You Cant Buy It but you Can Build It

@jasonbourne52 , Bob Carver does things just because he can. The cube has to take such long excursions its distortion increases dramatically at volume and sometimes you can even hear the driver moving. His best item in it's day was the Phase Linear 700, the first decent sounding high power transistor amp.

@mahlman , put on anything with a little low bass in it and turn it up to your usual listening level. Put your hand on the bass horn say just inside the mouth. Feel that vibration? Any vibration you feel is audible distortion. Getting any large structure not to vibrate at bass frequencies is extraordinarily difficult. This is the problem with bass horns. They add way too much coloration. You would literally have to make the horn out of concrete. Getting a small enclosure not to resonate is difficult enough but a horn is virtually impossible. There are very few horns that make it below 30 Hz. The K horn is already down 4 dB at 33 Hz. A horn that makes it down to 18 Hz would be huge and even more difficult to control. The driver is happy as a clam, the horn itself is an audiophile nightmare which is why you do not see or hear many of them. 

@phusis, sorry lad, it would appear your experience is lacking. I have heard and built Horn subwoofers. Mahlmans's sense of vibration is not good. I hope he is not diabetic. The other answer would be that his horns do not go very low which is in keeping with his other posts.  Yes, horns are very efficient but, bass is bass and it is very powerful and hard to contain. Any subwoofer, horn or otherwise putting out 20 Hz at 85 dB is going to shake and it is going to shake the entire house. Making one that does not vibrate with just the distortion produced by the driver is virtually impossible. There are examples that come close, Magico's Q subs come to mind. I might be able to do better. We shall see. I have been designing and building subwoofers for almost 40 years.

As for horns being the best type of driver, they have their advantages. I am waiting to hear a horn system that is not colored. They also require crossovers. IMHO the best type of system is a one way driver crossed to a subwoofer below 125 Hz where digital bass management is easy to apply. The only one way driver that is truly one way is an ESL. With horns you are also stuck with a point source system. It does not matter how big they get.  Line sources project power better particularly in the bass and are more capable of generating the visceral sensations of a live concert.  

@stereo5 , sorry to hear about your experience with the Dell. You never use the sound card in the computer. You use a USB DAC or a USB to SPDIF converter to a DAC. IMHO for audio use Apples are better. With programs like Pure Vinyl and Pure Music you can go anywhere and produce state of the art results. 

@mahlman , your organ must not go down very low. When I crank mine with a recording of the Boardwalk Hall Organ the cones of all four 12" subs move an inch and your vision blurs. Fun!

@phusis , I did not say there were not other ways. They are generally a lot more expensive, not any better sounding and have limited functionality vs a full fledged computer. My system doubles as a theater. I can also stream videos and movies as well as any audio service. I can record records to the hard drive and AB various versions of ...you name it. IMHO music servers are an insane waste of money. It is like comparing the pricing of commercial vs consumer audio equipment. Hint, professionals are not as easily conned.

One last thing. The problem with ears is that they are connected to a brain and when brains are concerned all bets are off. Example. Have a dispute with your wife then go mow down 50 people with an SUV. Sometimes brains really s-ck. 

The material a surround it made from really does not matter. It is the design of the surround given the drivers intended use. Certain designs work best with certain materials. Subwoofers need a large X max and a long throw, low compliance suspension requiring large dual spiders and butyl surrounds. Foam surrounds are a poor choice for subwoofer drivers as the stress causes even the good foam to disintegrate. 25 years is not good enough. A suspension should never fail.

@mahlman , unless you are using an insanely large driver (21") you are not going very low at all. In order to move the amount of air required to produce a 20 Hz note a 12 or 15" driver has to move quite a distance especially at volume. Even at moderate levels the excursions would be plainly noticeable. If they are not then your woofers are not doing anything below 40 Hz. It is simple physics and it does not matter what type of enclosure you are using. Distortion does increase with excursion distance after a point. Modern subwoofer drivers can easily do 1 cm excursions without distortion, some up to 2 cm. Down below 40 Hz it is not what you hear that counts. It is what you feel. A 20 Hz sine wave played at just 75 dB causes my entire house to rattle. I have four 12" subwoofers in a 16 foot wide room and you can see the excursions across the room. I made my enclosures with Corian laminated to MDF with a layer of glass microspheres in between. Each one weights 200 lb. They are sealed. 

@mahlman , you have to be very careful with specs when it comes to bass. What a speaker does at 1 meter is a far cry from what it would do in a room at 3 meters. Most woofers can move fine at 20 Hz but it does not mean they are actually radiating the sound with any authority.

@phusis ,I am honored that you would spend so much time analyzing my post.

It sounds like we are on the same side of the ile. We both use computer audio and not dedicated music streamers like an Aurender. I suspect you are a PC guy and I have to admit that my computer knowledge is somewhat lacking. But, the sound cards I have heard, and I have not heard all of them did not sound as good as an Apple driving a Berkley Alpha USB. They were obviously veiled for some reason and I suspect why many dis computer audio. I would not go any other way.

My point about brains is that each brain has it's own way of interpreting it's senses. Some interpretations are better than others. Just because someone thinks a certain something sounds better does not mean it will to other people. You can only trust the opinion of other people who interpret sound the way you do. I have two such people in my life. A multitude of issues will determine sound interpretation, looks and price are the two big ones. In my world they do not count one iota other than there are certain pieces of equipment I like that I can not afford, at least for the time being. 

You are quite correct. Horn loaded drivers do not have to work near as hard because they are impedance matched to the air. Very few people use subwoofer horns because they are extremely large and they tend to have their own resonance problems. Forgetting about horns everything else I said is true. Someone mentioned foam surrounds as being best. It depends on the design and intension of the driver. I will say if you see a subwoofer with a foam surround, run away. I have seen to many of them fail including the Velodynes I ran for a decade or so. One of them is now the base for a fish tank. The vast majority of sub drivers are made with butyl rubber surrounds for a reason. 

Take any pair of 12" or 15" sub drivers in an appropriate sealed enclosures. Put them in a 15' X 30' room, cue up a 20 Hz test tone and turn it up to 90 dB. What you will see are cones flying in approximately a 1" blur, a little less for the 15 cone. What you will hear is your whole house rattling. This is not my local context or my opinion. If you do not know this it is because you have not built enough subwoofers. What is "local" is that I only expect dynamic drivers to make noise below 100 Hz. Most residential folded horns run up to 350 Hz. K horns used to be 500 Hz. That is not bass anymore. Middle C is 256 hz. It is well into the midrange.Then you are faced with another huge problem. A large chunk of your midrange is five feet behind the rest of your speaker. That is a 5 ms group delay! In order to make that work you will have to biamp the speaker and put a 5 ms delay on the high frequency drivers using DSP. I always wanted to try that with K horns to see what you would get. I have another local problem. I use Line source loudspeakers. In order to match their radiation characteristics I had to create a line source subwoofer array using 4 subwoofers. On a 16 foot wall 4 subwoofer horns would be a site to see. I am working on a new system with 8 subwoofers. The four 12" subs I am using right now are working too hard and on occasion I run them into their bump stops. They have a X max of 19 mm. That is a 38 mm excursion. In a 16 foot wide room.  It takes a lot to make powerful sub bass, a lot more than most people think. I do not have any problem with multiple drivers. I would use larger ones but then the size of the enclosures would be prohibitive in my "local" situation.

@wvgraber , Nice System, my feelings exactly. 

@mahlman , no I am not debating myself. Being the SOB that I am I am simply stating reality for what it is. If you want to cut yourself short for whatever reason that is your business but trying to convince people that you can have decent bass with woofers that do not move is another thing all together. Then you back that up by saying you do not like it (bass). If it does indeed hurt your ears that is awful and I do sympathize with you.

My subwoofers were designed for music not Star Wars although they do the Star Wars thing just fine. That was not the intension. 

Feeling like you are at a live concert requires low bass. There is no way around this. Without it you have a run of the mill Hi Fi. Might be a great run of the mill Hi Fi but, it will not be convincing in the least. Having said this rather harshly I have to admit that realistic sound is not everybody's goal for one reason or another but, nobody has ever told me this is not the ultimate target for the serious hobbyist and my point of reference when evaluating systems.  What other reference can you have?