diffuser material Color Coated Cellulose Suspension material Foamed polyurethane basket material Steel magnet material Ferrite Voice coil, inches/cm 2" (5.08 cm) Overall diameter, mm 213 Mounting diameter, mm 182 Mounting depth, mm 107 Weight 5 KG SQ FROM WHERE THEY DID NOT EXPECT. PART THREE SWAT MAS-8 8" subwoofer speaker test Here one often sees statements saying that SWAT and SQ are incompatible things. What can I say ... who does not see further than the nameplate, they can continue to think so. And who looks at the real properties of things - this test will definitely be useful. Because in reality with this speaker you can save a lot, but get a compact and unexpectedly musical subwoofer that plays much more than its price. I dismantled its features, tried it in action, share the results. FIRST ACQUAINTANCE, DESIGN FEATURES Appearance, as it were, hints - this is not an overgrown midbass, this is a full-fledged subwoofer. The landing depth of the speaker is 10.7 cm. Assembled on a stamped steel basket - quite rigid and, moreover, completely devoid of sonority. With this combination of proportions and dimensions, it generally turned out to be comparable to cast baskets. Let's write it down as a plus. The central cap is made of plastic, the cone of the diffuser is made of dense pressed cellulose with a polymer coating on the front side. In bending, the cone turned out to be unexpectedly rigid, although with such proportions this was expected. The upper suspension has a High Roll profile - narrow and high. It allows a large stroke, but the useful area of the diffuser "eats" to a minimum. The lower suspension (well, or a centering washer, if you like) is with a progressive profile, i.e. the pitch and height of the waves increase as they move away from the center. This usually avoids mechanical resonances outside the subwoofer range and thus reduces bass coloration. Such things, by the way, are usually clearly shown by measurements, but more on that later. The motor is assembled on a 2-inch voice coil. The description does not give the internal geometry of the motor, but the winding appears to be out of the gap by about 1 cm. In this case, the height of the upper washer of the magnetic circuit is 7 mm - in this case, it is she who determines the height of the gap. The result was a compromise - a linear stroke of about 2 cm from edge to edge without the coil leaving the gap (for an 8-inch subwoofer, sufficient travel is relevant), without losing the ability of the motor to be controlled by the amplifier. A delicate balance, however. Coil cooling is traditional - through the windows under the centering washer and the decompression axial channel. MEASUREMENT OF PARAMETERS AND ANALYSIS OF WORK The repeatability of the parameters is good - the description in the calculations can be trusted. The mass of movement is definitely not like that of mid-bass speakers, and will even give odds to other 10-inch models. In theory, this should have greatly reduced the resonant frequency. But the center washer is stiff (which is indicated by the small value of Vas), and this tends to increase resonance. As a result, we again have a compromise: a typical value for 8-inch subs is slightly above 40 Hz. It's normal - the speaker does not climb into the fierce infrabass, but the informative "meat" bass works out (this was later confirmed by experiments). Declared / actual parameters SWAT MAS-8: Fs (natural resonant frequency) - 43 Hz / 45 Hz Vas (equivalent volume) - 6.5 L / 6.4 L Qms (mechanical quality factor) - n. d. / 7.18 Qes (electric quality factor) - n. d. / 0.53 Qts (full quality factor) - 0.45 / 0.49 Mms (effective mass of the moving system) - n. d. / 91 g BL (electromechanical coupling factor) – n. d. / 13.2 T m Re (DC resistance) - n. / 3.4 ohm dBspl (reference sensitivity, 1m, 1W) - 82.4 dB / 83.5 dB There are no resonances of the centering washer, a small hump in the region of 700 Hz most likely gives the central cap. Although it doesn’t do much weather - it’s too insignificant for the bass to acquire “color” (other more expensive subs have seen more). Distortion is moderate: the 3% mark is exceeded only below 30 Hz - for an 8-inch caliber it looks decent. Moreover, the picture almost does not change even with an increase in volume up to a stroke of 15 mm from edge to edge. Of course, when installed in the case, an elastic “air cushion” will make its own adjustments, but at least there are no complaints about the linearity of the motor itself. CALCULATION OF ACOUSTIC DESIGN AND TRIAL IN PRACTICE The description offers two housing options for the SWAT MAS-8 - sealed 8 liters and ported 12 liters with a 37 Hz port. As for the sealed, it is acceptable, and there is no need to be afraid of a low resulting quality factor - the test in the case clearly showed this (I will talk about this a little later). Bass-reflex design is also quite possible, and there is one caveat. The calculation program shows the maximum return below 40 Hz. But no, not only. If you make a slotted port, then with the resulting proportions, the air mass inside it will be slightly overdamped. In other words, the character of the bass will be closer to WL than to PHI. And also, as an option, you can try ported with a “clean” volume of 10 liters and also a slotted port, but tuned a little higher. TRIAL IN ACTION I confess that I was very surprised by the result - the small SWAT managed to give out a delicious, tight and resilient bass, pushing in the chest like a concert. And in the case, which, I'm sure, many did not even consider as optimal for this speaker. In general, in order. For experiments, I took my usual test box, reduced its volume to about 10 liters (initially I have more of it, so I threw it with foam blocks). I fixed the speaker in it and took the whole thing to the car. Connected instead of my usual subwoofer. Why in such a case with such a resulting quality factor did the bass turn out to be unexpectedly “delicious”? In fact, there is no discrepancy between practice and theory. Once again, I repeat that there is no need to be afraid of a low quality factor in the subwoofer link. Much is decided, including the internal geometry of the motor. In addition, pay attention to the equivalent volume of Vas. It is small, which indicates a fairly rigid centering washer - it also “helps” the motor to keep the diffuser from exceeding the stroke. In other words, the dynamics do not give a damn about the case, but for normal operation it is not particularly sensitive to the elastic air support of the air enclosed inside the case. Plus, the motor itself is far from weak here and also keeps the diffuser from loosening. Putting it all together, it comes very close to the concept of a proper free-air subwoofer. As the saying goes, the stars aligned. BRIEFLY TO THE POINT A very successful and extremely inexpensive speaker for SQ systems from a brand that many do not associate with SQ. Allows you to build a very compact, but musical subwoofer with tight, "concert" bass. With a good amplifier, it won't give up even before a fast bass drum or a frenzied bass guitar on aggressive rock and metal, not to mention simpler genres. Usually I try to refrain from subjectivity, but here, I'll be frank, that's just gone. Rigid basket, completely devoid of sonority Good repeatability of parameters (including warm-up) You can build a compact, but very musical sub Capable of tight, resilient "concert" bass, pushing in the chest Loyal to the volume of AP, allows small deviations from the calculated
