Was addressing filters in general. Altec made passive line level units, as did others, mostly a caution for folks using any of them.
BTW 600 isn't a standard value, 610 used to be. 620 is readily available.
Better to be slightly on the high side than low side.
Your neighbors called. They like your music.
might find some things in here -
AmericanRadioHistory.Com - Documenting the History of Radio TV and FM broadcasting
guns kill people,
like spoons made rush limbaugh,
fat ....
I only read the article once, but I like the idea of a passive line level crossover and it looks simple enough that even I, a novice in electronics should be able to solder up. Is there enough info in the article to design a 1000hz crossover? I can't do the math, but my son is a physicist, so I assume he can.
"James, a little knowledge is a dangerous thing!" World's scariest Volvo: [url]http://www.youtube.com/watch?v=AKn-LTNa4rc[/url]
Unless you're going to do it right with an output transformer or an active buffer / make-up gain section, you may as well go with a normal active two-way crossover a la Rane AC22 which is trivially inexpensive second hand and less expensive than a single high-quality transformer.Originally Posted by VolvoHeretic
I only read the article once, but I like the idea of a passive line level crossover and it looks simple enough that even I, a novice in electronics should be able to solder up. Is there enough info in the article to design a 1000hz crossover? I can't do the math, but my son is a physicist, so I assume he can.
It's worth noting that input impedance specifications particularly on solid-state electronics are nominal and assume a very low impedance and non-reactive output feeding said input. Unless you've got the schematics on-hand or are willing to measure, you won't have much clue on reactance at the input (coupling capacitors, for instance) and its attendent effect on your crossover point.
BobR
- - - Updated - - -
Good advice.
It was trivial to use passive units in spite of their inaccuracy and generally bad phase characteristics when inputs and outputs and the entire world were 600 ohm transformer-coupled; they definitely won't perform as advertised otherwise.
BobR
As Bob said, actives are cheap, but for some, DIY is the way to go..for instance Rod Elliot has a bunch of stuff on his site...
Linkwitz-Riley Electronic Crossover
Your neighbors called. They like your music.
I should have figured that that article was just to good sounding to be true. My buddy, the "Electrical Engineer Genius" said he could build me a passive line level crossover for $8 with just a capacitor and resistor over a year ago, and that an active crossover was a waste of money, but I am still waiting.
"James, a little knowledge is a dangerous thing!" World's scariest Volvo: [url]http://www.youtube.com/watch?v=AKn-LTNa4rc[/url]
They're called FMODS.I should have figured that that article was just to good sounding to be true. My buddy, the "Electrical Engineer Genius" said he could build me a passive line level crossover for $8 with just a capacitor and resistor over a year ago, and that an active crossover was a waste of money, but I am still waiting.
FMODS
Comparing them to an active crossover would be like comparing a bicycle to a fine Italian sports car.
While your genius friend may have a great understanding of electricity in general, he apparently has little understanding of the complexity of an audio signal, or the reactivity of audio components. The folks that make the FMODS simply ignore a lot that might otherwise undermine their marketing.
Not all vegetables make good leaders.
So,to ask the next question, has anyone used simulation software to check the veracity of the circuit I posted? You gotta remember when it was designed ,using relatively standard methods. I don't think it could get much simpler. I did look at the L-R blurb on Elliots web pages, and it seems his thoughts are well respected. Is one really going to hear, say a 3 db differenced at the crossover point knowing full well that most speakers can't spec their entire range inside of 3 db?
This was simple, had few parts, had to deal with only small voltages instead of lots of power, and I don't think there is any preamp out there worth its salt that can't handle a 3 db insertion loss. ???
Think this thru some more...as has been said that circuit will be affected by what it's hooked to...how can you sim it?
Answer is you can not. You could sim for ONE combination, which would be useless for others.
Your neighbors called. They like your music.
No one has performed any calculation because there is no point.
I mentioned that passive networks like this were designed in the era of 600 ohm termination which optimally used transformers for impedance matching (max power transfer), isolation and - most importantly in this instance of tuning a L-C circuit - ensuring that the target bandpass / bandstop frequencies are met.
This circuit uses resistive termination without buffering (isolation) which is NEVER recommended and will NEVER meet target -3 dB points in real circuits. In other words, it won't work.
Thankfully we live in a world where solid-state electronics offer low output / incredibly high input impedances and we have finally moved away from power (0 dBm = 1 mW into 600 ohms) to simple, scalar voltage (0 dBu = 0.775 V) reference for equipment interface. And we have finally dispensed with obscenely expensive phase-altering transformers!
His thoughts are well respected because they are based on solid audio engineering principle.I did look at the L-R blurb on Elliots web pages, and it seems his thoughts are well respected.
Depends on where (frequency) and over how broad a range (bandwidth) this 3 dB difference is -- please study the psychoacoustic concept of Equal Loudness (Fletcher-Munson / Equal Loudness Curves).Is one really going to hear, say a 3 db differenced at the crossover point knowing full well that most speakers can't spec their entire range inside of 3 db?
But in general, yes, a 3 dB difference - particularly in the midband where most crossovers are designed to operate - is audible.
Yes it is simple because there are critical features missing. Without an exact load or buffering/transformer isolation from outside reactances, this design will not work as intended.This was simple, had few parts, had to deal with only small voltages instead of lots of power, and I don't think there is any preamp out there worth its salt that can't handle a 3 db insertion loss. ???
And never mind the insertion loss; it is the poor transfer function (frequency and phase response alteration) that is objectionable.
BobR
Last edited by joyspring; March 7th, 2015 at 10:13 PM. Reason: grammar (subject-predicate agreement), spelling, etc. errors
Bookmarks