List of Reference Level, High Sensitivity & SPL Speakers - Page 19 - AVS Forum
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post #541 of 824 Old 12-11-2012, 10:36 AM
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Agreed. There are lots of types of distortion. Harmonic distortion, "coloration", cone breakup... heck even temporal distortion like ringing.

How we perceive that is dependent on what kind, how much, at what frequencies, etc. It's a very complex mix. It's one of the reasons I'm so fond of Floyd Toole's book; he went to actually test and determine which characteristics actually affected perceived sound and which did not.
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post #542 of 824 Old 12-11-2012, 01:10 PM
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did not Toole studied mostly linear distortion?
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post #543 of 824 Old 12-11-2012, 02:09 PM
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Originally Posted by zheka View Post

did not Toole studied mostly linear distortion?

Toole studied which variables affect subjective experience (psycho acoustics). Three of the more notable finds are that flat FR is preferred, absolute phase doesn't matter, and that off-axis performance is very important.
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post #544 of 824 Old 12-11-2012, 02:50 PM
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check this out

http://www.gedlee.com/downloads/AES06Gedlee_ll.pdf

the study found that audibility of linear distortion is increased with increase in delay AND playback level. It is possible that perceived non-linearity at higher playback levels is an artifact of human hearing rather then actual nonlinear distortion in the system.
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The combined effects of playback level and delay have strong implications to the perceived perception of nonlinear distortion. It is not possible to say, without complicated objective tests, if what is being perceived is a nonlinearity in the system or a nonlinearity in the subjective perception as described in this paper. This has profound implications to the subjective evaluation of nonlinear distortion in audio systems most particularly loudspeakers where the delay factor can be quite strong.

Time delayed resonances, nearby cabinet reflections and edge diffraction, waves in horns; all have delay times on the same order as this study. A loudspeaker that is evaluated at 70–80 dB (SPL) may have a very different perception at 90-100 dB even if it is completely linear.

A THD distortion curve will not reveal this effect, nor will a frequency response graph. A careful look at the impulse response might yield the best insight, however this has not been quantified. Methods for measuring the nonlinear effects of our subjective perception are currently under investigation. Another point is that the usefulness of a loudspeaker for audio playback can have a sound power output limit that is independent of its electrical power handling or its nonlinear distortion characteristics. Loudspeaker evaluations that take place at a fixed level, are seriously inadequate at revealing the true quality of these systems.
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post #545 of 824 Old 12-11-2012, 03:58 PM
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Quote:
Originally Posted by zheka View Post

check this out
http://www.gedlee.com/downloads/AES06Gedlee_ll.pdf
the study found that audibility of linear distortion is increased with increase in delay AND playback level. It is possible that perceived non-linearity at higher playback levels is an artifact of human hearing rather then actual nonlinear distortion in the system.

Very fascinating. I wonder how much of that is going on in our perception of hearing that we attribute to the driver?

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post #546 of 824 Old 12-11-2012, 08:04 PM
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OK guys some real reference level numbers at my LP from 13 feet away and center channel only.





















WARNING!!!!!

After running all these tests I ran a 15000 hz sine wave at 105 dBs and my amp started to smoke! This is running constant sine waves and are a brutal test so any movie peak will be lower in THD and much easier on the amp and speakers. Do not attempt above 10khz, especially after all these tests prior. I wanted to make sure I did not blow up my amp channels so I ran my test tones thru every channel and it is still working great. I will do more testing of the amp tomorrow. This is a beast of an amp THX rated 500 watts per channel into 4 ohms and stable to 2 ohms so these tests had to be brutal!
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post #547 of 824 Old 12-11-2012, 08:58 PM - Thread Starter
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Wow! So about how many watts should the amp have ben outputting at 105db?
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post #548 of 824 Old 12-11-2012, 09:13 PM
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Originally Posted by Eyleron View Post

Wow! So about how many watts should the amp have ben outputting at 105db?

I was running sine waves from 10hz on up for a long time. I bet the sensitivity dropped quite a bit at 15Khz and caused the amp to use lots of power or the impedance dropped. Let's put it this way, how well do people hear 15000 hz? Well, it was very loud and I heard it thru my theater to my rack room and all the doors were closed. The THD was also very high so it probably was THD from the piezos that caused the amp to smoke. I will check it tomorrow. Anyways, Jerrylove's loud at 200hz at 5% THD at 1 meter is interesting. I hit 105.2 dBs at 200hz 13 feet away with 0.076% THD. I think it is pretty clean. BTW at 1 meter it would have been 112 dbs with .076% THD at 200hz.
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post #549 of 824 Old 12-12-2012, 06:30 AM
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Originally Posted by MKtheater View Post

I was running sine waves from 10hz on up for a long time. I bet the sensitivity dropped quite a bit at 15Khz and caused the amp to use lots of power or the impedance dropped..
You can get in trouble real quick doing that with sine waves. You're pushing more or less constant power at every frequency, the equivalent of white noise, and that doesn't reflect what the system will normally see. We test speakers with pink noise, as that is typical of normal content, and the power spectral density of pink noise drops by 3dB with each octave increase. A swept sine at constant voltage is OK as the time duration is so small.

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post #550 of 824 Old 12-12-2012, 06:48 AM
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Originally Posted by Bill Fitzmaurice View Post

You can get in trouble real quick doing that with sine waves. You're pushing more or less constant power at every frequency, the equivalent of white noise, and that doesn't reflect what the system will normally see. We test speakers with pink noise, as that is typical of normal content, and the power spectral density of pink noise drops by 3dB with each octave increase. A swept sine at constant voltage is OK as the time duration is so small.

Well, I just learned that the hard way. I did not know something was happening until my room filled with smoke and I shut it down immediately. I was worried that I broke that channel so I ran test tones like I was calibrating and no problems. We will see when I throw some music and movies in. I get my expensive amps fixed for cheap so I am not that worried but I don't want my theater down for the 3 days it will take to get back.

BTW, how do the numbers look? Does it seem I did it right?
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post #551 of 824 Old 12-12-2012, 08:57 AM
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Originally Posted by MKtheater View Post

BTW, how do the numbers look?
They look really good. I've never tested my DR250s at that high a level, lest the neighbors show up at my door with axes and pitchforks. eek.gif

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post #552 of 824 Old 12-12-2012, 09:06 AM
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Just another reason I love my concrete bunker. My wife and kids were sleeping when I did these. I was not in the room but an adjacent with the gear.
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post #553 of 824 Old 12-12-2012, 03:09 PM
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Originally Posted by Bill Fitzmaurice View Post

They look really good. I've never tested my DR250s at that high a level, lest the neighbors show up at my door with axes and pitchforks. eek.gif

How is that possible? You've been ranting about 105db, reference level as though it was a religion. You've been pounding your chest with your massive experience as a builder of pro gear. And you've never actually tested your gear at reference level before?!? (the logic: because of neighbors, implies you've tested nothing at this level)

Worse than a consumer and 105db zealot: you're a builder who hasn't tested his designs?

Um. Wow.
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post #554 of 824 Old 12-12-2012, 03:15 PM
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Originally Posted by MKtheater View Post

Just another reason I love my concrete bunker. My wife and kids were sleeping when I did these. I was not in the room but an adjacent with the gear.

Nothing like seeing your precious gear start to smoke lol. Cant remeber which amps you are using right now? Great graphs as usual. I love my 21x13 basement HT concrete bunker too.

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post #555 of 824 Old 12-12-2012, 03:16 PM
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Originally Posted by JerryLove View Post

How is that possible? You've been ranting about 105db, reference level as though it was a religion. You've been pounding your chest with your massive experience as a builder of pro gear. And you've never actually tested your gear at reference level before?!? (the logic: because of neighbors, implies you've tested nothing at this level)
Worse than a consumer and 105db zealot: you're a builder who hasn't tested his designs?
Um. Wow.

Im sure hes tested DR-250s before at that level just not in his home setting like MK.

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post #556 of 824 Old 12-12-2012, 03:43 PM
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Im sure hes tested DR-250s before at that level just not in his home setting like MK.
A lot higher than that in live sound usage, hitting 115dB at 50 feet. But I won't subject my neighbors to those levels unless we decide to have a block party.

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post #557 of 824 Old 12-12-2012, 04:29 PM
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Originally Posted by Bill Fitzmaurice View Post

A lot higher than that in live sound usage, hitting 115dB at 50 feet. But I won't subject my neighbors to those levels unless we decide to have a block party.

Ya I bet so. 115dB at 50 feet is definitly gettin it done!! Lol major block party!

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post #558 of 824 Old 12-12-2012, 05:22 PM
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Nothing like seeing your precious gear start to smoke lol. Cant remeber which amps you are using right now? Great graphs as usual. I love my 21x13 basement HT concrete bunker too.

It was not pretty but I think I stopped it before something melted. The test tones work fine but I have not tested it with program material yet. It is an Ada MPA-500 amp.
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post #559 of 824 Old 12-12-2012, 06:37 PM
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Quote:
Originally Posted by MKtheater View Post

It was not pretty but I think I stopped it before something melted. The test tones work fine but I have not tested it with program material yet. It is an Ada MPA-500 amp.

I just happen to sell 'magic smoke' and can do you a great deal if you'd like some to refill that amp ! wink.gif

Cheers,

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post #560 of 824 Old 12-12-2012, 07:27 PM
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Originally Posted by MKtheater View Post

It was not pretty but I think I stopped it before something melted. The test tones work fine but I have not tested it with program material yet. It is an Ada MPA-500 amp.
It was probably a resistor, they can throw off a lot of smoke before giving up the ghost. You should be able to see it easily if scorched, and swap it out before it dies.

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post #561 of 824 Old 12-12-2012, 08:42 PM
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Originally Posted by Bill Fitzmaurice View Post

A lot higher than that in live sound usage, hitting 115dB at 50 feet. But I won't subject my neighbors to those levels unless we decide to have a block party.

So "Reference Level" is not a volume you actually listen in your home at.

That's really confusing given the importance placed on reference level in the posts arguing with me.
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post #562 of 824 Old 12-12-2012, 10:16 PM
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Originally Posted by MKtheater View Post

It was not pretty but I think I stopped it before something melted. The test tones work fine but I have not tested it with program material yet. It is an Ada MPA-500 amp.

Good deal. Thats right an Ada MPA-500. Helluva amp.

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post #563 of 824 Old 12-12-2012, 11:57 PM
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Yes it is, I always want to try new amps and I always come back to this beast. There are many amps with more power but not power reserves. I have been looking at the new emotiva XPR amp which boasts more power and 180k of microfarads of capacitance but my amp has slightly less power and much more reserve power, 500k microfarads of capacitance. That means it has lots of stored power for sustained material.
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post #564 of 824 Old 12-13-2012, 10:15 AM - Thread Starter
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Originally Posted by MKtheater View Post
 I have been looking at the new emotiva XPR amp which boasts more power and 180k of microfarads of capacitance but my amp has slightly less power and much more reserve power, 500k microfarads of capacitance. That means it has lots of stored power for sustained material.

What I got out of this thread: http://www.avsforum.com/t/1388399/how-many-watts-available-for-short-peak-db/0_50 and in reading an AES paper about the duration of music peaks is that some amps will provide double the RMS power for a period of time, and a lot of the time that period might be long enough, but if it was a sustained peak for like 1000ms then the amp would be clipping. Buying enough RMS power gives more assurance you can always handle the peaks. Depending on the application, that's not always feasible though, I imagine.

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post #565 of 824 Old 12-13-2012, 11:46 AM
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We are talking 600 watts vs 500 watts into 4 ohms. The Ada will provide 700 watts for 2 ohms as well and the emo is not stable at 2 ohms.
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post #566 of 824 Old 12-13-2012, 12:33 PM
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Originally Posted by MKtheater View Post

Yes it is, I always want to try new amps and I always come back to this beast. There are many amps with more power but not power reserves. I have been looking at the new emotiva XPR amp which boasts more power and 180k of microfarads of capacitance but my amp has slightly less power and much more reserve power, 500k microfarads of capacitance. That means it has lots of stored power for sustained material.

Yes that stored power really seams to benifit dynamics. Think id rather go less power with more reserve potential than vice versa. Ive been eyeing the new Emotiva XPRs as well. Good specs. I have the Emotiva XPA-3 running my LCR SHO-10s and I really like the combo.

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post #567 of 824 Old 12-13-2012, 12:37 PM
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Quote:
Originally Posted by Eyleron View Post

What I got out of this thread: http://www.avsforum.com/t/1388399/how-many-watts-available-for-short-peak-db/0_50 and in reading an AES paper about the duration of music peaks is that some amps will provide double the RMS power for a period of time, and a lot of the time that period might be long enough, but if it was a sustained peak for like 1000ms then the amp would be clipping. Buying enough RMS power gives more assurance you can always handle the peaks. Depending on the application, that's not always feasible though, I imagine.

I get your point about ample RMS power for sure. You can tell alot from an amp by how much more power it can put at at lower ohms. If one amp is say 200x2 at 8 ohms than 300x2 and 4 ohms, than another amp is 200x2 at 8 ohms than 400x2 at 4ohms, the second amp should have more reserve power. Would I be correct?

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post #568 of 824 Old 12-13-2012, 01:03 PM
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I get your point about ample RMS power for sure. You can tell alot from an amp by how much more power it can put at at lower ohms. If one amp is say 200x2 at 8 ohms than 300x2 and 4 ohms, than another amp is 200x2 at 8 ohms than 400x2 at 4ohms, the second amp should have more reserve power. Would I be correct?

The Krell KSA-150 impressed me.

150@8 ohm, 300@4ohm, 600@2ohm, 1200@1ohm.

Only time I've ever seen that linearity... though I believe they did that by under-selling 8ohm power.
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post #569 of 824 Old 12-13-2012, 01:45 PM
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Was that actually ever measured?
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post #570 of 824 Old 12-13-2012, 01:56 PM
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Originally Posted by JerryLove View Post

The Krell KSA-150 impressed me.
150@8 ohm, 300@4ohm, 600@2ohm, 1200@1ohm.
Only time I've ever seen that linearity... though I believe they did that by under-selling 8ohm power.

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Was that actually ever measured?

I wonder that too. If so great linearity for sure.

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