Here's three links for info on LspCAD.
Ingemar's home page
Liberty Instruments
Phil's Audio
You'll notice that there is a lower priced Standard version that has most of the same features and the Pro version.
For those that have had a chance to compare the two versions have you found the extra features invaluable or just convenient? I appreciate seeing pictures of projects done on LspCAD as it gives me a better point of reference as I pursue my own designs. Thanks!
Ingemar's home page
Liberty Instruments
Phil's Audio
You'll notice that there is a lower priced Standard version that has most of the same features and the Pro version.
For those that have had a chance to compare the two versions have you found the extra features invaluable or just convenient? I appreciate seeing pictures of projects done on LspCAD as it gives me a better point of reference as I pursue my own designs. Thanks!
Err.... octopus
Be prepared for major variations between design & actual performance with your crossovers due to component selection.
You seem to be using non-polarised electrolytic caps, with have high leakage and self inductance - ie their value varies considerably with frequency. Use polypropylene or polyester caps.
Cored coils, such as ferrite & steel, whilst being smaller & cheaper will introduce distortion - go for air-cored coils using heavy guage wire to reduce series resistance.
Then you may get close to predicted performance.
Cheers
Be prepared for major variations between design & actual performance with your crossovers due to component selection.
You seem to be using non-polarised electrolytic caps, with have high leakage and self inductance - ie their value varies considerably with frequency. Use polypropylene or polyester caps.
Cored coils, such as ferrite & steel, whilst being smaller & cheaper will introduce distortion - go for air-cored coils using heavy guage wire to reduce series resistance.
Then you may get close to predicted performance.
Cheers
Vivek said:
Hmmm......
I think I recognise those RicherSounds special cabinets.
Generally speaking a box volume of over Vas for most drivers is
a waste of opportunity. 71L is more than enough for two 7"
drivers if they are well chosen.
94 litres sounds like a lot to me for the cabinets I think you have.
47 litres per driver tuned to ~ 30Hz looks good for in-room response.
I'd suggest for you to use the box volume ideally you have two choices :
Build an MTM 2-way or 2.5way.
Or sealed box load the Vifa (22 litres) and build a
powered subwoofer into each cabinet, the driver
can be rear mounted to allow a larger size.
The MTM would be 4 ohm and high sensistivity.
The MT would be 8 ohm and lower sensisitivity
but with the stereo subs would have killer bass.
sreten.Re: bipolar electrolytics
I recently found out the hard way that complicated passive crossover networks may easily sound worse than a simpler network but with better components. I changed a 3nd order high-pass filter with mylar/polyester capacitors to a 2nd order filter with a polypropylene cap, and also replaced the mylar cap in the 3rd order low-pass filter with PP, and it sounds much better.
I thought that the increased driver overlap would muddy the sound, but quite the opposite happened and the sound is cleaner than ever. I don't attribute this to the crossover being simpler, but rather that each mylar cap adds a bit of distortion, and having 2 of them in series will be a lot worse than making the sound pass through one, superior capacitor.
Electrolytic caps are worse still. Unless I'm gravely mistaken, each "bipolar" cap is simply made from 2 separate capacitors in parallel and with opposite polarities. For a 3.3uF cap, it might actually be 3.45u in one direction and 3.15u in the other direction (a 5% tolerance is pretty good btw), while at low voltages things get messy and unpredictable. In other words, these sorts of caps are likely to produce one of the worst possible forms of distortion, similar to class-B amplifier distortion.
CM
I recently found out the hard way that complicated passive crossover networks may easily sound worse than a simpler network but with better components. I changed a 3nd order high-pass filter with mylar/polyester capacitors to a 2nd order filter with a polypropylene cap, and also replaced the mylar cap in the 3rd order low-pass filter with PP, and it sounds much better.
I thought that the increased driver overlap would muddy the sound, but quite the opposite happened and the sound is cleaner than ever. I don't attribute this to the crossover being simpler, but rather that each mylar cap adds a bit of distortion, and having 2 of them in series will be a lot worse than making the sound pass through one, superior capacitor.
Electrolytic caps are worse still. Unless I'm gravely mistaken, each "bipolar" cap is simply made from 2 separate capacitors in parallel and with opposite polarities. For a 3.3uF cap, it might actually be 3.45u in one direction and 3.15u in the other direction (a 5% tolerance is pretty good btw), while at low voltages things get messy and unpredictable. In other words, these sorts of caps are likely to produce one of the worst possible forms of distortion, similar to class-B amplifier distortion.
CM
Hi Sreten,
I have built two 90L boxes. I want to make it a TM system. You have suggested about 47L per driver. I can make two compartments in each box. One will be the 47L, the top half, and the bottom part can perhaps hold the crossover etc. What say?
Including the sub in the cabinets would have been good but I just built a 40L sealed sub for my HT receiver. The sub has two drivers mounted back to back.
Vivek
I have built two 90L boxes. I want to make it a TM system. You have suggested about 47L per driver. I can make two compartments in each box. One will be the 47L, the top half, and the bottom part can perhaps hold the crossover etc. What say?
Including the sub in the cabinets would have been good but I just built a 40L sealed sub for my HT receiver. The sub has two drivers mounted back to back.
Vivek
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