# Percieved Loudness, Class D vs Class A/B and High Voltage vs. High Current



## MikeT1982 (Jul 6, 2011)

Two situations that i always found interesting throughout my time with the car audio scene were as follows. Watt for watt Class A/B amps seemed louder by ear than Class D and watt for watt higher ohm high voltage setups seemed louder than high current low impedance setups. I am sure there are tons of reasons this could have happened and maybe it's in my head LoL... but i figure it would be a neat thing to discuss. One example was a MMATS D300HC wired for optimum impedance vs a Precision power PC2350. I was well aware that an un-modded D300HC was capable of 1,728 WRMS as the old Autosound test showed, however in a customers car, the PPI rated 1,400 WRMS not only scored higher but sounded snappier and louder too by perception. I think the MMATS scored a 144 (wall of 4 old W4 JL's sealed) and the PPI scored a 147 on an old Audio Control meter. I still preferred to run the MMATS myself due to efficiency and whatnot. And the guy had a solid power system with a large alternator and multipel batteries to back up the current demand too. Interesting. Another occurance was when I ran a Soundstream Reference Class A 3.0 at .5 ohms mono and then switched to a PPI PC275 making 300 WRMS at 4 ohms mono. The higher ohm setup sounded louder, same woofer manufacturer (JL) but different coils. Same box.

Edit - Well i just found the post below pretty covering this HC vs HV, but i'll leave this as i truly feel the same wattage on same drivers with higher ohm coils and higher voltage but lower current are louder for the exact same wattage....vs the same power whipped up through more amps less voltage and lower resistance.


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## ChrisB (Jul 3, 2008)

The only way to truly test out your perceived loudness theory among the different classes of amplifiers would be to measure each amplifier then retest. I'm willing to bet that max output for an SPL burp was not equal among the different classes of amplifiers.

Then again, I witnessed the same vehicle score differently on the TermLab at different events with NOTHING changing system wise. I'm talking a 4 to 6 decibel swing too. Explain that one!

My experience with high voltage versus high current was that the high voltage amplifiers that I used would fall flat on their faces every time they encountered a max power situation lasting more than a few seconds. Even on the test bench most of them would shut down prior to clipping on test tones played into dummy loads. It was truly a disappointing experience since those amplifiers commanded such a high dollar on the secondary market. So much for the "you get what you pay for" myth!


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## MikeT1982 (Jul 6, 2011)

That's really neat man, very interesting! Yeah i actually tried to erase this post after seeing the other informative one about HV vs HC amps. I wish i would have read/searched first but i was so excited to see how much oldschool related stuff was here and wanted to start chatting LoL. I wasn't sure how to erase it though. Anyways yeah i never meant to favor one or the other, i'd personally use Class D all day for subwoofers it's pretty much a no brainer with efficiency and raw power and all. I may have been totally off with my observations as well. I guess i coudl say the A/B's seemed to have a more "snappiness" and firmness to the bass, maybe it was lower THD i was seeing. The numbers could have been meter error for sure!


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## slater (Nov 21, 2010)

i know the last thing wrote on this topic was 2 weeks ago. but i just want to throw my 2 cents in . the higher the ohms the more damping factor the amp has and the lower the ohms the lower the damping factor is. that's why it could sound snappier at the higher ohms, because it has more control over the sub. 

correct me if im wrong, but amps that are cea certified test the damping factor at 4 ohms. . .


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## subwoofery (Nov 9, 2008)

slater said:


> i know the last thing wrote on this topic was 2 weeks ago. but i just want to throw my 2 cents in . the higher the ohms the more damping factor the amp has and the lower the ohms the lower the damping factor is. that's why it could sound snappier at the higher ohms, because it has more control over the sub.
> 
> correct me if im wrong, but amps that are cea certified test the damping factor at 4 ohms. . .


Damping factor doesn't do anything and is not an important spec either: 
http://www.diymobileaudio.com/forum/449977-post34.html 
http://www.diymobileaudio.com/forum/605531-post11.html 

Kelvin


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## ChrisB (Jul 3, 2008)

subwoofery said:


> Damping factor doesn't do anything and *is not an important spec either:*
> http://www.diymobileaudio.com/forum/449977-post34.html
> http://www.diymobileaudio.com/forum/605531-post11.html
> 
> Kelvin


Watch it, the pro audio guys are going to string you up for saying damping factor is NOT an important spec. When speaker wire runs exceed 50 feet all the way up to several hundred feet of speaker cable between the amplifier and the speakers, damping factor IS important! A low damping factor on touring band/DJ amplifier will more than likely result in lots of magic smoke just as the crowd gets into the groove.

On the other hand, I am in agreement that the damping factor spec is useless in a car where speaker cable runs will rarely exceed 20 feet.


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## subwoofery (Nov 9, 2008)

ChrisB said:


> Watch it, the pro audio guys are going to string you up for saying damping factor is NOT an important spec. When speaker wire runs exceed 50 feet all the way up to several hundred feet of speaker cable between the amplifier and the speakers, damping factor IS important! A low damping factor on touring band/DJ amplifier will more than likely result in lots of magic smoke just as the crowd gets into the groove.
> 
> On the other hand, I am in agreement that the damping factor spec is useless in a car where speaker cable runs will rarely exceed 20 feet.


Guess I should just hide for at least the next 20 years then 









:laugh:
Kelvin


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## cleansoundz (May 14, 2008)

My buddies old system which consisted of a 1998 RF Punch 250.1 Power in a sealed enclosure pushing 2 Kicker CVR 15's was loud and clean and clear. His system was louder than many systems I heard pushing 1000+ watts to their woofers. The 250.1 maxed out at 750 class AB watts. He always kept his bass on -5 btw. I eventually got him years ago with my old setup which was a RF t10001BD and 2 12 inch RF T1s in a ported enclosure tuned to 40hz. However the t10001BD at 1 ohm was pushing 1500 watts.


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## envisionelec (Dec 14, 2005)

ChrisB said:


> Watch it, the pro audio guys are going to string you up for saying damping factor is NOT an important spec. When speaker wire runs exceed 50 feet all the way up to several hundred feet of speaker cable between the amplifier and the speakers, damping factor IS important! A low damping factor on touring band/DJ amplifier will more than likely result in lots of magic smoke just as the crowd gets into the groove.
> 
> On the other hand, I am in agreement that the damping factor spec is useless in a car where speaker cable runs will rarely exceed 20 feet.


Damping factor has nothing to do with what you've described.

And it's an unimportant spec for _most _applications. :laugh:


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## 1998993C2S (Feb 2, 2011)

ChrisB said:


> Watch it, the pro audio guys are going to string you up for saying damping factor is NOT an important spec.


+ 1 . Driver coils and amplifiers are complicated. And to complicate the issue in a screwball way is the marketing departments words of wisdom.

Cheers, Mike


working on my first SQ build. A MY98 911 coupe, a P99RS head unit, a trio of A900s amps and to round things out Dynaudio's / ATC's.


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## ChrisB (Jul 3, 2008)

envisionelec said:


> Damping factor has nothing to do with what you've described.
> 
> And it's an unimportant spec for _most _applications. :laugh:


So damping factor has nothing to do with how the amplifier deals with back emf from a driver (implied subwoofer here) that is 50 to 100 feet away while simultaneously sending a musical signal? Damn, the spec is even more useless than I thought.


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## rommelrommel (Apr 11, 2007)

cleansoundz said:


> My buddies old system which consisted of a 1998 RF Punch 250.1 Power in a sealed enclosure pushing 2 Kicker CVR 15's was loud and clean and clear. His system was louder than many systems I heard pushing 1000+ watts to their woofers. The 250.1 maxed out at 750 class AB watts. He always kept his bass on -5 btw. I eventually got him years ago with my old setup which was a RF t10001BD and 2 12 inch RF T1s in a ported enclosure tuned to 40hz. However the t10001BD at 1 ohm was pushing 1500 watts.


Yeah, but was your bass on -5?


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## 14642 (May 19, 2008)

ChrisB said:


> Watch it, the pro audio guys are going to string you up for saying damping factor is NOT an important spec. When speaker wire runs exceed 50 feet all the way up to several hundred feet of speaker cable between the amplifier and the speakers, damping factor IS important! A low damping factor on touring band/DJ amplifier will more than likely result in lots of magic smoke just as the crowd gets into the groove.
> 
> On the other hand, I am in agreement that the damping factor spec is useless in a car where speaker cable runs will rarely exceed 20 feet.


the silly notion of damping contributed to the amplifier is completely undone by the inherent design of the speaker. Inductance causes motion and a low output impedance would cause the energy stored in the speaker's inductance to be dissipated more quickly. The amplifier's output impedance would, ideally restrict (or enable) current flow. The conventional wisdom is that a lower output impedance provides a lower-resistance path to ground. Unfortunately, all of that is out the window because the speaker's DCR is in series with the inductor and the output impedance of the amplifier. The sum of the DCR and the output impedance regulate the current flow. Put 50 feet of cable in between, and you have to add that resistance to the others that are in series in the circuit. Then, if you have a 3 ohm DCR, 1 ohm of speaker cable and .00000000000000004 ohms of output impedance, which component determines circuit damping? 

Voltage is dropped across the resistors according to their resistance (more resistance means more voltage drop), but current is constant in a series circuit. 

Hmmm....sounds like the speaker's DCR, to me.


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## 14642 (May 19, 2008)

ChrisB said:


> So damping factor has nothing to do with how the amplifier deals with back emf from a driver (implied subwoofer here) that is 50 to 100 feet away while simultaneously sending a musical signal? Damn, the spec is even more useless than I thought.


It has something to do with it, but VERY little. It's almost completely ineffective in HELPING the situation if the output impedance is low, but if the output impedance is really high--like similar to the speaker's DCR, then it can have an almost significant effect in making it WORSE.

For a subwoofer, it just doesn't matter. For a full range system, a high output impedance can have an effect on frequency response. 

This is why CEA 2006 uses EDF and output regulation to describe these aspects of performance. 

Ahhh...marketing...


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## minbari (Mar 3, 2011)

Steven Mantz has a great article to do with amplifier dampening factors. he basically says the same thing. it is an over-hyped and mostly useless spec. once you figure speaker DCR, as andy mentioned, then the best amplifiers only have a dampening factor of less then 20, which is more than fine. you look at tube amplifiers that everyone seems to think are the best audiophile grade amplifiers, they are in the single digits


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