Does class D have the Heft of SS

[Figjam]

We have yet to discover the Hefton particle; a nanoparticle said to give amps their heft.

 

[svtb15]

But but but (best stuttering impression) .. If they do that, we may see some 800 Watt amps turning out o be only 350! ... Maybe not that low. But You Know what i mean..
I agree 100%.
I remember the days when power amps were rated 20hz to 20k +,- blah blah THD < 0.002% from 20Hz to 1kHz etc etc..
You don't see that these days except for a few..
It would be nice to see a Standardization, so that we have reference point that is solid and repeatable .

I'd like to see some standards of measure. I like to see a real continuous power rating, a real average power rating. I got no use for burst power rated down in milliseconds.


If there is something such as "heft" some amps are going to have some aren't. It is not the class that determines it but actual design and measurement. Measurement again some mutually agreed on standards.

 

[seamonkey]

But but but (best stuttering impression) .. If they do that, we may see some 800 Watt amps turning out o be only 350! ... Maybe not that low. But You Know what i mean..
I agree 100%.
I remember the days when power amps were rated 20hz to 20k +,- blah blah THD < 0.002% from 20Hz to 1kHz etc etc..
You don't see that these days except for a few..
It would be nice to see a Standardization, so that we have reference point that is solid and repeatable .

Maybe they don't have to call it a "Watt" anymore?
Maybe "Heftons" like Figjam recommended
Make it easy to get 1GB Hefton rating. Big numbers are good marketing.

 

[Jim C]

But but but (best stuttering impression) .. If they do that, we may see some 800 Watt amps turning out o be only 350! ... Maybe not that low. But You Know what i mean..
I agree 100%.
I remember the days when power amps were rated 20hz to 20k +,- blah blah THD < 0.002% from 20Hz to 1kHz etc etc..
You don't see that these days except for a few..
It would be nice to see a Standardization, so that we have reference point that is solid and repeatable .

So, many feel that class D bass amps have less heft.
How about professional power amps?
For example, assuming output power being the same, does a Crest Pro-Light have the same heft of say a Crest CA series?

 

[Dave Hill]

Much of the discussion in this thread has been about pro audio systems - which means full-range PA

But let's remember we are talking BASS here

The difference between a good quality amp and a mediocre amp in the bass frequency range is its ability to deliver constant power down to the lowest frequency to be amplified

Manufacturers quote "frequency response" at one watt rms but what happens at rated power ?

Compare the rated power at 1 kHz to rated power at 40 Hz and you will see why some amps deliver better bass

i.e. - if a power amp delivers 100 watts at 1kHz and only 80 watts at 40 Hz then that will be heard as weak bass

You can offset this to some extent with preamp tone controls and graphic EQ but that approach requires a higher rated amp

But ultimately the limitation will be heard if the power is cranked up far enough - we cannot replace what is not there in the first place

Maybe this characteristic is what is described as "heft"

The PA pros I know use their best amps for the sub woofers - i.e a split system for highs, mids and lows

Good question. I wonder if the guys who have done the blind test (@agedhorse) were listening full PA mix or bass guitar only.

 

[agedhorse]

Much of the discussion in this thread has been about pro audio systems - which means full-range PA

But let's remember we are talking BASS here

The difference between a good quality amp and a mediocre amp in the bass frequency range is its ability to deliver constant power down to the lowest frequency to be amplified

I disagree here. What sets a GREAT bass amp apart from a mediocre bass amp is the voicing, the tone and texture that works well with a palyer's own personal style, tastes, bass and speakers. Extended low frequency response at high power is in fact a big negative for many players as evidences by the popularity of the sweep high pass filter in more than one (very) popular and respected amp/preamp.

Manufacturers quote "frequency response" at one watt rms but what happens at rated power ?

Compare the rated power at 1 kHz to rated power at 40 Hz and you will see why some amps deliver better bass

i.e. - if a power amp delivers 100 watts at 1kHz and only 80 watts at 40 Hz then that will be heard as weak bass

Actually, most amps produce rated power easily down to 20Hz, especially class D amps. This is not at all difficult from a technical perspective, but from a player's perspective this almost always causes more problems than it pretends to solve. Once you start driving a real world bass cabinet, you have to deal with the system response, what happens when this speaker is driven in regions where there is acoustic unloading of the driver with the air mass. When this happens (mostly at very low frequencies starting around the F3 point but certainly noticeable at F6), the non-musical distortion components go way up, and the mechanical power handling quickly falls, the results being a muddy, sloppy, indistinct low end that interferes with the rest of the spectrum. This is why virtually every pro level bass amp is high passed these days.

In pro audio, this is just as much of an issue, and virtually every high powered subwoofer is highpassed as well.

You can offset this to some extent with preamp tone controls and graphic EQ but that approach requires a higher rated amp

But ultimately the limitation will be heard if the power is cranked up far enough - we cannot replace what is not there in the first place

Maybe this characteristic is what is described as "heft"

No, you can not replace this with eq, because once a cabinet reaches its limits of low frequency extension and output, there simply is no more of anything to be had.

The PA pros I know use their best amps for the sub woofers - i.e a split system for highs, mids and lows

The pros I know (and I am one of them in the pro audio side of the industry) strongly disagree. They use amps that have sufficient power for the job. "best" amps never enter the discussion, just the most APPROPRIATE amps. Many pro houses have standardized on amps and use the same model for every band (sub/low/mid/high). This has been made much easier because of the advanced limiting and power management algorithms available in DSP. Of course, you may not be aware of what's really happening at the (real) pro level, but that's the life I lived for a very long time.

Class-d is more efficient, so given the same power supply there is less waste as heat, and more can go to actual output.

I'd like to see some standards of measure. I like to see a real continuous power rating, a real average power rating. I got no use for burst power rated down in milliseconds.

It only takes some manufacturers to agree. Consumers must demand it. And hopefully it's not legislation, but actual cooperation. Right now manufacturers have gone just the opposite route. Choosing to not agree and argue that their methods are the single best approach to ratings. Pure divergence based on marketing.

If there is something such as "heft" some amps are going to have some aren't. It is not the class that determines it but actual design and measurement. Measurement again some mutually agreed on standards.

Except that continuous power ratings make no sense in audio. BURST power is an entirely different thing, and there are a wide variety of methods in this area as well. Most pro companies that provide a burst rating in RMS metrics, and define the mark to space ratio and the mark to space time because different burst ratings apply to different types of signal and different spectrum ranges. It CAN be very valuable information if you understand what it provides.

The industry is indeed going towards duty cycle rating, mainly because it can be virtually guaranteed that audio of ANY type will NEVER be 100% duty cycle. For example, 25% duty cycle (6 dB of dynamics relative to average baseline) is pretty darn heavily compressed, and sounds that way... really squashed.

But but but (best stuttering impression) .. If they do that, we may see some 800 Watt amps turning out o be only 350! ... Maybe not that low. But You Know what i mean..
I agree 100%.
I remember the days when power amps were rated 20hz to 20k +,- blah blah THD < 0.002% from 20Hz to 1kHz etc etc..
You don't see that these days except for a few..
It would be nice to see a Standardization, so that we have reference point that is solid and repeatable .

I agree, standards would be nice. The problem is that different methods of rating an amp apply to different condition. I remember the spec. races, the vanishing distortion, the DC to light bandwidths AND I remember all the drawbacks that came along with these new approaches. Horrible clipping behaviors that gave the "new" solid state amps a deservedly bad reputation. Instability issues so bad that spontaneous combustion was not all that uncommon. I remember a now long gone hi-fi brand Nikko, their big rack mount amps had fantastic specs BUT as soon as you got even close to clipping the amps would chatter, chirp, and ultimately explode. Upon exploring what was really happening, it was due to a loss of feedback along with VI limiting event that resulted in unstable open loop conditions. As I was running a warranty service center at the time, I reported this to their engineering department but marketing declined to act upon it because the spec numbers were deemed far more important than the actual performance. The solution was detuning and being more conservative with the loop management, completely solved the reliability and audio problems, but this increased THD from .008% to about .08%. In the end, virtually every amp sold came back blown up, the cost to repair was very high, and the brand ended up being scrapped. The sad thing is the basic design of the amp was quite good, it was the fixation on numbers that was the problem. At the same time, tube power amps were still being sold, THD was typically ~1% but they entered and exited clipping gracefully and there were no reliability issues. The difference between real world performance and the fixation on numbers was not lost on me, and it saddens me to see folks focusing on unrealistic numbers/specs rather than on real world performance. This all happened in the late 1970's, so the concept has been understood for decades. In fact Randell Smith (founder of Mesa) followed the same course of real world performance rather than worrying about numbers, his results in this industry are pretty convincing. This may be why I was a good fit with the company, even with my numbers based engineering background.

 

[BadExample]

So, many feel that class D bass amps have less heft.
How about professional power amps?
For example, assuming output power being the same, does a Crest Pro-Light have the same heft of say a Crest CA series?

Funny, you never hear that about power amps. Just happy joyous stories. Maybe since the amp section is relatively cheap, they buy a higher rated power amp then their class D bass amp they gave up on, and have overhead? Just a guess and not meant to poke anyone in the eye. Well, not this post. You'll know if there is an eye poke involved Could also be selective memory (of what others have said) on my part.

 

[eyeballkid]

I feel like you guys are getting lost in the weeds of mathematical specs and audio theory. Yes, thats important, but what it comes down to is the experience you have using it. The engineers may tell you some car is the finest and most efficient engineered automobile in history and it can simply be just not practical or deliver what each driver needs. Im aware of all the science involved, but from a user/listeners experience Class D just doesnt hit you with any real solidity. I cant explain why. Im sure Agedhorse will know the one class D amp that actually does deliver, hell... he may have helped design it, but I aint heard it yet, and with my body finally starting to show its years of wear and tear I SOREly wish I could find it, but... im still lugging iron and using an ice pack when I need it. ;-)

 

[BadExample]

Actually, most amps produce rated power easily down to 20Hz, especially class D amps. This is not at all difficult from a technical perspective, but from a player's perspective this almost always causes more problems than it pretends to solve. Once you start driving a real world bass cabinet, you have to deal with the system response, what happens when this speaker is driven in regions where there is acoustic unloading of the driver with the air mass. When this happens (mostly at very low frequencies starting around the F3 point but certainly noticeable at F6), the non-musical distortion components go way up, and the mechanical power handling quickly falls, the results being a muddy, sloppy, indistinct low end that interferes with the rest of the spectrum. This is why virtually every pro level bass amp is high passed these days.

In pro audio, this is just as much of an issue, and virtually every high powered subwoofer is highpassed as well.

Not to mention the power required to make the deep bass sound as loud as higher freqs to the human ear. At least short term, until the eardrums break, bleed and we do like our parents always said, turn it down. Now that deep bass you feel more than hear is a different story, but still capable of separating you from your eardrums.

 

[Loring]

I feel like you guys are getting lost in the weeds of mathematical specs and audio theory. Yes, thats important, but what it comes down to is the experience you have using it. The engineers may tell you some car is the finest and most efficient engineered automobile in history and it can simply be just not practical or deliver what each driver needs. Im aware of all the science involved, but from a user/listeners experience Class D just doesnt hit you with any real solidity. I cant explain why. Im sure Agedhorse will know the one class D amp that actually does deliver, hell... he may have helped design it, but I aint heard it yet, and with my body finally starting to show its years of wear and tear I SOREly wish I could find it, but... im still lugging iron and using an ice pack when I need it. ;-)

Your opinion is simply and unequivocally wrong. I have owned tube (SVT - early 80's vintage), Mosfet SS (Trace Elliot - made in England vintage - mid 80's) and now a class D (Genzler Magellan 800). Aside from the tonal differences - all of them hit. The Ampeg probably the most as the 8x10 was about the same height and my torso and that is a lot of speaker mass. As far as attack goes - the magellan is the tightest. It is very punchy. I have also tried the Mesa D800 and it also smacks very authoritatively.

Perhaps your experience has more to do with the speakers they are plugged into, or maybe you're testing entry level stuff vs SS high end gear? I don't know. Maybe your statement should be more like "of the class D amps with ____ speakers I've tried blah blah blah".

 

[agedhorse]

Good question. I wonder if the guys who have done the blind test (@agedhorse) were listening full PA mix or bass guitar only.

Both, and extensive.

 

[Jim C]

Both, and extensive.

Andy, were there any differences that you heard between the 2 design styles (both MI and power amp)?

 

[MordBass]

Been playing for 20+ years... had more amps than I can recall.
Recently used a TH500 as my main head for a year, sold it and got a Crest CA9. Sounds a million times better.

FWIW I also grabbed an MB200 that I toss in my gigbag for rehearsals here and there.

Also, to be fair I owned them simultaneously for a few weeks. Even at lower volumes the sled was better. Now dont get me wrong, if you play churches or small bars where you use a 1x12 or 2x10 and then DI out... the Aggie was fantastic. But it doesnt even come close to bringing the thunder like a huge SS. I dont even know what to call it... the X factor? the 6th sense? the 4th dimension? the soul? the wrath? Who knows what its called.

 

[Loring]

Been playing for 20+ years... had more amps than I can recall. Who knows what its called.

Placebo?

 

[eyeballkid]

Your opinion is simply and unequivocally wrong. I have owned tube (SVT - early 80's vintage), Mosfet SS (Trace Elliot - made in England vintage - mid 80's) and now a class D (Genzler Magellan 800). Aside from the tonal differences - all of them hit. The Ampeg probably the most as the 8x10 was about the same height and my torso and that is a lot of speaker mass. As far as attack goes - the magellan is the tightest. It is very punchy. I have also tried the Mesa D800 and it also smacks very authoritatively.

Perhaps your experience has more to do with the speakers they are plugged into, or maybe you're testing entry level stuff vs SS high end gear? I don't know. Maybe your statement should be more like "of the class D amps with ____ speakers I've tried blah blah blah".

well so much for civil discussion! Lets just yell "WRONG!!" at each other. lol
look man.. Ive tried out, and even more disappointingly, seen numerous bands I love who switched to class D on bass. They played thru many different cabs. All sounded thin and sterile in comparison to their sound with either tube or actual SS. Now, most of these have been louder rock. Perhaps these work great for jazz guys, or cover bands, but Im sorry, my experience both playing and listening to bands using them has been very underwhelming. But yeah.. Im wrong for hearing a difference.

and look, Im not trying to be "anti-Class D" but it should be a simple logical step to understand that EVERY gear choice in EVERY area of life has its advantages and trade offs. Some tools work for some applications. Everyone wants to act as if Class D is ALL positive outcomes and no drawbacks, like its some kind of audio miracle cure. Its not. Tubes have their pluses, and their obvious minuses. So does Class D. Its biggest two drawbacks are sudden no warning shutdowns at thermal/power limits, and a noticeable one dimensional tone. Some dont mind that drawback for the the portability and weight gains that deliver a tone 98% of people wont distinquish. But... for some of us, its a deal breaker. Why is that so objectionable to consider?

 

[agedhorse]

Andy, were there any differences that you heard between the 2 design styles (both MI and power amp)?

Not among those that were well designed and avoided any "poor engineering" artifacts.

 

[MordBass]

Placebo?

Nah, Id call it experience. Theres just a difference. The class D is lacking something once you get to a volume where youre playing with a drummer/other musicians.

 

[svtb15]

One person's "drawbacks" is another person's NIRVANA.. Too much subjectiveness.

I disagree here. What sets a GREAT bass amp apart from a mediocre bass amp is the voicing, the tone and texture that works well with a palyer's own personal style, tastes, bass and speakers. Extended low frequency response at high power is in fact a big negative for many players as evidences by the popularity of the sweep high pass filter in more than one (very) popular and respected amp/preamp.



Actually, most amps produce rated power easily down to 20Hz, especially class D amps. This is not at all difficult from a technical perspective, but from a player's perspective this almost always causes more problems than it pretends to solve. Once you start driving a real world bass cabinet, you have to deal with the system response, what happens when this speaker is driven in regions where there is acoustic unloading of the driver with the air mass. When this happens (mostly at very low frequencies starting around the F3 point but certainly noticeable at F6), the non-musical distortion components go way up, and the mechanical power handling quickly falls, the results being a muddy, sloppy, indistinct low end that interferes with the rest of the spectrum. This is why virtually every pro level bass amp is high passed these days.

In pro audio, this is just as much of an issue, and virtually every high powered subwoofer is highpassed as well.



No, you can not replace this with eq, because once a cabinet reaches its limits of low frequency extension and output, there simply is no more of anything to be had.



The pros I know (and I am one of them in the pro audio side of the industry) strongly disagree. They use amps that have sufficient power for the job. "best" amps never enter the discussion, just the most APPROPRIATE amps. Many pro houses have standardized on amps and use the same model for every band (sub/low/mid/high). This has been made much easier because of the advanced limiting and power management algorithms available in DSP. Of course, you may not be aware of what's really happening at the (real) pro level, but that's the life I lived for a very long time.




Except that continuous power ratings make no sense in audio. BURST power is an entirely different thing, and there are a wide variety of methods in this area as well. Most pro companies that provide a burst rating in RMS metrics, and define the mark to space ratio and the mark to space time because different burst ratings apply to different types of signal and different spectrum ranges. It CAN be very valuable information if you understand what it provides.

The industry is indeed going towards duty cycle rating, mainly because it can be virtually guaranteed that audio of ANY type will NEVER be 100% duty cycle. For example, 25% duty cycle (6 dB of dynamics relative to average baseline) is pretty darn heavily compressed, and sounds that way... really squashed.



I agree, standards would be nice. The problem is that different methods of rating an amp apply to different condition. I remember the spec. races, the vanishing distortion, the DC to light bandwidths AND I remember all the drawbacks that came along with these new approaches. Horrible clipping behaviors that gave the "new" solid state amps a deservedly bad reputation. Instability issues so bad that spontaneous combustion was not all that uncommon. I remember a now long gone hi-fi brand Nikko, their big rack mount amps had fantastic specs BUT as soon as you got even close to clipping the amps would chatter, chirp, and ultimately explode. Upon exploring what was really happening, it was due to a loss of feedback along with VI limiting event that resulted in unstable open loop conditions. As I was running a warranty service center at the time, I reported this to their engineering department but marketing declined to act upon it because the spec numbers were deemed far more important than the actual performance. The solution was detuning and being more conservative with the loop management, completely solved the reliability and audio problems, but this increased THD from .008% to about .08%. In the end, virtually every amp sold came back blown up, the cost to repair was very high, and the brand ended up being scrapped. The sad thing is the basic design of the amp was quite good, it was the fixation on numbers that was the problem. At the same time, tube power amps were still being sold, THD was typically ~1% but they entered and exited clipping gracefully and there were no reliability issues. The difference between real world performance and the fixation on numbers was not lost on me, and it saddens me to see folks focusing on unrealistic numbers/specs rather than on real world performance. This all happened in the late 1970's, so the concept has been understood for decades. In fact Randell Smith (founder of Mesa) followed the same course of real world performance rather than worrying about numbers, his results in this industry are pretty convincing. This may be why I was a good fit with the company, even with my numbers based engineering background.

 

[eyeballkid]

Nah, Id call it experience. Theres just a difference. The class D is lacking something once you get to a volume where youre playing with a drummer/other musicians.

I'll save Loring the trouble and just go ahead and tell you you're unequivocally wrong and using crap speakers! lol

 

[agedhorse]

One person's "drawbacks" is another person's NIRVANA.. Too much subjectiveness.

That's the root of the problem, we are trying to quantify subjectivity.