Speakers for leading edge, transients, speed and big sound

@ditusa Bill Woodman who founded ATC in 1974 solved this problem by using "underslung" edge wound voice coils in a longer and tighter gap which eliminated the "offset" issue while reducing distortion up to 20dB throughout the driver's frequency range. In addition, this reduces the usual swings in impedance as well as radical changes in phase angels resulting in flat impedance response without resonances. The caveat being the need for enormous magnet structures along with considerable reduction in efficiency. Essentially though, you could use any type of amplifier typology to drive their speakers without harm to the amplifier but to get the speaker system to come alive you need minimally a hundred watts high current solid-state power.

"Example of a short excursion woofer that @larryi is referencing see here.

The JBL 2220 is a 15'' woofer with a short excursion and has a frequency range of 40 Hz-2 KHz while the JBL 2235 is a 15'' woofer with a long excursion and has a frequency range of 20 Hz-2 KHz. The 2235 woofer will reach two octaves lower in the bass than the 2220 woofer see here. 

Almost all HiFi woofers suffer from this problem (woofer dynamic offset) see below:

''Woofer dynamic offset is a problem long known about but seldom discussed or treated. With high input power at low frequencies, many woofers tend to shift their mean displacement forward or backward until the coil is nearly out of the gap. This is most likely to happen just above each low frequency impedance peak of a system. The result is a high level of second harmonic distortion and subjectively a bass character that loses its tightness at high acoustical output levels [4]. The cure for offset, as shown by T, H. Wiik [6], is a restoring spring force that increases in stiffness at high displacement in an amount that counterbalances the reduced B field at the extremes of voice coil travel. Such a nonlinear spider will in fact reduce distortion and eliminate the tendency to offset.'' See full article here."

 

Reading about the Meyer Sound Bluehorn in the MIX magazine article  (installation at the Fox soundstage for film soundtrack mixing) made me think of the original early efforts to bring sound to film using large horns, eventually augmented by woofers since the "snail" shaped horns did not deliver much bass. The Bluehorn seems to be a modern answer to large scale reproduction, taking advantage of current technology--active speakers with dedicated amps, using DSP to correct time and phase differences, etc. If you consider how well regarded some of the antiquarian theater reproduction systems are today (WE, Klangfilm, JBL), these may be their more modern incarnation. 

I did achieve a piece of this by combining the Avantgarde Duo with 15" subwoofers that use a relatively inexpensive outboard DSP system to flatten the response and got everything to gel the old fashioned way, through tuning by ear. But it's an unpredictable way to set up a system and it is obviously "tuned" to my preference in the room- not for perfectly flat response. And of course, much relies on the upstream equipment, all entirely tube based, utilizing expensive, hard to find old stock tubes. 

I'm not suggesting one go this route. (I gather the Avantgarde Trio has the option of utilizing their built-in electronics and crossovers to accomplish room integration at a price). 

There is something magical about the sound of a good horn system with SETs, though....

@devinplombier wrote:

I strongly suspect that I couldn’t live happily with speakers that are down 6 dB at 55 Hz (JBL’s spec), but I respect those who see beyond that. An additional caveat is that I have not auditioned the K2, and I am open to the possibility that their sound somehow transcends their underwhelming spec. Wouldn’t be the first time such a thing happens 🙂

The JBL specs are not really indicative of their true LF-capabilities, certainly not compared to the specs supplied by other hifi speaker manufacturers. Where JBL come from a pro history of relying on honest specs that openly reveal their specific measuring context, most hifi manufacturers on the other hand... do not. That is, the latter is somewhat more "creative" in their measuring approach, so take your own advice and listen to those K2 S9900’s before making any judgements.

Be prepared though - the K2 bass reproduction may not be what you expect; many anticipate a 15" woofer/midrange is about prominent bass wallop and blow your socks off-SPL’s only, but the K2’s produce a balanced, nimble, tuneful, agile and effortless low frequency bass that in many regards is really what "hifi" bass should be about (but mostly is not). Being also that they play up to about 700Hz they cover the important power region without the interference of a crossover point here.

Using a 15" that handles 700Hz while also being called to do LF is no small feat and involves compromises, but the 1500AL woofer (a fantastic piece of engineering in its own right) shows a way to do it with relatively few compromises. Having said that JBL has imposed design limitations on themselves trying to keep a manageable size factor, and to those of us who are not bothered by larger size and that dare to look outside the accepted brands, hifi segment and high price dogma, not to mention embracing actively configured speakers, there are even better options out there - and cheaper to boot.  

@larryi wrote:

I like the sound of the K2’s but, this being a matter of personal taste, I don’t think they are the best sounding horn-based systems.

 +1

@whart wrote:

Reading about the Meyer Sound Bluehorn in the MIX magazine article  (installation at the Fox soundstage for film soundtrack mixing) made me think of the original early efforts to bring sound to film using large horns, eventually augmented by woofers since the "snail" shaped horns did not deliver much bass. The Bluehorn seems to be a modern answer to large scale reproduction, taking advantage of current technology--active speakers with dedicated amps, using DSP to correct time and phase differences, etc. If you consider how well regarded some of the antiquarian theater reproduction systems are today (WE, Klangfilm, JBL), these may be their more modern incarnation.

By all accounts the Meyer Sound Bluehorns are an all-out assault that sonically levels most any other speaker out there - regardless of price (the Bluehorns aren’t cheap themselves at about ~$100k/pair, or even more). However there are quite a few theater reproduction systems of older age and much lesser price that, well implemented, will still do bloody good and more than hold their own against many contemporary, and typically more compact, much more expensive domestic designs. I never heard them, but those Klangfilm horns (of considerable size) should be very well sounding, not least on tube gear. On the other hand I’m very familiar with the Vitavox Thunderbolt's and their quite rare Black Knight horn systems, and they sound great actively configured with high quality, class A/B studio SS amps. Bring on older Electro-Voice and JBL cinema speakers that can sound great as well when actively configured with quality DSP’s (XTA and Xilica). 

Phusis,

Many good points are made in your excellent posting.  It would indeed be challenging for a big woofer to handle frequencies up to 700 hz.  A local builder uses quite sizeable horns and compression drivers that can go extremely low.  I recently heard a system where the crossover from compression midrange to woofers was set at 180 hz with a very shallow 6 db/octave slope.  The compression drivers were quite pricey, and if this were my system, I would insist on a higher crossover point and/or a 12 db/octave slope.  The woofers are twin 18” woofers made to his specifications.  The manufacturer insists on a minimum order of 40, and in the past three years or so, he has made three such orders.

@phusis 

Thank you for your response. Your point about "hifi" bass and what it is / should be about is well taken. I do agree in principle, but I do like some slam too, and I'm not resigned to the two being mutually exclusive.

I suspect that listening tastes play a part. For instance, I listen to a lot of electronic music.

In any event, I was curious about this:

to those of us who are not bothered by larger size and that dare to look outside the accepted brands, hifi segment and high price dogma, not to mention embracing actively configured speakers, there are even better options out there - and cheaper to boot.

Wondering if you would care to elaborate on some specific options you have in mind? Thanks!