Please help me cross over the subwoofers

Discussion in 'Monitoring' started by CherylJosie, Mar 12, 2017.

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  1. CherylJosie

    CherylJosie Active Member

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    This is not strictly a monitoring or recording question but I am having difficulty finding a good place to ask this question since most of the forums I found seem to focus on recording and mixing rather than live sound.

    I have begun mixing live sound for a band sort of at random because the drummer cannot run his gear while performing. I stepped in at his house party to cut the feedback and got nominated/appointed sound person despite my hearing issues and tangential background because there is no one else better qualified.

    They are using Mackie powered full range mains with additional Mackie powered subs, a Mackie mixer, and Master Fader on an iPad.


    They have the mains and subs overlapping in the sub frequency band. The mains are 3 way full range rated to about 35Hz and the subs rated to about 30Hz.

    The mains are 1200w with a 15" woofer and the subs 700w with 18" woofer. Their max dB is similar at about 135dB.

    I am considering setting up a crossover and high-passing the mains but not sure if this is wise, for many reasons.

    I found a document on Mackie's web site describing how to set up a crossover in Master Fader and I am electrical engineer but not a sound person. I can certainly implement that crossover just fine per the instructions and have already figured out most of it on my own anyway.

    The system is deafeningly loud even in a larger bar. I have not seen them perform at a really large venue though and doubt they would qualify anyway at this stage. They are still performing for gas money and earn more jamming acoustic on the sidewalk.

    So I think those subwoofers probably do not need the mains helping them out, but not sure what is the appropriate way to handle it. At this time the subs only have bass and kick on them, shared with the mains. I am planning to at least gang their input faders on main l/r and gang the aux subs on the main l/r with a VCA to at least make it easier to control the input and output levels, but I am uncertain what to do about the crossover.

    My idea is to cross over at 120Hz max frequency of the subwoofers rather than overlap with the mains. Should I do it, or leave them duplicating output below 120Hz?

    Thank you
    Cheryl
     
  2. Boswell

    Boswell Moderator Distinguished Member

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    Welcome!

    If you are feeding all the speakers from a single full-frequency mix, you should always employ crossovers between the subs/mids and the mids/tops. These crossovers need to be of the Linkwitz-Riley type to keep the phase response consistent through the crossover frequency range. There is a good introductory Rane article on this subject.

    However, you said that you are doing this for live sound, and so there is another method you should consider for driving the subs. This is called the aux-fed sub, where you generate a specific mono mix for your subs in your mixer and send it out through one of the mixer's Aux outputs. The mains/tops are fed using their normal crossover from the mixer main outputs. Doing it this way allows you to control which sound sources are put through the subs, and in many cases, it can make a sub/mid crossover unnecessary. For example, you could choose to send just the kick drum microphone and the guitar bass DI to the subs and not to the mains, thus removing a great deal of LF clutter from the main and top loudspeakers. It takes a bit of extra mixing skill to get the balance right and to mute the subs between songs, but the extra clarity you get through the main loudspeakers by not having to deal with heavy low-frequency components can be well worth the extra effort.

    Good luck!
     
  3. dvdhawk

    dvdhawk Well-Known Member

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    Hi Cheryl, and welcome to Recording.org.

    I realize it's not your gear, but model numbers would be useful if you have access to them.

    I believe you're right about avoiding the overlapping low-mids, and the subs not needing any help from the full range speakers.

    Mackie powered speakers have perfectly adequate crossovers built into them, specifically tailored for what each cabinet does best. Is there a specific reason you want to go outside the box?

    If it's simply because you don't want the overlap between the sub and the full range; connect your XLR mains from the mixer to the input(s) on the back of the sub(s), and then jump short XLR cables out from the sub to the full range cabinets using the sub's "HIGH PASS" Output connectors. That will eliminate any overlapping frequencies.

    You would only use the "FULL RANGE" Output(s) to jump to any additional sub cabinet(s), and repeat as needed.


    For instance the Mackie Thump18s has designated a fixed crossover point of 140Hz.
    The SRM series subs are set at 115Hz, but in "VAR" (variable) mode, you can dial the HPF anywhere from 60Hz to 120Hz. And as long as you use the "HIGH PASS" outputs, there's not going to be any overlap.

    If for whatever reason the overlap between 140Hz and 35Hz is desirable, then that's another case where you would simply connect your tops to the "FULL RANGE" Outputs on the back of the sub, and deal with the mess the overlapping low-mids is likely to cause with EQ.

    You could use Master Fader to adjust the crossover point by incorporating Post-Fader Auxes with the appropriate High-Pass-Filters and Low-Pass-Filters engaged, but it would complicate the cabling and iPad mixing. It complicates the cabling by requiring a homerun from the mixer Aux Out to the sub, plus a homerun to the full range from the mixer Main Output(s). If you're running in stereo, you'll need 4 homeruns. If you're running in mono, you would also have the option of jumping sub to sub, and full range to full range. To me, it complicates the iPad mixing just because of the limited screen space you get with Master Fader. The Auxes have EQ and HPF and LPF, the Subgroups only have EQ, the VCAs have neither.

    In my option it wouldn't yield enough benefit to justify doing it unless you really needed to constantly monitor and re-balance the subs vs. tops levels from the iPad.

    Also, is "deafeningly loud" what the band is shooting for? ( I know some that would be )
     
  4. CherylJosie

    CherylJosie Active Member

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    Thanks! Quick response!

    The speakers are Mackie powered 3-way full range, and Mackie powered subwoofer. Apparently they have something similar to the aux-fed sub but with some differences from that article.

    The subs are low-passed with the graphic EQ on the aux. The full range mains have a house curve on the graphic with mild broad bass boost slope of about -3dB/decade or so up to about 1KHz. The subs are rated to about 30Hz and the mains rated to about 35Hz.

    The mains are full range speakers and the mix they get is also full range. It includes the bass and kick, with the input faders on them separated between main and sub. Also, the output faders on the mains and aux sub are independent rather than ganged in a VCA.

    I was considering using the l/r main input fader to control the bass and kick levels on the aux/sub channel so that the tonal balance remains constant. However, the aux send may be set to post-fader as in the article already and if so it is already OK. I did not check and did not know to check at the time because I was unfamiliar with the gear.

    I was also considering ganging the main and sub output faders on a VCA to make the output levels track.

    This seems to be the original intent of the setup they are currently using.

    Yes well the problem is the skill. I have minimal experience at this. I was a warm body where there was none before.

    Apparently the drummer who set up this mix on his equipment also has minimal experience at this.

    So, now that I understand aux-fed sub (thanks for that!) I will have to go do some more reading and experimentation. It seems that the aux fed sub is superior for live sound so I will try to tune it that way.
     
  5. CherylJosie

    CherylJosie Active Member

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    SA1530z https://supportloudtech.netx.net/loud-public/#asset/10579
    SWA1801z https://supportloudtech.netx.net/loud-public/#asset/10600
    DL1608 https://supportloudtech.netx.net/loud-public/#/asset/9115
    Master Fader http://mackie.com/products/master-fader

    The subwoofers are designed to mate with the SA1521z but for some reason the drummer bought the SA1530z, runs them full range, and stacks them on the subs without a pole.

    I am trying to bring an existing setup inside the box. Since I had never before seen the aux fed sub configuration they are using, I was confused by it, so I started looking for more information here.

    The drummer seems resistant to making large changes to the setup he has. I also think, after reading about aux fed sub, it is superior approach, plus they are most of the way there already.

    I found this: Crossover with Matrix Outputs https://supportloudtech.netx.net/loud-public/#/asset/16525

    but have not read it yet. Still trying to sort out the rest of the details, and I only have access to the iPad at gigs.

    The SWA1801z manual says it is 120Hz 12dB/octave crossover but does not state if the lowpass is active all the time or only when the highpass output connector is plugged in. I presume the lowpass is always in circuit?

    If I try to run with this aux fed sub and the sub has its own crossover, what does that mean for linkwitz-riley? I would need to add another 12dB/octave low pass at 120Hz to the sub, and use a 24dB/octave highpass on the mains, with the frequency set to, what, 110Hz? Probably I need to tune it with a nearfield microphone and REW to do it properly?

    They are already running stereo mains and mono aux fed subs, I think.

    Yes, I noticed that at the last gig. I had to walk back the mains gradually toward the end of the night and that meant using the keyboard input screen because the sliders are just too coarse on the touchscreen, and I had to alternate back and forth between mains and subs to adjust by 0.5dB steps to keep the change smooth.

    My impression was that I can use the independent EQ on the l/r main and aux/sub to set up a crossover and trim the frequency response while still using the VCA to gang the output faders. I can also still use the output compression on the mains and aux/sub. Is that correct?

    Just about every band plays too loud for me, but yes, this band wants to feel it rattle through their bones. We are negotiating a compromise where I keep my earplugs in most of the time and try not to cause too much hearing damage for everyone else by moderating the volume as best I can without destroying the tactile completely.
     
  6. DonnyThompson

    DonnyThompson Distinguished Member

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    A common problem, unfortunately, and kind of a sign of their level of professionalism... I don't know why club bands are so often resistant to the fact that, the more in control of their stage volume they are, the better they will play, the more they'll be able to hear each other, and...the more control the FOH engineer has; which ultimately, allows you to provide better FOH mixes. And, the better the fronts sound, the more people listening will enjoy the band.

    I've seen bands where the guitar amps are stationed behind the players, and are blowing into the backs of their knees; so they complain that they can't hear themselves, so, they turn up.... but at a stage height of 3' or so, the people out in the audience are getting a full-frontal blast from the amps on stage.

    Until you get them to rein in the stage volume, you'll only ever be able to do so much, regardless of how good the PA is, or the way it is set up.

    Make sure they understand that you are not responsible for what they do on stage, and don't let them attempt to blame bad mixes on you, either, if the stage volume is such that it's an ungodly wall of white noise.
    There's nothing you can do if the band is so loud that you've got every fader on the FOH mixer off ...and it's still too loud.

    Oh, and welcome to RO, Cheryl. :)
     
  7. Boswell

    Boswell Moderator Distinguished Member

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    You've got several options here, Cheryl, but also several constraints, not the least of which is that your drummer set the system up and sounds as though he would not easily be convinced that a major change to the loudspeaker configuration is necessary. Dave (dvdhawk) has given an excellent view from someone with much wider familiarity with the range of Mackie gear than I have (it is not as common on this side of the Atlantic), and you have also explained more about how the system is currently configured.

    There was one thing you mentioned that really hit a nerve with me, and that is the use of graphic EQ units to perform loudspeaker crossover functions. This is normally a no-no, as the phase characteristics of narrow-band graphic EQs are not conducive to a smooth phase response through the crossover regions. The big exception to that is if you are talking about digital graphic EQs implemented using linear-phase FIR filters, where, by definition, the phase is controlled. However, FIR filters are more often used in studio mixdowns and not generally suited to live work because of the time delays they inject.

    You seem to have got a handle on the control of the balance between the subs and the mains, but possibly some further experimentation with VCAs (if your mixer has them) to control both at once would allow a more peaceful FOH workflow.

    My recommendation for experiment would be to continue with the aux-fed subs, feeding the kick and bass through them, but don't send these instruments to the mids/tops. Doing that would allow you to dispense with additional crossovers altogether, just using the LPFs built into the subs and feeding the remainder of the mix full-range to the mids/tops. In a lecture course I used to give many years ago, I had a demonstration where I sent a 1KHz sinewave to an 8" loudspeaker in a good-sized cabinet and then used a microphone in front of the speaker to feed a spectrum analyser. The 1KHz came out relatively clearly as a single line on the analyser until I mixed an unrelated 40Hz sinewave in with the 1KHz. The 40Hz was below what the loudspeaker cabinet would reproduce, but the loudspeaker cone was nevertheless going through the motions of responding to both the frequencies. The result in the spectrum analyser was that the 1KHz line got broadened by 80Hz due to the Doppler effect of the cone movement, an effect you could hear. This was to illustrate that, if you want purity of mid/high frequencies, you should try to avoid putting large-amplitude low frequencies through the same physical speakers.
     
  8. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    To me a dedicated crossover is the best choice. it can be tuned to the speaker array and even if you change the mixer you'll get the same accurate results. (and no phase issues like my friends and I fear.)

    Bos, I'm not sure about this. to make tests yes but for a gig ?? There is a lot HM & HF needed for a bass drum pressence and also for the bass.
    What I suggest 2 options ;
    1. Make use of 2 linear phase EQ if it's a digital board (one for the mains and one for the Aux Sub) and fine tune a crossover that way.
    2. Let the mains full range (to give some lows to pianos or other instruments) and make the SUB Aux pre fader, then cut the lows on the bass and bassdrum strip so they don't output low freq to the mains and use a low pass on the AUX Sub.
    No need to say an external dedicated crossover is a better choice.
    Also an option, you can still seperate the freq using the sub aux, but use the external crossover to remove lows to the top speakers.

    EDIT : Some external crossover can receive 2 full range signals. So you can send the mains and the Aux sub without eq and the crossover does the job ;)
     
  9. Boswell

    Boswell Moderator Distinguished Member

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    Yes, as an experiment. Sorry, I didn't emphasise that.

    For gigs, I have used a mixer to split the kick/bass in frequency by using up two mixer channels for each, then sending only the low end to the subs and the remaining highs to the standard mid/top mix. But phase problems are the enemy. I ended up doing it with analogue crossover boxes (Linkwitz-Riley filters) in the external insert loops, with the high/low outputs going to the returns on the two separate mixer channels.
     
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  10. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    I do a few big shows in the summer and the best setup I had to work with was a Yamaha M7CL (which has a dedicated sub fader)
    Mains and sub output of the mixer are sent to tuned crossovers which feed a line array. Man it's an easy job !!
     
  11. CherylJosie

    CherylJosie Active Member

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    They ride the line between Reggae tactile and 'wall of sound' and in that respect are about average loudness, if still too loud.

    The first gig I went to was a warehouse party and multiple bands all using the same equipment with the overhead doors open and most of us outside. They tested the limits of the system that time due to being isolated and having full autonomy. That is what I was referring to when saying that the system is unbearably loud. I was trying to point out that it seems the subs do not need any additional bass from the mains that should be highpassed.

    Another band I hang with uses tiny amps with large speakers in them, set on the floor and angled up. Personally I am not a fan of the sound but the light small boxes are easy to move and mic.

    I make that argument with virtually every band but I only find one in ten drummers that knows how to play fast AND light at the same time. Those needing to pound the drums seem to do it for the recoil as much as for the tactile.

    In this case I think probably the drummer and the rest of the band just prefer the tactile for the Reggae dance feel. I think the audience does also.

    I prefer drummers who not only keep the volume down but also take advantage of the lower level to spice up the dynamic range. It makes the music cut through better without drowning out conversation and it feels more satisfying to me when hard hits stand out because they stand alone. But that is not Reggae and not even pop. That is more suited to jazz and classical.

    Actually I am the one who is usually too critical, and sometimes too experimental, being inexperienced at this. They are just glad to have someone moving the faders for them.

    Thanks much, seems like a great community and I wish I found it sooner.
     
  12. dvdhawk

    dvdhawk Well-Known Member

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    I think the main question is for you, Cheryl, .... do you enjoy doing it? Because you've already demonstrated a good grasp of the mission at hand, and if you're not careful, you might create a demand for your sound tech services if you've also got a musical ear. And honestly, there's very little 'upside' if you don't like the work. Your engineering mindset is serving you well in sorting through this, and I'll be surprised if you don't eclipse the PA owner by mid-week. Kudos to you for doing your homework and reading the manuals, it's a lost art.

    You're doing great, but I'm going to just throw out some random notes for your consideration, and a couple questions at the end.

    • If you have a PA system that's balanced and optimized based on the strengths of individual pieces, (i.e. using the HighPass out of the subs to avoid the low-mid overlap) I think you'll get much more predictable results (song to song, set to set, night to night, venue to venue). I'd try to make it as flat and efficient as possible regardless of input source(s). Otherwise, I feel like you will be forever chasing your tail as every adjustment has multiple results and consequences. Matrix and Aux technology is a beautiful and useful thing, but in my opinion, only in systems and venues well up the ladder from what you've described. And I feel like it would actually be a detriment to an admitted novice mixing, at least at first. More energy in the sub and low-midrange isn't going to be of any use to you without enough high-mid and horn level to balance it out.
    • In your case, I think you can achieve the same net result as you would with the Aux or Matrix approach in a more pure way, by using the HPF on each input - with the added benefit of it being more tunable / adjustable, rather than 'all or none'. (meaning, included or excluded from the sub feed) So in other words, if you wanted a little electric guitar in the subs, set the HPF at 100Hz. If you don't want any of the acoustic guitar in the subs, set the HPF at 120Hz or above. As pcrecord points out, even the kick drum can be very present up to where the beater sound is between 3k - 5kHz. And as Boswell notes, using an EQ as a pseudo-crossover is likely to introduce unnecessary phase problems. If they're trying to milk every dB out of the system they can, a better solution would be an external active crossover along the lines of the dbx DriveRack family.
    • One way or another, I'd really want to get those top cabinets a couple feet higher. If the PA is stacked on an elevated stage, they might be OK without any pole, tripod, or box. If they're stacked at floor-level, as soon as someone 5' 6" stands or dances in front of the 6ft. tall stacks, they will block virtually all of that stack's high freqs. from getting to the rest of the room. So the people up front are going to get drilled by the horns, and for the folks further back it will sound muffled and muddy. It's a good idea to get the horns a couple feet above head level.
    • All you need to balance the levels of the sub vs. the full-range is an RTA app for your iPad. I use one by "Andrew Smith" in the App Store, that is very handy for realtime frequency analysis and easily accurate enough just using the iPad's internal mic. If you would like any more information about that, please feel free ask.

    What genre of music do they play?
    Can you can provide any details on number of vocals, and the rest of the instrumentation? (what all is mic'ed up)

    Best of luck.
     
  13. CherylJosie

    CherylJosie Active Member

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    Perceptive of you. :)

    Actually, I think time constraints and the freshness of the alliance, plus my lack of experience as well as his, have been the major obstacles. He seems receptive in the broader sense.

    Most layperson will not be aware of this so it is understandable and forgivable.

    Thanks for that elaboration. My DSP days were long ago and sparse.

    That is the plan. DL1608 has four VCAs, and also has four submixes with EQ.

    I am averse to deliberately dropping frequencies above 120Hz from bass and kick without understanding why it is OK to do so. Can you elaborate?

    Rechecking, I see that the subs have 12dB/octave (2 pole) crossover built in. I suppose I should understand if that is Linkwitz-Riley cascaded filter or Butterworth and probably Mackie is the place to find out in the absence of direct acoustic measurements.

    What institution?
     
  14. CherylJosie

    CherylJosie Active Member

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    This might be what the drummer actually implemented. I need to re-check. My lack of experience left me unprepared, in the heat of a gig with zero prior experience in master fader, to check thoroughly. I suspect the aux was all pre-fader.

    Does a VCA gang faders without merging signal paths? Controlling the mix was too complicated. If a VCA can fix that then I would use one for the bass, one for the kick, and one for the FOH (thanks for that acronym Donny). That leaves one spare.
     
  15. CherylJosie

    CherylJosie Active Member

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    Experiments are unlikely. I am probably going to have to make all these adjustments incrementally during set-up and teardown at gigs. There is geography, health issues, and time constraint.

    Maybe once I have been doing this for awhile and demonstrated more competence then the drummer might be more receptive and let me measure the system to set up the crossover.
     
  16. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    it is no just ok to remove low end on top speaker systems when you have seperate subwoofers, it is recommended.
    Here is how I understand it.
    Low frequencies are harder to produce for the amp and the speaker. It takes more electricity and energy to project them. When a full range cab is overloaded with low frequencies, it also affects the other frequencies because most speaker protections affect the full Spectrum. If we remove the low end on a speaker, the speaker will be able to project more mids and HF before overloading. So when the lowend isn't there the speaker will be able to play louder. Also, if there is no protection, there is less risks to damage the speakers. Also most full range boxes that are able to produce sub frequencies aren't as good to produce them like dedicated subs. (Their shape and the way they are made internally)
    Some will also argue that seperating the sub frequencies will help the speaker a cleaner and more precise sound.
    That's why most pro installation uses seperate subs. But this is not true of all systems some boxes are made to be stacked together with full range signals (highend array)

    All in all, you would be saving the speakers some stress and strains if you'd remove the low end and it will sound better !
    ( all good arguments for the owner)
     
  17. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    Sending him some litterature or video demonstration could help.
    If it's a stubburn person, maybe the only way is to make him believe the idea comes from him ! ;)
     
  18. CherylJosie

    CherylJosie Active Member

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    I might be appropriate to mix for other deaf musicians and bar creatures occasionally but I am not in the market to do this for pay. My top octave faded decades ago.
    Thanks. The drummer has been doing this for a while. His practical background dwarfs mine, but I have a theoretical edge.
    Already discovered that complexity the hard way. I have already suggested calibrating the system with a microphone and analyzer using a traditional crossover approach, but so far the drummer has not responded to that suggestion.
    I think they already are experiencing that limitation in some aspects because their standard mix is a little bit muddy, but not sure if it is from lack of mid/treble power capability, or if it is from inexpert EQ shooting at that Reggae tactile. I have not noticed any clipping but with my toasted ears I am the last to know plus I just started on this a couple months ago.
    The drummer likes being able to tweak everything from the iPad, plus I think maybe he does actually want to get all the bass he can out of the system.

    Now that I understand it, I am up for the challenge of a more complicated setup, if for no other reason than the education (and of course the challenge).
    The mains state explicitly that they cannot be pole-mounted despite having a socket that would mate them to the subs on a pole. I think for liability they have to follow the manufacturer's recommendation so I am not pressing the issue. Fortunately the cabs are always on a stage so far, so they have at least an additional 12" to 36" on the audience.
    Thanks for that. I will check on it. Hopefully it can find a UMIK-1 USB calibration microphone. Even if the calibration data for the mic is not there, the mic is pretty flat by itself.
    They play cover Reggae, original Reggae, and cover pop adapted to Reggae/Ska.

    The drums are mic'd with cardioid, only kick and snare but I bring my mics now so they added a hi-hat mic that they already had a channel allocated for. The kick is one of those longer small diameter things for easy transportation and smaller footprint.

    I am trying to get the drummer to mic the cymbals too but so far not pushing too hard because of the clutter and my lack of experience, plus the stage volume is loud enough that the cymbals do not need mic in most of the venues they play. Maybe later, if they bring the stage volume down a little, I will again suggest mic'ing the cymbals.

    There are 3 hypercardiod? vocal mics up front for bass lead and rhythm guitarists. These are the type that align horizontally parallel to the floor to aim the null at the monitors.

    The lead plays a beautiful pale green hollow Gretsch with a wonderful warm jazz sound but I forgot what amp he uses. I think the bass is fender jazz with two 10" Mesa and running direct out. The rhythm varies but mostly fender telecaster? maybe. Not that conversant with this, never heavily invested in equipment myself. My thing is home theater.

    The small-ish lead and rhythm cabs are set flat on the floor and direct out I think (or maybe mic'd cannot remember) but placed behind plexiglass right-angle shields to keep from splashing the audience. I think one is a Fender with a single 12" but not sure. I did not have time to pay attention to these details yet.

    I think they rely heavily on the floor monitors. They use at least two of them up front at every gig but since the drummer does not sing there is no monitor in the back as far as I know. No in-ear monitors.

    All the guitars are wireless. Everything else is wired except the iPad of course. No racks that I could see, just the usual foot pedals, some small and classic, some larger and complicated.

    They have a keyboard player running direct who barely makes a sound, hiding in the background playing rhythm.

    They also have a second, partial band rhythm/front man who joins in with his own set, with a female guest vocalist doing some originals beside him too. Mixing it up like that keeps it more interesting but it also means I have to re-adjust the vocal levels and EQ on the fly between sets and songs. Plus they are mixing down the two rhythm guitar amps on stage but they never use both simultaneously so that is manageable. I think they may have run out of channels on the DL1608. Not sure, maybe the drummer just wanted a single fader for the rhythm.

    I am hoping to put the vocals through a single submix so I can EQ them as a unit for the proximity effect and adjust their level as a unit. Same/similar for the drums. But I have a long way to go learning the ins and outs of EQ and compression for live sound.

    Plus I still have not figured out how the effects channels work, so I just twiddle until they sound about right. NOOB! NOOB! NOOB! ;)
     
  19. CherylJosie

    CherylJosie Active Member

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    I suspect that additional expenditures are off the table.

    So far, I have the following options then, beginning with modified version of the existing setup:
    1. Use aux-fed sub pre-fader on bass and kick only, filter the aux and mains separately per input channel to remove sub bass from the mains, and add VCA to the bass, kick, and FOH faders so the subs and full range track each other. Remove the lowpass in graphic from the aux/sub.
    2. Use the aux-fed sub post-fader with additional highpass on the mains to match the sub lowpass crossover, and add the VCA to the FOH faders. Add the guitars to the aux sub mix channel for the bottom 40Hz.
    3. Use the built-in subwoofer crossover and re-do the mix for a single full range output.
    Of these options, only the first would preserve full bass output capability and allow for strong 'doppler isolation' between subs and mains without the need of any crossover, but it seems like the most complicated to configure and difficult to control.

    The second seems like a simpler compromise that reduces the chance of doppler but it sacrifices some bass output capability from the full range mains.

    The third is simplest and cleanest in practical terms, but it means the system must be carefully calibrated at sound check because I cannot run up on stage and change the faders on the rear of the speakers during a performance plus it again sacrifices some bass output capability from the full range mains.

    Then there is one additional possibility in that matrix crossover doc that I cannot read until I finish the master fader manual, but unlikely to apply since it is probably even more complicated?

    I think I have my answers. Thanks people.
     
  20. dvdhawk

    dvdhawk Well-Known Member

    Joined:
    Dec 18, 2008
    Location:
    Western Pennsylvania, USA
    Sorry, a couple follow-up notes:

    • If you use the Aux Post-Fader, the kick and bass will 'track' with their FOH sliders.
    • Keyboards can go lower than a bass guitar, so you might want to put keys in the sub too.
    • I think the mid-show adjustments might be at least partly due to the unpredictable nature of the way they've been doing things. It seems like riding a bucking bronco to me. I think you'll make more people in the audience happy with a mix that's clearer and a couple dB quieter (with well balanced highs and midshipmen's), than wringing a few extra dB out of the muddy low-mid region. Happy audience = more call-backs, bigger audience next time, more fun, and better pay.

    Please let us know how your experiments go!!
     
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