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Just finished a pair of subs and they suck. Why?

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  • Just finished a pair of subs and they suck. Why?

    ****UPDATE: SEE POST #76 ON PAGE 4****


    I was hoping to be posting a thread in the Project forum by now, but I have to come here because I am very disappointed after all my hard work. I recently completed two identical Dayton RSS210HF-4 8" sub builds, using the volume and port specified in Paul Carmody's thread for the 'Pony', here. I modified the dimensions of the Pony to accommodate a 2"x12" precision port instead of the slot port, as well as some internal bracing.

    Some select pictures of my build can be found here.

    The subs are powered powered by Dayton SA70 plate amps; I've had the gains set at about 2/3. I've tried my Xonar DX sound card, Sandisk mp3 player, and Asus tablet as sources. I've also tried using hi-level inputs from my DTA-100A.

    The port is 2" in diameter and is 1 3/4" away from the back of the baffle. I don't think this is an issue because of the very large flare on the tube, if you measure from where the port is 2", it's more like 3+ inches of space.

    Now, onto my issue.

    The subs sound like crap. Both of them. I know these particular ones aren't supposed to get that loud, but if I raise the volume to anything reasonable I start getting bad sounds. With the crossover on my plate amp set to ~70hz, and the crossover on my Xonar sound card set to 50hz, some songs sound okay, but others get some bad sounds happening. The best way I can describe the sound is a mix between radio static, wind buffeting a microphone, and a speaker bottoming out.

    My first thought was it must be reaching excursion limits. The only thing is, it doesn't look to be doing that. The sub had much greater excursion when I was playing test tones in the 20-40hz region, even to the point of a good amount of port chuffing, but the bass was clean and I didn't get any bad sounds. Also, when I raise the crossover point on my sound card to 80hz and above (keeping the plate amp @ 70hz), the bad sounds get much, much worse. It doesn't make any sense to me. If the sub can handle the song at a 50hz crossover, why does it start crapping out at 80? If I remember correctly this driver has been used with an 800hz crossover in some speakers designed by Wolf.

    I was going to post a video but my webcam's mic wasn't good enough. Maybe when I get my EMM-6 back from a friend I can get a recording of the sound.

    Any help is appreciated. I'm pretty bummed because as of right now these subs are near worthless to me :/
    Last edited by Exarch; 04-28-2015, 02:41 AM.

  • #2
    Re: Just finished a pair of subs and they suck. Why?

    Something along the way must be hard-clipping. 70w should still be enough power to get you over 90db.

    Either

    1) All of your sources are under-driving the inputs of the plate amp
    2) The amp itself is just struggling with the 83.5 db load.

    I would start by raising the gains all the way.

    But what I would really do to test is run the subs off the more powerful DTA-100.
    :blues: Flat frequency response, a smooth sound power response free of resonance, careful driver-integration, and high dynamic range both upward and downward :blues:

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    • #3
      Re: Just finished a pair of subs and they suck. Why?

      Originally posted by GranteedEV View Post
      Something along the way must be hard-clipping. 70w should still be enough power to get you over 90db.

      Either

      1) All of your sources are under-driving the inputs of the plate amp
      2) The amp itself is just struggling with the 83.5 db load.

      I would start by raising the gains all the way.

      But what I would really do to test is run the subs off the more powerful DTA-100.
      Agreed, especially the last part. Just hook them up to that amp and run it full range.

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      • #4
        Re: Just finished a pair of subs and they suck. Why?

        Originally posted by chrisn View Post
        Agreed, especially the last part. Just hook them up to that amp and run it full range.
        You guys must be confusing the DTA-100A with a different amp. It is the 30WPC t-amp that isn't stable at the sub's 4 ohm impedance. I mentioned that I used it as a high-level source to the 70W plate amp instead of a low-level RCA input. It wouldn't be able to drive the subs.

        You have given me an idea though. If I have time tomorrow I'm going to bring one of my subs into my car and run it off my JL sub amp (340W into 4 ohms). I know the environment and equipment better and it will eliminate the plate amp + sound card etc from the equation.

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        • #5
          Re: Just finished a pair of subs and they suck. Why?

          My two thoughts for the months. As you move the cross-over frequency higher to the subs, the plate amps have to "carry more load" of more frequencies, and with just 70 watts to work with, going from 50Hz to 80Hz, I wouldn't find it strange to get worse sound from them. Try playing the output from your soundcard thru the DTA-100a, then use the high-level outputs from it into the plate amps. Your soundcard maybe an impedance mis-match to the plate amps (very likely). Soundcards can be fussy. Some of this stuff I've quit trying to "think through it" and just accept it doesn't make sense sometimes...but it might work.
          Why does your vehicle (under warrantee) miss bad, check engine light comes on, Pep Boys/Advance Auto checks it and says "You're throwing a hard code on cylinder #2." For 2 weeks you limp around 'til you can get into the dealership, they take it in, keep it a couple of days while you bum rides, they call you, "We can't find a thing, it's running fine." And it is. And does. For two days.:rolleyes:

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          • #6
            Re: Just finished a pair of subs and they suck. Why?

            Somethings not right. Even at 1 watt they should be playing what 85db? I would hook up my sound card to the DTA and run them to the line ins on the sub or if you have an LFE channel run that to the sub and see what it sounds like. Or just run it full range and see what it sounds like.
            "What lies behind us and what lies before us are tiny matters compared to what lies within us." -- Ralph Waldo Emerson

            Projects:
            1. Melodious Monitors: https://skydrive.live.com/redir?resi...DsO7QEFSodJMEk

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            • #7
              Re: Just finished a pair of subs and they suck. Why?

              Maybe over damping...some say none needed for a sub box.
              I don't put much in mine, let the drivers do the work.

              Long time ago; made huge cabs, expensive 12" woofers, 2 big duds! I used that same foam as in your pics.

              Nice work btw!

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              • #8
                Re: Just finished a pair of subs and they suck. Why?

                You could make a simple wallin jig and measure impedance to verify tuning.

                But my guess is something is clipping in the signal chain.

                It is interesting that you say there was more excursion when running test tones. Did they also sound better?
                Salem

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                • #9
                  Re: Just finished a pair of subs and they suck. Why?

                  Those boxes look well built. Try stuffing the port with foam to see if the noise is port related (doubtful). Other than that, it would have to be your source. Do you have a plain old A/V receiver with a sub out?

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                  • #10
                    Re: Just finished a pair of subs and they suck. Why?

                    Could your sound card crossover be set as a high pass instead of low pass?

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                    • #11
                      Re: Just finished a pair of subs and they suck. Why?

                      Do you have a good old fashioned CD player to RCA jack right into the inputs on the sub amp? It's amazing how low the output level is on those smaller portable devices compared to a real component output on say a CD player, home theater amp or something like that. If you had say a 150 watt sub amp driving it combined with the lower voltage of the smaller source devices, you might not notice any issues, but with the 70 watt unit, that is probably what's making the difference here.

                      The box looks awesome by the way. Don't worry, you'll get it figured out. I suspect it's just lack of input voltage from your source.

                      What did you play the test tones from? They always seem to play louder/cleaner to me for some reason as well.

                      Also, is it possible that the phase is reversed on one of the subs, that's a good possibility as well for reduced output. Even in both amps are switched in the same position, it's possible one is reversed from the other.

                      TomZ
                      *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                      *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                      *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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                      • #12
                        Re: Just finished a pair of subs and they suck. Why?

                        Could the two subs be firing out of phase with each other? You could unplug one and see if the other's output increases.
                        Edit - Sorry, Tom Z already suggested

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                        • #13
                          Re: Just finished a pair of subs and they suck. Why?

                          Sorry guys. I'm at work so I'll have to try these suggestions later; however, I'll mention that I've only played these subs one at a time, so there's no issue with them being out of phase with each other.

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                          • #14
                            Re: Just finished a pair of subs and they suck. Why?

                            Can you post the exact sound card you have?

                            Double check to make sure you are actually using the sub out. As already suggested, double check the sound level output going to the sub. Where do you have the volume set on the sub?

                            In the future, you might want to listen to speakers before doing a final finish on them. I always have. I know you can't change anything now, but next time.

                            They do look good BTW.

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                            • #15
                              Re: Just finished a pair of subs and they suck. Why?

                              Originally posted by tomzarbo View Post
                              Do you have a good old fashioned CD player to RCA jack right into the inputs on the sub amp? It's amazing how low the output level is on those smaller portable devices compared to a real component output on say a CD player, home theater amp or something like that. If you had say a 150 watt sub amp driving it combined with the lower voltage of the smaller source devices, you might not notice any issues, but with the 70 watt unit, that is probably what's making the difference here.

                              TomZ
                              +1

                              Get a good input signal in the form of a .wav file. Forget the crappy mp3 files and soundcard for testing.

                              As Tom suggests, plug in an old fashioned CD player and play some good source material.
                              Don't worry, if your parachute fails, you have the rest of your life to fix it.

                              If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

                              Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

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