merzbow

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Does this look good?

Alright I'm tired of fighting my car and am getting an SUV. Will be getting two more BTLs 15s (I accidentally ordered two more 12s today, lol, hopefully I can get that fixed on Monday over email). If anyone in the CA Bay Area wants the half-built box pictured above for free (plus two MDF sheets for the top, that I haven't cut circles in yet), let me know...

2 BTL 15s (per the thread title . The port is wide enough I can put a V brace in the back after it's built, so that's something I can experiment with later if I need to.

Oh happy day my subs are shipped. This is going to be a SILLY weekend...

Decided to split the difference, a little bit, and went with 10.75" on each of the "side Ts". By any account this should be pretty close to 32hz, with proper net volume to each sub: I can't put the top on this beeatch until the subs arrive, which is taking Fi a lot longer than they said they would originally. Anyways I can do electrical work in the car in the meantime, and also it's 45 pucking degrees in California in late May so I can't fiberglass the interior edges of the box yet until it warms up. I'm still debating whether a V brace is necessary at the back of the port. My inclination is "no" at the moment, unless someone tells me they didn't do it and it sounded like ass.

I think you're mixing up "flare" with "flange". WinISD help file defines a "flanged end" as a port that terminates in a baffle, their diagram makes that clear. So I'd put the outer opening of this port in that category. As for the inner port opening, yes, that requires adding end correction also. WinISD's "flanged end" correction factor is to add 0.4 times effective diameter, which also corresponds closely to what we need for the inner port correction. So hence why I set it to "two flanged ends".

Audibel, that also looks like a logical way to analyze the air flow, assuming the air streams are taking the "nearest" route outwards (which I could encourage with a center divider). So ignoring the Torres calculator for a moment, WinISD (set to 7.3cf at 32hz with this port area) wants a vent length of 32..46" if I set "two flanged ends" as the correction, which means 32.46" - 29.89" = 2.57" extra on each side of the "T". You appear to be setting WinISD as "one flanged end", which produces 33.91", and 33.91 - 22.89" = 4.02", which is where you must be getting the 4 inches from. I think the "two flanged ends" is more accurate for a slot port, so right now I'm leaning towards adding the 2.5".

Do your own research and choose. All you're going to hear is speculation since nobody has actually measured one of these (although I will at some point). Don't listen to people who slag off on a company with no evidence to back up their statements.

http://www.qualitypowerauto.com/

31 inches actually, you have to measure from the middle as it bends. From what I understand, you can consider a T port to be the same as an L port by "stacking" the two upper halves of the T on top of each other. So if we do that here, then measure down the middle, we get 0.75 + 16.75 + 2.75 + 2.75 + 8 = 31. Its 0.75+16.75+2.75+0.75+8=29" physical length since there isn't a triangular divider at the end of the wall in the port splitting the original port. Effective length is 29+(2.75/2)= 30.375". To me, its basically two ports. I have never built a "shared" center port so take it however you like. The (2.75/2) you mention above is end correction, right? Hmm. (The Torres calculator actually doesn't appear to take end correction into account, seems like a bug). So I guess I'm not really that far off. I'll be happy with anything reasonably close to 32hz to be honest, what I'm trying to avoid is screwing it up REALLY badly. I suppose a triangle divider might help reduce turbulence by redirecting the air towards the mouth before it merges.

Anyone at all have experience building these types of boxes (dual subs, shared center port)? I'm going to start putting it together this weekend so time is running out... as for bracing, I think the port walls will be enough, except I will also fiberglass the interior edges for added strength.

31 inches actually, you have to measure from the middle as it bends. From what I understand, you can consider a T port to be the same as an L port by "stacking" the two upper halves of the T on top of each other. So if we do that here, then measure down the middle, we get 0.75 + 16.75 + 2.75 + 2.75 + 8 = 31. And before anyone asks this post is where I got this technique from: http://www.caraudio.com/forums/enclosure-design-construction-help/272321-port-tuning-question-3.html#post3656749 I don't know enough about the theory to verify if this is actually correct, but the poster seems reliable.

31 inches actually, you have to measure from the middle as it bends. From what I understand, you can consider a T port to be the same as an L port by "stacking" the two upper halves of the T on top of each other. So if we do that here, then measure down the middle, we get 0.75 + 16.75 + 2.75 + 2.75 + 8 = 31.

I can see them fine from multiple computers... but I will put them on a different site, perhaps that will work better: <original second post repeated now...> Changed my mind, I want to do a middle T-shaped port now. Here are the new specs and diagrams. 3.65cf net per driver, which is within Fi's range of 3-5. Port area is 16.41 in^2 per cf, above the 12-16 recommended by Fi because there are TWO drivers sharing the same port. Modeling with WinISD puts port velocity within the range of the 23-30 m/s I'm seeing with Fi's recommended enclosures, so I think port area OK. Also, I'm going to be using a Sundown SAZ-3500D, so I'll be running with 3500 watts at least, not 3200 as in the thread title. Opinions please before I potentially waste a LOT of money on materials? I cannot change the outer dimensions, that is the max I can possibly go, the only thing I can adjust now is the port.

Changed my mind, I want to do a middle T-shaped port now. Here are the new specs and diagrams. 3.65cf net per driver, which is within Fi's range of 3-5. Port area is 16.41 in^2 per cf, above the 12-16 recommended by Fi because there are TWO drivers sharing the same port. Modeling with WinISD puts port velocity within the range of the 23-30 m/s I'm seeing with Fi's recommended enclosures, so I think port area OK. Also, I'm going to be using a Sundown SAZ-3500D, so I'll be running with 3500 watts at least, not 3200 as in the thread title. Opinions please before I potentially waste a LOT of money on materials? I cannot change the outer dimensions, that is the max I can possibly go, the only thing I can adjust now is the port.

Sup. I have a pretty good system in my BMW, and frequented some other forums about five years ago. I'm getting the itch to rebuild again, and wondered what happened to the industry, and sort of concluded that car audio was dying. Well it looks like everyone came here. Cool forum!