Systems ListRythmik AudioFV25HP

ManufactureRythmik Audio
System typeVented
Driver Size15 "
Number of drivers2
External volume11.6 ft3
Dimentions (Width ◊ Height ◊ Depth)21 " ◊ 41.5 " ◊ 23 "
Weight210 lbs
Power1800 W
Aprox. Price$2499 USD


The FV25HP subwoofer is a new high output offering from Rythmik Audio and is currently the largest, most powerful subwoofer in their lineup. The FV25HP employs a pair of Rythmik DS1520 high power 15" drivers and the most powerful amplifier currently in the Rythmik catalog the HX2000XLR3. These are combined with a large cabinet measuring 21x41.5x23 inches, including the grille and weighs as much as a large man at 210lbs. Like the FV18 the FV25HP is a vented subwoofer, but unlike the FV15HP and FV18, the FV25HP is designed to operate in a single 12.5Hz tuning, with all vents open only. As with all of Rythmik's subwoofers it employs the companies patented servo control system. I will not go into the operation of the servo system here. For more information on that I recommend reading the documentation available at the Rythmik website here, or for an even better understanding, a perusal of the patent documentation. Available finishes include: Matte black, black oak and gloss black. The Rythmik DS1520 based subwoofers are also available with a "silver", raw, spun aluminum driver cone. The FV25HP sells for $2499 shipped to the continental 48 US states. The raw aluminum look cone adds an additional $100. The standard Rythmik warranty for their subwoofers is 5 years on the cabinet and driver and 3 years on the electronics.

The drivers inside of the FV25HP subwoofer are the proprietary Rythmik DS1520. This 15 inch driver features a spun aluminum cone, rubber half roll surround with the Rythmik logo molded into the mounting flange area and the familiar 12 spoke frame. The spider system appears to be a single 8 inch diameter high excursion unit. The motor system consists of a large double stack of ferrite magnets that are about 7.5 inches in diameter and 1 inch thick. The back plate features a bumped back plate to clear high incursion levels and a pole vent for cooling. The top plate appears to be about 12mm thick. The frame also features under spider vents to help facilitate cooling and the motor design incorporates a shorting ring to combat inductive distortions. The voice coil is nominally a 3 inch diameter unit with a secondary smaller coil wind for the servo circuit. The coils are labeled and keyed by manner of smaller spade terminals for the servo coil connection. Xmax for the unit is said to be 15mm one way. 

The FV25HP's dual 15's are motivated and controlled by Rythmik‚Äôs HX2000XLR3 amplifier. This 1800w rms rated unit is a big slab of an amplifier, probably weighing in excess of 25lbs due to being an old school analog design utilizing a very large toroidal transformer and a massive aluminum heatsink. In keeping with Rythmik tradition it has a veritable buffet of control knobs and toggles on the face plate. There are stereo balanced XLR inputs which are switchable via a toggle to operate as a matched pair, or with the R source in XLR operating as an unfiltered LFE input. There are also 2 sets of unbalanced RCA style inputs. One set for LFE and one set for use in systems without a dedicated external low pass filter. The power switch is able to be set for Auto/On/Off. There is a 12v trigger available as well as a switch to enable the amplifier to be connected to either 120v or 240v AC. The usual volume, phase and on board low pass filter controls are included as well as a single band parametric EQ, which can be enabled or bypassed via a toggle switch. Towards the bottom of the amplifier there is a series of 4 toggle switches used for tailoring the subwoofers response shape and behavior. The left most switch enables a fixed low pass filter at 50, 80 or 100Hz when not using the LFE input. Of note is that this toggle switch also interacts with the typical low pass filter knob provided, which further increases the range of adjustment of the internal low pass filter. Next to the low pass filter toggle there is a high pass filter toggle labeled "Rumble Filter". This toggle is an On/Off switch for a high pass filter that rolls off the extreme deep bass frequencies, for added protection of the subwoofer. The right 2 toggle switches at the bottom of the amplifier are for tailoring the deep bass extension of the subwoofer and varying the amount of damping provided by the servo system between Low/Mid/High. There is even a switch to turn on or off the amplifier limiter circuit. Rythmik is the only company I am aware of that provides an option to defeat the limiter. Needless to say the amount of controls provided give tremendous flexibilty to tailoring the subwoofers behavior and response shape, but...What each control does, how they interact with each other and when to use each, could be overwhelming to some users, even after reading the guides provided by Rythmik. 

The cabinet of the FV25HP is constructed of MDF material and is extensively cross braced internally. This type of bracing is even more important for larger cabinets with big panels such as this one, but the tradeoff is a slight increase in weight. I'll take the extra weight vs potential panel vibrations. The front baffle houses the pair of recessed DS1510 drivers and a trio of 3.5 inch diameter flared ports at the bottom. The vents are quite long and make a 90 degree curve up into the cabinet. They are glued and locked into the internal bracing similarly to those in the FV18. There is a generous amount of damping material placed inside of the cabinet on the walls and around the port tubes as well. The top and bottom corners are rounded over like the F18 and FV18 subwoofers. 4 large, rubber feet are provided, that screw into the base of the cabinet. These proved durable after walking and sliding the Rythmik subwoofers over a number of surfaces. The provided grille is constructed of black fabric over an MDF frame with the Rythmik logo towards the bottom. The FV25HP cabinet remained inert and free from obvious panel vibration or noises during maximum output testing. 

Testing maximum output and behavior of the FV25HP, while running from a 120v line versus a 240v line, showed only the smallest advantage for the 240v line. The testing was done with the limiter both off and on. The 240v line amounted to about a 0.6dB advantage during the long term sine wave sweeps and only 0.2dB with the burst signals with the limiter turned off. With the limiter on 240v showed even less of an advantage. While this is a measurable difference it is extremely unlikely that it would be audible. The FV25HP was run on both a 20 amp and a 15 amp 120v lines and neither breaker was tripped during testing, even with the long term sine sweeps at maximum output. The FV25HP appears to operate just fine off of a standard 15a 120v outlet, provided that the circuit does not have a bunch of other devices increasing the load. I would hesitate to recommend running a pair of FV25HP's off of a single, standard 120v circuit though. To sum up...If you have a 240v circuit available by all means run the FV25HP off of it. The miniscule performance gains would not justify installing a dedicated 240v circuit though. 

The FV25HP subwoofer proved to be quite potent and polished in both the listening sessions and the captured measurements. It sounded quite similar to the FV18 in use but provided more of everything. In particular the distortion results were very good with low THD until the subwoofer is pushed to maximum output. Even then the FV25HP does not produce any unruly or obvious distress noises. Provided that the limiter is engaged, the most offensive sound I could manage to pull from the FV25HP was some vent noise below 20Hz. Even with all 3 vents open the dual 15's can overload the vents ability to handle the air volume required near the tuning frequency. This is something that nearly all vented subs suffer from under worst case scenarios. Similar to the F18 and FV18 subwoofers, turning off the limiter allows the FV25HP to produce a smidge more output, but at a cost of greatly increased distortion and heavy amplifier clipping at the limit. With the limiter on the sub remains unflustered and relatively clean sounding at maximum output. With the limiter off there is a clear negative impact and the sub sounds like it is in distress when driven to maximum output. It is not a subtle difference by any means. I recommend operating any of the Rythmik subs with the limiter engaged. The extra 1dB maximum output potential isn't output potential I would want to make use of. With or without the limiter engaged the FV25HP is one of the most powerful commercial subs ever tested at Data-Bass. When not being utilized near its maximum potential the FV25HP sounds very good and this is born out in the measurements.