What sub would be better with PR 15’s?


  • Member
    Travis Gibby on #1568

    Thank you TeeCee

    A perfect square wave at 100 Hz with p-p swing of 10 volts will have a RMS voltage of 5 volts (6.25 W into a 4 ohm load). A sine wave would only need a 14 volt p-p swing to produce the same RMS voltage. If you clip this sine wave off at 10 volts it will have less power, not more. In other words the unclipped signal from a more powerful amplifier will produce more power than the same signal clipped from a less powerfull amp (at the same gain setting of course).

    Yes you will deliver more power when you drive the amp into clipping, you will more readily deliver even MORE power from a more powerful amp.

    Everything else you said I agree with. However, I do not believe that high frequency components in the signal will cause your subwoofer to fail.

    Travis


    Member
    TeeCee on #1569

    Travis (which is also my name),
    I do think you see what I’m saying on the power. What you have to remember is that with a higher power amp, you will usually hear the sub bottom out when you deliver too much power. With the lower power amp, you will not be bottoming out the sub but you will still be delivering more power than the sub was designed for.

    As for the high frequency components damaging the sub, that’s not my argument to make, I just wanted to show the presence of high frequencies. Although I firmly believe that a sub trying to play high frequencies is likely to end up damaged – perhaps a voice coil coming loose. I’ve had this happen to a sub or too but they were not overly expensive subs.

    I’ve had subs die from deteriorated surrounds, torn spiders (which I try to fix with a little silicone), and voice coils that come loose. It’s never fun.


    Member
    Paul K. on #1570

    Thanks again for the replies. Although we got off on anther tangent and strayed from topic, a lot of good information was introduced. I’ve decided to keep my current setup and build another box with the same drivers. I’m throughly satisfied with the sound output, but I change my mind often and may go with something differnet down the road. Feel free to continue your discussion in this thread I don’t mind.

    Paul


    Member
    Travis Gibby on #1571

    Your welcome Paul. I hope you don’t feel like I hijacked your thread. I do think this topic is important however as many people exceed the manufactures thermal power rating believing that their subs will be safer with more power. They will usually be ok, depending on how conservative the manufacturer was in thier power rating among other factors (how high t he gain is set, how long the sub is used, and at how high a level). But some manufactures have been known to be fairly generous in their power ratings.

    The other thing important to point out is that just because your speaker is rated at 1 kW thermally, doesn’t mean that you will be able to take advantage of 1 kW of power in a given box. Most of the driver failures I have seen were not thermal failures, but mechanical failures from excessive excursions. Buying more power then you need wastes money.

    Travis, (nice name BTW)

    I understand what you are saying and you are right, a 10 V p-p square wave (5 V RMS) is more powerful than a 10 V p-p sine wave (3.5 V RMS). However, I want to make sure that people understand that clipping a waveform does not make add more power, infact it takes power away.

    The RMS calculations for square waves apply as readily as they do for any other periodic wave form. They are:
    (E1^2 + E2^2 + …/ Number of sampled voltages)^ 0.5

    Where E1, E2… are the sampled voltages.

    Travis


    Member
    TeeCee on #1572

    @Travis Gibby wrote:

    Travis, (nice name BTW)

    I understand what you are saying and you are right, a 10 V p-p square wave (5 V RMS) is more powerful than a 10 V p-p sine wave (3.5 V RMS). However, I want to make sure that people understand that clipping a waveform does not make add more power, infact it takes power away.

    The RMS calculations for square waves apply as readily as they do for any other periodic wave form. They are:
    (E1^2 + E2^2 + …/ Number of sampled voltages)^ 0.5

    Where E1, E2… are the sampled voltages.

    Travis

    That is true when you look at clipping due to a reduction in the voltage rails.

    *but* for a given amp where the voltage rails are fixed by design, when you push the signal to clipping, you are sending more power to the speaker. Therefor an amp capable of producing a maximum 100 watt pure sine wave could in fact deliver more power as a clipped or complex wave form. That is until something in the amp failed.

    I betting you understand that but perhaps didn’t realize what my point was.

    By the way, that method of calculating RMS would require continuous sampling or the equation of the signal. The equation of a sine wave is linear and easily defined. The equation of a clipped sine wave is neither.


    Member
    Travis Gibby on #1573

    You are right Travis on both accounts. An amp can produce a clipped signal at a higher amplitude than it can it can produce it cleanly. And I did not realize that was the point that you were making.

    You are also right when you say that RMS amplitude for a sine wave is easy to calculate:

    Peak amplitude * 0.707 = RMS amplitude

    Cheers,

    Travis


    Member
    dB on #1574

    @Travis Gibby wrote:

    @db wrote:

    You’re better off to have too much power available then too little. Amplifier clipping kills more drivers than over powering them.

    I’m not trying to look like a smart a** here.

    1) over powering a sub

    2) pushing a sub past it’s mechanical limits

    He said if your 25 W amplifier blows your 100 W subwoofer, then you should look at the build quality of your amp.

    Would you agree with this dB?

    Travis

    Yes. Still – More clipped 100 watt amps destryoy 100 watt drivers than 1,000 watt amps destroy 500 watt drivers.

    Add a third.

    3) Manufacturing deffects, whether in materials or craftmanship (usually evident early on – unless it’s say poor curing of adhesive bonds)


    Member
    TeeCee on #1575

    @db wrote:

    Yes. Still – More clipped 100 watt amps destryoy 100 watt drivers than 1,000 watt amps destroy 500 watt drivers.

    See that’s what I was trying to explain.


    Member
    Travis Gibby on #1576

    Thanks dB,

    I’m glad because I’ve been telling people that less power is safer :).

    Take it easy,

    Travis

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