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Why did crossovers end up in speakers, rather than preamps?

Discussion in 'classic' started by marshanp, Apr 2, 2021.

  1. marshanp

    marshanp ellipsis addict

    A line level signal is amplified full-range, then sent to a crossover where part of that amplified signal is deliberately filtered away for each driver.

    Which rather begs the question: Why bother amplifying a full-range signal? Why not filter it at line level first, so that amplification won't be wasted? It seems like a pretty obvious course of action to me...
  2. Jim Audiomisc

    Jim Audiomisc pfm Member

    TBH I often suspected they studied amp design in order to find ways to make that harder. 8-]
  3. Jim Audiomisc

    Jim Audiomisc pfm Member

    The problem in general is that the 'crossover' filters in speakers vary from one design to another in ways that are much more complex than one or two simple set of nth-order standard types. So in effect the 'amp' would need a DSP system that was given the recipy for this to suit in each case... and built to cover all the possible speaker designs the user might decide to use during the life of the amp. Plus, of course, needing multiple power amps per channel, not just one.

    Personally, it would be simpler and cheaper all round to tell the speaker designers to either sell active designs or get over the need to have their baby fed from a flat amp. 8-]

    That said, I was often tempted to lobby my MP for a law requiring all loudspeakers to have an input impedance that actually *was* 8 Ohms, resistive. 8-> Not an impedance that looked like the Alps when plotted against frequency and also varied with time and signal level.
    VanDerGraaf likes this.
  4. John Phillips

    John Phillips pfm Member

    Well, a loudspeaker-level crossover network will attenuate the power amplifier's output. In particular a low-pass section will usually have series inductor(s) which have some series resistance. It would not be unusual (from examples I have seen) for there to be 1.5 dB to 2 dB loss. So if (just for example) you wanted 100W to be available directly into the bass driver you would need an amplifier rated between 140W and 160 W.

    There are other issues which make designing a loudspeaker-level crossover network difficult, potentially inaccurate and maybe difficult to drive. But I have heard the active and passive versions of one loudspeaker and both performed very well indeed (including being easy to drive) so perhaps "strangles" is just a little too broad in this context.
    tuga likes this.
  5. Beobloke

    Beobloke pfm Member

    And me - that's why I use active speakers!

    But that's not to say that a well designed crossover cannot work very well. It's also a lot simpler and cheaper to implement.
  6. James

    James Lord of the Erg\o/s

    I resemble that statement!
    S-Man likes this.
  7. James

    James Lord of the Erg\o/s

    Unless the passive crossover is poorly designed, or designed to attenuate unmatched drivers, there is very little power loss. Inductors stay cold to the touch, resistors barely get warm and caps are totally unfussed. Beyond the stop band of each filter, current simply doesn't flow - so there is no waste of power - certainly not from the crossover. Drivers, on the other hand, can get pretty warm in their voice coils.
    S-Man likes this.
  8. foxwelljsly

    foxwelljsly Hawkwind and Fire

    A Linn exaktbox will take the place of most crossovers, but have to be partnered with compatible Linn Power amps, so I imagine would be the cost of a house in the north.
  9. audiopile

    audiopile pfm Member

    At one of the last Chicago CES shows (93?) I walked into the Meridian suite just as they started some piece of very dynamic classical music (it was last day of the show -so sales folks were punch drunk and /or hung over and volume levels almost everywhere had crept up near to pain). . The Meridians blew me away -they could do dynamic contrasts to shame a Klipsh corner horn and detail without shriek or honk -WOW. Then I looked at the price and gave up on the idea - didn't even tell my boss at the stereo store I worked at about them. So 25 years latter - i walk into a place that does mainly commercial sound installations to look over their room full of "stuff" -there sits 6 Meridian DSP-5000 speakers (5 working) , center channel and sub - no electronics -4 remotes .pay less than 10% of their price new. Couple of days later I make two trips back and forth -the DSP-5000 96/24 have been making music in my stereo system ever since -my pile of ancient n honorable old stereo amps have been sold off -and decades newer speakers sold for a substantial loss. Meridian has been making self powered speakers for decades and self powered with digital (DSP) crossovers for almost as long - because their older stuff doesn't have HDMI inputs -their surround stuff goes cheap (at least in the USA). While I will likely never use the sub or surround bits - this got me into the best speakers I have ever enjoyed in 50 plus years chasing the audio rainbow and did my dumpster diving soul a treat as well. Even at the reasonable higher prices of older Meridian equipment in the UK -if you are interested in getting a idea of what can be accomplished with a self powered/DSP crossovers -used Meridians can certainly give you a taste. Manual reading and a Analog to Digital Converter (ADC) likely required.
    Sorta surprised no body has mentioned the simply extraordinary Linkwietz LX-mini yet ?

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