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Post by williaty on May 23, 2014 11:37:03 GMT -5
How are the LEDs on the front of an XPA-1 calibrated? I'd like to have a rough way to estimate Watts output from the LED bar graph. Is about half scale 300W or is the scale non-linear?
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Post by AudioHTIT on May 23, 2014 11:40:16 GMT -5
How are the LEDs on the front of an XPA-1 calibrated? I'd like to have a rough way to estimate Watts output from the LED bar graph. Is about half scale 300W or is the scale non-linear? This has been asked often in the past without any official answer, I think someone with proper test equipment will have to measure it. |
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Post by Cogito on May 23, 2014 12:26:21 GMT -5
IMO If there isn't even at least a rough reference point, they are purely for show.
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Post by wizardofoz on May 23, 2014 12:35:38 GMT -5
I asked Lonnie in an email about 2 Ohm loads...this is what he replied me...Lonnie if you don't want this public please feel free to edit or remove accordingly (hope you still read things here...been a long time side I see you post)  . This one is difficult to answer because it can open a big can of worms but I will do my best here. The short answer is any and all of the XPA amps can drive a 2 ohm load when certain conditions are met. First off lets look at what they are driving. In your case a couple of 4 ohm subs. If the impedance curve of the subs hang right around 4 ohm or higher as you sweep through the frequencies, then the amps won't see an issue and go into protect. However, if they dip to far below their 4 ohm rating, the amp could see this as a short and go into protect, remember, you are starting out at 2 ohms here so if they dip, you could easily go below a 1 ohm rating. The next thing to consider is cooling. The lower the impedance the more current that will be flowing through the amp output stages which is going to generate more heat. So you want to be sure and take this into consideration when setting up your system. OK so now we get to output power. The amps are rated for a specific output level, granted they can do more than what they are rated, but at the cost of longevity. But as long as you don't drive the amps any harder then what they were designed to produce, you won't have an issue. That is to say, the XPA-1 can produce 1KW and as long as you stay within the 1KW rating, you can put just about any load on the amp you want. But don't rely on the meters to show you how much you are producing. First off they are time integrated. That is to say, they have a slow reaction time in comparison to the actual music being played and simply average the signal. Also, the meters are calibrated for 8 ohms. So at 2 ohms what may only look like you are driving the amps to 1/4 power in actuality you are getting full power out of them. The last thing to consider is the AC line. The XPA amps are not current limited, so when run into a low impedance, they will try to draw as much current out of the wall as needed to reproduce the signal. If the line sags to much, it will cause the secondary capacitors to over heat and shorten their life. So, what does all this mean. Well, if you have a good solid AC line, good ventilation and you don't over drive the amps. You can run just about any load you want on them and they will be just fine. Hope this helps. Lonnie |
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Post by deltadube on May 23, 2014 12:54:06 GMT -5
IMO If there isn't even at least a rough reference point, they are purely for show. I find my xpa 1 led move nicely with the volume.... Nick at emo sales... said 1/2 across is 250 watts at 8 ohm .. and only 8 ohm is measured.. |
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Post by williaty on May 23, 2014 16:38:43 GMT -5
I had noticed that they were doing something to average or sample over time as they don't perfectly track the music. So it sounds like they actually might be rather useless if they're impedance dependent since the impedance of the speaker will vary depending on frequency.
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Post by frenchyfranky on May 23, 2014 17:41:20 GMT -5
I remember I have read in another thread as per Emo staff that the XPA-1 gen 2 meter are more sensitive compared to gen 1 and react more like meters on reference amp series. I have the gen 1 and they are not very sensitive.
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Post by audiofile on May 24, 2014 0:15:28 GMT -5
XPA-1 LED Calibration and Measurements:
1. No LED - Background music
2. 1 LED - Musically engaged
3. 2 LEDs - Sonically enveloped
4. 3 LEDs - Picture rattling excess
5. 4 LEDs - Wall flexing intensity
6. 5 LEDs - Wife screaming
7. 6 LEDs - Neighborly threats abound
8. 7 LEDs - Dogs howling in angry stereo
9. 8 LEDs - Windows shattering
10. 9 LEDs - Ears bleeding
11. 10 LEDs - Sonic death punch
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Post by bitsandbytes on May 24, 2014 7:44:41 GMT -5
XPA-1 LED Calibration and Measurements: 1. No LED - Background music 2. 1 LED - Musically engaged 3. 2 LEDs - Sonically enveloped 4. 3 LEDs - Picture rattling excess 5. 4 LEDs - Wall flexing intensity 6. 5 LEDs - Wife screaming 7. 6 LEDs - Neighborly threats abound 8. 7 LEDs - Dogs howling in angry stereo 9. 8 LEDs - Windows shattering 10. 9 LEDs - Ears bleeding 11. 10 LEDs - Sonic death punch That sonic death punch sounds awesome - what a way to go!  |
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Post by novisnick on May 24, 2014 8:34:53 GMT -5
XPA-1 LED Calibration and Measurements: 1. No LED - Background music 2. 1 LED - Musically engaged 3. 2 LEDs - Sonically enveloped 4. 3 LEDs - Picture rattling excess 5. 4 LEDs - Wall flexing intensity 6. 5 LEDs - Wife screaming 7. 6 LEDs - Neighborly threats abound 8. 7 LEDs - Dogs howling in angry stereo 9. 8 LEDs - Windows shattering 10. 9 LEDs - Ears bleeding 11. 10 LEDs - Sonic death punch That sonic death punch sounds awesome - what a way to go! If this is so,,,,,,,would you please explain the XPR-1 meter ratings,,,,,,,,,,,,,he,,,,,,,,he,,,,,,,,, your milage may differ,,,,,,,,,,,,,he,,,,,,,',,he,,,,,,,,,,he,,,,,,,, |
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Post by audiofile on May 26, 2014 18:39:24 GMT -5
If this is so,,,,,,,would you please explain the XPR-1 meter ratings,,,,,,,,,,,,,he,,,,,,,,he,,,,,,,,, your milage may differ,,,,,,,,,,,,,he,,,,,,,',,he,,,,,,,,,,he,,,,,,,, Certainly... [(XPA-1 * XPR-1) / 3.141569] + [(UPA-200 * 1) / XPA-100] * 700 |
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Post by novisnick on May 26, 2014 19:25:12 GMT -5
Is there milk to go with that pie?
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Post by frogman122 on Aug 28, 2015 18:47:50 GMT -5
I used mine for 20 minutes, all lights have been off since. Look better with no lights.
How do you guys feel about the lights? Personally, Im not sure. Haven't turned them on in years, now, if they were meters, that's a completely different pickle.
Safe weekend to all
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Post by vcautokid on Aug 28, 2015 18:59:00 GMT -5
Yes the meters are calibrated for an 8 ohm load. However, if you running nominally a 4 ohm speaker, you would double the value you see since it is half of the imepedance.
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Post by leonski on Sept 1, 2016 17:22:13 GMT -5
Meters are calibrated PROBABLY to an 8 ohm resistive load. So, the worth decreases as a function of 'wackiness of load'. Highly reactive speakers will REALLY throw off the 'reading'. Speakers like my old Magnepan Panels which
are 5 ohm Nominal have little reference for these meters even though they are not very reactive. (almost resistive)
As for Calibration detail? Lonnie apparently said they are 'averaging'. This means they do not respond instantly to peaks and might 'decay' more slowly.
Fed a sine wave? I suspect a logrithmic calibration. With 12 LEDs per channel? 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048 watts. The last? +3db.
Without knowing the dynamics of the meter AND the real calibration, they are ONLY good for a 'light show' and little else. Maybe if you have had too much 'adult beverage' or some marginally legal burning material? could be fun?
If I owned the amps, I'd shut OFF the 'meter' if possible.
I JUST looked at the website pics of the amp. Backpanel has a 'left' / 'right' / 'off' switch for the 'meter'. Also a switch for the 'indicator' lamp.
And since I FORGOT it was a mono bloc? Throws my thoughts of power per lamp completely OUT THE WINDOW.
So, I'll double up on NOT KNOWING the calibration and also the idea that while 'fun' to look at, are quite worthless in point of fact. I'd switch 'em OFF and save the electricity.
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Post by audiobill on Sept 1, 2016 17:35:28 GMT -5
Why not look at the soothing glow of tubes instead of an led "light show"
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Post by leonski on Sept 1, 2016 17:54:47 GMT -5
Why not look at the soothing glow of tubes instead of an led "light show" Multi-channel / HT stuff needing 5 or 7 channels (not counting SUB) would REALLY put a dent in the Electric Bill with an All-Tube amp section. In my climate, I'd have to double up on my Air Conditioning, too, though in WINTER, a fan to move the heat around would probably be enough! The other factor is that SOME speakers are simply too bad a load for tube amps, especially with higher output impedance. The interaction can cause frequency shifts. Some speakers with a 'reputation' for being a bad load and AREN'T (like my Magnepans) are actually quite good with tubes, provided you can muster the power. And many HT speakers are INTENTIONALLY designed with poor amps in mind, as are found in MOST HT receivers and are therefore probably OK with tubes, too. |
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Post by audiobill on Sept 1, 2016 17:59:52 GMT -5
Uh, ok.....
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Post by leonski on Sept 1, 2016 21:54:24 GMT -5
All I'm saying, audiobil, is to make sure the speaker and amp are compatible. Some of the wackier speakers made by Thiel or even B&W simply are NOT a good match for tube gear. Tubes do NOT like (either) capacitive or inductive reactance. I can't remember which. Tube gear and Electrostats for example? I'm unsure.
But it is true that the advent of Cheap Watts (that awful SS stuff) had a huge impact on speaker design.
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