Help with sub box

[camaro01]

I know this might not be the best place but im buliding a speaker box for some subs for my car. Im wondering about a good place to get some help on getting the right size box ?

 

[TLS Guy]

I know this might not be the best place but im buliding a speaker box for some subs for my car. Im wondering about a good place to get some help on getting the right size box ?

What speakers do you have and can you get the Thiel/Small parameters for them?

 

[camaro01]

Yea they are audiobahn alum12. I know there not great but they where free . I thought about since i have them putting them in my jeep. Here is a link to the parameters http://www.audiobahn.com/Audiobahn06/images/tech/2004/theileSmall/ALUMQ_sub_specs.pdf Any help would be great . Im wondering like what would be the best a round port or square. Also like with the 2 subs so would it be best to have the chambers seprate or togather with one port .

 

[highfigh]

Yea they are audiobahn alum12. I know there not great but they where free . I thought about since i have them putting them in my jeep. Here is a link to the parameters http://www.audiobahn.com/Audiobahn06/images/tech/2004/theileSmall/ALUMQ_sub_specs.pdf Any help would be great . Im wondering like what would be the best a round port or square. Also like with the 2 subs so would it be best to have the chambers seprate or togather with one port .

What model of Jeep? If it's a CJ or similar, you'll want a Qtc of about .85 -1.1 in order to not have it sound like the box is out in your yard. A Qtc that works inside of a building is not what you need. If you have the materials, tools and opportunity, you might try a down-firing configuration and if you use that, you can use a slightly lower Qtc.

The drivers' parameters determine the box size and whether it needs ports. The box size, along with the driver's parameters will determine the vent length and diameter. If it's not practical, it's not worth doing because the results won't be good. A tiny box may be what is needed but that usually needs a vent that's not practical and if the wrong compromises are made, the woofer's power handling will be close to nothing. Whether it's square or round is less of an issue than box size and configuration.

Since you posted the link to the specs, look at the bottom- they already have box sizes. I'd bet that the power handling is a bit optimistic, though. Woofers made for tiny boxes are typically designed to be in a trunk, which acts to project the sound into the passenger compartment. Not saying they won't work in your Jeep but it won't hit as hard as if it was in a trunk of a car and it's apparent deep bass won't seem as low as if it was in a big car.

 

[TLS Guy]

Yea they are audiobahn alum12. I know there not great but they where free . I thought about since i have them putting them in my jeep. Here is a link to the parameters http://www.audiobahn.com/Audiobahn06/images/tech/2004/theileSmall/ALUMQ_sub_specs.pdf Any help would be great . Im wondering like what would be the best a round port or square. Also like with the 2 subs so would it be best to have the chambers seprate or togather with one port .

These drivers are only suitable for a sealed box. You need to wire the voice coils of each of the drivers in parallel and then the two speakers in series.

The box volume for two drivers will be 2.25 cu.ft. This does not include braces, so the volume of the braces will have to be added to the box volume. The box will need completely filling with Polyfill to the point just short of compression of the fill.

This is not a very good sub. The frequency response peaks at 100 Hz, and F3 is 45 Hz. The driver is xmax limited by 30 Hz so there is not really any room for Eq unless you play it quietly. Power handling for two drivers is only 30 watts by 20 Hz.

Graphs of your sub are attached below. You will have to decide if this project is worth pursuing.

 

[highfigh]

But it does work pretty well between 50Hz and close to 200Hz, which is fine for the vehicle he wants to put it in. The power at 20Hz wouldn't be a problem if an active 12dB/octave HP is used at about 40Hz- by the time it goes down to 20, the power won't be an issue (some amps and equalizers have this built in, but most cut the bass off at about 15Hz-25Hz). Flattening the hump with an equalizer would make it less of a "one note wonder", too. It's not practical to expect 20Hz in a basically open vehicle and since most music has little in that last octave, it should work fine.

What about a couple of Vario-vents?

 

[TLS Guy]

But it does work pretty well between 50Hz and close to 200Hz, which is fine for the vehicle he wants to put it in. The power at 20Hz wouldn't be a problem if an active 12dB/octave HP is used at about 40Hz- by the time it goes down to 20, the power won't be an issue (some amps and equalizers have this built in, but most cut the bass off at about 15Hz-25Hz). Flattening the hump with an equalizer would make it less of a "one note wonder", too. It's not practical to expect 20Hz in a basically open vehicle and since most music has little in that last octave, it should work fine.

What about a couple of Vario-vents?

I'm not a fan of variovents, I think it will make the ripple worse.

I agree for car use this will be OK. It will need to be rolled off below 40 Hz though, to prevent driver damage.

 

[highfigh]

I'm not a fan of variovents, I think it will make the ripple worse.

I agree for car use this will be OK. It will need to be rolled off below 40 Hz though, to prevent driver damage.

Might be worth trying the vario-vent, since the hole could be plugged if it doesn't work. It's a long-throw woofer, so I kind of doubt it was designed for this application. The amount of road/wind noise will obscure most of the problems, so I think it's worth doing. It's all about the compromises, anyway, so why not?

 

[TLS Guy]

Might be worth trying the vario-vent, since the hole could be plugged if it doesn't work. It's a long-throw woofer, so I kind of doubt it was designed for this application. The amount of road/wind noise will obscure most of the problems, so I think it's worth doing. It's all about the compromises, anyway, so why not?

Why not, is because the drivers are fairly high Qts, (soft suspension) with a low xmax, 14mm for that type of driver. I think below 50 Hz they will need all the back pressure they can get to restrain cone movement and prevent damage.

Variovents have really fallen out of favor. They are not a ported enclosure, and in a sealed enclosure you really need all the spring the air in the box can provide. I personally would just stay with a totally sealed enclosure.

 

[highfigh]

Why not, is because the drivers are fairly high Qts, (soft suspension) with a low xmax, 14mm for that type of driver. I think below 50 Hz they will need all the back pressure they can get to restrain cone movement and prevent damage.

Variovents have really fallen out of favor. They are not a ported enclosure, and in a sealed enclosure you really need all the spring the air in the box can provide. I personally would just stay with a totally sealed enclosure.

I know it's not a vented enclosure- a Vario-Vent is kind of like a limited/dampened air leak in a sealed box. If the seal is good, they shouldn't shred themselves but again, they're designed to be located in a trunk-mounted box, which helps the lowest frequencies transfer their energy to the passenger compartment better than they do in free air.

Let's face it- a Jeep isn't what the woofer manufacturers live for but good results can be had, depending on the desired sound and type of music played.

 

[camaro01]

It's actually going in a grand cherokee so it will be enclosed .

 

[annunaki]

I suggest different drivers unless you already have them.

2 JL Audio 12W1v2's in 3.5ft^3 (net) vented enclosures each (tuned to 24hz would wallop those drivers and only need 400 watts rms to do it. Anechoic response +/-3db from 25hz-83hz. Output in the range of 107db-110db each. Anechoic output with two of them would be in the 116db range. Add in the +20db gain or more from being in a vehicle and watch out!!

 

[highfigh]

It's actually going in a grand cherokee so it will be enclosed .

That would have been helpful at the beginning, actually. If you use these, don't use a box that's too small- you want the Qtc to be as close to .7 as possible. It will sound better for a wider variety of music that way.

 

[TLS Guy]

That would have been helpful at the beginning, actually. If you use these, don't use a box that's too small- you want the Qtc to be as close to .7 as possible. It will sound better for a wider variety of music that way.

Actually the box I designed has a Qt of 0.707.

Type: Standard one-way driver
Company: Audiobahn
Comment: Sound Q series
No. of Drivers = 2
Mounting = Standard
Wiring = Series
Dual voice coils = parallel
Fs = 24.4 Hz
Qms = 4.8
Vas = 76 liters
Mms = 186 g
Xmax = 14 mm
Sd = 490 sq.cm
Qes = 0.52
Re = 2.7 ohms
Le = 2.7 mH
Z = 3 ohms
Pe = 1000 watts
Qts = 0.47
1-W SPL = 85.1 dB
2.83-V SPL = 89.9 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 1.888 cu.ft
Qtc = 0.707
QL = 18.1
F3 = 45.19 Hz
Fill = heavy

The speakers displace 0.36 cu. ft. hence the need for a 2.25 cu. ft. box. Bracing will increase that volume accordingly.