The short answer about a more bass and a woofer is - Yes. I'll offer some explanation.
First Issue:
Cone stress and the need for an extremely stiff cone does NOT happen for a cone operating at low frequencies. I know this remark flies in opposition to some common paradigms, but it is true. Three gentlemen much smarter than me have confirmed my thinking (Joe D', Sigfried Linkwitz., John Paulsen and Jeff Glowacki) during a visit to CES in 2002. Joe D actually explained the phenomena to me, and the other two gentlemen verified. I must give credit where credit is due.
Joe D' mentioned that the Usher 10" driver was quite exceptional. After some conversation I understood the reason why. The Usher 10"is a simple doped paper cone. Intuitively this is quite plain and certainly not special. Nonetheless, Joe D' said it was very good. I found this rather strange. I asked him if the soft paper cone caused some loss of resolution due to its lack of cone stiffness. His further explanation made very good sense. He asserted that low frequency reproduction activity for the cone is quite slow, and exerts little stress on the cone. The cone does indeed move a long way back and forth, but this activity happens very slow. Higher frequencies are a different story. At higher frequencies a very stiff diaphram is preferred because of the extremely fast transitions. A cone wiggling/moving at 2000hz is either very stiff, or very floppy. This is where a very stiff (commonly metal or ceramic) cone will perform exceptionally well.
The onset of cone wiggle is dependent upon cone stiffness and the operating frequency. The ultimate objective is a solid piston throughout the operating range of a cone. This is why Joe D' thought the 10" Usher was good. It is crossed quite low.
So, the use a metal cone when crossing low is foolish. A good doped paper cone will be equally pistonic. If crossing a woofer high, then sure, a metal cone is smart. It will remain a piston at high hz. It will create some crossover difficulties, but ya' can't have your cake and eat it too.
Second Issue: Ported versus sealed - dampening
There is some very good science about driver application and dampening. Such theory is very valid and suggests that a driver in a ported cabinet will have proportionally less dampening (more air-spring) due to the ported cabinet. The Qtc of a common ported cabient is 1. The sealed cabinet will commonly have less air spring, and the same driver dampening. The same concept can be applied to automotive springs and shock absorbers. Less cabinet spring in the sealed cabient means that the Qtc of an ideal sealed cabinet will be lower. There is some discussion about what Qtc is best, but a sealed Qtc of .6 to .7 is considered good by many. A smaller sealed cabinet will offer a stiffer spring and a higher Qtc will result. This Qtc might be .8 or .9. A slightly larger sealed cabinet will have an even lower spring force, and proportionally higher dampening.= and result in a low Qtc aligment. .707 is considered an average Qtc. Qtc numbers above this are considered high "Q". Qtc numbers below this are considered low "Q". The low "Q" sealed alignment seems somewhat coveted by the knowledgable.
However, I don't think this is the major consideration for a ported or sealed woofer. There are surely many midwoofers in a ported alignment that sound very good. The SS8545 is generally considered to be the king of bass for a midwoofer. I agree. The bass from this woofer in a ported alignment is extremely good.
Building a woofer for a sealed cabinet requires some other NON-Marketable characteristics. The hz depth that any woofer will play is determined by the resonance frequency Fs and the Qts. Drivers with a lower Fs will play lower. Drivers with a HIGHER Qts will play lower. A driver for a sealed cabient must have a higher Qts. Qts values above .4 are generally viable for a sealed cabinet. Obtaining this happens through a lower Bl (force) factor. Unfortunately a lower Bl factor also translates into less sensitivity. This is obviously less marketable. So, the cost for a woofer in a sealed cabinet is generally a couple db of sensitivity. The common consumer would surely never accept this. There is also some focus on the Qts of the driver, and I will agree that a lower Qts drivers do sound tighter. The unfortunate downside is that low Qts drivers don't play deep bass. Again, ya' can't have yer' cake and eat it too.
Soo, which alignmet is better?... Don't answer yet. Wait... there is more! Remember the Ronco Glass Froster? I ain't done yet.
Third issue: The rolloff
I believe the very most important woofer asset is the ability of a woofer to match the in-room response. This is because woofers are used in rooms. At about 40 hz in a normal size room there is room coupling that WILL occur. At 50hz in a small room there is room coupling that WILL occur. The degree of room coupling depends on the size of the room and the wall construction. I'll assume that coupling in an average room starts in the high 30's and extends downward. At 20hz there is 5-8db of room lift.
First, I need to address the issue of and octave. An octave is a doubling of frequency. 20-40hz is 1 octave. 40-80hz is 1 octave. 80-160hz is 1 octave. 20-160hz is 3 octaves
A ported woofer wil roll off at 24db/octave after the advertised f3. This means that when the 1801 starts the roll off at 38-40hz that it is approximately 24db down at 20hz. Since the room lift is only 5-8db, the signal remains 16-19db down. It will NOT be audible at 20hz. Heck, it'll barely be audible at 30hz.
A sealed woofer in a Qtc cabinet of .707 will roll off at 12db/octave. If the woofer begins to roll off at 37hz it will be about 10 db down at 20hz.
A sealed woofer in a low Q alignement will roll off slightly slower. A sealed woofer in a Qtc cabinet of about .6 will roll of at about 10db/octave. If it starts to roll off at 39hz at 38hz will roll off at 9db down at 20hz.
Based on the information above, it'll probably seem quite apparant what woofer I plan to use. This project will matriculate sometime next fall.
The downside to this is the very large cabinet. It isn't possible to accomplish this in a monitor/base setup for the 1801. Some quick calculations reveal that a 3.5 - 4 cubic foot cabinet with 1 1/2" thick walls + bracing will be friggin huge! This will not be acceptable in the living room for any respectable housewife.
I could use a lessor driver in a smaller cabinet, but really don't want to make compromises in any other direction. Also, the intended driver sounds.... well.... I'll let other folks comment on the sound quality of the SCC300.
Fair warning though. The cabinet takes me a very long time to build, is extremely heavy. The crossover componets will also be very large, and the completed speaeker won't be cheap.
There are other issues too, but my comments above encompass the major issues regarding the decision of a woofer.
Please let me know if you have further questions. I'll do my best to address them.
Dave
