Question on isobaric box for 2 Infinity 860w's, want tuned around 37-40hz

[ahardy17 10+ year member]

Alright so after my Alpine PDX ate this little shallow 8" Earthquake I was running, I'm replacing that with 2 Infinity Reference 860w's, 250 watts rms. They're nice little subs for short money and had some of the best reviews for their size, also they're 250 watts apiece is a perfact match for the bass channel of the PDX. So I've been messing around with BBP6 trying to find a design that will fit between the modified seats of my Ranger. It has 60/40 bench seats which I removed the middle of, leaving a cool 9 inches of room. Also here's the standard info as suggested:

Vehicle : 95 regular cab Ranger (5 speed)

Location in the vehicle: between seats against back wall

Space available (Length x Width x Height): 9 inches wide tops, about a foot tall in the back, and about a foot deep

Subwoofer make and model: Infinity Reference 860w

Subwoofer Size: 8"

Number of Subwoofers: 2

Type of Port (Kerfed, Slot, Aero, etc.): Trying to figure that out, BBP was saying like a 1" round port for isobaric at 40hz //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

What type of music do you like?: hip hop, anything crisp

Is your goal SPL or Everyday Music?: SQ really, although it is in nice position for dash blasting

Tuning Freq (Hz): 37-40 hz, whatever I can make this isobaric box do, if I can even port it

Volume : .3-.4 cubes for isobaric. would have to be 1.2 for standard or .7 sealed

Questions: Is it reasonable to try porting such a small iso box, and why as a result is the port so tiny? has anyone ever seen a port that small outside of like boomboxes and computer speakers? Or should I go sealed. I'm liking the iso configuration because although I have enough room for both, it's in an awkward shape, being the L-shaped area freed up by removing a port of the seat. Another thing is the bottom sub would be in danger of getting whacked every time someone buckles up or anything, and doing the face-to-face wouldn't leave any cones exposed. I've never done face-to-face subs before so I'm also unsure of how that would compare to a standard config. Any comments welcome

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[bbeljefe]

For sure it's a no on the one inch port, I don't care who said it. I would go with a three inch port with that much motor force and xmax, lest you're gonna wind up with a lot of port noise.

Another problem you're gonna have with a .3 cube box is that the port will be far too long. The box should be about 1 cube but tuned at 37 Hz it's gonna be stupid peaky at tuning and it's gonna fall flat on it's arse way above the mid 20s.

I'd tune it to something like 33-4 to keep the peak down and make it extend into the 20s.

 

[ahardy17 10+ year member]

For sure it's a no on the one inch port, I don't care who said it. I would go with a three inch port with that much motor force and xmax, lest you're gonna wind up with a lot of port noise.
Another problem you're gonna have with a .3 cube box is that the port will be far too long. The box should be about 1 cube but tuned at 37 Hz it's gonna be stupid peaky at tuning and it's gonna fall flat on it's arse way above the mid 20s.

I'd tune it to something like 33-4 to keep the peak down and make it extend into the 20s.

You aren't lyin about the port length, one of the times I changed the port size or Fb it said something like 109 inches haha. So are you saying it should be 1 cube if I do the face-to-face iso, or standard mounting? Some of the designs I was looking at were awfully peaky. I'll try playing around with those numbers in the meantime, thanks

 

[bbeljefe]

You aren't lyin about the port length, one of the times I changed the port size or Fb it said something like 109 inches haha. So are you saying it should be 1 cube if I do the face-to-face iso, or standard mounting? Some of the designs I was looking at were awfully peaky. I'll try playing around with those numbers in the meantime, thanks

I would do it at one cube even though it's an iso alignment. That will allow you to have a shorter port length and it will ensure that those little beasts can reach down into the bowels of bassdome.

I went ahead and loaded that driver into WinISD Beta (because I like unusual alignments) and here's what it reported:

The green graph is WinISDs model, which is .387 cubes tuned to 26.47. But with a 3" vent, you're talking about ~66", lol.

The yellow white and fuchsia are 1 cube each tuned at 30, 34 & 37 respectively. As you can see, the 37Hz box looks like a burp box. The 34Hz box is almost as peaky and the 30Hz is too but, it's also -3dB at ~25Hz, which is the same -3dB point that WinISD came up with so basically, that's about as low a reach as you're gonna get with those drivers. Group delay for all of the one cube models is ~40ms but WinISD's model isn't a whole lot lower, at around 30.

 

[ahardy17 10+ year member]

Interesting, so that cube at 30hz is looking like a solid route to go. It is a tad peaky but definitely better than not being able to port it. Thanks for taking the time to run that through for me, now I have a direction to head in with this design. Bassboxpro was showing a similar group delay spike, hopefully that won't sound too sloppy. Thanks for your help sir. //content.invisioncic.com/y282845/emoticons/respekt.gif.b162d148236010609fe523122efe3729.gif

 

[bbeljefe]

My pleasure. And look... you could get rid of that peak by making the box .387 cubes tuned to 26 Hz.

How do you think your car would look with a ten foot long port sticking out the window? Or maybe you could do the port in all 90° fittings and make it look like a big curly fry standing on the back seat.