Anyone else excited for this Borresen subwoofer?!!!

@deep_333 You are not understanding the physics of the situation deep. A powerful amp with a very low output impedance completely controls to motion of a well designed subwoofer driver. Music (sound) is not a series of stop and go traffic  lights. It is a conglomeration of sine waves. As soon as the cone passes the equilibrium point it starts decelerating gradually until it passes the zenith then it accelerates toward the equilibrium point again. The cone never stops, it just changes direction all under control of the amplifier and powerful magnets. Subwoofers do need help in other areas to provide that "you are there" intensity of a live performance, but servo control is not one of them. I owned a pair of Velodynes once. One of them is serving as a base for a fish tank. 

@deep_333 You are not understanding the physics of the situation deep. A powerful amp with a very low output impedance completely controls to motion of a well designed subwoofer driver.

@mijostyn , We can actually obtain high fidelity measurements (track the driver) and compare with instrumentation used typically in other fields of engg ....how well it was controlled or not....any driver+amp or a servo based system (LVDT, or a series of high sensitivity mini accels, conditioners and a DAQuisition system).

Until then, you could never be sure...

@deep_333  For example, a servo controlled driver will be forced to slam STOP quicker than some floppy/sloppy driver. It will result in the perception of FAST BASS! There may be other ways to do it as well. What is so hard about this to comprehend?

Oops, I didn't mean to criticize the ability of servo control rather the basic premise of the term subwoofer speed. I write poorly, my bad. "sloppy / floppy" that I'm going to use, thanks.

I replaced the Octavium with my first servo sub in the late 70's from Jonas Miller and Ken Kreisel at their Wilshire Blvd store. They had a stunning with and without demonstration setup there.

Now that I understood I was listening for I heard an even better presentation when I brought home Velodyne's ULD servo design and currently use two DD Plus. That David Hall, smart guy.

I believe the sub in my large Bag End ELF-M / S18E-D Bass rig has some control associated. 

@deep_333 wrote:

Paul’s vid describes the free lunch that he got with initial use of crappy drivers. How about this....Get the low distortion high excursion bells and whistles driver. Now, stack/integrate several of them so they don’t have to move as much for said spl level. Now, add servo control on top of it...it is incremental. It could all be overkill at normal listening levels, but, maybe not, because it is still the highest distortion component in the chain, relatively speaking.

It’s interesting to note that, with the knowledge and experience of being a servo-feedback designer himself (for the bass system of the IRS V’s), Paul is expressing how "everything is a compromise," and that - it follows - includes the servo-feedback circuit itself. What’s entailed in this specifically isn’t made clear, but it touches upon the aspect of a more purist oriented approach where, with a physically more all-out sub system, one can avoid "compensating measures" like servo-feedback, EQ-boosting and other. With the scenario you’re suggesting (i.e.: low distortion high excursion bells and whistles driver in stacks) the need for servo-feedback circuit will by all accounts be lessened, and so when will the insertion of such a circuit itself be deemed a larger, negative influence than the positive ditto it’s supposed to create? From my chair it appears that what Paul implies is that this is the very reason for them having omitted servo-feedback in their driver and amp upgraded sub towers, because servo-feedback wouldn’t have the desired, positive effect here when all is said and done.

As to the negatives of larger subs and the compromises that may or may not be involved here, structural integrity/enclosure resonances is the one area that is usually addressed. The important question to ask then, to me at least, would be to which degree subwoofer enclosure resonances of a certain magnitude would be an actual impediment in the reproduction of music, not least compared to the contribution of mechanical noise/distortion coming from smaller, direct radiating and inefficient woofers working much harder; would you rather have a capacity strained* small sub setup with more or less inert enclosures, or a capacity unlimited, larger ditto with what is still structurally sound cabs (i.e.: built with interlocked, CNC-machined and Baltic Birch multi-layer plywood, and heavily braced)?

From experience I can say with absolute certainty that, in each and every case, I would choose (and have chosen) the latter option. It’s no contest, period. How many have actually made an informed decision based on experience with both options? Close to none, because the by far most common scenario is that few even considers large, efficient subs for reasons we know all too well, and thus the only frame of reference to go by for most is that of smaller, inefficient subs.

On a related note, I have some coupled cavity speakers, i.e. the physical bass drivers sit inside and are cavity coupled to external radiators (Acoustic filter/ clean bass). One might argue that it is a unnecessarily complicated design. But, the free-er lunch there was that you didn’t need very expensive drivers trying to hit a price point (the expensive driver that may or may not hit a performance requirement just because you kept spending up the wrong tree). I know because i also owned a cost no object conventional speaker design from that same designer...a few different ways to do these things/clean it up, i suppose.

My quip would be: there’s no free lunch with smaller sub designs.

The good thing working with large, efficient sub designs is that of being dictated design appropriate woofers. Either you use them, or performance will be severely impacted (and who’d want that?) - that’s the deal. With tapped horns, like I use, there are very specific woofer requirements and a relative small specs-"window" to accommodate, or else the design won’t perform as intended. Like, too little motor/magnet force and the horn isn’t properly resonated; too much and the air pressure will be too compressed at the throat section and thus also not resonate the horn properly. Too light and non-rigid a cone is an issue as well, also because a cone too flimsy would simply be ripped to pieces with the uneven pressure built-up at the front side of the cone in the throat of such a design.

Build and board material quality is also important here. When the woofer cone really starts moving in tapped horns (and it takes a lot in domestic milieus) the pressure built-up inside the horn path can be so severe that the enclosure cracks open due to the immenses air pressure forces created inside (remember: the single 15" woofer per cab of my tapped horns is force multiplied at the mouth into the equivalent of two 18" direct radiating woofers). In reality such sub designs are built to withstand SPL’s at full tilt, why they’re rigidly built for that very reason - i.e.: design dictated.

*When are subs capacity strained? When there’s not enough if any notable headroom to speak of at the max. SPL one desires. What’s sufficient headroom? From my chair, no less than 10-15dB’s, preferably +20dB’s.

All technical and sensationalist jargon aside...the simple ability to delay the mains, very easily accommodated in the multichannel or pro world to make life a whole lot easier...but, a freaking rarity in purist hifi.

@deep_333 In many rooms you don't need it, owing to the fact that the best way to do subs is with multiple subs so as to break up standing waves in the room.

Below 80Hz in most rooms (unless they are very large) the bass has bounced all over the room before your ear can sort out what the bass note actually is. This is because at 80Hz the wavelength is 14 feet. So its had time to bounce off the wall behind you and pass by you again before your ear can even tell the note. 

If the note is cancelling the incoming bass note when it bounces, that is called a Standing Wave and no amount of EQ can fix it because the power you put into that result gets cancelled- you simply eat up amplifier power.

That is why multiple subs works so well- because if placed asymmetrically, they can break up standing waves so you get evenly distributed bass at the listening position as well as everywhere in the room.

So a time delay doesn't win you a whole lot in this situation.

Audiokinesis has a sub called the Swarm which is 4 subs each using a 10" driver. Because 4 subs might seem a lot to many people, they are designed to sit against wall to take advantage of the room boundary effect @mijostyn mentioned earlier.  The subs are designed to roll off at 3dB/octave starting at 100Hz to compensate. This allows them to be flat to 20Hz in a compact package (1' square, 2' high). Because there are four 10" drivers, they don't need to have to have a lot of excursion unless the room is quite large. Because they are meant to be placed against the wall, they tend to be more innocuous; very easy to live with, not just in terms of space but also very easy to integrate into a system!