Custom box advice

[chris41586]

I'm wanting to build a custom box for my subwoofers and I'm a little confused about some things. First thing is: why does vented SQ call for more volume than vented SPL? I thought SPL called for more volume than SQ, but this is what the Phoenix Gold recommendations say.

I'm also having a little trouble coming up with the design. I went on to re box calculator and played with some numbers. I got to the correct volume, port width, height, and length, yet at the end, the tuning was a little off. I'm not sure how this is, given the correct dimensions. I'm open to any helpful input, and I can also post the equipment I'm working with if needed. Thanks!

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[shredder2]

I'm wanting to build a custom box for my subwoofers and I'm a little confused about some things. Thanks!

http://www.caraudio.com/forums/enclosure-design-construction-help/560833-about-make-thread-about-box-design-read-first.html

 

[kr15 5,000+ posts]

There are generally 3 reasons for small spl boxes;

1- to make it as peaky as possible

2- reduce mechanical strain on driver so that more power can be applied

3- fighting rise, especially with neo drivers that lend to crazy amounts of rise

An sq box needs to accomplish none of these things

 

[THATpurpleKUSH 5,000+ posts]

The re box calc is not correct because it doesnt account for sub and bracing displacement. It will get you close but tuning and volume will be off by about .2cf and 3-4hz. It's ok if you are an experienced designer and know how to calculate on your own, but for those who are inexperienced its not a good tool to use.

 

[chris41586]

Yeah that's about how much it was off. I could just calculate volume by hand, on paper, but I would have no idea about the tuning. Do you recommend another calculator that would be good for a beginner? And is it really that much of a difference if I'm off by a couple of Hz?

And to the reply before the last: is it correct to say that vented SPL is going to be louder than vented sq, even though the sq calls for more volume? The speakers in running are two Phoenix Gold sx112d4. You could look at the recommendations to see what I'm referring to if you'd like. I also can't find anything online, that other people have made for these particular speakers, for reference.

 

[kr15 5,000+ posts]

Vented spl will be louder over a much more narrow bandwidth. Full on burp boxes can often only play about a 3-5hz bandwidth, sloping off quickly. It is driver dependant however. I was using a pair of custom 12s for a while, that had a loose gap, with modest motor force and slightly high Q as they were built for a 4th order. They ended up liking a normal size box for spl, just tuned close to cabin resonance. Those 12s did 153.4 legal, clamping 4k.

But an SQ enclosure is quite the opposite. You want to get a nice flat, usable bandwidth. Whatever it ends up being for your personal desires. Perhaps 25-65hz for example. A narrow bandwidth box is the opposite of what you want

 

[THATpurpleKUSH 5,000+ posts]

Yeah that's about how much it was off. I could just calculate volume by hand, on paper, but I would have no idea about the tuning. Do you recommend another calculator that would be good for a beginner? And is it really that much of a difference if I'm off by a couple of Hz?

And to the reply before the last: is it correct to say that vented SPL is going to be louder than vented sq, even though the sq calls for more volume? The speakers in running are two Phoenix Gold sx112d4. You could look at the recommendations to see what I'm referring to if you'd like. I also can't find anything online, that other people have made for these particular speakers, for reference.

I like to use the enclosure calculators on the12v.

I use round or slot port calc first to get an idea of how much port length i need then i play around with the rectangular volume calc to get my dimensions then i go back and forth between the 2 to fine tune things where i want them. Then i go into winisd and bass box pro 6 to double check my calculations, when I'm done i sketch it out by hand to give myself a visual representation and I lay out my cut sheet for the lumber store.

 

[shredder2]

I use Winisd and Torres then once drawn up in Sketchup I use dimensioning to get an exact volume and end-corrected port length. Then plug those #'s into Winisd to get actual #'s on the enclosure. Lotta calculator use I know but I try to be as exact as possible and soon I'll be adding BB6pro to the tools I use (if I can learn it). For some reason I'm having trouble with learning that particular program... lol... for me it does not compute so to speak. I guess I'm just a Gramps.

As far as apps go I like the "Ultimate car audio app" by Xplicitaudio... seems to be a good one and it's never very far off.

But for cut sheets and dimensioned port pieces then I rely on Sketchup, once dimensioned it's easy to see what you need to cut. I usually just explode the drawing and annotate if it's a X1 or X2 piece and what materials to use... like this...

 

[chris41586]

Thanks guys. I'll try those different programs when I get home, and hopefully have better luck. One thing I just thought of though: do I need to add volume for bracing? And also what about being off by a couple of hz? Does it matter that much?

 

[shredder2]

Bracing... lets see... 2.88 x 2.88 x height is a set of 2 4" 45's, 2.12 x 2.12 x height is a set of 2 3" 45's... 1.76 x length is a 1.5" round dowel displacement... etc.

Just add em in and once again it's all about the trusty ol' calculator for me... I've learned to back-check EVERYTHING if I want complete accuracy and piece of mind.

Now, those numbers are not 100% accurate but super close to figure bracing and it'll turn out fine if used.

I'm just used to doing it this way... seems like a lot but it's accurate as h*ll in my experience.

 

[THATpurpleKUSH 5,000+ posts]

Thanks guys. I'll try those different programs when I get home, and hopefully have better luck. One thing I just thought of though: do I need to add volume for bracing? And also what about being off by a couple of hz? Does it matter that much?

I can tell a difference when there is a 2hz difference im tuning. Its most apparent on notes below 35hz, not so much above 35hz unless its a high peaky tune. Some people will say you wont hear a difference until theres at least a 3hz difference. I try to get it within +/- .5hz

 

[THATpurpleKUSH 5,000+ posts]

I use Winisd and Torres then once drawn up in Sketchup I use dimensioning to get an exact volume and end-corrected port length. Then plug those #'s into Winisd to get actual #'s on the enclosure. Lotta calculator use I know but I try to be as exact as possible and soon I'll be adding BB6pro to the tools I use (if I can learn it). For some reason I'm having trouble with learning that particular program... lol... for me it does not compute so to speak. I guess I'm just a Gramps.As far as apps go I like the "Ultimate car audio app" by Xplicitaudio... seems to be a good one and it's never very far off.

But for cut sheets and dimensioned port pieces then I rely on Sketchup, once dimensioned it's easy to see what you need to cut. I usually just explode the drawing and annotate if it's a X1 or X2 piece and what materials to use... like this...

Email me or pm me if you need help with bbp6, I'm getting pretty good with it.

 

[shredder2]

[quote name='THATpurpleKUSH']Email me or pm me if you need help with bbp6, I'm getting pretty good with it.[/QUOTE]

Sounds great... thanks!.. do you know of a video for dummies?.. I think I'm overthinking the program. I need something I can watch repeatedly, @Jeffdachef can attest to that... he put up with me while I learned to use Winisd, took a while to even enter parameters, I kept on entering exact values for everything... lol... "Tab, Tab" is your friend in that program.

 

[THATpurpleKUSH 5,000+ posts]

[quote name='shredder2']Sounds great... thanks!.. do you know of a video for dummies?.. I think I'm overthinking the program. I need something I can watch repeatedly, @Jeffdachef can attest to that... he put up with me while I learned to use Winisd, took a while to even enter parameters, I kept on entering exact values for everything... lol... "Tab, Tab" is your friend in that program.[/QUOTE]

I'm not sure of any videos, there is an owners "manual" that walks you through a couple different designs. Its more like a book but its very helpful. So that combined with my knowledge of winisd makes it seem really easy to use. I had no problem picking it up.

 

[chris41586]

So another thing I didn't consider... The specs calls for 1.75cf for each speaker and then gives the port dimensions as 2" by 12" by 22". The box is going to be for two subs, so I double the volume to 3.5cf, but how do I come up with the port dimensions? I thought I would just have the ports meet in the middle with a divider, but the speakers are duel 4ohm, and they get wired down together before going to the amp, with a final of 1ohm. Do I not put a divider and make a bigger port? Put a small hole in the divider?