Sounds like this will be a great time. I would absolutely LOVE to hear all of these speakers, especially the SoundScapes and the Phil's!
There seems to be some confusion regarding the Amorphous core option for the various RAAL tweeters. I will do my best to try and clarify a few things.
Originally Posted by cschang
But the Cirrus uses the 70-20:
"Drivers Used RAAL 70-20XR Tweeter
Audio Technology C-Quenze 18H52 Woofer"
Two different versions of the 70-20XR...one with the Amorphous Core and one without?
The Amorphous Core is mentioned on RAAL's website, mentions that it is something new, but not that it is an option.
As Dennis mentioned, this is an optional upgrade and I while I don't have our costs readily accessible at this moment, I believe Dennis's estimates on costs are about right. Like Salk, we are just absorbing the additional costs for the AM core as I do feel it is worthwhile.
Originally Posted by Dennis Murphy
The "amorphous core" is an option on both the 70-10 and 70-20. For company buyers, it costs perhaps $75 - $80 extra per unit (probably less). I've worked with both cores in the 70-20, and to me they measure the same, sound the same. I can't find any clear explanation of what the amorphous core is or does. I've heard that it presents an easier load to tube amps, but there's nothing wrong with the regular RAAL in that regard. Jim Salk uses the amorphous core in his speakers, but doesn't hype any benefits. RAAL makes great stuff, but this particular aspect of their product line is a mystery to me. I wouldn't read any significance into it.
No real mystery
when referring to the "core" -- RAAL is referring to the core of the impedance matching transformer. The actual load presented to an amplifier will not change due to the core material (that is a function of the primary and secondary windings) but since AM core transformers are less lossy, lower power high resolution amplifiers will benefit most.
Originally Posted by Nuance
Perhaps the 70-10 RAAL doesn't utilize that core, but only the 70-20?
Available to both...
I will do my best to break it down into the simplest explanation.
A true ribbon tweeter consists of (3) major components. The diaphragm (aluminum with the RAAL's) the magnets (neodymium) and the transformer.
A true ribbon tweeter is designed such that a very thin conductive material is suspended between extremely powerful magnets. A current is applied directly to the diaphragm itself, thus reacting with the strong magnetic field generated by the magnets resulting in the diaphragm itself moving forward and back generating sound waves.
Unlike a dome or planar magnetic tweeter, a true ribbon does not have a voice coil - thus eliminating a very large amount of moving mass which accounts for the incredible transient accuracy which is clearly audible. Sounds simple, right? The lack of a voice coil creates a problem however....
Since voltage is applied directly across the diaphragm itself (the ribbon) and since the ribbon is highly conductive (extremely low resistance), your amplifier is going to see a load that may be as low as 1/10th of an ohm and it is either going to enter protection mode or fail almost instantly. To solve the problem, an impedance matching transformer must be used to keep the amplifier output power (wattage) the same while converting current delivery and, subsequently, voltage to usable levels.
The transformer design in a true ribbon tweeter is critical to performance as all transformers are subject to various losses, MUCH more so than capacitors, resistors and inductors. Keep in mind that the signal being sent to the ribbon is first traveling through the transformer and being transformed
I won't get into complex transformer design but a transformer consists of a core (typically metal) with one set of windings on one side of the core (primary) and another set of windings on the other (secondary). Current flows through the primary windings, creating a magnetic field in the core. This magnetic field then releases into the secondary windings creating a current which is directly proportional to the ratio of the # of windings in the secondary coil compared to the primary, and the process continues generating a "transformed" current flow.
The transformer core material has a significant influence on the performance of the transformer as it is continually subject to magnetic polarization. Ferrite cores are typical and are of very high quality, however, Amorphous metal cores are more efficient and can magnetize and then demagnetize faster and with less losses compared to ferrite cores.
Evidence of this will not show up on frequency domain measurements but are indeed evident in time domain measurements.
I have taken comparative measurements between the AM core units and the ferrite core units and the differences are noticeable. As far as actually hearing a difference between the two, there were times when I thought I heard subtle differences in micro-dynamics and yet other times I could not tell them apart. However, these are with my ears and we all detect sounds differently.
That said, it is in my professional opinion that if going with a RAAL ribbon, the AM core option is much more important to overall performance than choosing exotic crossover capacitors, silver solder, magic stones
and various other audiophile tweaks. Performance differences are measurable; therefore they can certainly be audible and AM core transformers are the choice when designing a high performance transformer (less losses.) Since many of you are already considering what is, perhaps, the best ribbon tweeter available, it certainly makes sense to go with the higher performance transformer option.
If interested, a simple Google search on Amorphous metal or even Amorphous core transformers will provide more detailed information.
Hope this helps!!!