Aluminium loudspeaker enclosure

[Kelly Skarra]

Hello all. I am brand new to this forum, so please bear with me. I am also a beginner in the field of loudspeaker design and construction and am looking for help / feedback about ideas I have to design and build my own speakers. I am a Journeyman Machinist, and I understand the qualities and metallurgy regarding aluminium. I would like to incorporate my abilities to construct a loudspeaker enclosure made out of aluminium and educate myself as to how to effectively design a speaker accordingly. I have a general understanding about crossover design and requirements, as well as an appreciation of what has appealed to me over the years with different sounds systems and speaker types. I am looking to design and build a three way loudspeaker utilizing JBL drivers exclusively. Where would a person start when deciding on the size and type of driver for each frequency range and how would I approach the task of building a crossover? Do I design and build an enclosure first, and work from there? I understand this may be a lofty goal and there are a tremendous amount of variables that need to be addressed, however, "you don't know until you ask" has always been one of my philosophies. Any help will be greatly appreciated

 

[shadyJ]

I wouldn't bother designing a three-way as a beginner. I would look at existing plans for three ways and follow those. You can make the cabinet from aluminum but the internal volume must remain the same as any other enclosure material. If you wanted to design a speaker, I would start with a two-way. You will want to pick up some books about it, like the Loudspeaker Design Cookbook.

 

[WaynePflughaupt]

I’d suggest asking your questions on a forum for DIY speaker builders.

Regards,
Wayne A. Pflughaupt

 

[Kelly Skarra]

Thank you ShadyJ

 

[j_garcia]

Issue with aluminum IMO is that it costs more raw for a larger speaker, fabrication cost is higher, and there aren't really any advantages to it. The ones I've seen that were nice were very expensive because it was chosen for it being solid for a smaller cabinet, but then the drivers also had to be specified to suit a small cabinet. All designs have trade-offs.

The enclosure design is based on your goals for the speaker and are modeled off the parameters of the driver to achieve whatever trade-offs you are willing to have in your final design. That means a lot of things need to be decided too - vented or sealed? Deeper bass or more control? 2-way? (2.5) 3 way or more?

Then comes the x-over once you've made those decisions.

 

[BoredSysAdmin]

why only JBL drivers?

 

[lovinthehd]

Aluminum could be cool, you could perhaps offer more reasonably priced ones than Magico does.....good luck!

 

[Mike Ruby]

It's a lot easier to build a good two way speaker than a three way. I also might recommend that you look at going active with the xover if you have a couple of amps to work with. It is an easy way to determine ideal xover points and makes for an easy prototype.

 

[tyhjaarpa]

I believe Genelec uses aluminium for at least some of their speaker enclosures and they look pretty nice. You need to design the speaker first so you know what cabinet volume you will need.

 

[tyhjaarpa]

It's a lot easier to build a good two way speaker than a three way. I also might recommend that you look at going active with the xover if you have a couple of amps to work with. It is an easy way to determine ideal xover points and makes for an easy prototype.

Pretty sure some one can model passive crossover for him easily here when speakers are selected. I don't really see a point for active crossover.

 

[Mike Ruby]

Pretty sure some one can model passive crossover for him easily here when speakers are selected. I don't really see a point for active crossover.

I find going active almost always offers better performance. Decent outboard xover's can be had for less than $300.

 

[BoredSysAdmin]

I find going active almost always offers better performance. Decent outboard xover's can be had for less than $300.

LMFTFY: less than $100
https://www.minidsp.com/products/minidspkits/2-x-in-4-x-out

 

[Mike Ruby]

LMFTFY: less than $100
https://www.minidsp.com/products/minidspkits/2-x-in-4-x-out

Very Cool!

 

[TLS Guy]

I don't think Aluminum is a good material for a speaker. Nothing has been shown to be superior to wood or MDF.

Aluminum has a Young's modulus and rings.

Studies have shown Birch plywood to have the best damping in the mid range frequencies and MDF to be superior in the lowest frequencies.

As to design you start with the speakers. Enclosure design will depend on the type of loading selected and the T/S parameters of the driver. You never start with the cabinet!

I would not advise using entirely JBL drivers. They are not known for high performance midrange drivers for a start.

This new and excellent midrange/HF horn I don't think is available for DIY.

There are very few good midrange drivers. I would advise starting with a two way. In a two way there is little advantage over an active versus passive crossover in a domestic speaker. For three ways there are significant advantages to to active designs. The design must be custom and probably the easiest way to accomplish this is with mini DSP.

Finally it is beyond the scope of a forum like this to teach you how to design a complete speakers if you have no experience or body of dedicated study. It is much more complex than you think.

 

[BoredSysAdmin]

This might give you an idea how complex this process is from The Man himself (there is a very popular and widly used crossover named after him)
http://www.linkwitzlab.com/Fitz/considerations.htm

 

[lsiberian]

I don't see an issue with it if you properly treat the walls. I'd suggest mass loading the walls with rubber.

In terms of 3-way or 2-way. The main issue is cost double the time, 3-ways mean double the amps and double the dsps. A 2-way lets you only buy 1 dsp and 1 4-channel amp. With 2 -ways you need 6 channels of amps and an individual dsp for each speaker.

In terms of driver selection there are several suitable midrange drivers. They may not be ideal, but I personally have had great success with the Dayton Dome Midrange drivers, Morel has one as well. You could also borrow from other folks. Then you select a tweeter and a woofer. These days the internet has a lot of good information with plenty of excellent midrange drivers identified. If money is no object. I'd suggest a RAAL tweeter BG Neo and a SB Acoustics woofer. Of course Money probably is an object. So you'll need to figure out what you can afford.

 

[lsiberian]

This might give you an idea how complex this process is from The Man himself (there is a very popular and widly used crossover named after him)
http://www.linkwitzlab.com/Fitz/considerations.htm

What's interesting is that by designing your own speakers you can specifically voice them to your listening area and your preferences, but it's definitely not a short task. I love my speakers and there is absolutely nothing in the world like them, but it took nearly 5 years with plenty of mistakes to get them the way I wanted them. I'm sure anyone on the forum could design and build a 3-way speaker, but if they had the hour estimate before hand most likely they'd pass.

 

[KenM10759]

Aluminum could be really cool but true it will have completely different resonant frequency than MDF of birch plywood. Cross bracing cam mitigate that, but this is something the major implementers design using finite elemental analysis. Harder to hide screw heads, better if you TIG weld it.

Me, I always wanted to make a pair out of cast iron, Meehanite in particular. Far lower resonant frequencies, almost completely dead in sonic terms. They'd weigh an awful lot though!