In some installations I had to set the levels on the PAs to prevent a bozo from cranking them up because he wanted more volume, effectively using very little output from the driverack but that's not the way to go.
If you use a sensitive amp (like a consumer amp or a pro amp with the levels set to max) and reduce the output on the driverack, you are NOT reducing the noise caused by the D/A converter!
The right way would be to use the processor up to its full output or let's say 12dB down, and to reduce the gain on the amp or with a attenuator or a pad.
However this (as already discussed) does not alter the fact that the input led's on the dbx did not get above -30dbu, which of course tells us the DRPA was not setup correctly (by a wide margin) for whatever reason.
This is a really open and shut case of user error and no amount of wishful thinking can alter that.
I come here to learn and, on rare occasion to debate something I see is in error. I try to do that in a somewhat diplomatic manner and to let the facts speak. I do not wish to offend you, but If the truth offends you, then so be it. From the facts you presented here the dbx was not set up correctly. And if you don't consider throwing away a potential 45db of s/n ratio as user error, I'd hate to see what you do consider user error.
To be fair to you though, you were just using what equipment you had on hand. And you have stated many times that you're not presenting your impressions as the be all end all. I would be interested to know (1) if your pre-amp has XLR outputs and if so did you use them? And (2) if your pre-amp doesn't have XLR outputs, did you use the +4dbu/-10dbu sensitivity switch on the back on the unit? It's entirely possible that you did the best with what you had to worth with, but it's also entirely possible that you could have improved the s/n ratio a bit. However without an amp with gain controls, you're behind the 8 ball to start with.
It seem plausible that he could have it set up correctly and have only the lower LED lit if the preamp wasn't cranked up to 11.
Ideally you'd keep your pre-amp fixed and adjust for volume after the dbx with a multichannel volume control. However these are expensive and hard to come by.
Let's be clear though, there is a big difference in s/n ratio between a setup that lights up the -30dbu lights at high volume and one that does it at 55db. I've had my system setup both ways (before I bought the right amps for the job) and there is without a doubt a difference in sound quality.
Actually, if your amp doesn't have gain controls you can get around it by building custom XLR cables (between the dbx and power amps) with a simple voltage divider circuit to reduce the output after the dbx. I did this for a while but in the end gain controls offer more control.
Call it what you will, it is what it is - A system with a poor gain structure such that the s/n ratio off by a potential 45db or more depending on where the volume control is. Shall I email dbx's tech support and see if they think a max signal of -30dbu is acceptable?
From the dbx manual - second to last page of the appendix - link
Note that the Krell amp in JR's system does not have gain controls and as such falls into the incorrect 'input controls turned all the way up' category.One thing that is critical to system setup is maximizing gain structure. Gain structure refers to
aligning the gain of each device so that they all clip at the same point, and the noise floor of
the entire system is at its absolute minimum. Quite often PA systems are setup with the amplifier
input controls turned all the way up in the incorrect assumption that this is the only way
to get the maximum output level.
Notice too how they said, "Critical" and "maximizing gain structure" in the same sentence.
The last time I used one of these in a SR situation, I was having problems with trying to get the vocals to come through. I found myself pushing the hell out of 800 - 1400 on the desk. I asked the in house guy about the crossover frquencies he was using and he gell fully replied 200hz and 1600hz. The system consisted 2240's 2225's and 2445's. I was having doubts about the performance of his driverack and then it all became clear. I asked why he chose 1600 as a crossover point and he commented that it was the optimum for the gear he was using. He then asked what I would use and proceeded to roll around on the floor when I replied 800hz......he started rambling about feedback and blowing drivers.....oh well. each to thier own........
Many people confuse poor performance with poor setup. The driverack stuff is great when used as intended but as with most things, can sound like bum if the setup is poor.
1600hz to go from a 2225 into a 2445, not so bad'ish! 800hz to go from a 2240 into a 2225 WAY off!!!!!!
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