sedate wrote:
Ah hamfist.... asking *moi* for specific questions?
1-Headroom - Here you refer to absolute SPL?
2-No frequency drift - What is frequency drift?
3-Damping improves - Damping? Signal/Noise? huh? |
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Headroom is the difference in power required between the quietest passages and the loudest passages. The more headroom you have, the better your amplifier can handle the transients necessary to make your music more "lifelike". Without one 300WPC amplifier having to do a (relatively) HUGE portion of the spectrum, say 80 to 20K, you could use two somewhat smaller amps and split that wide range into smaller bands, for example 120 watts dedicated to 80 to 3500, and 45 watts dedicated to 3500 to 20K. Also, passive crossovers tend to smear transient response. i.e. "round-off" the sharp peaks required. You know, the stuff required to make a snare drum sound like a snare drum. Without requiring VERY high quality passive components in the crossover, you can use an active crossover instead. The op-amps in pretty much ANY active device will be faster than even the best quality passive components. I almost forgot... Yes absolute (peak, or transient) SPL is what headroom will affect directly. Average SPL *MIGHT* be better as well, but overall, the average is really determined by the capacity of your drivers. Frequency drift is what happens when your caps and coils change values (although it is a SLIGHT change) due to age and/or temperature. Damping is the back EMF from the voice coils being shorted against itself inside the amplifiers output devices. It improves because there is significantly less wire between the voice coil and the output terminals of the amplifier. Signal to noise is simply the sssssssssss you hear in the background between songs, or in quiet passages. The higher the S/N ratio, the less sssssssssss you hear.
sedate wrote:
"additional active crossovers" - okay, my understanding of an 'active' crossover is one, in the signal path, that provides output.. say, the xover on the amp or the xover on the HU. a 'passive' crossover is one that sits in the signal path and just cuts off something.. an external crossover or a bass-blocker or whatever. |
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They really both do the same thing, just in different physical places in the signal chain. Active is placed between the source (your HU or EQ) and the destination (the amp). It is actually considered a gain stage, and this is why it is so important to choose VERY carefully your active devices. A passive crossover, can be as simple as a capacitor in a tweeter lead, or a coil (inductor) in a woofer lead. A single device such as a cap or coil, will provide a 6dB slope, and you add more caps or coils in any combination of series and/or parallel, to increase the slope (or the order - each order adds 6dB. 1st-6dB, 2nd-12dB, 3rd-18dB and so on). When you get to higher order crossovers, especially low pass crossovers, the amount of wire in the inductors can be significant, thus reducing the amount of power available for your speaker system. The additional resistance also reduces the damping factor of the system.
sedate wrote:
So in this case "additional active crossovers" is a signal processor? My interest in this goes exactly as far as I need to move the crossovers in my car due to a horrible installation accident that I really don't wanna discuss here.... I'd really rather ditch them completely.. and I have this 6-channel amp.. soo. |
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The amp, I see, can be run as a 4 channel? Is this correct? 2X45 and 2X150? PERFECT! I have no idea how flexible the crossovers are inside the amp, but if you can set it to HP at 3500 or so (for the tweeters @ 45wpc), and LP at 3500 or so (for the mid-bass @ 150wpc), you'd be set. IF not, you need an external crossover - something like the Audio Control 6XS (adjusted by chips or resistors, and semi-fixed) or the Altomobile UCSPro (digital and INFINITELY flexible and adjustable). This will put you into a bit of an overpowered situation, so you would of course, need to be exceptionally careful in your use of the volume control...
sedate wrote:
Yea my most specific question goes like this: I wanna try bi-amping a set of JL Audio VR series midbasses with a set of CDT Audio 1" silk dome tweeters from the first 4 channels of a JL Audio e6450 b/c I think it would be really fun to do it. So tell me everything you possibly can about that.
http://www.jlaudio.com/amps/e6450.html |
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This amp won't do it in native mode. You'll simply HAVE to buy another croosver - an outboard one will be necessary.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."