Folded Horn W-Bin Porting

[gjeff80]

Hi everyone, I was just wondering if anyone has any tips on porting a Folded Horn W-Bin cabinet. I've got 8 of these cabinets, 4 18 inch versions, and 4 15 inch versions, I've installed some ports in them based on port length recommendations from the software I used (winISD), it had all the T/S specs for the speakers pre loaded. I just wanted to make sure the same porting rules apply that you would use for a standard box. I just didn't know if having the port on the opposite side of the chamber as the baffle makes a difference in how to tune it or not.

Thanks
Glenn

[OMNIFEX]

Hey gjeff80 !!!!



It's very easy to port a W Bin Enclosure. I did it myself with
the panel you would remove to insert the woofer.

What you need to do is scale the cabinet the woofer sits
in.

I'm currently using Bass Box Pro, and, Eminence Designer,
which offers a Pyramid, Truncated design. So........ I took
all the measurements, punched them in, and...............

[OMNIFEX]

[gjeff80]

hmm... you guys have me thinking now... I shouldn't need special software that does pyramid boxes if I know the volume of the chamber right? I believe I found that correctly, I figured that out manually, all I did was take a measurement of the inside height, (h), the inside length of the two chamber walls (l), and then I took a measurement of the inside length of the front baffle (w1), and the small piece near the rear (w2), I averaged the two front and rear pieces ((w1+w2)/2) = (w) and that gave me my width, so then I just calculated box volume like a straight box, (l) x (w) x(h) / 1728.

My concerned was if you follow the same porting guidlines because the port is located on the rear of the driver. I just didn't know if it caused any problems because some of the sound is coming out of the front of the driver, and some is coming out of the port which isn't traveling out of the w-horn.

Thanks
Glenn

[Centauri]

The aim of porting a horn is to extend the low end, therefore if your horn's lower cutoff was say 50Hz (some compact W's are even higher than this), then try port tuning at 35-40Hz. Also be aware that horn loading a driver lowers the driver's Fs - estimate around 10% lower. The horn output at the port frequency usually drops off quite rapidly, so time arrival problems would be minimal - just don't try tuning the port too high. You may find that the required port length (taking into consideration port air speed) could be way too long to physically fit.

Cheers

[sreten]

I just didn't know if having the port on the opposite side of the chamber as the baffle makes a difference in how to tune it or not.

It makes no difference tuning wise.

The only concern with having the ports at the rear would
be designing cabinets for stacking, say four or more.

Rear porting in this case is not a good idea, a shelf port
to the front of the cabinet, top or bottom, should be used.

sreten.

[gjeff80]

Thanks, I've been tuning all the W-Bin pors to 40Hz, and went with the length ports winISD recommended I use. I'm running JBL 2226H speakers in the 15 inch w-bins, they used to be sealed, but the internal volume of the chamber is only 2.6~2.7 cubic feet, so I felt they were being restricted by being in such a small enclosure, so I installed 4 2 inch ports with a length of 6.5 in each box, which was what winISD said would tune the port to 40Hz.

Then one set of the 18 inch w-bin sets is loaded with a JBL 2240H woofer, the internal volume of this chamber is about 7.65 cubic feet, again I tuned this cabinets port to 40Hz.

Then the last set of 18 inch w-bin's I haven't ported yet since I just finished one of them. It's JBL's 4518 cabinet, I'm going to try an extra set of Cervin Vega 189E woofers I have sitting around, but I'm waiting to see if I can find the T/S specs, or measure them so I can plug the parameters into a box building software.

Does 40Hz sound about right for tuning the port too, according to the graph on WinISD it seemed to provide the best looking graph for the woofers. Also, how accurate is the graph that WinISD generates, I know it is based on a regular front loaded box, but how much will a W-Bin Horn affect the graph, will it still have the same curve just with increased dBs?

Thanks again guys!!

[OMNIFEX]

W Bins is a straight horn folded to take up less space.

You cannot just tune the box to a desired frequency until,
you know how the speaker will respond tuned to that
desired frequency in the enclosure.

Horn woofers TS Parameters are totaly different from
Bass Reflex woofers, and, you can't tune a Woofer
using bass reflex equations to work with a horn woofer.

[gjeff80]

Omniflex,

Do you know how I would go about tuning the port of a folded horn if i know the T/S specs for the woofer? I thought of leaving the cabinets sealed, but the majority of the W-Bin boxes I found online all had some type of port installed in in the front piece. I guess tuning them is a lot more complicated than I thought.

Thanks again for all your help on my posts!

Glenn

[OMNIFEX]

Yes I know how to it.

I explained it to you on my first reply.

Dude, I own four W Bins, all housed with Cerwin Vega
Eighteens.

They are tuned to 52.37 Hz, and, have a f3 @ 50 Hz (RED)

If I kept them sealed, the f3 would be 141 Hz. (YELLOW)

I cut them off at 50 Hz, and are tuned on 100 Hz. With
the help of a Electronic Crossover of course!