Originally Posted by bwaslo
Actually, the (co
siderably cheaper) Eminence 12" woofer we used sounded a LOT better (to me). The whole speaker sounds quite good now (not just loud). Could see no difference in distortion measurements between woofers, though. Odd. Distortion was low (<1%) and about the same for either, up to as loud as we wanted to measure with (maybe 105dB) with no hearing protection. Freq responses were very nearly the same, too.
The thing about the heavy cone I'm thinking is that a woofer puts most of its energy into shaking its cone back and forth, coupling to air is very low even with higher efficiency drivers. The B&C gets its efficiency with a beefy motor (Qes of ~0.18) but heavy cone; Eminence does it with a lighter cone. A shaking heavy cone will put more vibration into the cabinet than a light cone will (action/reaction if you remember that stuff from high school). So maybe the B&C excites cabinet and baffle resonances more than the Eminence? Maybe. Erich's cabinet is built like a tank and has a double baffle, but still the surfaces of the box are big. If this all holds water, then lighter cones are the way to go. Erich will be trying a more upscale Eminence driver I think, see if that's better still (though I personally don't see that one we used needs any improvement).
Very interesting Bill.
Somewhat related to this is an issue I've mentioned and inquired about either in this thread, or the "Hey guys, we need some rallying" thread. Clear to anyone paying attention, essentially the entire SEOS platform is a giant killer/over-achiever. I mean everyone involved should really be proud of what has been accomplished here. The waveguide design and execution is commendably state of art.
Granted, although my projects and level of hands-on experience in DIY loudspeakers likely pale in comparison to many here, one element of the various SEOS offerings really stands out to me as a potential issue. In my opinion, it would appear as if the one potential "Achilles Heel" of the finished loudspeaker during playback, is the mid-band backwave energy's potentially corruptive influence on the output. At some point, when Erich was asking what everyone was interested in regarding the next evolutionary step in the SEOS lineup, I've suggested the enclosure ... and examining the backwave environment.
Obviously the octaves covered by the waveguide are golden. Similarly, the bottom octaves are well handled. However, the upper half of the LF driver's range seems to me to be the most vulnerable element to high performance (transparent, low distortion playback, at realistically high levels). So any attention to this area, whether it's a different cone as you experimented with, or more radical approaches such as a fully damped open back, or equivalent technique. This in an effort toward greater resolution ... perhaps via lessening detrimental backwave energy, ... perhaps helping the magnetic circuit to better track the signal. But ultimately, and maybe most importantly, allowing the cone to more accurately resolve the micro-dynamics that render the complex textural components of the recording that lead to next level realism and greater overall enjoyment of the experience.
I'm picturing some manner of open back, not dipolar, ... but somehow employed uber damped backwave area, as to maintain design directivity goals, etc., but also render the backwave essentially a non-issue ... black hole style. Integrating such an approach with either a screen wall, or baffle wall, would make things much easier with a custom solution. But it sure would be interesting somehow bringing these attributes and integrating them in a typical stand alone box. To maintain proper LF alignment and balance, it would seem a three-way like the Maximus is ideal.