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Author Topic: Subwoofer amps - what are we REALLY hearing?  (Read 31281 times)

Dan Bouchard

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #160 on: February 18, 2008, 08:10:13 am »

Duncan McLennan wrote on Tue, 05 February 2008 11:22

I've personally always like amplifiers with real toroidal transformers and linear power supplies.  Switching amps, although convenient for weight purposes, have never sounded as good to my ear.  That might be just me.

So is weight worth sacrificing sound quality?  I don't know.


I am 100% with you on this, nothing sounds as good as my Crest Pro9001, my 9200 come really close but its not the same animal
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John Roberts {JR}

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Re: Well, some companies display IM distorsion...
« Reply #161 on: February 18, 2008, 10:32:22 am »

Alexander B Larsson wrote on Mon, 18 February 2008 05:01

Ted Olausson said:
"There is also a numbergame with distortion, THD% is very inaudible but IM% is almost never stated but highly audible."

Well, Labgruppen and QSC certainly displays figures for IM distorsion, at least for the amp models I checked.
Coincidence?  Rolling Eyes

I DO find it interesting that many of the posters really liked the sound and reliability of the "old, continous power, 24/7" amps. Many of you have also clearly said that you ARE willing to compromise on the bass accuracy to get more power and lighter racks.

And I think nobody argues that the D class technology is still in need of more development, since the IM and load matching issues are still not really solved...

/Alexander


THD+N is kind of a kitchen sink measurement of all nonlinearity, noise, or deviation from straight wire with gain performance, IMD is a specific variant of distortion. Both can be audible depending on amount and masking capability of program material.  People are often confused about THD specifications and use of THD as a qualifier for power measurements (wrt clipping).

I expect class D to continue developing. It has some unique performance limitations but AFAIK IMD is not inherent to class D topology, and load interaction with output filters is a well understood engineering trade off to amp designers. I find it remarkable that modern class D amps with DSP on board don't apply that technology to mitigate the output filter losses (mostly simple freq response error).

JR

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Alexander B Larsson

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Re: Well, some companies display IM distorsion...
« Reply #162 on: February 18, 2008, 11:17:45 am »

Well John, I mean exactly what I wrote...  Very Happy
Apart from THD figures, Labgruppen and QSC also displays separate Intermodulation distorsion measurement figures, be it SMPTE or DIM 30.  Smile

Regarding the class D, was I mostly thinking of the inherent "coloration" in the higher frequencies, and the problems to get rid of that kind of topology related issues.
But the amps sure are light and use the supplied outlet power in a very efficient way - just what many here ask for!  Smile

/Alexander
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Duncan McLennan

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Re: Well, some companies display IM distorsion...
« Reply #163 on: February 18, 2008, 11:41:24 am »

Not all class D amps are light, only those with a switching power supply would be as light as something like a PLX.

I have a whole rack of Crest CD, which are class D and have toroidal transformers.  They're about 40lbs a piece, and sound pretty darn good.  They're extremely efficient.  500w/side at 4Ω and they draw something like 4A at 1/3 power.  I put four on a 20A circuit.

And they sound pretty darn good too.  I actually took one home, threw it in my stereo, and A/B'ed it with some of the good, and not s good hi-fi amps I've got lying around.  I also tested an old Microtech, and a Yorkville Audiopro, and a PLX.  I was surprised, the the Yorkville was the most 'musical' sounding of the whole lot.  The Microtech had tons of balls, but really no finesse.  The PLX sounded like a tin can, and the Crest-CD felt fairly well balanced compared to the rest.  Closest to the Yorkie in terms of tone.
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John Roberts {JR}

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Re: Well, some companies display IM distorsion...
« Reply #164 on: February 18, 2008, 04:11:30 pm »

Alexander B Larsson wrote on Mon, 18 February 2008 10:17

Well John, I mean exactly what I wrote...  Very Happy
Apart from THD figures, Labgruppen and QSC also displays separate Intermodulation distorsion measurement figures, be it SMPTE or DIM 30.  Smile

Regarding the class D, was I mostly thinking of the inherent "coloration" in the higher frequencies, and the problems to get rid of that kind of topology related issues.
But the amps sure are light and use the supplied outlet power in a very efficient way - just what many here ask for!  Smile

/Alexander


I was responding more to your comment

" And I think nobody argues that the D class technology is still in need of more development, since the IM and load matching issues are still not really solved...

/Alexander "


Class D technology has been around for decades and while anything can be refined, the primary developments these days is related to device technology. Higher voltage and current switching devices is what allows the formidable power output from newer class D amps.

A consequence of this higher output current is bigger/heavier output filters, which one recent model seems to have scrimped on to save size, or weight, or cost, or whatever.  I am not aware of any inherent  IM or load matching issues, while output impedance is a design consideration to be managed.

In light of the at least one model I mentioned it is prudent to look at top octave frequency response when driving low impedance HF drivers. Since this looks like a one pole LPF, corrective EQ should restore amplitude and phase response.

JR
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Bob Leonard

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Re: Sound Is Subjective
« Reply #165 on: February 18, 2008, 06:01:39 pm »

Andy Peters wrote on Sun, 17 February 2008 13:57

Ted Olausson wrote on Sun, 17 February 2008 06:50

(One of the amps is also very close to "2xpower" from DC to 80MHz and has perfect stepresponse, the other is a normal amp)


80 MEGAHERTZ?

Why does it need bandwidth out that far, if it's an audio amplifier?

-a


It won't and it can't. Well maybe, but it would be one hell of a circuit. Think of the possabilities. Audio through the RF spectrum with one amplifier. 80mhz is above most military radio frequencies. Look up BPL and tell me what you
find.
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John Roberts {JR}

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Re: Sound Is Subjective
« Reply #166 on: February 18, 2008, 06:32:46 pm »

Bob Leonard wrote on Mon, 18 February 2008 17:01

Andy Peters wrote on Sun, 17 February 2008 13:57

Ted Olausson wrote on Sun, 17 February 2008 06:50

(One of the amps is also very close to "2xpower" from DC to 80MHz and has perfect stepresponse, the other is a normal amp)


80 MEGAHERTZ?

Why does it need bandwidth out that far, if it's an audio amplifier?

-a


It won't and it can't. Well maybe, but it would be one hell of a circuit. Think of the possabilities. Audio through the RF spectrum with one amplifier. 80mhz is above most military radio frequencies. Look up BPL and tell me what you
find.


The name of the company escapes me now, but there was an amp company back in the late '70s or early '80s whose claim to fame was strip line (?)  technology and Mhz bandwidth, I doubt even they were pushing 80 Mhz power bandwidth but they were faster than your average Fender...

Needless to say there was no "there" there and they faded into oblivion. Something about "you can't fool all the people all the time..." (without a huge marketing budget).

JR

 
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Mac Kerr

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Re: Sound Is Subjective
« Reply #167 on: February 18, 2008, 06:41:19 pm »

John Roberts  {JR} wrote on Mon, 18 February 2008 18:32

The name of the company escapes me now, but there was an amp company back in the late '70s or early '80s whose claim to fame was strip line (?)  technology and Mhz bandwidth, I doubt even they were pushing 80 Mhz power bandwidth but they were faster than your average Fender...

Needless to say there was no "there" there and they faded into oblivion. Something about "you can't fool all the people all the time..." (without a huge marketing budget).
 
I don't know if it's what you were thinking of, but that was a claim to fame of Spectrasonics amps. The Spectrasonics 700 was a 70W amp on a card. You could load up to 8 of them in the card cage. they were very sensitive to wiring issues, I smoked a cage full of them when they went into ultrasonic oscillation because there was a grounding issue.

Mac
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Tim McCulloch

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #168 on: February 18, 2008, 06:42:01 pm »

Can we stick a fork in this thread?  It's done....

Tim Mc
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Mac Kerr

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Re: Subwoofer amps - what are we REALLY hearing?
« Reply #169 on: February 18, 2008, 06:43:32 pm »

Tim McCulloch wrote on Mon, 18 February 2008 18:42

Can we stick a fork in this thread?  It's done....

Tim Mc
It was done on day one.

Mac
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