I've received a few inquiries on the full range boathull speakers so here's an update.
My default starting point for this project was to use Audio Nirvana's 10 inch Classic full range driver a their plain vanilla 2.8 cubic feet (~79 liter) cabinet with a 6 inch port and no port tube, just the ~0.75 wall thickness of the front baffle. It was never my intent to actually use this as the final cabinet, only to use it to guide to next steps. The final cabinet design will be a stacked "boat hull" shape using layers of milled baltic birch. Thus the entire cabinet except for the tops and bottoms will be sanded and clear finished baltic birch edge grain. The walls will be ~1.5 inch thick laminate with periodic cross bracing. Stiff, stiffer, stiffest. You won't be hearing this cabinet, just the driver.
I've run several cabinet design calcs which more or less conclude that the ideal cabinet for this driver would be ~ 12 cubic feet with an F3 well under 30 Hz. A monster size box that is too big to be practical for what I'm looking for. Hence the 2.8 cubic feet box which when you see it standing there in front of you still looks plenty big. 40" tall by 12" wide by 13.5" deep.
With a 6 inch port the design calcs call for a port tube length in the 8-12" range. I currently have no port tube other than the 0.73" baffle itself. I've experimented with an 8" quick and dirty port tube made of stiff thick walled paper rolled into a tube reinforced with duct tape. Ugly as sin but fairly solid. Did some with and without listening and my conclusion was the port tube was not noticeably effective. Quite possibly a proper tube would lead to a different conclusion. By my hunch is that while a longer tube may provide incremental benefit it would be rather modest at best and adds additional sonic complexities.
After further playing around with the miniDSP together the Room Eq Wizard ("REW") software (
http://www.roomeqwizard.com/) and a real time analyzer (RTA), I've arrived at the following adjustments and thoughts.
1) The 10" Audio Nirvana Classic benefits greatly from the application of a high shelf PEQ starting at 400 Hz with -6 dB reduction in gain. Some might call this a form of baffle step compensation.
2) Whether it's the driver, the room, or combination of both, there was a noticeable boominess in the mid-bass. After running REW and loading the adjustment filters into the DSP, the boominess was completely gone. The filter was a fairly complex peak followed by big notch. Huge plus and a snap to implement with REW and the miniDSP.
3) Overall bass satisfaction benefits from adding a low shelf PEQ boost from 100 Hz down with a +2 to +3 dB gain. Adjust to suit. Cranking it up further really pours on the bass.
4) After further work with the DSP, RTA etc. it's quite clear that de-emphasizing the 2.5-5k range by ~2 dB resulted in enormous improvement by smoothing out a somewhat overly bright presentation in this audible range. This wasn't obvious based on the RTA but the benefits were most clearly evident while listening to live tracks and switching this filter in/out of the mix.
I should add that the room these speakers are in is arguably on the large size. Vaulted ceiling central great room with integral kitchen area. Plus the speakers are at least 3-4 foot out from the wall. In a smaller room with speakers closer to the walls the above adjustments may not prove optimal. Which only goes to further support the efficacy of DSP in achieving optimal performance. One size rarely fits all.
While further tweaking of the DSP may yield yet more improvements, this full range driver in a plain vanilla box with a DSP in front of the amp is producing the best sound I've ever heard from a speaker. Or let's say as good a sound as I've heard from any speaker regardless of price including anything I've heard at shows.
This presents a quandry in terms of how to best package this together. One the one hand, offer the 10" boat hull full range speaker together with a preconfigured DSP in a separate box? Or...make this a powered speaker with integral DSP? Regards,
Morten