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Old 18-07-2020, 11:54 AM   #1
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Proper measured example why amplifiers sound different

Good explanation and comparison of how electronic differences affect speakers' audio output significantly. Important thing is the proper measurements capturing both electronic and audio differences.

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Old 18-07-2020, 01:00 PM   #2
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Good explanation and comparison of how electronic differences affect speakers' audio output significantly. Important thing is the proper measurements capturing both electronic and audio differences.

Yes, this is very true esp. class AB amps. I have mentioned it, the key is the current. 4ohm speakers will need 2x the current of 8ohm speakers to drive. Thats where most of the lower end AVr struggle at. Some even mentioned in their manual that it cannot drive 4ohm speakers.
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Old 18-07-2020, 01:10 PM   #3
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But measurements alone isnt sufficient. Eg, for THD, tube amps have much higher THD compared to transistor one. But does this means they are bad sounding?? CDs are much better than vinyls when it comes to noise. But does that make vinyls bad??
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Old 18-07-2020, 01:45 PM   #4
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That is why for a lazy person like me who just wants to enjoy his Home Theatre Setup, I just recommend sites like Audio Science Review (ASR) and AudioHolics Reviews and call it a day.

Let them do the bulk of the heavywork. Then I can just pick and choose whichever speakers are the best objectively (and based on all their reviews nicely displayed in a very easy to read graph where I can easily click on any of them to get even more details and in-depth reviews if I wanted to) in that certain price range and Amplifier DACs too like whether they are using ESS Sabre, Hypex and whatnot and call it a day.

But if you have all the time in the world, for whatever reason, then by all means, pick your top 3 or 5 products based on those objective reviews. Go down to Adelphi's showrooms and see how those speakers look like and sound in real life.
Take note, there are many issues I have due to how the showrooms pair their setup;
like they have an overpowered Amp vs another shop using a weaker amp for the other speaker you have in mind
or they have room treatment while the other showroom lacks any
or their speakers are further apart than your home speaker layout and you can't do an objective A-B comparison since they don't have all your speakers right there for you to compare with. So you are basing the listening experience based on memory when you go to another showroom to have a listen.
So many issues... but by all means; It is perfectly fine to at least have the experience but do not consider that as a better way to test vs objective tests where the variables are as negligible as possible for consistency sake between 1 review and another.

But don't forget. Always prioritize Sound first. So those objective measurements are very very much appreciated.
Then you can choose whichever priority you want next.
Be it price
or the looks of the speakers so that it will suit your home setup.

Also, when looking for Amps or AVRs, take note what Room Correction software that they are using.
Yamaha's YPAO is meh. Audyssey MultEQ is acceptable. Audyssey XT32 is good. But if you want a cohesive experience, go for Amps or AVRs that have Dirac or REW.
Dirac for the lazy individuals like me who wants everything done automatically or REW for a more manual, hands on experience.
Room Correction software are the final key to your listening experience. It helps flatten out your speaker's flaws via software EQ as much as possible based on your main listening position.
And REW and Dirac with its added features like time alignment correction made all the speakers disappear as they are all playing the audio in tandem. It really feels like the speakers are not even there. Because the speakers are now as flat as possible along with being time aligned to your listening seat. It is very cohesive. So you no longer hear sounds coming from speakers, but more like sound coming from a location in space.
It really is immersive.
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Old 18-07-2020, 01:50 PM   #5
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Great advice for noobs! Thumbs up!

Like I said before, I dream of the day affordable speakers are so technically good they can EQ / DSP to simulate any sound signature, be it tube sound, vinyl sound or whatever u like/need with easy to use presets.

Last edited by benedium; 18-07-2020 at 02:00 PM..
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Old 18-07-2020, 02:08 PM   #6
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Tripath designs were well known for that frequency change vs load impedance probably in part due to many people owning them because they are cheap. But yea that used to be a common issue with class D.

However as you can see nowadays the better class-D amps don't have this issue. It is due to a poorly-designed output filter anyway.

Anyway as you probably already know from this thread this is mainly due to output impedance and hence the effect on FR can be caltulated, the knowledge of which is starting to be spread amongst headphone people. The impedance from an LC filter is reactive, hence ringing in the frequency domain can occur.

Also from the curve below you can see why speaker impedance rating is kinda bs because the impedance of KEF R3 is only 5ohm at 10kHz and above, where output filter issues occur. What's even worse is that, in the bass regions where average amplitude is the highest (Just do a frequency response plot of your favorite song in audacity), the impedance is 3.2ohm, lol.

Spoiler!
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Old 18-07-2020, 02:23 PM   #7
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Tripath designs were well known for that frequency change vs load impedance probably in part due to many people owning them because they are cheap. But yea that used to be a common issue with class D.

However as you can see nowadays the better class-D amps don't have this issue. It is due to a poorly-designed output filter anyway.

Also from the curve below you can see why speaker impedance rating is kinda bs because the impedance of KEF R3 is only 5ohm at 10kHz and above, where output filter issues occur. What's even worse is that, in the bass regions where average amplitude is the highest (Just do a frequency response plot of your favorite song in audacity), the impedance is 3.2ohm, lol.

Spoiler!
Which begs the next question: Why are certain speakers, or woofer drivers, designed with such low impedance?

Is it because it's cheaper to build (manufacturing reasons)?
Is it because it allows the speaker to go louder (audio performance reasons)?
Or are they trying to make people buy more powerful amps (business / branding / strategic reasons)?
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Old 18-07-2020, 02:47 PM   #8
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I always thought the variations resulting in a not-flat response are due to luck.

Well I'm not a speaker designer.

Driver impedance comes from
-voice coil resistance (i.e. impedance @ DC and <10Hz)
-the inductance (i.e. the slowly-increasing impedance at >20kHz)
-the system resonant frequency i.e. where the impedance of your resonant circuit is the greatest, showing up as a spike in impedance.



And then it gets very complicated when two drivers + a 7-component crossover are added together
I mean u notice that the impedance in the R3 actually goes below the DC resistance at 40Hz and 150Hz.

For me, as long as the resulting sound is flat, I dun care. I'm not a speaker designer.

As for the not-flat part of the question: Driver manufacturers do sell different versions of the same driver: 8ohm version, 4ohm version, even 2ohm and 16ohm versions. As home audio consumers we should get 8ohm because that is the current meta. But cars would go for 2ohm. It depends on the application.

And to achieve these differences is simple: Force depends on amount of current. You can have one round of thick wire or two rounds of thinner wire. The two rounds of thinner wire would have 4 times the impedance.
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Last edited by wwenze; 18-07-2020 at 02:50 PM..
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Old 18-07-2020, 03:05 PM   #9
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Tripath designs were well known for that frequency change vs load impedance probably in part due to many people owning them because they are cheap. But yea that used to be a common issue with class D.

However as you can see nowadays the better class-D amps don't have this issue. It is due to a poorly-designed output filter anyway.

Anyway as you probably already know from this thread this is mainly due to output impedance and hence the effect on FR can be caltulated, the knowledge of which is starting to be spread amongst headphone people. The impedance from an LC filter is reactive, hence ringing in the frequency domain can occur.

Also from the curve below you can see why speaker impedance rating is kinda bs because the impedance of KEF R3 is only 5ohm at 10kHz and above, where output filter issues occur. What's even worse is that, in the bass regions where average amplitude is the highest (Just do a frequency response plot of your favorite song in audacity), the impedance is 3.2ohm, lol.

Spoiler!
wow 3ohms!!!
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Old 19-07-2020, 08:04 AM   #10
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That is why for a lazy person like me who just wants to enjoy his Home Theatre Setup, I just recommend sites like Audio Science Review (ASR) and AudioHolics Reviews and call it a day.

Let them do the bulk of the heavywork. Then I can just pick and choose whichever speakers are the best objectively (and based on all their reviews nicely displayed in a very easy to read graph where I can easily click on any of them to get even more details and in-depth reviews if I wanted to) in that certain price range and Amplifier DACs too like whether they are using ESS Sabre, Hypex and whatnot and call it a day.

......
Also, when looking for Amps or AVRs, take note what Room Correction software that they are using.
Yamaha's YPAO is meh. Audyssey MultEQ is acceptable. Audyssey XT32 is good. But if you want a cohesive experience, go for Amps or AVRs that have Dirac or REW.
Dirac for the lazy individuals like me who wants everything done automatically or REW for a more manual, hands on experience.
Room Correction software are the final key to your listening experience. It helps flatten out your speaker's flaws via software EQ as much as possible based on your main listening position.
And REW and Dirac with its added features like time alignment correction made all the speakers disappear as they are all playing the audio in tandem. It really feels like the speakers are not even there. Because the speakers are now as flat as possible along with being time aligned to your listening seat. It is very cohesive. So you no longer hear sounds coming from speakers, but more like sound coming from a location in space.
It really is immersive.
Ya. I buy all my stuff googling on user reviews.
So this “sound response flat”, been spotting this description in audio stuff.
Thus by achieving that, we can achieve this effect of the sound not directly coming from a localised spot but from a large staging?


Also from the curve below you can see why speaker impedance rating is kinda bs because the impedance of KEF R3 is only 5ohm at 10kHz and above, where output filter issues occur. What's even worse is that, in the bass regions where average amplitude is the highest (Just do a frequency response plot of your favorite song in audacity), the impedance is 3.2ohm, lol.

Spoiler!
We set the crossover at 80Hz, then the avr will not need to drive spk at 3.2ohms.
So regular avr should be able to drive the spks.
So the issue only occur if there is no sub, and the user need to buy an amp that can go to 3ohms?
Is my understanding correct?
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Old 19-07-2020, 08:14 AM   #11
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You don't need to "buy an amp that can go to 3ohms". Go and connect two speakers in parallel so you get less ohms than that. Did your amp explode? No? This proves that your amp can go to 3ohms.

All amps have a max limit on output current and output voltage. It can output anything below this limit. Load impedance decides the ratio of current and voltage.

Operating at max current & max voltage at the same time produces the max power, which only happens at 1 specific load impedance.
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Old 19-07-2020, 11:13 AM   #12
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You don't need to "buy an amp that can go to 3ohms". Go and connect two speakers in parallel so you get less ohms than that. Did your amp explode? No? This proves that your amp can go to 3ohms.

All amps have a max limit on output current and output voltage. It can output anything below this limit. Load impedance decides the ratio of current and voltage.

Operating at max current & max voltage at the same time produces the max power, which only happens at 1 specific load impedance.
So meaning if the spk are rated 8ohms, it doesn’t really matter at what freq, the impedance will vary? Just need to get the amp that has enough power rated for the rated impedance will do?
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Old 19-07-2020, 02:40 PM   #13
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Just get enough power = enough voltage + enough current and you're fine even if your speakers have low impedance.

A speaker with minimum impedance 3ohm doesn't mean it will draw as much current as a resistor of 3ohm. It's the average that matters. Consider a speaker with impedance 3 ohm @ 100Hz and 5 ohm @ 1kHz. And you play a signal that is 1V @ 100Hz + 1V @ 1kHz. Current will be 1/3A @ 100Hz + 1/5A @ 1kHz = ~0.53A total. If I swapped it with a 4ohm resistor, the current is 0.5A
i.e. It's average impedance that matters

Of course when we start doing more math then we can see if that average or rated impedance is appropriate or not. For example we consider most music content has more bass than treble. The impedance at a specific frequency also starts to matter when you want to do things at that specific frequency e.g. bass boost when impedance at bass is low
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Old 19-07-2020, 03:23 PM   #14
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I'm just guessing... but does manufacturer indicated nominal impedance, like 6ohm or 8ohm, indicate the impedances encountered by the speaker for the majority of sounds?

So if manufacturer states 4ohm means majority of sounds will be at around 4 ohm. It all depends on the speaker's design?

So does an 8ohm nominal impedance speaker mean it can be powered by a majority of low powered amps and avr? 6ohm for mid range to high end like at least 60/80w amp, 4ohm for only high end high power amps like 150w to 200w?

I plucked these numbers from air because remembered reading ASR saying elac debut reference dbr62 needs 80w per channel amp to perform optimally and its nominal impedance is 6 ohm.

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Old 19-07-2020, 04:09 PM   #15
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I'm just guessing... but does manufacturer indicated nominal impedance, like 6ohm or 8ohm, indicate the impedances encountered by the speaker for the majority of sounds?

So if manufacturer states 4ohm means majority of sounds will be at around 4 ohm. It all depends on the speaker's design?

So does an 8ohm nominal impedance speaker mean it can be powered by a majority of low powered amps and avr? 6ohm for mid range to high end like at least 60/80w amp, 4ohm for only high end high power amps like 150w to 200w?
Yes, the value stated by manufacturer is the nominal impedance.

I can safely say all amps in the market can power 6/8ohm speakers. 8ohm is the most common impedance for speakers, esp. for budget models. So, amp companys will ensure their budget amps can drive 8ohms speakers. Speaker companies will also ensure their budget speakers can run on these amps.

Btw, sensitivity also plays a big role. Even if the impedance is 8ohm, if the sensitivity is low, then not all amps can drive it properly.

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