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Speaker enclosure dimensions, how to find it?  

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D2U
 D2U
(@d2u)
Active Member Registered
Joined: 4 months ago
Posts: 6
23/10/2020 4:49 am  

Hi :),

 

I've stumbled on a problem when I was designing a speaker. I use the winisd software for modelling the speaker. Once one has finished modelling, the program gives a box-volume(v) and port size. In my case the box volume was 50 liters and the port had a diameter of 7,6 cm and a length of 16.6 cm.

In my design the port will be inside the box. Correct me if I'm wrong, but that means that the internal volume of the box should be the volume given by winisd + the volume of said port that will be inside of the box, right? If so, should I also take the driver volume into account? If so, is there any easy trick to find out what volume your driver is?

In my case I'm planning on using 18mm mdf as base material. So the internal volume should be equal to 50L + (Pi*8cm^2(ie. outer diameter of port)* (16.6cm-1.8cm) )/1000(in order to go to liters) + driver volume

50L + 2.98L + driver volume = 52.98L + driver volume.

Lastly, once I had my volume I was planning on getting the box dimensions by taking the third root of the volume converted to cm. Is this a proper way of getting the box dimensions? I'm kinda newbie to this so if there are certain design rules for converting your enclosure volume to dimensions plz share :).

Thanks a lot for the help.

 


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TVOR-Ceasar
(@tvor-ceasar)
Honorable Member Moderator
Joined: 2 years ago
Posts: 523
23/10/2020 9:33 am  

"50L" is the optimum internal volume that would make the driver(s) perform correctly. And yes, you Should take into account for things like driver displacement (considering mounting type - inside or outside baffle and adjust accordingly), port volume (outside dimensions), and other "large-ish" objects, such as bracing and X-over components. Small stuff, like wires etc. can effectively be ignored since box size is actually somewhat forgiving. My personal number is +-10%.

Once you have that done take the total and get the Cube Root, then use the correct multiplier to get to your unit of choice. That will give you your internal base "Width" (of the face plate), which you can use to get the rest.

Golden ratio:

Width*0.618=Depth
Width*1.618=Height
(this classically is the most pleasing to the eye)

Acoustic ratio:

Width*0.7937=Depth
Width*1.2599=Height
(this is designed to reduce standing waves inside the box)

Of course, these are just guidelines. You can play with the numbers  to get your own unique box, as long as you end up with the correct volume.

-Charlie


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D2U
 D2U
(@d2u)
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Joined: 4 months ago
Posts: 6
23/10/2020 10:11 am  

@tvor-ceasar

Thanks a lot for your feedback! I'm going to build a few test-boxes very soon. I plan on 3d printing the final enclosure, but I first wanna be absolutely sure I have the right dimensions. Thus, I'm gonna make a few prototypes first. About the standing waves, is it possible to correct them by using a simple dsp? Or would the effect be negligible compared to a box design with your acoustic ratio? Also, would it help if the corners inside the box would be round instead of hard 90 degree angles?

Lastly, does the placement of the driver on the front baffle have any influence on the occurrence of standing waves? Should it be centered or have a small offset to the bottom or is the effect negligible?

Again, thanks a lot for the feedback 😀

 


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kanaaudio
(@kanaaudio)
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Joined: 5 months ago
Posts: 71
23/10/2020 5:17 pm  

@tvor-ceasar

very useful info, the ratios. Am in the process of designing a new box myself. Thanks for that 🙂 


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