I'm going to incorporate a Dayton SD215-88 ( http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-480 ) into a portable boombox. I'm going to power the DVC sub with a 2 channel amp. I dont have any impedance plot except for the Dayton provided one. I'm wanting to cross it over at around 200hz @ 12dB. Can anybody help me out? How close could I get by using the Dayton provided impedance curve?
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Pretty close once you add a zobel to flatten it, but the 3.75 ohm non-inductive power resistor and 85 - 88 uF cap's going to be kind of large to fit in a boombox, not to mention make it run hot, so a line level XO seems a better choice: http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
GM
Pretty close once you add a zobel to flatten it, but the 3.75 ohm non-inductive power resistor and 85 - 88 uF cap's going to be kind of large to fit in a boombox, not to mention make it run hot, so a line level XO seems a better choice: http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
GM
Well, passive filters at 200 Hz is often problematic due to the impedance curve of the driver. Below is an example of a cookbook filter (green curve) and what happens when it is applied to the complex load of the driver. When the values are "fiddled" a bit, it looks a bit better (blue curve).
I think this highlights the need for simulations when designing passive filters
. The impedance of the blue system is probably too low to be useful, though.
An externally hosted image should be here but it was not working when we last tested it.
I think this highlights the need for simulations when designing passive filters
. The impedance of the blue system is probably too low to be useful, though.
GuyPanico said:
You pick R1 and R2 as a compromise between insertion loss and the impedance your preamp sees. You need to know your preamp's output impedance, and your amplifiers input impedance, too get an idea of how much wiggle room you have.
For example, if your amplifier's input impedance is 100kohms, then your above filter would result in about 3db insertion loss. If the input impedance is 10kohms, then insertion loss is closer to 11db. As you reduce R2, insertion loss gets smaller, but so does R1.
Since R1 is the lowest impedance the preamp will see, you can't reduce it forever. I think 10x output impedance is a minimum, but hopefully someone with more knowledge than I will chime in with a better answer.
Dan
I'm in planning stage of similar project. Planning to use a DVC sub woofer. Was going to use active filter but concerned about Power supply. Going to run car radio with ac power supply. An active filter would require another amp and would be considerable challenge to power supply.
See if this helps. http://www.apicsllc.com/apics/Misc/filter2.html
See if this helps. http://www.apicsllc.com/apics/Misc/filter2.html
Maybe I wasn't clear. The project is a portable boom box. Based on car stereo which will give me FM, CD, and external inputs such as MP3 player.
Plan to use AC power instead of battery. Tho, a batery could be used if no power available.
Am now considering a matched component system and be done with it.
Like this
Or never had any kids , my daughter was pestering me to make/buy her one at least 30 yrs ago. Anyway, portable stereo system: http://www.secure-internet-store.com/products/product-view.asp?prodID=5769
GM
, my daughter was pestering me to make/buy her one at least 30 yrs ago. Anyway, portable stereo system: http://www.secure-internet-store.com/products/product-view.asp?prodID=5769GM
The thing is, for not a great deal more than the list price, I think I can build something with much more power and better sound that will have an aux input for my and other's MP3 players.
BTW, I'm 62. Maybe I AM too young for this project.
The project is for Beer and BBQ parties. Not to be carried around!
BTW, I'm 62. Maybe I AM too young for this project.
The project is for Beer and BBQ parties. Not to be carried around!
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