get or do not get that spooky real degree of refined inner detail. 

This is why the future of speaker design is like everything else composites. With composites the vibration control happens at the microscopic level. No longer a continuous medium like all the alloys composites are a, uh, composite of different materials. As such they get both their strength and ability to transfer mechanical energy into heat at the molecular level. Combined with multiple small cabinets custom shaped to optimize each driver, its hard to beat.

Except that like jon_5912 pointed out, it has to justify the cost. Designing with composites is extremely expensive, especially in the beginning when almost everything goes in the dumpster because you don't really know what you're doing. The first Porsche Carrera GT was supposed to be impossible to make profitably from carbon fiber. Then it was supposed to be possible but only in a $750k car. Then it came out for less than a third of that. Its still not common construction but the technology is filtering down, and the same is bound to happen in audio.
Not sure but I think the Paradigm Personas are.

Finding great drivers is easy the problems come in designing the crossover
what problems?
You missed YG Acoustics, who make heroic metal cabinets.
Wilson Benesch has metal and carbon fiber cabinets. Very low noise
It has been out of production for ages, but don't forget the Celestion SL600 in Aerolam.
Agree with @millercarbon in part. What I’d add is that a carefully designed wood cabinet could be better than metal, but open baffle speakers are really the way to go IMO for several reasons and he touches on one important one that relates to metal.
Magicos are the most lifeless sounding expensive speakers I've ever heard. The idea of making a ringing speaker is hideously dim. The idea of paying writers to tout them obviously not so dim.
@shadorne stated Genelec does make many different models out of aluminum. I own a pair of Genelec 8350A's that I adore. The use of metal also allows for speaker designers to work with a material of great rigidity. The cooling effect is also a plus. On the con side, cost and weight.
Karl Shuemann who used to frequently offer valuable posts here on Audiogon before opening his AudioMachina line, has made some very interesting speakers, some of which use metal cabinets.
Mike Lenehan of Lenehan Audio in Australia, uses differential bracing including 6mm and 4mm sprung steel plates inside his ultra high end loudspeakers. Connected electrically to the ground terminal, as a ground plane. (I suspect also acts much like a Faraday Cage as well.)
He also uses depending on the outright high end models, cast iron rod as well as silicone filled rigid copper tube bracing (due to it's high Young's modulus). Which is why he uses very pure copper screws to secure the drivers in his all of his two way speakers. To help alleviated ringing of the spiders on the drivers against the baffle.

I have even heard a pair of his standmount speakers with an external crossover, and the cabinets were lined with 4mm solid copper plate.

Curious recording studios in LA and NYC learning of his achievements have enquired and purchased his nearfield monitors to satisfy their curiosity after being informed; immediately ordering a second pair for another studio room after verifying the reviews.

In a sea of well advertised audio equipment, his speakers are a well hid pot of audiophile gold. I worked for Mike and still own two pairs of his speakers, after giving my brother an older model, and selling my first pair to help pay for them.

I have built them myself, and I would welcome anyone who may be interested why they out perform speakers costing more than 10 times their cost. Real science, why it's superior and not salesman hyperbpole.

The benefits of metals in an enclosure are real, so long as you can also account for the limitations. Even metals have a resonant frequency, attenuating the ringing of metal is also why it benefits being laminated to another material.
Definitive Technologies Mythos STS. Aluminum cabinet with a granite base.
The idea of paying writers to tout them obviously not so dim.

And they paid extra for all these reviewers who dumped their Wilsons and got Magico instead. Really dim :-|
Aluminum is an ideal material for loudspeaker enclosure. Very stiff, low energy storage, and therefore easily dampened (most of these cabinets are well damped). If you ever knocked on a Magico or YG, you know that they are as inert as cement. 
@anotherbob I think the mythos is MDF... but does have a granite base.

@sciencecop Thats what I suspected. Maybe thats why Magico is so loved?

@mtdining Have you heard the MK2 series or M series? The M2s really impressed me. They sounded super detailed but still musical.
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??? 
Paradigm Persona’s are not metal. They are wood composite. 

Also, different metals have different damping factors. There are far too many variables to make any judgement on this. 
I did a tour of the YG facility and their process was super impressive, and the speakers did sound great. They CNC all their own parts/drivers/cabinets out of 2" thick aircraft grade aluminum.  No parallel surfaces, double walled cabinet construction. Apparently it takes 120 hours of CNC milling for them to make a single pair of Sonjas.
Post removed 
@mijostyn, A D'Appoltio Array uses a 3rd order cross-over not a 6dB 1st order cross-over.
I had a set of the Celestine SL600 with the honey comb cabinets and they did some things quite well. but huge power pigs.  had an amazing midrange not so great in the extremes as modern speakers but very musical and engaging if I remember correctly.  but wow needed a lot of power to wake them up 
I have Focal CMS 40 monitors on my desk. Aluminum and very heavy. They don’t resonate and add sound/ambiance like an MDF or plywood box does.

Having said that, a resonate box can be very enjoyable. I love Harbeth and Rega mini monitors. 
Unsound, I am only referring to the positioning of the drivers. Done this way the drivers are acting acoustically as one driver through the entire pass band, an almost perfect point source. Whether or not you use a 1st, 2nd or 3rd order cross and where you put it depends on the physical size of the tweeter as you want to keep the mid/woofers as close together as possible, the upper frequency limit of the mid/woofers and the lower frequency limit and power handling of the tweeter. If you choose the right drivers you can get away with a 1st order cross and still maintain the point source characteristics of the array. It does limit your choice of drivers generally to more expensive ones but it makes life much easier and guarantees a phase coherent speaker. The dipole plate design eliminates enclosure resonance and improves integration with the room acoustically. Placed at shoulder level these little speakers sound really big. With your eyes closed you would swear you were listening to big floor standers. 
If you have access to a CNC mill you could even make the plate out of aluminum.
@unsound Not a metal cabinet, but Coincident has used d'appolito arrays and first-order crossovers in some of their speakers...

Speaker features:  "1.The D'Appolito alignment is optimally applied to midrange/woofer drivers no larger than 5.25" in diameter. Any larger mitigates against the optimum spacing between the midrange/woofers and the tweeter, (as measured from the driver centers).
2.First order crossovers are essential to maintain perfect phase relationships and time constants."
I'm thinking 2 things here.....

Metal cabs might be nice, but it seems to me they're still facing the same challenges as speaker cones. Aluminum has miserable damping characteristics in cones, and I suspect you have to very diligent in how you build a cab out of the stuff. 

My other thought is that 2 layers of marine grade plywood sandwiching a constraining layer is about as stiff and as dead as a bowling ball. I watched a guy build some full range transmission lines using a technique like that and he measured the constraining layer sandwich against equal thickness MDF and plywood alone and it wasn't even a contest. 

I have Genelec in aluminium cabinets and they are surprisingly inert - you tap them and you get much less noise than a mdf cabinet. The shape and thickness may play a roll - Genelec’s aren’t square and everything is smooth and rounded. Certainly the aluminium thin heat sink grills on my amp ring when touched.
I have been on the fence about posting on this. These things get nasty at times and I lack the energy to argue with folks.

I have done extensive testing on cabinet materials in the startup of my company. One straightforward approach was too build the same cabinet out of multiple materials. You would be shocked at how much energy goes back into a cabinet and how much strength is really required to damp it.

The frequency with which the cabinet resonates is also extremely important. The lower the frequency, the greater the vibrations that are created and the more it impacts the ability for sound to travel forward from the cabinet and secondarily, the amount of distortion that muddies the sound coming from the drivers.

I used the same drivers, crossover and stuffing in cabinets that were identical other than the material and fine exterior measurements to variances in thickness of the materials.

When you do this, you will find that when you use stiffer materials like Carbon Fiber or even fiberglass stiffened by resin, the sound coming from the speaker will be more natural and fine detail is clear. When the cabinets are less rigid, but still resonate at a high frequency separation of detail will still be good but sound will be damped and dark. The solution is to alter the crossover and make the tweeter slightly more forward.

When the cabinet materials are less stiff and resonate at a lower frequency, the sound will be both dark and muddy. No matter how stiff the drivers are, there is nothing that a manufacturer can do to stop this.

Wood, no matter how heavy, stiff and dense, can’t match it. Some perform better than others, no question. But manufacturers are cost conscious and want to keep prices down. Take a stand mount speaker that is 8"w x 15"h x 10"d. Normal size. The cost of the MDF in that pair of speakers is about $7.50. Baltic Birch plywood will be about $40 and a hardwood would be $100-$400 depending on exactly how rare or exotic it is.

Composites will start above that plus the cost of a mold and much more expensive machining. Same for metal.

There is a reason why Magico’s, Wilson’s, Marten, Vivid, Wilson Benesch, etc... sound so good. The materials they use, whether composite or metal, resonate less and/or do it at a much higher frequency.

Given all that, what material do you think a manufacturer is going to pick when making a cabinet? Especially when everyone is using MDF and it is the industry standard. Unless you are going for high performance, even stepping up to Baltic Birch will add about $100 to your retail price and in hyper competitive markets where there are 80 speakers to choose from, every nickle counts.

MDF is used because it is cheap.  And layered MDF does not significantly outperform solid MDF. It bends easier which is why it is used. Strength comes from layers with oriented strands of grain being laid down in opposite directions. OSB or standard plywood are examples of this. By it’s vary nature, MDF does not have oriented strands. It is stronger than particle board but well short of plywood. Having 7 or 9 layers of thin MDF glued together only makes sense when bending

@verdantaudio  I'm glad you posted this. Thank you!
When you do this, you will find that when you use stiffer materials like Carbon Fiber or even fiberglass stiffened by resin, the sound coming from the speaker will be more natural and fine detail is clear. When the cabinets are less rigid, but still resonate at a high frequency separation of detail will still be good but sound will be damped and dark. The solution is to alter the crossover and make the tweeter slightly more forward.
The alternative explanation of course is that there are no differences and its all imaginary
Post removed 
I’m a little surprised nobody’s mentioned carbon nanotubes. 
@Kenjit...I promise you the differences are not subtle.  

One other note.  What will be completely game changing is when graphene comes available as a skin.  Stronger than Carbon Fiber, graphene layers over a nomex or aluminum honeycomb will be at a completely different level.  

Graphene could be the holy grail for cabinet materials.  
How about concrete?  You can get the stuff they make concrete countertops out of at a store near me for around $15/bag.  Past a point it seems it would make more sense to have portable forms and pour the box onsite.  Or have the box made out of interlocking vertical layers that stacked on top of one another.  How inert and resonance free would a box be if it were brick and you just had a brick layer lay it in your listening room?  It wouldn't cost much.  Maybe have a light box and cover it in a thick layer of concrete.  If performance were really the point of these ridiculous boxes there are bound to be a lot of better ways to going about building an inert box than spending 120 hours machining aluminum.  

The thing is, past a point it can't possibly make sense to have the entire speaker delivered to a house.  You can do a lot of things for 100k, let alone 500k, that you can't for 10k.  It's a very different situation and calls for a different approach.  Or it would, if performance were the primary consideration.

Concrete is interesting but you need to create a mold for a hollow concrete box where you are going to have metal lathe running through it.  Concrete won't hold together without it.   

Not to mention that mounting hardware would be difficult. I doubt that a hammer drill will work near the edges of a round hole like that without fracturing off.  Maybe it would.  I am not sure. 

This seems like it would be harder than you would think.  That being said, a company did launch a speaker that has a stone cabinet and evidently it sounds great.  Acora Acoustics makes their's out of black granite.  

They are about midway down this article.  You can see mine a bit further down under Verdant Audio.
The entire box doesn't need to be made out of concrete.  You could make the baffle from aluminum or some other material that is practical.  My point is that making the entire box of a ludicrously expensive speaker out of a single material is ridiculous.  Making it in a factory and shipping it somewhere is ridiculous.  It doesn't translate if the point is to get the best performance for your $685k.  What is going on here is that the guys who make the decisions for these companies have been around enough rich people to know just how vulnerable their vanity makes them.  
Through NEWAS, an audio club now gone I had the opportunity to hear the Sason Ltd. Granite speakers that Ridge Street Audio brought up with his Poemi cables for a meeting  we had.  The Positive Feedback article was written by the host of the meeting.  Affectionately called Roozer.

It was truly a unique experience especially since the speakers were set up in a 2 story great room with balcony and about 45' x 28' in floor space.  It filled the room.  On talking with Robert and  Steve on the research and work to  get the granite, internal wiring and speaker terminals (no binding post) right was eye opening.  I wish I had the money to buy them back then, although I still love my Soliloquy 6.3's.

It is amazing what you can use for speaker cabinets if you are willing to try.


 Speaking of concrete speakers, there was a company in Sweden named "RAUNA" that made such a thing!  I heard a pair in the early eighties here in Las Vegas at a used stereo store.

@verdantaudio Have you heard the Magico M2? It has 1 piece carbon fiber cabinet. Sounded amazing to me. 

Also the graphene drivers on the newer magicos are awesome.