Here is the list of the thing to do with Vitavox S2 in order to use it in 4-ways installations. The S2 must not be used in 2, 3 ways systems. It possible to do with S2 whatever you wish but pretty much any other way to utilize them produces some very specific sonic negative manifestations that I very much might name.
1) After you get your S2, form whatever junk yard you got it, you should inspect it and to confirm that the magnets are fully charged. I usually do not stress the compression drivers by driving them with 2.38V. I have plenty of know sensitively drivers to make a comparing judgment. However, the most comfortable way is to "measure the both of the drivers and to assure that they produce the acoustic pressure equally within .25dB at 5Khz. (do not use 1Kz with S2, there are reasons for it). It is highly unlikely that both of the drivers would be discharged equally. It is very seldom that S2 would be discharged by electrical force of DC component but mostly it might happen then it experienced a mechanical or temperature stress. If a driver is discharged then charge it at the Vitavox’s Mike’s place.
2) Peace an order to your horn-maker to manufacture for you a pair of a 550Hz tatrix round horns from as soft/damped wood as you will be able to get. Give to the horn-maker VERY precise diameter of the throat. No adapters from another size throat should be used.
3) Remove the front bag-screens (3 small bolts), clean them up and put them back. Do not remove the bag-screens permanently as the bag-screen MUST be there. Besides performing very important acoustic diffuser role the bag-screens create a front-loading contra-pressure the diaphragm and participate on acoustic dumping. If you find that the compression drivers (and particularly S2!!!) sound better without the bag-screen then you have to trash or your electronics or your ears or your listening taste.
4) Remove six bolts on the back of the driver and take out the back plates.
5) Un-solder the diaphragm’s leads by a low wattage solder, remove the diaphragms, the diaphragm’s plates and the gaskets.
6) Inspect the diaphragm. There is 99.99% that you have an aluminum diaphragm with metal surrounding, that is the original Vitavox diaphragm (they actually had 3 different types of the diaphragms). If you have no aluminum diaphragm with WHITE PLASTIC SURROUND (not clear transparent, metal or milk but white plastic with litz round, not flat, wires) then trash you diaphragms. Order a set of NEW production diaphragm from the Vitavox’s Mike. His contemporary production is WAY more interesting sounding then the original old diaphragm. If you feel that to waste another few hundred dollars to this project is too much then you then have two options:
A) Do not read further on and, concluding that Romy the Cat is idiot, to continue to use the S2 “as is”
B) Get yourself some JBLs, Altecs, TADs or the similar toys: the Vitavox is way above your handling abilities and sonic ambitions.
I personally never was able to get a result that I would consider sonically satisfying from the original fully metal diaphragms. If you see me sealing the “fully-metal” diaphragms on eBay and claming that they are the best because they are “original” then just smile….
7) Unscrew the binding posts and clan the surface under the bottom. Your driver is 50 years old and you have to remove all dirt and the possible cockroach’s legs in there. The binding posts transmit signal via a physical contact to the soldering plates, they are not soldered. You want to make the contact surfaces clean and preferably treat it with any know to you de-oxidizer and contact cleaner/conditioner. Tight the binding post’s nuts quite strongly. If you on one of those idiots who tight the big and heavy cables from amps to the binding posts with those heavy-duty tools (I am) then be advised that those binding post’s nuts will hold the moment of the tightening. If your binding post is slightly turning then disassemble everything (primary because it will not be a secure contact (pass) for the signal) and tight the nuts again (and at the moment it will be a lot of affords invested into the S2, read on)
8) Clean the S2’s gap. Many people have different ways to clan the gap but old-good mask tape will do. It might be quite tedious. I will not elaborate on it as all percussion and warnings about the gap cleaning are well known. I would only recommend before cleaning the gap to mask out the entire back palate of the driver and collect on the making tape all dirt that will be dropped there from everything. The gap is never could be too clan and I strongly encouraged to over-clean it.
9) When you get the new Mike’s diaphragms install them into the driver according to the his/Vitavox instructions.
10) Place the diaphragm’s palates and screw the palate’s 6 bolts into thier slots. Screw very gently those bolts; the order is not important but DO NOT TIGHT THEM now.
11) Now you have to tune the driver and it might be complicated. The tightness of those six bolts will HUGELY affect the performance of the driver. In many instances the 5-degree of one of the bolts will distinct the sound of your drive from bad to good. By aligning the diaphragms you will accomplish 2 things:
A) Center the coil in the gap and make it do not scratch the walls) or do not touch the junk that you left in there)
B) Tune the driver sonically, even if it is has been already properly aligned.
12) To accomplish the 11A is relatively simple. Many people use different methods: distortions analyzer, high voltage full-driver-range frequency sweep, RTA with maximum response around 600-900 amplitude, injection a signal into the secondary resonance and so on. Use whatever method you want but your driver should not have any alien sounds during a sweep. To work with 6 bolts alignment is relatively complex. Use 2 opposite bolts to start and when you reach a perfect result for 2 opposite bolts then add the forces of the rest 4 bolts by tightening them in X-order.
13) To accomplish the 11B is relatively difficult. The RTA will not help even if you have a reference sweep from another driver at 0.1 dB resolutions. The problem is that a very minute tightening of those bolts will still maintain the driver in a perfect “11A state” but will quite auditably affect harmonics and obertones, or the “11B state”. The distortions analyzer is very valuable tool but I learned that the best sound I was able to get NOT at the lowest distortions measurable level, not to mention the it is very difficult to fix the diaphragm’s plate at the mathematically best position (remember your have 6 damn bolts in there to screw but just one life). I tune the diaphragms at the 11B level by a hearing, Take a good contralto singer, connect the amp to a driver with it’s opened back plate, pace the driver on the table with a hole to let sound to go out and play music (I accustomed to do it by playing Polish singer Eva Podles singing the Stravinsky’s Oedipus Rex). It will sound for a beginning kind of st
range but soon you will figure out Sound and will be able to detect the relationship between the few degree of the bolts turns and the sonic result. The more LF harmonics you get the best it will be (it will open also a lot of HF). It is possible that you will screw up the 11A setting but it is not important, as when the coil will be properly alighted at 11B then it will be automatically properly set in11A. You may abandon the aligning at 11A but it you want to get all S2’s “kinkiness” while it will be handle the crescendo of the string group during the second movement of the Tchaikovsky 5th symphony or a dynamic attack of a good soprano then better to suffer now then later. The 11B alignment works strange: some of the drivers could be tuned within a few minutes and I have seen some S2 that I was not make sound good at (11B level) for weeks. Go figure!
14) Remember the final tuning can’t be archived but only escaped or abandoned. Somewhere during this process you should find a peace with yourself (remember you have 6 damn bolts!!!). You have to approach the ceremony of tuning being in a very comforting mood. It is very similar to alighting TT’s cartridge, did you try to do cartridge when you pissed or not completely calmed? You got the message….
15) When you finish with the 11B then place the back plate and not you are ready to move further.
16) Get your new 550Hz horn and screw the driver in. Do not use the 330Hz horns as you loose HF, dissipation, useful upper mid rage resonanses, closeness of positioning a tweeter (larger horn) and few another things.
17) Place the horn in wherever system you intend to use it. Align the diaphragms of your upper bass channel and the S2. I usually do the alignment by connecting the channels in opposite phases, applying the 1KH tone after the crossovers (look lower about the crossovers) and move the horns until the maximum analyzer’s cancellation will be observed.
18) I will talk about the crossovering in context of passive speaker level crossover. IU will do it order not to go into the diversity of line-level, feedback- level or any other crossovers you might employ. Convert my comment into whatever crossovering scenario you use. If you decided to use S2 then I presume that you are not a complete moron. There are a few other conditions of being none-moron, namely: no use any digital crossovers, no higher order filtration for MF then first, no Zobels, no impedance equalization, no resonant filters, no notching and no any other idiocy. So….
19) Let the upper-bass channel to roll of ~ 1000Hz with first order. The precision of the upper-bass low pass crossover point might fluctuate upon few parameters (driver, topology and many others) but usually it will be around 800Hz -and 1200Hz. I presume that your upper-bass driver was property selected for the “correct” integration and a proper “1 order penetration”. Use whatever evaluation method you know to make sure that you use a correct upper bass driver. (A tip: make sure that the upper bass driver sound good at 3-4octaves of it’s low –pass crossover point)
20) The Vitavox S2 has primary resonance somewhere around 400Hz and the secondary at 1250Hz. Here is the S2 response in the standard Vitavox 330Hz horn
As you see it is a freaking rollercoaster and the secondary resonance is screwing everything very dramatically. Interesting that in this picture the 109dB sensitively corresponds to 74.5 dB of reference point. Whatever happens between the 400 and 2,5 is pretty much unnecessary for you garbage. So, get any known to you soft capacitor of 3uF and place it in series with the S2 driver. This will introduce to 15 Ohm of the S2’s load a first order slop starting approximately at 3,500Hz. The beauty of this cap that is quite nicely snatched all wildness of the ugly secondary resonance. Ironically, it also slightly boosts HF and “accidentally” progressively flattens the response to the place where the roll off of the horn kicks in. Here what you get with the 3uf cap. (Disregard that it is measured at the different reference volume)
21) Now you may listen your S2. Completely disregards that fact that it runs to 10-11KHz only. At this time you can hear what S2 does and why it’s upper mid is totally different then any another driver. Do not be in hurry to peace a tweeter in there and spend some tome to listen it “as is”.
22) If (a REALLY BIG “IF”) you have very obligating amplifications, very “honest” cables and generally your installation and your listening preference have high demands then you might detect some idiosyncrasy of S2 at its HF. I intentionally do not name those idiosyncrasies and I do not want to plant the placebo into the process. Now you might search for a tweeter. However, this tweeter should not inject measurable sound above the S2. Find a tweeter that you believe has the same sonic attributes that S2 has (use whatever evaluation and assessment methods you find necessary to use). Alight the diaphragms, use of course a first order and inject into a listening space a sound from the tweeter at ~15kHz and minus 12dB. Slowly increase the output of the tweeter by ½ db until suddenly the S2’s idiosyncrasy will be gone. If you run .25 dB resolution of your TRA and if you see that the tweeter output have rise over the S2 roll off then your tweeter it too hot. The complete “fixing” of the S2 will happen approximately form minus 10 to minus 6 dB at ~15kHz or when the tweeter’s output begin to intricately modulate/resonance with the S2’s HF slope.
Now, your S2 is “cooked” and you may listen what it dose “full time”. Do not be bothered that it looks on the paper that it dose not go up enough. The quality of HF that you have now is not even remotely approachable by any other driver/s or any other method of sound reproduction. I assure you that if you do not look at the response curve and do not show it to your friends than no one, even in their sickest imagination would complain about “not enough HF extension”. The MF-HF superiority, nobility, alacrity, transient response, musicality, handling dynamic contrast and tonal discrimination that you got now form your “helped” Vitavox S2 driver should make you forget about existence of any doubts to reproduce MF-HF and should make you entitled to show a big middle finger to any another compression driver. You may spend some time to work on your horn if you wish (damping and mass-loading never hurt) but regarding everything else about the MF-HF: your “hobby” is over. Welcome to the REAL S2 club.
Romy the Cat
PS: this is what I have now at the top of my mind. Possibly I missed something then I will add it later on.
Added March 2005: Please read the thread to the end as some of the my view about the use S2 have changed since I've written this article.
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche