Systems ListRythmik AudioFV18

ManufactureRythmik Audio
System typeVented
Driver Size18 "
Number of drivers1
External volume9.22 ft3
Dimentions (Width ◊ Height ◊ Depth)21 " ◊ 23 " ◊ 33 "
Weight155 lbs
Power900 W
Aprox. Price$1699 USD


The FV18 subwoofer is a new vented offering from Rythmik Audio. It is larger than the FV15HP subwoofer that was tested many many years ago, but not quite as over the top as the even larger, more powerful FV25HP.  The FV18 is a vented design, which allows a choice of operation between 2 different tuning points. 16Hz and 12Hz. The FV18 is based around the same DS1820 18 inch driver used in the sealed F18 subwoofer and the same 900w amplifier platform. 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. The FV18 is not a small subwoofer with dimensions of  21x23x33 inches, which includes the grille and amplifier heatsink. The FV18 is also quite heavy at 155lbs. Available finishes include: Matte black, black oak and gloss black. Additionally the Rythmik DS1820 based subwoofers are available with a "silver", raw, spun aluminum driver cone. The FV18 sells for $1699 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 driver inside of the F18 and FV18 subwoofers is Rythmik’s proprietary DS1820 driver. The 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. Interestingly the frame has a 12 bolt pattern instead of the usual 8 bolts. The spider system appears to be a single 8 inch diameter high excursion unit. The motor system consists of a large double stack of 120oz ferrite magnets that are about 8.5 inches in diameter and 1 inch thick. The back plate features a generous bump out to clear high incursion levels and a large pole vent for cooling. The top plate appears to be about 12mm thick. The frame also features large under spider vents to help facilitate cooling and the motor design incorporates multiple shorting rings 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 also keyed by manner of smaller spade terminals for the servo coil connection. Xmax for the unit is said to be 20mm one way. The DS1820 is a weighty and substantial driver.

The amplifier for the F18 and FV18 subwoofers is Rythmik’s HX1000XLR3, which is rated as a 900w rated amplifier. 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, what each does, how they interact and when to use each could be overwhelming to some users, even after reading the guides provided by Rythmik. Removing the amplifier from the cabinet revealed that these are not SMPS based or switching amps, but are analog based with a large, old school, transformer. These Rythmik amplifiers are a serious hunk of equipment. The HX1000XLR3 probably weighs 20lbs or more and the HX2000XLR3 is even heavier.

The cabinet of the FV18 is constructed of heavy MDF material and is cross braced internally, much like its little brother the sealed F18. The front baffle houses the recessed DS1820 driver 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 also glued and locked into the internal bracing. 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 sealed F18 subwoofer. 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 FV18 cabinet may be heavy, but it proved to be inert and rattle free during maximum output testing.

The FV18 vented subwoofer shares a lot of characteristics with the smaller F18 sealed sub. This is unsurprising since it shares the same driver and amplifier platform. The control schemes and myriad available adjustments are exactly the same for both units. The differences are in the cab designs. The larger, more expensive and heavier FV18 vented subwoofer provides more bass headroom overall due to the venting and greater internal volume. The main advantage is in the 12-40Hz frequency range where it offers substantially more headroom than the F18. Additionally, since the driver excursion is lower in the deep bass due to the vent loading and the output is higher, the FV18 offers a large reduction in harmonic distortion over most of the deep bass range. Like nearly all vented subs the FV18 can be pushed to produce audible vent noise near the tuning frequency, but that doesn't occur until approaching maximum output. This is most apparent with the reduced vent area when operating with the 12Hz tuning. The 12Hz tuning offers some increased output capability below 16Hz but at the cost of slightly reduced output above 16Hz. In cases where the FV18 is placed in larger spaces and/or the output demands are very high it would be best to use the 16Hz tuning configuration. In smaller spaces or in cases where the playback levels are not as high the extra extension of the 12Hz tuning may make more sense. One subjective take away was that if both the F18 and FV18 are kept well within their capabilities and the response shapes are configured to be similar, they perform and sound remarkably alike, except that the FV18 has more dynamic reserves available if called upon during demanding passages. The advantages for the smaller sealed F18 are the more compact size, weight, slightly lower cost and the complete lack of vent noise under any situation. Both subs perform admirably and represent their respective type of design well. Which one to pick would come down to individual preferences and situation.