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2 Rockford Fosgate P3D4-15 box build

post #1 of 45
Thread Starter 
I am getting a great deal on 2 Rockford Fosgate P3D4-15 subwoofers, and am going to need to make a box for them. http://www.rockfordfosgate.com/products/details/p3d4-15
that is a link to the product page so you can see the specifications.
I am not sure what amp i am going to use yet, but being as this is just a budget build, I will probably go with a Behringer epx3000 or 4000. unless I can get a good Crown or something off Craig's list.
I have never built a box for a house and am going to need help designing it. I do have a good amount of experience with wood work, so the construction of the box shouldn't be a problem, but coming up with the dimensions is.
I want it to play 15hz-80/100hz.
I am currently reading the different threads, and have downloaded and am messing with winISD.
I think I would prefer a ported box, but am not sure, especially if it is going to have to be giant. I can do big, but I don't want a giant couch sized box.
So if some of you with lots of experience could help me out, I would greatly appreciate it. thanks.
post #2 of 45
Thread Starter 
I would consider building 2 seperate boxes as well. Depending on how far it is safe to run speaker wire between an amp and a sub.
post #3 of 45
That driver really wants a sealed box, and extension is good in a sealed box. You can do ported, but if you want to tune way below 20 hz you're going to need a miniDSP in order to set a high pass filter that low. A 4 ft3 sealed box each, with a EP4000 for power would be a nice setup, you'll want to wire the subs for 8 ohms, as they cant really handle much power.

If you really want ported, 10 ft3 each with a pair of 4" x 24" ports will tune you to 16hz, you would use the same amp and 8 ohm wiring as above, but you have to add a miniDSP to set a 15hz high pass filter.

Here's each of the above with 450 watts



You can calculate what gauge wire you need here

http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf
post #4 of 45

Here is a single driver in a sealed and ported enclosure. The driver wants a huge enclosure which is why you see the hump at tuning on the ported and a high QTC on the sealed enclosure. Both at 500w and the ported enclosure has a 20hz highpass.

 

post #5 of 45
Thread Starter 

is this ok? I put on a 100hz lowpass filter. my biggest issue is with the ported box. I don't know what id have to do to get the velocity right so I don't get port noise.
Why have you guys been putting on 20hz high pass filters? that means it wont play below 20hz. also I don't even think a sub amp will let you set a high pass filter. only a low pass.

I figured out how to change the graphs range.
Edited by iBurn - 7/27/13 at 5:08pm
post #6 of 45
A plate amp will have a built in HPF. Most of the Dayton amps are at 18hz, a couple at 20hz, and I think the Yung amps are at 30hz. I was suggesting a pro amp with a separate EQ for more control, but if you want to use a plate amp, tuning to 18hz would work fine.

Ideally you want to keep port velocity below 17 m/s, but realistically you can have it go higher then that, depending on the output level of the sub.
post #7 of 45
Quote:
Why have you guys been putting on 20hz high pass filters? that means it wont play below 20hz.

 

Go to the cone excursion window in Winisd, you'll see why. Below the tuning frequency the cone excursion will sky rocket which will bottom out the driver possibly damaging it. Unless you know for sure the audio you're listening to has no content below the subs tuning point then its ok to run without a highpass. Of course you would have to scan each and every movie/song for low freq...

 

 

Quote:
I don't know what id have to do to get the velocity right so I don't get port noise.

 

One option to get rid of chuffing entirely is to use passive radiators. They work just like a port but with no chuffing and it saves you internal space. The only problem is that they cost a lot more than a piece of pvc or scrap wood.

post #8 of 45
Thread Starter 
how low can I go with a sealed box? I feel like it would be cheaper and easier to go that route. I plugged a cheap Dayton 12 passive radiator into winISD and it took 5 of them to keep cone excursion in a safe range, so that's not going to work. in a 8' ported box tuned to 18hz, with 2 ports, everything seems to be ok tho, so that could be an option. im looking to make the box aprox. 12in deep, 26in wide, and 48in tall front facing sub, or 16in deep, 24in wide, and 48in tall, with a up or down facing sub. not sure about port placement. the subs will probably be placed in the rear corners of the room.
post #9 of 45
How big is the room? In 4 ft3 sealed you have an F3 of 30hz and an F10 of 20hz. That is actually really good, and with some room gain you could be flat to well below 20hz.
post #10 of 45
Thread Starter 
im setting it up in an extra bedroom, so I will be able to close the door, and the room is about 13'x12' with a 10' ceiling. its a square room. so Its not living room big, but its a decent sized room. also it has wood floors. I want to be able to be able to feel the bass.
Edited by iBurn - 7/28/13 at 1:29am
post #11 of 45
Quote:
Originally Posted by iBurn View Post

im setting it up in an extra bedroom, so I will be able to close the door, and the room is about 13'x12' with a 10' ceiling. its a square room. so Its not living room big, but its a decent sized room. also it has wood floors. I want to be able to be able to feel the bass.

The corner to corner wavelength of your room equals 63hz, so if you start to heavily pick up room gain from the 1/2 wavelength point, 31.5hz, a basic sealed box will actually be a perfect choice.

You should be able to get flat down into the single digit range as long as you dont use a plate amp.
post #12 of 45
Thread Starter 
Quote:
Originally Posted by Jay1 View Post

The corner to corner wavelength of your room equals 63hz, so if you start to heavily pick up room gain from the 1/2 wavelength point, 31.5hz, a basic sealed box will actually be a perfect choice.

You should be able to get flat down into the single digit range as long as you dont use a plate amp.

thanks. im not planning on using a plate amp. im either going to get a crown xls, or a behringer epx amp depending on which I can get cheaper. its between those, because I can get 1 rca splitter cheaper than a rca splitter and 2 xlr converters.
I was looking at the subs today tho, and it turns out 1 is a P3D2-15 and the other is a P3D4-15. sinse they will be in separate boxes, I will be hooking them up to the amp in separate channels. so do you think it will be ok? I know one sub will end up getting more power than the other, but other than that it should still work right? that's probably why he was selling them so cheap.
post #13 of 45
Yes you can still use them, but you will need to adjust their levels. The sub wired at 4 ohms should be set about 3 db lower then the sub at 8 ohms.
post #14 of 45
Thread Starter 
Quote:
Originally Posted by Jay1 View Post

Yes you can still use them, but you will need to adjust their levels. The sub wired at 4 ohms should be set about 3 db lower then the sub at 8 ohms.

alright cool, that's good. And most amps should be capable of adjusting each channel separately right?

here are the subs next to a blown 12 I took out of an old tower I have and a quarter to compare size.




on a side note, do you know of a good 12" sub to replace that one? it needs to be 8ohms and less than 100watts. preferably around 50watts, as the tower is being powered by my receiver and it only puts out 70w per channel. I am currently considering a Dayton dc300-8 12"

Thanks for all the help.
post #15 of 45
Thread Starter 
the maximum recommended enclosure volume from the manufacture for a sealed box is 3'. why is that? will there be a problem with cone excursion or something?
post #16 of 45
Quote:
Originally Posted by iBurn View Post

the maximum recommended enclosure volume from the manufacture for a sealed box is 3'. why is that? will there be a problem with cone excursion or something?

The main reason is because it's a car sub wink.gif

3 ft3 does control cone excursion very well, but the Q is getting pretty high, you're giving up some low end efficiency. If you plan on pushing these subs really hard, then 3 ft3 might be better.

As far as that other 12" driver, really hard to say without seeing some measurements...
post #17 of 45
Thread Starter 
I need to get down to at least 20z. I prefer to feel my movies. I feel like it makes it a significantly more emursive experience. If you think 4ft would be better, without risking the sub, then I'd probably do that.
As for the 12, it's out of an old kenwood JL-775 floor tower. I've hardly got anything into the towers, so the replacement needs to be pretty cheap. I'd get a used one off Craigslist, but it's suprisingly difficult to find a low power 8ohm 12" subwoofer.
post #18 of 45
I like how the 4 ft3 box looks better, but it won't be a huge difference if you go smaller.
post #19 of 45
Thread Starter 
ok. so ill probably make it 4 feet inside, then add bracing and whatever it is after bracing is what ill have. how much bracing do you think will actually be necessary? also I was wondering if the dimensions would affect how it sounds. I want to make it a tall box so I can set my rear speakers on top of the boxes. im thinking of making it 44" tall, 22" wide, and 11" deep. with the sub mounted on the front.
post #20 of 45
Thread Starter 
I got a behringer epx3000 off ebay for $250 today. so hopefully that will be good.
Edited by iBurn - 7/31/13 at 4:31am
post #21 of 45
Epx3000 should be good. For bracing just pick up some square dowels and make 4-6 sets of # shaped braces connecting the front/back/sides evenly spaced across the 44" dimensions. Stuff the top and bottom of the box heavily with poly pillows to reduce standing waves from such a tall cabinet.

Make sure you put a stable base on the box, it might wobble being that tall.
post #22 of 45
Thread Starter 
I can just put in corner shelfs to set my speakers on if the boxes being that tall could cause problems or not sound as good.
post #23 of 45
Thread Starter 
I ended up making 3.5ft boxes, and there is way to much excursion. what should I do? should I just put a port in it? what size port would I get if that would work?
post #24 of 45
What do you mean by way to much excursion? Is it bottoming, or distorting badly? In 3.5 ft3 with 500 watts the sub should be topping out at a little over 15mm excursion, the sub is rated for 14mm xmax, 1-2mm over xmax is nothing.

Are both subs having issues?
post #25 of 45
Thread Starter 
maby tune it to like 20-28hz. I assume it would still play down to at least 20hz if I did that right?
post #26 of 45
Thread Starter 
i have only hooked one up so far, but it is running at 4ohms, and when i turn it up, the sub is going out way to far. like it looks like the voice coil is coming all the way out, to far. not good.
post #27 of 45
Thread Starter 
this amp is rated at i think 900 watts per channel at 4 ohms. so its getting a lot of power.
post #28 of 45
No you cant just port an undersized sealed box, there will be a massive hump around 40 hz...
post #29 of 45
Thread Starter 
i think it is bottoming out. please help, i need to get this fixed soon.
post #30 of 45
That amp isnt really putting out 900 watts. Even if you somehow pushed 900 watts you would have 20 mm excursion in the low 20hz and below range.

Im still not sure exactly what you are doing with the subs,is it making a clacking type sound?
Edited by Jay1 - 8/5/13 at 5:50pm
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