I'm planning to have a sub box made to put in the rear footwell behind the drivers' seat. And I'm currently enamored with the idea of twin 8" opposed for force canceling. At external dimensions of about 9x12x20" that means let us say 0.84 cubic feet, which would be 0.42 cubic feet per woofer, ignoring any stuffing effects for now.
Here are three quite different woofers to consider:
https://rockfordfosgate.com/products/details/p2d4-8/ which I can get FREE!*
https://www.parts-express.com/Dayto...-Series-HO-Subwoofer-8-ohm-295-459?quantity=1
and the seemingly unsuitable
https://www.parts-express.com/LaVoce-WAF082.00-8-Woofer-8-Ohm-293-714?quantity=1
Can someone kindly simulate these with actual SPL?* Just a simple model, never mind inductance and all that, and never mind Xmax. Please feel free to comment about those things! But my interest here is what happens just like below 80 Hz, I am curious. Suggestions about a single 10" or 12" also welcome as alternatives to the twin 8"
Domo arigato!
*(I plan to install WinISD but have some problems with that since the machine is at work and I need IT Department to install it. But if the Rockford is good enough I can ask for that later this week 😀
If I simulate at https://speakerboxlite.com/subwoofer-box-calculator/tab-graphs the curves all look the same at the low end since they are all below resonance. The LaVoce looks "lower" but this simulator does not do actual absolute SPL, and if I offset the zero level it seems maybe it would be almost the same at very low frequencies.)
BONUS questions:
3/4" material? Or 1/2" material to gain a bit more internal air space? Or give up a bit more for super solid 1" material? Presume internal bracing and anti vibration goop (what goop though? I'm out of touch with this)/
Here are three quite different woofers to consider:
https://rockfordfosgate.com/products/details/p2d4-8/ which I can get FREE!*
https://www.parts-express.com/Dayto...-Series-HO-Subwoofer-8-ohm-295-459?quantity=1
and the seemingly unsuitable
https://www.parts-express.com/LaVoce-WAF082.00-8-Woofer-8-Ohm-293-714?quantity=1
Can someone kindly simulate these with actual SPL?* Just a simple model, never mind inductance and all that, and never mind Xmax. Please feel free to comment about those things! But my interest here is what happens just like below 80 Hz, I am curious. Suggestions about a single 10" or 12" also welcome as alternatives to the twin 8"
Domo arigato!
*(I plan to install WinISD but have some problems with that since the machine is at work and I need IT Department to install it. But if the Rockford is good enough I can ask for that later this week 😀
If I simulate at https://speakerboxlite.com/subwoofer-box-calculator/tab-graphs the curves all look the same at the low end since they are all below resonance. The LaVoce looks "lower" but this simulator does not do actual absolute SPL, and if I offset the zero level it seems maybe it would be almost the same at very low frequencies.)
BONUS questions:
3/4" material? Or 1/2" material to gain a bit more internal air space? Or give up a bit more for super solid 1" material? Presume internal bracing and anti vibration goop (what goop though? I'm out of touch with this)/
Don't forget to allow for the volume the drivers take up in the box, a pair of 8" could use up ~160 to 200 cubic inches (over 3 liters) depending on cone and magnet shape and size.
Stuffing can increase the virtual box volume ~15%, in a small box the drivers may occupy more than that space.
Some of the volume gain reducing from 3/4" to 1/2" will be lost to additional bracing required to be as stiff. Going to 1" is not worth the stiffness/volume loss in small cabinets.
Assuming the drivers can handle the power, in a sealed cabinet, their displacement (Sd times Xmax,) determines potential output SPL(sound pressure level). Sd is effective cone area, Xmax one way linear displacement, usually given in MM.
Doubling displacement adds +6dB output, but often will take more than +6dB (4 times) the power to achieve.
Below ~40Hz, +6dB will sound more than twice as loud.
Xmax ratings are not always consistent between manufacturers, but the three choices you listed Xmax seem reasonable.
The smaller the box, the more power required to achieve the same displacement.
Sim programs can make that determination, but this calculator makes it easy to determine the output limits of any size driver at any frequency:
http://www.baudline.com/erik/bass/xmaxer.html
One 12" would have ~1dB more output than 2x8" with the same excursion/Xmax.
The Baudline Piston Excursion calculator uses Vd = (.83 * diam)^2 * pi / 4 * Xmax to figure displacement, smaller large displacement cones effective diameter (Sd) may be less due to the relatively larger surround diameter.
In a vehicle, "cabin gain" may counteract much of the low frequency rolloff, but any sealed box will likely need EQ to get the desired response.
Stuffing can increase the virtual box volume ~15%, in a small box the drivers may occupy more than that space.
Some of the volume gain reducing from 3/4" to 1/2" will be lost to additional bracing required to be as stiff. Going to 1" is not worth the stiffness/volume loss in small cabinets.
Assuming the drivers can handle the power, in a sealed cabinet, their displacement (Sd times Xmax,) determines potential output SPL(sound pressure level). Sd is effective cone area, Xmax one way linear displacement, usually given in MM.
Doubling displacement adds +6dB output, but often will take more than +6dB (4 times) the power to achieve.
Below ~40Hz, +6dB will sound more than twice as loud.
Xmax ratings are not always consistent between manufacturers, but the three choices you listed Xmax seem reasonable.
The smaller the box, the more power required to achieve the same displacement.
Sim programs can make that determination, but this calculator makes it easy to determine the output limits of any size driver at any frequency:
http://www.baudline.com/erik/bass/xmaxer.html
One 12" would have ~1dB more output than 2x8" with the same excursion/Xmax.
The Baudline Piston Excursion calculator uses Vd = (.83 * diam)^2 * pi / 4 * Xmax to figure displacement, smaller large displacement cones effective diameter (Sd) may be less due to the relatively larger surround diameter.
In a vehicle, "cabin gain" may counteract much of the low frequency rolloff, but any sealed box will likely need EQ to get the desired response.
That's an interesting data point-which would sway me to keep towards the 2x8" for the force canceling. In one home setup we have an SVS SB-2000 Pro. We quite like it but one day I was looking at the cabinet next to it and noticed how much the cone moved and then felt there was a LOT of force/motion going on. Plus the 2x8" firing to the side would always have some air space open. And come to think of it, I could make the box a tad deeper than with a front-firing sub where I would need to leave some excursion room and air space behind the seat.
Yeah if this rain stops I realized I better at least cut a proposed cross-section out of cardboard, to be sure it fits. Likewise a picture
Exactly!
Also keep in mind the lavoce woofer is not a subwoofer thus has high efficiency, but also quite high fs and "average" xmax.
I used a box, realized 9" depth doesn't give me much seat/seatback adjustment. Still going to go for opposed 8" but get the woofers first and figure the minimum depth. Might mean 1/2" material depending on the depth of the "vertical" part of the mounting lip.
Well I have a feeling that at the lowest frequencies the efficiency may be...the same! Or really similar. But I am not yet set up to do absolute SPL simulations like WinISP or such. Gotta get the IT guys at work to install that for me due to admin privileges, if I didn't mention that already.
I can’t quite picture your layout. Also, since you have access to RF, how about the pancake drivers?
I have always considered even the most intricate cat install as easy due to the fixed environment. Contracted on a lot of fibre glass cabs molded to car interiors. If you have ambitions for something like that then let’s do it 😀
Q seemed high, but on second glance maybe workable. I'll take a look. I thought about fiberglass which could yield more internal volume...then again I know a high school wood shop teacher who can have an enclosure made for me for free (well I donate stuff actually but quasi-free). Plus then I can move to another vehicle with a different internal shape.
Argh I keep forgetting to take a picture of the rear footwell.