RSS 390 HO 4 WinISD

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Hi, Does this look right to you? I expected more low end response:

Driver : Dayton Rss 390 HO 4
Vas : 167.9
Qts : 0.32
Fs : 21.50
SPL : 92.80
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Number of drivers : 1
Box type : Vented
Box size : 2.761 ft^3
Tuning frequency : 27.25 Hz
Vent : 1 vent(s)
13.27 in length for each
4.00 in round


Relative
Freq Gain SPL
[Hz] [dB] [dB]
20.00 -12.42 80.38
21.00 -11.05 81.75
22.00 -9.77 83.03
23.00 -8.58 84.22
24.00 -7.48 85.32
25.00 -6.48 86.32
26.00 -5.57 87.23
27.00 -4.75 88.05
28.00 -4.02 88.78
29.00 -3.38 89.42
30.00 -2.83 89.97
31.00 -2.36 90.44
32.00 -1.95 90.85
33.00 -1.62 91.18
34.00 -1.33 91.47
35.00 -1.10 91.70
36.00 -0.90 91.90
37.00 -0.74 92.06
38.00 -0.61 92.19
39.00 -0.51 92.29
40.00 -0.42 92.38
41.00 -0.35 92.45
42.00 -0.29 92.51
43.00 -0.25 92.55
44.00 -0.21 92.59
45.00 -0.18 92.62
46.00 -0.15 92.65
47.00 -0.13 92.67
48.00 -0.12 92.68
49.00 -0.10 92.70
50.00 -0.09 92.71
51.00 -0.08 92.72
52.00 -0.08 92.72
53.00 -0.07 92.73
54.00 -0.06 92.74
55.00 -0.06 92.74
56.00 -0.06 92.74
57.00 -0.06 92.74
58.00 -0.05 92.75
59.00 -0.05 92.75
60.00 -0.05 92.75
61.00 -0.05 92.75
62.00 -0.05 92.75
63.00 -0.05 92.75
64.00 -0.05 92.75
65.00 -0.05 92.75
66.00 -0.05 92.75
67.00 -0.05 92.75
68.00 -0.05 92.75
69.00 -0.04 92.76
70.00 -0.04 92.76
71.00 -0.04 92.76
72.00 -0.04 92.76
73.00 -0.04 92.76
74.00 -0.04 92.76
75.00 -0.04 92.76
76.00 -0.04 92.76
77.00 -0.04 92.76
78.00 -0.04 92.76
79.00 -0.04 92.76
80.00 -0.04 92.76
81.00 -0.04 92.76
82.00 -0.04 92.76
83.00 -0.04 92.76
84.00 -0.04 92.76
85.00 -0.04 92.76
86.00 -0.04 92.76
87.00 -0.04 92.76
88.00 -0.04 92.76
89.00 -0.04 92.76
90.00 -0.04 92.76
91.00 -0.04 92.76
92.00 -0.04 92.76
93.00 -0.04 92.76
94.00 -0.04 92.76
95.00 -0.04 92.76
96.00 -0.04 92.76
97.00 -0.04 92.76
98.00 -0.04 92.76
99.00 -0.04 92.76
100.00 -0.04 92.76
 

GM

Member
Joined 2003
0.32 Qts equates to very little bass output; add 2-3 ohms of series resistance and the net Vb will increase, tuning decrease, with more bass output relative to its higher harmonics [mid-bass], i.e. you're trading efficiency for a wider usable bandwidth.

GM
 
Hi, it's as it should be in that box !

Try it in a 120L box tuned to 25Hz as shown :)
 

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0.32 Qts equates to very little bass output; add 2-3 ohms of series resistance and the net Vb will increase, tuning decrease, with more bass output relative to its higher harmonics [mid-bass], i.e. you're trading efficiency for a wider usable bandwidth.

GM

A low Qts itself does not equate to low bass output and the OPs example is a case in point with flat response down to a 30Hz F3 in the box described above and even deeper in a larger box, shown as well. The ratio of Qts to Fs is what determines bass extension relative to midbass. In this case, the ratio does not quite provide home theater frequency range in an "optimally" flat alignment. As noted, a larger enclosure and deeper tuning can provide increased output in the 20-30Hz range with no need for other augmentation.

Also, while putting a 2-3 ohm resistor in series with a 4 ohm subwoofer will have some of the effects described, it's also a great way to start a house fire. With a relatively common 500W sub amp, the resistor could be required to dissipate over 100W and most readily available audio resistors are only rated to 25W or less. Sure, you can wire several resistors in parallel to accommodate this power requirement, but the fact that they aren't available in this value should tell you something about the practicality of this size resistor. There are much better ways to trade efficiency for bandwidth.

Dan
 
Tune to the lowest frequency you want to reproduce and equalize (EQ) the response back to flat. You will need EQ anyway for low frequency room correction. Keep in mind that decreasing box size and tuning frequency usually reduces efficiency down low.

Putting a resistor in series with a woofer is one way to apply crude EQ. It's cheap, though other ways like DSP are more efficient and flexible.
 
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