Crown XLS 602, pair of T48s on channel 2, paralleled?

[djengineer]

I just finished my pair of T48s, and ran the DR250s on channel 1, and the T48s on channel 2. How much am I really shortchanging these cabs? Channel 1 barely turned up 3 notches with DRs, so not worried there.

[Bruce Weldy]

I just finished my pair of T48s, and ran the DR250s on channel 1, and the T48s on channel 2. How much am I really shortchanging these cabs? Channel 1 barely turned up 3 notches with DRs, so not worried there.

If you have the 3015LFs in 'em, you are shorting them 150 watts ea. DRs with 2510s are getting plenty of power.

More importantly, you really should be adjusting the volume of your system at the board, not the amps. Crank the amps wide open, adjust your balance with the crossover and EQ, then let your board determine volume.

[djengineer]

My DCX2496 feeds Crown amp for DRs and Titans and then also to house system preamp, so not sure how to adjust volume from there. House system is about 20-6" Klipsch thingies spread throughout. My DRs fill a sound void in front of me, and T48s make bass because there's none at all. It would be hard to control volume of these 3 things separately unless I use the 2496. I guess I just use amp knobs because it's easier to reach over and raise volume as it gets busier, and turn down when a hard-hitting song makes the amp clip. Thoughts?

[SeisTres]

My DCX2496 feeds Crown amp for DRs and Titans and then also to house system preamp, so not sure how to adjust volume from there. House system is about 20-6" Klipsch thingies spread throughout. My DRs fill a sound void in front of me, and T48s make bass because there's none at all. It would be hard to control volume of these 3 things separately unless I use the 2496. I guess I just use amp knobs because it's easier to reach over and raise volume as it gets busier, and turn down when a hard-hitting song makes the amp clip. Thoughts?

You should read the yamaha mixer manual as they show the proper way to set the gain on the system. And yes, ideally, you don want your amps to run wide open and then just feed the signal they need to reach certain voltage outputs.

However, the way I usually roll is that I try to get the hottest signal from the mixer and set all my limiters/eq on the drpa based on that. Then, I set my amps approx. 3/4 on the knobs and balance the top:subs with from the amp itself. Like I said, it's not ideal, but it's extremely convenient for me. Then, when everything is set, the main volume for the system becomes the main fader on the mixer. So basically, if the mixer clips, so will the amp, if not driven past the orange l.e.d's, then the amps can just dish it out all night.

[djengineer]

How much improvement would I expect if I just used the XLS 602 for the T48s, one per channel? I don't NEED the DRs, as I guess I can work house system a little harder. I'm thinking though, that running 2 T48s on one channel like I have been so far; that the load halves, and wattage doubles...? So isn't the final wattage to each cab about the same as 1 per channel?

[Bruce Weldy]

You should read the yamaha mixer manual as they show the proper way to set the gain on the system. And yes, ideally, you don want your amps to run wide open and then just feed the signal they need to reach certain voltage outputs.

However, the way I usually roll is that I try to get the hottest signal from the mixer and set all my limiters/eq on the drpa based on that. Then, I set my amps approx. 3/4 on the knobs and balance the top:subs with from the amp itself. Like I said, it's not ideal, but it's extremely convenient for me. Then, when everything is set, the main volume for the system becomes the main fader on the mixer. So basically, if the mixer clips, so will the amp, if not driven past the orange l.e.d's, then the amps can just dish it out all night.

Sorry, but I totally disagree. Why would you want to take all of the headroom out of your system by turning down the amps? If they are all the way up, then you won't have to to take your mixer all the way to clip. You didn't say whether you set your limiters with the amps all the way up and then turn 'em down.

If you set the limiter with the amp at 3/4, then your limiter is a crap shoot as you can't ever set the volume at exactly the same place everytime - and what's to stop some numbskull from turning it up, thus blowing right past your limiter? The limiter only works if everything after that point in the chain stays stable. And the most stable place on any volume pot is all the way up.

Now, that said - if you set your limiter at full volume on the amp, then turn it down - you'll be ok with the limiter. But, you are sacrificing headroom.

As far as Yamaha's instructions.....remember, they are the guys that tell you to put your mains on top of subs - maybe they don't know everything. And I doubt seriously if they are taking into account the use of limiters.

I'm sure there are some who will disagree, but with the exception of power shading in permanent installs - I don't know of any sound professional that runs their amps anywhere but wide open.

[SeisTres]

The limiter only works if everything after that point in the chain stays stable. And the most stable place on any volume pot is all the way up.

Not if you're amps have the little indentations My amps have the little bumps on the knobs so i just set them to the same indentation every time, no need for guessing.

As far as Yamaha's instructions.....remember, they are the guys that tell you to put your mains on top of subs - maybe they don't know everything. And I doubt seriously if they are taking into account the use of limiters.

Of course they don't know everything, and why would anyone think they do, but I seriously doubt they hired a couple of high school students to write a detailed and comprehensive piece of instructional literature for their mixers in which just about everything has it's specifications written down and all the circuitry is also drawn out.

Also, the yamaha is hot enough that extra 1/4 turn on the knobs is insignificant as far as headroom is concerned since way before my yamaha clips, the amps will already be clipping, so i get a full signal with nice headroom, without noise. And sometimes +3 led will light up but for it to clip it still has to get to +20, so no, it never really clips.

And seriously, where the hell are you guys doing sound for some bozos to come and turn up the AMPS!

So in conclusion, if I had 4 itechs all being controlled with a laptop, running at least a 100 feet snake, and I had the rms and peak limiter all set at predetermined level for every possible scenario i would encounter, then yes, I'd do it differently and alot more technical. However, that also implies that I would be running commercial power shaded flying j-arrays and commercial or professionally built subs; but until that happens, my method does everything I need it to do so I'm happy.

[Sydney]

http://www.crownaudio.com/kb/entry/16/

Often the appropriate calibration signals ( see above ) are injected directly into the amp.
The setting are then "spiked" with colored tape or "whiteout" for further reference.

EDIT:
http://www.rane.com/note135.html

Syd

[Bruce Weldy]

my method does everything I need it to do so I'm happy.

Well, that certainly is the bottom line to all us - we've gotta' do what works for us. However, I see absolutely no reason for controling the mix between subs and tops or volume with the knobs on an amplifier when you have a sophiticated device such as DRPA (or equivalent) available. It will do all of that and can be saved and recalled for each venue.

I can think of no reason why it would ever be advantageous to use the volume knob on an amp. As a general statement, I would rather control distortion by sending as little input as possible (obviously enough to have good signal strength) and maximize the ouput.

As far as the manuals from Yamaha (and I own and like their gear) or anyone else - too often they are written by engineers instead of peoplewitheers.

But hey, there's more than one way to skin a cat.....I just want to make sure there is plenty of meat left when I'm done.

[Sydney]

I can think of no reason why it would ever be advantageous to use the volume knob on an amp...

Consider this a rare exception ...
A dance studio; approx 25,000 cu ft.;
very reflective ( wooden dance floor & wainscot, full length wall mirrors, drywall w some drapes );
a Crown amp with a lot of power and very efficient speakers.
All gain stages pre-Crown are 0 calibrated - but if the Crown input sensitivity was set to take that to full gain - the Master Vol slider on the mixer becomes so "touchy" that the dance instructor does not have enough slider range to finely adjust vol. for the variation that occurs in workout music of diverse level and dynamics.
Too much power for the room - so the Crown is made less sensitive.
Outdoor or "other circumstances" the input sensitivity is restored.

Syd

[djengineer]

So I take it that I should crank the knob(s) all the way up on amp, and use DCX to control volume of T48s. I wasn't sure if DCX volume has enough range to start out quiet (early in night), and all out when bar is in full swing. Whether I use paralleled on channel 2, or 1 on each channel..max amp knob will give me max amp output...?

[DrDoug018]

I can think of no reason why it would ever be advantageous to use the volume knob on an amp. As a general statement, I would rather control distortion by sending as little input as possible (obviously enough to have good signal strength) and maximize the ouput.

When we have the volume knobs on the amp set to max, there is significant noise/hiss in the system when no signal (music) is present. The DRs are so sensitive that this is quite noticeable.

If I turn the amp attenuator up (down?) - if I attenuate the amp with the knob- then the noise disappears. We still seem to have plenty of headroom.

Maybe if we had better quality amps this would not be a problem, but at least for us it seems to make sense to use the amp attenuator.

Doug

[SeisTres]

Whether I use paralleled on channel 2, or 1 on each channel..max amp knob will give me max amp output...?

Yes the channels are the same, but the reason they should not be used as volume knobs, is because an amp can deliver full power even if at 1/4 turn on the attenuators. You just need a hot enough signal, but the amp will deliver it's full power. Hence the whole "maxing them out" and "headroom" thing because with the attenuators, you can drive the amp with whatever mixer and optimize for it's best "range".

So basically if one mixer clips at +5dbv, and another clips at +20dbv, you just attenuate the amp that 5dbv but 20dbv will make the amp put out the same amount of voltage at the outputs. However, with the processors now, it's all done from those units.