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Get familiar with the reaction system: Introducing the Reaction System
Radio Shack 40-1024A
So, pair of NOS Radio Shack 8" woofers showed up at my doorstep today.
As I am a huge fan of the appearance of older drivers, I find them very attractive with their semi-gloss, dimpled, black poly cone and treated fabric dustcap.
Pretty basic motor and construction - no voice coil venting to be seen. The foam is perfect condition, as are the mounting gaskets.
These were taken after ten minutes at 40Hz, at about +/-4mm excursion. Relatively quiet operation, given the free-air environment and lack of venting.
I would consider these a "true" acoustic suspension design, versus, say - a GRS 8" equivalent.
In the above chart, the light gray line is the Radio Shack driver which modeled with a Q of 0.85 or so, with F3/6/10 of 55/45/35 or so. The GRS models at 57/48/40 with a peak on the bottom end. The ripple on the RS driver is barely noticeable.
One hallmark of good AS style drivers is the ability to play low in a small box:
Here is the RS in 15 liters, Q is still at 1 (which is not at all objectionable IMHO), and while F3 is up to 68 - F6 and F10 are still respectable at 56/45. This means in as small as 1/2 cubic foot and boundary loaded, this will probably be flat to the low 40's in a typical living room or home office, with additional usable output into the 30's.
Most drivers today advertised as "acoustic suspension" are actually just high Q, cheap drivers. AS used to mean something, it meant a driver with a moderately high Qts, low Fs, and very high compliance - note the Vas on the RS driver is nearly 50 liters!!!
As I am a huge fan of the appearance of older drivers, I find them very attractive with their semi-gloss, dimpled, black poly cone and treated fabric dustcap.
Pretty basic motor and construction - no voice coil venting to be seen. The foam is perfect condition, as are the mounting gaskets.
Loudspeaker parameters:
Fs = 40.37 Hz
Re = 6.80 ohms[dc]
Le = 348.98 uH
L2 = 531.99 uH
R2 = 18.27 ohms
Qt = 0.61
Qes = 0.71
Qms = 4.36
Mms = 20.29 grams
Rms = 1.179327 kg/s
Cms = 0.000766 m/N
Vas = 49.18 liters
Sd= 213.82 cm^2
Bl = 7.002735 Tm
ETA = 0.44 %
Lp(2.83V/1m) = 89.21 dB
Added Mass Method:
Added mass = 20.00 grams
Diameter= 16.50 cm
These were taken after ten minutes at 40Hz, at about +/-4mm excursion. Relatively quiet operation, given the free-air environment and lack of venting.
I would consider these a "true" acoustic suspension design, versus, say - a GRS 8" equivalent.
In the above chart, the light gray line is the Radio Shack driver which modeled with a Q of 0.85 or so, with F3/6/10 of 55/45/35 or so. The GRS models at 57/48/40 with a peak on the bottom end. The ripple on the RS driver is barely noticeable.
One hallmark of good AS style drivers is the ability to play low in a small box:
Here is the RS in 15 liters, Q is still at 1 (which is not at all objectionable IMHO), and while F3 is up to 68 - F6 and F10 are still respectable at 56/45. This means in as small as 1/2 cubic foot and boundary loaded, this will probably be flat to the low 40's in a typical living room or home office, with additional usable output into the 30's.
Most drivers today advertised as "acoustic suspension" are actually just high Q, cheap drivers. AS used to mean something, it meant a driver with a moderately high Qts, low Fs, and very high compliance - note the Vas on the RS driver is nearly 50 liters!!!
I have a signature.
Comments
Those are real beauties. Nice score.