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Mono Vs. Stereo? What's the real deal?

Discussion in 'Live Sound [BG]' started by armyadarkness, Sep 17, 2018.


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  1. I've always run stereo, because I thought it was the best... But I carried that mentality over from my "home stereo" way of thinking, and now I wonder if it's actually hurting me.

    My PA is 3 Crown 2500 Power Amps (mains, monitors, subs), an X32 Mixer, and DBX Driverack PA2 loudspeaker management system. The mains are Yamaha BR15 2-ways, running at 8ohms, and subs are JBL 18's running at 8ohms. I've been using this for about 4 years now.

    Here's my issue... I often have to push the vocals beyond unity gain in order to be heard, and I feel like I really shouldn't have to with all of this power. My gain structures are set well, and yes, I know that at 8ohms I'm not getting full power from the amps, but I can't believe I have to turn up so much to hear the vocals.

    I keep telling my guitar player that I want to by three way speaker cabs (2x15 with horns) so that I can drop down to 4ohms and get more speakers and power, but he insists that it won't help, and while he has no practical experience, he does have a degree in sound reinforcement.

    While grappling with this issue, I can recall the old days, when switching the home stereo to mono, it seemed much louder... So is my issue just that I'm not using mono?

    BTW... we do not pan, and the only "stereo" thing in the PA is the MP3 player.

    Thanks for your thoughts. Anyone with Driverack exp., I'm especially interested to hear your experience.
    20180420_182102.jpg
     
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  2. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Chillin' n Grillin' on the Best Coast
    Song Surgeon slow downer.
    Maybe running mono would give you more headroom.
    Also, try setting the vocal volume and then set the band mix volume below that.
     
  3. s0c9

    s0c9 Supporting Member

    Jan 9, 2014
    Ft.Worth/Dallas
    1964 Audio artist, Fractal Audio Beta Tester
    It's NOT really mono vs stereo. Power amps like yours are dual-channel not stereo.
    You can run both channels at once and each will push 440w @ 8-Ohms. The BR15 specs say 400w (Program) @ 8-Ohms.
    You're not under powering them.
    If you go mono (bridge mode) on the 2500, you can get 2400w and 1550w @ 4 and 8-Ohms respectively.
    If you daisy-chain your BR15's you'll have a 4-Ohm load and 2400w is WAY more than the 1600w peak that both speakers can handle.
    In essence, you'd be giving each speaker 1200w and they are rated at 800w peak.
    This approach maybe fine for the subs - I haven't checked the specs.

    I know you said you gain staged the rig, but are you sure you did that correctly and are getting maximum output from console to amps and beyond?

    You have a problem that occurs quit often. NOt enough rig for the gig. Unless you want to spend $1000 ea on new active (powered) 1000w+ tops to replace the BR's, as was suggested above, set vocal levels and adjust band sound accordingly.

    reference:
    Crown XLS 2500
    BR Series | Speakers | Products | Yamaha
     
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  4. DirtDog

    DirtDog

    Jun 7, 2002
    Retired
    No comment on the relative efficiency of stereo vs mono, but your cabs are rated at 98dB max SPL. Is that enough juice for your purpose? I would think drums could drown that out easily. My powered cabs are rated at 127dB max SPL, an appreciable difference over 98dB. Never had a problem getting the vox through the rest of the mix with a pair of those either with or without subs.

    Could be like @s0c9 says - not enough rig for the gig esp. if your not driving the cabs to full capacity.

    Are you eq’ing the vox to cut through the rest of the sonic space with what you have?
     
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  5. Unfortunately, the genre allows the guitar players to just be overbearing, and I can't see myself getting them to turn down furthur without causing problems... I consider myself fortunate that I'm able to get them to turn down their amps and just run through the PA. What are your thoughts on switching over to cabs with two 15s and 4 Ohms?
     
  6. Thanks for the response. those power amps are just about the most powerful but Crown makes, so unless I do switch over to Mono or reduce my ohms there's not much else I can do there. I can easily try both, but before I go buy new cabs I am curious about the mono versus the stereo. As for the EQ, now that you mention it, no I do not eq vocals at all. I've always left them flat for feedback reasons, but with the driverack there is no feedback anyway, maybe I should start to mess around with the EQ as well
     
  7. I have no problem dropping any amount of money on whatever is best... I just didn't want to do that if it was something that I can secure with settings. What about getting bigger speakers that are running at 4 Ohms like I had mentioned?
     
  8. nbsipics

    nbsipics Unstuck in Time Gold Supporting Member

    Apr 8, 2016
    Aw come on - there is a remote chance that you need to buy more gear: So, New cabs it is!
    ( and full reports, review, etc. ) hah!
     
  9. No fair... Your opinion is biased because you know I secretly want more gear!! I'd like to buy Yamaha 3 ways, and run the br15s off my Strategy as a home stereo! But seriously... and I would... should I?
     
    RobertUI likes this.
  10. I I never imagined buying powered cabs. But is that the way to go now?
     
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  11. nbsipics

    nbsipics Unstuck in Time Gold Supporting Member

    Apr 8, 2016
    That is a deep topic. Remember the old days when studio's always ran huge passive ( and a whole ton of small passive MS10 ) monitors. These days from what I see? 90%+ powered monitors. And some of the spl's being blasted in some of those studios ( not my cup of tea ) approach small stage volumes IMHO.

    What is the #1 reason I think for powered cabs? An excellent ( we assume ) matching of the amp to the cab.
    And running line-level to a cab is generally a lot easier that amp>cab cables and loads.

    Subs? I really think it makes a lot of sense these days. Look into the QSC Cardoid subs. I have asked but
    not heard anybody on this site using them - but the idea of semi-directional subs makes a lot of sense to me.

    And dude - don't you have a Mesa 8:88 packed away somewhere? With that monster feeding any decent cabs + DI to FOH, I would think that anything short of playing for the real Armageddon would be easy. But what the F do I know anyway? Stepping out to avoid further embarrassment...
     
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  12. Yes! Strategy 88 with a ph412 and a heritage SVT with 2 410s... buy my volume issue is with the vocals!
     
    Last edited: Sep 17, 2018
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  13. mobdirt

    mobdirt Guest

    Jun 14, 2017
    2 questions :)

    have you tried flipping the phase switch on the vocal mic?
    is the result the same with all vocalists? some vocalists have decent "throw" some dont
     
  14. mobdirt

    mobdirt Guest

    Jun 14, 2017
    also does your setup have a loudness maximiser of any sort?
     
    armyadarkness likes this.
  15. My voice has no presence, but since we play punk, I yell l a lot, so it works, but I'm working too hard!

    I dont mind telling for the song, I hate yelling for volume
     
    Last edited: Sep 17, 2018
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  16. I dont know, but there isn't much that an x32 doesn't have...
     
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  17. mobdirt

    mobdirt Guest

    Jun 14, 2017
    x32 huh, let me check it out :)
     
  18. mobdirt

    mobdirt Guest

    Jun 14, 2017
    which vocal mic?
    sennheisers have more presence the 835(?) especially (doesnt work with all vocals)
     
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  19. mobdirt

    mobdirt Guest

    Jun 14, 2017
    whoa
    id have to sit for a week or 2 and tune the system
    it has so much stuff, lots of experimentation needed :woot:
     
    armyadarkness likes this.
  20. DirtDog

    DirtDog

    Jun 7, 2002
    Retired
    I hear ya about not getting too wound up around new gear...in theory what you have should work in the small club scenario.

    I wonder, though, with X32, are you running any compression/limiting on the vocal channel and then compressing/limiting the mains? I know from experience that it's easy to get carried away with the channel strips on the digital boards. Same for channel EQ and GEQ. Just a thought, not a criticism.
     

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