4th Order for Dayton HO

[Triticum Agricolam]

Well there are a couple things you could do. Assuming you are only running 800 watts, you could probably get away with just two 4" ports, which would only need to be about 15" long. If you flared them really well, they would probably be fine, they just wouldn't be ideal.

Another thing would be to use three 4" ports, which would have to be about 25" long. 4" PVC is cheap and the fittings aren't too bad, I think last time I looked elbows were like $8-$10 a piece.

Or you could step up to a single 6" port. It would be less port area than two 5" ports, but would be better than two 4" ports and would only have to be 16" long. Flared well you should be fine.

If it were me, I'd do either three 4" ports, or one 6".

[bassman619]

Cool

[gckless]

Well there are a couple things you could do. Assuming you are only running 800 watts, you could probably get away with just two 4" ports, which would only need to be about 15" long. If you flared them really well, they would probably be fine, they just wouldn't be ideal.

Another thing would be to use three 4" ports, which would have to be about 25" long. 4" PVC is cheap and the fittings aren't too bad, I think last time I looked elbows were like $8-$10 a piece.

Or you could step up to a single 6" port. It would be less port area than two 5" ports, but would be better than two 4" ports and would only have to be 16" long. Flared well you should be fine.

If it were me, I'd do either three 4" ports, or one 6".

So full disclosure: Here's what I'm working with:

I'm trying to fire the ports through those holes in the rear deck. Middle one fits a 6" max, the outer two fit 5" max. Box will be 18" high (outer), and I have 23.25" from the where the opening will be on top to the bottom of the box. The driver will be vertical firing backwards, with the sealed section towards the front of the car.

So I could do a single center 6", makes it about 15.5" long by my quick calcs, but I'm kinda worried about driver unloading since the port will be directly in front of it. Anything I could do to get rid of that? Also trying to do more than 6" of port area, you really think that's going to be enough?

Doing 3 4" ports, I'd be worried about unloading to or favoring the center port. Also, I'd have to turn them if they were 24", so the center port wouldn't work. And I'm pretty nervous about doing two 4" ports, doesn't seem like enough. Beats spending $150 for a pair of 5" ports though I think.

Edit: I didn't want to cut the outer two holes. Would make sealing it up much simpler and cleaner. But cutting them to fit 6" ports each I think is my best route. Beats spending $150 for 5" ports or going with a pair of 4".

[Triticum Agricolam]

I can see why that's kinda a tough space to work with. Your situation, like many others I've seen in car audio, makes it very difficult to come up with a solution that is optimal in every way. Somewhere design compromises must be made.

With bandpass boxes I like to keep port velocities under 20 m/sec. Two 5" ports will do that, no problem. A single 6" port gets up to around 23 m/sec, while that's higher than I'd like to see, its not really into the danger zone yet either. Larger diameter ports handle higher port velocities better than smaller diameter ports anyway. Three 4" ports is just slightly less port area than two 5"s so its port area is about the same as the 5" ports.

I sure wouldn't spend $150 just to run 5" ports, that's a lot of money for some ports. If I HAD to use 5" ports I'd buy a box of 5" mailing tubes for $60 and cut them up to make my own bends.

I wouldn't worry about the sub unloading with the port in front of it. As long as you can't see the sub cone through the port I don't think you have much to worry about.

[ToNasty]

Sonic electronix does sell a 5" flared aero last time I looked. I think they were $25

[gckless]

I can see why that's kinda a tough space to work with. Your situation, like many others I've seen in car audio, makes it very difficult to come up with a solution that is optimal in every way. Somewhere design compromises must be made.

With bandpass boxes I like to keep port velocities under 20 m/sec. Two 5" ports will do that, no problem. A single 6" port gets up to around 23 m/sec, while that's higher than I'd like to see, its not really into the danger zone yet either. Larger diameter ports handle higher port velocities better than smaller diameter ports anyway. Three 4" ports is just slightly less port area than two 5"s so its port area is about the same as the 5" ports.

I sure wouldn't spend $150 just to run 5" ports, that's a lot of money for some ports. If I HAD to use 5" ports I'd buy a box of 5" mailing tubes for $60 and cut them up to make my own bends.

I wouldn't worry about the sub unloading with the port in front of it. As long as you can't see the sub cone through the port I don't think you have much to worry about.

You think I could raise internal volume and tuning a tad? I think if I go to 1.7 net and 52Hz, I could get a port length of 19.25, which is doable without bending the 5" ports. I see that it does start to get peaky real quick, but with some EQ work think I could get it close to flat? Could bring up sealed chamber volume too if I needed to.

I think I'm just trying not to cut the rear deck cover. If I do an odd number of ports I will need to do that to get it in the center.

Thanks for the help man.

Sonic electronix does sell a 5" flared aero last time I looked. I think they were $25

If they do have one, I couldn't find it.

[Triticum Agricolam]

Yeah you can increase the front chamber to 1.7 cubes and raise to the tuning to 52 hz. It won't make that much difference, especially if you are going to use some EQ.

[gckless]

Ok cool. Or maybe I should just tune it above my LPF. Would eliminate the need for EQ essentially, but would also eliminate any gains I got from the enclosure. Would basically be a sealed box directed into the cabin.

Dunno, have to see what that looks like in WinISD. Just thinking out loud here.

[Triticum Agricolam]

Ok cool. Or maybe I should just tune it above my LPF. Would eliminate the need for EQ essentially, but would also eliminate any gains I got from the enclosure. Would basically be a sealed box directed into the cabin.

Dunno, have to see what that looks like in WinISD. Just thinking out loud here.

Yeah you could do that too.

[gckless]

Well looks like that isn't going to work, peak is too large too high.

Looks like 1.7 net at 52Hz or 1.6 net at 54Hz is where I'll be landing. Not sure I'll notice a difference there, and to be honest not sure I'll even get it that precise after bracing. I'll probably be between the two.