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  • Subwoofer question

    I recently bought a Dayton SA70 sub amplifier, along with a Dayton SD215-88 subwoofer. Before I start cutting the wood and assembling the cabinet, I wanted to test out the amp and sub driver in open air.

    I have the amplifier hooked up to a stereo receiver; high-level input of the amp connected to the speaker outputs of the stereo receiver, and the high-level output of the sub amp connected to the bookshelf speakers I built a year ago.

    The amp passes through the signal from the receiver to the bookshelf speakers perfectly; however it seems like the sub driver barely vibrates, even when the gain is brought up to 50%. Obviously, I can't hear any of the bass from the sub driver, but this is to be expected since this is done in open air (no enclosure). So for this test, I just wanted to feel the cone and make sure it is vibrating.

    The problem is, for some songs, it feels like the driver cone hardly moves at all. The amp is definitely sending a signal to the sub driver; I've tested the electrical output to the driver with a voltmeter, and the amp fuse is intact.

    My question is this: Do these symptoms sound like a blown sub driver? Or should I just build the cabinet in the hopes that an acoustically-sealed enclosure will resonate with the minute excursions of the driver?

    I'm completely new to building subwoofers, so I can't make a judgement call on how much this driver should be moving.

    Thanks for any replies.

    -CAPGuy

  • #2
    Re: Subwoofer question

    In my experience a sub will move MORE when enclosed. The compression of the air behind the driver acts like a spring and helps to push back against the speaker. Now maybe I've got my terms wrong somewhere there but I KNOW when I change from a ported to a sealed setup the driver moves more sealed than ported.

    Hope this helps.

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    • #3
      Re: Subwoofer question

      How do you have the voice coils wired to the output of the Dayton sub amp ??

      The Dayton SD215-88 is a DVC driver(dual voice coil) - 8ohms per coil

      If you only have one coil connected the Dayton SA70 70W Subwoofer Amplifier it is only capable of outputting (at max volume) about 45 watts into that load. If you wired the two coils in series then the driver impedance would be 16 ohms and the amp would only be capable of delivering about 22 watts to that driver. Either of these conditions could be the reason that you see and hear so little from the driver......

      Try connecting both coils in parallel (which will give you a load impedance of 4 ohms) and then connect these to the sub amp, that way you should be able to utilize all of the 70 watts that the sub amp can supply

      Finally you should get some source content DVD / CD that has some known amount of higher level LF content - ie frequencies of less than 100 Hz, after all the Dayton sub amp (depending on where you have the internal XO set) will only deliver these low frequencies to the driver

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      • #4
        Re: Subwoofer question

        Thanks for replying guys.

        @Cokewithlime

        Ah, dude, I didn't even see that! I guess I can chalk this up to being new to building subwoofers. Thanks for the reply.

        I noticed there were two connection prongs and I assumed they were used for hooking up multiple woofers in series. lol

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        • #5
          Re: Subwoofer question

          although it sounds like your voice coil wiring (or lack there of) is definitely one problem, another possibility to come to mind is: when you say "stereo receiver", is it truly a stereo receiver, or are you by chance referring to an avr as a stereo receiver? if the latter, the bass management could be enabled, and since you have the sub amp hooked up to the receivers speaker level outputs, it could be that the bass signal is never making it to the sub amp in the first place. on the other hand, if your stereo receiver really is a stereo receiver and has no bass management... then just ignore me .

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          • #6
            Re: Subwoofer question

            I've got that same speaker and the same amp. And I had the same experience as you when I hooked it up without a cabinet. Completely unimpressed. Go ahead & build the cabinet, wire it up correctly & rock out. This combination makes a nice little sub.

            Dennis

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            • #7
              Re: Subwoofer question

              Put your ear next to the edge of the speaker. You should hear some bass.

              Ron
              C-Note Iron Driver Build
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              My Projects Page

              The good thing about science is that it's true whether or not you believe in it. - Neil deGrasse Tyson
              http://www.youtube.com/watch?v=cjuGCJJUGsg

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              • #8
                Re: Subwoofer question

                Ok so I built the cabinet today. I still haven't fine-tuned the passive radiator yet, but there is definitely some bass coming from the driver now that I've hooked the dual voice coils in parallel. Although I still have to turn the gain up to 50% before hearing an appreciable amount of bass. This is fine, its just I've heard from other sources that even 20% gain should be sufficient. Oh well.

                In answer to your question, absolootbs, its actually a true stereo receiver.

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                • #9
                  Re: Subwoofer question

                  Although, I do have a conceptual question:

                  According to the amp manual, the amplifier takes the left and right high-level speaker outputs from the receiver and derives a bass signal from both and sums the two. So if one were to reverse the polarity on, say, the right speaker output of the receiver by switching the positive and negative terminals, would that sum the right and left bass signals to result in a near zero bass output? (because the right signal would be out of phase of the left signal by 180 degrees?)

                  I ask because I just hastily moved my whole setup to another room and it sounds like there is very little bass coming out of the cabinet now. Is proper terminal assigment important when connecting an amp to a receiver via high-level outs?
                  Last edited by CAPGuy; 08-14-2010, 12:42 AM. Reason: not enough info

                  Comment


                  • #10
                    Re: Subwoofer question

                    Originally posted by CAPGuy View Post
                    Although, I do have a conceptual question:

                    According to the amp manual, the amplifier takes the left and right high-level speaker outputs from the receiver and derives a bass signal from both and sums the two. So if one were to reverse the polarity on, say, the right speaker output of the receiver by switching the positive and negative terminals, would that sum the right and left bass signals to result in a near zero bass output? (because the right signal would be out of phase of the left signal by 180 degrees?)

                    I ask because I just hastily moved my whole setup to another room and it sounds like there is very little bass coming out of the cabinet now. Is proper terminal assigment important when connecting an amp to a receiver via high-level outs?
                    yes you can test polarity with a 9 volt battery. hook it up to a set of the speakers tabs and see that the way the speaker moves say out towards you. then do the other set and see the movement must be the same as the other coil .. in theory this should be easy to do. hook post end of 9v to pos tab on speaker neg end of 9v to neg tab on speaker. repeat and in both case the cone should have moved in the same direction. dual voice coil speakers may be wired at the factory wrong. thus causing a problem. or you wired wrong

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                    • #11
                      Re: Subwoofer question

                      I ask because I just hastily moved my whole setup to another room and it sounds like there is very little bass coming out of the cabinet now. Is proper terminal assigment important when connecting an amp to a receiver via high-level outs?
                      Yes- Bass is usually mixed mono at about the same amplitude in both stereo channels. Disconnect one side at the receiver speaker terminals and see if your new sub sounds louder. If so, you probably have one side reversed somewhere. Also try it on the SD215-88 too. You want the two sets of terminals on this woofer in parallel, so + to + and - to -. It's easy to get it backwards....I know from experience:o
                      Co-conspirator in the development of the "CR Gnarly Fidelity Reduction Unit" - Registered Trademark, Patent Pending.

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                      • #12
                        Re: Subwoofer question

                        Originally posted by CAPGuy View Post
                        Ok so I built the cabinet today. I still haven't fine-tuned the passive radiator yet, but there is definitely some bass coming from the driver now that I've hooked the dual voice coils in parallel. Although I still have to turn the gain up to 50% before hearing an appreciable amount of bass. This is fine, its just I've heard from other sources that even 20% gain should be sufficient. Oh well.
                        Probably the "other sources" where driving the sub amp with the line level inputs (Hi impedance - RCA inputs).

                        With the way you are doing it, using the speaker level inputs, my guess is that the input sensitivity of the sub amp amp with these inputs is way less than using the RCA Hi Z inputs. Thus you would need to turn up the volume to compensate for the lack of input sensitivity using these inputs.

                        Comment


                        • #13
                          Re: Subwoofer question

                          Yup, suspicions confirmed. When you reverse the polarity on one of the high level inputs, you get very little bass. This thing is kicking now! Even at 3 notches, it's rattling my windows.

                          The quality of parts coming from PE is absolutely amazing.
                          Thanks for your help guys.

                          Comment


                          • #14
                            Re: Subwoofer question

                            This being my first speaker project, I figured I'd show you guys the results.
                            The bookshelf speakers took about a year of on/off work, and the subwoofer was finished in about a day. Still have to paint it black :D

                            Click image for larger version

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                            I think I've been bitten by the bug. Now I'm eyeing the Tri-trix design haha.

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