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Thread: Rythmik DS1500 CI

  1. #1
    Join Date
    May 2008

    Rythmik DS1500 CI

    Introducing our new custom range of subwoofers
    There are many benefits to a custom subwoofer product. For those concerned with spouse acceptance factor, often a subwoofer is best felt and heard but not seen. For others, a subwoofer should match the interior of your home. Either way, our CI series products are the ideal choice. Have it built by a local trusted furniture maker, or if you are handy, you may choose to built it yourself.

    Our DS1500ci subwoofers feature the same components as our F15 subwoofers. This subwoofer features our high end DS1500 sub driver which is available in silver aluminum. Also featured is a subwoofer plate amplifier of your choice from our range.

    Your choice of enclosure
    Direct Servo technology can be applied to any enclosure type - it is not limited to sealed boxes. If you would like to use an enclosure other than sealed or vented, we can design a custom servo board to ensure you receive all the benefits the technology allows. For a vented box, we recommend this product over DS1200ci.

    Subwoofers for audiophiles
    For audiophiles looking for uncompromising accuracy, our subwoofers are the ultimate choice. They features our Direct Servo technology to ensure accuracy and definition. We don't merely design low distortion subwoofers. We are concerned with eliminating the problems which most degrade the accuracy of a subwoofer. Problems like memory effects which are clearly audible are dramatically reduced. Perhaps you already own a subwoofer but have been disappointed to discover that it added more than extra depth. Or perhaps you have avoided purchasing a subwoofer because you were unwilling to compromise the accuracy of your system. Rest assured that you have found a subwoofer for audiophiles.

    Better technology
    Nearly all subwoofers on the market are based on outdated technology. Our subwoofers are based on our patented Direct Servo technology. Not only does our technology surpass that of conventional subwoofers, it also offers significant improvement to the performance of other servo systems. In our technology section, we describe the differences between Direct Servo and other servo technologies. Our system is better suited to music reproduction than other servo systems.

    Amplifier and driver options
    DS1500ci features your choice of three amplifier options. A300SE has slightly less power handling and requires a slightly larger box. A370PEQ features parametric EQ and our A370XLR has balanced inputs, making it ideal for studio use.

  2. #2
    Join Date
    May 2008

    Re: Rythmik DS1500 CI

    Unlike conventional subwoofers, the frequency response remains flat at all output levels until the output limits have been reached. Without Direct Servo, a flat response will only be achieved at low output levels.

    The above shows the frequency response of our sealed version DS1500 subwoofer. The vented box provides 4-5dB more output from 20 - 30 Hz (using the same amp). Since the response rolls off rapidly below 20 Hz for vented box, the sealed box has more output below 20 Hz. Vented box is ideal for HT in a large room.

    Component selection
    We carefully select all components for performance and value. We have selected components that will return the best value. For instance, the MILLS current sensing resistors, the op amps, and the hand selected MOSFET inputs stage for power amplifiers. We don't cut corners. We also avoid wasting money on "audiophile" components which offer no real advantages.

    Flexible design
    All of our subwoofers feature unique bass extension controls which are not normally provided on subwoofers. This enables the user to customize the output and extension to achieve the best compromise in any room. Most subwoofers neglect to provide bass extension control, and the result is that dynamic headroom is compromised.

    Sub crossover filter
    A lot of audiophiles like to run their front speakers full-range. The objective is to avoid any signal degradation on the front speakers. Our recommendation is to have a simple RC network as shown in the FAQ page to relieve the bass burden from the front speakers. In either case, a 24 dB low pass roll-off version of the subwoofer is recommended. Phase alignment is also very important. One can either use the phase control on the plate amps, or the delay time adjustment on HT receiver to dial in the phase alignment. The phase control on the plate amp is only for phase lag adjustment on the subwoofer. The delay time adjustment on the HT receiver can achieve both phase lead and phase lag adjustment on the subwoofer. As a general rule of thumb*, the sound wavelength of 50 Hz is 20ft. A full wave is 360 degrees. Therefore, if we put the physical distance in the delay time adjustment menu 5 ft further (or closer) than the physical distance is, the HT receiver will put a 90 degrees phase lead (lag).

    Customized Bass extension
    All of our subwoofers feature unique bass extension controls, shown below.
    The bass extension controls enable the user to customize the frequency response of the low end. This puts control back in the hands of the user. The controls customize a high pass filter, which attenuates frequencies below a given frequency. If set to 14 Hz, bass below this point will be filtered. The damping control determines the slope, high damping providing the steepest slope.

    Why is this necessary?
    Very low bass can cause very large cone excursions without contributing useful output. The result is that the output is limited by the large excursions required at very low frequencies. The bass extension filter increases output by reducing unwanted signal. For maximum output, the 28 Hz setting should be used with high damping.

    Recommended settings
    For sealed subwoofers, the default configuration is the 14 Hz setting with low damping. For home theatre use, a higher setting for both switches may be used. For vented subwoofers, the default configuration is the 20 Hz setting with high damping. In individual situations, other settings may prove more suitable. Experimentation is recommended to determine best fit. Caution is recommended with the choice of settings for vented configurations. If the damping setting is set to a frequency below the tuning point of the subwoofer, cone excursion will not be effectively controlled. Low damping will also not provide sufficient excursion control.

    Voltage selection
    Before use, correct voltage must be selected. Voltage switch is shown below.

  3. #3
    Join Date
    May 2008

    Re: Rythmik DS1500 CI

    DS1500 -- 15" subwoofer driver

    This is the third generation of our servo driver. While designed specifically for our Direct Servo subwoofers, all our drivers are also suitable for conventional use. After extensive testing and comparisons and positive customer feedback, we feel compelled to offer them for sale separately. In a market dominated by products designed to look good on paper, we have created products that feature uncompromising performance. Audiophiles are well advised to keep in mind that drivers that look most impressive on paper may not be very accurate.

    Impressive on paper vs real performance
    To improve the specs on paper, most existing drivers on the market use more voice coil layers. This requires a wider voice coil gap. As a result, not only the moving mass of the driver is increased, the magnet strength is weakened, and the voice coil inductance is also increased. In many cases, the result is a driver which performs poorly above 40 Hz. The problem is more serious than it may appear. If we play a 40 Hz tone, harmonic distortion products will be added to the original. 3rd order distortion products are particular objectionable, and for this 40 Hz tone will be at 120 Hz. The ear is more sensitive around this range, and as a result, it makes the distortion more audible. It is often thought that a subwoofer that has poor distortion performance can merely be crossed low. The problem with this is that harmonic distortion will be clearly audible and accuracy will be compromised. Most subwoofers are plagued with these problems. Not only are they unsuitable for operation above 40 Hz, they also add a lot of distortion even when crossed this low.

    Our approach to driver design
    We take a very different approach. Our drivers have low moving mass, high flux density in the magnet gap, and low distortion. We start with two 0.84" stacked magnets (for a total of 1.68" magnet height) and a 1.8" long sensing coil with 0.5" top plate to support 1.2" linear peak to peak excursion. In order to achieve the goal of low moving mass, we have designed a lightweight 4 layer voice coil. To reduce distortion and low inductance, we added a FEA-(finite element analysis-) designed short circuit ring that is effective above 30 Hz for reducing flux modulation and at the same time reducing voice coil inductance at higher frequency. The cast frame basket further improves the rigidity of the driver. The result is a driver capable of high SPL and that is also accurate.

    Conventional vs Direct Servo
    For audiophiles who desire the ultimate in accuracy, we recommend our Direct Servo subwoofers. While our drivers are better than most, their performance in a conventional subwoofer will never be as good as a Direct Servo subwoofer.

    Driver features
    • Rigid anodized aluminum cone (silver only)
    • Rigid 12 spoke cast aluminum basket
    • FEA designed aluminum short circuit ring to reduce 2nd order distortion
    • High linear excursion capability of 1.2" peak to peak (15mm one-way) xmax
    • High mechanical excursion capability of 1.8" peak to peak (xmech) to reduce risk of bottoming
    • Very low inductance
    • 24 ohm ultra thin sensing coil for servo operation keeps moving mass low
    • Woven wire lead in the spider to prevent rattling during high excursion
    • Gold spring loaded terminals for easy solderless cable connection
    • Single 3.0 ohm voice coil
    • Mounting without gasket (15-7/16" outer diameter and 7/16" depth)
    • Two 0.84" stacked magnets for a total magnet height of 1.68"
    • Cutout: 14-1/16"
    • 6.75" clearance in depth
    • 500W RMS max power

    We supply a foam gasket tape (also comes with the driver) that goes between the driver basket and the enclosure to ensure proper seal. We recommend to put the tape on enclosure, instead of on the driver basket.

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