Hi I have been into car audio for years and building subwoofer boxes for me and quite a few of my friends. I want to build some sub boxes for 2 JBL 2226H's that I have but I can't seem to find any nice web sites on designs for home theater. If I look up subwoofer boxes I tend to get a lot of car audio sites but nothing on home theater. I know I could just try building the box with the space calculators on car audio sites but they take into consideration the fact that they are going into a car and the car acts like a box. A large room almost has the characteristics of open air and the calculations should be defferent if I understand it correctly.
I know that doubling the speakers in a car they add 6db for the gain as a rounded off number but in a house it is 3db. Not sure if it makes a big enough difference to worry about but I thought since this is a do it yourself forum you guys might know of a place that can help me design a simple ported enclosure for my speakers.

Thanks for any help you can give me.

Decware has some cool sub plans. The sonotube subs are pretty neat too.

Ditto Kingofswords, I built a Decware Deathbox 12'' and am happy with it. If I didn't build that I would have built a Sonosub with a Adire Audio Shiva. There HUNDREDS of websites on building your own home theater subs. Shiva's seem to be the sub of choice for most DIYers. That's what I use and would suggest it to anyone.

www.adireaudio.com
www.decware.com
www.partsexpress.com (makes a shiva copy called the 12'' DVC from Dayton Audio).

-Jim

diyaudio
More than you'll ever want to know.
Most everything here is using partsexpress parts.

You need The Loudspeaker Design Cookbook by Vance Dickason

http://www.amazon.com/exec/obidos/tg/detai...=glance&s=books

Sure it's expensive, but it's really quite good.

Also, what kind of box do you want? Vented? Sealed? Do you have the Thiel/Small (sp?) parameters for the driver in question? These parameters will allow you to model the speakers response and compare it to that of others.

Shiva's are great too. I did blow one up once. I put about 2000 watts into it. Don't do that!

Going from old memory from here on, may be inaccurate:

One of the most important in the resonant frequency, it's hard to get response below that.

kingjamez, I built a 10" Deathbox a couple years ago. I recently upgraded the amp and now it sounds really crappy. I think I have to re-tune it. Still, it was easy to build and was pretty decent when it was working. I'd love to make a sonosub one day when I have room for one.

I have used Bassbox to design my subs - both home and auto. It can be found here. I have been very pleased with the results. Sure, it will cost you a little money up front, but it is nice to be able to "see" what changing the variables will do the sound. For my HT I tuned 2 subs to one frequency and 2 more for a bit higher to create an overall smoother response pattern. Lots easier to plug in some #'s to a cpu program than fiddle with all that math...

I wanted to do a vented enclosure as that is what JBL recommends. I know that its hard to go below the resonant frequency but not in all cases. I have seen that this particular driver in the cabinets you buy it in in a much higher frequency cabinet than what I have heard of people getting out of it at home. I think its because it has a pretty flat response in the low end. The speaker is designed for pro audio applications like a live concert and so they typically focus on the audible frequencies. But many people have thought this particular driver to be great for home theater and they focus on the inaudible rumble your butt frequencies. So I am looking for the later in my home. I have seen a few box dimension calculators but they typically base it on the resonant frequency and I would like to obviously tune it a bit lower than that. Anyway the speaker is as follows.

JBL 2226H
Nominal Diameter: 380mm
Impedance: 8ohms
Power Capacity: 600 W AES Continuous Pink Noise
Sensitivity: 97db spl 1w 3.3 ft
Freq range 30hz - 2.5 khz
highest ecommended crossover 1200hz
Recommended enclosure volume 85-285 (3-10ft)
effective piston diameter:335 mm
Max Excursion before damage: 1.6 inch
minimum impedance 6.0 ohms
voice coil diameter 100mm (4 inch)
Voice Coil Material: Edgewound aluminum ribbon
fs: 40hz
Re: 5.0 ohms
qts:0.31
qms:5.0
qes:.33
Vas175 (6.2ft)
S:0.088m(137inch)
Xmax:7.6mm (.30 inch)
V:689cm(41 in)
L:.1.75 mH


and lots more found here



http://www.pispeakers.com/JBL_2226.pdf

If you own your own home you can try a IB subwoofer.

Cult of the Infinitely Baffled


peace

Good stuff comparing different alignments:
http://www.danmarx.org/audioinnovation/theories.html

Other random stuff, including plenty of Excel sheets to do all of the response, etc. calculations for you.
http://www.diysubwoofers.org/

Beware of anyone who tells you that you can get much below your Fs (anechoic anywho). The reason you really don't get much is because below the lowest resonant frequency (yes there are many!) the inductance is the prominent component of the impedance. An inductor looks like a short to low frequencies. The lower the impedance, the lower the voltage drop, and thusly the lower the power absorbed by the voice coil. Since this power absorbed by the voice coil is turned into sound, less power means less SPL.

Don't get me wrong, you'll still get energy out of this beast at lower frequencies, just not as much. Which raises the question, do you need as much energy to feel lower frequencies as you need to hear them? I have no idea!

Hope this helps!

Brett

Thanks Brett that looks like some cool info I will check it out.

As far as the efficiency of the woofer at lower freqs I am not to concerned about it. One if the efficiency of the box boosts the freqs below the resonant req then you can squeeze out decent efficiency because of the standing waves in the box. Yes the coil will need to draw more current but with the added resistance of the standing waves in the box it can still be useable. I have seen a set up with my speakers tuned to 25 hertz which is almost an octave below the resonant freq. His setup was quite efficient and didn't use a lot of power. But these speakers can handle way more juice than I would care to give them and I got plenty of juice to give. Anyway I appreciate the info and I will try to post my results when I get to it. I think to 15" subs like these could really rock the house.

i have the sub and amp sold by parts express to build the "Titanic 12 mkIII"
Anyone have experience with this? It sounded good from some reviews I read.

Hi,

I'm not exactly an expert, but I have been learning a lot about building home theatre subs over the past year. I just finished my Tempest based sub, and I love it. You should definately check out Adire's line of drivers, as they are an awesome deal for the price.

I believe the JBLs you have will be much better suited to music as opposed to Home Theatre. The Xmax of your drivers will only give you an air displacement of 1.3 litres each. The Adire Tempest has an air displacement of roughly 2.55 litres and an fs of 18.8. I built mine into a 9 ft^3 cabinet with dual 4" ports, and it will make my window glass blur below 20hz in a room 24'x12'x8'. Around 10hz it get's violent .

I'd like to see how it turns out with these drivers! They appear to be designed for PA use. These things will go LOUD above 40hz.

There are some Sub Plans here
Home Theater Talk
Adire Audio