Class D amplification can sound just as good as true A/B

[envisionelec]

Originally Posted by jgustin

Is that the problem with the Eclipse XA4000?

I was going to write a big technical response, but I've decided a simple "Yep." is enough. It gets complex very fast. The feedback/filter mechanism is the biggest contributor to its issues with load variance. I think if you ran an active system with tweeters that had a relatively flat impedance profile, you'd never hear that harshness. But I still think you're clipping - and depending on how the clip indicator is designed, it probably isn't responding well to clipping in the upper midrange/treble.

You can clip an amplifier below the 100% mark on your headunit if the source material is above your reference level when you set the system up.

[jgustin]

I really thought I was leaving enough head room so that I would NEVER clip. I set it up so that it BARELY clipped at 100%. I don't see how it would be clipping at 80%, running components with passive crossovers. I use the loudest/best recordings I have when I set it up to account for source levels.

[jgustin]

Originally Posted by envisionelec

Wrong thread.

This isn't about recommendations - it's about the perceived differences between the JL Audio HD amps and a typically well-regarded A/B amplifier.

Look, I'm not being a dick about this. Maybe I should have asked some questions, but your post basically stated "Oh yeah, those Class D amps are harsh - I can hear it with all different types of speakers". So my reply, being one-sided and judgmental really shouldn't be taken offensively because it's the same tack you used. Try a different approach like "I have a XXX amplifier and hear harshness on X and Y music, but not Z. Are the XXX brand amplifier the same technology?"

I do apologize for offending anyone. I just re-read my original post and I can see how it could be offensive. I really did not mean it that way - lesson learned to be more sensitive while I type.

[envisionelec]

Originally Posted by jgustin

I really thought I was leaving enough head room so that I would NEVER clip. I set it up so that it BARELY clipped at 100%. I don't see how it would be clipping at 80%, running components with passive crossovers. I use the loudest/best recordings I have when I set it up to account for source levels.

But that's not how you set up a system. You can't generally hear the onset of clipping on normal source material, so you have to run the amp into a dummy load (resistor) and play a 0dB signal while monitoring the speaker output on an oscilloscope or HD meter. Turn the headunit up until it clips (amp gain all the way down), then turn the amp gain up until it clips. Ideally you want all sources and amps to clip at the same point.

Keep in mind, though, that most source material will sound "too quiet" on a system that is ideally set up - even at max headunit volume. So this is why you have to be cognizant of what clipping sounds like on your system without attributing non-linearities to a particular class of amplifier.

[envisionelec]

Originally Posted by jgustin

I do apologize for offending anyone. I just re-read my original post and I can see how it could be offensive. I really did not mean it that way - lesson learned to be more sensitive while I type.

You didn't offend me. No worries, mate!

Double post? Yep...not sure how.

[envisionelec]

Originally Posted by jgustin

I do apologize for offending anyone. I just re-read my original post and I can see how it could be offensive. I really did not mean it that way - lesson learned to be more sensitive while I type.

You didn't offend me. No worries, mate!

[jgustin]

Originally Posted by envisionelec

Look, I'm not being a dick about this.

Originally Posted by envisionelec

You didn't offend me. No worries, mate!

Okay good!
But, I might offend you now...
I just have to say, you were being kind of a dick earlier.
I appreciate your knowledge, now that I have asked for it. But, as for earlier, maybe you can take some of your own advice on how to phrase things better

[jgustin]

Originally Posted by envisionelec

But that's not how you set up a system.

Well, that's what I get for trusting a bunch of guys from DIYMA!

Originally Posted by envisionelec

Keep in mind, though, that most source material will sound "too quiet" on a system that is ideally set up - even at max headunit volume.

I'm sorry, but I don't follow this at all. Can you please explain it more?

[t3sn4f2]

Originally Posted by jgustin

Well, that's what I get for trusting a bunch of guys from DIYMA!

The same bunches that talk down on quality cheap cables, ipods, 25% cld dampening, not using linedrivers for SQ, etc.? You're following the wrong crowd, need to start looking for that science thing.

[jgustin]

It's so hard to know who to listen to. I am fairly intelligent, and I read and read, falling asleep at my desk most nights. I never trust something the first time I read it. I make sure I verify it from multiple sources. So many people sound like they know what they are talking about, and sometimes it even makes sense

[jgustin]

Originally Posted by garysummers

I was originally running the first generation Alpine PDX amps in my 5.1 setup! When the new PDX came out I decided to replace all 5 amps at once!
With out question these amps sonically out preformed the original.
So IMHO the technology is improving!

Gary,
What was the time period between the older and the new amps?

[envisionelec]

Originally Posted by jgustin

It's so hard to know who to listen to. I am fairly intelligent, and I read and read, falling asleep at my desk most nights. I never trust something the first time I read it. I make sure I verify it from multiple sources. So many people sound like they know what they are talking about, and sometimes it even makes sense

Well, if you look through my posts, you'll see that I don't get into fights about amplifiers based on anything but scientific principles. When people ask me which amp to buy, I say stuff like "Get the one that color-matches your installation" and "Buy as much power as you can afford, not based on your speaker's rated power handling (which is almost meaningless)."

What I am saying about playing "normal source material" is that you'll likely find your system doesn't get "loud enough" when playing normal music if you've set your system to clip at 0dB. Most well-recorded music doesn't peak at 0dB, so that can be misleading. Maybe set your max levels at -10dB source and make that your limit.

If you want to find out if you are clipping when you hear that harshness, grab a storage oscilloscope and look at the output during that passage (and level) that you hear it. To find the upper limit, crank the gain up until the waveform amplitude stops increasing and the tops of the waveforms are chopped off. Make note of that level...Set the capture levels to grab anything over 90% of that peak voltage and see what you get.

The amp could be faulty. The only way to know that is to perform a standard THD test, but you need specialized equipment for that like an Audio Precision or HP 8903b (I have the HP). You'd then capture the harmonic distortion over frequency response and compare to the specification.

[avanti1960]

Update 5/4/12 Re: Swapping out the class D JL HD900/5 for the class A-B JL 300/4 V2:

It has been 3-weeks of running the JL class A-B on the front stage and the occasional but offensive harshness found in the JL class D has yet to be observed in the new amp.
I am willing to bet dollars to donuts that if I go out right now and swap rca connectors and speaker leads to bring the HD900/5 back online for the front stage- I could insert those CDs and play those tracks that I have recorded in my log notes as being objectionably harsh- and duplicate the sound tendencies once again.
But I won't do it. I'm perfectly happy letting the 900 play bass and rear fill, although I have been tempted to bridge (2) channels just for the front mids!

[TOOSTUBBORN2FAIL]

1- The lag between switching the rca's and putting the cd's in would be more than your (or anyones) brain can accurately remember.

2- Your expecting the harshness to come back, so it will.

[subwoofery]

Originally Posted by TOOSTUBBORN2FAIL

1- The lag between switching the rca's and putting the cd's in would be more than your (or anyones) brain can accurately remember.

2- Your expecting the harshness to come back, so it will.

For #1, what happens if you take notes on a piece of paper of what you hear and feel?

Kelvin

[TOOSTUBBORN2FAIL]

Every study I've read states that your brain cant accurately remember what it heard a few seconds ago, let alone a few minutes.

[ChrisB]

Originally Posted by TOOSTUBBORN2FAIL

Every study I've read states that your brain cant accurately remember what it heard a few seconds ago, let alone a few minutes.

Please explain this to my wife for me.

[TOOSTUBBORN2FAIL]

This isnt completely scientific, but you could try this. I'm not sure if you can do this, but if you have the gear to do it, try it.

Play a song for your wife. Afterwards, go to where the amps are, and "mess with some settings", but dont really. Then get back in, and tell her that there should be more bass this time, that it wasnt set right the first time. Ask her to listen again, and see if she agrees.

Or, you can do the opposite. Play the song, then use the remote knob out of her view to slightly or raise the bass, try to make a 2-3 db change. You'll probably have to practice to get it right. Ask her if she heard anything wrong with it, and then play it again, and see if she notices.

[ChrisB]

Originally Posted by TOOSTUBBORN2FAIL

This isnt completely scientific, but you could try this. I'm not sure if you can do this, but if you have the gear to do it, try it.

Play a song for your wife. Afterwards, go to where the amps are, and "mess with some settings", but dont really. Then get back in, and tell her that there should be more bass this time, that it wasnt set right the first time. Ask her to listen again, and see if she agrees.

Or, you can do the opposite. Play the song, then use the remote knob out of her view to slightly or raise the bass, try to make a 2-3 db change. You'll probably have to practice to get it right. Ask her if she heard anything wrong with it, and then play it again, and see if she notices.

No, I meant from the perspective of when she tells me to do something and I don't do it. I'm blaming it on the fact that I can't remember what I heard seconds or minutes ago.

[TOOSTUBBORN2FAIL]

Ahh, haha. Ya, i know all about that.

[avanti1960]

Originally Posted by TOOSTUBBORN2FAIL

1- The lag between switching the rca's and putting the cd's in would be more than your (or anyones) brain can accurately remember.

I can agree with this to a certain extent- some may not accurately recall very subtle differences a few moments after the fact. I would argue that some people are better than others at recalling sound qualities.
However the opposite end of the spectrum- meaning sound qualities of more obvious distinction- most certainly can be recalled seconds if not years later. For example, I will play track (1) of a sound effects CD on May 5th 2012. It is the sound of a gong crashing at full effect. I will then play track (2) and it will feature the sound of a seagull chirping. I should be able to discern many many years later that I know the difference between the sound of a gong and a seagull and would strongly argue to that effect that I would remember the difference if an amplifier sounded like a gong or a seagull. The differences in sound qualities between a gong and a seagull are obvious and distinctive and therefore easy to recall in one's mind.
So where do you draw the line for the threshold of distinction where people can no longer recall sound characteristics with accuracy? Gong vs. seagull? loud vs. soft? slight changes in pitch?
I will again argue that the differences I heard when playing the (2) amplifiers of different class architectures were by no means subtle with certain program material. The differences were obvious. I remember them and would testify as such.

[subwoofery]

Originally Posted by TOOSTUBBORN2FAIL

Every study I've read states that your brain cant accurately remember what it heard a few seconds ago, let alone a few minutes.

I remember some poster saying the same thing. Am too lazy to search for those studies but agree
However, what happens if you take notes on a piece of paper of all the distinctive notes that you hear and feel? Wouldn't that be a pretty good way to compare two things? Objectively of course...

Kelvin

[Wesayso]

Originally Posted by subwoofery

I remember some poster saying the same thing. Am too lazy to search for those studies but agree
However, what happens if you take notes on a piece of paper of all the distinctive notes that you hear and feel? Wouldn't that be a pretty good way to compare two things? Objectively of course...

Kelvin

Probably not if you expect to hear a difference?

[ChrisB]

Originally Posted by Wesayso

Probably not if you expect to hear a difference?

I'm sure I said it somewhere else in this thread if not somewhere else on the forum... I spent many HOURS listening to my HD 900/5 when I had my Mustang, just waiting for that one note that it would produce wrong. I'd hook up my Iota DLS55 to the battery, put the car in accessory mode, and just sit there and listen with my eyes closed. I did CD, I did iPod, I did every genre known to man, and to be honest, it was a totally unfair test for the JL Audio amplifier because I NEVER treated any other amp that way since going scientific. After about 2 or 3 weeks of doing this, I concluded that the JL Audio full range class d amplifier was good enough to meet my needs in the automotive environment.

Then again, I can't hear grass grow or scream when cut, nor can I hear the electrical pulses running through the wiring in my house. In other words, take what I just wrote with a grain of salt because I make no claims of being a golden ear God among man.

[MarkZ]

You guys are totally overthinking this. But fortunately you won't remember that I said that, because your brain is only capable of storing it for a few seconds.