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Post by total2727 on Feb 13, 2017 23:21:38 GMT -5
I have a xpa-5 gen2 and a xpa-2 gen 1 and have noticed that the xpa 2 runs much warmer than the xpa 5. I have the xpa 5 running mains, center and surrounds all 98db or better. The xpa-2 is running 2 subs at 4 ohm each. I expect it to run warmer when I am pushing things. But even at night at low volumes it still runs much warmer than the xpa-5. Never gets to hot to touch but pretty warm. ??
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Post by shortyg83 on Feb 13, 2017 23:42:42 GMT -5
Running the amp at 4 ohms compared to the 6 or 8 ohms the other amp is at is likely the reason.
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Post by macromicroman on Feb 14, 2017 9:21:14 GMT -5
Ohms measures resistance-resistant=heat.
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Post by boomzilla on Feb 14, 2017 9:38:05 GMT -5
AND the XPR-2 had a tendency to run warm to start with - even when at idle.
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Post by total2727 on Feb 14, 2017 13:54:36 GMT -5
Thanks guys, didn't think there was a problem just curious.
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jlafrenz
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Post by jlafrenz on Feb 14, 2017 15:06:52 GMT -5
98db...? That is ROCKIN'!
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Post by Deleted on Feb 14, 2017 16:21:12 GMT -5
Those products aren't exactly my area of expertise but I do know that in class-AB power amps there is something called "bias", which affects how the two phases of the amplifier (positive phase and negative phase) hand over to each other, and bias is a current level which both transistors conduct (that is, the amplifier operates in class A thru this part of the waveform), which causes them to generate heat even with no signal. As class-AB amplifiers get better, with better parts and better design, this bias setpoint can be lower; it only needs to be high enough to prevent something called "crossover distortion" near the zero crossing of the waveform. The quiescent heat output of an amp (the heat output with no signal) can be greatly reduced if the bias current can be lowered, and this also improves power efficiency.
It is possible that the first-gen XPA uses higher bias than the second-gen, although notably the Class A/AB switch on the XPA-1 Gen2 amplifier works by increasing the bias setpoint for the amplifier so that it runs in Class A to a higher power level (appropriate to the thermal dissipation capacity of the unit's heatsinks), so if you still want high-bias operation you can set that product's switch accordingly.
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Post by total2727 on Feb 14, 2017 16:39:52 GMT -5
98db...? That is ROCKIN'! I know it is like having a big block chevy driving a Prius. Effortless power to them, you know what they say about headroom. I have driven them to over 103db in room with hearing protection and the amps never break a sweat. Huge fan of horn loaded speakers, sound is not for everyone but you can drive them to insane levels with flea power.
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Post by leonski on Feb 14, 2017 17:28:38 GMT -5
If I understand this right, the XPA-5 is driving horn-loaded speakers. '98db or better' is pretty high sensitivity. You'll never put a dent in the XPA-5 even at pretty insane levels.
That being said, the crossover to the subs determines the aprox amount of power needed. At a reasonable 80hz and lower? You'll need maybe 15% of the total system power for those speakers. Of course, the subs are of an unknown sensitivity, so that matters as well. I think one of the reasons the XPA-2 runs warm is that it is well-biased into class-A. This applies to the first 10 or maybe 20 watts. The Gen2 with the needless A-A/B switch was biased even further into 'A' and probably ran warmed. That would be if they didn't increase the amount of Heat Sinks in proportion to the new demands.
If you can lay your hand on it? No problem.
I wish I could post an InfraRed photo of my amps. You can see the 'hot spot' in the power supply. And since they are moderately driven they don't get THAT warm, ever. Even into my very low sensitivity panels.
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Post by teaman on Feb 14, 2017 17:34:55 GMT -5
Total, I notice my Gen 2 XPA 2 and 5 run warmer and are more active than my Gen 1's, kind of opposite your findings. Part of that I am sure is that the Gen 1 is 32db of gain where as the Gen 2 are 29db. My LED's on the front of my XPA-2 Gen 2 lights up three lights even when I listen at night at low volume. I can turn the volume up quite a bit before I get LED's to dance on my Gen 1. My Klipsch KP-250's, Heresies are all 94db sensitive and my Infinity SM 150 and 152 are 102db sensitive. It doesn't take much to push these to high volumes but the Gen 2 definitely heat up quicker than my Gen 1 in all cases.
Tim
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Post by leonski on Feb 14, 2017 19:02:36 GMT -5
Total, I notice my Gen 2 XPA 2 and 5 run warmer and are more active than my Gen 1's, kind of opposite your findings. Part of that I am sure is that the Gen 1 is 32db of gain where as the Gen 2 are 29db. My LED's on the front of my XPA-2 Gen 2 lights up three lights even when I listen at night at low volume. I can turn the volume up quite a bit before I get LED's to dance on my Gen 1. My Klipsch KP-250's, Heresies are all 94db sensitive and my Infinity SM 150 and 152 are 102db sensitive. It doesn't take much to push these to high volumes but the Gen 2 definitely heat up quicker than my Gen 1 in all cases. Tim It's the BIAS which makes 'em run warmer. All other things being equal, I'd expect the higher bias amp to run warmer. If you look at a really high bias A-A/B amp like a Pass Labs, the XA30.5 as an example, it runs 30x2@8 in 'A'. Than it has about 6db of headroom over THAT which ends up to be 120+ a side firmly in A-B. At some point distortion becomes the limiting factor. It weighs about 60lb and is 'only' 26db gain. One tester ran the amp at 40 a side into 8 ohms for an HOUR and got it up to about 140f. That is pretty much worst-case. Do you have any way to measure the temp? Know anybody besides me with a FLIR camera?
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Post by total2727 on Feb 14, 2017 20:52:39 GMT -5
Total, I notice my Gen 2 XPA 2 and 5 run warmer and are more active than my Gen 1's, kind of opposite your findings. Part of that I am sure is that the Gen 1 is 32db of gain where as the Gen 2 are 29db. My LED's on the front of my XPA-2 Gen 2 lights up three lights even when I listen at night at low volume. I can turn the volume up quite a bit before I get LED's to dance on my Gen 1. My Klipsch KP-250's, Heresies are all 94db sensitive and my Infinity SM 150 and 152 are 102db sensitive. It doesn't take much to push these to high volumes but the Gen 2 definitely heat up quicker than my Gen 1 in all cases. Tim You are so Klipsch poor!!! Why is it we put 200 watts on these speakers and probably never use more than 20 of those watts?? Love this hobby!! Lol
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Post by teaman on Feb 14, 2017 21:34:31 GMT -5
Total, I notice my Gen 2 XPA 2 and 5 run warmer and are more active than my Gen 1's, kind of opposite your findings. Part of that I am sure is that the Gen 1 is 32db of gain where as the Gen 2 are 29db. My LED's on the front of my XPA-2 Gen 2 lights up three lights even when I listen at night at low volume. I can turn the volume up quite a bit before I get LED's to dance on my Gen 1. My Klipsch KP-250's, Heresies are all 94db sensitive and my Infinity SM 150 and 152 are 102db sensitive. It doesn't take much to push these to high volumes but the Gen 2 definitely heat up quicker than my Gen 1 in all cases. Tim You are so Klipsch poor!!! Why is it we put 200 watts on these speakers and probably never use more than 20 of those watts?? Love this hobby!! Lol Nothing like excessive headroom on command.
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Post by leonski on Feb 15, 2017 2:36:29 GMT -5
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Post by Deleted on Feb 15, 2017 10:15:21 GMT -5
You are so Klipsch poor!!! Why is it we put 200 watts on these speakers and probably never use more than 20 of those watts?? Love this hobby!! Lol Nothing like excessive headroom on command. I agree - I've always noted a sense of 'effortlessness' from speakers, even sensitive ones, fronted by monster amps. Maybe it's a matter of that extra dynamic capability. Of course the power needs to be clean and quiet if the speakers are sensitive.
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