Design bass amplifier

Discussion in 'Audio' started by josejos, Mar 6, 2018.

  1. josejos

    josejos

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    Hello,

    I am trying to design my own stereo at home with a amplifier with a separated bass speaker en tweeters.
    I have once designed a simple amplifier with the TDA2003 IC but for this application i want something more powerful.

    I have found the TDA2030 IC but for the circuit i need some filtering to get the low tones (and separate this from the tweeters).
    From wich order is this filter and what is the cuttof frequency of this filter?

    Have someone tips or help to design this?

    Dear
    josejos
     
    josejos, Mar 6, 2018
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    Arigato likes this.
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  2. josejos

    Audioguru

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    If you use one amplifier to drive a woofer and a tweeter then you need a "passive crossover network circuit", look in Google for a website that has them.

    A first order filter has gradual slopes and the low frequencies might blow up the tweeter and let the woofer shriek high frequencies. A second order filter is better but it causes a notch at the crossover frequency or a peak depending on the phases of the speakers. A third order is best. The crossover frequency depends on the spec's of the woofer and tweeter or as recommended by their manufacturer.
     
    Audioguru, Mar 6, 2018
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  3. josejos

    WHONOES

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    I suspect Josejos is wanting to build an active speaker.
    As for a passive speaker crossover, it is possible to construct one that sum's to zero at the crossover frequency using the Linkwitz - Riley type. The only issue is that there is a 180degree phase difference between the 2 halves. This however is easily remedied by connecting the tweeter reverse phase. Having said all that. passive speaker crossovers are notoriously difficult for the amateur to design. It is easy enough to design a mathematically correct filter but, that assumes that the speaker used has a perfect profile. So the mathematical version is only the starting point. Having said that, the Butterworth type is more commonly used as it has a maximally flat passband.
    As far as Joseos is concerned (and maybe others) the active avenue is to a degree simpler to design as the speaker vagaries may be largely ignored, assuming of course, that the cabinet has been correctly designed and constructed and that the speaker unit selection is not outrageous.
    Information required would be:
    Chosen speaker chassis.
    Crossover frequency
    Type of loading.
     
    WHONOES, Mar 7, 2018
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  4. josejos

    Audioguru

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    I bought some inductors from a local high-end speaker manufacturer. My finished speakers did not sound good so I measured their very poor response and discovered the wrong inductance marked on the inductor. I went back to the speaker manufacturer and complained that their marked inductance was wrong so I listened to their demo speaker and measured its very poor response. I showed that their inductors are marked wrong.The high end speaker manufacturer only cared about how their speakers look like, not about how they sound and did not even test each one they made.

    I think the separate "bass amplifier" Jose is making has a higher output power than his existing amplifier because his woofer is too small to produce powerful low frequencies. He should post a video of it burning out.
     
    Audioguru, Mar 7, 2018
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  5. josejos

    BobK

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    Your post is not clear. Are you using 1 amplifier or 2 for low and high frqeuencies?

    Bob
     
    BobK, Mar 7, 2018
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  6. josejos

    Hopup

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    What was the speaker manufacturer Audioguru?
     
    Hopup, Mar 7, 2018
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  7. josejos

    WHONOES

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    I tend to make my own inductors then I know they will be accurate. How on earth did you measure a manufacturers demo speaker? presumably it would have been in a shop or on their premises.
     
    WHONOES, Mar 7, 2018
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  8. josejos

    Audioguru

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    I can't remember their name but I looked on a map and they are gone.
     
    Audioguru, Mar 7, 2018
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  9. josejos

    josejos

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    Ok, thanks for the explination, you helped me a lot. I would to build a seperate amplifier for the woofer.
    The stereo would be in my room and i don't need very large power but what is the common power for the woofer and tweeters?
    Do the design off the bass amplifier need some modifactions to drive the woofer signal(I was planning to use the TDA2030 as amplifier for the woofer and the TDA2003 as the tweeter)?
     
    josejos, Mar 9, 2018
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  10. josejos

    josejos

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    Haha i will try to film this but now my speakers are more has a higer power rating than my amplifier. Thanks for the application.
     
    josejos, Mar 9, 2018
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  11. josejos

    josejos

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    I would like to use 3 amplifiers, two for the tweeters and one for the woofer.
    Or do you think 2 amplifiers is good enough.
     
    josejos, Mar 9, 2018
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  12. josejos

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    Speakers always have a higher power rating than the amplifier so the speakers do not blow up when the music plays loudly.

    Your tweeters need a highpass filter because low frequencies will damage them.
    Your woofer needs a stereo to mono converter (2 resistors) and a lowpass filter because a woofer shrieks when it plays high frequencies.
    Instead of using inductors to feed the amplifier to the speakers it is simpler and less expensive to make active highpass and lowpass crossover network with opamps that feed the 3 amplifiers. The tweeter and woofer manufacturer will recommend what the crossover frequency should be.
     
    Audioguru, Mar 9, 2018
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  13. josejos

    WHONOES

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    For all the years that I have been doing this, it has been the other way round. The amp should always be more powerful than the speakers. There is a few reasons for this. If you are running 50W speakers with a 30W amp and you try to run the amp flat out it is going to sound awful also there is a good chance that the tweeter will be destroyed when the amp starts clipping and produces lots of broad band harmonics. As well as these two, a 100W amp running 50W speakers will be cruising and giving much better sound, you will soon know when you have reached the speakers limits as it will start distorting but, without the destructive harmonics of the underpowered amp.
     
    WHONOES, Mar 9, 2018
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  14. josejos

    WHONOES

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    Forgot to mention in earlier post that the conventional way to do what Josejos is after is to use 1 amplifier per speaker is 4 speakers and 4 amps and then use active filters to split the audio spectrum as required.
     
    WHONOES, Mar 9, 2018
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  15. josejos

    josejos

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    Ok thanks, i have protyped this today and everthing seems to work fine.
    I only have a problem with single supply operation when the bass seems to influence the offset given to the signal to lay in the middle of the supply range.
    I think the best thing to do is to make a dual supply for the circuit?
     
    josejos, Mar 9, 2018
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  16. josejos

    josejos

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    Ok thanks for the tip, i think this will be dificult, i found some bass speaker but the max power off the speaker is 250W.
     
    josejos, Mar 9, 2018
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  17. josejos

    WHONOES

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    Is the speaker rating RMS or Peak power? It makes a lot of difference.
     
    WHONOES, Mar 9, 2018
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  18. josejos

    WHONOES

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    How have you configured the thing? Are you using one amp per speaker. What sort of filters are you using? What crossover frequency? Are you still using the TDA2030?
     
    WHONOES, Mar 9, 2018
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  19. josejos

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    Only people who play acid rock have the amplifiers clipping like crazy, but it happens often so the speakers should be sturdy enough to handle lots of power. He has "a room" (a bedroom?) and he decided that a TDA2003 amplifier for each tweeter and a TDA2030 for the woofer will be loud enough. The power supply voltage for the amplifiers and the speaker impedance determines the power output (loudness) at clipping.
    A 2.1 sound system is common and has two satellite mid/high speakers and one woofer.

    Output offset voltage? The waveform of the signal sets the amount of offset voltage which should be small enough to not produce any trouble. Using a dual polarity power supply will still cause offset voltage at the output if the waveform at the input produces it.
    I think maybe your power supply is not powerful enough and the bass causes its voltage to drop, but the output of the amplifier stays at the same mid voltage as before which causes the top parts of the waveform to have clipping.
    If a dual polarity power supply is used and drops both voltages when the bass is playing then if the output of the amplifier is too high the clipping will be symmetrical, but the output of an amplifier should not be high enough to produce clipping.
     
    Audioguru, Mar 10, 2018
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  20. josejos

    WHONOES

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    AG. The output offset voltage of an amplifier is nothing to do with the waveform of the signal and is a function, primarily, of the small difference in the Vbe of the input transistors times the gain of the amplifier Calling it the output offset is a bit of a misnomer as it is actually an input offset. It is possible to virtually eliminate the offset voltage at the output but I won't go into that here. I would expect an output offset voltage to be less than ±100mV any more could point to a poor design. It doesn't matter if clipping is a bit one sided for, clipping is clipping and is to be avoided.
    You are correct in recommending a ±V power supply.
    As I have said elsewhere on this forum, there is a relatively simple way to calculate the RMS voltage and hence peak to peak voltage which will ultimately determine the power supply requirement for a given output into a given load and is:
    Sqrt of RMS power x Load impedance.
    Example:
    50W at 8Ω = 400
    SQRT of 400 = 20. Therefore RMS voltage required for %W into 8Ω is 20V RMS
    Peak to peak voltage is then 2.84 x 20 = 56.8.
    Allowing for saturation in the output transistors and other circuit losses, a ± 30V power supply would be required.

    Edit. I also meant to ask what speaker chassis Josejos is using.
     
    WHONOES, Mar 10, 2018
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