Coops, I less care about the attacks on me, I know that I am a pH-indicator of Moronity among audio freaks. So, if some specific idiots out there are not happy about me then… it is good for me. The higher we climb in mountains the stronger wind and less frequent chance meeting of pedestrians…

I would like to extend a little my comments about my dissatisfaction with the Gamma’s tweeter. I do not like that way how Gamma’s tweeter thought-out and implemented. Sure, I did not hear the speaker but I do not need to hear it. Let be beyond of agendas and “conditions” and look at the subject of pure facts and also to fulfill out desire to pursue the Oscar Wild’s “simplest principle”: to be satisfied with the best.

I will live aside all other aspect of Gammas and will look only at the way how Gamma implements the top octave. The Gammas uses that ET-703 in custom spherical horn. Gamma put the tweeter at I presume time-aligned position. That is very good but …

The custom spherical horn depicted above is not good “ultimate” horn. Since the ET-703 kicks in that speaker after the TAD 4001 driver I presume that it crossed far-above 10kHz.  Those ultra-high frequencies have very short wavelength and the size of this wavelength approximates the dimension of the tweeter. When it happens, the waves begin to propagate themselves in the areas of geometrical shadows (the diffractions) and the only way deal with it is a complete elimination of rough surfaces (boundaries). Here is where the horn termination with negative opening is mandatory. Similar to what the French Le Cleach does only taking it to extreme. The best profile for UHF horn termination would be a full negative rollback to the whale body shape. Did I mention how a water drops self-adjust own ultimate resistance shape while they are falling in air?

However, the Gamma has no space for a full negative-opened tweeter. Here is the picture that I found in my browser’s cash. The tweeter sits well behind MF driver and has no room for maneuvering. A short HF hone makes the tweeter to have a nice wide radiation diagram but we have a MF horn oppresses it from top, the upperbass horn from bottom (a lot of wasted space between tweeter and upper bass horns) and the sides of the Gamma frame truncate the tweeter’s radiation from left and right (as it sits very deep). The tweeter’s reflections from the boundaries are relatively high. The tweeter takes too much vertical space, making the speaker too tall and making nearfield very problematic, if ever possible. That forced Gamma to make it’s top horn “angle-able” that is very compromised solution as to find correct time alignment for none-parallel horns is possible ONLY for a single point in distance. Listen the things, then make a step closer or further and the HF sound will plunge apart, screwed by the phase anomalies (depands how the upper horn high-passed) . Did I mention that the Gamma’s tweeter horn is in fact a LF booster?  Dose this tweeter needed to boost 6dB at 5kHz of the tweeter care just the toppers octave? Does it make the tweeter to run a sharper crossover?

When I initially looked on the issue I thought that the Cessaro tweeter will use a narrow horn with very tight and controlled radiation. By narrowing the radiation angle the tweeter will be able to pick a few dB necessary to match the 110dB of MF drivers… However when you, Coops, posted the picture I realized that Gamma do not go to address all those problems with narrow horn.

Is anything that I migh propose? Sure, use ribbon instead of compression driver. 

Let presume that Cessaro Gamma uses my “Water Drop” Tweeter located as Macondo uses it – between the second and third horn. The Gamma MF horn is dropping virtually almost for a foot down, positioning itself at ear’s level and MF got better integrating itself with upper bass (tested!!!). The tweeter site above MF but it sits well behind the horns, at the driver level where there is a lot of space. So the their Gamma horn will be moving perhaps 6-8 inches down – not bad at all!  Now, we have the Gamma’ hypothetic ribbon tweeter is shooting in a narrow window between the second and third horn. However, the ribbon radiates a cylindrical waveform that has very narrow and VERY sharply terminated vertical window. So, the ribbon tweeter is way less sensitive to the presence the second and third horn then ET-703 in Tractrix or Le Cleach horn.

However, even after that, a ribbon tweeter will have (in Gamma case) some extra benefits. Pretend that you sit 7 feet from your Gamma with ET-703. The ET-703 radiates 100dB with 30% of reflections from juts the Gamma frame (completely of the wall numbers). So, you get 70dB from your driver and 30dB from noise that come from reflection. The direct sound of ET-703 and the reflected sound loose identically 6dB for every doubling of distance. However, if Gamma armed with a ribbon and if it even has the same 30% of reflections (which will be much less) then you will not have 70dB and 30dB ratio of direct vs. reflected but less reflections. The ribbon, being a line source loose 3dB for every distance doubling. However, the ribbon’s reflections DO NOT have cylindrical waveform and therefore they loose 6dB for every distance doubling. So, we have the HF reflections are naturally rolled off out from the direct sound of the speaker VERY good for HF!!!  Combining it with the fact that ribbon will see other horns much less it is possible to get a lot of advantages of ribbon and to lower the Gamma vertically and perhaps enable it in near field. I think I have mention at that British site that Macondo can play perfectly integrated from 7 feet!!!  Sure, there are few other tricks that enable Macondo to do it but a very conservative use of vertical plane for those types of systems I found is very obligatory.

So, I feel that if Gamma it trying to push itself as 150K “ultimate” off-the-shelf commercial horn playback then I think they need to review this use of a compression driver as tweeter as real-estate vise there are better solution. Sure whatever I said does not touch the subject of sound for the tweeter itself. As far as I was able to observe properly made ribbons have only 3 limitations:

1) Tone-disabled
2) The lower crossover point the worst sound
3) The dynamic-sinking with stresses compare to compression drivers.

The Gamma-type application should not worry about first and second limitations: the Gamma tweeter does not care tone and will be crossed high enough. Also, the RAAL’s Alex and I in a couple weeks will be able to get results that might change the dynamic-sinking factor with ribbons as I think we found what was responsible for it. If it so them RAAL might soon be able to produce tweeters that will have the dynamics identical to the  dynamic  of compression drivers.

I relay would like Gamma try to explore the direction of more “friendly” (for their design) tweeter…

coops wrote:

Romy Hi ,just a couple of things , in the Gamma there is another 1 inch TAD driver between the 4001 and the 703 , regarding the placement of the tweeter ,it is only recessed 3 or 4cm ,at a useable frequency range there will be negligible diffraction from the side panels.

Paul S wrote:

Romy, when you mention "dynamic sinking" of ribbons are you speaking of sub-8k Hz use of powerful ribbons like the Water Drop compared to 109 dB efficient compression drivers, or do you notice this dynamic sinking no matter how high you cross over? As you know, I use ~96 dB dynamic drivers and my 96 dB ribbons crossed ~10k Hz.  In this context I have not noticed any more dynamic sinking from the ribbons than I get from the dynamic drivers. Perhaps the lesser root efficiency and general problems with my L/MF effectively mask any dynamic sinking by my own HF ribbon during my own listening.

Romy the Cat wrote:

Yes, I have seen that Living Voice uses it. Frankly I was not impressed HOW it was used. I did not mention it at the British site, to bogus contingent of “critics” was there, but I think if that driver is good then there are better ways to use it in the Kevin Scott’ prototype. Rgs, the Cat

Merlin wrote:

I wonder if you could expand on that Romy? How is Kevin Scott employing the 703 and indeed in your wide experience, how could that be improved upon?

In context of Kevin Scott’s speaker it is absolutely beyond my comprehension why he decided to locate his tweeter with vertical axis offset. In some cases when there is a “geographic problems” people do it but in Kevin’s case there were no real-estate challenges in his loudspeaker, so why he shifted the tweeter to the side I of the speaker I have no idea.  He had lost some very fine moments of imaging doing it and it is unfortunate. I don't sing that Kevin's mind operates by the virtues of very “fine moments of imaging” as I think is that rectangular horn should be the obstruction that mad “fine imaging” water of the Living Voice’s lake.

Merlin wrote:

Sorry Romy. Which loudspeaker are we talking about? Do you have a picture at all?

Merlin wrote:

Well firstly on those, the tweeter is not offset to one side - it appears to be time aligned directly behind the midrange horn and upper bass unit. Secondly, that's a JBL 2405.

Romy the Cat wrote:

Sure, looking at some moment in the Orgon description I have a lot of suspicion that they use incorrect amplification  and incorrectly, and that multi-amping in there was not implemented as it should be but the desire was there. The Cat

el`Ol wrote:

I heard the Orgon and I didn`t notice any electronic colorations. The midrange of course doesn`t have the sweetness of an SET, but is the most realistic I have heard from a piece of hifi. The two things on my wishlist would be more transparency on top and better soundstage.

coops wrote:

Romy will you visit next years CES ,2008? Regards Keith.