>Do you think something like blackhole 5 could be put in the Adire kit to get rid of the cabinet resonance in the bass?
>There's a rumbly sound? Do you mean some sort of harmonic distortion, or cabinet resonance, or a frequency response problem, or something? If such a thing exists, I'd like to fix it if possible in my speakers. I have noticed the Kit281s bring out a "texture" in the bass that I haven't heard in my limited experience, but I thought that was good, not a defect.
>OK, so it's a problem inherent in the driver that I can't fix? Darn...
====
Not so! The driver itself is overdamped (Qts = < 0.5), so this is a cab and/or alignment issue. If you look at Adire's FR plot for these you'll see that they chose an underdamped alignment (tilted up LF response). This causes what I consider to be excessive 'ringing' (degradation of transient/impule response) in the LF's harmonics, and I imagine what folks are hearing, especially since the room more often than not accentuates it.
Tuning the cab lower/increasing stuffing will help somewhat in some ways hurt in others due to the excessively long vent, but making a larger, lower tuned cab will correct it, and while it will sound 'tighter', it probably won't sound as tonally balanced overall unless the room helps enough, possibly requiring some (more?) baffle step compensation which I imagine will affect the XO ckt. design
Internally, the 'x' frame bracing causes mids/HF standing waves so damping their surfaces might audibly help. Also, in lieu of tuning it lower with the vent you can apply one or more layers of fiberglass or polyfil sheeting over the large holes in the bracing to somewhat aperiodically damp the cab/vent's pipe action.
Out of curiosity I modeled Adire's vented version and not surprisingly the results mimicked Adire's measured response and also showed the affect on the upper harmonics due to the woofers being placed near one end of the pipe.
Maintaining the same height/woofer positioning, but with larger Vas (4.66ft^3)/lower Fb (~31Hz) shows good pipe gain/flatter response down to 40Hz where it smoothly rolls off to a low 20s F10, and of course the phasing issues due to the woofer placement. My preferred layout is a bit shorter though, with the woofers ~centered down the cab to better utilize the pipe's action, reinforcing higher up the FR with the same LF response, though with fewer, more benign phasing issues, ergo less stuffing required.
How audible the differences are between a 'fatter version of Adire's design and mine is to a great extent room/person dependent, and more stuffing in the Adire layout appears to offset this, but either one should perform better overall. This isn't to trash Adire's design, all manufacturers stay 'under the gun' to keep size down and provide as much 'bang for the buck' as they can within pretty restrictive limits, and considering how many folks like a 'bouncy' bottom end, their design appears to balance the various tradeoffs quite well IMO. Judging by how popular they are, looks like a lot of folks agree.
GM
