soundqubed hds212s 4th order questions

[Rich Kovacs]

So I would like to try building a 4th order. I have 2 extra hds212s. I was wondering if a 1-2 ratio at 3 sealed 6 ported would work? I can get max dimensions later tonight. Anyone have a 4th order setup that could school me a bit?

[Rich Kovacs]

Here are specs on the sub

Piston Diameter 254.0 mm

Mounting Depth

6.5"

Circle Cutout

11.1875"

Outer Diameter

12 7/8 with gasket

Xmax

26.5mm Peak to Peak

Magnet Weight

100oz

f(s) 39.03 Hz

Q(ms) 5.367

Q(es) 0.587

Q(ts) 0.529

V(as) 29.700 liters

(1.409 cubic feet)

[Triticum Agricolam]

So I would like to try building a 4th order. I have 2 extra hds212s. I was wondering if a 1-2 ratio at 3 sealed 6 ported would work? I can get max dimensions later tonight. Anyone have a 4th order setup that could school me a bit?

Depends on what you mean by "would work". I'm sure it would make sound, and I'm sure it would successfully take up twice as much space as a ported box for those subs would.

What are your goals for this system? What is your motivation for building a 4th order bandpass box? Bandpass boxes let you trade bandwidth for efficiency, so while a bandpass box may allow you to get louder, it is going to be over a very limited frequency range, this is great is you are looking to make a 50 hz burp, not so great if you want to listen to music. You could design the bandpass box to have a large frequency range like a ported box does, but by that point you have given up so much efficiency the ported box would be louder anyway, not to mention much smaller and easier to build.

Also the concept of 2:1 or 3:1 or whatever ratio bandpass boxes makes even less sense than the "port area per cube" rule. There are no cookie cutter short-cut design rules to bandpass boxes, at least not if you want it to sound decent.

If you are wanting to build a bandpass box just to experiment, I totally get that and would encourage you to do so. Just know what the limitations of the system are going to be. Also you should know that the subs you have aren't going to be the best in a 4th order bandpass. They are geared more towards ported use.

[Rich Kovacs]

Thanks for the info. I have never built one and have wanted to try it out.. have been real happy with them in a ported enclosure, more so just playing around

[jessdabest77]

Hate to thread,but I have also been curious on bandpass boxes. So,then what sub's would work best in bandpass boxes?

[Triticum Agricolam]

Depends on what style of bandpass box you are looking to build. For a 4th order bandpass box (BP4) you want sub that would do well in a sealed box. So something with a low EPB, higher QTS, lower Fs, higher xmax, etc. For a 6th order bandpass box (BP6) a sub that is better suited for a ported box will work. Higher EPB, lower QTS, higher Fs, etc.

For example, a sub known to perform decently in a BP4 is a Stereo Integrity HT 18". I know of several people using them like this. It has and EPB of 41, pretty loose suspension (which lowers the Fs), and a decent xmax of 22.5.

Band pass boxes let you shape the output somewhat differently than you can with a ported or sealed box, they also let you push all the sound through a port, which is very beneficial in certain situations. There is also some sound quality advantages to band pass boxes, if used correctly. However, if you are wanting to build a band pass box hoping to get louder with it vs a comparably sized ported box, it is not going to happen.