box parameters

I am going with a pretty modest system and I just want it to sound as good as possible. I am new to box building and I am trying my best to find out on my own the best box to build, but I want opinions from more experience individuals. I am going with the Polk DXI 10" subwoofers and I am going with an amp that will push them about 150 watts rms each. I listen to mainly rock, but listen to about every other type of music as well. I am just really going for sound quality. Here are the numbers I have for a sealed box: Qtc: .6725 Qts: .55 Qes: .59 Fs: 35 hz Vas: .99ft^3 Pmax: 150 watts Xmax: .622 in Vb: 3455.57in^3 Fb: 42.7955 hz F3: 45.1106 hz Would an enclosure with these parameters be okay for what I am wanting? My only concern is I drive a smaller car and two subs would be around 4 cubic feet for the enclosure. Any help would be great! Let me know if I am completely off on something, because this is my first box I am trying to build to using t/s parameters.

Maybe a box the that is roughly 30" wide, 14" tall, and about 16" deep...would have to be a littler larger than that because I didn't account for bracing and thickness of mdf

I looked that sub up in the manufacturer's site and put the available parameters through WinISD. By what you wrote, you apparently have two SVC 4 Ohm woofers.  A few thoughts:

Most of the info you posted looks accurate, although Pmax wouldn't be 150 watts but that's not really important.  The use of a huge 4 cu ft box to house these two subs, with what you are getting in return, is where the concern lies.

This is not a very good SQ sub.  The fact that you have to use a minimum of 3 cu ft (what I modeled) for the two subs to achieve a  45 to 48 Hz F3 doesn't seem to me to be a desirable trade-off.  I see this sub as a better potential in a vented box, where you can use basically the same cubic footage and short vent length and get a lot more sub bass out of this Polk.   Your amp's limitation of 300 watts is a negative factor when putting these subs in a sealed box.

I suggest that this sub would be happier in a vented box that has 2.75 cu ft of net airspace and a slotted vent of 16 sq in (such as 2 X 8) and is 9.6 in long, tuning the enclosure to 35 Hz.  It looks like you would get the best out of this sub in this way.  Your available amplifier power would be better put to use.  If you go with the sealed alignment, I'd keep it at 3 cu ft and increase the available power, if possible.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Okay cool thanks! Yea, they are not my first choice for subs, but I get them for an insane price (or I would be getting them at all.). I was just using free software I could find on the internet, so I didn't know how reliable it would be. I do appreciate the info though! Trust me I know these subs suck and the amp as well, but it is just to get me by as I am transitioning from college into my career. I plan on getting a good setup when I get everything sorted out. The goal here is to just make this semi pleasurable while I have them! Thanks again!

The Pmax is the max power of the sub then? I wasn't completely sure, so I just put in what I was going to be supplying the sub with. I can see how this would change accurate results when the sub is design to handle more. If that's still wrong feel free to correct me! I am trying to learn as much I can.

Pmax isn't a parameter that you should pay any attention to when selecting a sub, speaker, or amplifier because it is supposed to be the power that a component can handle or produce for a very short amount of time. From what I've read on this site peak, Pmax, max power are more marketing than measurements and I don't think there is a standard procedure for determining them. Instead you should look at the components rms power rating or the continuous power rating.       A perfect first hand learning experience I had was when I bought my first sub and amp. Infinity 1220 12" sub 1200watts max but really 300watts rms and a legacy rebel 2000watts MAX POWER 2 channel amp really only 150watts rms X 2 channels which is why it made pretty good bass. But when I got my Eclipse XA1200 500watts rms and hooked it up it was like I bought a new sub too because the quality of the amp was so much better the sub played louder and tighter. This is getting long ...sorry. Concerning your question about how it effects the design of the box. A sealed box causes resistance on the sub as the sub moves because the air acts like a spring, damping the movement of the sub. This is why stevdart recommended more power for the sealed because it takes more power to over come this resistance. Also the power effects the excursion of the woofer but that is also dependent on the box design and I'm sure stevdart checked that in WinISD so I wont go there. I hope that wasn't too much and I bet stevdart will correct me if I have mis spoken.

Good to hear from you again zoomzoom, and a good post.  It's true that these subs would appreciate about double that available power if enclosed in a sealed box.

To the OP: The benefit here is that you could build a large sealed enclosure, 3 to 4 cu ft., and still have enough internal space to reconfigure to a vented alignment.  This sub works with a relatively short vent length as I described in the above post.  So that, if using these as sealed (SQ?) doesn't quite work well enough for you, you can rebuild the same box into a vented enclosure while maintaining the same footprint.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Trust me I know what max power is. I was trust making sure that's what it was in t/s parameters. That is why I put the 150 into the program because that is what I was going to supply it with. I also know the differences between boxes. I was thinking sealed because I wanted tighter bass, from the air resistance in the box. That was until I saw how big it was going to have to be. I know that vented enclosures have a vent tuned to a certain frequency and they play higher around said frequency, but have a higher roll off of frequencies that are not as close to the tunes frequency. The only thing I really needed was to confirm that I was getting accurate t/s parameters and wasn't getting anything completely wrong. I'm am an employed installer and MECP certified, but where I am employed we are not properly ventilated to cut wood or use resin. That being said, I do not do much custom work outside of work because I am a full time student and don't work many hours to have a bunch of supplies to just practice my fabrication skills. I do not need help with understanding basic principles such as the differences between boxes and that max power is pretty much a selling strategy. Ha sorry for all that. Just wanted to establish that I am intelligent and do not need an introduction to installing or something.

Yea I think I am just going to end up going with one since I really do not want to have it all that long. I'll probably up it to 200 watts for the one sub and probably put it in a vented enclosure. I never really see much on bracing a sub woofer enclosure. I wouldn't assume I would need much for such a lower powered sub. Could I add some fiberglass resin on the inside to increase rigidity and not loose volume for bracing?

agraves1 : "Let me know if I am completely off on something, because this is my first box I am trying to build to using t/s parameters." I guess all I comprehended was the "my first box" part, I missed that underlined part. Oh well hopefully someone will find that more helpful. I haven't braced any of the sub boxes that I have built in the past but they were all less than 3 ft3. I think it mainly depends on the specific box you are looking at and if there are any sides that are large enough to require bracing. I have built TONS of other random things out of wood and as long as you have good flush joints, GLUED & screwed (or brad nailed or biscuit or pegged) together I can't see any reason to brace a 3 ft3 ported enclosure (I would brace a sealed enclosure this size because of the increased stress(pressure) you would have increased strain (flexing)). I also think it would be a waste to line the inside with resin just use some caulk to make sure the seams are sealed. If you have access to a lot of resin at work or something then you could cover the outside of the box with just resin and sand and paint it but that just be for aesthetics. Fiberglass and resin have almost no rigidity when flat, its the curves and complex shapes that make them strong. !!! HOWEVER !!! I highly recommend doubling up the baffle or at the very least make a ring to double up around the woofer to give the screws holding the sub something substantial to hold on to. I used Tee Nuts on this box and they worked WAY better than drywall screws. To Stevdart : Thanks