I know pretty well sealed enclosures since I am more of an SQ guy. Unfortunately I don't know ported that well. I was trying to help a guy out with a box, and thought I would get your help on this as well. Here's the link to the thread. He's wanting the most SPL possible out of his two RF 1812 subwoofers. I'm hoping that they are the same as the 2812's listed in WinISD. I noticed that as the enclosure size goes up, I can really get a large peak at a certain frequency. This includes more than a 6 dB peak at 45 cubic feet. What I was wondering is at what point does the enclosure get too big? Also the port size was a little odd. At 10 cubes with both subs and tuned to 45 Hz, two 4" ports would only be .42 inches long. I had to step it up to 5.5" diameter ports to get a half way decent length out of them. What do you guys recomend for this, and why?
Oh wow, lol.. I just posted on that thread! B) Small world... Anyway, your observations are reasonable. The larger you make an enclosure, the shorter a given port diameter port needs to be to maintain a particular target tuning frequency. And likewise, the smaller you make an enclosure, the longer that port needs to become, to maintain that same target tuning frequency. That's why, in tiny boxes, the less-efficient passive radiators become desireable... they don't have any length to them, and effectively they behave like ports. "What point does the enclosure get too big" has two answers, depending on how you look at it... From a frequency response standpoint, have at it! Huge, no harm. Big, giant, all good. But from a mechanical powerhandling standpoint... you are reaching another limit.. excursion capability. The larger you make the enclosure, the less power is required by the subwoofer to reach given excursion levels. You need to be aware of this, so you don't try to send 300 watts through a 300w RMS subwoofer in a huge enclosure, because you might bottom it out before you reach 100w. Enclosure can be a great substitute for power that way, even. Your subwoofer's efficiency is MUCH more controlled by the enclosure that you have it in, than it is by the driver itself. B) You should have him join up over here, so we can answer his posts directly! :ss:
The forum is finally up and working, so my link above will now work. BTW Geo, I think you may be talking about a different forum/thread? But thanks for the info. I just figured that at some point the internal air space would be so large, it wouldn't act like it was in an enclosure anymore and enclosure size gains would not result in performance gains (from an SPL standpoint). So if you put a Brahma in a room size ported enclosure and took it too Xmax, would the output still be up there with a 4 cubic foot ported enclosure?
Oh, yep.. I had a thread open at the12volt, and when I clicked your link, it just popped open that window apparently... must have been when your link wasn't working. Oh well.
