Advice on subs

sovereignsovereign
edited December 2013 in Amplifiers
Does anyone know anything About subs here?
Even though I have 15 inch open baffle woofers I'm wondering if I can increase the dynamic range with a sub, but it would have to be musical and integrate with the speakers.
Am I correct in thinking there are passive subs that work from the speaker terminals from the power amp and active subs that work from the pre amp?
Appreciate any advice.
Thanks

Comments

  • DocfosterDocfoster
    Yes. You are right.
    I had an active sub once (mordant short...?). It was definitely helpful when i had small dynaudio floorstanders.
    The sub had a "gain" knob and some sort of cut/roll-off knob that gave some control over the frequency up to which the sub operated.
    No idea what kind of beast you'd need to affect things with your 15 inchers tho...
  • uglymusicuglymusic
    I've heard a lot of subs over the years, and I've never liked any of them.

    The systems always end up sounding disjointed to me.

    Open baffles do struggle at the bass end, so I wonder if the answer is to move away from the OBs.

    OK. That's not the answer to your question, but there you go. 
  • sovereignsovereign
    Hi Ben, what was its limitations, why did you get rid of it ?
  • DocfosterDocfoster
    I used it with some dynaudio audience 62s. When i moved up to the 82s the sub wasn't digging much deeper than the 82s, and it "slowed" the music. The one i had wasn't very "fast" or "musical" like that. With the smaller floor standers, for me it added enough grunt to justify itself. But not with the bigger ones.
  • PACPAC
    FWIW James, I'd advise against the sub route. To do it properly, despite arguments to the contrary, you really need two subs.  There are several problems with subs.  Firstly, forget passive subs unless bespoke crossovers are used to split the operating range or they'll mess up the lower response. The room measurements have to be accounted for when determining both sensitivity and roll off point.  Secondly, your current amp will have it's work cut out considering passive subs, and thirdly, to do proper bass, with real texture at the lower end and to measure flat, they will have to be quite large (boxes).

    Active and driven by a preamp is the only way to do it half reasonably, but you'll get issues with group delay, so whatever sub is used must come with variable tuning to alter the crossover slope and volume (sensitivity).  You may find it almost impossible to get it to integrate properly with your OBs without a lot of homework or trial and error but in theory, it can be done and done well.

    As you're probably gathering, to get that far will cost possibly more than buying a new set of speakers (or building some) that do the bass in the first place. There is one solution though, so bear with me:

    Convert your OBs so that the bass units only are in sealed chambers and port the chambers. It will involve some tweaks to crossover and may involve extending the length of the rear chamber, but it'll work and done properly, wont be too demanding of your amplifier.
  • sovereignsovereign
    Paul your a legend, I'll reply properly later on today, but thanks in advance.
  • sovereignsovereign
    Ok I'm back.
    The bass that my ob's offer is very good and deep and holographic . I was just wanting to know if there was more to be had with a sub, but it has to integrate well with the speakers. The thing I appreciate about OB bass is its transparency and lack of congestion , just open and informative.
    The tweeter and mid woofer are completely open baffle but the 15inch bass driver has a massive open backed box on it, maybe 70cm deep by 60 cm high. My OB's do good bass but I was wondering if there was more to be heard with a sub.
  • PACPAC
    Nope...it'd muddy the sound and you won't have a hope of matching group delay properly which will cause more issues than it's worth. A sub with your mid/treble would work better, but running your bass unit and a sub would be nigh on impossible to get right.  You could tune the back box as a reflex enclosure by adding a little volume and porting (upward firing) and this would give you taughter bass with more impact, or you could close it off completely a la sealed enclosure (you;d lose bass depth and gain an upper bass peak) but in both cases, system Q would change and the crossovers would need re-designing.  The ported enclosure is possibly the better route.
  • sovereignsovereign
    Really informative Paul, thanks.  I'll leave it as it is I think. 
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