I use them passive up to about 500Hz, active 4th order would be higher possible. The hickup at about 700Hz is not that hard in real live but I still try to avoid it and have at least some dampening/masking happening at that frequency.
This is the highest crossover point of my passive designs:
This is the highest crossover point of my passive designs:
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Revel used the SB Acoustics NBAC based drivers in their, now discontinued, Performa3 line. Rumor has it, the Performa4 line is to be released at the end of the year. It could be a coincidence SBA releases a new driver ahead of a new, somewhat significant, line of speakers.
A bit radical crossover of the woofer. 3rd order and notch. Electrolytics inevitable
This looks way better than I expected but the floor bounce is murder.
The standard drivers are 11mm (p-p) (voice Coil height - Gap height) as defined by the motor geometry:
Some slight changes of motor/coil results in what appears to be smaller 9.6mm p-p height.
But don't worry too much about this because at high excursion the main cause of distortion for this driver would have been Cms(x) 2.8mm according to
Erin’s Klippel's machine
https://www.erinsaudiocorner.com/driveunits/sbacoustics_sb17cac35-4/
but a more accurate explanation would be surround modulation distortion (Sd(x))
I see nothing to complain about here. It is very similar to the baseline SB17NRX but with a 2 dB increase in sensitivity and a little lower Xmax... a reasonable tradeoff. This will be a useful driver for some applications, as @tktran303 has mentioned.
It is nice to have options, and we should applaud every new driver that is introduced and available for DIY.
It is nice to have options, and we should applaud every new driver that is introduced and available for DIY.
mmh, the trick might be to give it some series resistance, in this case 1,5 ohm for two drivers in parallel:
The result looks then overall nice for a compact and crispy floorstander of such kind I had in mid some time ago:
Series resistance helps to get the impedance not too low for two drivers in parallel, and also introduces some local current feedback lowering thermal modulation and hysteresis distortion a bit; can also take cheaper coils with higher resistance / thinner wire then for the lowpass.
The result looks then overall nice for a compact and crispy floorstander of such kind I had in mid some time ago:
Series resistance helps to get the impedance not too low for two drivers in parallel, and also introduces some local current feedback lowering thermal modulation and hysteresis distortion a bit; can also take cheaper coils with higher resistance / thinner wire then for the lowpass.
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Additionally, this is the behavior at 20V amplifier voltage, with 75mm port diameter, 1,5 ohm series resistance. This is the theoretical system rail limit.
The excursion must be multiplied with sqrt(2) because it is a specifically of the Basta! tool to show the mean and not maximum excursion value.
You also see nice current feedback effect above 150-200Hz.
so well system sizing result is possible with these drivers!
The excursion must be multiplied with sqrt(2) because it is a specifically of the Basta! tool to show the mean and not maximum excursion value.
You also see nice current feedback effect above 150-200Hz.
so well system sizing result is possible with these drivers!
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If you're gonna use a lot of resistance in front of the drivers, raising qes and so on, can't you just use the original driver instead?
Did some simulations in the past with the original SB drivers for application as woofers in a slim passive floorstander together with a 5" Revelator mid an 1" dome; Similar enclosure volumes and vent tuning frequencies were applicable than in my approach above with the XL and series resistor.
But with 2 of the original drivers in parallel, sensitivity got too high for matching the mid and resistance got very low < 3 Ohm. Adding series resistance rised Qes too much for meaningful system sizing also with the volume and vent tuning. So I kicked the drivers out of the options.
The low Qes of the XL due to the fatter magnet "allows" now for adding series resistance: Sensitivity is then matching the mid, and impedance is > 5 ohms. Enclosure and vent is same, sim outcome looks overall even bit nicer with the XL.
Further benefits of the resistor:
1) Can take cheaper woofer series coils with thinner wire. Opens even the option to take air coils in series of the woofers instead of cored ones.
2) Local current feedback effect above >~150Hz that lowers current distortion and thermal compression a bit
3) Increased independency of amplifier damping factor behavior. Higher resistive fraction of impedance is easier load for the amp.
Costs: The resistor. But you can save probably more on the coil than pay for a Mundorf 20W bifillar wirewould.
A bit burned power on the resistor. But impedance between 50-100Hz is high, so not much loss at these frequencies.
But with 2 of the original drivers in parallel, sensitivity got too high for matching the mid and resistance got very low < 3 Ohm. Adding series resistance rised Qes too much for meaningful system sizing also with the volume and vent tuning. So I kicked the drivers out of the options.
The low Qes of the XL due to the fatter magnet "allows" now for adding series resistance: Sensitivity is then matching the mid, and impedance is > 5 ohms. Enclosure and vent is same, sim outcome looks overall even bit nicer with the XL.
Further benefits of the resistor:
1) Can take cheaper woofer series coils with thinner wire. Opens even the option to take air coils in series of the woofers instead of cored ones.
2) Local current feedback effect above >~150Hz that lowers current distortion and thermal compression a bit
3) Increased independency of amplifier damping factor behavior. Higher resistive fraction of impedance is easier load for the amp.
Costs: The resistor. But you can save probably more on the coil than pay for a Mundorf 20W bifillar wirewould.
A bit burned power on the resistor. But impedance between 50-100Hz is high, so not much loss at these frequencies.
Why don't make separat volumes for the lf drivers and push the first length resonance of the cabinet an octave higher? Way easier to deal with.
Well, 5.5mm vs 4.8mm is gonna give you an amazing 1.2dB extra!!!
Sensitivity is almost 3dB higher.
Looking at the other specs, seems like a more mid-range focused design.
But all depends how things are behaving, distortion etc etc.
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