Joseph Crowe Speaker System No. 2015 DIY. Cabinet construction question

[thrx]

I would like to build these speakers: https://josephcrowe.com/products/speaker-system-no-2015-10-mtm-with-1-4-horn

Is it normal to have zero internal bracing in sealed cabinets of this size, made from 18mm (0.71") Baltic Birch? I've only built a subwoofer so far, so this would be my first speaker build. I have few left over panels of 1" Baltic Birch, and I was thinking of adapting this design to use thicker panels, which would make me feel better about the lack of internal bracing. Thicker panels would mean a slightly wider front baffle so I imagine I may need to adjust the crossover, due to the change in baffle step and edge diffraction effects, unless the difference between 300mm and 314mm is not audibly significant?

Any insight on this specific speaker design would be appreciated. I do understand the characteristics of an MTM layout design and it is good a fit for my application, I was just want to make sure the cabinet construction is as good as it can be, to support two quite energetic 10" woofers.

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[voodooless]

Why not ask Joseph?

Generally it’s a good idea to add some bracing. No need to make the walls thicker. Volume differences would be minimal with some added bracing, so I would not expect any changes to the design.

 

[Salt]

The baffle step will not significantly differ at 314 mm (0.5 % difference), so no need to worry. Additional internal bracing won't harm, too (if not significantly reducing internal volume, what could be compensated by some extra damping OTOH).

 

[thrx]

Why not ask Joseph?

Generally it’s a good idea to add some bracing. No need to make the walls thicker. Volume differences would be minimal with some added bracing, so I would not expect any changes to the design.

I sent him an email, but I've heard at least from a couple of people they never got a response to a question. My main desire to use thicker panels is to be able to roundoff the vertical edges of the baffle, I've modeled the speaker in SolidWorks, it looks much better to me slightly wider with rounded edges.

 

[thrx]

The baffle step will not significantly differ at 314 mm (0.5 % difference), so no need to worry. Additional internal bracing won't harm, too (if not significantly reducing internal volume, what could be compensated by some extra damping OTOH).

I could compensate for the braces easily, as I have the speaker modeled in SolidWorks, and there is no flat pack, so I can alter the dimensions as required. Should I change the height or depth, or width, to compensate for added bracing?

 

[voodooless]

It’s a closed box. The volume really isn’t super critical. You could add some additional damping material to compensate. Speed of sound is slower though the material, so virtually the volume grows.

 

[sigbergaudio]

I could compensate for the braces easily, as I have the speaker modeled in SolidWorks, and there is no flat pack, so I can alter the dimensions as required. Should I change the height or depth, or width, to compensate for added bracing?

Small volume changes from a brace won't affect much, but it's also fine to increase the cabinet in any direction to counter the reduced volume from the extra brace and thicker cabinet panels.

 

[Salt]

I could compensate for the braces easily, as I have the speaker modeled in SolidWorks, and there is no flat pack, so I can alter the dimensions as required. Should I change the height or depth, or width, to compensate for added bracing?

Compensating internal volume loss by increasing depth does not alter the drivers response on the baffle and thus needs no modification of the crossover. So: depth.

 

[sigbergaudio]

Compensating internal volume loss by increasing depth does not alter the drivers response on the baffle and thus needs no modification of the crossover. So: depth.

A slight height difference shouldn't mean the world either. But depth does nothing to the baffle so from that perspective I guess that's best. I'm so used to dealing with active speakers I didn't think of the problem of not being readily able to adjust the crossover as needed.

 

[thrx]

A slight height difference shouldn't mean the world either. But depth does nothing to the baffle so from that perspective I guess that's best. I'm so used to dealing with active speakers I didn't think of the problem of not being readily able to adjust the crossover as needed.

My plan is to build the passive crossovers, however, since I bought a MiniDSP Flex HT with a UMIK-2 mic for my DIY 18" subwoofer integration, I'd like to use it to design active crossovers for the speakers, and use this setup to learn the process. Then I'll build my own multichannel Purifi or Hypex mono amps to power these towers. I see this becoming a long term hobby for me.

 

[sigbergaudio]

My plan is to build the passive crossovers, however, since I bought a MiniDSP Flex HT with a UMIK-2 mic for my DIY 18" subwoofer integration, I'd like to use it to design active crossovers for the speakers, and use this setup to learn the process. Then I'll build my own multichannel Purifi or Hypex mono amps to power these towers. I see this becoming a long term hobby for me.

In that case it could perhaps even be interesting to deliberately change the dimensions and then adjust the crossover to compensate.

 

[thrx]

In that case it could perhaps even be interesting to deliberately change the dimensions and then adjust the crossover to compensate.

I suppose I could use more height on these towers. MTM layout has a limited vertical dispersion and I don't want to tilt the towers more than 2~3 degrees. I'm 6'4" and even when sitting in my lounge chair, my head is a bit higher than normal, while the center of the horn compression driver is only about 31" from the bottom edge of the cabinet. I also don't want noticeably tall isolation feet, so I think a combination of a slightly taller cabinet and a custom designed plinth with a 2 degree rake angle, will do the job.

 

[thrx]

Design modified with 1" thick walls, 1.25" thick baffle with 1" fillet corners, 3/4" thick braces, integrated plinth with custom machined height adjustable legs. Sitting next to my 18" sub. The depicted wooden finish is just what I assigned in SolidWorks, I'm not sure yet what finish I'll attempt. Speakon 4 pole receptacle will be used to connect to external crossover, this is because I'll be fiddling with the crossover quite a bit and also I can easily switch between passive and active (MiniDSP Flex HT).

 

[Jeff M.]

I sent him an email, but I've heard at least from a couple of people they never got a response to a question. My main desire to use thicker panels is to be able to roundoff the vertical edges of the baffle, I've modeled the speaker in SolidWorks, it looks much better to me slightly wider with rounded edges.

I have experienced the same thing each time I email him. So, am guessing it’s the normal. I did resend my E mail and then I got a response from him. He is very upfront and explained how he would do a box design for my speakers I have from one of the first speaker box designs he did years ago pictured on his website. He explained the cost and how long it would take to design this project for me and what kind of file would be sent to me in my E mail. Needless to say I have not reached back out due to the cost and a few other things I didn’t agree with. I hope you get your answers and you are able to complete your speaker project. Good luck . Jeff

 

[crazycloud]

Is it normal to have zero internal bracing in sealed cabinets of this size, made from 18mm (0.71") Baltic Birch?

No. it's terrible design.