I have been testing someones ZROCK2 in my system this weekend just to make sure it has no intermittent issues... and since it was installed I decided to try the filter A B switch. I always listen to the ZROCK2 with the switch in the position that does not roll off the highs. Without adjusting the dial, I flipped the switch to the more rolled setting. Of course set flat where I have it, it really doesn't start rolling the highs much, but the gain does drop a touch and sound does change a little. I wouldn't say it was dramatic but rather just detectable. If the gain hadn't dropped it would be very hard to hear that anything had happened.
Then I got in the listening chair and the entire sound stage had moved back and focused up and has me wondering if this might actually be the best sound stage I have ever had in my system. I love good 3D imaging with super depth and width and this is pushing all the right buttons. The combination of the network and the ZROCK2 set in this manner is creating a soundstage that is hard to believe using the Sarah 300B.
As you know the Sarah has a switch that using it's own internal ZROCK technology bumps the sound stage back or forward, whatever is your preference. I generally like it in the back position because I like a lot of depth. So it is the combination of these four elements (ZROCK2, SARAH Voicing switch and tube compliment, the NETWORK and the FAST15's response in our large baffle that has created this magic.
One interesting thing is the null in my room at 30~40Hz at the listening chair. This is created from the open doorway on the sound end of the room. I have fixed it in the past with a door that blocks the lower half of the opening, but constantly opening that door to walk in and out of the room was a hassle. With the F15's rolling off at 50Hz, this null is never noticed from the listening chair.
Last night I did a serious round of listening and found myself wondering when I was going to hear the 30Hz stuff because the bass was no better than before with the F15. Then I remembered the null. So I moved my chair back 4 feet out of the null and did some more listening. I was fairly amazed at the amount of low end these speakers have. It's subwoofer bass, the kind you would get from two large 15 inch subwoofers. Equally amazing is all the ultra low bass that was in many of the tracks I played, that I didn't know was there with this kind of prominence.
The experience was like having two large subs added to the system and getting them perfectly integrated and time aligned and having those subs driven by an identical tube amplifier with identical speaker cable and interconnects and power cords and tubes.
This makes me realize that creating small or skinny baffles with the F15 or Fast15 mounted high in the baffle is a mistake because those baffle designs have no bass by comparison to this. So a W15 woofer gets involved in yet another baffle to give you bass. It is less efficient and requires more power. Now you need two amps, and more or bigger baffles, additional cables and so on. All of this is likely to consume more space in your room than a simple pair of ZF15L baffles and unless the W15 is actually in a large and wide enough baffle it's highly unlikely you will hit 30Hz with it.
I was never a big fan of wide speakers - favoring narrow "audiophile" towers that "imaged well". Randy of Caintuck Audio who designed this barrel shaped baffle changed all that. I am convinced it is one of the best open baffle designs there is by gracefully handling energy within the panel to the degree that baffle step compensation is never needed unless your driver sucks. In fact, this design if you notice is a free floating baffle. There is no frame to secure it, etc., just a high mass base that it bolts into. That means the term "baffle" is misleading. It is so because we all view a good speaker baffle as something that is as inert as possible. Yet on this design, yes it is very dense, but it is a transducer -- meaning that the entire 'baffle' is vibrating to create a sound wave. This means that the woofer is mounted in a transducer that extends its size to the entire area of the 'baffle'. Since the driver is mounted in a transducer which carries the sound away from the driver out to the edges of the arc any baffle step in the response should be nearly undetectable.
The ever changing shape from the arc on either side of the baffle evenly distributes the energy across a wide band of frequencies. In contrast if it were a square board, there would be four triangles attached to the arcs where once the energy passed the line of the arc, it would then see decreasing mass and launch most of that energy into the tip. What didn't launch from the tip would then reflect back to the line of the arc causing hateful harmonic distortion in the panel corners and a fair amount of discord in the panel itself. A baffle like that would become unlistenable at higher volumes, and at normal listening levels it would easily locate itself.
Anyway the design is brilliant and even after many years it continues to amaze me how well it works. Hats off to Randy!
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