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post #1 of 33 Old 03-04-2014, 04:21 PM - Thread Starter
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I'd just like to have someone double check my cf before I get to finalizing this new design.

Enclosure will be made out of 3/4" MDF and driver displacement is .25cf x 2. Length is 65.5. I've calculated a couple different ways and the internal volume differs so I want to make sure I'm using the right method.

Thank you.


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post #2 of 33 Old 03-04-2014, 04:34 PM
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Just do a square box for the bottom potion and then second one down for the top two thirds of your pic. You very well might have already? http://www.hometheatershack.com/forums/enclosure-volume-calculator/ I'm sure someone can do it by the numbers though.

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post #3 of 33 Old 03-04-2014, 04:39 PM
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Quote:
Originally Posted by bass addict View Post

I'd just like to have someone double check my cf before I get to finalizing this new design.

Enclosure will be made out of 3/4" MDF and driver displacement is .25cf x 2. Length is 65.5. I've calculated a couple different ways and the internal volume differs so I want to make sure I'm using the right method.

Thank you.

 

I'm getting 18.6 cubic feet external volume

 

16.05 cubic feet internal

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post #4 of 33 Old 03-04-2014, 04:41 PM - Thread Starter
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Quote:
Originally Posted by steve nn View Post

Just do a square box for the bottom potion and then second one down for the top two thirds of your pic. You very well might have already? http://www.hometheatershack.com/forums/enclosure-volume-calculator/ I'm sure someone can do it by the numbers though.

I did that but the only thing I'm racking my brain on is the extra dimension based on the inside 2 edges not having a side. I added .75 to one side on each but am not sure if that's right lol.

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Originally Posted by doublewing11 View Post

I'm getting 18.6 cubic feet

I sure as hell hope not. biggrin.gif

I get anywhere between 8.05 and 8.3 depending on the aforementioned mystery side. smile.gif

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post #5 of 33 Old 03-04-2014, 04:55 PM
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Quote:
Originally Posted by bass addict View Post


I did that but the only thing I'm racking my brain on is the extra dimension based on the inside 2 edges not having a side. I added .75 to one side on each but am not sure if that's right lol.
I sure as hell hope not. biggrin.gif

I get anywhere between 8.05 and 8.3 depending on the aforementioned mystery side. smile.gif

 

 

I just did a quick calc on iphone................external volume

 

Trapezoid area (b1 +b2)/2*H + rectangle area ( B*H) gives base area.............multiply by 65.5 for length and you have volume in cubic inches......multiply by 1 cf/ 1728 cubic inches and now you have cubic feet.   I don't have my TI-92 on hand.  I do a lot of stumpage with logs so I'm not too far off.

 

 

Edit:  :rolleyes:

 

Freaking iphone........................the trapezoidal base was not divided by two.............now getting 11.2 minus approximately 2.5 cf for 3/4 inch MDF and driver

 

How's 8.7 cf?  I'll go find my calculator.....................phone calculations suck!!!

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post #6 of 33 Old 03-04-2014, 05:22 PM - Thread Starter
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Here's my calc

I added .75" to the height on both boxes as there won't be anything dividing them as one obviously. I'm hoping this is accurate. I get 8.24 total cubes after bracing. That's 4.1 per driver.
That's a little less then my front ones got (4.25 each).



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post #7 of 33 Old 03-04-2014, 05:27 PM
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No, just do .10 on your thickness and you'll come out very close doing it as I said.. It's a option anyway.

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post #8 of 33 Old 03-04-2014, 05:29 PM - Thread Starter
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Originally Posted by steve nn View Post

No, just do .10 on your thickness and you'll come out very close. You can add that to your number if you like.

You lost me there Steve. Why .1? It's asking for thickness in relation to inches, which would be .75. Am I misunderstanding this?

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post #9 of 33 Old 03-04-2014, 05:35 PM
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Just do your calc with your original drawing split in two. Ok I see what your saying. You are doing it as two units.. yeah you're good. What little we can't calc isn't going to matter.

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post #10 of 33 Old 03-04-2014, 05:40 PM - Thread Starter
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Originally Posted by steve nn View Post

Just do your calc with your original drawing split in two. Ok I see what your saying. You are doing it as two units.. yeah you're good. What little we can't calc isn't going to matter.

Cool. Always nice to have a second pair of eyes check it out. smile.gif

The only thing I'm debating now is reducing the size a bit to put it under 4cf as I'll be running a bit more power than the fronts are getting.

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post #11 of 33 Old 03-04-2014, 05:43 PM - Thread Starter
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Originally Posted by aaronlinkous View Post




5.94 cf without the hole or port internally.

That's not quite accurate as I have an extra "leg" on my design.

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post #12 of 33 Old 03-04-2014, 05:44 PM
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Cool. Always nice to have a second pair of eyes check it out. smile.gif

I didn't check it out. I know your all to capable. thumbs up smile.gif

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post #13 of 33 Old 03-04-2014, 05:45 PM - Thread Starter
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Originally Posted by steve nn View Post

I didn't check it out. I know your all to capable. thumbs up smile.gif

LOL. I do have my blonde moments though. cool.gifbiggrin.gif

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post #14 of 33 Old 03-04-2014, 05:45 PM
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I saw in your original post it did, but then in the screen crab of your calculator you didnt have it. So I thought you were updating the design. But thats how I usually figure out volum is to create the shape, then you group them and it'll show you volume.

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post #15 of 33 Old 03-04-2014, 05:48 PM - Thread Starter
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Originally Posted by aaronlinkous View Post

I saw in your original post it did, but then in the screen crab of your calculator you didnt have it. So I thought you were updating the design. But thats how I usually figure out volum is to create the shape, then you group them and it'll show you volume.

The screen grab has it. I built each box separately and combined cf to get a total.

The only thing that's throwing me is the fact when you add .75" to the angled box, it might be inaccurately calculating overall volume due to it's angled design. It's probably not enough to worry about but my ocd...........................

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post #16 of 33 Old 03-04-2014, 05:54 PM
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Originally Posted by bass addict View Post

Here's my calc

I added .75" to the height on both boxes as there won't be anything dividing them as one obviously. I'm hoping this is accurate. I get 8.24 total cubes after bracing. That's 4.1 per driver.
That's a little less then my front ones got (4.25 each).


 

 

Wait a second!  You said height was 23 inches in original post............................................you suckered me!  I'm a human calculator!!!  lol

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post #17 of 33 Old 03-04-2014, 05:57 PM - Thread Starter
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Originally Posted by doublewing11 View Post


Wait a second!  You said height was 23 inches in original post............................................you suckered me!  I'm a human calculator!!!  lol

Height is 23". Seeing as I was building 2 separate boxes in the calc, I was taking into consideration the two sides that won't be there when combined into one box. So hence adding 1.5" to the total height. That should make my internal volume pretty close to accurate.

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post #18 of 33 Old 03-04-2014, 07:25 PM
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I'm getting 9.04 cubic feet before I subtract the .5 cubic feet for the drivers with no internal braces. One problem I was having is with the dimensions you listed. I'm showing that the 20.5 inch face should actually be 19.98 inches long.


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post #19 of 33 Old 03-04-2014, 08:28 PM - Thread Starter
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Originally Posted by dmadesign View Post

I'm getting 9.04 cubic feet before I subtract the .5 cubic feet for the drivers with no internal braces. One problem I was having is with the dimensions you listed. I'm showing that the 20.5 inch face should actually be 19.98 inches long.



I think you're right there. I don't have a cad program so I was doing the calc in my head.

After gluing all my sides together I realize I made another calculation error. When factoring in for my double baffle, I didn't take into consideration based on an angled design, I'm going to lose another 1.5" of surface area. mad.gif The width and height should have been lengthened accordingly.

At this point I'm just going to forge forward. This is my third box design trying to make this hide behind my second row and I'm not building another at this point. I'll have to run with a single 3/4" baffle and hopefully some extra bracing will be sufficient. I was hoping to flush the drivers more so they wouldn't be as obtrusive, but it is what it is. It's also going to be an extremely tight squeeze between the magnet and the back of the cab. I'm hoping this doesn't present any performance issues.

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post #20 of 33 Old 03-04-2014, 09:06 PM
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Originally Posted by dmadesign View Post

I'm getting 9.04 cubic feet before I subtract the .5 cubic feet for the drivers with no internal braces. One problem I was having is with the dimensions you listed. I'm showing that the 20.5 inch face should actually be 19.98 inches long.


 

 

If I add the volume of the driver................I get what you calculated.

 

I used my brain................you guys use calculators.................hmmmmmmm.  lol

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post #21 of 33 Old 03-04-2014, 09:20 PM
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I don't have a cad program so I was doing the calc in my head.

I just use sketchup. I find it's kinda like cheating since it does all the calculations for you. smile.gif
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post #22 of 33 Old 03-04-2014, 09:31 PM - Thread Starter
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Originally Posted by doublewing11 View Post


If I add the volume of the driver................I get what you calculated.

I used my Iphone (Siri is smart as hell) ................you guys use calculators.................hmmmmmmm.  lol

Fixed. biggrin.gif

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post #23 of 33 Old 03-05-2014, 05:27 AM
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It's also going to be an extremely tight squeeze between the magnet and the back of the cab. I'm hoping this doesn't present any performance issues.

I know pole vent is a entirely dif thread but your good being solid.

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post #24 of 33 Old 03-05-2014, 12:05 PM - Thread Starter
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OK guys, I'm in a quandary.

Based on my current predicament; here's what I have to work with. I have two options. Which way would work out the best, if it matters.


1) Single baffle, extra bracing inside. Cubic feet will come in around 8 on the money.

2) I can barely squeeze in a double baffle but my volume will shrink to around 7.5 cf. To fit the db I have to bring the top wall in from 6.5 to 4.5.

I modeled these in Win and there appears to only be about 1 db difference between the 7.5 and 8 cf box, but I want to make sure I'm not giving up anything else.

Thanks

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post #25 of 33 Old 03-05-2014, 12:20 PM
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What about just building it with a single layer baffle and then making a second layer with mitered top and bottom "face" edges and adding it to the outside of the box? This way, it would add the rigidity you're seeking for the baffle panel and it will "recess" the drivers by 3/4". All this without affecting internal volume ad making your brain go cross-eyed!
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post #26 of 33 Old 03-05-2014, 12:23 PM - Thread Starter
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Too late for that lol.

I though about adding a face to the front and top, but the problem I have is depth. 16.75 is really about as deep as I can go without moving the chairs forward, which I'm trying not to do. If I have to I will, but that's the last resort. That also creates a bunch more work as I have to angle cut more lumber, which I hate, lol.

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post #27 of 33 Old 03-05-2014, 12:27 PM
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No problem. My thought is that your lost volume is not going to result in much for real world differences.
I can't wait to see these finished!
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post #28 of 33 Old 03-05-2014, 01:21 PM
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Quote:
Originally Posted by bass addict View Post

OK guys, I'm in a quandary.

Based on my current predicament; here's what I have to work with. I have two options. Which way would work out the best, if it matters.


1) Single baffle, extra bracing inside. Cubic feet will come in around 8 on the money.

2) I can barely squeeze in a double baffle but my volume will shrink to around 7.5 cf. To fit the db I have to bring the top wall in from 6.5 to 4.5.

I modeled these in Win and there appears to only be about 1 db difference between the 7.5 and 8 cf box, but I want to make sure I'm not giving up anything else.

Thanks

With what you run you're fine either or imo just so you brace your baffle good if going single baf as you know.

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post #29 of 33 Old 03-05-2014, 01:38 PM - Thread Starter
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Originally Posted by steve nn View Post

With what you run you're fine either or imo just so you brace your baffle good if going single baf as you know.

I decided to split the difference to appease my ocd lol.

I'm going to add a 3/4" piece to the top but not the front. I'll shift the driver 3/8" up further to center and the db should just squeeze. That puts me at 7.8 which is splitting hairs at this point.

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post #30 of 33 Old 03-05-2014, 01:56 PM
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Originally Posted by bass addict View Post

I decided to split the difference to appease my ocd lol.

I'm going to add a 3/4" piece to the top but not the front. I'll shift the driver 3/8" up further to center and the db should just squeeze. That puts me at 7.8 which is splitting hairs at this point.
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