I'm using the drivers in my ATC SCM20 Pro PSL Mk2 studio monitors for a project. Most notably I'm making them active and lowering the crossover point for best power response and dispersion. I may need to make a new enclosure to reach the desired woofer q and the lower tweeter crossover point. The thought occurred to me: I have two Kef Kube 10b subwoofers which I bought to fill in the low end. I could integrate their drivers and amp in the new enclosure!
Originally my idea was to spend under $2,000 on subwoofers instead of another $15,000-$20,000 to move up the product line to the next best options: SCM50s or 100s (it seemed like the financially responsible thing to do lol). The SCM50s have a 9 inch woofer, the 100s have 12.
The Kef Kube 10b is a 10 inch sealed subwoofer. It's 300w RMS, low end -3db point of 24hz, maximum output 111dB, ~35L enclosure. Ideally I would have bought the next size up (12" with same amp), but they weren't in stock or on the same ~35% off sale. Their -3db point is 21hz and I assume they would move 50% more air or so. They'd have made the woofer in the monitors the limiting factor in all music genres, but whatever, can't have everything.
A problem I have is, the subwoofer's low pass filter is 4th order, and the sealed woofer roll-off is 2nd - they don't match. Lowering the sub's level a bit and moving it's crossover up a few Hz kind of compensates for this, but isn't ideal. If I'm going to put both systems in the same box, I want perfect integration.
Keeping fidelity and price in mind, what's the best way to fix this? I assume to extend the low end in the 35 liter enclosure, DSP of some kind is used. The driver will bottom out quite easily at some frequencies, so I think the included DSP isn't especially discriminating re: how much peak power it sends to the woofer at various frequencies. On the rear there are two pots and a switch. The switch is 0deg 180deg and "Corner". I think corner shelves the very low end from the mid 30hz range. Pot 1 is frequency from 40hz to 140hz, pot 2 is level. There's RCA and speaker level inputs. I prefer RCA because I get hum with some amps at speaker level.
I'm using all four channels of my RME Babyface Pro's interface as the woofer and tweeter preamp, so I'm wondering how I can make these subwoofers behave the way I want them to. I don't want to spend too much (the speakers and subs cost enough lol) - free is always best.
The woofer in the SCM20s is an underhung design and can move either 10 or 12mm without distorting (20mm gap and 8 or 10mm coil, not entirely sure). Its diameter is 5.4 inches if you include 1/3 of the surround on both sides. I just measured the resonant frequency of it in its 20 liter enclosure, and found it to be 53.5hz. The -6db point of the system is advertised to be 55hz (which to my ears is right). The datasheet for the woofer says its resonant frequency is 57hz though, so I'm a bit confused... Isn't the resonant frequency of a woofer in a sealed box supposed to be higher than it is on an infinite baffle? If it's 53.5 in the box, how low would it be in free air? Mid 40hz range?
For compatibility, below I used 10mm peak to peak linear travel and 5.1 inch diameters for the cone. Peak undistorted amplitude at different frequencies:
70hz - 95.0db
75hz - 96.5db
80hz - 97.5db
85hz - 98.5db
90hz - 99.5db
95hz - 100.5db
100hz - 101.5db
The natural rolloff starts at about 80hz.
The subwoofer's maximum output is said to be 111db. The woofer is high excursion, so I'll estimate xmax is 10mm, peak to peak: 20mm
62hz is the lowest frequency which 111db can be reached.
at 50hz 107db can be reached
at 40hz 103db can be reached
at 30hz 98db can be reached
at 20hz 91db can be reached
I was thinking of using the natural filter of the woofer in it's box for high pass. Reasons being: for ease of implementation and to maximize its contribution to the signal. There's obviously a difference in quality between the drivers and amplification (though I think a properly designed high current class d amp is more than good enough for bass). I think a midwoofer with the same motor as the one used in speakers costing as much as cars should be used as much as possible before switching. Unless the excursions would be severely mismatched. Do the frequencies and outputs above look like they'd work well together - well enough to put them into the same enclosure?
Originally my idea was to spend under $2,000 on subwoofers instead of another $15,000-$20,000 to move up the product line to the next best options: SCM50s or 100s (it seemed like the financially responsible thing to do lol). The SCM50s have a 9 inch woofer, the 100s have 12.
The Kef Kube 10b is a 10 inch sealed subwoofer. It's 300w RMS, low end -3db point of 24hz, maximum output 111dB, ~35L enclosure. Ideally I would have bought the next size up (12" with same amp), but they weren't in stock or on the same ~35% off sale. Their -3db point is 21hz and I assume they would move 50% more air or so. They'd have made the woofer in the monitors the limiting factor in all music genres, but whatever, can't have everything.
A problem I have is, the subwoofer's low pass filter is 4th order, and the sealed woofer roll-off is 2nd - they don't match. Lowering the sub's level a bit and moving it's crossover up a few Hz kind of compensates for this, but isn't ideal. If I'm going to put both systems in the same box, I want perfect integration.
Keeping fidelity and price in mind, what's the best way to fix this? I assume to extend the low end in the 35 liter enclosure, DSP of some kind is used. The driver will bottom out quite easily at some frequencies, so I think the included DSP isn't especially discriminating re: how much peak power it sends to the woofer at various frequencies. On the rear there are two pots and a switch. The switch is 0deg 180deg and "Corner". I think corner shelves the very low end from the mid 30hz range. Pot 1 is frequency from 40hz to 140hz, pot 2 is level. There's RCA and speaker level inputs. I prefer RCA because I get hum with some amps at speaker level.
I'm using all four channels of my RME Babyface Pro's interface as the woofer and tweeter preamp, so I'm wondering how I can make these subwoofers behave the way I want them to. I don't want to spend too much (the speakers and subs cost enough lol) - free is always best.
The woofer in the SCM20s is an underhung design and can move either 10 or 12mm without distorting (20mm gap and 8 or 10mm coil, not entirely sure). Its diameter is 5.4 inches if you include 1/3 of the surround on both sides. I just measured the resonant frequency of it in its 20 liter enclosure, and found it to be 53.5hz. The -6db point of the system is advertised to be 55hz (which to my ears is right). The datasheet for the woofer says its resonant frequency is 57hz though, so I'm a bit confused... Isn't the resonant frequency of a woofer in a sealed box supposed to be higher than it is on an infinite baffle? If it's 53.5 in the box, how low would it be in free air? Mid 40hz range?
For compatibility, below I used 10mm peak to peak linear travel and 5.1 inch diameters for the cone. Peak undistorted amplitude at different frequencies:
70hz - 95.0db
75hz - 96.5db
80hz - 97.5db
85hz - 98.5db
90hz - 99.5db
95hz - 100.5db
100hz - 101.5db
The natural rolloff starts at about 80hz.
The subwoofer's maximum output is said to be 111db. The woofer is high excursion, so I'll estimate xmax is 10mm, peak to peak: 20mm
62hz is the lowest frequency which 111db can be reached.
at 50hz 107db can be reached
at 40hz 103db can be reached
at 30hz 98db can be reached
at 20hz 91db can be reached
I was thinking of using the natural filter of the woofer in it's box for high pass. Reasons being: for ease of implementation and to maximize its contribution to the signal. There's obviously a difference in quality between the drivers and amplification (though I think a properly designed high current class d amp is more than good enough for bass). I think a midwoofer with the same motor as the one used in speakers costing as much as cars should be used as much as possible before switching. Unless the excursions would be severely mismatched. Do the frequencies and outputs above look like they'd work well together - well enough to put them into the same enclosure?