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

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  • #16
    Re: Just finished a pair of subs and they suck. Why?

    Ah c'mon, you can't blame problems like this on MP3 files. Seriously, if the source material were that bad it wouldn't take a new sub to hear it.

    I've never personally seen a sound card that couldn't drive a high-impedance amp input either. Commonly, the outputs on a sound card can drive headphones directly. So, provided the input impedance on the plate amp is north of 1K (kinda low for line level standards) I don't see an issue. Not to mention the OP saying it was also tested with a tablet and through the hi-level inputs from his mains amp. The tablet can definitely handle low impedance loads (again, made to handle headphones), and the DTA would be built for single-digit impedance loudspeakers. You can pretty much cross "sound card" and "impedance issues" off the list, IMO.

    Also, as to why test tones are louder -- well, think about it a sec. When you play a 60Hz sine wave at -6dB (a typical starting point in tone generators), that's a single tone 6dB below full scale. No music is going to have that much concentrated energy in a narrow passband. Not quite even dubstep.

    OP, I think your troubleshooting idea is sound. Run temp speaker wire through the port, and plug the driver into your car amp. That isolates your problem domain into either "plate amp" or "box + speaker". That narrows the field of troubleshooting steps considerably.

    So will being able to hear the problem ourselves. Procure that mic, pronto! :D

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    • #17
      Re: Just finished a pair of subs and they suck. Why?

      Originally posted by cooper View Post
      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
      "I may not always post a suggestion mere minutes after someone else, but when I do, It's on Parts Express Tech Talk!"

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      • #18
        Re: Just finished a pair of subs and they suck. Why?

        Originally posted by JeffKnob25 View Post
        Could your sound card crossover be set as a high pass instead of low pass?
        This would be my guess also. If you are sending a highpassed signal to the sub that signal will have to be very strong to get any bass and will be clipped.

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        • #19
          Re: Just finished a pair of subs and they suck. Why?

          Originally posted by SirNickity View Post
          Ah c'mon, you can't blame problems like this on MP3 files. Seriously, if the source material were that bad it wouldn't take a new sub to hear it.

          I've never personally seen a sound card that couldn't drive a high-impedance amp input either. Commonly, the outputs on a sound card can drive headphones directly. So, provided the input impedance on the plate amp is north of 1K (kinda low for line level standards) I don't see an issue. Not to mention the OP saying it was also tested with a tablet and through the hi-level inputs from his mains amp. The tablet can definitely handle low impedance loads (again, made to handle headphones), and the DTA would be built for single-digit impedance loudspeakers. You can pretty much cross "sound card" and "impedance issues" off the list, IMO.

          Also, as to why test tones are louder -- well, think about it a sec. When you play a 60Hz sine wave at -6dB (a typical starting point in tone generators), that's a single tone 6dB below full scale. No music is going to have that much concentrated energy in a narrow passband. Not quite even dubstep.

          OP, I think your troubleshooting idea is sound. Run temp speaker wire through the port, and plug the driver into your car amp. That isolates your problem domain into either "plate amp" or "box + speaker". That narrows the field of troubleshooting steps considerably.
          Bingo. Give this man a dollar.
          Isn't it about time we started answering rhetorical questions?

          Paul Carmody's DIY Audio Projects
          Twitter: @undefinition1

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          • #20
            Re: Just finished a pair of subs and they suck. Why?

            Alright, thanks for all the replies. I'll try to address as many suggestions as possible. I've got a video of the sub in action at the end of this post.

            - The crossover on the sub-out of my soundcard is definitely low-pass. I think that is the only one doing any real work. While the plate amp crossover does limit high frequencies, it does a terrible job. By itself, set @ 40hz, I can hear a 630hz sine wave. Don't blame this though, I use the sound card's crossover in addition in my tests and it filters the sound better.

            -I tried stuffing the port with socks etc. It did not affect the bad sound I am hearing.

            -Although I don't have the ability to measure clipping from my sound card, I highly doubt there are any issues with it. I've used it with both the DTA-100A and Emotiva UPA-500 and driven my speakers (OS MTM & MT), as well as various low and high impedance headphones, and it has been flawless. The specs for the card can be found here.

            -Most of the music I play is FLAC. The tones I use are FLAC, from a CD series published by "Focal JMlab".

            -I just double checked the dimensions, the internal volume of the box is 31.7 litres before bracing, port, amp and driver displacements. Seems right. Assuming 1 cu. ft. after displacements accounted for, the precision port should tune the box to 26hz.

            -I probably won't have time to hook up the subs in my car until the weekend.

            Anyways, here is a video that demonstrates the sound I am hearing. The video starts with my sound card crossover @ 50hz, and plays a 20-to-160hz sine sweep. Then some music starts, I lower the volume to my main speakers, then start gradually raising the crossover point from 50hz to around 200. You should be able to pick up the sound I am talking about pretty quickly. Near the end of the video I lower the crossover back to 50hz and the sound goes away. I recommend listening to this video without a sub to better isolate the noise.

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            • #21
              Re: Just finished a pair of subs and they suck. Why?

              Originally posted by SirNickity View Post
              Ah c'mon, you can't blame problems like this on MP3 files. Seriously, if the source material were that bad it wouldn't take a new sub to hear it.

              I've never personally seen a sound card that couldn't drive a high-impedance amp input either. Commonly, the outputs on a sound card can drive headphones directly. So, provided the input impedance on the plate amp is north of 1K (kinda low for line level standards) I don't see an issue. Not to mention the OP saying it was also tested with a tablet and through the hi-level inputs from his mains amp. The tablet can definitely handle low impedance loads (again, made to handle headphones), and the DTA would be built for single-digit impedance loudspeakers. You can pretty much cross "sound card" and "impedance issues" off the list, IMO.

              Also, as to why test tones are louder -- well, think about it a sec. When you play a 60Hz sine wave at -6dB (a typical starting point in tone generators), that's a single tone 6dB below full scale. No music is going to have that much concentrated energy in a narrow passband. Not quite even dubstep.

              OP, I think your troubleshooting idea is sound. Run temp speaker wire through the port, and plug the driver into your car amp. That isolates your problem domain into either "plate amp" or "box + speaker". That narrows the field of troubleshooting steps considerably.

              So will being able to hear the problem ourselves. Procure that mic, pronto! :D
              If I troubleshoot an electronic circuit I do so with a signal generator providing a clean undistorted signal.

              Same with an amp/speaker system. I don't start out with an already distorted signal (mp3) and then run it through some electronic circuit with cross-over points that may or may not be set properly (sound card) and which may add a bunch more garbage to the signal before it enters the system I am attempting to troubleshoot.

              If I troubleshoot an engine I start out with clean gas.
              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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              • #22
                Re: Just finished a pair of subs and they suck. Why?

                I'd be thinking something is wrong with the amp.

                Do you have a home AV receiver or anything like that laying around? Any other amp of some variety? Just hook up the output from your sound card through that other amp and see what happens.
                DARPA Jr - 2015 InDIYana Winner - RS180-8 + RS100P-8 + ND25FA
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                • #23
                  Re: Just finished a pair of subs and they suck. Why?

                  I posted my prior post before seeing the one with the video.

                  I just watched the video. Don't know quite what to make of that.

                  I stand by my earlier recommendation to start with a simple clean input signal. Don't enter too many variables at once. Forget about soundcards and attendant cross-over points. Check out your amp and speaker first with a basic clean signal and then worry about integration with your soundcard and subsequent cross-over adjustments.
                  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

                  Comment


                  • #24
                    Re: Just finished a pair of subs and they suck. Why?

                    That is a weird noise. No idea, it sounds mechanical.

                    Comment


                    • #25
                      Re: Just finished a pair of subs and they suck. Why?

                      I've heard clipping on a closed-box sub that sounds like a microphone with outdoor wind noise. I know clipping was involved in my case because the clipping indicator on the Bryston amp was flickering when the noise occurred.

                      For subs, higher frequencies require more power than low frequency - at least in the closed box case - according to Linkwitz. Here's a link to a page with the reasons why...

                      http://www.linkwitzlab.com/thor_splmax.htm

                      My money's on amp issues.
                      Bill Schneider
                      -+-+-+-+-
                      www.afterness.com/audio

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                      • #26
                        Re: Just finished a pair of subs and they suck. Why?

                        Many moons ago I had a Infinity sub (factory not DIY) and it developed a air leak. It was fixed under warranty, but the sound coming from the sub was awful and sounded a little like your problem.

                        It might be a totally different problem, but make sure your box is sealed for air leaks. Air should only be coming out the port.

                        In the video, it looks like the front baffle has a gap.

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                        • #27
                          Re: Just finished a pair of subs and they suck. Why?

                          Sounds like a loose voice coil or the VC impacting to me. Did you get these subs new? Also in the video the mounting flange and surround seem distorted. Perhaps you have a distorted/bent basket, causing a misaligned VC. How tight was the fit in your cutout? Maybe try loosening the subs or mounting face in.

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                          • #28
                            Re: Just finished a pair of subs and they suck. Why?

                            What % output are you using from your sound card? I find that I have less clipping issues and distortion when I don't run my computer sound card above 85%, you may want to try it with the sound card around 80% and the larger aplifiers up slightly higher to compensate. I don't know exactly what that sound is, but it definitely doesn't look like an excursion issue, but it certainly sounds like a mechanical issue.

                            What you may want to do is pull the speakers from the box, and at very low wattage, while watching your excursion very very closely, play your normal signal outside of the box. If it's a mechanical noise you will very easily hear it out of the box, if you only hear it in the box then I have no clue what to associate it to other than distortion from either your sound card output, the sub-amp, or a wizard sleeping the sub box beating the cone with a broom to get you to stop playing it so loud.

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                            • #29
                              Re: Just finished a pair of subs and they suck. Why?

                              I can get a similar sound from my Burro sub, using the sub calibration pink noise generator in REW - but that's with a very large signal and about as much excursion as I dare. I assumed it was amp clipping. Integrated with the speakers I haven't come close to those levels. This leads me to suspect your amp. Maybe try playing a sine wave and raising the gain until the onset of clipping, and check the voltage.

                              Agree that the crossover in the plate amp has a fairly shallow slope, but it seems to integrate nicely with the knob set fairly low. I'm running full range signal to the high level input on the amp.

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                              • #30
                                Re: Just finished a pair of subs and they suck. Why?

                                Yup, sounds very bad.

                                I'm breathing a slight sigh of relief that it's not the enclosure size or tuning.

                                I think it's a matter of figuring out if it it's the amp or the driver. There's not much else it could be (well, the source, but honestly I think some people are making a mountain out of a molehill by claiming you can't use an mp3 to test. That distortion sounds way worse than any mp3 file I've ever heard.)
                                Isn't it about time we started answering rhetorical questions?

                                Paul Carmody's DIY Audio Projects
                                Twitter: @undefinition1

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