Suggestions about Ported SQ enclosure for K's

[evilsaint]

This post will probably give you a headache from reading it through, but I assure you my question, in the end, is actually pretty simple.

All I want to do is make a ported box so that I can gain more low end extension, and a bit more output from my subs. I just want to figure out a way to do it without losing any SQ, or with losing as little SQ as possible.

Just for the record, and even though it's in my sig, I have 2 12" dual4Ohm ED K's (2003 Models, "e" on the cone), which i'm powering with a Cadence Z7000.

I'm going to build the box myself, because I feel adventurous, and i'd like to have the experience for the future. Seeing this, what kind of relatively cheap, readily-available (home depot-type available) materials would you guys reccommend? I was thinking 1" MDF or 3/4" HDF, but would it really be beneficial to get some of that 7 or 11 ply birchwood? And would it be okay to glue the pieces together one at a time, and then screw them together to let the glue dry, as opposed to clamping the pieces? I just want this box to be solid and durable. I also plan on putting silicone on the inside, so air leaks shouldn't be a problem, but any tips are welcome. Also, what types of glue and silicon would you guys recommend?

Secondly, I can't get WinISD to work on my computer for some reason, so can anybody lead me to a formula for calculating port frequency based on enclosure size? Also, TS parameters for the ED subs would be a godsend, and I would PM the owner of ED, but I can't remember his SN.

Lastly, what kind of enclosure size, and port tuning freq. would you all recommend? I'm looking for a relatively flat response with a bit of a boosted low end. I have an adjustable subsonic filter on my amp, so tuning the box low isn't a problem, but I really have no idea how much it affects the output (or if it even does at all) of the subs in the enclosure by tuning it low. I figure that going from 1 cube per sub to 2-2.5 cubes per sub ported is going to make the output higher no matter what the tuning frequency, but any input is appreciated. Yet again, for the record, I was thinking of tuning it to 28 or 29Hz.

I thank all of you in advance for reading through this drawn-out, sleep-deprivation inspired post, and appreciate any tips/advice/thoughts/opinions that you can shed to help me out. Peace, Love, and T!ttie Grease

[mgaidica]

I would say 4 cubes tuned to 29-30 hz. The reason being is that 2 cubes per sub is a mid-size enclosure for those subs, and while u want low end extension of a bigger box, you want the SQ of a small one. I say 29-30 hz because that is lower than some might want to go, but with tuning lower you gain SQ along with a lower end extension.

As for wood, use 3/4 MDF, u can try out other things but the results may not be good. I use liquid nails for sealent and glue and it works just great. I will however use other meterials if the situation permits. I will start with a side of the box and pre-drill holes of course, lay a little liquid nails down and screw together that peice, i use 1 (1 1/4"- 1 3/4") screw about every 4-5 inches, to make sure to clamp the wood together really tight.

http://www.loudspeakers101.com/VentCal1.htm

That will help a great deal on port calculations. Also, the older model eD K's full spec sheet can be found in the writing tutorial section on eD's website (www.edesignaudio.com).

Let us/me know if ya got any more questions.

[evilsaint]

I've been messing around with WinISD for a while, now that it started working randomly, and the 2 cubes per sub, 29Hz figure seems just right from how the graphs look. The vent calculation is going retarded though in WinISD, so i'm going to try out a few others.

When people talk about MDF being $15-20 for a sheet, how big is a sheet? I would figure (and hope) that one is big enough for the whole box, but I could be wrong. Also, I know that the ppl at HomeDepot/Hardware Store/etc... are generally kind enough to cut the MDF for you, but do you think that they would be nice enough and/or skilled enough to cut the speaker holes for you?

Lastly, if I were to make 2 separate 2 cube boxes, would it still be viable to put the slot ports on the front of the boxes, because i've heard that you shouldn't put them near the cone if possible.

Thanks for all the help.

[andy00018]

Originally posted by evilsaint
I've been messing around with WinISD for a while, now that it started working randomly, and the 2 cubes per sub, 29Hz figure seems just right from how the graphs look. The vent calculation is going retarded though in WinISD, so i'm going to try out a few others.

When people talk about MDF being $15-20 for a sheet, how big is a sheet? I would figure (and hope) that one is big enough for the whole box, but I could be wrong. Also, I know that the ppl at HomeDepot/Hardware Store/etc... are generally kind enough to cut the MDF for you, but do you think that they would be nice enough and/or skilled enough to cut the speaker holes for you?

Lastly, if I were to make 2 separate 2 cube boxes, would it still be viable to put the slot ports on the front of the boxes, because i've heard that you shouldn't put them near the cone if possible.

Thanks for all the help.

Well a sheet being 8X4 should run you no more then $20, also if your going ported use 1 box if you can, common chambered.

[evilsaint]

Is there any big advantage going with a common chambered box, aside from the fact that it makes the ports easier to make on the box? It's probably due to my lack of sleep, but I really cannot figure out what a good size for these boxes would be that would allow the ports needed to tune them correctly. If anybody feels like giving it a spin, I have most of the specs needed. Single 12", tuned to 29Hz, and i'd prefer that the box is no higher than 18.5 inches, and no deeper (front to back) than 15.25 inches. This isn't a requirement; it would just mean that the new boxes would fit in my current sub box "rack". Any other ideal box designs are welcome.

And in WinISD, what figure are you supposed to put in for Pe? I figure that it has to do with power, because of the watts unit after it, but I don't have a clue what kind of power.

[evilsaint]

Ok, I came up with a few more calculations that seem right, but applying those to a few more, it still seems like i'm screwing something up, because whenever I do port dimensions for a slot port, say 15In (most of the height of the box) x 2In, I get insane port lengths of like 40in.

Is there a specific formula that you have to use for slot ports or something? I would think that the ones made for rectangular port should work just fine. Mgaidica, is there any chance that you could come up with a port design for a 18Hx15Lx13.3W single 12" box tuned to 29Hz, since i'm too retarded to do it? I'd prefer a slot port with no bends to avoid complications in the actual building of the box (i'm a first timer after all), and to avoid port noise at all costs. Whether you can do it for me or not, thanks for all the help.

[Randy Savage]

The lower the tuning, the longer the port will be, assuming you keep the same port area...

If you cut down the port area, the port will be much shorter- but you might run into some port noise

Personally, I'd try and go with about 30 in^2 of port...

With those dimensions, you are looking at ~1.5 ft^3 before driver and port displacement, which will probably end up around 1.0-1.2...I would try and get some more room...

With that low of a tuning, however, and wanting a slot port, you are most likely going to have to bend the port somewhere in the box...

If you decide to use one of the sides of the enclosure as a port, you have to factor in end correction (add 2x the width of the port to the total length), which will actually help you out a bit, since it will slightly cut down on the volume that the port takes from the box...

[evilsaint]

Originally posted by snova031
Personally, I'd try and go with about 30 in^2 of port...

With those dimensions, you are looking at ~1.5 ft^3 before driver and port displacement, which will probably end up around 1.0-1.2...I would try and get some more room...

Maybe my calculations are off again, but 30Inches square times 1.75 to find the displacement of the port is 52.5 cubic inches. 1728cubic inches (cubic foot right?) / 52.5 is only .03 cubic feet of displacement for the port, plus .08 cubic feet from the sub, makes only .11 cubic feet. 18*15*13.3 = 2.08 cubic feet - .11cubes = 1.97 cubes total. Do you need to count the area inside the port, and not actually inside the box? That could be screwing up my calculations.

[evilsaint]

One other thing, if you use multiple, smaller square ports to increase the port area, instead of only one, does it decrease the risk of having port noise?

[Randy Savage]

18x15x13.3 after wood displacement works out to about 1.5 ft^3...

You have a 30 in^2 port, that would be VERY long...

You're gonna need to cut down on port area to get something that is within reason...

Or, squeeze out some more box volume...

Example- you get a box that is 2 ft^3 after all displacements, you are looking at a ~28 in. long port with 30 in^2 port area...

You keep the 1.5 volume, and keep low tuning with a decent amount of port area, port will be 40+ in. long...

Any port with a decent amount of port area in that size of an enclosure wil have probably at least .5 ft^3 displacement...

Basically, you need to squeeze out more room for a reasonable port length...

[evilsaint]

THATS WHAT I WAS FORGETTING!!!! Thank you so much SNova
All along, I don't think that i've put a single thought towards taking the actual MDF thickness out of the displacement. I'm such an idiot

Anyways, adding displacement isn't a problem (extra output is never bad), but would I be better off just putting 2 square ports, one in each corner on one side of the box? It would reduce the port area, and reduce those ungodly lengths, right? With the sizes that these ports are shaping up to be, I don't care about port noise that much.

[Randy Savage]

Whatever you do, you're still gonna end up with a long port or long ports...

With that small of a box and that low of a tuning, you'll run into long ports, unless you have ungodly small amount of port area...

Let's say you went with 10 in^2 port area, you're now looking at a port that is about 18 in. long...but, you will most likely run into port noise here...

[evilsaint]

Ok, sorry to keep buggin' ya, but I have two more questions. First, what's the smallest amount of port area that I can have while most likely avoiding port noise? And second, would the length of slot port on a larger common-chamber box for both subs be shorter if I had the same port area? This is just as much of a possibility for me to do, and it'd certainly be easier to make than two separate boxes with all sorts of fvcked up port designs. Again, thanks for all the help.