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Author Topic: Subwoofer amps - what are we REALLY hearing?  (Read 36588 times)

Ted Olausson

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Re: Sound Is Subjective
« Reply #60 on: February 07, 2008, 08:08:42 pm »

Andy Peters wrote on Thu, 07 February 2008 07:24

Ted Olausson wrote on Wed, 06 February 2008 22:27

Quote:


I think the way that amps are used today they do have a "sound".  It is typical to see amps driven into the non linear mode.  In fact I think it has become commonplace.  That makes a smaller system sound "louder".  



http://www.moultonlabs.com/more/power_amps_revisited/


Well, he's driving easier loads at lower SPLs than typical for SR use and it's obvious that driving the amps to the edge all night is not a requirement.

But, really, it just sounds like the guy who built the amps conservatively rated them lower than what they can really do. Which is fine, and even laudable, especially considering that he leaves some "marketing watts" on the table.

Note how they measure SPL, but not amplifier output power, which would be the better test.



No, the SPL is the single most important part, or as the quote i answered to: Noone in PA actually wants a clean sounding rig, people wants loudness and cuttrough at 97dB , and if you remove distortion et al you wont get that, even at 120dB...

The article was a followup to an earlier ampshootout where he compared amps between 35 and 250w and concluded that they were all the same regardless of power, and in the followup he says that this one is different because his reaction to the SPL is different.
http://www.moultonlabs.com/more/what_is_the_sound_of_one_amp _clipping/

Anyway, all amplifiertests on speakers should be done with fullrangematerial without any kind of crossovers, the difference can be quite remarkable.(even a 1inch driver will hold for fullrange as long as the volume is sufficiently low)

Duncan McLennan

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Re: Sound Is Subjective
« Reply #61 on: February 07, 2008, 08:20:08 pm »

Home stereo or PA?  I can easily tell the difference between both hi-fi amps and pro audio amps in my home system, even under blind test conditions.  I've done it many times.

In a PA application, I don't consider it a serious issue.  If an amplifier will get through the night without thermaling, sound pretty good, not blow up my speakers, I'm a happy guy.

Lighting weight, and low current draw are nice bonuses.
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Tim Duffin

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #62 on: February 07, 2008, 09:09:25 pm »

Bob Leonard wrote on Wed, 06 February 2008 12:52

Andy Peters wrote on Wed, 06 February 2008 13:08

Bob Leonard wrote on Wed, 06 February 2008 08:02

Yes Tim, I am aware those are all tube circuits, and;

A class C amplifier is biased beyond cutoff. The class C amplifier like the class B amplifier will draw no current with no signal input but a class B will start to draw current as soon as a signal is applied and a class C will only start to draw current when the signal strength is sufficient to go beyond the bias level. The class C amplifier is not linear but is the highest in efficiency.

In all classes of amplifier the linearity of the amplifier is determined by it's class.

The APS-20 radar on an EC-121 Willy Victor used a class "C" amplifier. RTTY, CW are often used with class "C" amplifiers, but they can not be used with SSB.


As The Good Tim says, flat view, anyone? USE THE QUOTE BUTTON.

And how is this relevant to the topic at hand? Other than to get into another mudwrestle with Duffin?

Quote:

I posted these as classic examples, and being as basic as these classes of amplifier are I would think it may be good reading material for people who may want to understand amplifiers and how they operate. Guitar players may find interest in class A/B amplifier circuits especially if they use a Fender amplifier.


And the design goals of a guitar amplifier are at cross purposes with one designed for sound reproduction.

One is a tone generator, one is not.

So the discussion is rather pointless.

-a


Andy,
I don't care about Duffin. He asked for an answer and got it. And since when are class A/B amplifiers not a part of sound reproduction. I seem to remember working with many prior to the use of transistors in amplifier output stages. I don't remember saying anything about preamplifier circuits at all. Maybe that's where your confused. Besides that the above were used as examples of amplifier class in response to someone who doesn't understand the meaning of the word linear. Ever read an RCA tube manual? Regardless of the class most amplifiers can trace their roots back to those simplistic amplifiers of days gone by in some way or another.




Fine, Ill use the quote button.

Anyways, the correct answer for my question you did not get.  The circuit which is class C is called a "gyrator" and it is not used in audio as per JR's comment.  The reason why is because it conducts only for positive values of input-- so use your imagination as to what that looks like on a scope.  I can tell that whomever wrote your quote has very little grasp of what the circuit does-- or it is very outdated information.

"Biased beyond cutoff"---lol!  thats the funniest thing I have read all week.


T


Pascal Pincosy

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #63 on: February 07, 2008, 09:15:35 pm »

Tim Duffin wrote on Thu, 07 February 2008 18:09

Anyways, the correct answer for my question you did not get.


'Scuse my language, but who gives a f*ck? This site, forum, and thread are discussing pro audio. No-one is reading this thread to find out which of the two of you has the bigger penis. Can we please move on and talk about something that matters, like cars or something?  Rolling Eyes
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Tim Duffin

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #64 on: February 07, 2008, 09:19:31 pm »

You, of all people should talk Laughing Cuz PAS speakers are better than everything else, right Rolling Eyes

I wouldn't have said anything if the info was correct in the first place.  

T

Pascal Pincosy

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #65 on: February 07, 2008, 09:38:10 pm »

Tim Duffin wrote on Thu, 07 February 2008 18:19

I wouldn't have said anything if the info was correct in the first place.

If you intent was really to educate, you would have let it go after Andy and JR set Bob straight. Instead you just had to get another word in. That's exactly how you continue to earn your 'troll' reputation.
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John Roberts {JR}

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #66 on: February 07, 2008, 09:55:02 pm »

Tim Duffin wrote on Thu, 07 February 2008 20:09




Fine, Ill use the quote button.

Anyways, the correct answer for my question you did not get.  The circuit which is class C is called a "gyrator" and it is not used in audio as per JR's comment.  The reason why is because it conducts only for positive values of input-- so use your imagination as to what that looks like on a scope.  I can tell that whomever wrote your quote has very little grasp of what the circuit does-- or it is very outdated information.

"Biased beyond cutoff"---lol!  thats the funniest thing I have read all week.


T





The gyrator circuits I am familiar with, I am only familiar with because they were used in audio. Capacitors and opamps were configured to mimic inductors in EQ circuits. Those gyrators absolutely conducted in both directions.

I see little value in talking about class C RF amps or even tube stuff here.. other than in passing.. see there it goes, it's passed. now wipe.

JR

PS.. fi fie fo fum, I smell a troll in the LAB lounge...
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Richard Rajchel

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #67 on: February 07, 2008, 10:00:50 pm »

A bit more clarification.

Just the simple fact that anyone is using the word "better" makes it subjective in the first place. In the case where the RMX improved on some top cabinet sound over the Labs, what was it that made the RMXs "better". It had to be SPL in a "pleasing to the ear" range. For example at the level you were testing at the RMX/top cabinet combination had a slight rise in SPL for the frequency range from 2k-5k or something? Just an example, but if it's audible and repeatable you should be able to measure it.

Like different microphones have different response curves, as well as speakers etc... More expensive mics might be closer to flat response, and more accurate, but that doesn't make them sound better to our ear. That slight rise in response in the 1.5k-10k range of frequencies(even if it's only a dB or 2) tends to sound clearer, or cleaner, or more presence, or any other number of descriptions for that particular sound quality.

So maybe the RMX is just not quite as accurate as the Lab with those speakers, but the result is still pleasing to the ear. Change speakers and you get a different result perhaps as well.

The question is who's going to spend the rest of their lives and millions of dollars documenting which amps work the best with each speaker in every situation?

The QSC RMX 1450 is the best sounding amp on the compression driver of bi-amped monitor XYZ, but use a Crown MA3600 for the 15" speaker and cross them over at 108.64 hz., but if the temperature is below 71.5 Fahrenheit and voltage is above 114 then use a PLX 3002 on the compression driver.

It's all sooooo ridiculous...lol.
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Tim Duffin

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #68 on: February 07, 2008, 11:33:04 pm »

I don't agree.  How can you educate somebody without saying anything?  And btw-- this is the lounge, call me whatever you like--just don't be a sore loser. Laughing   The original post doesn't serve to educate or inform, so why should I?

T

Jeff Hague

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #69 on: February 08, 2008, 12:08:19 am »

Andy Peters wrote on Wed, 06 February 2008 15:40

Silas Pradetto wrote on Wed, 06 February 2008 13:35

Damping factor is the load impedance divided by the output impedance of the amplifier. This means, with an 8 ohm load and a .01 ohm output impedance of the amplifier, you would have a damping factor of 800. Damping factor has quite a bit to do with bass quality. It is related to cone control such that a higher damping factor is more control. If there is more control, the woofer flaps around less and relies less on it's own suspension to return it to the "zero" point in it's travel, making everything sound "punchier." I hope that kind of made sense.


You forget the salient point: overall damping factor is severely degraded by the cable between the amp and the driver, as that cable's resistance adds to the amp output impedance.

In fact, the cable resistance essentially sets the damping factor, making amplifier damping factor irrelevant except maybe as a marketing bullet point.

This horse is dead.

Please stop beating it.

-a


So, why wouldn't a higher damping factor be desirable anyway? If the copper between the amp and the speaker degrades it, wouldn't a higher damping factor to begin with cause less degradation? Is the effect that overwhelming (ie non-linear)? It seems to me that the effect of copper wire on damping factor is linear, as is the effect of speaker impedance. An amp with a damping factor of 200 into an 8 ohm load will have a damping factor of 100 into a 4 ohm load, right? In that light, the higher the damping factor of the amp to begin with (prior to the speaker cable), the better...

Ive never beat a dead horse that I didn't like...
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