![]() If the second one can run from 12-15 Volts I would like to make that one, I suppose. Now that I think about it I don't know what resistors or capacitors to get either lol Will the "safety" resistor the second link recommends be sufficient to send the right amount of current to this circuit? Also I looked on (not sure if this is the best place to get these parts) and they had 113 different kinds of TL082 OP amps and I don't know which one to get. But then again the last one does say that it operates between 12-15 Volts, are they all like this? It is important to me since I will want to wire this probably where my head unit is in my car. I would want for the -3 db point to start at around 18 Hz, I think, and I'm not sure the last one does. Which suggests that simple calculation is not indicative of the amplifier's control over the cone.Īlso being old enough to have only had analogue tape or vinyl sources, cone flap was not considered out of the ordinary.Here are links to three different subsonic filters: SUBSONIC FILTER - Circuit Diagram - Forum - Subsonic / Rumble Filter for Phono preamps and Sub-Woofers Subsonic Filter ![]() I once connected a DC coupled amp to a drive unit and tapped the cone and then repeated it after disconnecting the amp. Back emf is the release of inductor energy once the drive has been removed, but as the amplifier is now driving in the opposite direction the maths will be a little more complex, and a factor of 4 might be a long way off. I say common knowledge because some rubbish the whole idea of damping factor. It's always a good idea to do a lot of research before buying, but some manufacturers don't give the full details these days.Īnd therefore I should remark that the Proprius also has sod-all damping factorīased on common knowledge it is around 4 at 20Hz. Then again, Chris says these are designed using amps with a stiff driving impedance. Reflex "loading" allows the driver to resonate (pump) at its resonant frequency and a complete lack of damping will allow large cone excursions, but I would have thought the manufacturer would have taken that into consideration so as not to "bottom out" on its suspension. Slope of filter 6dB/octave.Īgreed, damping factor (or should we call it driving impedance?) isn't much from an output transformer, and as such "sod all" is appropriate wording. Replacing the grilles would remove that annoyance, and not cost anything. However, to get the cross feed a large number of op-amp stages are required to do the subtraction and summing and so the resulting sound might not be as good.Ĭone flap should not damage well made speakers, and if so it would only be of visual annoyance. I beg to differ on that, because some early stereo records have the bassists over to one side or another.Īnyway, as bass is less directional and the "cross feed" circuit doesn't result in phase differences within audibility (which your filter does), then it looks like a better idea. ![]() Purists may argue that it makes the lows mono, which isn't a good thing, but we are told that records are cut with mono bass below 300Hz anyway. This cross feeds the bass from around 150Hz and below and cancels the lateral differences from the cartridge where the rumble, we are told, comes from. If a 1Meg valve amp input the parallel combination will be 70k, and the turnover frequency only slightly higher at 22.74Hz.Īt the other extreme of say a 22k input solid state, the parallel combination will be 17k, and the turnover frequency much higher at 93.6Hz.Īnother much more complex way of doing it would be to use the channel subtract and sum method which has been doing the rounds since 1979 (see: ). By how much depends on the input impedance of the amp (or preamp etc). The values give a high pass filter which turns over at 21.22Hz (-3dB), but when the load of the amp it is driving is taken into consideration, the 75k will not be 75k, it will be less. Why should I be upset with you for doing this? ![]()
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