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Can you please help me understand what a speaker does with the signal it receives?

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  • Can you please help me understand what a speaker does with the signal it receives?

    Hey folks!

    I recently built a subwoofer based on some chats on here. It came out great. I dug through the internet and discovered I may have had my receiver setup wrong, and once "corrected" the sound quality was night a day and it put a smile on my face (while also aggravating me that I did it wrong for so long).

    My mains are completely rebuilt Klipsch KG 5.5's. They use dual 10" drivers a tractrix horn tweeter. They produce impressive bass and are very efficient.

    I changed my crossover for the mains (2.1 setup right now) to 80 hz, it had been 40 hz and I changed the LPF for LFE to 120 HZ. I also have it set to what Denon calls "LFE + Mains"

    I was under the impression that, I can send a "full signal" to my main speakers. They have a crossover network (obviously) that sends the correct frequencies to the 10" drivers and the tweeter (x-over @ 1600 hz) and then the cabinet volume and port length tune the cabinet to something probably around 35 hz +/- 3 hz (best guess without doing the math right now). So even if it sees a signal that reaches to 40 hz or lower, it doesn't matter because the drivers will play what there design/specs and cabinet/port allow it to......right??

    I have gone through a couple of those drivers lately, they don't make them anymore and I have to find em on ebay. I was getting ready to replace yet another buzzing driver (VC's buzzing against each other?), but after making these adjustments to the crossover freq in the receiver and the LFE the buzz went away and everything sounds terrific. Was I damaging those drivers sending the speakers too low of a signal? Maybe their power handling was less than what I was pushing at those frequencies? I had been using different sine wave tests at 40 hz and 100 hz playing with the phase on the newly built subwoofer. This is when I discovered another buzzing driver.

    Questions are:
    1. Is the buzzing usually VC's?
    2. Could I have been the one damaging the speakers and not father time?
    3. What exactly is happening when I change the crossover in the receiver to 80 hz for example, rather than 40 hz?
    4. Am I right or wrong in thinking that I can send all the signal/all the frequencies at my main speakers and they'll play what they can play?

  • #2
    Originally posted by KodiakHT View Post
    even if it sees a signal that reaches to 40 hz or lower, it doesn't matter because the drivers will play what there design/specs and cabinet/port allow it to......right??
    Wrong. They will play, or attempt to play, everything sent to them, including material too low in frequency for them to handle. This leads to over-excursion, distortion and voice coil overheating. To protect them from damage the signal to them should be high passed. That's what the AVR crossover does. Raising the crossover frequency from 40 to 80Hz shifts the low end away from the mains into the subs, which should be better able to deal with them. OTOH setting the low pass for the subwoofer signal at 120Hz allows directionally locatable frequencies into the sub, which you don't want. It should also be set at 80Hz.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      Originally posted by billfitzmaurice View Post
      Wrong. They will play, or attempt to play, everything sent to them, including material too low in frequency for them to handle. This leads to over-excursion, distortion and voice coil overheating. To protect them from damage the signal to them should be high passed. That's what the AVR crossover does. Raising the crossover frequency from 40 to 80Hz shifts the low end away from the mains into the subs, which should be better able to deal with them. OTOH setting the low pass for the subwoofer signal at 120Hz allows directionally locatable frequencies into the sub, which you don't want. It should also be set at 80Hz.
      Ok thanks for the reply. My mains play down to 34 hz (not sure what their actual F3 is, bandwidth is advertised as 34-20k). So they shouldn't really have an issue with the crossover set to 40 hz right?

      Thanks for the tip on the sub playing up to 120 hz, I'm aware of the wavelength becoming directional at that frequency. I read arguments back and forth about 80 or 120. Wonder if the sub is facing me like the mains, if 120 is then ideal or not

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      • #4
        Originally posted by KodiakHT View Post
        Ok thanks for the reply. My mains play down to 34 hz (not sure what their actual F3 is, bandwidth is advertised as 34-20k). So they shouldn't really have an issue with the crossover set to 40 hz right?

        Thanks for the tip on the sub playing up to 120 hz, I'm aware of the wavelength becoming directional at that frequency. I read arguments back and forth about 80 or 120. Wonder if the sub is facing me like the mains, if 120 is then ideal or not
        The 34hz rating means the manufacturer believes those speakers won't lose too much efficiency/volume at those low frequencies...the speaker should be only about -3db to -10db quieter down around 34hz (and up around 20Khz).
        BUT that does NOT mean the speakers can handle their full wattage rating all the way down that low.
        The lower/deeper the bass, the farther in and outward a speaker will need to move to keep that bass sounding as loud as higher frequencies...so deeper and deeper bass forces a speaker to move farther and farther in/out. A speaker that moves too far can crash the voicecoil against the back of the magnet gap, denting the voicecoil so that it'll rub and make noise.

        In other words; those speakers might be rated for 150watts (their voicecoils should handle ~150watts of heat from music), but full-range music with deep bass down below 60-80hz might have them run out of XLIM (safe forward/backward movement amount) around 40watts instead.
        So you can either play them full-range while staying a bit quieter, or you can crank them up to full rated wattage if you have the deeper lows being sent somewhere else instead (or simply blocked/limited from hitting the speakers).

        A 40hz crossover can be too low for most bookshelf or hometheater speakers to play really loudly....especially if it's an efficient speaker, because more efficient speakers tend to have smaller/shorter voice-coils and might have smaller gaps (this helps the moving parts be lighter-weight and more efficient..making them louder watt-per-watt but less able to handle loud+deep bass).



        The directional thing with subwoofer's being low-passed too high isn't about their facing-direction, it's about location in the room....AKA frequencies below 60-80hz will usually sound like they're coming from all around you in the room so you can't tell where the speaker making those low sounds is located by listening, BUT frequencies above 60-80hz will get easier and easier to located by listening so you might notice if the subwoofer is set toward one side or behind you when it plays those higher bass-notes instead of having them only come from the front L/R speakers (which should be fine for 80hz and above all by theirselves).
        My first 2way build

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        • #5
          Suggest you ask on the Klipsch forum what is a suitable sub xo point. Remember, the xo point is not a brick wall, the low frequencies fade as they go lower so some frequencies lower than 40 get through. Same going up in freq.

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          • #6
            Originally posted by KodiakHT View Post
            Ok thanks for the reply. My mains play down to 34 hz (not sure what their actual F3 is, bandwidth is advertised as 34-20k). So they shouldn't really have an issue with the crossover set to 40 hz right?
            Klipsch plays fast and loose with their specs. That 34Hz is probably where response is 10dB down. That means for the speaker to be as loud at 34Hz as it is at, say, 100Hz it will need ten times the power. That's what leads to blown drivers. If your system is well balanced your subs should be able to handle at least four times the power from 40Hz to 80Hz as your mains can. There's nothing to be gained crossing over the mains lower than 80Hz, other than added stress on the drivers and the amp powering the mains, which leads to distortion.

            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Originally posted by billfitzmaurice View Post
              Klipsch plays fast and loose with their specs. That 34Hz is probably where response is 10dB down. That means for the speaker to be as loud at 34Hz as it is at, say, 100Hz it will need ten times the power. That's what leads to blown drivers. If your system is well balanced your subs should be able to handle at least four times the power from 40Hz to 80Hz as your mains can. There's nothing to be gained crossing over the mains lower than 80Hz, other than added stress on the drivers and the amp powering the mains, which leads to distortion.
              yup, thanks. This is what I'm seeing and hearing. Music sounds significantly better after changing the cross over from 40 to 80. I just couldn't understand exactly why at first. I have a better understanding now.

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