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Request for confirmation and guidance on initial DRPA setup

Jeff S.Jeff S. Posts: 22
edited January 2010 in PA Connectivity
Hello all. First time post. This is a general request for input on my plan for gear setup and a beginning “rough-in� plan. Confirmation and/or guidance would be greatly appreciated. Here is some background and what I am trying to accomplish. Forgive the long post – you can always skim over stuff, but if you don’t get enough info, then how can you be expected to help someone or even know what they are trying to do? Here goes …

I recently joined a weekend warrior / recreational / hobbyist Classic Rock band that plays out in the local clubs and bars. They are decent enough players and singers, they have some reasonable gear IMO for this level of band (mixer, amps and speakers – both FOH and Monitors, a snake, all the needed patch cords, etc. etc.) but they know absolutely NADA about setting it all up properly, and they have a few blown-up amps and speakers to show for it.. They are all pretty cool folks with day jobs and a life, and they really want to have someone help them get straightened out and not have crappy live sound and more buggered-up gear in the future. I volunteered for the job. Among the gear they have that is a “keeper� is an older DriveRack PA.

You have probably heard this same sad story a thousand times.

I’m new to being responsible for planning / setting up / handling live sound issues for a band, but I’m not new to playing out live, electronics in general, or audio in particular. Have played guitar in bands for 15+ years (mostly a long time ago before family / kids / responsibility / …), am an EE, design and build vacuum-tube guitar amps for myself and even sell a few of them here and there. But none of this means that I know anything about live PA setup, so I have been trying to learn enough on my own to get started.

I have read the old forum, the FAQ, external links, the Read-me first, as many posts as possible and am still going on that one. I’ve taken the DRPA out of the rack and brought it home and powered it up on my kitchen table, read the manual F2B while playing with all the buttons, played with and setup presets, and got comfortable enough with the interface. Went to the Bink Audio Test CD site and burned a CD with all the files (except for the crazy square wave / DC offset speaker killer stuff) that would be OK to actually run thru the mixer and out to the amps & speakers.

I’ve had one live session between rehearsals this weekend with the hardware where I went through the DRPA setup, then Gain Structure and Limiter setup after roughing-in a starting crossover setup, then played with the x-over a bit more. This has IMO fixed the majority of existing bonehead issues their previous attempted setup in the DRPA, and it sounded a TON better through FOH, but I really want it dialed in. I am sold on the DriveRack, but it’s now time to get some expert help in order to get conformation or be straightened out on where I am so far, and then eventually “take it to the next level�. I’ll do the work, and if I have to drag out my audio sweep generators, o’scopes, my Rat Shack el’cheapo SPL meter, whatever it takes, I’m game. Actually I intend to eventually do just that. This stuff is a blast.

OK, enough introductions.

This is the FOH gear that I have to work with, leaving out vocal effects boxes on Aux Sends / Returns, anything on an Insert, etc., and no compressors are used (yet):

1ea. Behringer MX3282A mixer
1ea dbx DriveRack PA (yea!)
2ea. Yamaha S115V Full-Range speaker cabinets
2ea. Peavey SP218 Sub-woofers
1ea. Crown XS 700 Power Amp
1ea. Mackie M1400i Power Amp

I can include links to specs / manuals if needed, but I suspect the experts have seen all this stuff and already know these boxes inside and out.

Here are my ideas and thoughts / opinions on the basic hookup and “rough-in�:

1. We do not have enough power to run both sub enclosures (nor would be even need it in the rooms we play anyway), so only use ONE sub and keep the other 150lb refrigerator-sized box in the gear trailer as a spare.
2. The Crown looks to be the higher power amp, so use it in bridge mode to drive one SP218 sub – 4 Ohm load bridged.
3. Use the Mackie to drive the pair of S115V tops in stereo as Highs up on poles, one per side of the stage.
4. We are a little underpowered, but this is what we have for amps, so just be careful.
5. Set the DRPA for “Stereo tops with mono-subs� – 2x3.

The following in the DRPA is turned OFF to start: GEQ, Sub-harmonic Synth, Compressor, PEQ, Delay, and Limiter.

Crossover roughed-in as follows:

Low @ 40 Hz with a BW18, 100 Hz with a LR24, Gain = 0 dB
High @ 100 Hz with a LR24, Gain = 0 dB

My initial observations when I set the Gain Structure using pink noise (speakers unplugged of course), from going by the LEDs on the Mixer and the LEDs for Input and Output level on the DRPA, it appeared that the Lows were about 5 dB below and the Highs were 5 dB above the Input level as shown on the DRPA.

The Mixer only has LEDs above 0 dBu at +2, +4, +7, +10, then it jumps all the way up to the Red Clipping LED at +28. This is less than ideal. It is leaving out A LOT of needed detail between +10 and +28 for us to use here, but I’m pretty confident my pink levels were “way up and in the ballpark but not clipping the board�. Also, this Mixer is supposedly putting out +4 dBu levels when the 0 dBu LEDs are lit, at least that is what the manual says IIRC. Thanks Behringer :-(

Anyway, with a “smokin’ high pink level� sent from the Mixer (in reality, likely well over +14 dBu but way below +32 dBu – and hopefully below the +22 dBu IIRC usable limit on the Mixer) and with 0dB Gains in the x-over, the Red +20 dBu Input LED’s on the DRPA are out and the +15’s are dancing. But the Low LED’s are down about 5dB and the Highs are up 5dB as compared to the Input LEDs, with the High Red +20’s glowing.

The DRPA’s inputs are not clipped but the High Outs are clipping with 0 dB Gains in the x-over!

If I trust the meter ballistics on the Mixer and the DRPA, and if I want to be safe on the Highs, and level out the overall gain through the crossovers, this leads me to believe that I need to set the Crossover Gain at +5 dB for the Lows and at –5 dB for the Highs. I am concerned that this might mess with the 100Hz LR24 crossovers if I am wrong, but when I adjust the x-over Gains like this, the DRPA LED meters seem to track it just as expected, and I can crank the input attenuators on the Mains and Subs amp and not have their clip indicators go active.

After a +5 / -5 Gain setting tweak with speakers plugged in and amps up, the 100 Hz +/- 40 Hz “warble track� from the Audio Test CD sounded reasonably OK (lower volumes needed since the rehearsal space is rather small), but I did not monitor the LEDs to see what the DRPA was thinking about this adjustment. I will do this tonight during our weekly rehearsal time and report back.

If there really is an internal gain mismatch thru the DRPA x-over when both Gain settings are at 0 dB, then “fixing� it by applying the +5 / -5 adjustment should actually be OK to do without changing the equal x-over frequencies. Has anyone else seen this? Is this a known issue? I tried searching the forum; sorry if this is an easy one that I missed. I might have to get out the sine sweep generator someday and scope this out on my bench to really know what is going on – slowly swing a line level signal on both DRPA inputs from 70 Hz to 130 Hz and monitor the levels on the Low and High output jacks to really prove the answer to this one. Has anyone else done that?

Finally, with the +5 / -5 Gain setting, setting the Limiters using the “super duper� instructions with Overeasy = 4, I needed to drop the Thresholds down from +20 to +15 in order to see the clip LEDs go away, so now I have x-over gains at +5 / -5, still have 100 Hz for both freqs, and Limiter ON with Overeasy = 4 and Threshold = 15.

That’s it so far. I have not attempted an auto-EQ yet (still reading up on that one). Baby steps here.

Bottom line: Please critique anything I’ve said here and advise me where to go next. I really want to learn from the folks that know this stuff cold. I’d like to get the system setup as well as possible so I can start learning how to actually mix ;-)

Thanks to anyone still reading this post!

- Jeff S.


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    DraDra Posts: 3,777
    Remember you are setting the gain structure not the system output. There is more bandwidth in the 100hz and up and below 100hz. I believe that is what you are seeing. Try sending a 60hz tone for the lows and a 1K tone for the highs. You might even create a combo tone. The levels should be the same now, or at least a lot closer.


    More later.
    Gadget, you're up.
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    Jeff S.Jeff S. Posts: 22
    Wow, that was fast. Thank you DRA for jumping in to help me out. Anything I ask from here on out is not arguing, it is me trying to wrap my head around the world that you and others have a really good grasp of.

    Quote: “Remember you are setting the gain structure not the system output.�

    I thought I got that one. With the DRPA outputs to the amps unplugged and pink noise running into it, I was looking at the input and output LEDs on the DRPA. That IS my system at this point, and the LEDs on the DRPA was my “system output�

    I have presumed that the Gain Structure on the Mixer will eventually be set properly from channel strips thru the two Main Outputs in the future, and now I am sending “as hot and heavy of a signal without clipping the board out to the DRPA that I ever will approach in practice� so I can set the Gain Structure. The Gain in the DRPA is set in the x-over.

    Pink noise would be worse case audio program I’d ever expect my setup to be able to reproduce in practice– it has a cr@pload of energy content all throughout the spectrum – equal energy per octave in fact, and thus I accept that pink noise would be the BEST signal to use to set the Gain Structure of my system to a safe level (i.e. don’t clip the DRPA or amps before the board clips – then just make sure I never clip the board), and for system I mean “from the Input XLRs to the Output XLRs of the Driverack�. Keep stuff from blowing up first, then work to get it to sound good, then better …

    Quote: “There is more bandwidth in the 100hz and up and below 100hz. I believe that is what you are seeing.�

    Did you mean to say ““There is more bandwidth in the _100hz and up region being used by the Highs_ than there is in _the below 100hz but above 40 Hz region being used by the Lows_� ? If so, then Yes, I see that.

    Pink noise by definition is equal energy per octave. So Yes, in rough numbers, there are only about 1.5 (or less) octaves from 40 to 100 in the Lows, but there is more than 6 octaves in the Highs (100 – 200 – 400 – 800 – 1600 – 3200 – 6400 plus a smidge). More BW in the Highs and using a pink noise signal means more energy in each stereo High channel – roughly 3x more than the Lows have. I got that. But the real grabber here is “OK, what do we expect to see on the DRPA meters when we send a nominal +22 dBu level Pink Noise signal into the two inputs of the DRPA set to 2x3�? Am I being mislead looking at the meters since there is 3x more energy in the Highs vs in the Lows?

    Ballistics aside, with any audio program being ran, either I can believe the LED meters on the DRPA or I cannot. If I am to believe them, then I need to understand how they are performing, and why. Thank you for helping me.

    Quote: “Try sending a 60hz tone for the lows and a 1K tone for the highs. You might even create a combo tone. The levels should be the same now, or at least a lot closer.�

    Yes, I’m with you on that one. How about I shoot the system tonight with 70 Hz and then 200 Hz (each of these frequencies are “three sliders away� from my 100 Hz x-over frequency on the standard ISO EQ freq range and I have them on that Test Tone CD. 70 Hz is right in the middle of the Low side Band-Pass filter response, and 200 Hz seem like a reasonable spot to shoot the High side and have it compare properly to 70 Hz in the Lows (log frequency range and all).

    I’ll also do your 60 and 1k as well, but 1k is much farther away up from 100 in the Highs than 60 is down in the Lows. That might skew the results to the High side since we would be much farther away from the crossover knee up in the Highs. Anyway, I suspected I’d have to investigate this point further, as I tried to allude to this in my earlier post. Use a Sweep-able sine-wave generator and a 2ch scope and bugger the LEDs.

    But if the differing LED levels are is a result of the lower energy in the Lows as compared to the Highs, and not the “level� of the pink noise coming in as read by the Mixer LEDs or even the DRPA’s Input LEDs, and I shoot the same level Vpp sine wave at 60 Hz and again at 200 Hz and I see 60 at the same level in the Lows as I see 200 in the Highs at the output LEDs of the DRPA – as well as at the Output XLRs of the DRPA, then it seems to me that using pink noise to set the Gain Structure is a little biased. Or at the very least, the LEDs are showing me something other that the “Gain Structure� thru the DRPA.

    TIA to anyone that helps me get a handle on this one.

    - Jeff
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    GadgetGadget Posts: 4,915
    Wow and I thought I was wordy... :lol: but hey, I always say too much info is never enough... don't you just love people that use never and always... I know I do... ok so on to a few thoughts first... after reading what you wrote...

    1. The balistics of the meters on the mixer and DRPA are only decent.. NOT accurate...
    2. Pink noise can have varying crest factors... in the case of the binkster I believe the tracks have a 12db crest.
    3. Pure tones can be more accurate for this purpose (passband dependent)
    4. It's far more important to get the analog devices in a signal chain into their optimum signal to noise than any digital devices
    5. Digital clipping is BAD... VERY BAD read this NO DIGITAL CLIPPING EVER!!!!
    6. Whether you vary the amp level or the crossover level you are moving the xover point
    7. I'm not at all surprised that the subs are 10db less efficient than the tops... but then sub info takes far more power than the above 100 hz info...I generally do just that.. add gain in the sub region of the crossover...consider this...
    a. typical front loaded sub 93-98db @ 1 meter 1 watt
    b. typical lo mid 98-102db efficient 1 meter 1 watt
    c. typical horn 105-112db efficient 1 meter 1 watt
    that's a potential efficiency difference of up to 19 db difference in output levels ... given the same input.

    I think your spending too much time fretting (chuckle.. one guitar player to another) over levels that are not represented accurately enough by the meters to be taken as tacit... I guarantee you the peak levels are not accurate enough for that kind of scrutiny...

    Once you have the auto eq done you will REALLY start to see a difference in the way those speakers sound...they are VERY peaky without equalization...even if you take the mic and place it about 4 feet out aimed right at the Yamaha, or equidistant aimed at the ceiling in the position you are standing in your practice room you will have far better sounding speakers.

    Yes your under powered especially in the sub region... those subs could take double the amps peak power...Those amps are pretty much even.. because it takes 10 times the power to get twice as loud...and a couple hundred watts difference is meaningless...

    Stereo for club use is ... useless... except for stereo keys/guitar rigs and efx ...does absolutely no good to pan a vocal or guitar to one side as then the patrons on the other side can't hear them...

    Lastly... for now... do NOT depend on the limiters to save your system.... the gain structure is for that... I like a minimum of 10-12 db of headroom on the mains... so if your approaching that +10 db point on the mixer your running out of room to move...I run the same mixer.. the same amp (Mackie1400i... and I like it!)and DRPA... and until you start working with the equipment that has better meters it's best not to dwell too much on the small stuff...

    1. Keep the mixer in the best signal to noise ratio ratio you can... each channel should be PFL'd and set to maximize the signal... when you think about it... 32 channels of non optimized signal to noise can induce a WHOLE LOT of unwanted noise into the system... where as two master output channels are just that... 2 channels...far more damage can be done to the mix with the individual channels ...

    2. As long as the driverack is operating somewhere in the middle of it's range you are fine..as noise is not a problem. As specified previously do NOT clip!

    3. I know your not wanting to tote that extra cab in but know this... 2 cabs in close proximity...
    a. couple and give you 3db of additional (free) spl...
    b. they smooth out frequency response wise
    c. they go lower frequency response wise...
    d. that's why trying to keep the subs in one location (other than the omnidirectional/no comb filtering thing :roll: ) is a great plan!

    If I haven't covered all your questions forgive me.. it's a lot to cover...but were still here so fire away!
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    Jeff S.Jeff S. Posts: 22
    Thank you Gadget. That was very helpful. For now, I’ll not rely on the accuracy of the LEDs – the root cause of this behavior has my “concern meter� pegged, but I knew this was going to be a learning curve. Point taken on the crest factor in the pink noise – I had hoped the meters were capable of catching the peaks (instead of an approximation of the RMS or average or whatever it is doing). No worries, it will get sorted out. Eventually I’ll make a breakout jig, then bust out the scope and sweep the DRPA’s inputs with different signals and see what is really happening at the outputs.

    How about we table everything else for now except the basic connectivity / hookup questions I posed earlier? I’ll save the “next layer of the onion� questions for new threads as needed.

    I’m all in on setting the Gain Structure concept by the way. To get this started again, let’s presume I know how to set it throughout the system, and can recheck it at any time if I change a Gain setting in the x-over. I’ll restate the gear connectivity stuff here for convenience.

    The following is what I have to work with. Nothing is in the Inserts, and no outboard compressors are used. I’ll also presume that links to the manuals are still not needed:

    1ea. Behringer MX3282A mixer
    1ea. dbx DriveRack PA
    2ea. Yamaha S115V Full-Range cabs
    2ea. Peavey SP218 Subs
    1ea. Crown XS 700 Power Amp
    1ea. Mackie M1400i Power Amp

    First, please confirm or provide counsel on the basic hookup and “rough-in�:

    1. Set the DRPA for “Stereo tops with mono-subs� – 2x3.
    2. Use the Crown for the Lows and the Mackie for the Highs. There’s not much difference between the two in power here, the Crown has a bit more, so just it pick this way and move on.
    3. I am a little underpowered – especially for the Low, but this is all I have for amps, so I live with it for now and move on.
    4. Since I believe I am a little underpowered while driving only ONE sub with one Crown, then I’m better off trying to knock the snot out of one box rather than be _really underpowered_ with two boxes in parallel, so only run ONE sub box in 4 Ohm Bridged rather than two sub boxes in 8 Ohm stereo from the Crown.
    5. Lay the one sub box on its side in front of the stage when we can get away with that. If not, then put it off to one side under a Top. If we cannot do that, then just put it “somewhere� that is less and 1’ or more than 8’ from a wall / reflector and leave it where it “sounds OK� when walking the room.
    6. Use the Mackie to drive the pair of S115V tops in stereo as Highs up on poles a bit higher than head height on the dance floor, one per side of the stage facing parallel out and a bit in front of the stage.

    The stereo Highs are not for “soundstage panning efforts� but just to allow the one Mackie to hit both Tops, one 8 Ohm cabinet per amp channel. I might also want to experiment with some stereo FX for the vocals since I found an old Digitech TSR-24 in the band-room (… will try to get a usable main vocal process out of it – just some subtle chorus / delay to thicken the soup ;-) and maybe for a guitar drop from my rig that can do stereo if needed, but everything else is panned dead center.

    That’s it for now ;-)

    Thank you for your patience and answers so far. I have seen how much work you (and others) have invested in answering the MANY questions posted here. I’ve played a similar role on other forums (basic electronics, vacuum-tube guitar amp design, circuit debug, etc.) and I know how fatiguing it can be answering the same types of questions over and over again.

    - Jeff S.
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    GadgetGadget Posts: 4,915
    You have a TSR 24! :D:D:D Gadget likes this! (facebook reference :roll: ) I LOVE THAT PROCESOR! I really like the ... hmm I believe #3 Ultra chorus... I set up 4 efx for the mains... A Yamaha Verb, an old bucket brigade Effectron... an ... geez I don't know Alesis verb for the snare...and the TRS... That ultra chorus adds some serious depth to the vocal and makes the mix so much less "sterile".

    As for the rest... ok.. good to go. I don't care for the S115V without processing, but after the Driverack and auto eq I got usable sound... I have built a number of "usable" monitors using the guts of the S115v... but completely changing the "box" config...( I MAY even still have the plans!)(I certainly can go to the guys I built them for and reverse engineer them!)

    BTW Kinda cool that your "all in" with the MOR equipment you have and wanting to drag the most (kicking and screaming though it will be) OUT OF IT...I completely understand...Right there with you!

    You really need to do the auto eq outdoors, or minimum the "New indoor method" which is really quick and painless... some experimentation and you could make your system sound... welll... the best you can!
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    Jeff S.Jeff S. Posts: 22
    Thanks Gadget for the config confirmation. I’ll fire up a new thread for the next layer of stuff I’m interested in getting straightened out. Nothing left to answer here.

    I actually un-racked and brought that TSR-24 home with me last Tuesday in order to mess around with it. It is an earlier one; it is the -24 and not the -24S version. Almost all of the presets are “interesting�, but IMO they are unusable for what I want to do – they are just “showing off� the unit’s capabilities and that’s cool, but all of that crazy ping-pong delay or arpeggios or detune or knee-deep reverb or some other digital trick in the presets doesn’t apply to making something that the vocals can run through and just be “thickened� – or to paraphrase you, to just “… add some depth to the vocals and make the mix much less sterile …" . This circa-1993 box was probably over the heads of most casual users since EVERYTHING is adjustable – most folks probably just wanted to turn a knob and get something usable out, like on an Alesis Microverb. I have no idea how the band ended up with a cool old vintage Digitech TSR-24, but I am not complaining – I like it too.

    The factory preset that is closest to what I actually want is one that uses the unit’s “Algorithm #3� – I bet this is the same “#3� you spoke of liking too. It is “Chorus --> Delay --> Reverb� – full Stereo in-to-out. That pretty much says “ultra-chorus� to me too.

    The unit’s internal battery is probably the original one, and after 16 years, it has understandably lost the ability to keep any changes made to the user presets, so any attempts to adjust this preset have been pretty futile since the changes are lost when the power is cycled. Have located a new internal battery and will replace it this weekend to (later) see if I can “improve� on the “good� preset. For now, given the other things that need attention, the factory preset using Algorithm #3 is “close enough�. I will have some TSR-24 questions later on after I get down to that “layer of the onion� if that is OK.

    Also later, I will have the need to open up and repair some Yamaha S115V cabs – before I came on board, they blew one of their original cabs (yep, the horn – go figure), so they bought a new PAIR of the same cabs, and proceeded to blow another one up :-(

    I’ve straightened out the gain structure and got the x-over “close enough� so that now, even though it isn’t properly EQ’ed yet, the remaining two tops shouldn’t be damaged during use. I will have some Yamaha S115V parts and build questions later on after I get down to that “layer of the onion� if that is OK too.


    - Jeff S.
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    GadgetGadget Posts: 4,915
    Ya..I have 2 and they are the 'green" ones indicating that they are the dual "S" disc processors...which doubled the ability of the device... gave it much longer delay times and the ability to be a true dual stereo unit... I can either have one super memory intensive preset, or do a couple different simpler ones. I have enough other processors I bought in the EBAY heyday before they got popular and everything was FAR cheaper than now... including an old bucket delay effectron which is WAY cool...Also some Yamaha verbs and a few other cool seemingly indestructible units have weathered the storm of time and been kickin since the early 90's... One set in a bar install during the heyday of the "smokin" days...Pretty amazing...

    The weak link in those speakers is the horn driver.. 1.25" diaphragms... I beefed all mine up to the 1.75" P Audio drivers years ago. I was able to buy 2 full drivers... magnets and all for the price of one Yamaha diaphragm... and they sound better, get louder and I haven't lost one since...

    Glad things are working out for you.
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