Ya know......it's so simple........you might not have thought of it......but......here it is:

MAKE SURE THE DAMN THING IS SEALED!!!

With my sealed box......I was getting some distortion on the really loud, really hard bass. It was kinda ticking me off. Luckily.....I had an idea what the problem might be.

I pushed on the cones of my speakers. And what did I hear? "Swish.....swish.....swish." Air sucking in and out of the enclosure. NOT GOOD! And I don't mean a little bit.......it was like a damn vaccuum cleaner. The guy that built the box did a ____ poor job of sealing it. Why does it matter? Because a sealed box controls the excursion of a subwoofer.......but only if its completely sealed. Sure...ported boxes let excursion roam free......but the ports are tuned to maximize the sound. A sealed box with a leak is as good as a speaker tossed on your back seat.

Anyway.........sealed the interior joints of the box with silicone........and sealed the terminals of the box with liquid nails.

Result? CLEAN......super hard hitting bass! I thought my system kicked before. Now.....it just owns my nuts.......simple as that. There was a time when I was confident that I had legal guardianship of my nuts.........but my system fought for nut custody.....and won.

KiL

 

Damn good advice. Glad you founde your problem though, I am sure it made quite a difference.

 

To the novice.....it might not seem like a big deal. I know........because there was a point in time where I thougth to myself "Oh please, does it rally matter if there's a small leak? Come on!" Now I know better! Not from reading an article. Not from being told by an "expert". But....from pure experience. And breaking it down logically........it makes perfect sense. The whole point of a sealed enclosure is to limit the excursion of the subwoofer...giving clean sound, and more flexibility in terms of the range of music you can listen to and still enjoy nice bass (I can make Simon & Garfunkel, or Billy Joel "out bump" many people's systems). This has advantages and disadvantages. However.......if you're going to enjoy the advantages........the box HAS TO BE COMPLETELY SEALED. Otherwise.....all you experience is the disadvantages. And who the hell wants that?

KiL

 

The point of sealed boxes is not necessarily to limit excursion, it's to sheild the back-wave from the front-wave.

Vented boxes take the back-wave, and in theory change the back-wave's phase to match the front wave. There is a formula behind this, which is why just a random hole in a box doesn't work (effectively) as a vent.

Vented boxes are affected even worse from leaks, as it disrupts the tuning frequency of the enclosure.

But, the point remains... the box should be sealed from air leaks, Sealed, or vented,

 

Even a sealed box doesn't protect the front wave from the back wave exceptionally well unless you use dynamat in the box.......or polyfill. I understand that concept..........but one of the main advantages of sealed enclosures is the regulation of speaker excursion. That's why in general, subs in a sealed enclosure can handle more power. They might not be as efficient with the power......but they can handle more.

KiL

 

Sealed boxes (When properly sealed) act as an airspring, helping the sub return to neutral state quicker. This is why sealed boxes sound "tighter." The subs are spending less time recovering from the last bass note.
When the woofer is moving it has to push against this "air spring", so the power requirements are higher for any given excursion value. This is why the power requirements are higher. More power doesnt equal more output but it is good for bragging. Hope that helps!


--
Cheese

 

i fiberglass the box and use silicon inbetween all board joints....havnt had one leak yet....

 

Thank you for reinforcing my point. Now people won't think I'm wrong.

But you're right.....more power doesn't equal more output necessarily.........ie, vented/ported enclosures usually being more efficient with the power they are given. But....if you want to maintain clean bass, have flexibility in the types of music you can listen too, and still be able to pound pretty hard.......a good sealed enclosure, with good subs, running a decent amount of watts is definitely a good choice. Sure......maybe you have to get a more powerful amp than you would with a ported/vented box to get the same or similar loudness (or, anywhere close in some cases)......but because of that "air spring" you mention (control of excursion), the speaker will be able to handle that power with less distortion, more clarity, and "tighter" sound.

KiL

 

Actually, this isn't entirely true. Subwoofers in vented enclosures have alot of control over the cone unless the port is entirely too large, IE 3x the cone area, where unloading can occur. Because of this, vented boxes can handle more power. The thermal power handling of a sub when in a vented box is increased due to increased cooling.

True, mechanical power handling MAY be higher at some points in sealed boxes.

Did I mention I hate sealed boxes?

 

1 box design isnt better then one of the other.....ive seen many different types of bandpass setups....horn load setups....sealed slot loaded....ported....ported sloted....all of these setups i have seen in very high spl producing cars including my own....it depends on the subs....wattage class....and type of medium u are running....the craziest design ive seen was a ported box with 3 foot port up the middle of the suv to tune the two 18's to 32hrz for spl......
they all have their place....
most efficient design ive seen was 2 jl audio 10's old school w6's in a sealed slot loaded box....they had about 250 watts rms into the two and hit 138.9db and killed everything in that class....needless to say we all know a 250watt amp at 4ohms put out allot more at .5....the w6's were dual voice coil and after hooking all coils up in parrallel he ended up with a half ohm load on the mtx amp he was running....he hit 138.9db in his class and took first in most competitions....

 

From what i have seen when building a box its best to build the box for the speakers you plan on using. Proper air space make the system sound much nicer and cleaner. Most people dont think about air space but it does make a difference.

 

I recommend getting BassBox 6 pro. I had some cheap audiovox 10's laying around to experiment with this program. Once you put in all of the info from the Drivers (fs,qms,vas,xmax, etc), it will give you optimum box sizing and type. Using the program, I put together a sealed box and these cheap 10's sounds CLEAN!!! If anyone wants a box designed, PM me the specs on the speakers, or the Model # and I can look them up. A properly designed box can make a world of difference. NEVER buy an off the shelf, generic box.

 

All points are valid and no one is incorrect. Although I would like to add that always follow manufacture specs. If the sub calls for a 1.0 cu. ft. sealed enclosure. Build it in a 1.0 cu. ft. box and seal the hell out of it. To check apply low pressure on the cone and it should rise SLOW!

If the sub calls for a ported enclosure build the sub in a ported enclosure. Not all subs will work in a sealed enclosure. Crossfire XT2 series subwoofer will best perform in a ported box. Only because the construction of the spider, cone, and suspension is more designed to be played in a port box.

Ported enclosures usually gives you +3 dB's. If you dont know how much +3 dB is. It is lke doubling your amplifier power. So if you are running 1000watts sealed a ported will act as if it is playing 2000watts.

Here is an idea of port area...



Here are some amps for you..

 

i dont remember how it is anymore...every 3db after 120db u have to double your power correct?

 

To double output (add 3 db), either you must double the power or double the cone area, assuming no other changes. Reality is that there are myriad other details that come into play, such as box design, amplifier/ subwoofer efficiency, etc... but that's the high school physics answer!

-Phil

 

What's so great about 138.9db's?

Also, there is no such thing as a sealed slot loaded box. Nor is there a ported sloted. Conventionally, there is ported, sealed and bandpass. There aren't really any variations of sealed boxes, but there are several variations of bandpass, and a few different styles of porting. There are several different orders of bandpass, the most popular being 4th order (sealed box firing into a ported chamber) and 6th order (vented firing into another vented enclosure) They both have their places, but aren't really well suited for SQ at all. There are quite a few more types of enclosures, but I couldn't possibly go on a rant about all of them.

Also, a 32hz tuning is not for SPL, it's for incredibly obnoxious output in the 35-50hz range.

I have a buddy with 2 - CHEAP Audiobahn AW1051T 10" subs, I built him a vented box for them. He took a cheap 400w Kenwood amp, which puts out less than 200wRMS lol. To add to the story, he did a 143.2 db on my meter.

Right now, my daily driving box in my grand cherokee has a single 18" Resonant Engineering HC subwoofer, in a vented box I built, tuned to 30hz for the low notes. I compete in stock 2 in SLAP, and I normally do around 152db on their meter. Keep in mind, this is all within the cargo area, below the window line with one sub...

Fun stuff....

 

Best explanation yet.

BUT, theoretically, there is more than +3db to gain form venting. Especially if you know what you're doing. Remember, the backwave is equally as powerful as the front, and the most efficient ported enclosure on earth would gain close to 6db's. Why, you ask?? Remember, the movement of the cone is the same, front and back... the 1000w powering the subwoofer, is powering both sides... Effectively, it's another X amount of cone area with the same 1000w. Now, harnessing that 6db's of acoustical energy is impossible, but with a very efficiently designed vented enclosure you could gain 4-5db's instead of 3.

 

Your correct..I just wanted to do a really brief explanation.

 

You can have an isobaric design but it may not necessarily be a different box configuration.... but I've seen some sweet open clamshells!
--
Cheese