Audio Crossover Back in Service


Audio Crossovers are an essential tool for any high end speaker system. Because most individual loudspeakers are unable to cover the entire spectrum of audible sound as well as multiple drivers are, it is necessary to split the input signal into low and high frequency parts. When a friend of [Anthony]‘s was about to send off a classic Klipsch AA Crossover to be repaired professionally, [Anthony] insisted it was possible to save some money and do it himself.

The oil can capacitors of the Crossover had gone bad, so a new set of metalized polypropylene capacitors were ordered to pick up the task. After carefully removing the old caps, [Anthony] assembled the new set on a breadboard, and mounted the board to the old Crossover base (along with some tasteful McDonalds straw spacers). The entire process is detailed on his blog, and we are sure his friend saved a good deal by this home repair method. Capacitor issues are a common problem in repairing electronics new and old alike, and always a great place to start looking when devices start acting funny.

Comments

  1. fartface says:

    “Audio Crossovers are an essential tool for any high end speaker system.”

    Nice to see the editor knows nothing about speakers… a Crossover is required in ALL speaker systems where there is more than 1 speaker with a wizzer cone. a low end 2 way speaker has a crossover in it it’s required in any speaker design.

    “high end” speaker crossovers are made from either oversized components to support huge amp loads or made from exotic sounding materials to make really stupid people (audiophiles) pay a lot of money for nothing.

    Crossover design is old and important part of speaker design if you want the speakers to last. Nothing like pumping 200hz or lower into the tweeter and midrange to make them go POP! some tweeters like ribbon tweeters will fry themselves if they get lower than 10,000hz to them.

    Masters in audio engineering is useful for something!

  2. buckshot says:

    @fartface
    why the hostility?

  3. osgeld says:

    Guess it depends on your definition of crossover, yes even cheap speakers have SOMETHING, but its usually nothing more than a filter cap, which in my mind is just a filter cap, not a full crossover

  4. patman2700 says:

    (I can’t believe I’m saying this, but…) I’m with fartface. Seriously, even crappy RCA/etc. mainstream speakers have at least a small electrolytic capacitor to filter out the low end for the el-cheapo plastic-diaphragm tweeter.

    Not to downplay [Anthony]‘s work, but this doesn’t seem like too much of a hack to me. I’m even researching crossover design so that I can make one for my custom bass speaker cabinet, but I’m not sure that I’d submit that to HAD.

    Now, if he changed the crossover parameters to allow for an electrostatic tweeter to be thrown into the mix, then THERE’S a hack!

  5. patman2700 says:

    osgeld,
    Even a one-capacitor setup acts as a 6dB/octave 1st order crossover. Though I understand the logic, I’m basing this one off of a technicality.

  6. matt says:

    Worth noting that pro audio systems usually have crossovers before the amplification (active), while home and car audio typically have them after (passive).

  7. Whoever says:

    Furthermore multi-speaker designs for domestic applications are a thing of the past, modern high end is a single speaker with a factory-made FIR filter that brings it’s freq and phase response right up to “perfect”.
    Except of course it’s hard to make it look as “smexy” as a bunch of randomly thrown together speakers, so audiofooles still believe in a lot of speakers (to go along with the looks of their “smexy” untreated rooms :-).

    Also, I hate to be the one to say this, but… Repair != hack. Now I wouldn’t mind if it was a noteworthy repair, but this isn’t even noteworthy, it’s extremely simple and honestly not very well made.
    Good one the McDonald’s spacers though! I’ll have to remember that one. If anything it was worth for that. :-)

  8. Fallen says:

    I’m with osgeld. A single cap is just a filter. You need a filter for each driver, a LPF for the woofer and HPF for the tweeter. Running the woofer full range and the tweeter from 5kHZ up from a cap isn’t really crossing it over, as the woofer is still playing content above the 5kHz ‘crossover’ of the tweeter.

  9. HARaaM says:

    Is there a schematic for that?

  10. Cricri says:

    Nice to see old hardware being brought back to life, but that’s a waste of breadboard: for something as simple as a filter, I’d simply trim wires shorts, solder them in place, and protect with heat shrink.

  11. Dino says:

    Those old oil filled caps are usually what cause old tube amps to stop functioning. Nice to see old tech revitalized. :)

  12. Urlax says:

    He should have really hacked up a bic pen instead of a straw. Those are way too flimsy to support any load.

    The PCB weighs probably next to nothing, but still..

  13. Durandal says:

    Okay… all the philosophical discussion aside, a question for you specialists out there: I know the design and function of some passive crossover networks, but would someone be kind enough to explain what those two diodes (if they are indeed diodes) are doing there? I have never seen these in classic LC filter configurations….

    Thx!

  14. Niru says:

    @buckshot:
    re: hostility. . .
    “Audiophiles”. Audio Engineers. ’nuff said.

    This completes the lecture portion of your “Introduction to Internet Discussions” 103 Class.

    Please leave your multiple-choice final exam face down in the inbox on my desk. I will post your grade to the class-wiki within the next 6-12 days.

    I look forward to seeing you in class next semester. Thanks for your hard work!

  15. echodelta says:

    @ Whoever and all. It’s sad that home audio is now only about 5 tweeters and one woofer. Better to hear all the mpiss. Pentaphonic treble and mono bass, where formerly an INFINITE number of channels formed a solid (stereo) image across full range reproducers. People that accept this should only use floppy discs and use dial telephones, and dial-up internet at 2kb. And watch TV on a tube.

  16. Whoever says:

    @echodelta:

    I agree it’s sad that home audio is now a bunch of tweeters, not even a subwoofer on the tiny “iPod docks” kids use these days.

    As for the rest of your message, call me hard-a$$ed but I didn’t understand a word.. Could you elaborate?

  17. patman2700 says:

    @Whoever
    Modern systems “cheat” using advanced electronics and active crossovers.
    Instead of having a dedicated tweeter, midrange driver and (possibly) a woofer for each individual speaker (i.e. 5 in a 5.1 setup, 7 in a 7.1 setup, etc.), modern systems simply use 5 (or 7) high-frequency tweeters to give the illusion of multi-channel sound. The x.1 subwoofer is not only used for super-low frequencies anymore, but also for the frequencies that used to have their own driver.
    The perfect example is the Bose Companion 3 speaker system. I’ve tried a friend’s set, and it’s just as echodelta said; the two satellite speakers are nothing but tweeters, whereas all of the midrange and low frequency sound comes from the woofer.

  18. qwerty says:

    regarding N+1 audio system, they have only one woofer because the human ear cannot sense the direction very low frequencies come from as easily as it does with higher frequencies.
    However, a good system should have N *low-midrange+tweeter* boxes and one subwoofer, not N tweeters and one woofer. The latter choice is a compromise imposed by cost or space issues, not audio fidelity.

  19. ReKlipz says:

    @fartface

    “high end” speaker crossovers are made from either oversized components to support huge amp loads or made from exotic sounding materials to make really stupid people (audiophiles) pay a lot of money for nothing.

    There is something to be said for the quality of components; apparently something you chose ignore.

  20. paul says:

    I like seeing old audio equipment being brought back to life ( currently i’m using an old Sanyo amp witch I bought nonfunctional and completely refurbished )but I think [Anthony] should have replaced the inductors with air core ones ( the iron core in the existing ones will saturate at high levels and distort the sound pretty bad ). As for ,,modern high end systems” only the cheap ones use the combination of speakers mentioned above , true high-end systems – like the Klipsch THX 2 Ultra have satellite speakers ( that are usually 2 way speakers by the way ) that go down to 50-60 hz

  21. strider_mt2k says:

    Overall it is okay, but I agree: massive waste of breadboard and you could negate the soda straw silliness to boot.

  22. Shox says:

    must have been a slow day to report on a blog of a guy repairing capz

  23. Peter says:

    I’ll bet the current handling capacity of the replacement capacitors is not the same as the oil-filled ones they replaced. However, as a previous poster said, it’s probably overdesigned.

    And the oil was probably PCB if they were as old as the rest of the components look.

  24. Brennan says:

    Just wondering, what do you audio buffs think of the Bose L1 PA system as far as design and sound? I’m curious because as an acoustic guitar player, it’s one of the best systems I’ve played through and it seems to have a rather non-traditional design, which is fairly typical of bose.

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