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    PURIFI PTT6.5X04-NFA-01 6.5″ Ultra Low Distortion Long Stroke Driver 4 Ohm

    € 305,74€ 369,95 >10 In stock: delivery time 1-4 business days
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    Product description

    The PURIFI PTT6.5X04-NFA-01 is a refined bass-midwoofer, incorporating state of the art technology that is based on extended research. The result is this ultra linear long-stroke woofer with unparalleled performance. 



    • A whole new take on driver design
    • PURIFI’s Natural Surround
    • Extreme low distortion over full excursion range 
    • Engineered and manufactured in Denmark 
    • Excellent midrange performance 
    • High power handling
    • High linear excursion limit with constant force factor


    Product Details

    PURIFI PTT6.5X04-NFA-01 bass-midwoofer 


    PURIFI is a fresh company that designs and manufactures extreme high performance transducers and amplifier modules. Don’t let the freshness fool you; Their leadership team consists out of some well-respected audio technology pioneers. PURIFI developed a deep understanding of many performance degrading aspects for both amplifiers and transducers. Thanks to this understanding the PTT6.5X04-NFA-01 is the most refined bass-mid woofer from our woofer category.


    Besides this 4 ohm version, there is also an 8 ohm version and a 6,5" passive radatior available. Looking for similar performance, but something smaller? Take a look at the 4" PTT4.0W04.


    The challenge 

    Loudspeaker drivers are known to add a large, if not the largest, amount of distortion in an audio signal chain. Reducing this distortion is a challenge with the complication of fine-tuning to improve one part (e.g. harmonic distortion) often results in a degradation of  another part (e.g. intermodulation distortion). These distortions consist out of several separate distortion mechanisms. By carefully mapping and completely understanding these mechanisms, PURIFI succeeded in improving the overall performance by a large degree.


    A whole new take on driver design

    PURIFI developed mathematical models for the motor system, suspension, cone and surround. These models allowed for optimization of each distortion mechanism separately. This systematic approach reduced all distortions mechanisms and keeps intermodulation distortion low. The result makes that the PTT6.5X04-NFA-01 is a compact 6.5” driver that parallels or even surpasses  the bass performance of a low excursion, large surface driver, while it also excels in midrange performance.


    The mechanism 


    Low force factor modulation

    Current through the voice coil is not distorted by cone movement. Gives undistorted midrange regardless of excursion

    Constant force factor over excursion - Bl(x)

    Prevents amplitude devotions of midrange output during large excursion (sometimes called ‘burbling’)

    Low surround radiation distortion 

    Reduces harmonic and intermodulation distortion caused by surround

    Low magnetic hysteria distortion 

    Reduces harmonic and intermodulation distortion caused by magnetic traces left by previous cycle 



    Q: Should I go with this 4 ohm or with the 8 ohm version?

    A: Both woofers have similar distortion performance and the T/S parameters are alike. The 4 ohm coils of this PTT6.5X04-NFA-01 allows more current to flow on a similar drive voltage. This gives a higher sensitivity and is preferred in most applications. If you have an amplifier that is not comfortable with low impedance loads or have specific requirements, such as parallel woofers, the PTT6.5X08-NFA-01 might be more favorable. 


    Q: Why is this surround odd shaped?

    A: This is the PURIFI Natural Surround. Conventional surrounds create distortion as they deform. The shape of the Natural Surround reduces cone edge resonances and distortion. It might be odd looking, but form follows function here. A more detailed look shows that the surround actually represents complex sound wave. We are told that the Natural Surround is also called ‘wormy’ by insiders. 


    Article number
    Woofer Series
    Woofer Type
    Nominal Diameter
    Power Handling (RMS)
    250 watts
    Power Handling (max)
    Continuous Program Power
    80 watts
    Impedance (Z)
    4 ohms
    88.7 dB @ 2.83V/1m
    Frequency Response
    Voice Coil Diameter
    39 mm
    Magnet Weight
    DC Resistance (Re)
    3.7 ohms
    Voice Coil Inductance (Le)
    0.38 mH @ 1kHz
    Resonant Frequency (Fs)
    30 Hz
    Mechanical Q (Qms)
    Electromagnetic Q (Qes)
    Total Q (Qts)
    Diaphragm Mass Inc. Airload (Mms)
    26.7 g
    Moving Mass Of Diaphragm (Mmd)
    Mechanical Compliance of Suspension (Cms)
    1.04 mm/N
    Surface Area of Cone (Sd)
    132.7 cm²
    Volume of Displacement (Vd)
    132.7 cm³
    BL Product (BL)
    Compliance Equivalent Volume (Vas)
    25.9 liter
    Maximum Linear Excursion (Xmax)
    10 mm
    Driver's Mechanical Losses (Rms)
    0.88 kg/s
    Cone / Diaphragm Material
    Proprietary Fibre Mix
    Surround Material
    Nitrile rubber
    Voice Coil Wire Material
    Voice Coil Former
    Dual Voice Coil
    Basket / Frame Material
    Aluminum alloy diecast
    Magnet Material
    Overall Outside Diameter
    176 mm
    Overall Depth
    90.2 mm
    Baffle Cutout Diameter
    145 mm
    Bolt Circle Diameter
    166 mm
    # Mounting Holes
    Mounting Hole Diameter
    5.1 mm
    Sealed Volume
    Sealed F3
    Vented Volume
    Vented F3


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    PTT6.5X04-NFA-01 6.5″ Ultra Low Distortion Long Stroke Driver 4 Ohm
    € 305,74
    € 369,95
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    PTT6.5X04-NFA-01 (PTT6.5W04)
    >10 In stock: delivery time 1-4 business days
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