Very strange results for RadianAudio 5312 coax

[Kitchenpass]

Hi Folks,

My first post here, so go easy on me.

I am trying to design a monitor cabinet similar to the Microwedge (www.microwedge.com). This is a ported wedge shaped cabinet which is intended to be used by musicians as a vocal monitor. My plan is to power these guys with www.speakerpower.net 2 channel amps using the built in DSP crossover.

I already have the Radian Audio 5312 12" coax driver and am starting to get familiar with Thiele-Small parameters and the various box calculator packages out there, WinISD and http://www.diysubwoofers.org/ amongst others.

The trouble I'm having is some very strange results with all of the utilities I've tried that show near zero response below 200hz, yet I know that can not be right. I have tried different net volumes, port tunings and everything in between, and I still get general weirdness.

The numbers I got from Radian's webpage are as follows:
THIELE/SMALL PARAMETERS:
QTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3653
QMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6136
QES . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 0.4246
VAS. . . . . . . .. . . . .. . . . 1.95 (ft.3), 55.444 (liters)
FS (HZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Hz
XMAX (IN) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.113”
RE ohms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0
SD (IN2) . . . . . . . .. . . . . . . . . . . . . . . . . . . . 82.08
Power handling is 500watts

With a small x-max this is no subwoofer, which is fine I don't need much beneath 80-100hz. But this strange response curve makes me think I've got something wrong or the T-S numbers are way off base.

Can anyone give me an idea of the net volume and port dimensions that would give me a reasonably flat response from 80hz on up?

Thanks
Simon

[Stixx]

Hi Simon,
you happen to live very close to me.....

The numbers you supplied make perfect sense, so I plugged them into the Unibox spreadsheet by Kristian Ougaard.
Looking at the vented box output we have a box volume of 40 l, Fb=58Hz and a nice response curve down to 56Hz (-3dB). Did you take care of putting the metric equivalent of Sd into your programs? I just assumed 440cm2...

Tschuess,
Oliver

[rcw]

This type of box is an ideal candidate for a QB5 class II alignment,
these incidently were derived by two Germans named Kreutz and Panzer.
My quick calculations indicate a Vb=30.5 litres, fb=82 Hz.
if fed from a .62 Q, 93 Hz. filter, this driver should have a f3=80 Hz. and the power handling will be such that it is limited by the voice coil rating, i.e. Smalls "kp" parameter is around 60.The full details of how to design these boxes are to be found at Rod Elliots website, at www.sound.com.au

[Kitchenpass]

Hi Folks,

I finally had some time to play with this design again and figured out that I had entered the Qts wrong. I had 0.036 instead of 0.365. Made a huge difference. (It's always the dumb things that trip you up) Now it is behaving more like I would expect.

After some fiddling around with various alignments and box volumes I have arrived at a modified SC4 alignment, 36.7 liter net volume, with 2 3"x5.44" ports tuned to 62 hz. This gives me flat response with a -3db point at 65hz. Perfect for my needs.

At full power (500 watts) it looks like I'm going to exceed my Xmax at 90hz, but I tend to HighPass at 100hz for this application and will probably never drive them that hard, so that should not be a problem.

I will be ordering a pair of SpeakerPower modules tomorrow and will start to put this design on paper in the next few days.

Thanks for the assistance.
Simon