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Posted by Romy the Cat on
07-12-2007
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We, the horn people, know what the compression drivers could do. The controlled dispersion, low distortions, low mechanical dependency, low magnetic anomalies, high efficiency, higher maximum dynamics and many-many more advance are well known. The term “compression driver” is kind of bogus as we do not rely from compression anymore but it is the only name that we have. The most remarkable part in the compression drivers is how they response to crescendos or to any increase in volume. Compression drivers have insultingly linear increase of intensity with constantly-present extra pool of dynamic headroom. It is very hard to make a good compression driver properly driven and properly used to hit a point where it stop gain volume and begin to compress. Well, where did you see a properly driven compression driver?
This is the subject that I would like to talk about: the compression drivers do not compress and do not dive into the typical “hardness” only if they driven by a “clean signal”. If the signal is “clean” then a compression driver is not stressed by anything – very seldom happen. Unfortunately the industry (and the compression drivers are unlucky, as their industry is pro audio industry) do not investigate or invest into “clean signal” but rather they make the compression drivers less sensitive to the “dirty signals”. All those JBL’s aquaplass cone treatments, increase the compression ratio to 10:1 or 20:1, making barbarian suspensions, use electromagnets (it might be controversial), employing of none-reactive cones and many other “solutions” do mask out the reactance of the drivers to the “dirty signal” but along with it they weaken the sonic characteristics of the drivers, “denobleize” the driver’s Absolute Tone ™ and reduce the driver’s transient capacity.
So, what make a signal “clean” and what would not stress the high vulnerability of a fragile, low power, good compression driver? I would not look at internal characteristics of the compression drivers: magnets, diaphragms, suspensions and many other and will look only at the external variables. Without pretending for the complicity of the answers here are my runners:
1) Bad electricity (bid subject!!!)
2) Presents in signal path of any direct or indirect phase constructors.
3) Presents, position within the chain and type of capacitors in signal path.
4) Quality of grounds
5) Having <18dB in signal’s dynamic headroom
When those 5 reasons are optimized then a compression driver has opportunity to demonstrate the max capacity of its design. So, in many cases: do not blame the compression drivers and if the fish begin to die in your pound then look up the river for the reasons that poison the pond’s water… Rgs, Romy the Cat
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Posted by Markus on
07-12-2007
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Hi Romy,
I usually manage to read you quite well, but this
 Romy the Cat wrote: | direct or indirect phase constructors. |
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has me baffled. What do you mean, please?
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Posted by Romy the Cat on
07-12-2007
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| Markus wrote: | I usually manage to read you quite well, but this
 Romy the Cat wrote: |
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direct or indirect phase constructors. | |
has me baffled. What do you mean, please? |
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When I wrote it I meant different wave constructors: phase splitters and phase summizing nodes. I am very much not fancy myself as some kind circuits specialist, and have very rudimental knowledge on the subject. I never had interest or motivations to figure out how it all works in relation to the actual sound. However, I did try a great number of PP amplifiers to drive better drivers and I observed is that the wave reconstructing amps are not usable with compression drivers. I might only presume that PP amplifiers very minutely spoil sound with asymmetrical reconstruction of the waves, and it would be due to practical impossibility to make absolutely identical halves of the PP amplifiers. Any single PP amplifier that I have experienced, when they drove a compression driver, injected into transients some very strange atonal mud. It is like you painting a picture and while you do it someone are adding white color in all your paints, and are replacing your brushes with the brushes of the much larger size, although you continue to use your brushes as they were small.
I have to admit that the said about this true only in context of “good” compression drivers. A good compression driver is a driver that has a consequential reaction to the “clean” signal. Since the drivers that I am experienced are only Mid frequency compression drivers then I would without any hesitation state that good compression drivers employ ALNICO magnets. The Samarium Cobalt, Neodymium, injection and electromagnets are a different subject and they might have own place but they are not well explored by me in reference to Actual Sound. The Ferrite or the Ceramic – the most commonly used nowadays materials, are absolutely not usable in context of MF compression drivers. In order any HF/MF Ceramic driver to be able to give away anything remotely resembling to Sound the driver should be driven with enormous amount power that, in own turn, has many other negative Sonic consequences.
So, in the end, in my warm world I see at high frequency compression driver as an ALNICO-centric driver with amplification that amplifiers THE WHOLE SIGNAL ONCE AS A WHOLE, without any tricks, the way how it is done in single-ended triode amps. Saying it I do not demonstrate a loyalty to a specific topology but rather I just report my past disability to get the desirable sound from compression drivers using other type amplification.
Rgs, Romy the caT
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Posted by TerryG on
07-13-2007
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Hi Romy,
Your the first person that I have seen that seems to have actually made PP tube amps work with compression horn drivers. It has been my experience that PP amps don't like the low watt operating range. I supose it all is a matter of the splitting and recombining of the AC signal, along with the careful matching of the tube pair. The thing about any tube amp is that just because you have any specific amplifier doesn't mean your getting the same results of the guy next door, because they are so component dependant. You can have the same brand of tubes, but even tube to tube the sound can change within the same brand. I see potential for PP tube amplifiers, but I have never thought them a canidate for horns.
Terry
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Posted by TerryG on
07-13-2007
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Sorry I misread, I thought you endorsed the use of PP tube amps with compression horn drivers. Well it looks like were still in the same situation of not making them work. I could go on about why I feel they don't work, but it won't change anything helping anyone create a PP amp that will. I believe PP amps can sound good with some speakers simply because you get the crossover distortion low enough in signal to noise ratio sort of way that it is no longer as huge an issue, but then those same amplifers almost always have issues with higher frequencies.
Terry
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Posted by Paul S on
07-13-2007
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Terry, are we reading the same posts, here? I am given to understand from the foregoing that the general idea (a la Ockham/Einstein) is to keep it as simple as possible unless and until greater complexity is audibly justified, and that one of the great things about narrow-band HE is just that it rewards the simpler circuit, ie,  SET, and specifically not PP.
Of course all these idea can and should be put to the test. While I presently use a wide-range driver for MF, and FR amps to drive the whole shebang, my own listening to date confirms the audible merits of the basic ideas put forth in this and related threads. There are other ways to go for +/- acceptable compromises; but at this time, as far as SOTA is concerned, it looks like this is Harvey R's One Way Way, and so plainly so that it inspires in me incredulity that more rich nutbags aren't onto this, especially since so much time and money is being spent on outright junk, even as this is written and posted.
10/4, the generic tube info, although I don't get how it applies here.
Best regards,
Paul S
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Posted by Romy the Cat on
07-13-2007
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Terry,
I did found that PP amps were good to drive BAD compression drivers (with ceramic magnets). The irony was that the better amps to drive the ceramic magnet were not just the PP amps but the solid state PP amps. Do not ask me why – I do not know why.
Still, with the use of the average better compression drivers (let for a sake of reference point consider the JBL 2440 as a reference “average compression drivers”) there is nothing that could be less “clean” then SET.
BTW, I’m not a big fun of OTL because their very fraudulent harmonics, but I might only presume that if someone would wind very high impedance, still light, voice coil and make the OTLs do not drive DC then OTL might be a good candidate to try defeating the SETs… Still, something is VERY special "lives" sonically in the core of the SET’s transformers…..
The caT
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Posted by Paul S on
07-13-2007
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I haven't given it a lot of thought other than to note the irony that there are quite a few dedicated OTL people who use autoformers ahead of their speakers. In fact, I think there is fairly brisk underground traffic in autoformers for this use. I have heard several OTLs sounding very "clean", but also pretty bleached out, struggling with their loads, but I have never heard OTLs improved with auto formers.
Now I am wondering: If we go to such trouble to have transformers wound for our particular applications, maybe we could just as well be winding our narrow band voice coils and welding them to our/their own output tubes.
I don't know why, but something like this sticks in my head and responds to the idea of "dedicated amp", and it also re-surfaces when I think of old "theater horns" (may God rest and keep them...).
Best regards,
Paul S
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Posted by Romy the Cat on
07-14-2007
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| Paul S wrote: | | Now I am wondering: If we go to such trouble to have transformers wound for our particular applications, maybe we could just as well be winding our narrow band voice coils and welding them to our/their own output tubes. |
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Isn’t is what some elescrostas do coupling their transducers directly to the plates of some high voltage transmitting tubes? I do not think that we have this option in compression drivers as compression drivers have a very limited voice-coil mass and (derived form a typical ultra-narrow gap design) the voice-coil-heat dissipation problem.
Sure, the OTL are very “clean” and it is imposable to take it from them. It would be interesting to hear more harrow-bandwidth D-OTL (dedicated) with compression drivers. Vincent Brient did something in that direction:
http://vincent.brient.free.fr/otl3w_eng.htm
If I were him I would not go for 6C33C and that tube are crazy in OTL mode. I would rather go for 6C19P that have less power and do not “blow DC“ when it dies (as the 6C33C does). The 6C19P sound muck less interesting in SET mode however
I do not know. I never experimented with OTL idea dedicated to compression drivers, perhaps I should. I always took OTL evaluation in a full range context and it never was successful (people do not know but I had Lamm ML2, Atmasphere and Tenor in the same room)…
Still, as I said there is something interesting lives in the “core” of output transformers. The “core” adds some viscosity and some creaminess to sound, in the same way as the coffee made by excrete of the Palm Civet adds own “allure” to a fry water…. Rgs, Romy the caT
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Posted by cv on
07-14-2007
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Allo
Well this could be very interesting.... the Melq driver (at lower voltage) direct coupled to a 6C33 cathode follower run at low voltage, high current. Vincent looks like he's running about 80V 500mA, though in this case you'd need to use a resistive load rather than aircore choke. Then you'd cap couple to the S2 using the existing Vit Q high pass.
The only issue would be that the Zout of the stage would be about 20 ohms - this may well screw the tailored frequency response you've obtained by deliberate "undersizing" of the cap relative to the acoustic x/o point. Ie the damping of the "secondary" resonance of the plastic diaphragm S2 may be off.
Here's a crazy thought... have you every tried driving the S2 directly from the Placette?! I know the 6E5p does some unique things but I wonder if it might be educational.
The placette has a 7 ohm Zout right? Don't forget that that doesn't translate into current delivery so best stick to low volume...
Cheers
cv
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Posted by Paul S on
07-14-2007
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But I thought the core of the Placette is passive, with a buffered output, no gain?
How could this work at all?
Best regards,
Paul S
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Posted by cv on
07-14-2007
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Hi Paul,
My understanding is that the placette has a unity gain buffer. At full CD ouput levels of 2Vrms into an S2 - it wouldn't quite get that into the S2s 16 ohms - but say it did, you'd be looking at about 109db from a pair...
I'm not saying it would or wouldn't sound good, it's just me being curious given that Melquiades is losing an output stage...
The point is you don't really need any gain from the amp when driving such high sensitivity. You might successfully construct an OTL using just a 6C33 with no other stages... anyway, I'm taking things off-topic for this thread so please excuse me.
Best,cv
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Posted by Paul S on
07-14-2007
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then the idea of amp bypassing is relevant to the "clean signal" discussion. But regardless of the measured voltage out vs. driver sensitivity I suspect that there is too little of something in the way of drive and control between a 2-3 octave compression driver and a pre-amp, let alone a phono stage or CD player with resistors and a unity buffer between the source and the driver. It remains to be seen/heard how much or how little power would really be needed if the circuit were optimized for the driver in question. Back when, and barely relevant, I got perhaps the best overall quality of sound from my VOTTs with 20 wpc PP tubed amps, but they certainly lacked dynamics. Friends with speakers similar to mine liked their little 2A3 and 45 SETs, but to my ears these were not really in the running for FR, and we did not have crossovers or techniques that made multi-amping any good, either. No doubt it can all be done more effectively than we did it, but I just have to scratch my head at 2V from a 12AX7, etc., controlling an an S2 or JBL 2440.
I would like to hear from anyone with recent practical experience on this front, or furthur considerations on the lower limits of power that one needs to get music from the average MF or lower MF compression driver.
Best regards,
Paul S
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Posted by Romy the Cat on
07-15-2007
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| cv wrote: | Here's a crazy thought... have you every tried driving the S2 directly from the Placette?! I know the 6E5p does some unique things but I wonder if it might be educational.
The placette has a 7 ohm Zout right? Don't forget that that doesn't translate into current delivery so best stick to low volume... |
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I did try it a few months back. With a high output front-end driving Placette and the Vitavox directly coupled to the Placette the Vitavox was able to develop a relatively mid volume (not to high though). However, altogether the sound was horrible, it was even further than horrible it was astonishingly revolting – it was pretty much the frequency-fluctuating noise.
Sure, the Placette that did not mean to develop enough currant necessary to drive the Vitavox. During those times I spoke with Guy Hammel, exploring opportunity to bias Placette harder and putting the output transistors on larger radiators. Guy was very willing to go to any directions I would like to, thanks him for that. But eventually, after many considerations, I turned skeptical to the idea of changing my Placette and recognized that it should be built a new, different type of amp to do the duty. I decided do not trouble troubles and let it be as is. If I had another Placette buffers then I might experiment with it, letting it to drive more current, but I did not want to destroy or to compromise what I currently had. Also, there is no assurance that if Placette we'll be driving more current than it would be at transparent/neutral as the current Placette is.
Actually doing is these experiments I come across to a very interesting observation, the observation that I have no explanation. At that time I was truing to drive S2 with anything that outputs voltage. I told in the past that I have SL-600 monitors (which sound superbly with Lamm M1.1) given by 22W Denon mini-system. They do not sound interesting but it is acceptable enough to listen the “Prairie Home Companion”. How big my surprise was when during those experiments suddenly discovered that SL-600 might yield a surprisingly wonderful sound when crappy Denon headphone outputs drived one stage 6E5P, and then via a transformer the SL-600 monitors. So the 6E5P just overrided the SS buffer... I am not kidding the sound was hugely different than the Denon's own, it was truly brow-raising. Surely it was not possible to drive it laud because as soon I overload 6E5P’ grid with voltage (it has only 3.4V of bias) then found dive into a very severe distortions. However, with low voltage on grid the 2.5W 6E5P’s stage did against those sub 50-sensitive loudspeaker some phenomenal sonic pyrotechnics those sub. If someone would tell me about it I would never believe.
I do not know. Perhaps I have developed an addiction to 6E5P. I have no motivations so far to sign into a rehabilitation facility. Now I have to live with it. :-)
Romy the caT
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Posted by Romy the Cat on
02-01-2008
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I was right before but now I really review my rightness for a new perspective. Yes, the compressions drivers are the subject of clean signal but it what I witness with the new 6-chenals DSET put what I said above in another extreme dimension. I do not know what it was: the singe-stage 6E5P driving, the lower intermods, different power supply but the definition of cleanliness of signal move way out there. It moves in such an extreme dimensions that some “sleeping god” issuers with of my Water Drop tweeter become the open issuers.
What the new amp for my compression drivers suggest that there is another level of dynamic (as opposite of static) signal cleanliness. In context of that moving cleanliness the changes with driver sound express a totally superlative level of majestic delicacy when sound moves across frequency and dynamic range. I think it comes from a new v of signal as there was nothing changed in my loudspeakers.
The Cat
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