I've been behind on keeping up with forums as we are short staffed for production with some people out, so I've been in back more than at the computer. I was about to respond on our forum when I saw the post here. IMO of listening on multiple occasions and seeing measurements to back up impressions, the DirectServo does a very good job of reducing distortion... to the similar levels we can with good motor design. In the days before precise DSP, it also made for an efficient and very effective way to correct the frequency response in what ever box size the woofer is placed. DSP is now extremely flexible, and with the right efforts, it's possible to design very low distortion woofers.
Taking a look at the final specs I see the overall size is pretty much the same, swapping height for width. With the driver and amp used it's probably more similar than different in capabilities. The SubMersive does have a serious amount of dynamic headroom above 40Hz, and given the FV25HP uses the same driver and amps, it appears they will be close in this regard. Below 20-25Hz is where I could see the Rythmik having lower distortion within the limits, similar to what the much newer driver in the F18 offers in lower distortion below 25Hz. In older versions of the DirectServo designs, the "autocorrect" action of the servo could result in some hard clipping of the amplifiers which would put the stops on the fun with big dynamics in movies. They've greatly reduced this behavior when you engage the limiting switch on the current offerings, but I would argue this behavior near and into the limits is something we do a bit differently and allows our subwoofers to play so much beyond what might otherwise be expected in real use. Another harder-to-quantify quality is the SubMersive's ability to excels with impact, articulation, and snappy response with even rather high crossover frequencies. Subjectively the SubMersive's can deliver an intensity that I haven't heard to the same degree from Rythmik offerings, which often lean toward a very composed operation. I would most certainly expect different personalities from each. Of course keep checking back as who knows what will be out when you get around to upgrading from your original 1000W SubMersive. FWIW, we have recently finalized a new single amplifier per unit option for the SubMersive which has a universal power supply that gives the same input controls and options of the latest + amplifiers without the need for a separate version for our international customers, and less than 1/2 the cost of what we had to charge for the HPi+/F2i+ amplifiers. We'll be adding these as the HPi / F2i versions to the website as we get closer to having units in stock.
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