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Thread: Help with speakers and amps

  1. #11
    Quote Originally Posted by Bill Fitzmaurice View Post
    If you do that the mains won't have the lows filtered out.
    It was stated that the tops have inbuilt crossovers (3-way, although I didn't see the cabs having mid drivers.. as to what's "quasi" 3-way is another thing, I looked it up and it means "seemingly" but on the active crossover end it's 2-way, whereas with 3-way you'd have control over the low/mid/hi components).. running them via processor gives more control but risks damaging them; ie. adding more devices like filters, compression etc in the signal chain which is also considered reducing overall sound quality, as does bi-amping into the cabs (I highly advice not to but there could be people who do or have done so)

    That will cut their effective power handling by 75%
    I highly doubt this is an official, exact figure but very likely so (edit : for example I wouldn't calculate overall power consumption based on it but it's a rough estimate of the power the part of the system sees).. the rig may end up sounding "thin" if improperly xovered though.

    For instance, many active tops are designed to be run as full range on their own and processed (high-passed, DSP etc) with a sub.

    I used to run my old passive rig with a mixer sub out (LPF) to a compressor/limiter and full range tops (15" tops&15" sub) which offered little to no control over the rig except for volume (and mixer EQ, it could've benefit from many things like GEQ, crossover etc but I kept it simple until I got an active system)

  2. #12
    Quote Originally Posted by efinque View Post
    It was stated that the tops have inbuilt crossovers
    The internal passive crossovers split the signal between the woofer and HF horn. They do not high pass the woofer. The electronic crossover does.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  3. #13
    Quote Originally Posted by Bill Fitzmaurice View Post
    The internal passive crossovers split the signal between the woofer and HF horn. They do not high pass the woofer. The electronic crossover does.
    Yea I was thinking the same.

    But high-passing a sub (or any driver, with low frequencies it's more pronounced) without factory suggested parameters is sort of risky.. active sub manufacturers do this on the regular though (and midtops/fullrange too but they have it calculated and engineered whereas us hobbyists may risk blowing a couple of drivers before getting it right)

    Some CD horn manufacturers offer frequency response plots etc, as well as some sub plans I've seen advice using a HPF (such as scoops) but most amplifiers have fixed freq response, ie. they don't go lower than 30Hz.. if this was the case you'd work at a cinema or something.

    EDIT : think of it this way; the recording engineer sets a HPF with a +3dB peak or so, so does the mixing engineer from his desk, then the mastering engineer puts yet another HPF as does the sound guy in his processor, and then the DJ mixer has filters too.. all those peaks fold and summed together we're talking an 8-10th order HPF in theory, although the intention was good, to get rid of the rumble it could make things worse. In practice recorded music is analyzed so as such peaks wouldn't exist but everything's possible (the discussion whether to use 6, 12 or 18dB/oct filters etc).. you'd basically EQ it out, preferably within the crossover but it requires an RTA (real time analyzer, in the frequency/spectrum domain) and a 2x31 band graphical EQ or per channel GEQs in the xover (I never bothered doing much else than low/hi cut to 30Hz-20kHz with 12dB/oct and normalize during mastering)

  4. #14
    Quote Originally Posted by efinque View Post
    But high-passing a sub (or any driver, with low frequencies it's more pronounced) without factory suggested parameters is sort of risky..
    There's nothing risky about it at all. Not high passing any driver so that it's not being fed with frequencies lower than it should be is risky.

    think of it this way; the recording engineer sets a HPF with a +3dB peak or so, so does the mixing engineer from his desk, then the mastering engineer puts yet another HPF as does the sound guy in his processor, and then the DJ mixer has filters too.. all those peaks fold and summed together we're talking an 8-10th order HPF in theory,
    Think again. That simply does not happen.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  5. #15
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    My mains are the jbl's and they have built in crossovers. Each has 2-15" speakers and a horn on top.

  6. #16
    Quote Originally Posted by Darman View Post
    My mains are the jbl's and they have built in crossovers. Each has 2-15" speakers and a horn on top.
    Dual 15"s can do full range easily, it's a matter of taste/extra control over the system (and they last longer which is the main point here I think)

    For example an Eminence Beta 15 goes down to approx. 43Hz so with JBL 15" woofers there shouldn't be a problem.

    They don't do bass quite like a dedicated sub/folded horn does, they're simply not meant for that because the enclosure is ported/tuned to act as a vocal/PA reinforcement and as such are required to have sensitivity in the low/midrange (think of it as a large guitar amp cab minus the AC hum)

    Also they may lack in xmax/cone excursion which means they move less air compared to subwoofer driver (ie. you do get bass/sub but not the trouser-flapping kind, turning up the low EQ won't do much else than distort) but luckily you have the EL36's to deal with the low register..

    For the record lowest E1 on a bass guitar is 42-43Hz, double that and you get E2 which is ~80Hz and ~160 at E3 so there you have your ideal crossover points, on a keyboard C1 is ~30Hz, C2 at 60Hz, C3 at 120Hz and so on.. for example in dnb kicks are around 80-120Hz whereas in house/techno they're lower, like 40-60Hz generally but there are exceptions.

    With live bands the larger the bass drum is the lower it plays, smaller kits sound punchier though but you'd usually tune them in conjunction with the drummer. I think many studio kits are of the smaller kind to play back properly on home systems (and they take less space), whereas the more sophisticated studios use sub-kicks and unobtanium for the extended low end.

  7. #17
    Quote Originally Posted by efinque View Post
    For example an Eminence Beta 15 goes down to approx. 43Hz so with JBL 15" woofers there shouldn't be a problem
    There is a problem. Drivers made to work best in mains won't keep up down low with drivers made to work best in subs. The purpose of an electronic crossover is to have each speaker operate only within its ideal range. The penalties for not doing so range from bad sound to blown drivers and amps.
    For the record lowest E1 on a bass guitar is 42-43Hz, double that and you get E2 which is ~80Hz and ~160 at E3 so there you have your ideal crossover points
    Subs are run only up to where they're not directionally locatable. On average that's 100Hz, but it's lower with subs that have high THD, and it can be higher with subs that have very low THD. It has absolutely nothing to do with the content being played.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  8. #18
    Quote Originally Posted by Bill Fitzmaurice View Post
    Subs are run only up to where they're not directionally locatable. On average that's 100Hz, but it's lower with subs that have high THD, and it can be higher with subs that have very low THD. It has absolutely nothing to do with the content being played.
    There are upper harmonics depending on the instrument (in an "ideal" sine wave there aren't but it's another thing) but they are more quiet than the fundamental tone when measured mathematically, your ears may tell you otherwise though because of Fletcher-Munson curves.

    Many recorded pieces, esp. in pop and EDM etc use doubling some parts an octave higher, not only for harmonic content but because it generally translates better to consumer systems, in-ears etc.. ideally, with live stuff in theory you could emphasize the upper harmonics of the instrument so you could hear them better in monitors, using a semi-parametric/sweepable mid EQ I guess but it's yet one of those things sound engineers constantly argue about (and probably answers why some live recordings/bootlegs sound like crap because they were recorded directly from the desk)

    EDIT : in other words a bassline in low E would require a very capable monitor or the aforementioned bell EQ, I'm not sure whether it works but on paper it does.. or whether the system was intended for live use in the first place but it's a good thing to take into consideration since you never know (there's also a DJ technique known as harmonic mixing which emphasizes the key of the tracks and that they do not clash, I'm not very familiar with it though but I'd figure it's worth mentioning)

  9. #19
    None of that has anything to do with how high a subwoofer should be run.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  10. #20
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    A quasi 3-way crossover is a common config for cheaper dual 15 cabs like those JBL JRX. What happens is both drivers work at low frequencies but the lower 15 is low passed at about 500-600hz so only the upper 15 goes all the way up to meet the CD at 2khz, this eliminates the comb filtering that would occur with both 15" drivers operating at those frequencies. 15" drivers really should never be run up that high but large format compression drivers that can crossover at lower frequencies are quite expensive so they aren't found in budget boxes.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

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