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        PTT6.5W04-NFA-01 6.5″ Ultra Low Distortion Driver 4 Ohm

        PTT6.5W04-NFA-01 6.5″ Ultra Low Distortion Driver 4 Ohm


        PURIFI PTT6.5W04-NFA-01 6.5″ Ultra Low Distortion Driver 4 Ohm

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        Brand: PURIFI
        € 355,33€ 429,95 6 In stock
        • -10% Purchase 4 for only € 386,96 per piece
        • -15% Purchase 6 for only € 365,46 per piece

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        Product description

        The PTT6.5W04-NFA-01 is the standard stroke 6.5" bass-midwoofer from the PURIFI woofer family. It incorporates similar breakthrough technology, but due to a reduced excursion limit the efficiency is improved over the PTT6.5X04-NFA-01 long stroke woofer.



        • 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
        • Perfect balance between volume displacement and midrange efficiency


        Product Details

        PURIFI PTT6.5W04-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 PTT6.5W04-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, a long stroke version (PTT6.5X04-NFA-01) 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 PTT6.5W04-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 PTT6.5W04-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. 

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        Article number
        Nominal Diameter
        Power Handling (RMS)
        250 watts
        Continuous Program Power
        80 watts
        Impedance (Z)
        4 ohms
        Sensitivity (SPL at 1m / 2.83V)
        90.3 dB
        Voice Coil Diameter
        39 mm
        DC Resistance (Re)
        3.7 ohms
        Voice Coil Inductance (Le)
        0.32 mH @ 1kHz
        Resonant Frequency (Fs)
        33 Hz
        Mechanical Q (Qms)
        Electromagnetic Q (Qes)
        Total Q (Qts)
        Diaphragm Mass Inc. Airload (Mms)
        Mechanical Compliance of Suspension (Cms)
        1.10 mm/N
        Surface Area of Cone (Sd)
        132.7 cm2
        Volume of Displacement (Vd)
        78.3 cm3
        BL Product (BL)
        Compliance Equivalent Volume (Vas)
        28.9 liter
        Maximum Linear Excursion (Xmax)
        5.9 mm
        Driver's Mechanical Losses (Rms)
        0.7 kg/s
        Cone / Diaphragm Material
        Proprietary Fibre Mix
        Surround Material
        Nitrile rubber
        Voice Coil Wire Material
        Voice Coil Former
        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

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        PTT6.5W04-NFA-01 6.5″ Ultra Low Distortion Driver 4 Ohm
        € 355,33
        € 429,95
        PTT6.5W04-NFA-01 6.5″ Ultra Low Distortion Driver 4 Ohm
        6 In stock
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