Assistance Needed Please

Cheeze

Good Afternoon...I've owned a Driverack PA for a couple of years now and have had fairly good success, although I had some help with the initial settings. My band plays classic rock in small to med sized clubs and we have recently switched to using powered mains with our non powered subs. I've played around with the PA a good bit and I've read the Start Here, FAQs, General Discussion, and Driverack PA forums.....and find that I still need some assistance regarding system gain setup and crossovers. I hope you can help....

First...here's the info on the amp/subs/powered mains

Sub amp - QSC 3402 (run in stereo mode)
Stereo Mode (both channels driven)4 ohms 20 Hz–20 kHz 0.05% THD 1100 Watts per channel @ 4 ohms
Noise (20 Hz–20 kHz)
Input Sensitivity @ 8 ohms 1.9 Vrms
Input Sensitivity @ 4 ohms 1.7 Vrms
Output Circuitry 2-Step Class H
Distortion (SMPTE-IM) Less than 0.01%
Distortion (typical)
20 Hz-20 kHz: 10 dB below rated power Less than 0.01% THD
1.0 kHz and below: full rated power Less than 0.01% THD
Frequency Response 20 Hz–20 kHz, ± 0.2 dB / 8 Hz–50 kHz, +0, -3 dB
Damping Factor Greater than 500
Input Impedance 6 KΩ unbalanced, 12 KΩ balanced
Input Clipping 10 Vrms (+22dB)
Gain 40x (32 dB)

Subs - JBL 418S
18\" Bass Reflex
Frequency Range -10dB 36 Hz-300 Hz
Frequency Range +-3dB 40 Hz - 300Hz
Impedance 4 Ohms
Sensitivity 101 dB SPL
Power 600 Watts (IEC Filtered Noise, 100 Hours)
Peak Power 2400 Watts

Mains - QSC HPR 122i
12\" 2-way12\" neodymium transducer with 3\" voice coil1.4\" diaphragm neodymium compression driver
Frequency Response (-3 dB) 62 Hz – 18 kHz
Frequency Range (-10 dB) 53 Hz – 22 kHz
Nominal Coverage (-6 dB) 75° conical
Maximum SPL (1 meter) 131 dB peak
Amplifier type/power 400 W LF Class H 100 W HF Class AB+B
Input Impedance 22k ohm balanced / 11k ohm unbalanced

I'd thought I would load a new 2X4 user program specifying the JBL 418s with a custom amp along with JBL MPRO 412s (similar to QSC 122i ??) with a custom amp. If this is appropriate, I would greatly appreciate your recommendations for the sub/main crossover frequency(s) and slopes? If you have what you what you feel is a better recommendation for main selection that would be appreciated.

My next questions are in regard to the gain structure. Am I correct that once I have my new user program set with the crossovers established (but with flat GEQ and limiters defeated, etc) I am ready to proceed?[/b] I know I can set the sensitivity on the sub amp (using Pink Noise) without the JBLs being plugged in. Once that is done, do I just increase gain on the mains (while protecting my ears) until the clip point is reached and back off slightly? Then do I return to the PA and proceed to GEQ, feedback, etc?

I really appreciate your help! I'm sure I'll have a couple of more questions as I try to fine tune. Cheeze

Gadget

I'd go all custom, 2X3 or 2X4, and set the HPR at 12 o'clock (1/2 way up and then set the sub amp to the level necessary for balancing the sound...If you insist on setting the amp \"sensitivity\" you'll need to see if you can get enough out of the sub xover gain to balance the sound. That should answer both questions.
G

Dra

Cheeze, be careful when using words like \"sensitivity\". Gadget took you at your word and those amps do not offer \"sensitivity\" settings, only \"input attenuation\" (volume knobs).
I would ASSUME that those QSC's have limiting and whether you balance top to bottom or bottom to top, I'd do both and see where it takes you.

You might ask Gadget (he may already have) to check the QSC setting in the PX he has.

DRA

Cheeze

Thanks for the comments! Gadget, would you send the HPR settings if you have them in your PX? Thanks. Cheeze

Gadget

As I told Dra.. it wouldn't be till later on Thursday.. The PX is an a remote location...
G

Cheeze

Thanks. Anytime you could check would be fine. I know this is real basic stuff for you guys and I really appreciate your help. Cheeze

Dra

Here is your reminder to check the recommended levels for these speakers (mine and Cheezes) in your PX.

Thanks,
DRA


Yorkville NX55P
QSC HPR 122i

Gadget

Roger.. Thanx for the reminder...later..
G

Cheeze

Thanks Dra. Appreciate the help Gaget.

Cheeze

Whoops GADGET!

Gadget

All right guys...here it is.. although I have to tell you it LOOKS retarded :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :? :?
First off...The QSC HPR122i.....here it comes...8 o'clock, or 17% :shock:
and then there is the NX55p...at a whopping 7 o'clock..or 15% :shock: :shock:
Well, there you have it... right off the machine...let me know ok?
G... spot

Dra

What? :shock: :shock:
Did you install it up side down in the rack and it just looked like 7, when it was actually 1 o'clock and you were dislexic and saw 15% as 51%.
Kind'a makes you wonder who DBX is paying to research that stuff.

Thanks for trying,
DRA

Cheeze

Gadget, Dra...Thanks! I'll be setting the system up tomorrow and will try the setting at 8 o'clock.

Gadget

DEAD serious... and no.. I \"AM\" older than dirt... and I \"AM\" blind as a bat...but I used a microscope and a magnifying glass and somehow managed to get the unit in right side up.. and DID manage to get the system sounding AMAZING... as always... but it did take a fair amount of effort, but well worth it in the end...

That aside... I guess I would TRY it.. I would ASSUME that the Driverack would need to be @ unity gain on the xover points...and the rest of the gain structure optimized..(mixer)...

Keep me informed..
G

Cheeze

Gadget - Thanks again for the help! I'm older than dirt too....What I came up with....hope I'm doing things correctly.....Set the mixer input channel and mains at unity and unlugged all speakers. Made sure Driverack EQ, limiters, etc were off and ran pink noise to the QSC 3402 sub amp and found the clip point, then backed off slightly below clipping (approx 3 o'clock). I then hooked up the QSC powered speakers and ran pink noise to them and gradualy turned up the gain to clipping (approx -6 to-7 dB), backed off to -8dB (approx 1 o'clock). Plugged the subs in and played around with the GEQ(most freqs lowered to some degree) and feedback controls (haven't set the PEQs and limiter yet...not quite sure how those settings are supposed to work). Overall the system sound very, very good. Although I've been playing and tinkering around with sound systems for over 40 years, my ears are having a tough time perceiving a change when I sweep the High delay from 5.0 to 10.0 ms...I'll keep trying. I'm sure I'll have more questions....if you ever leave the northlands and wind up close to Myrtle Beach, SC, email me. Thanks again.

Gadget

I was in the Coast Guard at Elizabeth City for a year or sio.. I then patrolled the east coast for 5 years...and R.O.N. ed all over the coast...during my tenure...We used to weekend @ Myrtle beach lots during the summer. I don't know why in the world MOST EQ faders would be cut :?: that makes no sense... what bands? I'm also not sure how you balanced the subs and the tops.. it's not intuitive to me what you used to balance the subs and the tops.
G