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Multi-Way Conventional loudspeakers with crossovers

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Old 17th January 2013, 07:20 PM   #31
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L pad on tweeter only
notch filter on tweeter not necessary (particularly if you use a 2nd order xover)
this woofer needs a 2nd order xover
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

Last edited by PeteMcK; 17th January 2013 at 07:23 PM.
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Old 17th January 2013, 09:57 PM   #32
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Slightly off subject, the next level: Bi-Amping, and Why?

If you were to put an active crossover using opamps ahead of power amps for the crossover at 300HZ, you would have very good accuracy, very sharp cutoff rates (4th order), completely non-interactive level adjustments, and once you've got a chassis and power supply, active woofer EQ can be added with not much more trouble that will make a closed box (only) woofer be acoustically flat to practically any low end frequency you might want (20HZ, 30HZ etc.). Getting the large amount of cone movement required for good bass away from the midrange frequencies is one of the best improvements you can make in a speaker system. It causes audible doppler effect distortion (frequency modulation of the higher frequency energies). If heavy bass causes an amp to clip (overdrive), and the same amp is handling the whole frequency response, then every thing is horribly distorted.

My tri-amp'd system measures acoustically flat from 20HZ to 20kHZ +/- 2-3 dB at the couch (listening location), and it sounds really dam good, especially when kettle drums or bass drums are in the program source.

These days many video/movie soundtracks have lots of special effect energy below 40HZ, and it's quite a thrill if your system can handle it well. Circuits for active crossovers and woofer EQ can be grabbed off the web and scaled pretty easily, verified with a free version of the SPICE program (why re-invent the wheel - the actual math is very complex). If you decide down the road to take it up a notch, this may be what you'll be looking at. It seems like too big a project until you've seen what a time consuming pain in the rump it can be to get a passive crossover right.

Last edited by Bob Richards; 17th January 2013 at 10:01 PM.
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Old 17th January 2013, 10:08 PM   #33
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Bob that's a pretty big ask for a first project.
Mind you I agree that Bi-Amping is the best way to go for a cost effective solution below 120Hz or thereabouts
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Old 18th January 2013, 12:34 AM   #34
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Quote:
Originally Posted by Moondog55 View Post
Bob that's a pretty big ask for a first project.
Mind you I agree that Bi-Amping is the best way to go for a cost effective solution below 120Hz or thereabouts
That's why I started with "slightly off subject". I'm not recommending it at this point. Just wanted to give you a quick nutshell view of the what and why, perhaps for down the road. A simple passive speaker system is often a "gateway drug"... Pretty soon you're doing the hard stuff...
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Old 18th January 2013, 12:41 AM   #35
dijaam is offline dijaam  Australia
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Quote:
Originally Posted by Bob Richards View Post
My formulas are for 1st order only. Although a 2nd order between the woofer and mid is a great idea, I don't recommend it for a newbie since it's hard to get right without the ability to measure impedance of drivers at the frequencies in question. For the L-Pad, I was recommending a variable pot version of an L-Pad, not just two fixed resistors. That way you could adjust the tweeter level without throwing off the crossover function dramatically, as you would with a simple variable resistor.

Again, I haven't seen the specs on these drivers, and apparently they aren't very complete, and are therefore questionable all around IMO. When you consider the amount of time it takes to build speakers, it just doesn't make sense to use questionable drivers. Giving a newbie poor quality drivers for his first project is like giving a 15 yr old a really bad first guitar; it will likely teach him to never want to play guitar ever again.

Peerless and Dayton drivers are cheap and very good. I can recommend specific drivers if you'd like. If you can't do a project well... sometimes you're better off not to bother at all. Any advice we try to give you may not actually make it better in the end. Dealing with Baffle Step is a bit more advanced and not something a newbie is likely to get right. A Bass control on the preamp can largely make up for that.
Fair enough. Although to be honest I think id learn more building something to begin with and then be able to come back here and ask how I can improve certain parts after listening as opposed to just getting it right the first time or copying another design and never have to worry about it.. although the learning process might be different in speaker design, I dont know. it might just sound horrible and only be slightly better after fixing it ha!


Quote:
Originally Posted by Moondog55 View Post
Bob that's a pretty big ask for a first project.
Mind you I agree that Bi-Amping is the best way to go for a cost effective solution below 120Hz or thereabouts
Yeah im having enough trouble as it is haha..

Also, my amp has a 5-band eq on it so couldnt i just attempt a build as accurate as I can (using software with the specs im given) and just eq it to my room or come back here for suggestions to fix it? I think everybody is also overestimating how 'good' the finished product needs to be lol, Im building for a bit of fun mostly..

thanks guys
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Old 25th January 2013, 10:06 PM   #36
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So the little fullrange on ebay went for $56- did you bid on them?
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