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Urggg, why do amp companies do this ???

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  • Urggg, why do amp companies do this ???

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ID:	1431053 So I was looking at a new 4 ch amp, which will be used for my mids / highs, and my mid-bass. The way that I will be using it, will make the X-over points critical. (well, kind of... I guess I could still use the crossover feature of the deck. I prefer to use both. But it just kills me when amplifiers have a dial that says 50hz on the bottom left, and 500 hz on the bottom right, and NO numbers anywhere else around the dial ! Come on man ! At least give me some reference points ! How TF are you supposed to set your crossover points from say 100 to 350, on a stupid freaking dial like this ???


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  • #2
    I'd assume (yes, yes, yes . . . ) that TDC is 160Hz (about 3X 50, & about 1/3X 500).

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    • #3
      But are the pots linear or logarithmic....?

      I'm sure that somebody more knowledgable about small electronics parts than I am can tell you an easier way to test them, but I suppose you could use a pocket oscilloscope like a DSO Nano V3 (which I use to set my amplifier gains anyways) to measure the waveform and voltage at the amplifier terminals using a test tone CD. Play a test tone at the frequency at which you want to filter set (play it a lower volume so as not to clip or blow up the oscilloscope) then turn the knob until you see it affect the waveform amplitude. Compare your original voltage to the new voltage to see where your 3db down point is (or where it just starts to affect the voltage depending on what topology you are aiming for) and thats where your knob should be set.

      I suppose you can do the same thing with a multimeter and just observe the voltage.

      Someone else is welcome to corroborate or correct my musings...

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      • #4
        Another tuning idea...

        Good old Audiotools and the iMM6 mic.... Use the analyzer to watch where the roll off actually happens and adjust to your target with only one section (mid, woof, tweet etc) playing at a time. Then fire them all up and tweak some more to flatten it out on the analyzer.
        Electronics engineer, woofer enthusiast, and musician.
        Wogg Music
        Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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        • #5
          Wogg, I'm sure that would work, but why not just put a few reference numbers around the dial ? That would work perfectly fine for my purposes....

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          • #6
            Originally posted by Fishchris View Post
            Wogg, I'm sure that would work, but why not just put a few reference numbers around the dial ? That would work perfectly fine for my purposes....
            Yeah... wasn't addressing the whole why not question. Perhaps the artwork would get too small, or they wouldn't be accurate so someone with an o-scope would complain. Who knows... now you just have to deal with it
            Electronics engineer, woofer enthusiast, and musician.
            Wogg Music
            Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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            • #7
              I have seen a few amps where they just had a dot, or a short radiating line out from the dial, then a few small numbers out from those marks. Heck, even just 3 or 4 additional reference points would be a huge help. And it would not cost them an extra nickel to produce 😵

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              • #8
                The old PPI (well at least the Power Class for sure) amps had indented pots and the manual told you how many clicks to your target frequency. That worked ok.

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                • #9
                  I have seen a few amps where they just had a dot, or a short radiating line out from the dial, then a few small numbers out from those marks. Heck, even just 3 or 4 additional reference points would be a huge help. And it would not cost them an extra nickel to produce 😵

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                  • #10
                    Originally posted by Fishchris View Post
                    I have seen a few amps where they just had a dot, or a short radiating line out from the dial, then a few small numbers out from those marks. Heck, even just 3 or 4 additional reference points would be a huge help. And it would not cost them an extra nickel to produce 😵
                    Then they have to use decent enough potentiometers that the screened in points actually roughly correspond to a frequency

                    I liked my JL XD amps for this - decent legends on the xover controls. I used a DSP but though it was good that JL included them.

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                    • #11
                      Wouldn't it make more sense to tune the xovers by ear ?

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                      • #12
                        Originally posted by hitsware2 View Post
                        Wouldn't it make more sense to tune the xovers by ear ?
                        IMPO, it would make the "most sense" to be able to set it to what should be correct. And then maybe fine tune it by ear, making adjustments slightly in both directions, to see if that setting could be improved upon.

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                        • #13
                          Seems those controls are just too Tiny, to accurately find a frequency, even if they had room to put markings, a slight turn of a control that small might go 20-30 hz or more one way or the other due to the size limiting the accuracy.

                          On a much larger control, maybe...

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                          • #14
                            This is for a car, right? How critical can it be? Tuning by ear can be pretty effective or if you really want to over-egg the pudding, measure. Many of the mobile sound manufacturers target buyers whose main concern is the color of the woofers and magnet weight.

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                            • #15
                              Originally posted by dwigle View Post
                              This is for a car, right? How critical can it be? Tuning by ear can be pretty effective or if you really want to over-egg the pudding, measure. Many of the mobile sound manufacturers target buyers whose main concern is the color of the woofers and magnet weight.
                              Why would it be less critical in a car? Resonances and reflections are much more prevalent in a car, and physical driver separation many times what is experienced in most typical home situations. Crossover settings are critical to achieve any sort of blending.

                              Many home audio consumers buy based on aesthetics as well. You don't see many commercially manufactured home speakers that are raw MDF. The talk of WAF often comes up here as well. I am failing to see how aesthetics are tied to the OPs desire to have decent sound, regardless of where it is.

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