steve_1979 said:
lindsayt said:
Instead of coming up with any sort of answer to what I have written ...
With all due respect all of your previous comments clearly show you've totally failed to understand this point:
Re: Passive speakers
"for no sound to come out a driver, the passive crossover must effectively disconnect the amp from it. The impedance seen by the amp starts to rise from a few hundred Hz. It is this action, far more than the resistance of the inductors, that reduces damping right through the range and dramatically."
Re: Active speakers
"In an active design, the crossover doesn't use lossy and distortion introducing inductors and it is placed before the power amp, which remains permanently connected to the driver and maintaining maximum damping/control over its entire operating range."
lindsayt said:
... the 3 of you have focused on insulting me personally.
Me? I've said nothing personally insulting about you. Nor would I.
A heated debate is all good fun IMO and best not to be taken too seriously. But if I've said anything that's actually caused you genuine offence then I apologize.
Steve, I fully understand the totally MISLEADING nature of the two paragraphs you have quoted.
I have already given a partial explanation as to why they are misleading in my previous posts in this thread, including #35 #89 and #93.
Is there anything in those posts that you disagree with? Is there anything that you don't understand in those posts? (Please please please play the ball here (with the "ball" being posts #35, #75, #89 & #93). Please don't play the man).
The active vs passive debate ineveitably leads onto discussions about speaker design - which is a complex subject full of swings and roundabouts compromises.
At this point I want to re-state my position on actives vs passives. Which is: in some scenarios actives will sound overall better, in others passive will sound overall better.
Let's dissect Ashley James MISLEADING statement "re: Passive speakers"
Remember this circuit diagram from #89:
The amplifier output is not shown in this diagram. It's connected to the terminals on the left.
Please note that the midrange unit and treble units are wired in paralled with the bass units.
Ashley James said "for no sound to come out a driver, the passive crossover must effectively
disconnect the amp from it". Disconnect is not the word I would use to describe what's happening in the most appropriate manner.
The reality of what's happening is that as the frequency rises, inparticular above the crossover frequency of 400hz, the reactance of inductor L1 increases. We can calculate by how much by using this tool (that I mentioned in #89) http://www.electronics2000.co.uk/calc/reactance-calculator.php
So that for my 1.58mH L1 inductor:
At 400 hz: 4 ohms reactance
At 800 hz: 8 ohms
At 1600 hz: 16 ohms
At 3200 hz: 31.8 ohms
What this means is that as the electricity coming from the amp increases in frequency, it will be increasingly
directed to the midrange unit. Directed because the midrange unit is wired in parallel. And because electricity will flow most via the path of least resistance.
OK we could say that the amp has been disconnected from the bass unit at higher frequencies. But the trouble with that is that it implies something bad is happening, because disconnection implies a lack of control and control is generally a good thing. The reality is that all that's happening is that less electricity is going to the bass unit and more is going to the midrange unit at these higher frequencies. After all, that is what we want!
Something else that we need to remember is that the bass drivers will have a natural fall off in output as the frequency rises. This is something that anyone can test by wiring an amp directly to a bass driver and playing full range music through it (please never do the same test with midrange units or tweeters as there's an extremely high chance you will break them).
So that at 1600 hz, for example, my bass cones are receiving little electricity (thank to L1) and are converting an extremely low amount of that electricity to sound (thanks to the natural roll off in efficiency of that driver as frequencies rise).
Ashley James said "The impedance seen by the amp starts to rise from a few hundred Hz". It is true that the impedance / reactance of the bass driver part of the circuit rises from a few hundred HZ. But, because we have midrange units / tweeters wired in parallel, the impedance seen by the amp will be largely dependent on the impedance of the midrange / tweeter part of the speaker circuit.
"It is this action, far more than the resistance of the inductors, that reduces damping right through the range and dramatically."
The Wikipedia entry on damping factor says: "In loudspeaker systems, the value of the damping factor between a particular loudspeaker and a particular amplifier describes the ability of the amplifier to control undesirable movement of the speaker cone near the resonant frequency of the speaker system. It is usually used in the context of low-frequency driver behavior, and especially so in the case of electrodynamic drivers, which use a magnetic motor to generate the forces which move the diaphragm."
It is unimportant if we have a high electrical damping factor way outside the resonant frequency of the speaker - eg 120 hz and above on my bass units. Why? Because at those frequencies the speaker cone will have it's own natural mechanical damping (I will be happy to discuss damping and spring effects on bass cones in another post).
I will address the MISLEADING statements made by Ashley James on Active Crossovers in another post.