Hi there,
I have an 18" Mackie branded (but built by Eminence) driver laying around that I got off a friend a while ago. I would like to build a box for it to put it to use, and so I put the T/S parameters into WinISD. It defaulted to an absolutely massive 17.3 cubic foot box, which does not seem correct - or is it?
The parameters are as follows:
Re 3.20 Ohms fs 38.3 Hz
Le 0.72 mH Mms 145.5 grams
QM 8.03 Mmd 122.0 grams
QE 0.51 Cms 0.119 mm/N
QT 0.48 Rms 4.354 N*sec/m
Xmax 6.67 mm Vas 238.4 liters
Pmax 450 Watts SD 1188.0 cm^2
Bl 14.85 Tm VD 792.1 cm^3
Coil Diameter 4.00 Inches EBP 75.3
Gap Height 0.375 Inches Magnet Weight 109 ounces
Efficiency 2.54 % Winding Width 0.900 inches
SPL 96.1 dB 1W-1m
Could someone please tell me if i'm doing something wrong? Or would you recommend to just get a new driver.
Thanks,
Joe
I have an 18" Mackie branded (but built by Eminence) driver laying around that I got off a friend a while ago. I would like to build a box for it to put it to use, and so I put the T/S parameters into WinISD. It defaulted to an absolutely massive 17.3 cubic foot box, which does not seem correct - or is it?
The parameters are as follows:
Re 3.20 Ohms fs 38.3 Hz
Le 0.72 mH Mms 145.5 grams
QM 8.03 Mmd 122.0 grams
QE 0.51 Cms 0.119 mm/N
QT 0.48 Rms 4.354 N*sec/m
Xmax 6.67 mm Vas 238.4 liters
Pmax 450 Watts SD 1188.0 cm^2
Bl 14.85 Tm VD 792.1 cm^3
Coil Diameter 4.00 Inches EBP 75.3
Gap Height 0.375 Inches Magnet Weight 109 ounces
Efficiency 2.54 % Winding Width 0.900 inches
SPL 96.1 dB 1W-1m
Could someone please tell me if i'm doing something wrong? Or would you recommend to just get a new driver.
Thanks,
Joe
Greets!
Hmm, basic Margolis-Small T/S max flat vented box alignment formula:
Vb = 20*Vas*Qts'^3.3 = 659.06 L/23.275 ft^3
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor plus any added resistance from an XO/whatever.
So WinISD is apparently using one of the earlier formulas. Regardless, a max flat alignment is in theory when Vb = Vas, Fb = Fs, Qts' = ~0.403, so with a 0.48 Qt we see that it will be > Vas by a significant amount tuned somewhere below Fs for a max flat alignment.
What's it going to be used for, desired location and what's the max box size you can tolerate?
With only 6.67 mm Xmax, tuning < Fs won't allow much bass output unless there's sufficient room gain.
Hmm, basic Margolis-Small T/S max flat vented box alignment formula:
Vb = 20*Vas*Qts'^3.3 = 659.06 L/23.275 ft^3
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor plus any added resistance from an XO/whatever.
So WinISD is apparently using one of the earlier formulas. Regardless, a max flat alignment is in theory when Vb = Vas, Fb = Fs, Qts' = ~0.403, so with a 0.48 Qt we see that it will be > Vas by a significant amount tuned somewhere below Fs for a max flat alignment.
What's it going to be used for, desired location and what's the max box size you can tolerate?
With only 6.67 mm Xmax, tuning < Fs won't allow much bass output unless there's sufficient room gain.
