Amp comparison by in room measurements. Advice? Conclusion?

[Blumlein 88]

The output impedances of the amplifier over the entire frequency range could provide an indication. A power cube measurement or a reactive load test could also provide further information.

It would, but if you measure the actual speaker in use, that will do.

 

[antcollinet]

Simply not possible to see differences between amps measuring in the audio domain. There are so many other variables that will swamp the tiny differences between amps - unless one is actually faulty, or being driven into clipping.

If you want to compare, you need to measure the electrical signal reaching the speaker.

 

[joqueval]

Interesting page where you can check the microphone curve

 

[GM3]

Interesting page where you can check the microphone curve

View attachment 330132

Which site is that image from? The Yeti has 4 modes, the image is for Omnidirectional, but "I was using cardiod which has apparently quite a bit bass roll-off starting at 200Hz as well as >4Khz... (bottom right)". If your site has a calibration file for Yeti that would be awesome!

There are so many other variables that will swamp the tiny differences between amps - unless one is actually faulty, or being driven into clipping.

Or is not fit to properly drive a specific speaker, given it sensitivity, impedance, etc., right? If that was the case, there might be more than "tiny differences" correct? Are you just assuming it's not or can't be the case?

so in this case it seems that you're trying to chase measurements to confirm what you thought you heard. That seems backwards to me.

If the methodology is valid and measurements demonstrate measurable (audible) differences... It's like you're against it in principle. Little bit like a priest telling a believer not to question his faith? I shouldn't question/measure/confirm my own beliefs?

In a simple case of two amps would its not be more useful to set up blind testing of the two amps to see if you can actually identify a difference between them that isn't biased?

For the V3 at least, we've already got a full suite of tests conducted here at ASR by Amir.

Actually imho; more trouble & less reliable. Measurements of Amir already demonstrated that the amp can sound different from other amps with different speakers, right?

https://www.audiosciencereview.com/forum/index.php?attachments/fosi-audio-v3-stereo-amplifier-budget-frequency-response-measurement-png.293699/

As I asked multiple times earlier, what happens with 3 Ohms or maybe even less less? (blocked ports)

Already, you have shown the QSC is not flat response in the low end.

When did I do that? And what do you mean by "QSC is not flat response in the low end"? I did mention <35Hz QSC will have less bass due to the roll off, but I think you're assuming that the V3 speaker output is perfectly flat, and because the QSC measurements are different the "QSC is not flat response in the low end"? (but yeah not flat = in room response = can't really be perfectly (perfectly) flat..)

 

[SIY]

Measurements of Amir already demonstrated that the amp can sound different from other amps with different speakers, right?

Only if you can pick up sub-1dB difference at 20kHz and can do a rapid (essentially instantaneous) switch.

If the methodology is valid

But as several people have pointed out, it likely isn't. The far more valid measurement (electrical at the speaker terminals) is actually a lot easier.

 

[GM3]

Only if you can pick up sub-1dB difference at 20kHz and can do a rapid (essentially instantaneous) switch.


But as several people have pointed out, it likely isn't. The far more valid measurement (electrical at the speaker terminals) is actually a lot easier.

What happens with 3 Ohms or maybe even less less? (blocked ports) Could it have an effect?

I do have a multimeter somewhere, so level match speakers at 1k, or measure watts with 1k tone, then do the same for 30, 40, 50, etc.? Yeah, that sounds like less trouble. I'll definitely try that

(sorry haven't had time to read in depth and respond to all!)

Oh yeah btw, someone asked, from my cell dB meter app, measurements were probably something like 75dB at for first 2, then 80-85dB. But, initially the app mentioned calibration file for the mic I think, which I didn't have (built-in mic), so I didn't want to put too much faith into it... But I guess it must still be fairly accurate in the end... shrug

 

[NoMoFoNo]

You're interested in testing but I would argue only to confirm your preconceptions. If you would take the time to blind test these amps, and see that you cannot reliably distinguish between them, you'd be much further along IMO. To each their own but I'm not convinced by what you've done to this point.

 

[SIY]

so level match speakers at 1k

That'll work and only take a few seconds. Because you're looking at frequency response, the level match only has to be approximate- a mismatch just shifts the curves up or down, it won't change their shape.

 

[pogo]

it won't change their shape

This is not correct and depends on the output impedance of the amplifier as well as the speaker impedance over the frequency range.

 

[joqueval]

Hello.
The page is this

Blue Microphones Yeti | RecordingHacks.com

Yeti, Multi-Pattern Condenser Stereo Microphone - detailed microphone profile, specifications, manuals, reviews, frequency-response graphs, self-noise data

recordinghacks.com

Behringer ECM8000 | RecordingHacks.com

ECM8000, Omnidirectional Condenser Microphone , aka: ECM-8000 - detailed microphone profile, specifications, manuals, reviews, frequency-response graphs, self-noise data

recordinghacks.com

You should use a measurement microphone, a basic one with a good price/performance ratio for gaming is the ECM8000.
Really take it as a game because using the Yeti will give you approximate results.
The ideal would be an ECM 8000 with an external sound interface, make a calibration file of the two devices and experiment with REW.
The QSC is a truck and the V3 is a car, so at load times the amplifier with more reserve power will get a better, more full-bodied sound.

 

[Blumlein 88]

When did I do that? And what do you mean by "QSC is not flat response in the low end"? I did mention <35Hz QSC will have less bass due to the roll off, but I think you're assuming that the V3 speaker output is perfectly flat, and because the QSC measurements are different the "QSC is not flat response in the low end"? (but yeah not flat = in room response = can't really be perfectly (perfectly) flat..)

Well you said the QSC had some protection or a roll off filter at 30 hz and lower. So that is what I was referring to in this case. Filters often have some effect well before the design point. So that might well be some difference to hear depending upon speakers and such.

(The QSC has 30Hz protection activate which rolls the bass, but apparently might be kicking it at ~35Hz, as QSC rolls off far quicker <35Hz)

 

[SIY]

This is not correct and depends on the output impedance of the amplifier as well as the speaker impedance over the frequency range.

It is correct unless an amplifier is pathological. This amplifier is not.

 

[antcollinet]

Or is not fit to properly drive a specific speaker, given it sensitivity, impedance, etc., right? If that was the case, there might be more than "tiny differences" correct? Are you just assuming it's not or can't be the case?

That is covered by my - "or being driven into clipping". If an amp is unable to drive a particular impedance dip of a speaker - it clips, or goes into protection which is even more drastic. Either way you are driving an amp outside it's power limits.

 

[pogo]

It is correct unless an amplifier is pathological. This amplifier is not.

Do we have the data for the speaker, the amplifiers, ...? Then we could do the math: Link

 

[SIY]

Then we could do the math

You might try that. Although you haven't bothered to before when you get on about your "damping factor" obsession, so probably won't this time, either.

 

[pogo]

Although you haven't bothered to before when you get on about your "damping factor" obsession

This is also incorrect: Link

 

[SIY]

This is also incorrect: Link

My apologies, you tried, I didn't see that. And screwed it up, as others pointed out.

Get a new obsession, this one is pretty tired.

 

[Cbdb2]

Waiting for the voltage at speaker measurements. Will answer all the questions.