Members ToHarm Posted February 4, 2010 Members Share Posted February 4, 2010 Hello, writing this on behalf of a friend what is trying to get some insight on how to setup the dipswitches on the back of his two QSC amplifiers ... First off, bit on his equipment ... top speakers are Crest Audio LH1'sand his bins are JBL MPRO MP255S ... To power the tops he uses a QSC PLX3402 and to power the bins he uses a QSC RMX2450. With this setup, what should the dipswitch settings be on each amplifier for this setup ... he runs MONO. Dipswitches on the RMX look like this ... http://www.qscaudio.com/images/hi_res/RMX2450_bk.jpg and the PLX is this ...http://media.qscaudio.com/images/hi_res/PLX3402_back_hi.jpg I think he is getting confused (as i am) on the 'clip limiter', '50Hz/30Hz', and 'Filter' switches ... how they should be setup and why ... Appreciate your continued help guys !! Link to comment Share on other sites More sharing options...
Members ToHarm Posted February 4, 2010 Author Members Share Posted February 4, 2010 Also the Nominal Impedance of his tops are 8ohms and the bins nominal impedance is 4ohms. Does that make a difference in what mode the amplifiers should be set too ... ie. Parellel, Bridged mono, etc ... Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 4, 2010 Members Share Posted February 4, 2010 Don't run anything bridge mono. WAY too much power for the tops and too low impedance as well as way too much power (as the amps begin to smoke) for the bottoms. What crossover is he using? If he is just running mono, use the parallel mono mode and follow the directions for PARALLEL mono connections. Bottoms:Mode switches - PARALLEL monoClip limiter - ONHPF - ONFrequency - 50 Tops:Same as above. Crossover: 120Hz, 24dB/octave, LR or BW alignment.(you need an outboard active crossover) Link to comment Share on other sites More sharing options...
Members ToHarm Posted February 4, 2010 Author Members Share Posted February 4, 2010 I believe he has a DBX 223. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 4, 2010 Members Share Posted February 4, 2010 Then what I gave you is good to go. Link to comment Share on other sites More sharing options...
Members ToHarm Posted February 4, 2010 Author Members Share Posted February 4, 2010 Ok, so parallel mode on both power amplifiers ... now i'm not sure what you mean by 24db/octave and LR or BW alignment ... and is lowering the crossover freq. ok for those bins ? ... on the following document it says crossover freq. is 200Hz. http://www.jblproservice.com/pdf/MPro%20Series/MP255S.pdf Thanks for all your help agedhorse !! Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 4, 2010 Members Share Posted February 4, 2010 The DBX is a 24dB/octave LR alignment crossover. The 200Hz is the maximum recommended crossover frequency. 120Hz is about right for those subs. Link to comment Share on other sites More sharing options...
Members Dukey Posted February 4, 2010 Members Share Posted February 4, 2010 If you really want to make sure just ask Bob @ QSC - as a QSC-amp owner I've noticed they're one on the best in answering their client's questions. Just my opinion though GreetzWill Link to comment Share on other sites More sharing options...
Members Unalaska Posted February 4, 2010 Members Share Posted February 4, 2010 Andy is right on with the answers here. The crossover in question is a fixed 24/db per octave crossover, perfect for this app as are many modern crossovers being made today. As you have noticed the dip switches are different between the PLX and RMX amps, it's important to pay attention to what they are. Assuming you've set them correctly: the crossover settings, try these: (based on amps/speakers being used, this is only a starting point)Input: 0dBLF output: +3dBLF/HF crossover point: 100-120hzHF output: 0dB If you are in stereo then copy those settings to both channels, otherwise ignore the second channel, it isn't used. Also make sure the crossover is in STEREO mode even if you're only using 1 side! Turn up each amp channel all the way (this is a point of heated debate amongst some member of HC, start here and reaf=d up if you feel you have insomnia). You'll notice the system is really loud, that's good. You can either back off the mixer outputs or the crossover inputs. Do not back off the EQ or amp attenuators. It's one or the other and it's makes it easy to adjust later. I prefer to back off the mixer main faders. (flame suit on) Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted February 4, 2010 CMS Author Share Posted February 4, 2010 Turn up each amp channel all the way (this is a point of heated debate amongst some member of HC, start here and reaf=d up if you feel you have insomnia). You'll notice the system is really loud, that's good. You can either back off the mixer outputs or the crossover inputs. Do not back off the EQ or amp attenuators. It's one or the other and it's makes it easy to adjust later. I prefer to back off the mixer main faders.(flame suit on) No flaming, but I'd suggest only backing off the attenuators to the point where the amps only clip (or show limiting if limiters are on) at absolute maximum performance volume. You can't get the system any louder anyway, and it'll prevent you running up against the limiters so hard they smash the signal. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 4, 2010 Members Share Posted February 4, 2010 Always set the dip switches on both channels because in parallel mode either input can be used (and/or will pass signal) and it will prevent unintended accidents down the road. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 4, 2010 Members Share Posted February 4, 2010 If you really want to make sure just ask Bob @ QSC - as a QSC-amp owner I've noticed they're one on the best in answering their client's questions. Just my opinion though Greetz Will That's another option. Bob's a good guy. I've been handling QSC products (sales/installation/service) for about 20 years and am pretty familiar with how they work too Link to comment Share on other sites More sharing options...
Members ToHarm Posted February 4, 2010 Author Members Share Posted February 4, 2010 Thanks for all the insight .... my last question is regarding the FILTER and 50Hz/30HZ dipswitches ... correct me if i'm wrong .. When the FILTER dipswitch is set to ON ... that allows you to use the 50Hz/30Hz dipswitch .. if the FILTER dipswitch is set to OFF, than the 50Hz/30Hz dipswitch is unusable ? And For the above mentioned speakers ... do you believe setting the dipswitch to the 50Hz setting for the tops and 30Hz setting for the bins is recommended, or both to 50Hz ? Thanks guys !! Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 5, 2010 Members Share Posted February 5, 2010 From what I remember about the subs, they don't go down all that low so the 50Hz position is more appropriate. I could not find the specs on those subs, the only link that looked promising would not load. The 30/50Hz is selected by the position of the switch. The side that is labeled 30Hz is the 30Hz side and the side that is labeled 50Hz is obviously the 50Hz side. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted February 5, 2010 Members Share Posted February 5, 2010 http://www.jblproservice.com/pdf/MPro%20Series/MP255S.pdf34 Hz Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 5, 2010 Members Share Posted February 5, 2010 IMO, better safer at 50Hz. My guess is the -3dB point is closer to 45Hz. The speaker is not very robust and 40Hz at the rated RMS power will be exceeding Xmax plenty. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted February 5, 2010 Members Share Posted February 5, 2010 IMO, better safer at 50Hz. My guess is the -3dB point is closer to 45Hz. The speaker is not very robust and 40Hz at the rated RMS power will be exceeding Xmax plenty.I didn't notice at first glance but is that a bandpass cab of some sort? Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 5, 2010 Members Share Posted February 5, 2010 I didn't notice at first glance but is that a bandpass cab of some sort? Yup. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted February 5, 2010 Members Share Posted February 5, 2010 Yup.I've got the impression that bandpass and horn loaded subs both drop off and unload the driver "faster" than reflex cabs below their tuning frequency - true/false/depends ? Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 5, 2010 Members Share Posted February 5, 2010 Depends. Differently. Link to comment Share on other sites More sharing options...
Members ToHarm Posted February 8, 2010 Author Members Share Posted February 8, 2010 Thanks for the help in this thread to all, your expertise helped for the gig this weekend. Only problem i found with my friends system is that those bins are just not powerful enough to get good low end. Got the tops to a good level, but just could not match it with the bins. Can you guys recommend a good bin to go with the above tops ... i recommended EV QRX 118s. Thanks. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 8, 2010 Members Share Posted February 8, 2010 Now try crossing over at 100Hz, and decrease your top gain by another 2dB . Now you should be pretty close. The subs won't be thundering, but should be adequate. Link to comment Share on other sites More sharing options...
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