Steel Speaker Enclosures

[EDS]

I've been reading the forum for a couple months and have really enjoyed all the projects.

I work in a manufacturing company specializing in laser cutting and CNC bending. I have the resources of 3D modeling and a million dollars of equipment to produce steel parts.

I assume that steel would make a horrible enclosure material because I've never seen it done, but I still had to ask. Is there any way steel could be used?

Thanks for your input.

If I could ever help anyone out by doing some 3D modelling or drawings for you, feel free to ask. I would love to help out.

[ThomasW]

It's not an inherently inferior material, it's just not cost effective given the weight and cost of machining.

I'm sure one could fabricate a nice cab from 1/4" plate. Moving it around might be problematic....

[EDS]

What would be involved in designing and producing a new set of speakers made of steel enclosures.

I assume

1. spec. the drivers for intended use.
2. design the enclosure for these drivers.
3. produce an enclosure and install drivers.
4. design, build, test and optimize XO.

Would anyone participate in this by designing and building the prototype XO? I would supply a couple complete enclosures for them to keep.

Would any special considerations need to be made when using steel? Dampening material for example.

I am thinking of making MTM speakers that would be stand mounted, used for primarily HT. This size speaker would be very easy for us to fit into our production schedule at little cost for material, laser cutting, and CNC bending. Welding would be very simple compared to our normal daily operations.

[TacoD]

http://www.tnt-audio.com/casse/adorn_concerto3_e.html

I think extra care is needed to treat the resonances of the cabinet. Think of bitumes. As design you can take the Modula loudspeaker designed by Jon (see sticky thread of this subforum). A couple of people have already made a pair.

[cjd]

My only other vague concern would be whether that much steel would tweak the response at all due to magnet interaction.

C

[EDS]

due to magnet interaction

What about using sheilded speakers?

Think of bitumes.

What is bitumes"


I've attached a prelimenary design photo.

[noah katz]

You could have a very stiff and light enclosure if you had inner and outer shells of thin steel and filled the space between them with expanding polyurethane foam.

Not sure how that uses your capabilities, a sheet metal shop could do it.

Seems like you have more technology than needed for the job.

[TEK]

How does steel compare to wood when it comes to stiffness vs. weight vs. thickness?
I would assume that alluminium would be a better material if that was available.

However, using one of those material would problably enable you to create speakers with more inner volume for the same outer volume as a wood speaker.
If you shape the cabinet correctly you should get it very stiff. I would guess that it will move the resonance frequence up quite a bit compared to a wood speaker, so that it will be very important to damp the higher frequences.

Just my 10p

TEK

[jdybnis]

Here is a white paper with some info on damping steel. Doesn't seem too difficult.

http://www.earsc.com/HOME/engineering/TechnicalWhitePapers/DesigningForQuietVibration-freeOperation/index.asp?SID=145

[joecarrow]

I think that steel would be a really rough material to make cabinets out of, mostly due to the weight. You could probably make an insanely stiff framework out of the steel, like a cage with bars running inside, and use something like plywood for the actual walls. With only a few inches of free space between super-rigid braces, I don't think there would be much deflection for even the baddest subwoofers.

What seems more interesting is the possibility of turning your own custom horns, or making different systems for mounting woofers. For example, a bracket to hold a woofer by the magnet, or a floating ring filled with a viscoelastic damping foam to decouple the woofer from the cabinet.

In any of those cases, stainless is probably the least magnetic form of steel you could use. Aluminum should be a heck of a lot easier to work (especially turning your own horns!)

Whatever you do, I know we'd all love to see how it turns out

[EDS]

I've done a little further modelling and came up with a drawing.

Overall size and weight is well within reason. Internal volume looks promising, but I still don't know what drivers I would be using yet.

I've been thinking about the finishing options. Automotive paint with clear coat would be amazing and very easy to do for any body shop.

[ThomasW]

One potential problem is that the drivers are usually recessed flush with the front baffle. If you cover the entire front baffle with a layer of high wool content felt gasket material that solves the flush mounting problem.

You don't need that many small holes in the brace. A few larger ones would be fine.

I'd be tempeted to use diamond plate for the exterior surfaces excluding the front baffle.

How about having the enclosure plated with black chrome?

[cjd]

Oh man...

The speakers I'm dreaming up at the moment would be SO ideal in metal. Not sure the could be done CNC or in a machine shop sensibly, probably would need to be hand massaged.

Adding a slight curve to the sides should dramatically increase the stiffness.

C

[EDS]

One potential problem is that the drivers are usually recessed flush with the front baffle

Why are they flush mounted? What does this effect?

All sorts of materials are possible, but we cut a thousand or two pounds of carbon steel every day. Slipping in these relatively small parts will be easy and free for me. These can be painted with automotive paint to give a spectacular finish.

[TacoD]

Why are they flush mounted? What does this effect?

All sorts of materials are possible, but we cut a thousand or two pounds of carbon steel every day. Slipping in these relatively small parts will be easy and free for me. These can be painted with automotive paint to give a spectacular finish.

Drivers are flush mounted to reduce diffraction effects on the edges. This alters the frequency response. You can put some foam, velt on the baffle to fill the difference in height.

Bitumes, I am not sure what's the correct translation for it, I was refering to automotive dampening plates. Those are used in car doors and other places in the car to reduces resonances. A bit expensive, but available from your local car parts retailer.

[taz13]

Pro sound and industrial sound have been using metal for speaker enclosures for years and it works well. The probable reason it is not used more is the expensive of the machinery needed to mass produce.

[ThomasW]

If you have the capabilities to fab a curved or rounded back that would be pretty cool....

[EDS]

to reduce diffraction effects on the edges

Could you explain this a little further or point me to something that will. I follow what your saying, but would like a little more explanation.

Is this a "big" deal. I could definately recess the driver if needed.

[Tommythecat]

The transition between the surround, frame, and then baffle face plays a critical role in diffraction effects which can be found in the on-axis and off-axis freq. responses. Because we flush-mount a driver, the transition is eased going from the frame of the driver to the baffle board.

It's not a world of a difference, but it really helps to keep the midrange as smooth as possible, which helps the general soundstage, etc.

[Landroval]

Is this a "big" deal. I could definately recess the driver if needed.

It is, at least for tweeters and midranges. And I see no reason not to do it for all the drivers (exept those that are made for surface mount).

This might help:

http://www.zaphaudio.com/mtg-surface.html

[ThomasW]

It's doesn't need to be done if you use acoustic foam or felt gasket material on the front.

Even with flush mounted drivers, we use the felt because it improves the performance of the tweeter.

[EDS]

I wouldn't want to use felt on the front because of the look. I want to keep the smooth, flat painted finish that steel could give. I am going to using small magnets in the speaker grills to hold them in place. I can flush mount the drivers by welding a flange in the inside of the baffle.

Where can I get more dimensions of these speakers: Dayton RS180S and RS28AS=4

[ThomasW]

I wouldn't want to use felt on the front because of the look.

Too bad because it certainly improves the performance of the speaker.

Where can I get more dimensions of these speakers: Dayton RS180S and RS28AS

The Parts Express has the dimensions for each driver on their website. But it's best to have the units in hand just in case there's any unit to unit variation.

[cjd]

Another note: it's important that any driver near a tweeter be flush-mounted, because the tweeter will still "see" the edge. Felt still helps with this significantly, but without felt...

And, if you're putting a grill on the speakers, put the felt behind this inside the grill frame with driver cutouts where they need to go.

C