OK, so here I go with my first PA Sub Build. Desired outcome is to have 4 double 18 cabs similar to size of the BassBoss SSP218. I have the dimensions for my cutlist for the panels. I plan on using either 1/2" ply or 5/8" ply. I have 4 B-52 18-180L By Eminence 18's. Rated at 800W RMS. My questions are as follows:
1. Why is the cab so deep on the BassBoss SSP218?
2. Does my cab have to be that deep as well?
3. The BassBoss cab has 3or4 rather large fuses inside. Do I need to put fuses in mine? I assume the fuses are to protect the subs from overpowering them...?
4. With the subs I am using, will a cab that big be a bad thing??
Dimensions are H 48" x W 23.75" x D 29.75"
I understand that the BassBoss cab uses Faital Pro sub rated at 3000w rms I believe.
1. Why is the cab so deep on the BassBoss SSP218?
2. Does my cab have to be that deep as well?
3. The BassBoss cab has 3or4 rather large fuses inside. Do I need to put fuses in mine? I assume the fuses are to protect the subs from overpowering them...?
4. With the subs I am using, will a cab that big be a bad thing??
Dimensions are H 48" x W 23.75" x D 29.75"
I understand that the BassBoss cab uses Faital Pro sub rated at 3000w rms I believe.
Hmm, [4] double 18 = [8] woofers, so short [4] or typo?
I notice you cab dims are different than BBs, is this intentional?
Really need 3/4" [ 18 mm] no void plywood such as Baltic Birch, Apple or marine grade same as BB uses [no Home Depot, etc., grade]
Thinner panels will require significantly more bracing, especially if using relatively limp plywood with voids, so probably little, if any weight savings and [a lot] more work.
Drivers require 'X' amount of acoustic 'cushion' based on its Vas, Qts specs, but in this case width x depth is fixed for dolly cart truck packing, so difference must be added to height: BASSBOSS SSP218 Dual 18" Powered Subwoofer | Guitar Center
Yours only needs a 7.875" x 1.5 = 11.81" i.d. depth to clear the driver, vent though.
You'll need some form of protection, but due to the driver's low Xmax spec, these drivers can't handle but a fraction of its 800 W rating below ~70 Hz in a technically correct cab alignment, so doubt you'll need more than a digital high pass filter.
Actually, the cab is considered to be way too small based on T/S theory, requiring ~762.34 L net Vb [26.922 ft^3]/dual woofers tuned to 33.2 Hz, so even larger with vent, bracing.
The pioneers determined that a Vas/1.44 net Vb has the best trade-off between size, power handling if tuned to Fs, so based on the published Vas it can be considerably smaller: 2*10.6 ft^3/1.44 = ~14.722 ft^3 [416.88 L] tuned to Fs, so with a single ~772 cm^2 [20"^2] duct vent x [21.3 cm [8.375"] long based on published Fs, though should be tuned to actual Fs for best performance if not close.
This is an under-damped alignment, so will require some EQ to flatten out its mid-bass peaking, but now the drivers can handle much more power; 400 W/driver, simming > 122 dB/m/2pi/32 Hz - up and the full 800 W/driver to boost ~100 Hz- up if desired.
GM
I notice you cab dims are different than BBs, is this intentional?
Really need 3/4" [ 18 mm] no void plywood such as Baltic Birch, Apple or marine grade same as BB uses [no Home Depot, etc., grade]
Thinner panels will require significantly more bracing, especially if using relatively limp plywood with voids, so probably little, if any weight savings and [a lot] more work.
Drivers require 'X' amount of acoustic 'cushion' based on its Vas, Qts specs, but in this case width x depth is fixed for dolly cart truck packing, so difference must be added to height: BASSBOSS SSP218 Dual 18" Powered Subwoofer | Guitar Center
Yours only needs a 7.875" x 1.5 = 11.81" i.d. depth to clear the driver, vent though.
You'll need some form of protection, but due to the driver's low Xmax spec, these drivers can't handle but a fraction of its 800 W rating below ~70 Hz in a technically correct cab alignment, so doubt you'll need more than a digital high pass filter.
Actually, the cab is considered to be way too small based on T/S theory, requiring ~762.34 L net Vb [26.922 ft^3]/dual woofers tuned to 33.2 Hz, so even larger with vent, bracing.
The pioneers determined that a Vas/1.44 net Vb has the best trade-off between size, power handling if tuned to Fs, so based on the published Vas it can be considerably smaller: 2*10.6 ft^3/1.44 = ~14.722 ft^3 [416.88 L] tuned to Fs, so with a single ~772 cm^2 [20"^2] duct vent x [21.3 cm [8.375"] long based on published Fs, though should be tuned to actual Fs for best performance if not close.
This is an under-damped alignment, so will require some EQ to flatten out its mid-bass peaking, but now the drivers can handle much more power; 400 W/driver, simming > 122 dB/m/2pi/32 Hz - up and the full 800 W/driver to boost ~100 Hz- up if desired.
GM
Eventually I want to have 4 double 18 cabs. For now, I’ll start out with 2. Dims are a hair smaller than the BB cabs intentionally. So if I read correctly, these subs I have will not have much output past 70hz? Like I said, this is my first build and I’m learning a lot already. I’m a little fuzzy on the vent opening size and depth for each sub. Can you assist on that? Thank you for your advise and input. I have not purchased the wood yet. Glad I posted this before hand. Now I know exactly what not to get.
xmax is very low for an 18" at 5 mm which will limit your low bass output so you will want to use a high pass filter set to ~fs (36Hz also the same as your port tuning). You may also have excursion problems above this frequency at high power levels. Its worth simulating the design in hornresp to check all this out:
Hornresp for Dum... hmm... Everyone 😉 - Home Theater Forum and Systems - HomeTheaterShack.com
Hornresp for Dum... hmm... Everyone 😉 - Home Theater Forum and Systems - HomeTheaterShack.com
GM - that classic fb=fs Vb=Vas/1.44 reflex does look smooth. At ~208l per speaker 5mm xmax only goes so far. That B52 might make a pretty good kick box too.

because qts is a bit on the warm side (some Eminence 18's had 0.26 qts), its tough to cut cabinet size by much.
Here's ~166 liters vs 208.17 (had typo in picture above), no added resistance, no heating effects
(maybe WinISD is more appropriate for reflex than hornresp - ?)
Here's ~166 liters vs 208.17 (had typo in picture above), no added resistance, no heating effects
(maybe WinISD is more appropriate for reflex than hornresp - ?)

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