rxmadness

iTrader: (1)

i just made my sub box to the specs of my sub(1.45cu) but now looking at the specs for a port i have a question.....the sub requires a port that is 3" diameter by 9" length but i dont have enough room for a port like that because of the angles and shape of my custom box... so my question is if instead of one port(3"x9") i used two ports(1.5"x4.5") would it have the same sound? i know the area would be the same but would this effect sound? also im planning on using 1.5" carboard tubing to reduce that bouncy noise that you get from pvc.

thanks

SinSFDream

iTrader: (9)

Sorry to say it does not work that way. There is a calculator out there for port dimensions and length. If you have a single sub, then you must use a single port from my experience. If you had two subs in a box you would use a single port also unless each had its own chamber and you could use one for each.

Ported/bandpass boxes are tricky and picky. Your box sounds big at 1.45cu. Im guessing it has to be a 12 or 15. The rated 1.45cu would be for net air space also without port and speaker displacement so you must take that into account. If your port takes up .25cu then you must make the box that much bigger. You left out what you are trying to tune the sub to, but I assume its in the range of 34-36Hz from the info given.

You say its a custom box with angles which is why I assume you are trying to use round ports. Almost all ported boxes use a single slotted port now. Mainly because you dont run into the problem you are having with the length of the port not fitting the box if round. Im not sure who made/designed your box but it sounds like you'd be better off leaving it a sealed enclosure although the air space may be too much. I dont think there is an easy solution. There are many variables to look at prior to building the box as all subs have different specs for each application. Porting a box after the fact almost never works due to air space and not being able to have a correct length port.

dohckiller808

lets see some pix.

you could use bends in your pipe to make your 9" if you dont care about it sticking out of your box, you could even have port outside.

rxmadness

iTrader: (1)

thanks for the info guys ive decided to start over so i scrapped the box and built a new one, this one a much simpler design, the new one is .88 cu feet with the displacement of the sub and its staying a sealed box. my sub requires .75 cubic feet for a sealed box but ive always preffered to have a little more room and a little more insulation its the best for my sound likings. i am using a 10" power acoustik DVC sub set to 4 ohms with just a small 800 watt amp bridged at 4 ohms to it and im looking for about 43 HZ but thats because this system will only be pounding rock and country with sharp quick bass. ill be setting up the system when i get some time this month.

installer67

iTrader: (18)

If space is a premium, you might consider using a different shape "tube" for your port, or designing it to bend to accomodate space. In my experience, as long as you don't go more than 45 with the bends, it has negligable affect on sound. I've built them with rectangular, trianglular, oval and tapered ports. But the lengths get tricky to figure in tuning when you go "outside the box". (pun intended)

dohckiller808

tunings the same. speaker sees whatever amount of air space before the port. look at slot ports for example. the only difference in the port is that you use the enclosure wall as the outer part of the port.

so whats the difference if the port is build out side of the air space needed for the sub?

juicyjosh

iTrader: (29)

rxmadness,

Ported boxes are more efficient (i.e. louder per watt) within a narrow bass frequency range as facilitated by the port(s), so you get unusually loud bass from as little as 50 watts RMS, but the result is often loose, "one-tone" bass. The downside, aside from requiring a huge box, is that the quality of the music is not so easily achieved, by far, compared to a sealed box. For someone starting out in car audio, and even for a lot of "professional installers," the result is music with bass notes that manifest themselves at different volume levels throughout the entire song.

By comparison, consider the 10 in a (smaller, lighter) sealed net 0.9 - 1.0 cubic foot box. You'll hear and feel a wider range of bass, tighter bass kicks, more consistent output at different bass frequencies, and more accurate bass reproduction across your low pass, when compared to a ported box. This is due to the cone being more controlled by what can be considered a stiffer spring of air inside the smaller box, as well as different acoustic dynamics compared to a bandpass.

That being said, "800 watts" might only be 400 RMS, which is a LOT for any 10 to handle. I blew up two 15" MTX voice coils, installed in 1.4 cubic foot sealed enclosures, each independently powered by 500 RMS, both with just an hour of rock music. From experience, even 300 RMS is pushing it for a 10, regardless of what it says on the side of the speaker box. You'd need to also upgrade your mids and highs to keep up with your sub. Other considerations would be major capacitance protection for your battery and your amplifier, and blowing your alternator. I've destroyed 4 batteries, two alternators, and more amplifiers and speakers than I can remember when I was "learning." That was a long time ago, but I wished I had learned from other people's mistakes - and money.

I'd have to say that asking a 10 to specialize at 43Hz is also pushing the limits of physics. You can't make a 10 sound like a 15, but there's a space limitation

It comes down to what are your goals and your budget and the results you would like to get from your installation.

dohckiller808

^^^ you might of blown your subs from under powering. there are a lot of 10" subs that handle 1000 watts rms like champs. ex. re sx, dd 3510, dd9510, atomic and the beat goes on. it all depends on the motor of the driver as a lot of 15" subs have small motors like rockford p1 which tops out at 250rms

more people blow their subs under powering because they dont know when to back off. sending a clipped or dirty signal to the speaker.

installer67

iTrader: (18)

"outside the box" was meant as "unconventional thinking", not literally speaking. LOL And tuning becomes difficult (as compared to oval or square), because it's a bit harder to find the volume of say a star or strange shape, than a standard square or oval. So, there is a little trial and error involved when you go for "unconventional". Not to mention that in audio, what works on the calculator doesn't always translate into sound well, too many variables involved.

dohckiller808

still no different... i always build test boxes then port outside for ease of tuning. that way the speaker doesnt see a change in air space as you cut down or add on to the port.

its much harder to build port in cause you got one chance to hit you target freq.

EDIt: ^^^ opps i didnt read what you posted correctly.