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Subharmonic Synth and Amp question

Discussion in 'Amps and Cabs [BG]' started by Chris_AtariDoll, Mar 10, 2003.

  1. Chris_AtariDoll


    Dec 8, 2001
    Im thinking about getting a subharmonic synth (DBX 120) and i was just wondering if my current rig will be able to cope with the extra lowend.

    Warwick Pro-Fet IV
    Behringer Composer Pro
    Warwick 2x10 and 1x15
  2. I run the DBX 120a box (identical) and it drives hell out of my subwoofers between 26 Hz and 55 Hz.

    As much as I like the DBX box, I'd check around a bit more. First, the box only operates on fundamentals between 55 and 110 Hz, or A to A. I'd like mine to operate on a wider range. Behringer makes a similar box, similar price, but I have no experience.

    Next, there is no foot switch to activate the synth function. This is done by a push button on the front panel. It is a bit inconvenient to reach over and turn this on in the middle of a tune. I'd really like a foot switch.

    On the positive side, the synth tracks VERY well, is quiet and works well.

    You will need speakers FULLY capable of handling the big bottom end, or you will blow them out at stage volume.
  3. The DBX 120XP Subharmonic synth is a subtle box that can also be used as a dramatic effect if need be. I used to run mine on all the time as a way of re-inforcing the fundamentals of my bass rig. This box really helps if you feel the need to "deepen" your current amps range and is brilliant at this IMO; this would be the more "subtle" method. If you want to use it as an "effect" like ol' BG here does you'd have to get some sort of A/B box to switch it in/out of your effects chain. I used to use a full MIDI DMC GCX set-up with all my pedals stashed away in my rack; I only used the DBX as an "special effect" back then and used the switch-able loops of the GCX for that. I think it's better put to use as a subtle enhancer left on all the time. You can adjust the level of the effect to the ability of your speakers so i wouldn't worry too much about your rig being able to "handle" it. Just be v e r y careful because you can blow a driver. I run mine with my 2x12's and they handle it just fine. I can only imagine what they must sound like with BGavins rig.
    Amazing and useful box tho'....
  4. redneck2wild


    Nov 27, 2002
    Memphis, TN
    I have blown a number of speakers over the years with my DBX 120XP (mostly club PA speakers - I always warn sound guys but they tend not to listen).
    You have to be careful with the 26Hz-36Hz frequency band as many speakers can not reproduce these frequencies very well.

    What I have found that works for me is:
    1) Run a Biamp Rig
    a) So that the ultra low frequencies are not sent to the high channel. This helps protect the life of smaller speakers found in the High Cab.
    b) Distortion in one channel does not affect the other. You may not hear distortion in the Subharmonic channel but it will affect speakers.
    2) Run a Limiter on the Low Channel
    a) This will limit the peaks in the Subharmonic signal which could damage speakers
    b) If the limiter is only on the Low channel, you will still get your dynamics from the High channel.
    b) Furman has a similar product, Punch, that does not track as well as the dbx but has a built in Limiter.
    3) Run a small amount of Compression on the signal going into the dbx 120xp.
    a) This helps the tracking and helps prevent distortion in the peaks.

    My normal Rig consists of a 4x10 and a 1x18 but I add an additional 1x18 for clubs that do not have PAs that can produce the subharmonic frequencies.

    You can get a good rumble with the dbx 120xp with a 4 string but it will not create frequencies an octave down on the notes from G down. It produces the fundamental on these notes.

    Peavey also has a similar product that I heard a band play with last weekend. It sounded like it had more clarity than what I get from my dbx 120xp (but I have had mine for 10+ years).
  5. Wow...10 years, cool. I have always kept that 26-36 freq. band turned pretty much off to protect my drivers. 36Hz is often low enough for me anyway.
  6. redneck2wild


    Nov 27, 2002
    Memphis, TN
    If I use 2 18s I turn the 26hz band all the way up otherwise I leave it in the Middle (with 1 18). The 36-5? band I leave in the Middle.
    Its the 26-36 band that really makes things rumble but it is also the one that can damage speakers.

    In the Early 90s I would blow a 15 every few months until I started using a limiter on the low channel. I think the extreme frequencies somehow heat the voice coil to a point where something eventually melts (I could always find burnt marks on the speakers after blown - sometimes before they would blow). I have not had this problem with 18s though.
  7. Chris_AtariDoll


    Dec 8, 2001
    Would it be worth adding a dedicated sub? Im into my car audio, so would it be a idea to build a sub enclosure using a high SPL car audio sub, just to reproduce the low end?


    Would i be better adding an extra amp to drive the 15?

    Also, has anyone tried the Behringer Subharmonic synth? i can pick one up for about £50. How does it compare to the DBX?
  8. Car subs are not high SPL. They are high power... big difference.

    I run Rockford RFR-2215 (15") car subs and they are not very loud, but they are ferociously power hungry. And they will blow the doors off the commerical cabs in the bottom end. The cost is the 900 watts required to drive a pair of them hard enough to keep up with my JBL 10's running at 75 watts.

    Each of mine is 89 SPL which is MILES down from a high efficiency cab such as an Eden. You will need a minimum of two subs to play in average loud venues such as bars.

    Unless you have a means of balancing the (weak) sub output to the hot commercial cab, the sub will get lost in the mix. Bi-amping is the best way to go when using subs. This means an active crossover and a two channel (stereo) power amp capable of putting out 900 watts into 4 ohms, per channel. I run a QSC PLX 3002 for this.
  9. Chris_AtariDoll


    Dec 8, 2001
    I am talking to a guy i know who builds SPL competition cabs about building me a sub cab for my rig, I will let you know how it goes. What frequecy response should i be looking for??? anything else to take in to account?. It will be getting over 1000W from a seperate power amp.
  10. I'd be very interested in hearing what you come up with? Please keep us updated. What drivers will you be going for? I am considering converting one of my EB-MM HD212's into a sub using car audio components. I would suggest a 4 ohm cab for sure just so you can get the most out of your power amp. Flat to 30Hz would be ideal in my books buit BGavin's go even lower I think!!

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