what does this mean

[.::DuD3::. 10+ year member]

Class D amps are preferred for driving subwoofers because they are generally more efficient than Class A/B amps but at the sacrifice of lessened SQ. For bigger wattage demands most users prefer the lower current draw of the Class D units over the larger power input demands of Class A/B amps.
This isn't to say that Class A/B amps aren''t well-suited for sub usage but, like everything else, it has its drawbacks. Yes, your average Class A/B amp will have a low-pass crossover section in it in case the end user wants to implement it in that manner. Additionally more and more aftermarket headunits at most pricepoints except the most budget of units, have their own inbuilt crossovers which make having that low-pass crossover outboard somewhere (whether it be a function of the amp, an outboard processor/crossover of some kind, etc) unnecessary.

Some people prefer the overall sound of an A/B amp over a D....some have found really great deals that they couldn't reasonably pass on, etc etc. There are many varied reasons why someone would go with an A/B amp over a D for their subs.

It all boils down to what fits your needs/budget/preferences the best. Once those parameters have been established it's time to go spend some money!

just curious, how is there going to be a difference between the two amps?? and dont say thd% and snr because you can't really hear the differences beyond a certain point.

 

[squeak9798 5,000+ posts]

Because it wasn't designed to reproduce any frequencies higher than that.

But it's not as if the amp just ceases to have any output beyond the "rated" frequency response. Generally the frequency response of an amplifier is measured in much the same way as a speaker's, with the rated frequency response being the point at which the frequency response has rolled off by some decibel level, such as -1db or -3db, and beyond this point the amplifier would continue to have output, however at a gradually increasing level of attenuation.

 

[XTRProBoy 10+ year member]

^Just to clarify a bit more... Class D amps designed for low frequencies only actually have a low pass crossover set at a value such as 200Hz or 250Hz. If the crossover weren't there, the amp wouldn't actually stop producing sound after that frequency but would do so rather horribly, LOL. After the lower frequency range the reproduction of sound becomes quite bad--filled with distortion and noise.

Therefore every Class D amp will have a low pass crossover such as that built-in and non defeatable (the best you can do is dial it up to the highest frequency allowed). The crossover usually has a slope of -12dB/octave or greater so yes it would have some small output but several "dB down" after the crossover frequency.

The fact that most Class Ds are only designed for low frequency and have such a crossover is of no real issue anyway. Since they are designed to drive subs, that LP crossover will usually be dialed down to 80Hz or so (or crossed over at the HU at such a frequency), meaning they aren't usually used for anything even near 250Hz anyway.

There are some class D designs that offer full range operation, but they are not that common. Class T is also very similar in efficiency and also offers full-range operation.

 

[Prowler573 5,000+ posts]

But it's not as if the amp just ceases to have any output beyond the "rated" frequency response. Generally the frequency response of an amplifier is measured in much the same way as a speaker's, with the rated frequency response being the point at which the frequency response has rolled off by some decibel level, such as -1db or -3db, and beyond this point the amplifier would continue to have output, however at a gradually increasing level of attenuation.

Abolutely right.

I guess I was more than a bit vague with my previous statement. Like you've said, it isn't as if the amp simply won't reproduce frequencies outside of its stated range but my statement, when taken literally, still remains true. The amp wasn't designed (intended) for real use outside of that range and as such is only well-suited for powering subwoofers.

But! I'll happily concede that the info contained in your post realistically should have been included in mine so //content.invisioncic.com/y282845/emoticons/bowdown.gif.b85b23b82970bd22fb6b549c3392f016.gif to your superior supply of information. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Therefore every Class D amp will have a low pass crossover such as that built-in and non defeatable (the best you can do is dial it up to the highest frequency allowed). The crossover usually has a slope of -12dB/octave or greater so yes it would have some small output but several "dB down" after the crossover frequency.

The monoblock I use in my personal setup would disagree with you, XTR. The LP crossover in my KAC-X401M is completely defeatable. I like the steeper crossover slope available in my HU so I use that and the LP crossover in my Class D is turned off. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[thch 10+ year member]

since many people will overdrive their amps, there is some merit in looking at clipping behaviors between the amps.

the class D design has inherient difficulties that are different from class AB designs.

the mechanisms for distortion, noise, and removal thereof are different between the two amps.

because class D is still rapidly evolving, and because class D is really a HUGE class of amplifiers, its not unreasonable that unfair generalizations were made based upon the performance of some class D amps.

 

[NebBlackshirts 10+ year member]

LOL nevermind... I found this information about Antarctica just now...
"There are no permanent human residents and Antarctica has never had an indigenous population. "

//content.invisioncic.com/y282845/emoticons/hilarious.gif.02a037aad04aa96f19982b298a3d70a8.gif

thats all //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif