Sorry. Another Ohm problem.

Discussion in 'Hi-Fi and General Audio' started by Baz, Sep 26, 2017.

  1. Baz

    Baz

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    Hi. all. I have an amp with Output Power of 2x60W rms (4 Ohms) or 2x50W rms (8 Ohms). Taking only one channel. I have a bass/ midrange 12'' speaker rated at 8 Ohms and a tweeter also rated at 8 Ohms. If I was to connect them in Parallel ( Making them both now 4 Ohm units. ) Would this damage the speakers in any way? This next bit is nothing to do with my problem. But any ideas on a mid-range or tweeter that covers the missing range Here -.
    The watts of the speakers are 200. With a range of (Hz) 30-4200. And tweeters 150 watts. 4.5kHz-20kHz ( Just in case I pop on a bigger amp.) I'm going to be using a crossover in each cabinet.
     
    Last edited: Sep 26, 2017
    Baz, Sep 26, 2017
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  2. Baz

    GZboat

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    If you use a proper crossover (that must itself have a nominal 8 ohm impedance if your two drivers are 8-ohm units), the impedance of your enclosure will remain at 8 ohms. In effect, the amplifier only "sees" the 8 ohm load of the crossover. With one enclosure per channel on your stereo amp, you will be operating safely at 2X50W RMS. If it's a two-way crossover, you won't be able to properly and safely add a midrange driver. You'll need an 8 ohm 3-way crossover if you wish to build a 3-way system.
    Greg
     
    GZboat, Oct 2, 2017
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  3. Baz

    Baz

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    Thanks for the reply. I do have a 2 way crossover on order for each channel. Cheers.
     
    Baz, Oct 3, 2017
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  4. Baz

    Baz

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    Sorry. Just another quick on this. If I have 2 tweeters. One is a long throw and the other an ordinary pizzo. Could I in connect them both to the high filter of the crossover and still have the bass unit on the low filter. Would the high filter read as 4 Ohms and the bass ( low ) as 8 Ohms. And would this muck the amp up. Sorry about all this. I have looked on u.tube and other site's for anything like this and cannot find an answer. Here is what I mean. What if.PNG
     
    Baz, Oct 26, 2017
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  5. Baz

    GZboat

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    A piezo tweeter should not have an impedance anywhere near 8 ohms. It should be more like 50 to 250 ohms, effectively presenting no additional load to the amplifier channel. The impedance of a piezo tweeter is inversely frequency-dependent; the impedance decreases as frequency increases. At frequencies far above the range of human hearing, the impedance can drop to where a damaging additional load is imposed. The standard protection for this is a small series-mounted resistor for each tweeter unit. Attached is a pretty good technical paper about the proper uses of piezo tweeters.
    https://www.grc.com/acoustics/CTS_Piezo_Tweeter_AppNote.pdf
    One other point, however. Combining tweeters of significantly different physical construction, especially if they are reproducing the same frequencies, will introduce unpredictable phase cancellations and combinations that will, in turn, introduce comb filtering into the high frequency reproduction. It will not make your highs sound better. Quite the opposite. Hope this helps.
    Greg
     
    GZboat, Nov 2, 2017
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    Baz likes this.
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