Box internal space question.
Thread Starter
Teching In
Joined: May 2005
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Box internal space question. As some of you may know I just blew a Rockford Fosgate rfr3112 woofer. I got to thinking it might have been the box who was at fault. It was the first box I've ever built so it might be tuned improperly. I went to the rockford fosgate website and got information on building a ported subbox. Here is where you can see the specs.
http://www.rockfordfosgate.com/ez2/M...0/%20Separates
Now the way I interpret haveing 2.5 cu feet of airspace is this: Box dimensions - wood (which is basically measureing the box from the inside) - the space the woofer takes up (woofer displacement as stated in RF website 224.64 cu in. ) = 2.5 cu ft, right?
Or is it only measuring the inside of the box without subtracting the space the woofer takes up should =2.5 cu ft ? I then put two 4 inch pvc tubes with a length of 12.65 inches per tube to each woofer like it said on the RF website. You can see pictures of the setup here. Also each sub has its own chamber.
http://www.cardomain.com/ride/837010/2
Does all this sound right? Also the tuning for that is supposed to be 40Hz which is what was on the website. Would I get better bass and a better sounding enclosure if I tuned it lower or does each sub have its own specific tuning?
The main question I have is, DID I BUILD THE BOX RIGHT, or would I get better bass and sound building another box which is ported differently (side ported, recantgle port, tuning, etc..).
By the way, I decided to give rockford another try since I don't have enough money to totally change speakers, and bought a replacement sub.
Thanks in advance for all your input.
http://www.rockfordfosgate.com/ez2/M...0/%20Separates
Now the way I interpret haveing 2.5 cu feet of airspace is this: Box dimensions - wood (which is basically measureing the box from the inside) - the space the woofer takes up (woofer displacement as stated in RF website 224.64 cu in. ) = 2.5 cu ft, right?
Or is it only measuring the inside of the box without subtracting the space the woofer takes up should =2.5 cu ft ? I then put two 4 inch pvc tubes with a length of 12.65 inches per tube to each woofer like it said on the RF website. You can see pictures of the setup here. Also each sub has its own chamber.
http://www.cardomain.com/ride/837010/2
Does all this sound right? Also the tuning for that is supposed to be 40Hz which is what was on the website. Would I get better bass and a better sounding enclosure if I tuned it lower or does each sub have its own specific tuning?
The main question I have is, DID I BUILD THE BOX RIGHT, or would I get better bass and sound building another box which is ported differently (side ported, recantgle port, tuning, etc..).
By the way, I decided to give rockford another try since I don't have enough money to totally change speakers, and bought a replacement sub.
Thanks in advance for all your input.
On The Tree
Joined: Aug 2005
Posts: 106
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RF turned to crap after around 2001. I have a pair of 2001 model HX2 DVC 12" subs that have held up really well. The box dimensions are going to be a measure of the internal volume, this does not include the wood or the sub as far as I know. I do not see how the box itself blew your sub, you may have other issues with those amps you are using. What burned up in the speaker and how much power are you putting out for it?
Last edited by zorrander; Sep 20, 2005 at 11:03 AM.
Thread Starter
Teching In
Joined: May 2005
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My woofers voice coils blew. I've heard that making a box wron can heat up your voice coils and make them give out. I'm giving each speaker 1500 rms but I've heard these speakers can take twice as much. Also here is my question again incase I wasnt clear.
Is internal volume space:
A: Measure of internal volume - space woofer takes up = 2.5cu ft
or
B: Measure of internal volume itself = 2.5cu ft
Is internal volume space:
A: Measure of internal volume - space woofer takes up = 2.5cu ft
or
B: Measure of internal volume itself = 2.5cu ft
On The Tree
Joined: Aug 2005
Posts: 106
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I've always been told it's the measure of the box itself... the space the sub takes up does not go toward the internal volume... so it's answer B.
1500 RMS is way too much! If you read your manual for the speakers you will see that the speaker is rated at 1000W RMS Max! It's no wonder you blew the thing up. You're giving it entirely too much power, it is not your box!
1500 RMS is way too much! If you read your manual for the speakers you will see that the speaker is rated at 1000W RMS Max! It's no wonder you blew the thing up. You're giving it entirely too much power, it is not your box!
When you build a sub box ported, you will need to subtract the woofer displacement and the port displacement in the box and add that to the overall air space.
So say you have a sub that requires 2.5 cuft. That is usually internal volume without woofer or port displacement.
Now you will need to subtract the woofer displacement. You say it is 224.64 cuin. You take 224.64 and divide it by 1728 to get the cuft measurement. Which is .13 cuft. Add the .13 to the 2.5 cu ft = 2.63 cuft (internal volume). You will also need to do the same for the ports as well, and add that to the 2.5 cuft.
After all that, you add the port displacement and the woofer dispalcement to the 2.5 cuft.
Something like this....
required box volume + port displacement + woofer displacement = total internal volume for box.
you also wanna make sure your ports are to spec. Don't try and assume a measurement, as it will throw the tuning of the box off. Been there, done that.
So say you have a sub that requires 2.5 cuft. That is usually internal volume without woofer or port displacement.
Now you will need to subtract the woofer displacement. You say it is 224.64 cuin. You take 224.64 and divide it by 1728 to get the cuft measurement. Which is .13 cuft. Add the .13 to the 2.5 cu ft = 2.63 cuft (internal volume). You will also need to do the same for the ports as well, and add that to the 2.5 cuft.
After all that, you add the port displacement and the woofer dispalcement to the 2.5 cuft.
Something like this....
required box volume + port displacement + woofer displacement = total internal volume for box.
you also wanna make sure your ports are to spec. Don't try and assume a measurement, as it will throw the tuning of the box off. Been there, done that.
