Do Amplifiers "color" sound? - Page 8 - Home Theater Forum and Systems -

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post #71 of 98 Old 11-07-12, 10:29 PM
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Speakers were Focal Maestro Utopia.

Assumption that the mic was in the same position is correct.
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post #72 of 98 Old 11-07-12, 10:38 PM
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It was only the third time using the measurement system during the recording, hence the curves weren't saved the best way possible. But you can try placing them above each other from power point, copy the image and superimpose them above the other, and increase the transparency. You'll see the curve generally takes the same shape, because room, speakers and system are not touched, just amps. The differences would be amplifiers then.

Since then, I've measured a couple of rooms, and have learnt how to save graphs properly for direct comparisons. The measurements have helped me design acoustics, and translate audio opinions to curves and associate frequency ranges more accurately.

I had the rare opportunity of sitting in with 4 amps in a semi blind shoot out. The measurement tool would have been so useful-if only I had them then.

We'll have better graphs in future. ")
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post #73 of 98 Old 11-07-12, 10:45 PM
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AudiocRaver wrote: View Post
A good point has been made - we tend to think of power amplifier nonlinearities occurring mainly at or close to the clipping level, but there can be speaker & environmental factors that coax different nonlinearities out of different amps even at levels way below clipping.

One assumption of this discussion has been that in "properly designed" amplifiers all these below-clipping nonlinearities have been ironed out and made equal, but perhaps that is not always the case. Perhaps it is not even possible.

I'm reminded of an early engineering job with an audio manufacturer, now long gone, where our chief circuit designer had a major challenge convincing the bosses that Transient Intermodulation Distortion even EXISTED. He finally ended up designing a circuit with good "standard" bench specs and grossly exaggerated TIM with the right signal/program material, and let their own ears do the convincing, which led to a new family of designs for that company. Knowing what to look for, new bench measurements were implemented so we could measure slew rate and test for the causes of TIM directly, and we all ended up a bit smarter about how an amplifier can sound and how to design circuitry that measured well and sounded good, too.

That said, we've come a long way, and absent a true double-blind, volume-compensated, quick-switch test setup with the amplifier the only variable, I still tend to believe that amplifiers intended to have flat response and little-to-no distortion and equivalent damping factors and running well below clipping - will sound the same. And if they don't, one of them needs some more drawing-board time. Probably. I would truly appreciate the opportunity to participate in a well-thought-out demo that shows otherwise. I am teachable. A little.
I think some amps have similar characteristics-just at different degrees. But those that sound exactly the same, I've not heard.

Could you point me to models that I could maybe put together to audition them? Based on your personal experience, you may be right, but I would like to hear it for myself, if they are within my means.

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post #74 of 98 Old 11-07-12, 11:49 PM
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Re: Do Amplifiers "color" sound?


are you claiming that the Emotiva XPa-1's are not flat?

If so, care to explain these independent review and measurement results? They're certainly easier to read than your smoothed out graphs with 20db spacing.

Of course, the graphs in the link are pure input-output measurements, unlike room measurements where who knows what the rest of the equipment chain is doing. The ability to isolate the results to a specific component makes reviewing the results a lot easier.

As I mentioned in previous posts, sure, one could take a bright sounding speaker with a boost in the treble, and then mate it with an amplifier that rolls off the highs, but why do that? It simply makes more sense to choose an entire equipment chain that is flat. Speakers that play flat, amps that do not alter the frequency response of the signal, cables that don't attenuate certain frequencies to produce a specific 'cable sound' etc.

With flat equipment, you can place it in any room, then measure it and see what needs correction in the room. With equipment that is all over the board, sure you need this amp for that speaker because you need the distortions of one to cover the distortions of the other. Amps shouldn't be tone controls, neither should cables, interconnects or any of these other pieces of equipment.

To sum up my position, the original question in the thread title has a simple answer:

Do Amplifiers "color" sound? Not if they're designed and built properly.

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post #75 of 98 Old 11-08-12, 12:15 AM
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Re: Do Amplifiers "color" sound?

MagnusAtom wrote: View Post
If you feel the speakers are too brilliant, but love the depth it has, the common approach is to use a tube.
being a common approach does not make it a sensible approach. If you feel the speakers are too "brilliant" then they were the wrong speaker in the first place for you.

Or you like tight bass, and love the effect big woofers have, look for a high powered amplifier with a high damping factor, which will typically tighten the bass - neat, big woofer with deep bass, and great tight control with the amplifier
Any moderately decent damping factor (an "inverse word" for low measured output impedance) will not affect the sound. Further, unless you know explicitly the speaker's impedance curve in frequencies above the bass, using any amplifier with a sufficiently high output impedance is just a bad move anyways. Why would one make a move which is clearly not sensible?

Impedance changes can be a big factor for some amps with some speakers. Some amps do well with impendece varying from 0.1 ohms to 15 ohms in pne speakers. some do not.
Obviously there's a bare minumum of bad design which is unacceptable. This starts at the speaker of course - if the speaker's impedance curve is needlessly difficult, than that's a speaker design issue. If the amp can't drive a moderate load, then upgrading amps is not a "bonus" as you imply but a necessity and should have been done from the very beginning.

My understanding of your earlier implication was that once good sound has been achieved - it can surely be improved by upgrading electronics. I disagree based on my experiences. My basic assumption is that the amplification is adequate with respect to the loudspeaker load and headroom. If the speaker requires some extreme amplification, then clearly there is a speaker issue. If the speaker already sounds great, then electronics will not make a meaningful difference because they are literally 5% of the sound - which gets masked by the speaker and the room. Even if a preamp has 0.0001% distortion instead of 0.003% distortion for example - it won't matter - it will all be masked by the speaker's .1 to 3% distortion. It's not that once you've sorted things out, then the electronics can only improve things - but rather that once you've sorted out the speakers and room, you've sorted out the sound.

Trust me, I understand that electronics aren't perfect. For example, whereas a speaker's distortion will only drop as SPL demands drop, many class AB amplifiers will have a rising distortion as voltages drop.

But this does not automatically mean it will be audible, either. A 5th harmonic at -50db (which is 1% distortion and higher order too!) sounds bad... except for one thing. If your SPL is 40dbSPL, then that means that 5th harmonic is at.. 10dbSPL.

There are a lot of measurable issues in electronics. But that does not mean they are audible, so chasing that goal does not mean that anyone looking for the best possible sound needs to chase great electronics.

Also the damping factor can make a real difference with some speakers in some rooms.
But do you have empirical evidence of this in an anechoic space before we even mention the room?

Even besides that, all rooms have a vast masking effect on system effects. So if the above case were true (that the damping factor makes a difference anechoically) it would still be subject to the effect of the room below the shroeder frequency. This will absolutely mask this already minor abboration at system resonance.

Listening can discern these effects to lead youvtovbest matches between speaker and amp.
Blind, 0.1db level-matched listening? Or does it need to be sighted, random level listening?

Don't underestimate us! Whether it be time, space, or alternate realities, they mean nothing to us! We will pierce the path and methods you've chosen! That is who we are!

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post #76 of 98 Old 11-08-12, 12:53 AM
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I was just stating- I do think we need the speakers to perform best on/off axis, 30-60. No speaker does this perfectly. But there are speakers that look real good on charts off the anechoic chamber.

So it doesn't matter how accurate your set is on the bench until it is put into the room, and measured. It does point us in the right direction though. It really depends what people do with what they've got and the degree of fidelity they are content with.

So match the speaker with the room if you're being technical. Otherwise match the room to the speaker. No right or wrong approach, as long as the sound is accurate at the final measurement.

Amps have different sounds, we just don't know which is the flattest/quietest at all frequencies, and one that manages all resistance the best. And know them truly. There is no one-body within the audio industry that is an authority enough to certify these things.

On another thought, perhaps bi-amping would be best, because lower frequencies seem to vary most in resistance, and requires good solid amps to keep pace.
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post #77 of 98 Old 11-08-12, 01:00 AM
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The graph indicates any changes in frequency response. I did not do it with the intention to point out any scientific proofs. But it does show varying frequencies between the set ups, with only variable being the amplifiers.
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post #78 of 98 Old 11-08-12, 07:26 AM
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Re: Do Amplifiers "color" sound?

Lessons learned from this most excellent post.

If you believe that amplifiers color the sound then YES they do and ways will be found to theoretically prove that belief.

If you do not believe that amplifiers color the sound then NO, they do not and ways will be found to theoretically prove that belief.

There, that sums it up. This appears to be a very personal issue.

Good Listening


"For those who believe no proof is needed for those who don't believe no proof is possible"
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post #79 of 98 Old 11-08-12, 07:54 AM
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Re: Do Amplifiers "color" sound?

Given the speakers (and if I understand one of those amps was an Emotiva); therre likely is coloration. The Focal Maestro Utopia is a 3ohm speaker (per Focal: the Stereophile measurement spends real time at 2ohm), and Emotivas are only rated down to 4.

From Stereophile: As taxing as this will be for an amplifier, there are combinations of 3.75 ohms and –37 phase angle and 2.3 ohms and +40 at 62Hz and 126Hz, respectively, which will also demand very high currents from the amplifier. As all music has considerable energy in this region, the Focal's owner will have to use an amplifier that can genuinely deliver high powers into 2 ohms if the speaker is to be allowed to sing as it should. Even then, as I found with the otherwise superb Simaudio W-7 amplifier, the high phase angle at infrasonic frequencies may well cause the amplifier to go into protection with a wideband pulse as it encounters what appears to be a short circuit on its output.

I have the same issue with my B&W 801N's. That's why I don't run them on Emotiva (I can hear problems).

Though if we go back to my "two kinds of amps: sufficient and insufficient" position; I'd assert that an Emo is "insufficient" for loads <4ohm.

We'd want to compare certain models of Krell, McIntosh, Parasound, and perhaps Crown (all of which have 2Ohm amp models) if using those speakers.

I thank you very much for putting up the graphs and taking the time: but I'm afraid (unless I misunderstand what amps you were using) you have supported what we already agreed on: insufficient amps color sound.

Last edited by JerryLove; 11-08-12 at 08:27 AM.
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post #80 of 98 Old 11-08-12, 08:13 AM
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Re: Do Amplifiers "color" sound?

One other thing to add to the equation is that I have the same sub in my room and if I take a different frequency response chart even throughout the day, they will look different. That is why the anechoic chamber is the best way.
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