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In Reply to: Maggies and active crossovers posted by slownlo on November 19, 2006 at 15:45:52:
A standard Linkwitz-Riley 4th-order slope crossover sums electrically to something quite a bit different than the stock crossover of a 1.6. Yes, you've made an improvement with regards to direct drive and all the benefits associated with that, but you've also changed the engineering of the system considerably as well. This should result in a noticeably boosted midrange. Time will tell if you ultimately like this tonal balance.It's just not as simple as removing the passive crossover and inserting active crossover...insert brand here...into the mix.
Cheers,
Follow Ups:
No it's not as simple, but you should always be able to get a "better" sound. In designing a passive crossover the engineer is limited by the impedance characteristics of the drivers themselves, often resulting in compromize solutions the produce audible artifacts in directional pressure or intensity response. Davey, you might be right in that those "artifacts" might be the defining nature of the loudspeaker's sound. with a flexible crossover/eq you can "restore" or even improve on the sound in the "Nice" realm before current amplification.
Well, passive crossover design for a Maggie is somewhat simpler than a conventional speaker because the impedances involved are resistive in nature. I wouldn't say a designer is "limited" by the impedance, but it certainly has to be incorporated into the design. For a line-level crossover you really don't have to consider it.Ultimately, the shape of the electrical slopes driving the transducers produces the final output. My point was that.....in the case of the 1.6.....the electrical slopes for the stock network are completely different than those produced by a generic active crossover with LR24 slopes. A comparison of active and passive in that case is really not valid. It's apples and oranges.
Cheers,
"Ultimately, the shape of the electrical slopes driving the transducers produces the final output."You need to keep in mind the acoustic output at the listening position. While the impedance may be flat, acoustic output is often not flat in the crossover region. If you look at the standard crossovers (particularly 2 ways), from an electrical standpoint, there would be a significant dip in the crossover region. However, this dip disappears at the listening position due to the acoustic output of the drivers. Creating flat frequency response either requires adjusting the crossover slopes or equalization (which would essentially accomplish the same thing- reducing output in the crossover region).
I am emphasizing "at the listening position" because of the dispersion characteristics of the panels, the dipole configuration and the fact that they tend to have significantly different response when close mic’ed.
When I started doing passive DIY crossovers, I didn't take output into consideration (just impedance curves) and they often sounded horrible. It took a lot of trial and error to figure out what I was doing and get them right.
Yes, obviously the electrical slopes may not sum flat....in fact they almost always don't. Unless some sort of generic crossover is used like mentioned in this thread. Sorry if I didn't make that clear enough in my statement.However, acoustic output should sum flat in the crossover region...at least on the design axis. However, as you noted, with large transducer speaker systems close miked measurements are not that useful.
It's possible that a designer might try to optimize for a more even off-axis performance at the expense of on-axis response, but you don't see that done very often.Cheers,
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