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Sealed vs Ported


Prodigal Son
There isn't any rule stating that a sealed subwoofer is always better than a ported subwoofer or visa versa. The trick is to find a woofer that sounds good.
Cisco - in what capacity will this sub be used? For instance, are you talking a 2-channel configuration for music, a multi-channel x.1 configuration with LFE for movies or some combination of both?
I have a 12" MK acoustic suspension sub used predominately for music (2.1) that sounds very good.

It's certainly no match for a SVS or HSU, but works nicely.
Room/space constraints steared me in this direction.
A cylindrical SVS is still a possibility . . .
I generally prefer ported subwoofers with a tuning frequency below 25Hz. That means using a driver with the T/S properties appropriate for a low tuning frequency.
CiscoKid said:
If I'm wanting to build a subwoofer and am not looking for a very loud sound, just high quality, would going with a sealed subwoofer configuration be better?
Ported preferably, but either way I wouldn't buy either if not rated to a minimum of 20 hz

.... and don't forget about acoustic room treatment.
The investment is worth every hour/dollar you spend.

`. :handgestures-thumbup:
We pretty much don't deal with car audio here so what's communicated on the boards about subwoofers is intended for home use. What might sound awesome in your living room or even a dedicated room can't be replicated in a vehicle with the same equipment (I'll spare you the obvious) and vice versa.
I think it looks really expensive and there are no specs listed to allow you to model the performance for your application. I have no idea if it is good for how you want to use it.

The woofer you choose has to be designed to perform best for the applicaiton you use it in. For car woofers in smaller sealed enclosures that usually means a higher Qts (0.4 to 0.5), moderately low Fs (25Hz to 35Hz), high expersion (15mm or more) and high power handling (over 300 watts IEC).

What I would do is design the enclosure to fit the area in the car you want to place it. Design it to be as large as you can fit and be comfortable with. Then take that internal volume and model it with a bunch of woofers to see which one has the highest SPL before reaching excursion limits and which has the highest peak in the output at 35Hz and which has the highest relative SPL at 20Hz. That is your most ideal woofer. Be sure to take into account the volume the woofer will displace in the enclosure when modeling.
That is a good approach Flint. I like that idea, especially for adults that want some performance but dont want to give up all the storage space in their vehicle.
Really cheap? Dude!

For car audio you don't necessarily want the ideal sealed volume performance. Most people enjoy the sound of a smaller enclosure with a 3dB to 5dB peak in the 30hz to 36hz range and a bit of a sacrifice in output below 25hz. In a moving car you cannot hear bass below 30hz over the road noise unless you crank the sub anyway. Try modeling a 3 cu.ft. enclosure with the 15" titanic (fully stuffed with damping) and see what you get. If you don't desire a high SPL boomtruck, then one woofer is way more than enough.
I don't do car audio, so I don't know all the options.

I do know the common desire for high SPL subs in cars is pointless and not about enjoying good music. I cannot imagine putting a 15" woofer in any carif the goal is high fidelity (accurate and realistic sound). Personally, I would use a very good 12" sub with a welltuned, designed and built enclosure following the principles of Dr. Small. Morel makes a great 12" sub driver, as does SB Acoustics. Look into those.

You need to use a computer program to model the subs in size of enclosure you have designed for your car. You need to calculate the peak output at 30 hz (not 20 hz). You need to calculate the SPL with the size of amp you are using. Then you'll know which sub is best.

Try the linear team online. They have all the calculators you'll need except one to calculate excursion.
Yea, Flint may know a thing or two about speakers and that type of stuff. But then again he is a Texan and you know what they say about Texans! :teasing-tease: Stick around and see how far the rabbit hole goes!
CiscoKid, Just wondering how you found this place? Its not really a easy place to find? There is a lot of very knowledgeable folks around here who will help you spend your green backs! More so towards the home audio side! Lord knows I have lost a few because of these people! :mrgreen:
I recommend using MDF for the enclosure. It has the best properties of the affordable materials for this application, plus it is easy to work with. Since the sub will be in a car, I recommend sealing the MDF, especially the edges, with spray on shellac - both inside and out.
Use yellow wood glue to hold the MDF joints together. Then, use caulk liberally to plug up any leaks. The, after all of that is dry, use shelkac to seal the porous MDF so it doesn't absorb moisture and expand, rot, or fall apart.
For car audio box's I also use a full can of car undercoat. It helps to reduce the resonating frequencies. along with bracing the box you will be set.
Flint said:
Use yellow wood glue to hold the MDF joints together. Then, use caulk liberally to plug up any leaks. The, after all of that is dry, use shelkac to seal the porous MDF so it doesn't absorb moisture and expand, rot, or fall apart.

I have a question related to this for the system i am trying to put in my boat. Can you shellac (sp?) the MDF and then paint it white with a high quality exterior paint.

I will use Rhino Liner of something similar for the sub boxes, but i need to make 4 speaker rings that will be exposed to sun, humidity, maybe a little rain and spray from time to time.
Yes, shellac is and excellent primer for MDF. It is what I treated my home speakers with when I made them. I started with several coats of shellac let it dry thoroughly, then used black lacquer on them, sanding with fine sandpaper between coats, then applied high gloss poly on top of that to finish them off.
I have never used the shellac, it sounds like thats for the outside. I just use the wood glue, screws, liquid nail to seal all the inside seems then undercoat it inside. I have never personally even brassed the inside of a box but, Flint and others have said it should be done. I just hate math and accounting for all that.
Shellac is preferred for MDF because it is just the right consistency to just soak in a little bit and dry hard. Most other paints, primers, coatings and liquids are either too light and soak in too much and expand the MDF as it acts like a sponge, or it is too thick and doesn't soak in enough and fails to hold the seal over time. Shellac, specifically the aerosol cans, is prefect for sealing and protecting the MDF as a base coat or primer.