Members Damien Quinn Posted March 17, 2017 Members Share Posted March 17, 2017 Hi folksI an using 2 Qsc hpri122s active speakers and every night after a gig when i take them down that one is noticeably hotter than the other when i touch the heatsink onthe backShould this b a matter of concern. Link to comment Share on other sites More sharing options...
Members DeepEnd Posted March 18, 2017 Members Share Posted March 18, 2017 If you're running both with adequate ventilation and at the same level then there could be something wrong. The HPRI122S is equipped with a 100 Hz high pass filter to keep extra low tones out. If the filter is disabled on one speaker it could be working harder amplifying those lower tones than the other. Run a vacuum cleaner over the ventilation openings. Dust and heat are enemies of electronic gear. Check the obvious and post again. If the problem persists I'd take it in and have a tech look at it. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted March 18, 2017 Members Share Posted March 18, 2017 If its hotter its drawing more current. I'd make sure you're driving both speakers equally. If you're pushing one harder because the signal is stronger to one, its obviously going to work harder and create more heat. I would check to see if the one running cooler has the bass roll off turned on and the one running hot has it turned off. This would make the one running hot work harder because its pushing more bass. Bass frequencies are what draw the most current and create the most heat. Likewise, if you're running a stereo mixer and have something panned to that speaker, it can be working it harder then it should. You may have a situation where the one is under an air vent in the place and the other has no air movement. You'll have to use some detective work to at least rule out the obvious. Heat sinks do get hot - that's what they're there for to dissipate heat and cool the power transistors so they don't fry.The question come down to what's normal and what isn't. I'd try these things first to make sure your worries are well founded or not. First I'd do a static test with no signal feeding them. Plug them both in side by side for an hour with no signal, simply running and either do a test feeling them or you could use an actual thermometer or temperature probe for a volt ohm meter. They make those electronic thermometers, laser type, whatever you got that might work. Hands can detect a difference but you're guessing on just how much of a difference there might be. You want to get some documented facts to work with. If I were to wager money I'd suspect the two would be fairly even in temp just running idle. The transistors have to be working to generate heat. If there is a big temp difference then I'd be more worried. There's something loading the transistors down drawing more current and they would need to be checked by an expert tech with a schematic in hand who can check all the voltages and currents. Transistors can break down and loose their tolerances before they actually blow. Better circuits self adjust voltages to some extent. Many amps use variable heat resistors mounted to heat sinks to vary current as amps get hot to prevent component damage. Sometimes the components aren't securely mounted to the heat sink and they don't get as hot as they should so the amp winds up running hotter then it should. These components can also weaken or fail when an amp is pushed to extremes on a regular basis. Second, you could do an active test. Download a frequency generator application to a computer or sound card which will generate test tones. You can feed the speakers directly from the computers sound card line out. You need a stereo 1/8 cable to plug into the line out of the sound card or laptop and have 1/4 or XLR adaptors to plug into the cabs. You can download a program called RAL - real time audio analyzer. Its got a built in audio generator and will run with a windows sound card. Set the audio analyzer to a low frequency of 100hz or less and crank the gain up to a medium level. The heat sinks should heat up fairly quickly and you can do your tests again. If one does overheat - then how much hotter it gets is important. Post your results here so we can check them. If its a difference of 10% I probably wouldn't bet to worried. that may be well within the manufacturers tolerances. if its off by allot more I'd contact the manufacturer. If you aren't getting much of a temp difference and only have the problem live, there one last test. Half way through your show, check the temps, if ones hotter, swap the cables around and see if the problem moves to the other cab. If one cable is more conductive (a very common problem) one speaker will see a stronger signal and obviously work harder. You may not hear a difference because it involves frequency responses. A quality cable provides a wider frequency response which means better bass response. Cheap cables can have more capacitance so you have less highs and lows and therefore the speaker doesn't work as hard. The two cables may have similar midrange response and vocals are mostly upper midrange so you might not hear the extra bass pushing to one of the cabs. You want to be sure the two cables are equal length and if you're using a snake you want to do continuity and signal strength tests to be sure your signals are balanced. Many mixers and amps use active circuits to provide a balanced XLR connectivity. In the old days they used 600 ohm transformers at both ends to step the voltage up and current down for transmission. The transformers are expensive and active circuits are inexpensive. Long cable runs and cable quality can load the signals down and cause higher losses so what gets to the speakers may have higher losses when using unmatched cables. If you were to open the mixer and look at the insider of the XLR output jacks and see if there's only two wires a hot and ground going to the board you'd know you have an active impedance matching. If the XLR connects three wires to a transformer then you know you have 600 ohm passive. Both can work well of course depending on many factors which I'll skip over for now. My main point is most new mixers and amps use active instead of passive because of the cost so the mic cables connecting them is very important. If you have a two different cables of different quality and length, it can be the cause of the imbalance feeding the speakers which is causing one to heat up more. Good XLR are very inexpensive. If you are using two unmatched cables I suggest you buy a matching set. Monoprice sells some high quality cables at very low costs. They have 150' XLR's for $45 each which are reasonable for that length. https://www.monoprice.com/product?p_id=601340 If you need something shorter, parts express has all lengths. https://www.parts-express.com/cat/microphone-cables/670 You can probably get a temperature probe and an inexpensive DB meter for checking the actual loudness of both cabs, this way you know one cab isn't running louder then the other. https://www.parts-express.com/cat/microphone-cables/670 Link to comment Share on other sites More sharing options...
Members Damien Quinn Posted March 18, 2017 Author Members Share Posted March 18, 2017 Both speakers are running with the high pass filter switched off.My set up is using a T1 Bose tonematch with only one lead coming out of the master to one speaker and then linking the over to the other speaker with a lead. I have always used good leads with neutrik connectors.Its not a massive difference in the temperature but enough for me to regularly notice after every gig when i am lifting the speaker off the stands. Link to comment Share on other sites More sharing options...
Members onelife Posted March 18, 2017 Members Share Posted March 18, 2017 Have you swapped the speakers - with everything else being the same - to determine if the speaker itself or the signal feeding it is the problem ? Link to comment Share on other sites More sharing options...
Moderators daddymack Posted March 18, 2017 Moderators Share Posted March 18, 2017 is it the first speaker or second speaker in the chain? Link to comment Share on other sites More sharing options...
Members DeepEnd Posted March 18, 2017 Members Share Posted March 18, 2017 It also occurs to me that it may simply be a matter of time. Do you take one speaker down then the other? Is it always in the same order? It may simply be that the second speaker has extra time for heat to dissipate. Have you checked both speakers immediately after a gig? The static test WRGKMC mentioned is also a good idea. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted March 19, 2017 Members Share Posted March 19, 2017 Is it the first speaker that's plugged in that's getting hotter? If so it has a shorter lead then the second so the signal strength may be a little stronger, which drives that can harder. The second has a longer cable length so it hay have slightly less bass response and doesn't get as hot. Next time, if you know which one gets hot, swap the two around and see if its the cabs or whether its just the shorter cable run to the first that's causing it to see a stronger signal and get hotter then the second. Link to comment Share on other sites More sharing options...
Moderators daddymack Posted March 19, 2017 Moderators Share Posted March 19, 2017 ah, exactly where I was leading to in post #5... Link to comment Share on other sites More sharing options...
Members onelife Posted March 21, 2017 Members Share Posted March 21, 2017 The amount of current flowing through the signal wire is so low that the different between the lengths of the wire would have to be monumental to have a significant impact on signal strength. Link to comment Share on other sites More sharing options...
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