Forums Music Sound Engineering Crossover Help!!!

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  • #1054452
    chutneyjoe
    Participant

      Hi everyone,

      so after some hassling i’ve got a shitty crossover off a mate that has two channels, so i’m using each of the channels into 1 amp each channel and then to a set of tops and one set of subs. Could i link an extra set of tops to the ones already connected and same with the subs? So i would be running 4 tops off 1 amp and 4 subs off the other. Also to add, two of myy subs have built in crossovers, will i still be able to link the subs through these ones? or should i put the pair without built in crossovers first from the amps? When i’m only splitting it into 2 channels does this mean that the mids are left out? or are they in the channel with the tops as well?

      And how do people run huge amounts of speakers, for example, what kind of crossover is there that has something like 4 channels, where i can run 2 amps for bass, 1 amp for mids, and 1 amp for highs, anyone know of a relatively cheap one?

      Any help is greatly appreciated!! 🙂

      #1262775
      Pat McDonald
      Participant

        It depends on a lot of factors as to whether you can add extra speakers to an existing arrangement. The most important one is the limit of what each crossover can handle.

        Assuming you are planning on adding the extra speakers to each seperate loop as a series connection (so it goes through one set, then the others, then back to the cross over) what you are doing is adding extra resistence (impedence) to the load, which means that you would get the same overall volume from each set but be able to spread each speaker out to give better coverage of an area).

        Quote:
        And how do people run huge amounts of speakers, for example, what kind of crossover is there that has something like 4 channels, where i can run 2 amps for bass, 1 amp for mids, and 1 amp for highs, anyone know of a relatively cheap one?

        Very often they build parts of it themselves. Helps keep costs down.

        In terms of your “miracle” crossover, I think you are referring to something like an active crossover network, where the components are powered (and to some extend controllable and limitable), rather than passive crossovers, which just sift the different frequences from a signal into the “bass” or “not bass” catergory. Likewise, if you want it seperated into 3 channel (bass, mid range and top) then you have a more complicated crossover again.

        Do remember that the weakest link in the chain between amplifier (overload it and it blows) crossover (overload and it blows) and speaker(s) (overload them and they blow) will be the first bit that blows up if you turn up the power too much. There will always be something that is lower spec than the other components, and some amplifiers have overload sensing that will cut power if it’s beyond the limits of the speaker array. Saves anything blowing up.

        Ideally, if you have a lot of speakers, and fused outputs on the amp, then the worst that will happen is the fuse in the amplifier blows. It’s a lot cheaper and easier than replacing all the speakers and crossovers. And you are quite right that bass frequencies take more power to amplify than more treble frequencies. Bass speakers usually have wider area, are larger, than speakers which don’t emit bass frequencies.

        If you’re asking me to recommend particular kit – I’m not familiar enough with current technology to give you really informed buying information. But, if you can calculate amps, and resistance (ohmage impedence) then you can work out power (watts, W) and that gives you something to base your designs on.

        It’s a hugely complex area. But at least I’ve given you some ideas of how people put the bits together, and how you can look up the rules guiding how big each piece has to be not to blow up.

        #1262773
        cheeseweasel
        Participant

          Providing that the crossover is an active one (i.e. a cased piece of equipment that you plug into the mains with XLR/jack inputs and outputs) you can run as many amplifiers as you want from it – hundreds if you like. All it does is split the signal into different frequency bands – what you do with the signal after that is up to you.

          To know how many speakers you can run off each amp you will need to look at the figures. What is the input impedance of each speaker (it’s usually printed on the back of the speaker)? What is the minimum load that the amp will happily drive (again, this is usually on a sticker on the back of the amp)? If your speakers are 8 ohms and the amp will go down to 4 ohms then you will be able to drive two speakers from each amp channel (since connecting two 8 ohm loads in parallel gives a combined impedance of 4 ohms). Linking any more than two speakers to a single channel in this setup would risk damaging the amp. Also bear in mind the rated output power of the amp – there is no point connecting two speakers per channel if the amp is not powerful enough to drive them properly.

          In bigger systems, professional amps often have a ‘link through’ connector that allows you to daisy-chain several units together.

          #1262776
          Pat McDonald
          Participant

            @cheeseweasel 508488 wrote:

            there is no point connecting two speakers per channel if the amp is not powerful enough to drive them properly.

            Key word here is “properly”. Amplifiers usually operate best at 80-90% of maximum volume, when pushed to max, the sound distorts as the amp is overdriven.

            Likewise, put too much juice through one speaker rather than 2, it distorts the sound. Yes what a speaker’s maximum capacity (in ohms and watts) is usually printed on the speaker. Keep running the speaker in that range and it will blow up sooner than having 2 underdriven speakers (for the same volume).

            My point is, sometimes putting 2 speakers on to one channel helps you avoid that speaker distortion and prolongs the life of the loudspeakers (they are moving parts – they have a finite lifespan). Ideally, the amplifier isn’t overdriven, nor is the crossover sorting out the frequences into different channels, and nor are the speakers run too close to their maximum tolerances.

            #1262774
            chutneyjoe
            Participant

              Thank you guys this is all really helpful. I’m learning one step at a time!!! Cheers for the info i shall put it into practice 🙂

              #1262777
              Pat McDonald
              Participant

                Important step to get your head around – wattage.

                Watts are the equivalent of joules (volts X amps) per SECOND. So there’s a time factor to consider.

                Bearing in mind that music – audio – is lots of little compression waves pulling backwards and forwards, you might appreciate more why watts are just average figures over one second – a tiny little bit of treble on a drum snare doesn’t last long or have much of a waveform, but it tends to perceived as loud due to the nature of the waveform.

                Likewise, a simple bass beat might sound pretty quiet but actually measures as a dirty great wave front.

                Seeing music playing as waves – with a computer or oscilloscope – can teach you these sort of factors, and once you have got your head around them, the actual mathematics to work out power capabilities, and understanding frequency response (why little speakers don’t do bass so well, for instance) become a lot more second nature.

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              Forums Music Sound Engineering Crossover Help!!!