Vandersteen Sub woofers v Rythmik Subs


I really love the idea of the Vandersteen Subs where they are connected with the mains via extra speaker cable off right and left channels off the main amplifier, which is supposed to provide better bass transition from the mains while keeping the signature from the main amplifier. My question is with Vandersteen coming out with the SUB THREE and the price going significantly higher, I was wondering if there are other subs for less that you could integrate in the same way. (Most subs seem to rely on the line level input which is just a sub-woofer RCA going from the pre-amp to the amp on the sub). Can this same Vandersteen set-up be achieved with other subs?
I picked Rythmik since they are known (in the home theater community anyway) for being one of the best bang for the buck subs and the most "musical" of the bunch. (between Hsu, SVS, PSA).
And could I possibly achieve even greater sub-woofer nirvana since I could get an 18" for around $1500? Vandies only have 3 eight inchers.

I am a Vandersteen fanboy and I would like to support RV whenever I can, but don’t know much about my other sub-woofer options so looking for some feedback. Doesn’t even have to be related to Rythmik necessarily. If you know of other subs that can integrate the same way I want to know about it!

Thanks
bstatmeister
     When did Vandersteen start positioning, considering and pricing themselves as an ultra high-end company?  I've always considered Vandersteen as a solidly high-end manufacturer that offered very good quality speakers, subs and related crossovers at  more reasonable prices,especially considering  their proven history of high quality offerings.
     I was just checking out the new Sub Nine on their website.  I haven't heard them but from their description and look, they certainly seem like another fine Vandy product.  But I was a bit shocked by the $18,900 per pair suggested retail price.   The very fine Model Seven MKII are also very expensive at $62,000 per pair.They  are now even selling a pair of 600 W@ 4 ohms mono-block amps that have tubed input stages and bipolar transistor output stages (M7-HPA) for $57,200.
     So, if you want the best all Vandy system while optimizing in-room bass response, you'll need the Model Sevens, the matching mono M7 amps along with the extra pair of Sub Nines to optimize the bass response.  This will set you back $138,100 but you'll also get a pair of nice Audioquest  cables gratis.
     Undoubtedly an excellent audio system in almost anyone's estimation but not the better performance than expected for the price that I remember when I was speaker shopping in the early 1980's and auditioned the 4C. 
     I'm not sure if anyone on this thread is seriously considering the Sub Nines but I cannot understand why anyone would pay $18,900 for 2 subs when they could buy the Audio Kinesis  Swarm or Debra bass system with 4 subs that will likely provide better in-room bass response for $2,500 and save $16,400 in the process.  Yes, the Nines may produce more bass but I've never had an issue with the bass quantity ( or quality) with the Audio Kinesis.
     It's similar to what I recall from past Vandy products:; a product that offers better than expected performance  based on the reasonable price. . 
     Anyone know why Vandersteen decided to move away from these type of products, like their former 4C speakers, and toward the more expensive and esoteric?
Tim    
My guess is Richard has realized, through R&D, very significant improvements in the sound quality of his offerings over the decades and has decided to go for the ne plus ultra to see how good the realism of his designs can get. Listening to the Treo CTs daily, I need to hear the Model 7 system to realize how far he has been able to refine his design concepts. As is so prevalent among many successful audio designers, Richard is reaching for the stars. Of course, in result of this lofty pursuit, those of us downstream, benefit from his efforts as he incorporates the lessons learned into his more modestly priced offerings.
I believe that speakers like the 1ci's, 2ce sig. II's are what really keep Vandersteen in business. But like all designers (and RV is no exception) like to see what they can accomplish with no price constraints. That dream, that pursuit, of what can be possible within the scope of their expertise. And yes, they can justify this thinking with the "trickle down effect" to their more affordable products. This has been evident thru the years with the steady improvement of his core products like the models 1, 2, and 3's. Making great highend speakers like the Treo Ct and the Quattro Wood Ct have brought a lot of what goes into the Ultra high end speakers he makes to a more affordable whelm of gear.
In case it wasn't yet mentioned, the Sub 9 is not Vandy's only subwoofer.  The 3W series is replacing the 2W series.  While not inexpensive, it is much less expensive than the 9 Sub.  The 9 is intended to augment the Model 7, for the most part, and is priced accordingly.
@hifiman5 
Only a proselyte would believe that it is possible for a dumb amplifier to change characteristics based on it's driving source. If that were possible, changing any of the 'perfect' electronics in our systems would hopelessly dependent on its upstream device.

In the Vandersteen 2ce II, the impedance doubles from 4Ω to 8Ω between 35 and 75Hz, dropping to a nominal 6Ω @ 200Hz.

The output of a tube amp transformer will be a non-linear voltage driving such a load  as can been see on any Stereophile tube amp review.

The Vandersteen sub amp is a voltage driven device, as are most amps. When the voltage rises the output of the sub will also rise. What results is a doubling of the bass output @ 35Hz vs 75Hz. This would not occur with a tube amp driving a loudspeaker.

Another issue I never considered a good design was the passive XO with limited adjustment. In all but a limited number of amp input impedances, the frequency will be sub optimum possibly varying by as much as half an octave. It's been my experience that as little as 10Hz can have a significant effect when tuning a sub into room. A fixed frequency sub may work well in the lab, but may not elsewhere.

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