Audio people know that loudspeakers mostly define the quality of sound reproduction. Also, everyone knows that the capacity of the loudspeakers mostly determined by the capacity of the drivers that loudspeakers use. Regardless of the topologies, applications and many other things.... if you have "bad sounding” drivers then all your further efforts become irrelevant. I usually with laugh look at many audio people who seriously pontificate about the importance of the minute details of their amplification or front-end but who disregard the fact the they load their entire system to the loudspeakers that employ drivers made from gravestone marble.

In this thread I will slowly posting information about the drivers that from my point of view defend own class. They are so good that the entire system might virtually be centered to serve an interest of this specific exceptional driver. I will be talking only about the drivers that I personally know and personally heard (like anything else within my site). If you have your own experience with drivers that you find exceptional then feel free to share your views about the Hall of Fame of loudspeakers drivers.

Rgs,
Romy the Cat

Let start from the largest drivers and go down. There are larger then 18” drivers (23” and 30”) but looking at this magnet structures I do not find them serious. I addition to make the 23” cone stiff enough requires a lot of diaphragm’s mass or to use very “bad for sound” materials.

The 18” driver would certainly be a woofer. If 18” driver used above 60Hz then it is misused. To my knowledge there was only one exceptional 18” driver even made… or perhaps it was a small family of the drivers that pretty much derive from one father: the AuraSound 1808 driver.

Aura made their 1808 driver in 80s and most of the 90s and it was wonderful. It had huge high-temperature neodymium magnet, unique magnet geometry with underhung 4" edgewound aluminum voice coil.  It was the only 18-inchers underhand voice coil ever produced. The finny part that despite of the underhand configuration it had 98dB sensitivity with 2” total excursion – what a motor! The driver had paper cone, cloth suspension and had phenomenal articulation at lowest frequencies. The 1808 was suggested for 20 Hz - 200Hz but it did not sound good even at 80Hz. The Aura 1808 had free air resonance at 24Hz and required enormous sealed enclosure of 14-16 cu feet.  Wilson Audio used the Aura 1808 in their unfortunately-ported XS subwoofers and soaked from their relatively small enclosure an extra 19dB of port noise at 20Hz.

The mid of the 90s was great time for the “exceptional 18” driver”. If you do not like the large boxes of the Aura 1808 (that in reality had Fs from 24Hz to 28Hz) then you could get form North Creek Music their version of Aura 1808.  They call it Leviathan and it was a next step into the wonder of the Aura’s motor. George Short (the North Creek Music’s guy) took the Aura 1808 and changed the cone’s suspension, effectively dropping the free air resonance down to 11Hz-13Hz. Now it was possible to use this driver in 5-6 cub feet sealed enclosure and get out of it an amassing bass in context or relatively low size, Sure you would not use the 11Hz Leviathan with 500W amplifiers, as the crazy pro audio people would do at their stadiums, but who cares about the stadiums?

There was a lot of controversy how to drive the Aura 1808. People use a lot of power; many hundreds watts… I always thought was not necessary for home use. I use Lamm M1.1, 110W of class A, PP hybrid. However the best result I was getting out of Aura 1808 when I drove it, believe me or not, by the Lamm ML2, 18 watt SET.  I did not feel that it was enough power but when it was enough the bass was like nothing else. So, what would be the scenario for use of the exceptional Aura 1808/ Leviathan driver? Two appropriately large sealed enclosures, with added mass (use Leaded Soft Density Fibreboard) driven by some kind of SET around 833A tube, relatively light loaded. (Or perhaps I might be the New Zarathustra hybrid? Will see….).

Unfortunately in the end of the 90s the Aura become the AuraSound and the 1808 driver become the NRT18-8. The NRT18-8 uses the same basic motor with slightly less sensitively and slightly higher resonance.  However, nowdays the AuraSound saturated their paper cone with epoxy to accommodate the barbarian 1000W amplifiers of the DJ installations. Epoxy on a driver’s diaphragm means an instantaneous death for sound and the new NRT18-8 driver sounds with no tonal discrimination at lower octave: juts a high quality generic LF boom.  The NRT18-8 sounds like a Boolean: yes-bass vs. no-bass, It is good for the Patricia Barber’s double bass and the taste of an average hi-fi Moron™ but it is very bad for any more civilized reproduced sound.

In the end, the Aura 1808 is the 18” treasury. In a proper sealed box it might give you an idea what theoretically possible to get out of the 18” driver. Find a good amplification for it, integrate it properly in your playback and forget about the lowest octave to the rest of your life. I doubt that more interesting 18” driver ever would be produced as there is no market demands for a good sounding 18-inchers… The Leviathan is no longer available, the beautiful Aura 1808 is replaced with Morons-accommodated NRT18-8, no one does 18” without those ports anymore… Cheating is good for high school exams but defiantly does not work for sound at lowest frequencies…

The exceptional 15-inchers would be two fitted in two categories: the bass 15-inchers and wide-range 15-inchers. It is imposable to think about the exceptional and wide -range 15-inchers and do not mention the 1946 -1973 production of the Tannoy Dual Concentric drivers. The idea was wonderful, the implementation was very good and the drivers (Gold, Red, Silver) are incredibly interesting. The 15-inchers Tannoy Dual Concentric require custom very sensible enclosure (the default Tannoy enclosures were compromised) that required a lot to taste and understanding. However, if everything is made properly then the Tannoy Dual Concentric does incredibly well. Of course the contemporary production of the Tannoy Dual Concentric is garbage….

Tannoy Dual Concentric

There is one interesting contestant thought…. I have unconfirmed evidence that the infamous Harry Olson had his own 15-inchers Dual Concentric driver. I heard a speaker that reportedly was Olson’s speaker and it was very interesting, free from some problems I observed in the Tannoys. Unfortunately during that the only listening session the Olson’s speaker was in context of an installation where was very difficult to say anything more critical…

That lead us to another category: the bass 15-inchers. The bass 15-inchers are the mostly misused drivers. It is know that the lowest octaves (sub 40Hz) and upper bass (above 40Hz) must not be handled by the same driver. So, if the lowest octaves are the target then why to stay with 15”? The Exceptional 18-inchers would be the direction to go. For the mid bass – the primary duty of the 15-inchers there are: Vitavox AK-151, Vitavox K15/40 and Altec 515G. They all pretty much the same drivers with very slightly different come materials but they all sound very wonderful. Vitavoxes is more advanced tonally then 515G but it is not an issues. The biggest problem is that the 15-inchers mid bass driver practically always misused.  The AK-151 and 515G have free air resonance around 40Hz and they are perfect for a 50-60Hz horn (I mean  a property done horn only). In the 50-60Hz horns they do phenomenally and really define their class. However, the Morons™ are not satisfied with 50-60Hz horns and they do not complement the 50-60Hz horns with the desisted LF sections. Instead they try to push out of their 50-60Hz horns lowers frequencies and by doing this they screw up everything.

Altec 515B

They mostly do it by loading their horns with 15-inchers of lower resonant frequency. There are quite few of them available (even Altec did the 515B and E with Fs of ~25Hz) but as soon this type of the driver loading a 50-60Hz horn then the problems begin as if a horn cares the acoustic pressure lover then it horn rate then it severally compress the 1-3 octaves above the horn rate. As the result we have a family of wonderful paper suspended 15-inchers drivers, with great tone but completely usable: you can’t put them in horn and you can’t put then in a sealed box because they have no excursion. The only suitable mid-bass application for the 15-inchers with Fs of 25Hz that I see would be a large line array of 6-12 drivers per channels where the combined sensitivity would not alloy then to hit their max excursion. Still, it should be only for smaller rooms and good lack to fit in them a pair of enclosures with a dozen 15” drivers….

Vitavox AK line

In the end the 15-inchers is very strange animals. Even for midbass they decay too fast in HF in most of the cases. People use them to get more pressure for the larger rooms. It has usually it’s own set of problems that it very deferent subject…I think that 15-incher should die out at ~250Hz-300Hz where the “fundamentals channel” should take over”. Before the “fundamentals channel” kick in, if you select the “15-inchers solution” then you would hardly find anything more interesting then AK151….

Oops, I almost forgot the size of 14”. This is kind of off the wall size but still there was two exceptional drivers in this size that I met.

The first is JBL 1400ND. The 1400ND was initially used in JBL K2 system. It had underhung voice coil, neodymium magnet and what is more important quite interesting sound. It was not particularly powerful driver but combined in array it was able to do very well in mid-size rooms. Nowadays the JBL 1400ND is long done and it replaced by 1500AL. I have no personal experience with 1500AL and do not know how good it does.

Another exceptional 14-inchers was Klangfilm KL-L405. It was far from prefect. It should be high-passed, it has low power handling, it had high resonant frequency for 14” and it had severs details deficiency. Actually it has no micro-details at all. However it has quite interesting macro tone that it in a way was exceptional. Properly used, in a correct horn and in relatively small room the KL-L405 was a very good solution for 70-500Hz.

I met once the filed-coil version of KL-L405. The electromagnetic version was very poor sounding and would not be suggested for any other reasons then just spread the electromagnetic paranoia and then sell it for some profit.

Rgs,
Romy the caT

Knightcrawler wrote:

The 1808 was designed for a large vented enclosure. Just looking at the TS numbers would indicate a large vented box to be best. It also worked well in horn loaded designs as well.

Knightcrawler wrote:

PS: The wilson Audio XS was a great subwoofer just completely overpriced.

Rgs,
Romy the Cat

Romy the Cat wrote:

Knightcrawler wrote: The 1808 was designed for a large vented enclosure. Just looking at the TS numbers would indicate a large vented box to be best. It also worked well in horn loaded designs as well. I did not says what it was designed for I said that “required enormous sealed enclosure”. I disagree with entire concept of recognition of T/S recognition in order the driver “to be best vented box”. How a driver could be at ”it’s best” if the ported enclosures do not produce acceptable sound? Also, Knightcrawler, the 18” throat with 2.5” max-to-max excursion? What link of horn you have in your mind? The only place where the 1808 was use were the shallow pro horns where the speakers “looked like horn” but essentially acted as direct radiators at lower frequency. Anyhow, I would personally never put the 1808 in a horn, regardless the side of the room (stadium).  Knightcrawler wrote: PS: The wilson Audio XS was a great subwoofer just completely overpriced.  Hm, I have to disagree with everything? Right? It was not necessarily overprized. It cost $18.000. A pair of drivers is $2.000, a well made <30 x <30 x >80 enclosure is ~$3.000, making it $5.000 all together. 50-60% of the dealer mark up is 10.000 and $14.000 -$15.000 all together. Add here the marketing expenses, transpiration cost, replacement and warranty cervices and it would not look like a lot of money left. Of course it is expansive from a different perspective (a person need 2 subwoofers) but those type of objective must be expensive. My major beef with Audio XS that if person do go for this level of demands and pays such a huge amount of money for subwoofers, dedicated amplification and space on his/her room then the person deserve to have more interesting result then a ported enclosure of XS is cable to deliver. So, I would not call the EX overpriced but rather unreasonably designed. Rgs, Romy the Cat

Knightcrawler wrote:

The 1808 in a vented box produces some of the best bass I've ever heard. I know some have a beef with vented enclosures but when designed right the sound can be brilliant. I've heard plenty of sealed, vented, bandpass and horn loaded designs. The 1808 is pretty tremendous in a well design enclsure and a powerful amp. A neighbor has two Wilson XS and loves them, they sound great for classical music and movies. The ports are to small for the design but the sound quality didn't seem to suffer from it.

Knightcrawler, well we basically agree that the 1808 was a wonderful driver. Let keep our views about the cones and pros of the ported enclosure out of the thread. It was the “best bass you've ever heard” but you did not hear the 1808 identically well implemented in appropriate sealed enclosure, didn’t you? Also, I have to give to the Wilson XS some credit as the ported enclosure if you cross them very low (25Hz for instance) do not manifest many negative characteristic as there is not sound in there anymore but juts pressure. BTW, do you know that Wilson use the 1808 on few reiterations of their Whow subwoofer.  I believe they have 4 versions and one of them was made with 1808. Do I have to say that it sounded way more interesting then Whow usually did?

Rgs,
Romy the Cat

We enter a complicated region as the lower driver we go the drivers could be used for different purposes and it is very hard to generalize. A 10-incher might be MF driver and LF driver. In my past I experimented with few MF 10-inchers, including some vintage field-coil 10-inchers, but I was not able to find any interesting driver. Giving this I have to note that in context of acoustic system that I was experimenting I had no proper application for 10-incher MF driver. Still, I did not see anyone ever has any reasonable use of the 10-inchers in MF. Sure there are wonderful older Tannoy dual-concentrics 10-incher but they are for different purposes. I’m sure that for correct application it would be possible to find/make a good MF (to be more precise: lover midrange – upper bass) driver.

What I did search and experimented were 10-inchers woofers. I very much like the Scan-Speak woofer made around their SD1 motors.  They use a very interestingly intentionally overhang constriction that has very soft sounding “enter into distortions”. The cones are very soft and the rubber suspension is very interesting for given resonance frequency. It has 20Hz of Fs but the suspension is not soft and uncontrolled like with most of the drivers. They are kind of stiff but flexible at the same time. What is the most beautiful in them that the “stiffness” of the suspension is very “smartly” relates to the firmness and mass of the cone. As the result, sonically the driver’s cone and the driver suspension act together as a semi-“varimotion transducer” when the stiffness of the cone is not identically access the cone but gently changes with radial proximity to the peripheral. Of course they are very much not varimotion but the special anti-resonance rubber that Scan Speak uses in their 25W/8565-00.

It is important to mention that there is a faulty notions the LF driver should act as a piston and the cone should not break. I do not feel this way and the best sounding “bandable” and breakable paper cone drivers are the direct evidence of it. Tone it is exactly what comes from the “band” of cone and it the cone is too stiff that you have the “jazzy upper pPPP’ass” bass…

For a first time I discover them when John Dunlavy introduce his Dunlavy SC-IVA model as a replacement of SC-IV. The SC-IV wee horrible speakers but had no bass at all, despite of their size. In the SC-IVA Dunlavy trashed the garbage drivers that he use and put the 25W/8565-00 in the game. The result was remarkable and the SC-IVA had much more interesting bass then SC-V and monstrous SC-VI. Of course Dunlavy normalized impedance of 25W/8565-00 and did some other thing that screw them up but still, even given all of this I feel that Dunlavy SC-IVA  (if they were properly used) had the best bass among all commercial speakers.

The only problem that I see in the 25W/8565-00 is to low sensitively. The key with them is to use more of them. Still, they do not handle a lot of power and should not care too much upper bass sound in them. I cross the arrays of 6X25W/8565-00 at 60Hz, first order and I do not feel that it is best configuration for them, since my line array is essentially a compromise between a line array and not existing midbass horn. I feel the best crossover point for 25W/8565 would be 40Hz and second order. It would be interesting to put them deep into low pass transition slope but with the restricted power handling it would be difficult to do.

So, if you find any other 10-incher with primary resonance of sub 20Hz and with “this tone” then let me know. Until then I would consider the SS 25W as an exceptional driver. Still if this drive would be 100dB sensitively then it would be ….more exceptional…

Rgs,
Romy the caT

NBC wrote:

1) What dimensions for 1808 baffle would you suggest?

It would be easy to circulate from the resonance frequency of the driver. The 1808 marked at 24Hz but in practice it could be anything from 23 to 29Hz. Since you will not despite a lot of power on the driver I would drop own resonance frequency as low as possible. The Northern Sound made it as low as 11Hz that should make the box much smaller. With default version go big, 14-15 cub feet will not hurt, larger is better but the exec number should be calculated, it very simple.

NBC wrote:

2) Is floor-firing vs. front-facing cone useful or preferred?

NBC wrote:

3) Any *general tips* about placement of 1808 cone(s), in relation to midbass horn channel (e.g., time alignment) and room boundaries?

NBC wrote:

4) Your thoughts about digital equalization (DEQ2496) for <50Hz subwoofer channel ONLY?

A few points I would like to make. I do not know if the Northcreek dropped resonance by adding mass or by softening suspension. I hope they leave the cone along and softer the suspension of the driver instead off adding mass. Sure it would reduce power handling but acoustically suspended it would not be a problem for this driver. The 1808 was made to handle a huge amount of power in pro applications and a few dozen of watts on the driver in a small listening shoe-box room will not really stress the driver to its critical excursion. Also, some words about the McCauley 6174 and possible other contesters. There are good drivers out there and many companies (I do not mean the McCauley – I never had thier drivers) love to say about their drivers high excursion (with is not necessary is better BTW). However, what the companies always “forget” to mention is what percentage of their excursion is in the “underhanged” mode. The driver can run even across 4 inches but as soon the driver coil jumps out of the area of the linear magnetic lines of the perfectly saturated gap then any further excursion is good only for Rap music and for the taste of the Absolute Sound “writers”.  (in fact the moment when the coil switches from the underhang to over hang more is the worst) The whole beauty of the 1808 that it has a small “emerged” coil (it’s with high sensitively as the same time – big rarity!) and “complimentary” to the small coil it has a long “active” gap. This keeps the coil move in linear magnetic invariant over a very long excursion. If I am not mistaken then it is 1.5” in undaunted mode out of 2” of total excursion! I it the highest numbers among all know to me 18” drivers and this is what set the Aura motors apart… It is from one point of view a huge waste of magnet… but is it what it sounds so good.

Hm, the 18mm out of 50mm in “fully in-gap mode” for Aura? It sounds too bad.  The last time I touched this subject it was 6 years ago and I remember I had better impression in term of the numbers.

I just looked at the Aura page:

http://www.aurasound.com/public/discontinued/images/spec/nrt1808_b.jpg

It has Xmax = 18mm(.71”) but, Jessie, you forget that Xmax is one-way excursion.

The next page sad:

http://www.aurasound.com/public/discontinued/images/spec/nrt1808_a.jpg

The Linear Excursion (pick-to-pick) 38mm (1.5”) out of 50mm (2”). That sounds more what the “consumer” numbers that I remember.

Also a few further comments. Aura is 5dB more sensitive then McCauley.  The other notable difference is the material of suspension. McCauley suspends fiber cone with rubber, while Aura uses fiber composites and suspends it with soaked fabrics. The epoxy reinforcement that you mention used only in Aura to glue the cloth to the driver. It  is not much epoxy but it is still not good – epoxy must not be use anywhere on the drivers (though we do not know how McCauley glue rubber to cone).  O do not know the neodymium vs. “soft iron magnets”. Generally higher BL factor considered better but it is not always the case. It should be heard in order to recognized how it warks all together.