[southworth]

I just picked up a pair of these from Stereo Integrity an I need some design advice.............

I'd like to build a pair of ported boxes for them using some 1" mdf and 3" Precision ports that I have left over from an earlier build...........

The front baffles will be 1-1/2" and I would like to limit the size to about 5 cu. ft. or so (internal). The plan is for the subs to be front firing. What would be a good recommended tune for these subs given the size of the boxes using the 3" Precision Ports?

My room is 2500 sq. ft. and the subs will be wired for 4 ohms and driven by a Behringer EP2500 amp...........

Thanks in advance....................

 

[fusseli]

How many ports do you have? And 5cuft/ea or for both?

For 5cuft a 20Hz tune would work well. With a reasonable amount of power a 3" port is way too small for a 15" driver. You'd need at least 3 or 4 ports per sub. I'd suggest bigger ports.

 

[southworth]

I have four 3" Precision Ports and I could go up to about 5.5 cu ft internal for each enclosure. These boxes will be located on the left and right sides of the front of the theater.

 

[steve nn]

I'd suggest bigger ports.

Wouldn't it/3" be nice.. just not gonna work though.

 

[southworth]

Will I need to go PR instead of ports?

 

[steve nn]

I'm seeing 1 6" port or 3 3" or 2 4" ports. A slot vent would work as well. PR's are always a great option if you like. You would need to get Mike or someone to sim it for you though. I have no experience simming PR's although I run a dual PR option. I'm looking at things at 5cf after displacement with a hp filter plugged in at 18-19hz though.

 

[fusseli]

Here is the SI 15 with Creative Sound APR15s in 5.5cuft. With a custom HPF to protect the driver (same as for ported subs) and with mass added to the PRs, the -3dB point is about 25Hz and -6dB at 19Hz. You could almost get away with one APR15, but it would be pushed pretty hard with 500W. Two would be fine beyond 1000W, which would take the SI 15 over xmax. Two APR12s might work also, it would need to be modeled separately.

 

[steve nn]

Hey that's awesome Russ.. THANK YOU.

 

[southworth]

I'll probably not go the PR route since I'd have to plunk down another $200 / ea to get it done. A slot port is beginning to look better for the design given the volume restraints. Can someone be kind enough sim up a slot ported 5.5 encloaure for me? Thanks.................

 

[fusseli]

The slot port would take up an additional 0.25cuft, making a 5.5cuft net more like 6.1cuft gross volume after bracing, driver, and port. In this case I agree, little is to be gained from dishing out for the PRs. Using PRs is the best deal for small cabinets tuned very low.

 

[steve nn]

Lets see.. 5.5cf internal after displacement.. Three slots at 2”High, 5”Wide come in at 38”Long. I can see applying a 15% correction value to the length because our tunes generally come in lower than projected. I’m taking for granted you’re going to bend the vent up the back in saying that though. So your total length would come in at 32.25”. I went with three vents not just taking air velocity into account but to give you a good base for your bracing also. If you would rather go two it will come in two vents 2X8 at 32.25

Yeah PR's really come in handy. They do cost though.

 

[southworth]

steve nn,
Am I to understand that you are suggesting that I'm can implement three 2h x 5w x 38l slot ports which would yield a tune of roughly 18.5 Hz in a gross 6.1 cu. ft cabinet (assuming .25 cu. ft. for the driver + bracing displacement and .25 cu. ft. for the port displacements)?

 

[steve nn]

Yes, except 19hz tune not 18.5. I’m also saying because of the way the driver sees the slot vent if you’re running it along the bottom and up the back wall.. The driver doesn't see the vent termination in most cases as the end but extending a little more because of the back wall which is part of your vent. Sort of the same effect as running a 4” round port up to 3” of your back wall. It lowers the tune, breaks the rule. So I also suggested (theoretically) if you wanted to shorten up your slot a few inches you would most likely stay on tune. Here is the air velocity and 1st port res along with vents. As far as what size enclosure it would take before displacement I can’t say because I haven't calculated. If I were you I would use the bottom, sides and back as part of your vent though. If the size vents don’t work out with how wide you want to build, they can be adjusted to a degree. EDIT> Since it’s three vents, you need to factor in 3/4 X 2 (1.5”) presuming 3/4 ply or MDF for your vent separation just in case you didn't factor. A 20hz tune shortens up your vents 4" more.

Slot example

Marty Super Cube

 

[RollerDJ]

Just curious, what mapping program are you using there? It looks nothing like the WinISD I use. Also, on the subject of this sub. If I do a single one of these in a 4.64 ft^3 box, would you use one or two 4" aero ports?

 

[fusseli]

Just curious, what mapping program are you using there? It looks nothing like the WinISD I use. Also, on the subject of this sub. If I do a single one of these in a 4.64 ft^3 box, would you use one or two 4" aero ports?

That's the newest WinIsd. For a 15 in that big of a box with more than a couple hundred watts a single 4" port will not be enough.

 

[RollerDJ]

Well poo. Got any suggestions then? I have 2 4" aero ports sitting around right now.