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xtp

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  1. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted

    My 1st enclosure sounded very well (only under 200Hz), but as I explained, it was too big (you said that too and I agree).
    So how big should it be?
    Should I use the 1st design (rectangular top and bottom) at a smaller scale (how small?) or the 2nd design (square top and bottom) at a larger scale (how large?)?
    What should the volume of the enclosore be (approximately)?

    You certainly don't need a 6th order crossover.

    But it sounds great!
    Will it work if I use three Linkwitz-Riley bandpass (highpass+lowpass) filters in series (highpass+lowpass+highpass+lowpass+highpass+lowpass)?

  3. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted


    Sorry, you said something like that: "When I tested them in properly designed enclosures with a 2x35W/4ohms or 20W/8ohms power amp they almost reached their mechanical limit below the amp's maximum power".

    I didn't want to turn the volume up more.

    Then its volume is too big for an 8" subwoofer.

    No...
    I found the size of the enclosure in a book (1980s).

    It isn't much power but maybe your room is small.

    Yup. 3m/4m/2.4m.

    A Butterworth filter has positive feedback and a flat response. The multiple 6dB RC filters you talked about aren't Butterworth and won't work.
    A Butterworth crossover with an even number of RC stages creates an acoustic notch at the crossover frequency when the speakers are wired in-phase. If the speakers are wired out-of-phase they add and create a boost at the crossover frequency. An odd number of RC stages creates a flat response at the crossover frequency. Linkwitz-Riley filters create a flat acoustic response at the crossover frequency regardless of the number of RC stages. ;D

    Ok...

  4. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted

    Hello Audioguru,


    Your 8" sub-woofer that reaches its mechanical limit with only 20W is either really cheap or is in an enclosure that doesn't damp its motion properly.

    I didn't say that my 8" subwoofers reached their mechanical limit and 20W was probably the average power delivered to the speakers and they ain't cheap either. I ment that I wouldn't turn the volume up more, everything in the room was shaking, I probably scared my neighbours too :D. The enclosure could support 12" subwoofer at full power ;D.

    For the subwoofer and the midrange I think I'm going to use something like the 10W amp in the link below but without the bass boost (for each speaker - that means four amps).
    http://www.redcircuits.com/Page61.htm


    I hope you understand that crossover filters in the links I provided are designed for a flat passband (unlike yours) and no cancelling phase-shift at each crossover frequency. ;D

  5. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted


    Hi Xtp,
    10W per channel, per speaker driver isn't enough for a good music playing system. You will be tempted to "turn up the volume" causing the amplifiers to clip, which will destroy the tweeters (and your hearing). Use much more power and don't worry about "blowing-out" the speakers unless they are really cheap. The sounds in music don't play continuously for any amount of time to overpower speakers.

    I don't think we're talking about the same kind of watts :-\.
    If you look at same types of speakers you'll se that the power stamped on each speaker is different from one manufacturer to another.
    For example 10" car subwoofers can be found with a power rating of 180W to 1000W :o, even if the 1000W subwoofer is less powerful than the 180W subwoofer, but their real power is probably around 40W :P.
    A lot of car audio systems (that include a radio and a CD player) have their power amp built with TDA 1554 IC that has a maximum output power of 4x11W single ended or 2x22W bridged, but all manufacturers write 4x45W or 4x60W on them.
    My 8" 8ohm subwoofers are stamped "80W RMS continous power" and "120W RMS peak power". When I tested them in properly designed enclosures with a 2x35W/4ohms or 20W/8ohms power amp they almost reached their mechanical limit below the amp's maximum power :(.

    When I worked for a sound system equipment manufacturer, one dealer brought back some of our cheapest speakers for replacement under warranty. He installed them in a bowling alley and they were literally burnt and even smelled burnt. The problem was caused by the low amplifier power he used. At heavy amplifier clipping the speakers received a continuous DC voltage that alternated as AC. We refused warranty replacement for the speakers so he bought more and a much higher-power amplifier for them. Then the system worked fine.
    I burnt a little speaker that was rated at 40W. I had it operating for years from my 70W amplifier. When I removed the burnt 4" "woofer" I noticed that it was stamped 5W. The replacement was also stamped "5W" and also worked well for years.

    My amps will have overcurrent protection ;D, so they won't allow any dangerous DC to the speakers.

    Here is a good audio site with some reading for you:
    http://www.sound.westhost.com/index2.html
    http://www.sound.westhost.com/biamp-vs-passive.htm
    http://www.sound.westhost.com/bi-amp.htm
    http://www.sound.westhost.com/bi-amp2.htm
    http://www.sound.westhost.com/clipping.htm
    http://www.sound.westhost.com/tweeters.htm
    http://www.sound.westhost.com/sp-boxes.htm
    http://www.sound.westhost.com/sp-boxes2.htm
    http://www.sound.westhost.com/project09.htm

    It seems funny but I know the Linkwitz-Riley filters from an old magazine ;D (20 years old...), it wasn't written anywhere that those filters were Linkwitz-Riley filters.
    Thanks anyway.

  6. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted


    Designing the crossover filtering is your biggest problem.


    Not yet.
    My 3 way speaker system project is two years old now and since then it's been permanently changing, so I'm not sure what kind of filters I'm going to use for the crossover. This project is still on the "drawing board".

    My biggest problem is how much power should each speaker get.
    I'd choose 10W (RMS) for the subwoofer, 10W (RMS) for the midrange and 5W (RMS) for the tweeter and that's because I want my system to be able to withstand music played with instruments, not made by electronic means.
    The 10W subwoofer amp will have a peak power of 20W, so it'll be perfect for my 8 inch kevlar cone subwoofers (it says that their maximum power is 120W but I don't believe it :P).

    ... ::) Can you show me some schematics of those Butterworth or Linkwitz-Riley bandpass filters?


  8. 3 way speaker system

    in Electronic Projects Design/Ideas

    Posted

    The filters are (theoretically ::) - I haven't built them yet) six 6dB/octave high pass and six 6dB/octave low pass in series, each using a resistor and a capacitor.

    One high pass filter and one low pass filter in series form a band pass filter.
    Six 6dB/octave band pass filters in series should form a 36dB/octave band pass filter :-\.

    I simulated 6, 12, 18, 24 and 36dB/octave band pass filters using a computer program and the last one was the best, it sounded better than the others ;D.

    If I wanted to make the building of this sound system easier I would have chosen a single amp per channel and separate the frequencies with passive filters (inductors and capacitors) but I don't think it would sound better than "one amp per speaker".

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