Is a single 8" aero enough?

[CorNut]

We're going to be building an 8.4 cu ft enclosure as recommended by B2 but I'm wondering about using a single BAP 8" aero.

 

Subs: 2x B2 Rampage 15 XMv4's

Amp: B2 Zero 9 (9kw RMS)

 

SkyHigh lists 43.3 port area for a single 15 in a 4.2 enclosure. The plan is to stick to the recommended volume but I'm wondering if using a single 8" aero (~50 sq in?) will be ok.

 

 

https://skyhighcaraudio.com/copy-of-b2-audio-18-rampage-v4/

 

 

 

[Joe X]

You are joking maybe?

[CorNut]

I wish I was/already knew the answer. You can let me have it if need be, I want to learn/understand it even if I get insulted as long as it leads to the education I seek lol. We already have the subs & amp, we're hoping to build the enclosure within the next few weeks. I've been reading about aeros getting away with near half the port area but different people have different opinions on that. The subs will be inverted (top), we need 48" width, no more than 19" height (lower the better) and we have 32" depth but that's not taking port (rear) clearance into account. It's going in a Sequoia. We're using 3/4" birch, figuring double wall & triple baffle. We're hoping to have the rear firing port in the center on the lower portion of the box. The BAP aero seems to be the easiest way to do that. We're open to other ideas, we're mainly looking at aesthetics/what we thought would look good. I'm guessing the 8" aero is enough but the wood is expensive and would hate to do something we'd regret.

 

 

[Joe X]

Pic straight from the B2's facebook page:

 

 

So I would try to talk to someone who makes sense over there because I got a manual supposedly for those drivers that says do 17.6 square inches per driver, what a mess they have going.

[CorNut]

2 hours ago, Joe X said:

Pic straight from the B2's facebook page:

 

 

So I would try to talk to someone who makes sense over there because I got a manual supposedly for those drivers that says do 17.6 square inches per driver, what a mess they have going.

I don't think they even have that driver on their website. They have a Rampage 15 but comparing the #'s to sky high doesn't add up. The B2 PDF says .49 displacement which matches what the v3 is, not the v4 that he bought.

[Joe X]

Subs should have their manuals with correct parameters inside the box but no way a single 8" port is going to do the job, it will need to be like the pictured box I posted above.

[CorNut]

that's what I was needing to know. Would you know how long each port would need to be for a ~30hz tune in a shared 8.4 cu ft box? I'll figure out the port displacement then make the enclosure that much larger to net 8.4. It's going to be a standard rectangle enclosure so that part will be easy. I'm thinking they'll need to be a little too long but want to make sure first. I think I'll probably have to go with a slot port, which is fine but we were liking the idea of trying the aeros.

 

Also, I figured the specs would be on the site. They were (of course lol) in the box and they do match the ones I assumed were right on Sky High's site. B2 needs to update theirs. 

 

Is what I read wrong about aeros needing nearly half the port area? A single 8" gives 50.2 of the 86.6 the specs call for, which is around 58%. I've read an aero only needs 56% of the area, is that not true? I trust what you say 100% & appreciate your responses. I've never done a dual port design. I'm showing my length as needing to be ~31" w/flare per port if I did 2, which won't give the needed port clearance inside the box. That's how it works right, when adding the additional port, the number I'm getting on the length calculator is per port so I think I'm back to a slot design if that's the case.

 

 

[Joe X]

The parameters are the same as listed in the skyhigh page, minimal set of parameters that let you figure port area but not enough to figure cone excursion or motor strength. With those parameters, 9K, two subs, 8.4 net and a single 8" port that port get airspeeds above 70 m/s, you could get away with 35 m/s with round ports but nothing like 70s. Again talk to someone who is actually running those subs and get some opinions.

[CorNut]

We're doing 2 ports, I was just curious if ~30" ports was what we need.

 

Thank you, you helped and we're definitely doing dual 8" aeros netting ~8.4 based on your responses. I'm guessing somewhere around 30" each but they're the BAP aeros which are easy to adjust so we'll figure it out/get it dialed in.

[Joe X]

For a 30Hz tuning on the above conditions it will be 30" each of two for a port displacement of 1.6 cubic feet total, port airspeed is still 36 m/s @9K pretty insane but you can barely get away with that because it's not just some PVC pipe but proper commercial designs you are going to be using.

 

It's kind of not even funny to see a company issuing ridiculous recommendations only to be showing themselves pictures of correct designs to contradict their statements.