low end rumble

toneyardpat

hey guys ,

i'm new to the forum, i just recently purchased a drpa for the house system at the club i work at. we're haveing trouble getting the dr set right . we used the set up wizard and had problems with not enough low end out of the subs. the room was pinked with the dbx mic for this appl. i went into the drpa and boosted the gain some on the low end and boosted some of the freq. between 600hz and 1.2 khz. we are now getting some low end rumble and the subs are still not kicking like they used to. could the x-over setting be wrong? here is a little info on our system:

mackiesr 244vlz pro mixer

(2) jbl sr4733x main run in passive mode
specs are
imp.- 4ohm
pwr. cap.- 1200w cont. pink noise
freq. range- 35hz to 18khz(-10db)
x-over freq.- 1.2khz

(2)jbl sr4719x subs
specs. are
imp.-4ohm
pwr. cap.-1200w
freq. range- 30hz to 300hz
x-over freq.- 80 to 100 hz

(2)crown k2 amps run in bridge mode(one to subs & one to mains)
specs are
2 ohm stereo-1250w
4ohm stereo-800w
8ohm stereo-500w
4ohm bridged mono-2500w
8ohm bridged mono-1600w
volt gain-32.88db at 1.4 volt sens.
the system is run all in mono, with both amps bridged 1 for both main and 1 for both subs. this is how it has been run for some time.

any help with the x-over setting and eq sugg. as i'm not sure the drpa through setup wizard worked correctly with this configuration.

PLEASE HELP!!

kpippen

Hello Tonyardpat,

Your X-over could use some tweaking... Set cross over like this (see below) and then perform another Auto-EQ only on one side (if speakers are separated like stereo) in fast mode... After Auto-EQ...enable the other side,...set everything from 0Hz to 80Hz to flat (0dB), and manually adjust 2kHz and above to your taste...

Subs
HP @ 45Hz, HS @ BW18dB/Oct
LP @ 125Hz, LS @ RL24dB/Oct
Gain +3 dB

Mains
HP @ 127Hz, HS @ RL24dB/Oct
LP @ Out, LS @ BS6dB/Oct
Gain 0dB

Set gain structure on noted on this page http://www.dbxpro.com/Forum/viewtopic.php?t=611&start=255...

Let me know if this works OK for you...:)

Kevin

toneyardpat

thanks Kevin, I'll let you know how it goes.

patrick

Dra

Hi guys, Are you running (2) 4 ohm sub cabs (2 ohm load) on a bridged amp only rated to 4 ohms in bridge mode? and the same for the mains? Sounds like trouble.

Kevin's recommendations may work well. Here are the recs from the 260 wizard.

Subs:
35hz BW12
96hz BW18
gain -5.5db

Mains:
96hz BW18
gain -9.5db

Good luck.

DRA

toneyardpat

hey dra,

yes , they are being run at a 2ohm load. i questioned it myself as i've only been helping them for around a month since the sound guy they had for about 10 years quit. i don't know if those specs you gave me will work since i'm using the drpa and not the dr260. if kevins specs don't work i'll give yours a try. thanks for your help.

patrick

Dra

The speakers don't care what the processor is. Have you set up the system using the wizard and selecting the SR speakers? What settings did it give you?
As a thought, maybe the sub amps are current limiting due to the load.

Anyway, good luck.

DRA

kpippen

toneyardpat wrote:

hey dra,

yes , they are being run at a 2ohm load. i questioned it myself as i've only been helping them for around a month since the sound guy they had for about 10 years quit. i don't know if those specs you gave me will work since i'm using the drpa and not the dr260. if kevins specs don't work i'll give yours a try. thanks for your help.

patrick

Hi Patrick,

Reading between the lines told me they must have been runing that way (2-ohms) for some time so I didn't pay it much attention... However,...I wouldn't high pass those subs below 45Hz because you are at 2-ohms and they probably wouldn't perform that well below 45Hz anyways...

Kevin

kpippen

Patrick,

How did it go?...

Kevin

toneyardpat

hey kevin,

i put your x-over settings into the drpa, but i haven't had a chance to really test it out. all we've had are a couple of guys with acoustic guit. and vocals. i did play some cd's through it. it sounds a lot better, but seems to be a little week in the mids. i talked to the guys at dbx and they gave me some suggestions on using the geq on the set up wizard. i'm going to repink the room, use the specs you gave me for x-over and take it from there. we don't have any bands playing until wed. so we'll see how it goes then. OH yes, you are right the amps have been run in 2 ohm bridged for a number of years. the crown tech said the k2 amps can do it with proper cooling. i'll let you know how it goes, and once again thanks for all your help.

patrick

kpippen

Hi Patrick,

You can also try crossing over at 105Hz (subs low pass) and 107Hz (mains high pass)...but I wouldn't go any lower... I did an install recently and it definately sounded better with a small gap between the crossover points...

Kevin

jakobsladderz

I'd be inclined to grab another smaller amp (say 600w/ch into 4 r) and use it for the tops, then use 1 K2 per sub. The amps will be much happier driving into their rated impedance (if they're current limiting now thats akin to clipping and the subs may blow) and the sound will be epic. Balance the power between the amps with the crossover point. you'll end up with a big grin and there will be plenty of punch.

Duncan

kpippen

Hello Duncan,

Using separate amps for the mains is certainly an improvement but it's not if you can't drive the load... You got to remember the SR4733Xs are rated at 1200 watts continuous...as well as the subs... In most cases the rule of thumb for sizing amplifiers is 2.5X the continuous rating of the load... So what were looking at here is 4-channels at 3000 watts each... There are some pretty heafty amps available these days but typically this type of system would require four amplifiers (L/R mains, L/R subs) in bridge-mono mode...

Kevin

Dra

Duncan, Kevin,
You are both correct.
Duncan's advice, I think, is budgetary. Not perfect, but sub duty is harder on an amp so IF you COULD ONLY buy 1 amp, that is where I'd put it too.
Kevin's advice is, if amps grow on trees, definately the way to go.

DRA
PS - When you find one of those trees, let me know.

kpippen

Dra wrote:

When you find one of those trees, let me know.

Hello Dra,

The K2 is 2400 watts @ 4-ohms in bridge-mono... I would click here to pick the "forbidden fruit"...

Kevin

Dra

Check your link. That was a link to the \"FREE SHIPPING\" tree. I have 62.34 mb of those growing in my C: drive. 8) :roll:

DRA

kpippen

Nope,...it's not a $Crown$ but I can proudly testify that it KICKS BUTT!...

Gadget wrote:

Fact...the BEH has a stiffer power supply than the RMX... bigger caps and heftier wiring... I have the NADY versions of these amps... made in the same factory..just using different cases.

Duncan,...see what you started!...:)

Kevin

kpippen

toneyardpat wrote:

hey kevin,

i put your x-over settings into the drpa, but i haven't had a chance to really test it out. all we've had are a couple of guys with acoustic guit. and vocals. i did play some cd's through it. it sounds a lot better, but seems to be a little week in the mids. i talked to the guys at dbx and they gave me some suggestions on using the geq on the set up wizard. i'm going to repink the room, use the specs you gave me for x-over and take it from there. we don't have any bands playing until wed so we'll see how it goes then. OH yes, you are right the amps have been run in 2 ohm bridged for a number of years. the crown tech said the k2 amps can do it with proper cooling. i'll let you know how it goes, and once again thanks for all your help.

patrick

Patrick,

How did it go?...

Kevin

jakobsladderz

like a ping-pong ball thrown into a room full of mousetraps

My experience with setting up PA systems has been primarily for use by DJ's. I guess the main difference between this and live music would be dynamic range, far more of it with live music. That aside, I have found that I get a nicely balanced sound running a 500w/ch amp into 100db/w subs and 175w/ch amp into 98db/w tops, crossed over round 112-120hz (running stereo subs to allow higher xover point.. assuming similar efficiencies that would correspond to a 850w/ch amp for the tops using 2.4kw for each sub.. that would be a very solid sound.

I understand the logic with regards to being able to use a 600w rms speaker with up to 2.4kw of amp without risking the drivers so long as clipping is avoided because of the peak ratio and dynamic range etc. Point is, there should be no problem running a smaller amp though, if you don't need the volume, so long as clipping is still avoided.. I guess it's like having a V8 engine in the car; Fun to stomp the foot every now and again, but you don't necessarily need all that power (volume in our case) all the time..

I had to turn the PA down a little at the local cafe a few mates and I play at, we were rattling bottles and glasses of the shelves. I doubt anyone's spleen would be intact if I ran a 2400 watt amp (peak power rating of the speaker) instead of the 500..

kpippen

jakobsladderz wrote:

I understand the logic with regards to being able to use a 600w rms speaker with up to 2.4kw of amp without risking the drivers so long as clipping is avoided because of the peak ratio and dynamic range etc.

Hello Duncan,

I could be wrong but I believe Patrick indicated his speakers to be rated at 1200 watts continuous each and...he's operating in a club venue... If you think about it...he's probably pushing around 4800 watts out of his K2s considering his loads are 2-ohms... So what I have suggested (power wise) is probably not that different from what he's already doing... In this particular case the main advantage of using four amps in bridge-mono at 4-ohms verses two amps at 2-ohms would be versatility I think... Personally,...I would consider a 2X4 stereo configuration in a club setting... Anyways,...it's just my opinion...and I still have a lot to learn...

Kevin

toneyardpat

hey guys,

From fri. to sat. I ran 12 bands on the system with the original specs. kevin gave me and after a little tweeking of the e.q. the system sounded great. No problems at all. To answer some of the other discussions, Yes I would rather run the system with more amps at a 4 ohm load. the problem is the club owner has used this set up for the last 8 years and is unwilling to spend money on something he cannot see the need for. Anyway Kevin and everyone else thanks for all the input.

Patrick

kpippen

Hi Patrick,

Thank you for posting back your results!... It's always good to know the outcome...:)

Cheers,

Kevin

PS. Stayed at the Holiday Inn that night...

HouseOfKlipsch

pardon if this has been discussed, but with lower impedence loads, particularly with bridged amplifiers, doesn't disortion increase?

Dra

Pardon if I'm mistaken where, but I think it was on a Crown Spec spec, that as load drops, so does the damping factor. In theory, the higher the damping the more control of the cone the amp has (particularly in the sub range). For example, for an 8 ohm load the damping may be 500, for 4 ohms - 400 and for 2 ohms - 300. (numbers pulled out of the air). Bridged or not is probably ont a factor. But, I've been wrong before. (once). If the above, and I think I have seen the distortion issue listed as well, is true, it stands to reason that the too are probably linked. (less control / more distortion).

DRA

kpippen

Pardon me... Would you have any Grey Poupon?...