mulling over crossover questions. Wayne? Anybody? [message #42837] |
Thu, 30 October 2003 05:09 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Triodeuser
Messages: 4 Registered: May 2009
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Esquire |
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I'm using Azura's that use 8" full range drivers and are beyond loading by the horn around 1500 hz. Also, 1250hz is about where 8" drivers begin beaming. I also have DDS Eng 90-1 constant directivity waveguides that will cover from about 1100 up with 1" compression drivers. Conceptually, my goals are to match and blend as many aspects here as possible while keeping crossover point above the vocal range, also paying particular attention to dispersion at crossover. Right now I'm thinking that what I want to occur is that as the Azura's begin to beam, I want the waveguide to start taking over. Initially, I had been thinking that I would do a first order crossover at a much higher point - say 4k or so, but have been told that was very difficult to do well, due to the 3db/octave rolloff characteristics of CD waveguides. I don't know that it matters, and I don't see what I could do about it anyhow, but from center to center of the horns will be about 29" apart - one reason I think I have to be sure I do it right. So where and how do you think I should start planning my crossover? Regards Ken L
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Re: A few useful documents [message #42843 is a reply to message #42840] |
Thu, 30 October 2003 12:04 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Chris R
Messages: 133 Registered: May 2009
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Master |
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Hi Wayne, I'm looking at the Lab Circuits at the Pi-over, and the only thing not shown is the amount of attenuation you are getting. I'm assuming its the 8:25, but I've forgotten how to translate that to dB. Is it 5dB? 10*log(25/8)? Also, how does one go about picking values for different attenuations? On another note, from Ray Alden's book that RatShack sells, he provides formulas for attenuation that leaves the total load equal to the original driver. Its a series resistor and one parallel to the driver. I suppose it wouldn't lend itself to the HF comp. you use. Comments? I've included the perl code if anyone cares.Chris ./atten.pl -8 driver Z: [8.00] ohms Series resistor: [4.82] ohms Parallel resistor: [5.29] ohms #!/usr/bin/perl -w
if ( ! @ARGV ) { $drop = -6; # dB } else { $drop = shift(@ARGV); } $driver_Z = 8; # ohms # split the load between the driver and the resistor $Rp = (10 ** ($drop / 20 )) * ($driver_Z/(1 - (10 ** ($drop / 20 )))); # calc the the combined impeadance of driver and parallel # resistor, and subtract from original Z. $Rs = $driver_Z - ( 1 / ( ( 1/$Rp ) + (1/$driver_Z ))); printf(" driver Z: [%3.2f] ohms\n Series resistor: [%3.2f] ohms\n Parallel resistor: [%3.2f] ohms\n",$driver_Z,$Rs,$Rp);
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thanks [message #42847 is a reply to message #42840] |
Thu, 30 October 2003 15:42 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Triodeuser
Messages: 4 Registered: May 2009
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Esquire |
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I will review them. I've read thru the crossover document and some of the other stuff. I regret to say that I no longer seem to have the ability to process that sort of info as well as I used to. Reading thru again may help clarify it somewhat. regards Ken L
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Re: A few useful documents [message #42873 is a reply to message #42840] |
Sat, 01 November 2003 12:53 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Chris R
Messages: 133 Registered: May 2009
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Master |
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Hi Wayne, Not to complain, because you are so generous with such good info, but the spice.zip install seems to be broken. On two different computers, when I run aimsp32.exe, it tries to install the previous program I installed instead of Spice. Any idea what's going on? On the first one, I even when hunting for setup.exe from the last installed program and deleted that. No help. I think WinZip is common between the two, FWIW.The on-topic question I had is about the crossovers. Doesn't including a significant series resistor alter the crossover frequency of the cap(s) and coil? The reason I ask is that you've suggested in the past that the Eminence 1.6K crossovers are OK to use along with the HF comp components verses making up the whole x-over by hand. Thx, Chris
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Re: A few useful documents [message #42889 is a reply to message #42874] |
Mon, 03 November 2003 18:59 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Chris R
Messages: 133 Registered: May 2009
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Master |
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Hi Wayne, I found the culprit setup.exe under Docs&Settings/userID/temp. Once I deleted that, the installer actually ran the right setup.exe. I love Windows.... NOT! How does one go about creating a Spice model of their drivers? It seems to be something about making an RC tank circuit that resonates at Fs, but aren't there a range of values that return the same center freq? And how does Zmax fit into the picture? Thx, Chris
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Re: A few useful documents [message #42891 is a reply to message #42889] |
Mon, 03 November 2003 20:55 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) |
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Wayne Parham
Messages: 18748 Registered: January 2001
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Illuminati (33rd Degree) |
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Glad to hear you figured out your problem with Spice. I hate little "gotcha's" like that. You can chase 'em for hours.About making a virtual circuit that models mechanical resonance, the idea is to find parallel L,C and R that acts as the mechanical resonator does. R will be set by Zmax, so that one is easy. Then, the values of C and L will be the same at resonance, and since Q is the ratio of reactive impedance to resistive impedance, you will find a the value of inductor and capacitor with reactances equal to Zmax / Qms at Fr.
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