Rivernuggets Posted October 9, 2011 Share Posted October 9, 2011 There is one semi-local to me for $500. Is that a good deal? Been wanting to power the LFs on my RF-7s seperately. Thanks for your valued opinions! Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 9, 2011 Share Posted October 9, 2011 PLXII 2502 for $ 500 is a decent deal, IMO. Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 9, 2011 Author Share Posted October 9, 2011 Thanks Michael. It's decent compared to Ebay's completed listings, but I just wanted to make sure. Follow up question.....as long as I mind the volume, 425watts x 2 @ 8ohms isn't crazy for RF-7s is it? Quote Link to comment Share on other sites More sharing options...
psg Posted October 9, 2011 Share Posted October 9, 2011 Nah. The best part is 1250W into 2 ohms. It will handle the low impedence dip of the RF7 quite well! Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 9, 2011 Author Share Posted October 9, 2011 Cool. Thanks guys. Hopefully this sale will go on. Waiting to hear back from him. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 10, 2011 Share Posted October 10, 2011 I have clipped a QSC PLXII 3102 @ 550 wpc into RF-3IIs and I would say that would be about the limit for them after breaking a few woofers and tweeters. ( ** long term flexing caused the cone breakage, and too much average power cooked the tweeters ) This was with a highpass on the woofers to limit excursion, so it wasn't from the surround stretching tight The average power going to the speaker was 5w or so, with the peaks just lighting up the clip lights. ( 20 db + transients ) Some of the music I have has 30 db transients, with a 425 watt amp, the highest average level you could listen to without clipping the output of the amp ( assuming proper gain structure ) is ( 425 ) - 30db = 0.425 watts. It's like having a powerful vehicle, when you want to pass, it's no trouble at all, just breathe on the pedal. Keep in mind that you have larger drivers in the RF7's, but I would be wary of cranking it up, until you have verified that your gain structure is right, and you feel comfortable running it at a high level. FWIW, I would recommend the 2502 for most people with RF3 / RF5 / RF82's, and the 3102 for RF7 / RF83 etc. Quote Link to comment Share on other sites More sharing options...
psg Posted October 10, 2011 Share Posted October 10, 2011 QSC PLXII 3102 current comsumpsion at Full Power: 8 ohms 21A/120V 4 ohms 33A / 120V 2 ohms 55A / 120V Yikes. I couldn't even fed it properly, Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 10, 2011 Share Posted October 10, 2011 The 1/8th power draw figures are more near 'normal' music signals, the 'full power' figures above would be a full tilt sinewave test tone @ clipping. You can run it on a normal 15A line, as the average draw would be no where near the current limits of the circuit. Quote Link to comment Share on other sites More sharing options...
psg Posted October 10, 2011 Share Posted October 10, 2011 Doesn't that argue that a 2502 should be sufficient? Its full-power 8-ohms current draw is 15.5 amps and the low impedence dip of the RF-7 could puill up to 30 amps. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 10, 2011 Share Posted October 10, 2011 Yes and no, a switch mode power supply amplifer draws power from the wall socket in a much different way than a conventional amplifier. The PSU in the PLX/PLXII switches at a reported 230khz, in a conventional amplifier, it's 60 hz. Also, the PLXII 2502 and up amps are class H ( two sets of power rails, a low power rail set and a high power rail set ) In other words, for short duration bursts, the PLX can put out a heck of a lot more than it's rated to do. Burst test here: http://www.diyaudio.com/forums/class-d/115300-qsc-pl380-amp-9.html Post # 89 has a breakdown. The testing was 50 msec on, 50 msec off, and the voltages were calculated into wattage into the resistive load. The PLX series was discontinued, the amp was given a facelift, and a generic crossover added to it, and called the PLXII. The 3402 is now the 3602, same as the 3002 is now the 3102. There were a bunch of amplifiers tested with the same methodology, with the results posted on the AVS forum. http://www.avsforum.com/avs-vb/showthread.php?t=855865 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 11, 2011 Share Posted October 11, 2011 I've got all my PLX2's plugged int a Furman with a TON of capacitance. Never have any problems. Quote Link to comment Share on other sites More sharing options...
psg Posted October 11, 2011 Share Posted October 11, 2011 Interesting! Nice amps! Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 11, 2011 Author Share Posted October 11, 2011 They do seem very sweet. I've read about these amps here often and am ready to experience. Michael, I'm straying from your ideal matching of amps to speakers. But I think this will have plenty of juice and headroom for the levels I listen at, around 85 db (when I'm alone in the house!). Thanks for your advice about matching the gain before enjoying. We're going to meet this Saturday morning for the transaction. Gotta find some RCA to XLR cables at Monoprice. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 11, 2011 Share Posted October 11, 2011 Gotta find some RCA to XLR cables at Monoprice. Be looking for a nice quiet 24v fan while you're at it. Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 12, 2011 Author Share Posted October 12, 2011 Oh yeah that's right. Thanks Carl. Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 12, 2011 Author Share Posted October 12, 2011 This should do it. Cheaper than I thought it would be, ~$10. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 12, 2011 Share Posted October 12, 2011 21 dB should be much quieter than stock. I can't see from the pic if it's a 2 or 3 wire fan. If it's a 3 wire, just use the red and black wires, disregard the third wire (normally white). Quote Link to comment Share on other sites More sharing options...
Rivernuggets Posted October 25, 2011 Author Share Posted October 25, 2011 Installed the new fan last week - MUCH quieter. Got RCA to XLR cables from Monoprice yesterday. Hooked the QSC to an HK 3390 and I can only get faint music with the QSC gain maxed and the receiver volume very high. I have seperates for HT....this isn't complicated but maybe I'm missing something. The QSC is used but in wonderful condition. Seller even had the original box. I'm hunting around online seeing if I need more gain from the preamp section or not. I see there are 'line drivers' you can get to boost the signal but I'd rather avoid that if possible. Here are the cables from Monoprice. Are those the problem? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 25, 2011 Share Posted October 25, 2011 The cables shouldn't be a problem. You may have a slight mis-match in the voltage the amp wants to see (input level) vs the voltage the receiver puts out. I've never had an issue, but occasionally it pops up. I've used Behringer, QSC and Crown with no problems hooking to consumer level products. Let me do some digging. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted October 25, 2011 Share Posted October 25, 2011 Make sure your clip limiter is off and input configuration is on stereo. Quote Link to comment Share on other sites More sharing options...
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