sbhattac@rnd.gba.nyu.edu (Shankar Bhattacharyya) (09/18/90)
Here are numbers for closed box alignments for a few drivers which look like
good candidates for home made woofers. Separately, I will also post the
numbers on a bunch of drivers which looked decent at first glance, but
did not look so good when I worked them through.
The numbers were generated by a C program of about 20 lines of code, the
guts being in about 5 lines. Since there may well be errors in my code, I
suggest that you check numbers out before you believe them completely. I
posted formulae earlier.
If anyone finds errors, please let me know. I should track down bugs in my
code. Perhaps some woofer sophisticates would check some numbers? I would
appreciate that, as, I am sure would anyone who might use these numbers.
Some of the Q's were entered to 3 sig. figures, incidentally.
I looked at every woofer in the Madisound and Audio Concepts catalogues,
chossing those which looked like they had acceptable EBP (not too far from
50).
Those are the only current ones I have. There are obviously other drivers
out there. I tried to stick to drivers with polymer cones (much more
rugged, and possibly better able to work as a rigid piston). With one or
two exceptions, I have tried to avoid vastly expensive drivers. Dynaudio
and Eton drivers are very highly regarded, so I have included some of
those, including a couple which cost over $200 just by themselves.
Finally, I have tried to restrict myself to drivers which are capable of
producing serious amounts of bass in a closed box alignment. So I have
stayed away from 6" drivers and other such things. Most of these drivers
are 10" or 12" units. There are a couple of smaller ones.
This article has the drivers which show promise.
The Audio Concepts AC-10 and AC-12 look far better than anything else I
have seen from either the Audio Concepts or Madisound catalogues.
All frequencies are in hertz, volumes in liters.
For convenience:
1 liter = 61 cu in
1 cu ft = 28.3 liters
Dynaudio 24W100 $ 110 looks good, but expensive, for a small system
Qts = 0.35, Vas = 132.00, Fs = 23.0, Qes = 0.45, EBP = 51.11
qtc alpha Vb Fc F3
(hz) (hz)
0.50 1.04 126.82 32.86 51.05
0.60 1.94 68.08 39.43 47.67
0.70 3.00 44.00 46.00 46.47
0.80 4.22 31.25 52.57 47.16
0.90 5.61 23.52 59.14 49.06
1.00 7.16 18.43 65.71 51.66
1.10 8.88 14.87 72.29 54.70
1.20 10.76 12.27 78.86 58.02
1.30 12.80 10.32 85.43 61.54
Dynaudio 30W54 $ 150 works very well with some bass boost
Xmax is less than I would like, but may be
Expensive, but conservatively stated. My 30W54 based
possible within woofer makes quite enough noise for me.
a budget of $200 Rolls Royce grade construction, excellent
rise time.
Qts = 0.36, Vas = 254.00, Fs = 22.0, Qes = 0.42, EBP = 52.38
qtc alpha Vb Fc F3
(hz) (hz)
0.50 0.96 264.15 30.81 47.88
0.60 1.82 139.20 36.97 44.71
0.70 2.84 89.29 43.14 43.58
0.80 4.02 63.16 49.30 44.23
0.90 5.36 47.43 55.46 46.00
1.00 6.85 37.10 61.62 48.45
1.10 8.49 29.90 67.79 51.30
1.20 10.30 24.66 73.95 54.41
1.30 12.26 20.72 80.11 57.71
Dynaudio 30W100 $ 240 looks quite promising; if you can accept a
Qtc of 1.2, with its attendant 2 db respone hump
Included because in the midbass, this is a hell of a driver.
people are inte- Rolls Royce grade construction, huge voice coil,
rested in Dynaudio excellent rise time.
Too expensive for
a budget woofer.
Qts = 0.62, Vas = 269.00, Fs = 24.0, Qes = 0.80, EBP = 30.00
qtc alpha Vb Fc F3
(hz) (hz)
0.50 requires non-positive box volume -- not feasible
0.60 requires non-positive box volume -- not feasible
0.70 0.28 964.73 27.14 27.42
0.80 0.67 401.30 31.02 27.83
0.90 1.11 241.47 34.89 28.94
1.00 1.61 167.09 38.77 30.48
1.10 2.16 124.66 42.65 32.27
1.20 2.76 97.53 46.53 34.24
1.30 3.41 78.87 50.40 36.31
Audio Concepts AC-10 $ 50 Looks very good. One of only a few drivers
of reasonable cost which will produce
Xmax = +/- 7mm F3 below 40 hz in a closed box without
bass boost. Excellent excursion. Among
10" woofers, this would probably be my
choice.
Qts = 0.44, Vas = 138.00, Fs = 23.0, Qes = 0.50, EBP = 46.00
qtc alpha Vb Fc F3
(hz) (hz)
0.50 0.29 473.70 26.14 40.61
0.60 0.86 160.56 31.36 37.92
0.70 1.53 90.14 36.59 36.97
0.80 2.31 59.85 41.82 37.52
0.90 3.18 43.34 47.05 39.02
1.00 4.17 33.13 52.27 41.09
1.10 5.25 26.29 57.50 43.51
1.20 6.44 21.44 62.73 46.16
1.30 7.73 17.85 67.95 48.95
Audio Concepts AC-12 $ 60 This looks stunningly promising. If I
were building a woofer today, this is what
Xmax = +/- 8 mm I would use. 30 hz, at respectable
excursion, without bass boost. The numbers
look much better than for the Dynaudios.
Qts = 0.43, Vas = 240.00, Fs = 18.0, Qes = 0.49, EBP = 36.73
qtc alpha Vb Fc F3
(hz) (hz)
0.50 0.35 681.66 20.93 32.52
0.60 0.95 253.43 25.12 30.37
0.70 1.65 145.45 29.30 29.60
0.80 2.46 97.51 33.49 30.04
0.90 3.38 70.99 37.67 31.25
1.00 4.41 54.44 41.86 32.91
1.10 5.54 43.29 46.05 34.85
1.20 6.79 35.36 50.23 36.96
1.30 8.14 29.48 54.42 39.20
Madisound 1252DVC (dual voice coil) $ 40
Looks quite promising, but I have no idea how I should deal
with the dual voice coil design. My numbers for this may be
entirely wrong. But not as promising as the AC-12, or even the
AC-10. Note the size required for Qtc=0.7. I would shoot for
Qtc=0.8 with this driver.
The Qts looks more suited for a vented box, but I think the
box would be quite large. If you can live with that, this
would produce very deep bass (guestimate; I haven't run the
numbers.
Qts = 0.36, Vas = 318.00, Fs = 19.0, Qes = 0.39, EBP = 48.72
qtc alpha Vb Fc F3
(hz) (hz)
0.50 0.93 342.30 26.39 41.00
0.60 1.78 178.88 31.67 38.29
0.70 2.78 114.35 36.94 37.32
0.80 3.94 80.75 42.22 37.88
0.90 5.25 60.57 47.50 39.40
1.00 6.72 47.35 52.78 41.49
1.10 8.34 38.15 58.06 43.93
1.20 10.11 31.45 63.33 46.60
1.30 12.04 26.41 68.61 49.42
Eclipse W1238R $ 50 Not bad, but I would prefer the AC-12.
As with the Madisound driver, the Qts
suggests a vented box, although the EBP, as
with the Madisound, looks rather low for
a vented box.
Qts = 0.33, Vas = 280.00, Fs = 19.0, Qes = 0.37, EBP = 51.35
qtc alpha Vb Fc F3
(hz) (hz)
0.50 1.30 216.10 28.79 44.73
0.60 2.31 121.43 34.55 41.77
0.70 3.50 80.01 40.30 40.72
0.80 4.88 57.41 46.06 41.32
0.90 6.44 43.49 51.82 42.98
1.00 8.18 34.22 57.58 45.26
1.10 10.11 27.69 63.33 47.93
1.20 12.22 22.91 69.09 50.84
1.30 14.52 19.29 74.85 53.92
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Shankar Bhattacharyya, Information Systems, New York University
sbhattac@rnd.gba.nyu.edu
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