I don't see how a driver can be 'too loose' for an infinite baffle installation. The driver is moving (displacing) air and if it runs out of useful excursion, then you have reached your maximum output. A stiffer suspension (lower Vas) will restrict the drivers efficiency at the low frequencies that an IB operates at. More displacement gives you more output, so the output an IB installation is strictly limited by displacement. If the driver is bottoming due to excessive subsonics, then a highpass filter should be implemented.
I don't see any of these drivers being unsuitable for an IB installation as they give you cost effective (but maybe not shipping effective) displacement. This says nothing about their distortion content though.
One of the major drawbacks of having few large drivers for an IB is the limited placement options which, in the end, cannot provide optimal response throughout the room. Two or more installations at the optimum locations would provide a far more even response. I would fully expect superior results from an installation of three or four separate 10" baffles, than one 18" baffle of equal displacement capability.
Also, in order to cancel out the mechanical vibration, drivers should be used in opposed pairs. This pairing also allows one driver to be reversed in a push-pull scenario which reduces a significant amount of 2nd order distortion. Again, these benefits promote the use of several smaller drivers over fewer larger ones.
One final advantage of using smaller drivers is that the manifold can be made to fit within the space provided by the floor or ceiling joists assuming they are deep enough. ie. an 8" baffle between 2x10 joists (approx 9" deep).
Earl Geddes suggests that three locations would be the minimum or optimum recommendation:
www.diyaudio.com/forums/showthread.php?s=&threadid=121590&perpage=25&pagenumber=3"I did a similar study where I used a random placement against a random (although centered in the space) data grid. Welte's and my results agreed "almost" completely, except that I found that
random placement worked as good with three sources as his did with four placed in the symetrical locations, as long as a few rules were kept:
1) place the source as far away from each other as possible
2) one source should be in a corner
3) one source should be above the rooms midpoint"
www.diyaudio.com/forums/showthread.php?s=&threadid=103813&perpage=25&highlight=&pagenumber=11"I have studied the LF sound field in rooms since I did my PhD on this topic back in 1980. There is no question that
exciting as many modes as possible yields a response with lower spectral variation than exciting fewer modes - this has been quantified in many publications - but in my books I go much further to discuss how to get good LF damping which spreads the modes increasing modal overlap and dramatically lowering spectral and spatial response variations. The net result of this room design and the use of multiple subs is by far the lowest spectral variation possible in a room of a given size."
Also see Earl Geddes paper, Subwoofer Placement:
www.gedlee.com/Papers.htm... while Toole came up with four:
In response to Tooles paper, The Acoustics and Psychoacoustics of Loudspeakers in Small Rooms
www.linkwitzlab.com/links.htmwww.linkwitzlab.com/Acoustics%20and%20Psychoacoustics%20of%20Loudspeakers%20in%20Small%20Rooms.doc"Regarding bass, the Schroeder frequency is that threshold above which room resonances are considered so close together that they can be ignored with respect to frequency response anomalies. Toole has found that this works for large rooms, but the formula for its calculation yields too low a frequency for small rooms. In fact, Toole believes that calculation of room resonances is irrelevant in real home listening rooms, because not all modes have an equal effect or are heard equally, since there are multiple sources (speakers), and because all the formulas are based on a source in a corner with the measurement taken in the opposite corner (where there is never a listener). This has led to Harman’s recommendation to
use four subwoofers in the center of each wall to provide the most uniform bass over the largest listening area in the widest range of small-room sizes; it reduces, and sometimes eliminates, the need for bass EQ."
Tooles work brought about this study which concludes:
Subwoofers: Optimum Number and Locations by Todd Welti
www.harman.com/wp/pdf/multsubs.pdf"One subwoofer at each wall midpoint is the best in terms of
Std, Max-ave and Max-min but does not support low
frequencies particularly well. Two subwoofers, at opposing
wall midpoints, performs very nearly as well as four at the
midpoints and gives a much better LF factor. One
subwoofer in each corner also has good low frequency
support, but does not perform quite as well as one
subwoofer at each wall midpoint, in terms of Std, Max-ave
and Max-min. If cost and aesthetics are considered,
subwoofers at 2 wall midpoints is preferred."
... also see:
Low-Frequency Optimization Using Multiple Subwoofers
Todd Welti; Devantier, Allan
www.aes.org/e-lib/download.cfm?ID=13680&name=harmanIf that link doesn't work, you can search for it here:
www.harman.com/about_harman/technology_leadership.aspxAgain, this thread is about cost efficient displacement. If you have anything to add or contribute, please feel free.
