Unofficial Mackie User Forums > DL1608/DL806/DL32R/ProDX Mixers

FAQ: Output Compression

<< < (2/2)

WK154:
When you previously mentioned Cafetorium I was afraid of what I am only too familiar with. A dual purpose room sometimes a gym or cafeteria with lots of echo and no acoustics to speak of. That in and of itself is a nightmare. Tell me otherwise.
"I was told that since this was being run as a 70V bridged mono system, I would want to run the amp at full power, and then set my gain structure through the pre-amp and channel faders. "
A quick look at the specs shows a 256 watt (without insertion loss considered) set of speakers (64 W each). and a QSC amp that is happy driving 600 W at 70V direct (transformer optional). I would say that the advise was bad. Back off the amp. If you have good dynamic material (12 to 14 db crest factor) or a sine wave (steadier signal for setup) available set your DL output at 0 (fader and signal that's ~ 6dBu) and then with earplugs bring up your amp to an acceptable level (OSHA has max requirements not to be exceeded. Your in a school not a nightclub). A SPL meter helps with this. The clip on the QSC is 22 dBu the max output of the DL is 21dBu no clipping on the amp but you will hit the Power limit and transformer core saturation long before this. As Greg pointed out remove the low end with a high pass filter and toss the Aphex and you'll have a truer sound. The spec on the speaker states 35Hz but no tolerance is given and clearly suspect. With these settings you are with lots of headroom and good S/N ratio. Remember your setting the average level not peak. 84 dB SPL is what I shoot for. Once you have the main loudness adjusted then you can play with material eq's, preamps etc. I personally think that the Aphex is nothing but a distortion on sweet young voices unless you want them sounding like the Mackie's Belch King (see DL ad). Acoustic sound treatment would help tremendously but it will be hard to convince the powers to be. Once this is accomplished you could revisit the amp setting and fine adjust. That leaves only the Mic positions and non-existent mic technique to keep you busy riding faders. As to the lone unnamed hanging speaker on a Behringer amp I would say it's probably a better setup than your ceiling speakers. Without info ? What is your DL driving? the Ceiling Spk's or the hanging speaker or both? Back in the stone age we were more concerned about Raptors than Flying threats so our hearing evolved much better in the horizontal plane than the vertical. And so horizontal speaker systems are more efficient for our ears than ceiling ones.

BlendedMix:
Hi guys...thanks for the info again.

WK...you NAILED the environment.   :o    And yes, the hung monitor with the Europower amp sounds magnificent. 

I could bore you guys to tears with all of the reasons with regard to why ceiling speakers were chosen, but I will submit this.  I took my EMX 5000 1000W Yamaha powered mixer up there with my two S115 speakers to do some testing when this whole thing got started.  It was like one big chamber of horrible in there, and it was primarily because the back wall was reflecting the sound back all around the room making it very muddy and unclear.  Bad news is...terrible place for any sort of entertainment...good news is, I know a great place for an echo chamber if I ever need one.   ;) 

Initially, we wanted to treat it acoustically and purchase a sound system.  We had some people take the room dimensions and say that we wouldn't hear any difference unless we spent $5K.  Then some said as little as $2.5 K on the back wall alone would make a huge difference, so start with that and then add more if you need it.  Then when someone actually agreed to come onsite to test it, they submitted a bid for $10K, and insisted that any less than that would potentially just be a waste of money.  So...we were left with a "who to believe" scenario, and decided to start with the sound system first, since it was SOOO bad, and we were working with a limited budget.  They sold everything from raffle tickets to $1 plastic frogs to earn that money for the PTO.  We submitted the sound results to the District with the hope that they may look at the decibel levels and ultimately decide that it needs treatment.  Just last year, they treated their all purpose gym, so we think we may get some traction there.  I digress....badly. 

As shocking as this may seem, the ceiling speakers actually seem to make the clarity of the overall sound much better.  I don't know if that is because the speakers are better with vocal frequencies and don't have much low end, or if since the sound is in the vertical plane and the tiled ceiling is doing a much better job of absorbing some of the sound.  My guess is that it's a combination of both.  Suffice it to say, no reverb is required.  :( 

On my last trip up there to mess with it, which is difficult by the way with the school hours and access, I quickly found that the distortion in the house speakers occurs when too much bass is sent to them.  I already had a HPF on the vocals up to 100 Hz, and I think ultimately I may have to put it on even the music channels, or at a minimum EQ it down significantly, so that I can maintain clarity and not tax the speakers.  Based on the info above, I will likely lower the amp output a little bit as an added measure of protection.

Question for you guys.  I am going to go work more on it early next week.  In lieu of what I have to work with, do you guys think adding a sub would help with the absence of much low end on those open backed ceiling speakers, or would it just serve to muddy things up with that much low frequency in that sound environment?  I was thinking about looking into getting a simple adapter at Radio Shack for an old Velodyne 390W subwoofer that I have that's not in use, and seeing if I could test that from the Aux 6 output just to see what happens.  What do you think? 

 
 

BlendedMix:

--- Quote from: WK154 on May 04, 2013, 07:42:39 AM ---When you previously mentioned Cafetorium I was afraid of what I am only too familiar with. A dual purpose room sometimes a gym or cafeteria with lots of echo and no acoustics to speak of. That in and of itself is a nightmare. Tell me otherwise.
"I was told that since this was being run as a 70V bridged mono system, I would want to run the amp at full power, and then set my gain structure through the pre-amp and channel faders. "
A quick look at the specs shows a 256 watt (without insertion loss considered) set of speakers (64 W each). and a QSC amp that is happy driving 600 W at 70V direct (transformer optional). I would say that the advise was bad. Back off the amp. If you have good dynamic material (12 to 14 db crest factor) or a sine wave (steadier signal for setup) available set your DL output at 0 (fader and signal that's ~ 6dBu) and then with earplugs bring up your amp to an acceptable level (OSHA has max requirements not to be exceeded. Your in a school not a nightclub). A SPL meter helps with this. The clip on the QSC is 22 dBu the max output of the DL is 21dBu no clipping on the amp but you will hit the Power limit and transformer core saturation long before this. As Greg pointed out remove the low end with a high pass filter and toss the Aphex and you'll have a truer sound. The spec on the speaker states 35Hz but no tolerance is given and clearly suspect. With these settings you are with lots of headroom and good S/N ratio. Remember your setting the average level not peak. 84 dB SPL is what I shoot for. Once you have the main loudness adjusted then you can play with material eq's, preamps etc. I personally think that the Aphex is nothing but a distortion on sweet young voices unless you want them sounding like the Mackie's Belch King (see DL ad). Acoustic sound treatment would help tremendously but it will be hard to convince the powers to be. Once this is accomplished you could revisit the amp setting and fine adjust. That leaves only the Mic positions and non-existent mic technique to keep you busy riding faders. As to the lone unnamed hanging speaker on a Behringer amp I would say it's probably a better setup than your ceiling speakers. Without info ? What is your DL driving? the Ceiling Spk's or the hanging speaker or both? Back in the stone age we were more concerned about Raptors than Flying threats so our hearing evolved much better in the horizontal plane than the vertical. And so horizontal speaker systems are more efficient for our ears than ceiling ones.

--- End quote ---

To clarify, that QSC amp is driving four sets of the 3 speaker arrays at 256W per array right?  Again, I'm a noob at this, but is it not additive?  Is that the reason for the 70V system and the speakers being wired in succession?  Apparently, electricity is not my strong suit either.   :facepalm: 

WK154:
4 speaker sets x 64 watts per set(array) = 256 watts at 70V. The spec is per set not per speaker. Could have been clearer, my bad.

BlendedMix:

--- Quote from: WK154 on May 04, 2013, 09:45:02 PM ---4 speaker sets x 64 watts per set(array) = 256 watts at 70V. The spec is per set not per speaker. Could have been clearer, my bad.

--- End quote ---

No worries...I didn't even look at what each speaker was rated, and the spec was right there in front of me. 

Navigation

[0] Message Index

[*] Previous page