In search of a new low

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  • AndrewM
    Senior Member
    • Oct 2000
    • 446

    In search of a new low

    Well it looks like my plans to move to front projection are...uhhh...panning out, so I'm thinking it's time to upgrade my single sealed Tempest (read: Big ass box that looks very ugly, but is well hidden for now) to something else. So I'm looking at a couple of different options and looking for some advice and to see what kind of ideas other people have.

    So basically with the opening up of the front of my room (no more TV stand, audio rack being moved behind me....just LCR and a screen up front) I had a couple of ideas, but here's what I'm looking for in order of importance;
    1. Sound quality: First and foremost on the list it has to sound good, not just for HT but for music as well.
    2. Price: I haven't really set a budget yet, but I'm not afraid of spending money to get something special.
    3. Has to be simple to build, I'm not that bad at wood working and such, but you can forget about me wanting to try and build odd-shaped enclosures.
    4. Extension: I'd like to cover the full 20-80Hz with no problem, my sealed Tempest hits -3db at around 19/20Hz right now. But again if I can get really close but get a good jump in SQ I'll take that sacrifice right now.
    5. Volume: This is a very distant 5th, I'm an apartment dweller so being able to rock on with 130db at 20Hz means zip to me. My typical movie watching is done at around -10/15 db below reference level. My low Q tempest with 250w is capable of more volume than I need right now for reference.

    My various thoughts.
    1. Keep the Tempest and add a couple of PR's and build a cabinet like the Adire Alignment (to mimic the curve of a sealed box with a little more extension). Or even add a couple of vents instead of the PR's, but my idea of an enclosure would be short and wide (like 30"Wx20"Dx20"H as a few numbers throw out there).
    2. A couple of DPL-12's in the same style box and sealed using the BFD to get me that last little bit of extension.
    3. 4 Tumult's and a couple of K1's...errr I was thinking of grabbing one in a sealed box with the BFD and a big amp, but I think I may be better off waiting until I'm a homeowner for such capabilities.
    4. - ????

    I'm not set on Adire, I've looked at the AV12/15's but I wouldn't make it into the pre-order, but maybe a couple of AV12's in a sealed box with a lot of EQ, but I doubt I would make use of their capabilities over say the DPL12's.

    And that leads me to my last question. What makes a sub sound good or bad over the next one in the line. Everybody likes to talk about how good the driver is when it's playing at SPLs that would make my eyeballs explode in my head, but how about at normal levels? What do I gain or lose by say picking up a $600 Focal Kevlar 15" driver over a $150 Tempest? I know I lose some extension right off the top and gain some effeciency, but how about sound wise? What makes one sub sound different/better than another despite both using "quality" drivers in quality enclosures?

    Andrew
  • PMazz
    Senior Member
    • May 2001
    • 861

    #2
    I'd go with a Tumult in a sealed enclosure with one of those new PE high power plate amps or maybe Rythmic's plate amp with LT. If a sealed Tempest gets you where you need to be in extension, a Tumult will give you about the same with less distortion. To upgrade later on, add more power and get more output.

    Pete
    Birth of a Media Center

    Comment

    • JonMarsh
      Mad Max Moderator
      • Aug 2000
      • 15261

      #3
      Ah, sound quality in subs.... you'll get many different answers on that one, oftem times resembling the old Rudyard Kipling fable about the blind men and the elephant, where each man is touching and describing a different part of the element.

      Well, I guess my "opinion" is worth as much or as little as anyone else's, so I'll chime in with my 0.02, but first I'll start by saying that given the requirements/general goals you have described, especially not very high output levels, any move you make from your current system may be more of a sideways move than an improvement.

      I'd seperate quality discussions into a few main areas- frequency response and Q, output capability (Xmax X Sd at it's most basic), and distortion. Enclosure effects (stiffness) affect percieved quality because of wall radiation in addition to driver output.

      Now, most common problems affecting quality in frequency response are low bass extension, upper and high bass extension, and Q at the LF roll off.

      Low bass extension needs little discussion- it's the factor in being able to produce the "palpable" low end, especially on special effects for movies. DVD has extended the range of LFE demands, the most severe movies go down to 10Hz in some cases. However, I undertand your issue about apartment or condo/townhome listeners- this often isn't practical except for single family homes with tolerante spouses.

      Upper bass extension is often neglected- but this is very important for integration with the "mains" system, and is a more frequent problem than most would expect, especially with high excursion sub drivers. The reason is that the voice coil inductance in long throw drivers often starts rolling off the frequency response well before cone breakup modes- as low as 70 Hz or so. This can be equalized out quite successfully- it's feasible, for example, to cross over a Blueprint driver or Stryke HE-15 at 80 or 100 Hz, but only if you equalize the sub flat to 150 Hz or higher, then apply the conventional electronic crossover. Otherwise, you have additional roll off and phase shift due to the driver, which is not present in the crossover, and you can't get a proper summation in the crossover region.

      The other frequency response/time domain issue is driver Q and setting time on transient steps. Along with the upper bass flatness, this has a great deal to do with the subjective impression of "speed" in a woofer, as a higher Q woofer at roll off actually rings somewhat, and smears in time the transient information. Worst offenders are passive radiator based systems; next worse are conventionally ported systems, to varying degrees, depending on the alignment; next worse is sealed sytems with small boxes and high Q; best is low Q sealed alignments and infinite baffle systems (which are just variations of the same thing).

      If you have Excel, Unibox can be used to model your driver and enclosure, and also show the expected transient response quite well.

      If you handle the above issues well, which your existing Tempest works fairly well, if not in a small box, then the rest is driver distortion and output capability. Of course, many folks don't like big boxes, and so may be willing to spend money on a (much) bigger amp, EQ, and long throw driver with large magnet to allow reducing the sub cabinet by 50% or more. Done carefully, you can get comparable results, but at a price. For example, while 250-300 watts is plenty of juice for a Tempest, a Tumult or HE-15 will really want a kilowatt or more, depending on cabinet and tuning.

      ~Jon




      Earth First!
      _______________________________
      We'll screw up the other planets later....
      the AudioWorx
      Natalie P
      M8ta
      Modula Neo DCC
      Modula MT XE
      Modula Xtreme
      Isiris
      Wavecor Ardent

      SMJ
      Minerva Monitor
      Calliope
      Ardent D

      In Development...
      Isiris Mk II updates- in final test stage!
      Obi-Wan
      Saint-Saƫns Symphonique/AKA SMJ-40
      Modula PWB
      Calliope CC Supreme
      Natalie P Ultra
      Natalie P Supreme
      Janus BP1 Sub


      Resistance is not futile, it is Volts divided by Amperes...
      Just ask Mr. Ohm....

      Comment

      • AndrewM
        Senior Member
        • Oct 2000
        • 446

        #4
        Here's another question for the group then, what effect does cone material have on a sub? We see paper (and modified paper) and metal cones fairly often with the popular DIY drivers (Adire, Stryke, PE, the old BluePrint), but what about the more esoteric brands out there offering carbon, kevlar, fiberglass, crushed pearls....errrr What I'm getting at is that when designing a "full range" speaker system that is often a consideration, how the cone material will effect the sound and is that what I want. Does it apply for the lower octaves as well?

        Andrew

        Comment

        • GM
          Junior Member
          • Oct 2002
          • 5

          #5
          It's all about damping and BW. If you look at a compression horn and some IBs, you'll see they have the best step response, etc., due to an overdamped Qtc of <0.4 and high Qms so that the motor/signal is the controlling factor.

          You also ideally want a driver that has a wide enough flat BW to cover the XO BW, then smoothly rolling off, so Le must be low and the diaphragm must have the right amount of damping. You get what you pay for IOW, and why good prosound LF/midbass drivers are pricey.

          To get some semblance of this kind of performance in a reasonable sized box requires either a LRT controlled or isobaric design, so theoretically one or more Labhorn drivers might fill the bill. Before the LRT it was either IB or aperiodic. Not having heard an LRT controlled sub, I can only recommend the alternatives.

          If cost isn't a factor and you don't mind a big box under the screen, then a NorthCreek Leviathan in ~15ft^3 tuned to ~10Hz with dual 15" PRs gets my vote, though leaving it sealed for now and uncorking it for those <20Hz special effects once neighbors aren't an issue is probably best considering you're an apt. dweller.

          For really low LF with a low/steep XO, say 32Hz/4th, it's all about displacement since our hearing acuity sucks down low. Here, you're better off using a large BP design like was used for special effects for movies such as 'Earthquake'. These require stiff/massive drivers such as a 2x mass loaded Leviathan or multiple smaller drivers to get the desired specs.

          GM




          Loud Is Beautiful, If It's Clean
          Loud Is Beautiful, If It's Clean

          Comment

          • ThomasW
            Moderator Emeritus
            • Aug 2000
            • 10934

            #6
            The cones should be stiff/rigid. One pays a premium for exotic materials = metal or ceramic cones.

            Cones like those used in the Adire products; pulp with a layer of epoxy and carbon fiber are very stiff and and available at more reasonable pricing.

            For sub applications I have a yet to hear a sound quality difference between the exotic material vs paper/carbon fiber cones.




            theAudioWorx
            Klone-Audio

            IB subwoofer FAQ page


            "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15261

              #7
              The exotics are relevant if you're going well up into the midrange, and trying to avoid cone breakup. But even well designed paper/kevlar fiber composite cones such as Adire, Dayton, and the other bang for the buck guys use normally don't have break up issues until 400 Hz or higher, which isn't subwoofer turf.

              Finally, nice weather here in Austria. Getting a little tired of the food, though... speaking of exotic!

              ~Jon




              Earth First!
              _______________________________
              We'll screw up the other planets later....
              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
              Minerva Monitor
              Calliope
              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saƫns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
              Natalie P Ultra
              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment

              • Dennis H
                Ultra Senior Member
                • Aug 2002
                • 3791

                #8
                If you're a fan of Siegfried Linkwitz (who isn't? :amen: ) non-linear distortion is a biggie when you're trying to select a "musical" bass driver. After you have the driver selected, you need to decide how many of them to use and what box alignment and/or EQ will give you the LF response you want.

                If you want it to play as high as 80Hz, there are big differences in the distortion of the popular subwoofer drivers. The page below has SL's favorite test for a bunch of them. Click the 80Hz pics. A perfect driver would show only the 80Hz tone with 72Hz and 88Hz tones 6dB lower. Anything else, besides those 3 spikes, is distortion. As an example, the Peerless XLS has distortion products at least 10dB lower than the DPL12 at 80 Hz. However, at lower frequencies, the DPL does quite well.

                Comment

                • ThomasW
                  Moderator Emeritus
                  • Aug 2000
                  • 10934

                  #9
                  His distortion testing set-up is to say the least 'interesting'..... :rollhead:






                  theAudioWorx
                  Klone-Audio

                  IB subwoofer FAQ page


                  "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                  Comment

                  • Dennis H
                    Ultra Senior Member
                    • Aug 2002
                    • 3791

                    #10
                    My personal favorite is the pic of him building speakers in his hotel room in Taiwan. Hey, I guess the true DIYer makes do with what he has.

                    So Jon! Make some MDF dust while you're wasting time in all those hotels! The cleaning staff will love you for it! :banana:

                    Comment

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