Ideal sub box...

[Florida240sx]

It all comes done to the person.The bigger the box the better quality you will have.But is your need for space higher than your need for sound.The advantages of having such a huge box to a practical aren't that big.I like to have big boxes that's the way I am and wouldn't have it any other way.I'm buying a table saw this week and goign to start making boxes for all my friends.I'll make it whatever way they want.

[PoorManQ45]

Hahah, it sounds like someone's over compensating for something by building large boxes

[Silvia2b]

Actually PMQ, fiberglass is a stronger but not for flat sides of and enclosure, only for contoured surfaces. For the kind of enclosure we were discussing, MDF 3/4' or 1" MDF construction they are much heavier. To build a square or rectangle enclosure that is a least reasonably strong on the flat surfaces out of glass would require multiple layers of glass with tons of reinforcement. I know the benefits of using glass, but in most cases it is much more efficient to use MDF. I have build 100's of enclosures in the last 10 years for my customers, many of them fiberglass. I still prefer MDF, the enclosure in my car is MDF with glass reinforcement and sealing covered with Dynamat. The reasons for the Dynamat is obvious if you have ever heard a glass enclosure in person, they aren't very musical. They ring horribly. Have you ever heard of a high end speaker manufacturer using an enclosure out of anything other than wood? No, that is because most use MDF which they cover in veneers or more expensive and aesthetic coverings.

Fiberglass is cool and expensive, but for music it isn’t the best.

[PoorManQ45]

Actually PMQ, fiberglass is a stronger but not for flat sides of and enclosure, only for contoured surfaces. For the kind of enclosure we were discussing, MDF 3/4' or 1" MDF construction they are much heavier. To build a square or rectangle enclosure that is a least reasonably strong on the flat surfaces out of glass would require multiple layers of glass with tons of reinforcement. Have you ever heard of a high end speaker manufacturer using an enclosure out of anything other than wood? No, that is because most use MDF which they cover in veneers or more expensive and aesthetic coverings.

I pretty much agree. I kind of prefer 'glass for its ability to maximize the airspace while minimizing the exterior dimensions. You can't do that with MDF.

The reasons for the Dynamat is obvious if you have ever heard a glass enclosure in person, they aren't very musical. They ring horribly. Have you ever heard of a high end speaker manufacturer using an enclosure out of anything other than wood? No, that is because most use MDF which they cover in veneers or more expensive and aesthetic coverings.

The reason for that is because 'glass does not have ANY interior absorbtion properties, as MDF does. Fiberglass creates basically an echo chamber with horrible reverberations, this is why you do what you said and put Dynamat or a line of your choice on the inside. Now with MDF dynamat is not necessary, it makes a difference, but you can still go without it because the MDF naturally absorbs some of the sound.

Hey, I'm making a fiberglass enclosure right now, and I'm making the baffle right now. It's fairly flat with a little bit of a curve towards the ends. Should I just make it out of MDF(and live with the extra weight), or should I make it out of fiberglass?

[Rex]

All this talk of box sizes, what about using aperiodic mats?

[PoorManQ45]

But arn't aperiodic mats effectively Infinite Baffles?

[Rex]

The subs would mount like them http://www.usdaudio.com/tutorials/ap-tut1.php, but the do't actually function like them.

[PoorManQ45]

Ok, so essentially you just build something to mount the sub to, and then use the aperiodic mat for the rest of it, or just one side?

That's a fairly interesting idea.

How can you tell if a sub will work well in this type of enclosure?

[PoorManQ45]

Ok Rex, I just read up a bit on aperiodic enclosures and all I have to say is:

You SUCK. Man you're telling me about this after I start making a low profile enclosure. Just kidding.

Though that gives me an idea for another location for subs in the Q. Possibly where the trunk/gas tank seperator is. Would the area around the gas tank provide enough air volume though?

[Rex]

LOL, yeah I do .

I've never worked with them, as when I was big into car audio (actively) they were very new and VERY expensive. But as I recall, they allowed the use of HUGE subs in TINY enclosures. I think the AP mat needs to be as close to parallel to the sub as possible.

[Florida240sx]

I'm lost on the mat thing.Pics are confusing me.Maybe you can explain to me or give me another link.They look very interesting.

[PoorManQ45]

Ok. What can be used to make the AP mat?

[Rex]

Hmmm, I was thinking they were a "had to buy" kind of thing???

Here's some more information.

http://www.usdaudio.com/products/ap.php

And a big write up ...

A-periodic membranes are not a new concept. Though new to the mobile audio industry, they have actually been around for decades. Dynaco was the first known company to introduce an enclosure of this sort. Dynaco used a damping material in the vent which differs from the applications used today in the automobile environment.

Subwoofer systems have more "pros" than "cons". The greatest benefit of utilizing one of these membranes is the drastic reduction of enclosure size. The enclosure volume should be as small as possible. Generally, .3 ft^3 or so for a 10", .6 ft^3 for a 12" and .9 ft^3 for a 15", or smaller.

The a-periodic membrane is simply a resistive element consisting of a damping material such as spun fiberglass or duct board. The job of the membrane is to control the excursion of the driver. Since the a-p mat is not a solid material, it can "breathe" from the other side of the mat, I.e. the trunk. This allows plenty of air "access" for low bass extension. Overall, this will exhibit a flat impedance which makes response very predictable, unlike some traditional enclosures. Achieving the right response comes through tuning the enclosure via the mat, which we’ll get to in a minute. "Quick" attack, lower cone radiated distortion and smoother frequency response are a few other benefits. The transient and phase response have similar characteristics to an acoustic suspension enclosure (sealed). In essence, you have a very large enclosure, the trunk, with a resistive element that controls and damps the energy transfer.

With all of these benefits, there had to be a sacrifice. Efficiency is slightly lower than an acoustic suspension enclosure. However, most will agree that this does not outweigh the advantages that the a-p mats have to offer. The typical user of this system will be a sound quality competitor, not an SPL competitor, so this is not an unbearable loss, especially since you get the sound quality benefits of a large box with the power handling and damping control of a small box.

There are a few different applications possible. The most commonly seen is the "fire through seat" method found in sedans. Bass enters the listening area via the seat and uses the trunk as the "large enclosure". Another place for the driver is in the rear deck. When installing the driver in this location, the enclosure can be bypassed altogether by bolting an a-p mat to the front of the driver. What can you do if you own a hatchback? Easy! Use the world’s atmosphere as the rear enclosure by venting outside of the vehicle with or without an enclosure. Should you opt for the hatchback idea, be sure to put a Gortex cover over the a-p mat for protection from road elements and weather.

A-periodic membranes are still a bit new to the car audio industry and seldom understood. I believe that this "rediscovered" method of subwoofer loading will become more popular in the future.

[PoorManQ45]

Where was the AP mat enclusure used though? I mean, in all the descriptions it says that the front must be completely sealed from the back. Where can you do that in a home application?

[Rex]

The first and most notorious use, was the Speakerwork/Richard Clark Buick GN . And the solution for home use is to seal the box, the "free air" applications where the front has to be sealed from the back, are when you're using it with no back to the box, I think.