Goldwood GW-12PC/4 Thiele-Small & LMS Curve Data

 
Unit #1

Fs = 30.46 Hz
Qms = 5.145
Qes = 1.4530
Qts = 1.1330
Vas = 104.73 Liters
Cms = 2.782E-04 M/N
Re = 3.84 Ohms
BL = 7.045 N/A*
Sd = 0.051774 Sq. Meters
Mms = 0.098137 Kg
Ref Efficiency = 0.1958 %
Predicted Output = 85.117 dB/1W/1M
Predicted Sensitivity =  85.69 dB/2.00v/1M
(Predicted Sensitivity =  88.69 dB/2.83v/1M)**
Xmax = 3.55 mm (Goldwood’s figure)
Xmech = 16 mm p-p
Le = 1.84 mH

*Direct BL crosscheck = 7.025 N/A.

**LMS curve shows 200-300Hz output @  ~86.8 dB/2.83v/1M and
    sloping downward; output @ 550 Hz is down to ~83.7 dB, before
    it comes back up to approx. 85 dB around 1000Hz.  It rises to
    ~91 dB at approx. 1.9kHz, and then rolls off for good.)

Measurement conditions:
Broken in 12+ hours, Rest 12+ hours.
Temperature = 25.8° C,   Humidity = 68%

——————————————————————-

Unit #2 [retest] (Note 1)

Fs = 28.98 Hz
Qms = 4.549
Qes = 1.1391
Qts =  0.9110
Vas = 117.06 Liters
Cms = 3.109E-04 M/N
Re = 3.82 Ohms
BL = 7.696 N/A*
Sd = 0.051774 Sq. Meters
Mms = 0.096997 Kg
Ref Efficiency = 0.2404 %
Predicted Output = 86.008 dB/1W/1M
Predicted Sensitivity =  86.22 dB/2.83v/1M
(Predicted Sensitivity =  89.22 dB/2.83v/1M)**
Xmax = 3.55 mm (Goldwood’s figure)
Xmech = ~16 mm p-p
Le = 1.69 mH

*Direct BL crosscheck = 7.724 N/A.

**LMS curve shows 200-300Hz output @  ~88 dB/2.83v/1M and
   sloping downward; output @ 550 Hz is down to ~85 dB, before
   it comes back up to approx. 86 dB around 1000Hz.  It rises to
   ~92.5 dB at approx. 1.8kHz, and then rolls off for good.)

Measurement conditions:
Broken in 12+ hours, Rest 12+ hours.
Temperature = 25.6° C,   Humidity = 66%

(Note 1)  An initial test was run on this unit before it was broken
in:  Output was the same, Fs was 29.63 Hz, Vas = 108.32 liters,
Qts = 0.9594.

Curves

1/4 watt, 1/2 meter curves on Unit 1 and Unit 2:

(Click image to enlarge)

Near field curve* on Unit 1:
 
(Click image to enlarge)

*The microphone was placed directly in front of the dust cap, 1 cm “out” from a plane defined by the front surface of the driver’s front gasket.  The test box used is a quasi-ported design, and this curve shows only the woofer output, so response below ~100 Hz is not accurate.  The 700 Hz dip changes with near field mic position, and even “goes away” in some positions, such as near the roll.  This has us inclined to think the dip may be due to non-pistonic behavior of the cone body, and not (at least not mostly) due to a resonance in the roll.

Their T-S data (LOL):

 
Fs= 32 Hz
Qms= 3.85
Qes= .44
Qts= .39
Vas= 2.79 cu. ft.
Re= 3.7 ohms
SPL= 93 dB/2.83w/1m
Xmax= 3.55mm

What’s going on with the motor efficiency of the units we received is hard to say.  Evaluating the unit from what we can see externally, and making a few educated guesses, it seems at least possible that a driver like this could perform to Goldwood’s specifications.  The most likely explanation is that perhaps Goldwood’s mfgr. did not get these magnetized correctly.  Of course, that’s not a very positive commentary on the QC.

With a little fancy crossover work, these would appear to be useable with crossovers up to 2.3kHz or so, perhaps in a giant W-HMT-W cabinet, or maybe in an infinite baffle, at modest power? They’d certainly be for the “high Q crowd” in any normal size cabinet.

Other Goldwood data / info. on this driver (seems to be reasonably correct):

Power handling= 140 watts RMS/270 watts max
Voice coil diameter= 2.0″
Le= 1.7 mH
Frequency response= 32-2,000 Hz
Magnet weight= 50 oz.
Net weight= 9.6 lbs.
aluminum die-cast frame
knurled and gold-plated binding post
rubber surround,
vented pole piece with bumped back plate