best size cab

[rptrsn2]

have read on here about the 3015 in a tl 606 box. i have a 3015 in a huge old peavey cab and want to build another smaller cab for it. what is the best size box to get the best performance from this speaker. i know when messing with winsd it gives you a optimum default size, is this what i want. anyone who has built cabs with these what are your exp. i've read posts that say anything over 3.5 cubic feet is a waste and belive one pos that said 2.8 is the best. thanks

[DukeLeJeune]

One school of thought would hold that the "best" size is the smallest one that still does what you want.

So... what do you want?

For instance, if you want to reproduce the first overtone of low-B at -3 dB, then 2.8 cubic feet tuned to around 48 - 50 Hz looks pretty good.

[rpsands]

I suggest you experiment with the box you have -- use closed cell foam reducers and an assortment of tube ports, to get the sound you like. It'll be educational and fun.

* Empirical testing combined with modeling is far better than modeling alone, if you have the setup to do it (and you have the perfect setup; those old Peavey cabs are usually huge and have one big tube port, IIRC.

[rptrsn2]

Just want as small as possible cab with keeping good bottom end. I use a 5 on ocassion but mostly just my pbass. Rarly play anything other than standard tuning.

[DukeLeJeune]

"As small as possible with keeping good bottom end" is, imho, ballpark 2.8 cubic feet if that low-B matters, and (again imho) can theoretically be as small as 1.6 cubic feet (tuned to the lower 50's) if low-E is the target. The latter is -2.5 dB at 80 Hz, with a .5 dB bump at 150 Hz, so the spread there is 3 dB. I like to keep the spread within 3 dB so that we don't have some notes significantly louder than others.

[rptrsn2]

im trying to figure out winsid to help me. also found this but dont know if its of any use, its for car sys woofers www.carstereo.com/help2/Articles.cfm

[rptrsn2]

using that site, entering a 2.8 cubic ft box,and 1 round 6" port it calls for 6.5" lenghth for 50hz or 2 4" at 6.75" long. does this sound right?

[DukeLeJeune]

Rptrsn2, those port lengths sound correct to me.

If you don't mind spending a little extra for your ports, let me recommend Precision Ports. They are modular ports, flared on the ends with a straight center section. Two advantages: The flare smooths the airflow in and out of the port which admittedly is only an issue at high SPLs but still a nice feature, and you get a long enough center section that you can cut it and try several different lengths (and therefore several different tuning frequencies). Parts Express and Madisound both sell 'em, and here's the company's website. Use their online calculator, at the "Tools" link, to calculate port lengths for their flared ports:

http://www.psp-inc.com/index.html

I have no affiliation with Precision Ports, aside from satisfied customer.

[rptrsn2]

thanks for the tip i will definitly check them out. i dont mind spending a bit more for the right stuff. i would prolly be better off to buy a cab but i really like this driver and want to build a cab myself for just to do it and try to learn a little more about the process. i always read up on hear and hear alot of terms and principles i don,t understand on designing cabs but trying to catch on. i have plenty of skill and the equipment to build right once i know what i need to build. thanks for the info

[5StringPocket]

That looks like a nice product line. Flared ports seem to be showing up in high end cabs like the Berg AE212 and the new DNA 12's. The 4" even comes in dimpled which makes them even more slippery for smooth laminar flow.

A 4.3 ft3 enclosure loaded with two Eminence 3012LF's tuned to 48 Hz would need four 4" ports if you follow the Eminence enclosure guide. Each 4" flared port needs 7.25" mounting diameter and would be 11.75" long according to the Precision port length calculator. That's a lot of port and cabinet real estate.

Using four 3" flared ports would only require 6.50" length. No mach numbers are provided but would this provide adequate porting for those high excursion woofers to avoid chuffing at high SPL?

[rptrsn2]

Is there any problem rear porting a cab? I've seen cabs with rear ports so I would assume this is fine.

[DukeLeJeune]

5StringPocket, the flared ports reduce the diameter necessary to prevent turbulence, and therefore reduce the length needed to tune to a desired frequency. I use two 3" flared ports for a single 3012LF variant, with the approval of Eminence engineer Jerry McNutt who designed the woofer and who generated those cabinet guidelines you looked at.

Rptrsn2, rear porting works fine because the energy emerging from the port is omni-directional. I generally prefer rear porting, given the choice. With fairly long-excursion drivers like the Kappalite series, I try to arrange the ports symmetrically with respect to the woofer cone, as this makes it less likely that the woofer will develop a rocking mode under high power from an uneven airload on the back of the cone. This is more easily accomplished with rear-mounted ports. Again, credit to Jerry McNutt for the tip about symmetrical air loads.

Edit: I think the uneven airload thing is more likely to be an issue in a fairly small cabinet, relative to the woofer involved. It's not an issue with the fEarful cabinets, which use Kappalite LF series woofers but have generous internal airspace.

[5StringPocket]

The Thunderchild, of course... a stunning application of this porting scheme.

[DukeLeJeune]

One final bit of port trivia: If you use multiple round ports, try to have some physically higher up than others. This can give you a bit of cooling as warm air exits the top port(s) and cool air enters the bottom one(s). The reason I have mine on a diagonal instead of vertically aligned on the Thunderchild is so that everything will fit in the fairly small box (woofer, ports, crossover, bracing). Once again, credit to Jerry McNutt. As it is, I still have to leave a bare space on the crossover board for the inner flare of that lower port.

[KJung]

Originally Posted by DukeLeJeune

One final bit of port trivia: If you use multiple round ports, try to have some physically higher up than others. This can give you a bit of cooling as warm air exits the top port(s) and cool air enters the bottom one(s). The reason I have mine on a diagonal instead of vertically aligned on the Thunderchild is so that everything will fit in the fairly small box (woofer, ports, crossover). Once again, credit to Jerry McNutt. As it is, I still have to leave a bare space on the crossover board for the inner flare of that lower woofer.

Hey Duke,

Maybe this will help the OP. Here is a 'back of the cab' picture of your wonderful Thunderchild that shows the port type and placement.

[rptrsn2]

cool, like to have that little cab and a mbfusion head!

[s_mcsleazy]

may i sugest some kinda 2x12

[rptrsn2]

thanks but no, ive fallen in love with the 3015 and want to stick with it in as small box as possible. it sounds great in my huge old tvx cab and from what i've read i am wasting the potential of this driver in that big of a cab. I,m thinking if it works out for me having 2 of them with a mbfusion head. although for now i,m happy with my 700rbii just like down sizing. i have thought for a next project tho seeing how small a 212 i could build.