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Author Topic: Subwoofer amps - what are we REALLY hearing?  (Read 29606 times)

Richard Rajchel

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Re: Sound Is Subjective
« Reply #30 on: February 05, 2008, 07:34:25 pm »

Could it be that the amps these days are just being built closer to the "edge" of acceptable sound. Yesteryears 1000 watt amp was so over-built that it could probably take a nasty 5000 watt spike or more and not even sweat. Todays amps based on ICs and switching power supplies just simply don't have as much in reserve. Sure a Class H or whatever powered amplifier can chug along at 90% efficiency, but when the voltage sags it just can't keep up. That old 100 pound/1000 watt amp had capacitors the size of a house and matching transformers and heat sinks too probably. I would guess that if input voltage, current, etc... was kept constant that todays amps could easily compare to older ones. In the real world however power sags/spikes are as common as groupies at a heavy metal concert.
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SteveKirby

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Re: Sound Is Subjective
« Reply #31 on: February 05, 2008, 08:35:29 pm »

Chuck Fry wrote on Tue, 05 February 2008 18:04

Hmmm... resonant circuits... could a Class C power amp be useful for those "one-note" car audio subs you hear booming down the road?  Laughing

Many years ago I worked with a guy who got a patented on a video sweep amplifier that fed the deflection coil's back emf from the flyback into storage for the next sweep.  Huge increase in efficiency.  I asked him about car sub amps as those guys want all the output for a given input current that they can get, regardless of quality.  He'd have owned the market.  He felt that car audio was beneath his dignity as an engineer.  Too low in frequency to be high tech enough for him.
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Garry Anderson

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #32 on: February 06, 2008, 02:34:31 am »

In a previous thread I offered several technical explanations on why different amps with similar specs would sound different driving a system..... and was basically ignored.

My conclusion is it all comes down to "I bought this amp so it's better than yours..." syndrome.

I'm not going to waste my time typing it all again because all that will happen is that another thread will start up again next week....I bought a Crown DC300A last week and it has a much better bass than my old Lab FQ10000.... Sad
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Keagan Corcoran

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #33 on: February 06, 2008, 07:11:24 am »

This seems to have gone off topic.... my respone to the original post.

Alexander B Larsson wrote on Tue, 05 February 2008 10:11

I am still searching for that "big amp" for the bass boxes, but the more I read, the more contradictory the information seems...
I currently run a number of older "conventional PSU" Labgruppen amps, but having one bridged amp per driver is HEAVY!  Confused

(Finding amps for listening tests is somewhat hard in Sweden, as many of the MI shops carry only entry level stuff, like Phonic, Alesis etc.)

Normally one can find some general trends in opininons/reviews of stuff, but amps seem different? Strange, since they should actually have the smallest impact on overall fidelity of the rig, from a distorsion point of view.

Some praise the QSC RMX 4050 and 5050 for subs, while some claim their upgrade from RMX to some "switched" Crown, Lab or similar made a world of difference. Listening test (shootout) says the differences are small, but that test only included few speakers, etc...

Considering our ear's limited sensitivity to detect distorsion in the bass range, what IS it that we hear?

A guy I talked to described the lightweight Lab amps as "punchy" in the bass, but are we talking about that amp adding something that was not originally there? Or are many other amps missing the "punch", whatever that would be?

Power is clearly important, but amps that run below their clipping point should not colour sound at all, at least not detectable...

/Alexander


You have a NUMBER of CONVENTIONAL PS LABS??? And you are winging?? If they are too heavy SUCK IT UP  Laughing . You only have to lift them twice per gig is my take on it.

For my money, the reason labs and camco's get great raps is because they can do with switchmode what others can barely do with iron.

The reason that 'old' or heavy amps sound better for subs is because (very basically) there is more power in the reserve at any given time for the speaker to draw on for peaks etc. Sure all drivers draw on supplies extra for peaks, but subs REALLY draw for peaks so there needs to be more in the power reserve. (sorry if this was patronising, i didnt know if this is what you were asking.)

And yes sound differences are small. I have run rigs on all toroidal amps and rigs on all switchmode. It really doesnt matter until you get into the big games, but in my view anyone can buy gear, it is the small things that make the rig. Go to the gym more.

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Gene Hardage

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Re: Sound Is Subjective
« Reply #34 on: February 06, 2008, 07:13:39 am »

Richard Rajchel wrote on Tue, 05 February 2008 17:28

I'm not sure how well informed I might be, but the biggest impact on live sound is the talent of the musicians. The second biggest is probably the talent of the person mixing the band. As long as there's enough power to get the vocals over the sound of the band anyone should be able to get a listen-to-able mix......



YES and YES
The magic happens when the musicians and the sound person are on the same page and make an effort to stay within the limitations of the system and the room it's in.


Wish I could offer an answer to the original poster question.  I've always had to make do with whatever was in house or use my own limited resourses.
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Don Boomer

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Re: Sound Is Subjective
« Reply #35 on: February 06, 2008, 09:45:05 am »

Scott Smith wrote on Tue, 05 February 2008 18:19

has anybody offered any technical reasons why amps sound different


Yes ... as JR said amps sound different when  in the non linear mode.  What you are "hearing" is the amp clipping or limiting or running out of power supply, etc.

An amp should have no "sound" ... good or bad if we use the old standard ...striaght wire with gain.

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".  

WRT amps for subs I think a lot of listeners actually prefer some distortion in the system ... it "sounds better".  I'm fine with that I just think you have to define your standard when talking about amplifier "sound"

I don't think that the first practitioners of electric guitar were looking to sound like anything but an acoustic guitar only louder but look what it's turned into. I won't even start with mp3's. [ /bad analogy]

Seems like folks are out there selecting their power amps for "tone control"
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Bob Leonard

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #36 on: February 06, 2008, 10:02:20 am »

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.

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.
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Tim McCulloch

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #37 on: February 06, 2008, 10:58:18 am »

Another senseless "flat view" reply tragedy...

Bob, who the fuck are you replying to?

With love,

The not as old soundman.... Wink
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John Roberts {JR}

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #38 on: February 06, 2008, 11:33:31 am »

Bob Leonard wrote on Wed, 06 February 2008 09:02

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.

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.


I invite people to ignore any discussion of class C as it doesn't apply to audio amps, and rebuttal intended to inflame rather than illuminate. For a (very) basic overview here's a link to piece I wrote years ago while at my old gig.

http://www.peavey.com/support/technotes/poweramps/classact.c fm

Looking at the amps touted on page two you can date how old the white paper is, but the discussion is a good starting point for any wanting to understand amplifier classes.

JR
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Andy Peters

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #39 on: February 06, 2008, 01:08:14 pm »

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
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