I recently made some highly attractive changes with the way in which I use S2. Now, since the S2’ top got cleaned up the universal misery of universe bothers me tremendously. :-)

Really, the S2 runs in my 400Hz horn up to 12.5kHz and the S2’s 12.5kHz sound more effective then TAD 4001’s or JBL 007’s 20kHz. I was trying to compliment the S2 with tweeter but it really unnecessary. Most of people out there use the S2 in thier default 330Hz 26” horns that put the driver deeper into the horn where it cuts-off ~2kHz. With the shorter horn the last 2khz jumps out and the S2 do not really need any tweeter. Well, it would be nice to have one (do not ask me why – probably juts in order to please my spectral-analyses) but I do not think there is any tweeter out there the would be able to handle what S2 dose at 12Khz.

Now, how should I use the bottom end of the S2? This is real dilemma! From one perspective I might drop the crossover point and drive it at 500Hz into 250Hz horn. But then I will loose 2kHz at the top. I’m clossing now the upperbass at 70Hz where the S2 kicks in… So, I was wondering.... How about to palace the S2 into an ultra-small ~5kHz horn and then to compliment it from bottom with another S2 in 250Hz horn at 500Hz. In the 5kHz horn the S2 will push probably 16hz and it will be HF that would be untouchable. Ay the bottom this HF channel will face the identical driver in a larger horn. The lower knee of the HF channel would decay acoustically with the horn rate and the low pass on the MF would be a first order. Considering that the are identical drivers it would not be problem to have a tail of any length in there…

Hm, this sounds quite interesting. At the bottom S2 channel I would use probably a plastic diaphragm as they can dissipate more power and less prone to that cracking… This sound quite attractive… Did anyone went to those extremes of Votavoxisisation?

From a different viewpoint now I have the S2 running in it’s optimum configuration for 4-way installation: S2 has a spare octave at the bottom allowing a nice midbass channel entry and it sits in a shorter and wider horn allowing to use it’s maximum HF. What the hell I want from it? I want somebody else to try and tell me how it was… Then I would object it... :-)

:-)
The caT

cv wrote:

The acoustic transformation's probably done by the time the wave reaches the throat.

Yes, it is. If we loom how the S2 internal channel done then it would clearly indicate the it should not be a great tweeter but what whatever reasons it is. Go figure…

cv wrote:

I'm currently running *one* S2 barbarically, while tweaking a few things. It's x/o'd 1st order before the amp at 500Hz on a 340Hz JMLC horn. Btw, the JM flare has a "T factor" parameter that can be used to control how open the flare is - larger T, shorter horn - you may be able to produce a horn that loads the S2 correctly down to 500Hz without sacrificing top.

Are you saying that the JMLC curve could be shorter then tractrix to the same flare rate?

cv wrote:

What you really need Romy is to find someone who will build 2 scale models of the S2; one twice the size for midbass and one half the size with electropolished phasing slits for tweeter duty, stick the standard S2 in the middle and you're done...

Here we go! Not we are taking!!! I would not need the S2 tweeter and what it dose now in 400Hz horn is perfectly enough. I would go only for the midbass S2.  Something with 6” cellulose diaphragm, low to medium compression, 3-4” throat, >2T in the gap and with Fs around 80-90hz. Something similar to the Community M4 compression driver only that would sound good

Ok, now I am officially hallucinating..
The caT

guy sergeant wrote:

If you use the plastic surround S2's from 500-5KHz won't you still have the bulge that concerned you at around 1.2K? I thought you suggested that the metal suspension units didn't have this bulge.Otherwise it seems a nice idea, albeit a bit expensive for many of us to try.

slowmotion wrote:

JMLC made a spreadsheet based on his approach to designing horns, with that spreadsheet you can design almost any kind of horn you wan't to.  We should maybe have Jean-Michel describe his theories himself, but I don't think he is on this list?

cv wrote:

Well, the Cogent (Steve Schell and Rich Drysdale) boys are building just such a beast: field coil magnet, (possible) permendur polepieces for >2T, Fs 70Hz, throat - dunno, but at least 3" dia, reduced compression ratio relative to midrange units. They tried various diaphragms, phenolic originally but I believe have decided that carbon fibre is king [cv ducks for cover...?]. I've seen pictures of the internals of the drivers and they certainly *look* incredible. A very, very early prototype of the smaller midrange unit may be seen at: http://www.oswaldsmill.com/id29.html but you've probably seen that already.

Yes, I have seen them; never head what those guys do though. I had some concerns about that project. I read somewhere that they were planning to put this drive all the way up to 10Khz, equipping it with some kind of phase plug and so on. I do not think that it would be good idea. The base theory of horn loudspeaker contradicts the wide frequency operation. I would personally love to have such an upperbass driver optimized from 70-80Hz to sub 1000Hz, which would perfectly fit into the 4-way installation.

Anyhow, no one never knows why those compression driver sound in the way how they sound. We get pretty much sound “as is” from those drivers and try to make out of it something. All drivers that I like of use do not do well on the specks. The very same S2 driver has very ordinary datasheet. Go figure how they all will sound!

Anyhow, I was argue (my normal state of mind) with someone of Cogent boys in past about a necessity to use a paper cone for mid bass driver (even compression). At that time they were big on the metal cones. So, you said that now they have decided that the “fibre is king”… Dose it mean that I won and now I can pat my ego :-), or perhaps to have the driver to try? Also, I hope that this drive will not come with a digital EQ… :-)

cv wrote:

As for JMLC, I don't have his email address, but you should be able to find his details on the web. That musique concrete site that Jan attached was very interesting - a French fella by the name of Marc Henri did some interesting research on the damping properties of different horn materials. He uses a similar flare horn as I have for the S2, but made of plaster of paris IIRC.

I do not really think that different horn materials are so important. The horns obviously should not be made with the Coca-Cola cans (courtesy to Altec-BL-Klipsh-EV-Vitavox and many others). A proper horn should have above critical mass that should be projected to the lower cut off frequency (LF push to mass). If is it heavy enough then the material become irrelevant but if a horn is too light for the given lowest frequency then the material maters. I think in those concrete horns the material is very secondary (they have enough mass and it is all the they should have). The really interesting thing in those concrete horns is not the concrete itself but the finishing surface. I have paid attention that the more “hairy” and granular horn’s surface is that more “interesting” the horn sounds. With a glossy horn sound juts “slips” vs. the “hairy” horn sound “flows”. John Hasquin once taught me to pain horns with structured paint to make them not smooth but abrasive. All his horn made this way. I tried to do the “structured paint” on some of my prototype horns and get very good and very predicable result. I think that the beauty of those concrete horns is in thier structured, abrasive surface that Marc Henri mistakably recognized as the “contribution of material”

slowmotion wrote:

I hope anyone interested in JMLC horns read the last four links,  where Jean-Michell writes about his reasoning for his horn profile.

Yes, Jan, tanks it was interesting. Unfortunately the words means little in this and it is necessary to have both of them with the same drive in order to say anything. Also, only God know how each driver would react to different profile and not different curves would couple with the rooms. This is the biggest problem with horn – no one could say anything and very few people actually had a chance to go over different scenarios and to evaluate what works and what do not. With those horns there are so many variables that nothing is objectively predicable…

slowmotion wrote:

I think the Cogent effort is very interesting, not many people are into making field coil compression drivers these days. I wish them the best of luck.

Probably because to make a permanent magnet of this size would be too expansive? BTW, My personal experience with field-coil was not so thrilling. The field-coil is very popular idea within EBay intelligence and among the drivers droolers but in my room none of them behave interesting (none of them were compression) for bass. At least for bass they all were too soft. I am not saying that the Cogent guys would end up with the same results as I did but I feel that for upperbass a driver should be dry and crispy instead of “soft” and “wet”. The field-coils that I used were too “wet” and were locking some testerone.

slowmotion wrote:

I don't know why they insist on using conical horns , though. In my not so humble opinion conical horns suck. Big time. …

May I ask why? The only problem that I see is the size, that it king of their problem… Unless they would run 70Hz horn with a curve and then it all will go to a toilet.
 

slowmotion wrote:

Regarding horn bandwith, this is of course a subject in where  everyone and his/her grandmother have their own opinion. Personally I think 2,5 to 3 octaves should be reasonable.  But sometimes it isn't.  I have given up on 2-way systems, the compromises are just to great. 4-way systems seems like the most reasonable compromise, at least to me, you may even have to go 5-way. If you are very skilled or very lucky you just might make it with a 3-way.

Exactly!!!

slowmotion wrote:

Just some personal observations based on years of hornbuilding, I should probably mention that most of the horns I build end up in the trash or in the fireplace.

Oh, Jan, shut up! I’m trying to encourage people to "go horns" and even begun to brew a small community of my local Boston guys with horn installations among the local 300W SS idiocy. Then you, show up and discourage the people by disclosing to them the bitter Truth. :-)

The caT

The point of the field coil is to saturate the piss out of the magnetic circuit so that the coil flux does not modulate the motor. Romy, I suspect that your experience of them may be based on an older drivers where saturation was not the name of the game; I would expect a proper saturated motor to lean more to the sonic characteristics you're after.

In theory, you could achieve much the same result with alnico (a la ALE, Lowther PM4) or neodymium but there may be something more to the field coil approach. The Cogent boys are convinced of the superiority of the FC approach; they are not about saving money, rather, creating the best driver they know how. Hence the proposed use of permendur polepieces.
 
It would probably be *much* cheaper to achieve a similar flux with Nd magnet but there is probably more to it than that. I know Guy has some experience of the AudioNote FC MC cartridge and will hopefully chime in here.

Cheers

cv wrote:

The point of the field coil is to saturate the piss out of the magnetic circuit so that the coil flux does not modulate the motor. Romy, I suspect that your experience of them may be based on an older drivers where saturation was not the name of the game; I would expect a proper saturated motor to lean more to the sonic characteristics you're after.

Probably. I have experimented with vintage 8-14 inchers.  None of them were contemporary design.

cv wrote:

It would probably be *much* cheaper to achieve a similar flux with Nd magnet but there is probably more to it than that. I know Guy has some experience of the AudioNote FC MC cartridge and will hopefully chime in here.

Yes, Peter told me about his new venture. It is still remains to be seen if it will be a FC MC cartridge or it will be a new Peter Qvortrup “nice on paper” marketing Vaseline wrapped around the story how he used the magnetic force of Erath to aroused the spirit of the Furtwangler’s recordings… :-)

The caT

guy sergeant wrote:

Having said that I've never heard a properly working WE555 or 594 either and given the problems of getting the S2 to work well I can't imagine there are many installations using those drivers with the right sort of horns to get a really good result anyway.

Quite correct observation. There is a lot of myths about the uniqueness and beauty of some older drivers: WE, Vitavox, Telefunken, Klangfilm, Goodman’s and many-many others but the interesting fact the all those conversations about the “superior vintage technique” NEVER got transformed into the really interesting sound in listening room. In fact, all installations that I head that were excessively based on what the “vintage drivers did” sounded like crap. The better sound usually came from a selective using of some selected benefits of some vintage drivers and incorporating of those benefits into own sound reproducing objectives. In the end, a blind use of those Klangfilm and WE always end up with garbage result. An “interesting sound” comes only form a will of a system creator and from the intentions of the systems orchestrator. If person knows what she/he wants to build then some chosen opportunities that exist in some vintage drivers would be used as “tools” instead as the “crutches” or “excuses”

guy sergeant wrote:

A friend, whose ears I trust, listened (I urged him to go there) to the Cogent System at the MAF last year and said it was poor which disappointed me. I'd have to say maybe their room acoustics were bad but he said they were reasonably happy with the result they were getting. Time will tell.

You see, Guy, there is another aspect of it. As soon you mention the MAF then you refer to the very specific (audio?) awareness.  Generally that crowd could be characterized as low-class hoodlums with taste of pterodactyl and reference points of “Texas armadillo hunters”. I personally never was at MAF but a friend of my (and his taste I trust) who is one of a leaders of their community told me the that the MAF population is conglomeration of Midwest white trashes who walk from room to room, belching louder then bass horn driven with 400 Krell amplifier and to anticipate form them any interesting views or accomplishments about sound is like an attempt to bult a high performance acoustic system based upon the Radio Shack ingredients. Interesting that he calls those MAF Morons as “bottomfeeders” (his word) that I find is very correct observation. Really, if you look in-depth at the personalities that “in sine” at the MAF then one would make very intriguing overviews … primary about the abortion clinics bombers, guys bashers, blacks-hater and other “low IQ Americans” … who are so deep in the tunnels of own asses that they need a big horn to be able to see the world. I know, that I sound not like an overly stressed “a liberal form Massachusetts” but I do know personally too well a number of MAF’s “spiritual leaders” and it is enough for me to express a strong negative attitude toward all that Midwest Audiofest. Certainly I would not associate the Cogent boys with my overview above (I do not know them personally) but the fact they so much spin around the MAF idiots made me wonder what the hell they do in there….

guy sergeant wrote:

I'd love to have a pair of S2's spare that I could put field coils into. Having seen Mike Harvey's cut-away S2 I'm sure it could be done.

I had in past those thoughts, however I was not thinking about the field coils but rather to invert the driver and use the new larger tunnels enabling it to go down to 100Hz. I was thinking to talk to Mike and to order a pair of custom durable and heavier coils with thicker weir and a dropped resonance frequency. Then I realized that I would like to have a t least 5-6” diaphragm and there was some other S2 limitation that would make it not perfect for that project. Perhaps I should find another driver to torture. There are none that I know worth to excrement… The only driver that I was thinking to torture and to rebuild was Community M4 but I never when to it since I discovered the Studio 8M

The Cat

cv wrote:

Note also the correlation between MC stepup sonics and size - I gather the Expressive Tech units are on massive cores...

Nope, they are not. The Expressive MC transformers  (the actulal transformers) are very small. I have seen the raw transformers from ET1 and ET2 and it was very “insulting” for the ego of those huge boxes. :-)

cv wrote:

Likewise, I've read a couple of comments where people have heard the S2 and 555 and preferred the Brit. Not sure there's many of the field coil crowd who've heard what the S2 can do...

CV, make an experiment: find some WE droolers and interview them about music and the reasons why they selected his/her 555. I did it. If you do it you will have very interesting observations about thier eBay-inspired intelligence and about their crow-driven motivation. I personally do not find in 555 anything interesting at all but I love how the 555 users push out themselves the bogus reasons and motivation that encourage them to use this driver.

The Cat