My understanding is he choose 120 to avoid the resonance that the H woofer baffle creates above this freq.
SL says H-frames have a quarter-wavelength (IIRC) resonance near the upper end of their frequency range. The shape of the side baffles isn't there solely to make the speakers look cuter
but rather to break up this resonance.
Maybe, Josh ... but the Orion has a straight "open" baffle .. the Phoenix I think is the one with the H-woofer-baffle.
The Orion has sides, which makes the baffle part of the H-frame. The Phoenix uses a W-frame configuration.
I'd imagine that if the resonance avoidance that joshk mentions was the primary reason, there were still numerous others. Perhaps he wanted to move the xover point below the regions where human hearing is most sensitive.
This is just a guess: maybe he operates the drivers in the regions where they have best performance, such as lower non-linear distortion.
But, funny you should mention the Peerless woofers not appearing to do enough. They are in a dipole config and as such, have to move HUGE amounts of air to create the necessary spl's. I was thinking that they were doing too much! In my Orions and others I've listened to and whose owners I've spoken with, the bass has always been the rate limiter.
I'd like to point out how your comment is both correct and somewhat misleading. The Orions have a -3db point of 30Hz and are -6db at 20Hz. The majority of speakers don't have anywhere near this amount of extension at any SPL.
SL's Audio Artistry Beethoven design used eight 15" woofers per channel to get sufficient excursion to blow out anybody's windows. He didn't want the Orion to be so imposing.
I used the boost on the active XO to produce what I consider more realistic representations. It made a very large difference -- more than I'd anticipated. The mid-range has never been a problem in mine.
Turning up the bass in the ASP will alter the tonal balance, but it won't get you past the "rate limiter". The SPL is ultimately limited -- intentionally -- by the amp's power. Most people who visit me find, at first, that the bass is a bit louder than they're used do. I've measured the speaker's response and find the 0 settings on the woofer and tweeter branches of the crossover are just about right.
A friend came over the other night to "test the bass". (My friends like to try and trip up my gear. Some friends!) He played incessant europop, trance, other electronic music, NIN, Tool, and other stuff I never heard of. I measured 105db peaks, C-weighting, on my ratshack meter. A-weighted averages were often around 95db. He didn't miss anything from the music, even when the bass amps -- as designed -- were clipping and so limiting the woofer excursion. He remarked at least five times about detail and other things in the bass that he'd never heard before. The Orions come very close to subwoofer performance for music at loud levels.
Also, someone below implied that the slopes were 1st order -- 6db/octave.
They're 4th order.
Finally, ewietzman, how did you access the Orion forum in the link you provided?
I emailed the admin. The site will be down for much of today.
"Normal" philosophy would say "the woofers need much more power than the other drivers, so they should each have a 100w AKSA module". The others can have AKSA 55s.
No. SL specifically warns against more than 60 watts per bass driver. As awm pointed out, dipole drivers are asked to move a lot of air as frequency goes down. Dipole output drops 6db/octave, so the crossover boosts the signal 6db/octave. That would ordinarily result in tremendous power going into the drivers at very low frequencies, bottoming out the drivers and potentially damaging the voice coil formers. Instead of another filter in the crossover that limits very low frequency output and would add group delay distortion, SL just let's the amps run out of steam. Clipping harmonics are sent to the woofers and can't blow the other drivers.
... the mid-range spans a relatively high octave-range. If there is a 55w AKSA on each woofer ... is it possible that the mid-range should better have an AKSA 100 rather than an AKSA 55?
I've only seen the midrange amps clip once. I don't recall what I was doing at the time, but it must have been pretty crazy, like playing sine waves at high SPL. During the torture session above, the woofer amps were clipping from time to time because of the beats, but the mid and tweeter amps
never clipped.
- Eric
