Howdy all, I have a home audio project issue that's a bit esoteric, but thought maybe someone here could point me the right way.
I have a subwoofer in my AV system, the Vandersteen 2wQ, an overall solid performer. This is not for a LFE channel, but rather offloads the low-end from my stereo front mains (a rebuilt pair of Dahlquist DQ-10's that really need the help even more than the Vandy's I originally bought the sub for). It connects to the power amp output terminals for my mains, and, this is the important part, requires a high-pass filter to be connected to the power amp inputs.
Filters are theoretically available from Vandersteen, but these range from dubious quality (I have a pair of X-2's I've been using) to ludicrously priced (the M5-HP, an adjustable crossover designed for one of their higher-end speakers, is both hard to acquire and costs nearly as much as the subwoofer). The filter itself needs to be matched to the input impedance of the amplifier, which usually means getting new filters if you change your system.
There was some discussion several years ago, mainly on the Planar Audio (I think) forum, about these filters being a fairly simple DIY project, though the details are a bit sketchy. I'm still pretty handy with a soldering iron, but the last filter I built was out of a cookbook in school some twenty years ago, so I'm a little rusty on the theory.
As far as I know, I need to make a first-order (-6dB/octave) high pass filter with a crossover frequency as close to 80Hz as I can get. Getting from theory to the workbench raises a couple of questions for me:
1) For a standard (unbalanced RCA-cable) hookup, I believe all that I have to do is connect a "high quality" capacitor to the hot lead of each of my pre-out/main-in cables. Let's pretend I can do the math to get the right capacitance I need (it's a function of the input impedance of the amp), as calculators are pretty easy to find online. Is that all I need? Some posts also refer to linking a resistor in parallel to the input, but I don't think this is right.
1a) For that matter, anyone have an opinion on what constitutes a "high-quality" cap? I've seen some brand names dropped (Auricaps, Teflon V-caps), but spending hundreds of dollars to trial-and-error different brands defeats some of the DIY purpose.
1b) I doubt I can find a cap that will map out to a crossover at exactly 80Hz, and using multiple caps seems needlessly messy. Knowing the right answer is "try different values and see what sounds right," see 1a, I'm going to assume that a cut off a little lower (like 73Hz) is better than too high (90-100Hz).
1c) Incidentally, when picking a cap, how important to me is the voltage rating of the cap? A lot of the ones I've seen are 600V. Is this reasonable for an audio application? Way higher than needed? Going to melt when I crank the volume?
2) I'm planning to replace both my amp (a Dunlap-Clarke Dreadnought c.1973 that's a monster, but way past it's mandatory retirement age) and my processor, with a new system that supports balanced (XLR) hookups. This means new filters (the unbalanced and the balanced are not interchangeable -- some of why I don't want to spend a ton of money on the factory filters). I don't have a lot of experience with XLR cables. What do I have to do different? Is it as simple as using two caps, one for each hot lead? What value caps do I use (one post said implied half of the capacitance of the single cap in the unbalanced hookup). Is there more to this one? Is working with XLR beyond what is reasonable to DIY?
If anyone out there has experience with the 2wQ's, or at least enough knowledge of circuits to tell me I'm doing it right, I'd love to hear from you.
I have a subwoofer in my AV system, the Vandersteen 2wQ, an overall solid performer. This is not for a LFE channel, but rather offloads the low-end from my stereo front mains (a rebuilt pair of Dahlquist DQ-10's that really need the help even more than the Vandy's I originally bought the sub for). It connects to the power amp output terminals for my mains, and, this is the important part, requires a high-pass filter to be connected to the power amp inputs.
Filters are theoretically available from Vandersteen, but these range from dubious quality (I have a pair of X-2's I've been using) to ludicrously priced (the M5-HP, an adjustable crossover designed for one of their higher-end speakers, is both hard to acquire and costs nearly as much as the subwoofer). The filter itself needs to be matched to the input impedance of the amplifier, which usually means getting new filters if you change your system.
There was some discussion several years ago, mainly on the Planar Audio (I think) forum, about these filters being a fairly simple DIY project, though the details are a bit sketchy. I'm still pretty handy with a soldering iron, but the last filter I built was out of a cookbook in school some twenty years ago, so I'm a little rusty on the theory.
As far as I know, I need to make a first-order (-6dB/octave) high pass filter with a crossover frequency as close to 80Hz as I can get. Getting from theory to the workbench raises a couple of questions for me:
1) For a standard (unbalanced RCA-cable) hookup, I believe all that I have to do is connect a "high quality" capacitor to the hot lead of each of my pre-out/main-in cables. Let's pretend I can do the math to get the right capacitance I need (it's a function of the input impedance of the amp), as calculators are pretty easy to find online. Is that all I need? Some posts also refer to linking a resistor in parallel to the input, but I don't think this is right.
1a) For that matter, anyone have an opinion on what constitutes a "high-quality" cap? I've seen some brand names dropped (Auricaps, Teflon V-caps), but spending hundreds of dollars to trial-and-error different brands defeats some of the DIY purpose.
1b) I doubt I can find a cap that will map out to a crossover at exactly 80Hz, and using multiple caps seems needlessly messy. Knowing the right answer is "try different values and see what sounds right," see 1a, I'm going to assume that a cut off a little lower (like 73Hz) is better than too high (90-100Hz).
1c) Incidentally, when picking a cap, how important to me is the voltage rating of the cap? A lot of the ones I've seen are 600V. Is this reasonable for an audio application? Way higher than needed? Going to melt when I crank the volume?
2) I'm planning to replace both my amp (a Dunlap-Clarke Dreadnought c.1973 that's a monster, but way past it's mandatory retirement age) and my processor, with a new system that supports balanced (XLR) hookups. This means new filters (the unbalanced and the balanced are not interchangeable -- some of why I don't want to spend a ton of money on the factory filters). I don't have a lot of experience with XLR cables. What do I have to do different? Is it as simple as using two caps, one for each hot lead? What value caps do I use (one post said implied half of the capacitance of the single cap in the unbalanced hookup). Is there more to this one? Is working with XLR beyond what is reasonable to DIY?
If anyone out there has experience with the 2wQ's, or at least enough knowledge of circuits to tell me I'm doing it right, I'd love to hear from you.