The 10-incher

This is from an email I had written on 29 July 2004 to Angshu, copying the data I found in the badly photocopied sheets from Jeetubhai. This pertains to the 10" woofer. Don't know whether this is the big-magnet one or the small-magnet one:

    The Peerless S25NL-8 AKA SKP254:

    Nominal Z:      8  ohms
    Fs:             26 Hz
    Nom power:      85 Watts
    Sens:           92 dB/W/m

    VC dia:         40 mm
    VC height:      14 mm
    Air gap ht:      8 mm
    Magnet wt:      (unreadable)
    Mag dims:       120x20 mm, dia x ht

    DC res (Re):            5.8 ohms
    Compliance (Cms):       1.08 m/N
    Moving mass (Mms):      33.3 g
    Qms:                    2.31
    Qes:                    0.45
    Qts:                    0.38
    VAS:                    not specified, a Peerless habit
    Piston area (S):        363 sq-cm
    Force factor (Bl):      8.47

The five-and-a-quarter-incher

This is from a mail I had written on 2 Aug 2004, about the 5.25" driver:

    Interesting fundaes and info. Will reply more later, but here's the
    parameters of the SKO 130, AKA S13NL-8 (or is it S13NI-8?).

    Nominal imp (Z):                 8 Ohm
    Resonance freq (Fs):            53 Hz
    Nom power handling:             50 W
    Sens:                           90 dB/W/m

    Voice coil dia:                 26 mm
    VC height:                      12 mm
    Air gap:                         5 mm
    Mag dimension (d x h):          86 x 15 mm

    DC resistance (Re):              5.7 Ohm
    Compliance (Cms):                1.05 m/N
    Moving mass (Mms):               8.5  g
    Qms:                             2.00
    Qes:                             0.46
    Qts:                             0.38
    Piston area:                    95 sqcm
    Force factor (Bl):               5.93

    As usual, no VAS.

    It has a stamped powder coated chassis, a polymer coated paper cone, and
    a rubber surround.

I remeber buying two of these 5.25" drivers just to see what they "sound" like and measure like. I had done T/S parameter measurements to see the Fs... I was curious to see whether they could be used as midbass units in small TM bookshelf speakers. I liked the sound, it was nice and smooth, like good paper cones, I guess. But the Fs was too high: about 80Hz. The GR-Research drivers had Fs of 40Hz, thus could do reasonable duty as midbass units. However, the Peerless India drivers can be used as lovely midranges extending down to 100-120Hz, or as midbass units in sat-sub configurations where the region below 100Hz would be taken care of by subwoofers.

Here is the extract from a mail dated 4 Nov 2005, where I documented the measured T/S parameters I got from measuring the two samples:

    Here they are for one of the two drivers (the two match closely):

    Fs:             80.7Hz
    Qts:            0.506
    Qes:            0.633
    Qms:            2.526
    Le:             0.292mH
    Re:             5.8 Ohm
    SD:             95 sq-cm

    And I've attached the impedance plots for the two samples I have.

I can see from my old notes that I did not bother to measure Vas for the drivers. This seems reasonable since Vas measurement is a separate activity, and is much more trouble than the rest of the measurements put together, and Vas is only needed if you want to design an enclosure size for the driver, which I won't be doing for a driver which stops at 80.7Hz.

Hope all this helps someone today.

next: Another MTM built using these drivers