34 replies to this topic

[abmolech]

Quote

lol i think i might stick to spl , all this active and passive crap is hurting my brain , ill go active on the weekend

bundy, you come from a background where measurement is more regarded than opinion. (SPL versus SQ)



Active has these measurable advantages.

1/ More efficient

2/ better noise rejection

3/ emulate anything a passive crossover can do and more.



Disadvantages

1/ You have to know more about crossover settings and drivers

2/ Less protection if something goes wrong with the settings (passive 12 dB and 24 dB slopes can take damage the other drivers on the circuit if they fail as well)

3/ Normally limited to "classic" passive crossovers (emulation)



Active crossovers have measurable advantages over passive crossovers, this is not in dispute, what is his peoples reaction to these differences.

[Hens]

What about stock passives? some speakers (even those higher end in the spectrum) have less then attractive stock passives.

[Roo]

ok anyone got a bit of a guide line on how to setup active?

i got DDC6.5 splits and a C4a

at the moment i got the woofers from 60hz to 3.5khz, tweeters from 3.5khz up. at the moment it sound nice but i think it can be better.

gains are on the down low amps not clipping.

just after abit of advice to get it sound really really nice

Roo

[abmolech]

Quote

ok anyone got a bit of a guide line on how to setup active?

I am not sure of your equipment capabilities.



Some basics why have crossovers?



Crossovers are normally filters. There is no reason that you could not use an equalizer to produce crossovers, so a crossover is a dedicated EQ. The crossovers most people will use, emulate a passive characteristics.The most common (read cheap) is a capacitor. This gives a 6 dB slope and a 90 degree phase shift. There are several ways of using an inductor(s) and capacitor(s) to create the following slopes.

12, 18 and 24 dB.

With an active crossover they often emulate these slopes.

These slopes give you an idea of how much they attenuate a drivers output. For example, a 24 dB slope is steeper than say a 12 dB slope, and the 24 dB is how much its maximum attenuation will be. IE if the driver is capable, it will keep playing this frequency, but at 24 dB less volume.



Point

Unless they are true brick wall crossovers (active) then the driver will keep playing all frequencies it is physically capable of but at a reduced SPL. For example a sub will often play up to 2 kHz (they are rated at 1 kHz, yep that efficiency rating)

A crossover therefore attenuates frequencies, while allowing others to pass through less attenuated, with the penalty of a phase shift, unless they are FIR filters.

The crossover is used to reduce mechanical failure of a driver. (Maximum loudness of a driver can be calculated, the limitation will be at the lowest frequency, the SPL required at the listening distance, and the volume of air it can physically move, that is cone area (SD) times xmax)

Aside from this limitation, a crossover is used to limit the bandwidth for which we wish the driver to play.

Know you mechanical limitation of your driver, and stay within a safety margin.



SPL (dB)= 100.3 + 20log(xmax) + 40log(D) + 40log(F) - 20log(L)

xmax=cone excursion
D=cone diameter (meters)
F=frequency (Hertz)
L=distance to listener from the driver (speaker) (meters)



Now that you have established the mechanical limit of your driver(s) then use 24 dB slope crossovers.

Use one driver only, and play your favorite songs. Listen for distortion, you may discover the driver distorts well before the mechanical limit or the "stated" frequency range of the marketers. Note this down, and rinse and repeat for other drivers. If your tweeter is capable of playing (without noticeable distortion), ideally you should try to get it to go as low as 2 kHz (most won't)

Why 2 kHz? It is the "zone of confusion" where your auditory system switches from time to intensity for location, it is also where most mids suffer from surround resonance, and if large enough diamtre, beaming. It is unfortunately a sensitive vocal area, so unless your tweeter is in close proximately to the mid you could be inviting trouble. Generally steeper crossover slopes are easier to align driver positions (more forgiving).

[/size]

Edited by abmolech, 03 May 2007 - 09:23 PM.

[Riley.]

when i get a mono im going semi-active

with the ESK's they have a seperate crossover for each driver.....so easily bi ampable...however they will run off the same amp

at the moment i get either midbass and hiss.....or nice sound with a lack of midbass