Romy,

Could you clarify : Would you like to vent the rear chamber or increase its volume (or both)?

jd*

PS : This weekend I will try listening with the rear covers on the Lower-Mids slightly open... I have to admit, I'm a bit nervous about high-passing the S2 much lower than 700Hz at 6dB/octave.

jessie.dazzle wrote:

Could you clarify: Would you like to vent the rear chamber or increase its volume (or both)? This weekend I will try listening with the rear covers on the Lower-Mids slightly open...

Good question. I do not really know what to answer. I know what I would like to accomplish but I do not know how it should be called.

Conceptually I would like it to have a whole in the back chamber but the whole should be like it covered by a material with variable acoustic transparency: from completely none-transparent to very transparent. My presumption is that if I will be able to introduce a managed and precise drift of pressure from the back chamber then it will be near identical to the increase the back chamber its volume. In fact the managed drift might be even more beneficial (I presume) as it will increase it’s effectiveness with increase of volume of signal.

Sure, it is just hypothetic but when this weekend you will be playing with adjusting the size of the crack on your Lower-Mids you might hear what I would like to accomplish. BTW, share your thoughts if you do not like it and do not forget that you will loose a couple dBs of output .

jessie.dazzle wrote:

I have to admit, I'm a bit nervous about high-passing the S2 much lower than 700Hz at 6dB/octave.

It is exactly what I’m wondering. The 500-600Hz with second order does fine. Where would be the first order equivalent? This question consists off:

1) How much power the driver will be able to handle. From one side the aluminum cones ten to crack, from another side I drive it with no power: ½ 6C33C and ~14dB divider. I have no answer to it but I hear some dangers sonic effects when I drove the driver with 450Hz first order (25uF)

2) How much LF extension do I actually NEED from my Fundamental Channel? I mean where the quality of the Fundamentals Channel begin to be better or worse in relation to the Upperbass charnel? I would like do not finalize my judgment at this point as currently I have one dedicated Milq Channel driving both Macondo’s Fundamentals and Upperbass Channel. I presume that in a few weeks whwn I go one Macondo Channel to one Melquiades Channel then I will eliminate the S2’s and Fane’s coils talk to each other, not to mention getting rig the  speakers level filter from Lover MF Channel. When I do fully bi-amp then I will review the actual sound from both channels. Yep, it would like to have at that time the opportunity to play with the pressure drift/leak from the S2’s back chamber…

Thanks, Jessie. I just will buy that Beswick Engineering valve, it looks like it is the right size and it look like it will do what I need

I made some experiments applying large gaskets to cover of the back chamber. I used a gaskets up to 12 mm but I did not detect that it impacted sound in the right direction. In fact the maximum chamber size that I was able to get with gasket sounded virtually identical is the default Vitavox chamber size. A 1-2mm crack into back chamber, however, made all different. I will be very enthusiastic to hear your feedback when you try it with your 180Hz horn. The 700Hz first order or the 450-500Hz second order will do, though I do not know if you will be able to stress enough the bottom response of that horn with S2 driver.

As I told, I am as now undecided about the benefits of the S2’s back chamber leaking for the Fundamental Channel. The sound is unquestionably and uncontestable “cleaner” but there are a lot of other things that I would like to consider. For whatever reason that cleaner sound from Fundamental Channel creates overly-necessary “directivity” in sound. The defaultly-damped S2 has it its bottom knee a minor touch of nozzleless, it sounds if it “chough a cold”, it has that hazy, smoky vale that sets an atmosphere of “noble mysticism”. It might have overwhelming amount of measurable distortions but at the same time that refined, superbly articulate and very intelligently-dosed nozzleless, in contacts of proper mixing with the rest of Macondo, can do some tricks, even purely Audio tricks, that are hardly imaginable with others drivers or topologies.

For instants I like set the Fundamental Channel (if recordings allowed of course) that the sound of violin sections are handled by Macondo MF directionally but the sound of English horns, flutes, oboes (if the playing of the give piece and orchestra intended to) is completely  non-directional. A properly set up Macondo, while maintaining extremely strong and very precise imaging for entire orchestra can throw horns or flutes from nowhere, almost like it is out of phase, coming from everywhere, and then, if the players/conductor willing to, then it capable to set the horns at the very precise position right where they should be for a given recording. What I detected that “leaked S2” driver has much cleaner, much much much cleaner sound but it doesn't have that foggy capacity to sound like it come from “nowhere”. It is too directional and too “straight”…

This subject is required more experiments, but to catch that fish would require a clean pond… The electricity now is so bad that it is okay to listening music but it is virtually impossible to do Audio. So, I would propone my further experiments for later, preferably when six-channel-Milq will be up and running, or perhaps you will come up with further observations.

OK, I am too lazy to run any curves on this, but is that the range of "bleed-off" you want for music?

As I understand it, the [R.] Goldberg Variation screws this thing in and out "really fast" along with the music in order to adjust/compensate for pressure differences?

Would the servo/stepper know the difference between complex material and volume changes?

If this actually "works", you absolutely MUST patent it!

In fact, it looks so good on paper that you should patent and sell it anyway!

Best regards,
Paul S

Hm, very different and very opposite result, interesting. Are you using the same S2 diaphragm as I do – the metal suspension? If yes then it would be the only one explanation that I might come up with.

Sometime the compression drivers with horn form a very subtle and very bizarre combination when the horn’s throat reactance damps the cone (along with it it’s back chamber) but not juts damps but does it in hipper critical mode when any minute deviation of the loading (like changing the bag-screens density) immediately threw the cone’s damping in one or another extremes. I personally never had it in such a sever care as I have it now but I heard that it might happen and to be VERY notable.

Vitavox did in 180Hz, 220Hz, 300Hz and 330Hz horns, all exponential. We know how S2 behaves in 330Hz – it was made for S2 driver. Interesting that neither Vitavox not any another company that I might recall as not ever did 250Hz hors. Altec did 329A and 311 horns that were 220Hz. The JBL did the same: 220Hz and 300Hz – never 250Hz, at least that I know off. Sure it would not indicate anything, as the balance between the specific driver and the horn size (mass if air in the horn’s belly) is the key. Still, it is juts data…

So, I might presume that at 250Hz and the metal suspended S2 I accidentally hit the “G-spot” of the horn-driver tandem, I am sure that if I measure the driver’s impedance then it will jump like a rollercoaster. Continuing the hypnotizing…. When you went for 180Hz horn you with air in that horn was way beyond the “dangers air-mass” and therefore you did not experience problems. If my hypnotizes is true then I might cure what I have by changing the pressure from back or the front of the cone and then trying to load the driver lower, to see it is will be able to handle it. In fact the leaking of the back chamber is one of those attempts … The sonic differences that I getting is not minor and very easily auditable….

I think if my hypnotize is true then that accidental hyper-fragile equidistant between the cone’ back damping, specific horn size and throat resistance deserved to be named. I propose to call it the “Horn’s Bermuda Triangle”….

I am not quite sure what is going on but wherever is going on is wrong. I was listening this morning Shostakovich’s second cello concerto by Berlin and Rostropovich and I detected that something was not right. It was too direct and “too stereo”, if I might say so. It has no of that smoky sound that is almost mandatory for any cello concerto. The Rostropovich was too prominent, not imaging- or volume-wise but the contrast-wise, it did not make sense…

I decided to close up the back chambers in my Fundamental Channels. It was interesting result. The hi-fi-quality of the recording move down, the articulation of the cello become slightly murkier and the Berlin Philharmonic’s Sound got more ambient and creamier but at the same time the entire play got more sensible, more united.  The lower midrange region become not “too sexy” but instead more dissolves in the rest of the music.

Go figure… I deseeded to close up the S2 back chamber for now and to put any further experiments on hold…

jessie.dazzle wrote:

Once I am done with more of this project, I will make a 330Hz Tractrix to try in place of the upper mid 400Hz.

Hm, I wonder what would be the purpose to make 330Hz horn for you if you have 400Hz and a dedicated lower MF channel? The only reason to do it would be the fact that you experience specific problems with lower knee of your MF channel, do you?  If you are persuaded by the fact the Vitavox did 330Hz horn to use with S2 then be advised that the same Vitavox systems that uses S2 sometimes were equipped with 220Hz “harrow” horns.

Still, I think it absolutely unnecessary for YOU to look at what Vitavox did. All their design with S2 driver were two ways systems and you are, dividing the S2 ranghe to HF and LF, are in way more advanced situation.

I think the 400Hz was a good chose. Let see what changed will be if you go for 330Hz instead of 400Hz? You will be able to driver your MF little harder at it’s bottom - do you need it if you have own Lower MF channel? You also will loose very slightly top end of your MF driver and will have more narrow MF radiation patter. Also, you will have ~60mm larger horn that will make the entire height of your frame’s horns taller. Sure, nothing wrong to make another horn and to experiment if it is easy for you but I would persuade you to use only your tangible sonic motivations to navigate yourself instead juts blindly looking at what Vitavox did.

I did a lot of those experiments a few years back, stuffing the back chamber of S2 driver with all imaginable things. During that time I did not use a dedicated lower MF channels and was concerned only about the S2 top end. I did not detect any difference in sound, as lease in the area that I was interesting. I might presume that for lover MF the back chamber stuffing might be way more interesting direction to explore.

Still the results of the back chamber stuffing most likely will be correlateable only when the drivers are loaded in identical horn (the same throat reactance). What the chamber stuffing does? Depending of the type of the stuffing it might virtually increase of decrease the size of the chamber, driving primary resonance up or down. I presume that when S2 was made they made (if they ever did it intentionally) the chamber to damp the 330Hz exponential. The volume of air in 330Hz exponential probably is the same as 220Hz tratrix, I do not know the exact numbers, however…

…however, the air’s volume rational might be is very erroneous way to view the things as Vitivox used bogus profile horns, primary stolen from Altec and Klipsch. Therefore, in reality I would not be surprised if they never even thought seriously what they did and juts went for the profile/size of the horn that just would fit the size of their cabinets.

I think all that S2 loading sage should be completely reviewed by us. Nowdays, using S2 driver in our home installations and with contemporary playback demands we are getting from those drivers so much more then they initially intended of imagined that any “default” Vitavox intentions should not be under any attention.

With 6-chenals installation using the S2 drivers we are not in Kansans anymore…

jessie.dazzle wrote:

I've been listening for about one week now with the filters set so the hand off from lower-mid to upper-mid happens higher up (upper-mid S2 is high-passed at 4800Hz instead of 3200Hz), meaning the small 400Hz horn is doing only the upper "half" of the mid range. I left the 180Hz horn as it was (790-3200Hz)…. I have not measured the output (too many other things to finish). I don't know exactly where the acoustic transition is happening, or if I am leaving a range uncovered. The point is, that the difference is such that I don't need to measure anything to be sure that this is better than when I had the upper-mid horn high-passed (electronically) lower down, at 3200Hz. I was most likely getting some overlap in the crossover region between the two horns (I don't attenuate the 180Hz "Fundamentals Channel", or any other channels). So the 180Hz horn is currently handling two octaves (electronically), the 400Hz horn is also now handling only two octaves (electronically)... I like what I hear well enough to not ask these horns to do more than this. If measurement reveals an uncovered zone between the two, I would rather add another horn than to ask more of the existing horns...

Romy wrote :

"...It is most likely that you changing the yours crossover to 4800Hz introduced a phase shift that accidentally “clicked” with the neighboring channels...You might look at the differences in imaging since you changed the crossover..."

Hmm, interesting... The horns are not yet properly located (frames under construction)... in fact they are only sort of close, and at this stage, the L and R channels are not really symmetrical, so I tend to not focus on imaging; even so, I have not noted any differences in imaging with the new arrangement.

Here are some specific observations made with the 400Hz horn high-passed higher up (at 4800, versus 3200Hz):

1) I now use a higher volume setting on the preamp

2) "Cringe factor" has gone down... This simply means that I don't find myself reaching for the volume knob to turn down violin, horn, and upper range vocals passages which are less than absolutely perfectly recorded

3) Due to the higher volume setting, for what seems like the same mid-range output, there is now more output from the bass drivers

4) Overall the sound is now less thin and I would say "warmer"

As you have mentioned in the past, and as I have confirmed with RTA, the 400Hz horn, when high-passed at 3200Hz, is good acoustically down to about 1kHz. I now need to measure the output from the 180Hz horn, but in its current band-passed configuration (790-3200Hz), it will certainly produce sound well above 1KHz, the point where the 400Hz horn was coming on. I was for sure getting ouput from both horns in the 1-3k range, and it is possible that the 180Hz horn alone produces better results in this range (say 1KHz-2KHz) than if accompanied by the 400Hz horn.

As you pointed out, moving the high-pass point up from 3200 to 4800 is only a 1600Hz difference, but what if we look at it in terms of octaves we are asking the S2 to reproduce:

High-passing at 3200 means the S2 in the 400Hz horn will be asked to handle a full two octaves (electronically) :
Octave 1 : 3200 + 3200 = 6400, and Octave 2: 6400 + 6400 = 12800 (where a good S2 will naturally roll off)

High-passing at 4800 means the S2 in the 400Hz horn will be asked to handle only one octave (electronically) :
4800 + 4800 = 9600, plus a bit more above that, until natural roll off of the S2

I'm not sure that means much... I will try to take some measurements soon.

jd*

Very interesting.  I appreciate that you have exposed more of your listening sensations  - that give more objective information, letting to propose more accurately what might took place. In regard to what you say it might not be the “phase clicking” but rather a mild decompression of the upper range S2.

The S2 crossed at 3200Hz at 6dB and pushing in a 400Hz horn 1000hz of air does reaches at it’s bottom the region where a very slight touch of the “Horn Boom” takes place. It is a mild form of honk, very modest and very much not detectable when the channel is supplemented with sub 1000Hz channel.  It is possible that moving the crossover point from 3200Hz to 4800Hz you further up removed the S2 from the Horn Boom region.  (The Horn Boom is always accompany with compression)

I did experimented with it and not detect that moving up the crossover point was a benefit. However, when I did those experiments (2001-2002) I did not use yet use a Fundamental Channel. So, during that time I was merging the S2 driver with my upperbass horn’ upper knee, which had too heavy cone to care 2000Hz. The lower friqency S2 driver should be way more interesting contestant….

Presumably you discovered an effect that worth to imitate or at least to try. Do you have the vertical image shift slightly up when you change your crossover point higher? Anyhow, let see what will be your further finding or perhaps the final findings. However, there are few things that would strongly encourage you to check before make up your mind, all of them are related to the S2 driver in 400Hz horn

1) Make sure that your cone is properly center in a gap. It is very important as misaligned cone will do compression at bottom end