ATI (Amplifier Technologies) Owners Thread

[Sly]

He might also be a little more prone to "bias of all sorts" than others.

Yeah his reaction wasn't very conclusive.
Though ati suggest 7 days of playing music to break it in lol. Never noticed speaker break in let alone amps.
Yep refrence 1, wasn't to sure of the power needed hence me asking, they look difficult but sure those amps would have decent current, don't perticually want to go overboard as they end up expensive n really heavy.
My fault for settling on a/b me thinks lol.

 

[PENG]

Though ati suggest 7 days of playing music to break it in lol. Never noticed speaker break in let alone amps.

Dr. Floyd Toole put it well in saying something like "It's the ears that got broken in", not the speakers, or electronic gear I guess..

Yep refrence 1, wasn't to sure of the power needed hence me asking, they look difficult but sure those amps would have decent current, don't perticually want to go overboard as they end up expensive n really heavy.
My fault for settling on a/b me thinks lol.

In my opinion, your choice of going with amps rated 200 W 8 ohms, 300 W 4 ohms is about right for the Reference 1. When manufacturers say 50-200 W, you know it is better to go with 200 W, so peak would be 400 W, and that should get you the best out of those speakers, in terms of satisfying their voltage/current need, more may be better, say up to 400 W 4 ohms capable amps. There are good information in the linked review, but that's for the Reference 1 Meta, the non Meta version will be different but I am sure they would be similar enough in terms of current requirements.

Kef Reference 1 Meta Bookshelf Speaker Review

From the measurements, you can see that the Ref.1's loves currents, and it has rather low EPDR (a misleading spec, that says more about heat dissipation, than currents). That, from my understanding, you may be better off using class D amps such as the popular Hypex or Purifi modules based power amps. Class D amps seem less prone to low EPDR than class AB amps that would have to dissipate lots of heat in the output devices, but obviously the ATI signatures should be good with that too.

 

[Sly]

Dr. Floyd Toole put it well in saying something like "It's the ears that got broken in", not the speakers, or electronic gear I guess..




In my opinion, your choice of going with amps rated 200 W 8 ohms, 300 W 4 ohms is about right for the Reference 1. When manufacturers say 50-200 W, you know it is better to go with 200 W, so peak would be 400 W, and that should get you the best out of those speakers, in terms of satisfying their voltage/current need, more may be better, say up to 400 W 4 ohms capable amps. There are good information in the linked review, but that's for the Reference 1 Meta, the non Meta version will be different but I am sure they would be similar enough in terms of current requirements.

Kef Reference 1 Meta Bookshelf Speaker Review

From the measurements, you can see that the Ref.1's loves currents, and it has rather low EPDR (a misleading spec, that says more about heat dissipation, than currents). That, from my understanding, you may be better off using class D amps such as the popular Hypex or Purifi modules based power amps. Class D amps seem less prone to low EPDR than class AB amps that would have to dissipate lots of heat in the output devices, but obviously the ATI signatures should be good with that too.

View attachment 74317

Was definitely my brain getting used to the arendals, took about a week, but i could tell how used i'd got to my q accoustics which had an extended treble so you could hear "detail", once i figured it was boosted i was determined to give more time n patience to my next speakers. I'd tried out at least 12 other speakers.
Its funny you mentioning that class d might be better, reading through Rich.b's thoughts and the thread about the ati class d, and having second thoughts about it.
Have been under the impression though that the added simbilance might not to my taste, leaness (which could be eq'ed out - so should'nt be concern) maybe worrying about it to much but don't want to make an exspensive mistake.
Thought 400w@4ohm would be best though, you confirmed my lingering concerns.

 

[PENG]

Was definitely my brain getting used to the arendals, took about a week, but i could tell how used i'd got to my q accoustics which had an extended treble so you could hear "detail", once i figured it was boosted i was determined to give more time n patience to my next speakers. I'd tried out at least 12 other speakers.
Its funny you mentioning that class d might be better, reading through Rich.b's thoughts and the thread about the ati class d, and having second thoughts about it.
Have been under the impression though that the added simbilance might not to my taste, leaness (which could be eq'ed out - so should'nt be concern) maybe worrying about it to much but don't want to make an exspensive mistake.
Thought 400w@4ohm would be best though, you confirmed my lingering concerns.

My concern with class AB amp for your speaker is in the range between 45-1000 Hz, where EPDR dips to around 2 ohms. There are tons of contents in music/movies in that range, so some class AB amps may struggle. In terms of current, lower EPDR than the impedance does not increase current, but could result in a lot more heat in the output devices so not a good idea.

This is a good example of using power, that is watts, is not the best way, as for people who are not familiar with EE principles may not realize that if an amp is rated say, 100 W 8 ohms, if that rating is limited by the rated current, then it is current limited at current = square root (100/8) = 3.53 A, then into 2 ohms, the "power" is only 3.53^2*2 = 24.92 W, that's not a whole lot! It is a reverse double down thing, so 100 W 8 ohms, 50 W 4 ohms, 25 W 2 ohms.

Simple math yet can confuse people right!

That's why I always want to calculate voltage and current requirement, not "power". Rule of thumb is, for higher impedance, voltage is more important and for lower impedance, current is, but that's just rule of thumb, there's always something in between, though the Ref 1, in the bass and midrange, it is current that they need, the tweeter do want voltage but it peaks at 16 ohm, that's not a concern.

As far as your concern about sibilance, lean, warm etc., I don't believe those things are due to power amps in the calibre of those you are looking at, if someone says they could hear the difference between ATI's class D and AB, I just smile, knowing full well, with confidence that they would not hear the claimed differences in a well controlled DBT, I respect enthusiasts like Richb, but I always just though they could imagine things better than I lol... I know people would say even their cats notice the difference when they change their amp, what can I say....sorry I digressed, should have just stick to EE principle and shut up on the rest.

 

[TLS Guy]

My concern with class AB amp for your speaker is in the range between 45-1000 Hz, where EPDR dips to around 2 ohms. There are tons of contents in music/movies in that range, so some class AB amps may struggle. In terms of current, lower EPDR than the impedance does not increase current, but could result in a lot more heat in the output devices so not a good idea.

This is a good example of using power, that is watts, is not the best way, as for people who are not familiar with EE principles may not realize that if an amp is rated say, 100 W 8 ohms, if that rating is limited by the rated current, then it is current limited at current = square root (100/8) = 3.53 A, then into 2 ohms, the "power" is only 3.53^2*2 = 24.92 W, that's not a whole lot! It is a reverse double down thing, so 100 W 8 ohms, 50 W 4 ohms, 25 W 2 ohms.

Simple math yet can confuse people right!

That's why I always want to calculate voltage and current requirement, not "power". Rule of thumb is, for higher impedance, voltage is more important and for lower impedance, current is, but that's just rule of thumb, there's always something in between, though the Ref 1, in the bass and midrange, it is current that they need, the tweeter do want voltage but it peaks at 16 ohm, that's not a concern.

As far as your concern about sibilance, lean, warm etc., I don't believe those things are due to power amps in the calibre of those you are looking at, if someone says they could hear the difference between ATI's class D and AB, I just smile, knowing full well, with confidence that they would not hear the claimed differences in a well controlled DBT, I respect enthusiasts like Richb, but I always just though they could imagine things better than I lol... I know people would say even their cats notice the difference when they change their amp, what can I say....sorry I digressed, should have just stick to EE principle and shut up on the rest.

It must have taken real work to deign a three way bookshelf speaker with an impedance curve like that. It is totally unnecessary apart from being design malpractice.

 

[highfigh]

Dr. Floyd Toole put it well in saying something like "It's the ears that got broken in", not the speakers, or electronic gear I guess..




In my opinion, your choice of going with amps rated 200 W 8 ohms, 300 W 4 ohms is about right for the Reference 1. When manufacturers say 50-200 W, you know it is better to go with 200 W, so peak would be 400 W, and that should get you the best out of those speakers, in terms of satisfying their voltage/current need, more may be better, say up to 400 W 4 ohms capable amps. There are good information in the linked review, but that's for the Reference 1 Meta, the non Meta version will be different but I am sure they would be similar enough in terms of current requirements.

Kef Reference 1 Meta Bookshelf Speaker Review

From the measurements, you can see that the Ref.1's loves currents, and it has rather low EPDR (a misleading spec, that says more about heat dissipation, than currents). That, from my understanding, you may be better off using class D amps such as the popular Hypex or Purifi modules based power amps. Class D amps seem less prone to low EPDR than class AB amps that would have to dissipate lots of heat in the output devices, but obviously the ATI signatures should be good with that too.

View attachment 74317

I think I would add 'mind' to the quote about ears breaking in- bias comes from the mind and the interface allows us to smooth out differences in sensed experiences. Then, we get to deal with the conflict that comes from "This can't possibly sound this good- it's not expensive, big, etc" due to education and preconceived notions. If a speaker produces killer bass and it's tiny, I think a lot of people will make sounds like a confused Scooby Doo.

 

[highfigh]

It must have taken real work to deign a three way bookshelf speaker with an impedance curve like that. It is totally unnecessary apart from being design malpractice.

Looks like they fixated on the frequency response and ignored the impedance.

 

[Sly]

My concern with class AB amp for your speaker is in the range between 45-1000 Hz, where EPDR dips to around 2 ohms. There are tons of contents in music/movies in that range, so some class AB amps may struggle. In terms of current, lower EPDR than the impedance does not increase current, but could result in a lot more heat in the output devices so not a good idea.

This is a good example of using power, that is watts, is not the best way, as for people who are not familiar with EE principles may not realize that if an amp is rated say, 100 W 8 ohms, if that rating is limited by the rated current, then it is current limited at current = square root (100/8) = 3.53 A, then into 2 ohms, the "power" is only 3.53^2*2 = 24.92 W, that's not a whole lot! It is a reverse double down thing, so 100 W 8 ohms, 50 W 4 ohms, 25 W 2 ohms.

Simple math yet can confuse people right!

That's why I always want to calculate voltage and current requirement, not "power". Rule of thumb is, for higher impedance, voltage is more important and for lower impedance, current is, but that's just rule of thumb, there's always something in between, though the Ref 1, in the bass and midrange, it is current that they need, the tweeter do want voltage but it peaks at 16 ohm, that's not a concern.

As far as your concern about sibilance, lean, warm etc., I don't believe those things are due to power amps in the calibre of those you are looking at, if someone says they could hear the difference between ATI's class D and AB, I just smile, knowing full well, with confidence that they would not hear the claimed differences in a well controlled DBT, I respect enthusiasts like Richb, but I always just though they could imagine things better than I lol... I know people would say even their cats notice the difference when they change their amp, what can I say....sorry I digressed, should have just stick to EE principle and shut up on the rest.

Thats actually some important info to have regarding what amp i should be looking out for. Going to have to swot up on the ee principles a bit, although i might be at a stretch to call it simple maths lol.
So really i should concentrate on currant rather than just power as a whole which in hindsight is a bit presumtous of the process.
Im leaning more towards ati's class d, although like you say cooling on those amps as a whole is quite good, but with the added perks of class d it weighs up favourably especially for this speaker.
Will have another good look although these companies can be very selective with the stats.
Thankyou again, you've been very helpful.

 

[Sly]

Looks like they fixated on the frequency response and ignored the impedance.

Tried to email them about it but seems impossible from a phone, won't scroll sideways.
Unless theres a simplified phone version, which i can't seem to access.

 

[PENG]

So really i should concentrate on currant rather than just power as a whole which in hindsight is a bit presumtous of the process.

You have very nice speakers, but it is a fact that their impedance/phase angle vs frequency curves are evident that supports they are not just so called hard to drive, but are in fact hard to drive, relatively speaking. That said, it is still important to consider the key factors that include listening habit and seating distance, as if those two conditions are "right", even a midrange AVR can do the job, if not, then amps rated 300 W/500 W 8/4 ohms such as the Hypex NC502MP, or ATI6000 or AT54XNC series. Great speakers deserve great amps!

 

[PENG]

It must have taken real work to deign a three way bookshelf speaker with an impedance curve like that. It is totally unnecessary apart from being design malpractice.

Agreed to a point only, because KEF probably considers impedance curves for their $7,500 a pair bookshelf speakers are not going to be a concern for their potential buyers who likely wouldn't mind spending at least $2,000 on a 200-300W/500W 8/4 ohm rated power amps. For those amps, they really don't care much about the impedance curves, again, for just bookshelf speakers.

 

[Sly]

You have very nice speakers, but it is a fact that their impedance/phase angle vs frequency curves are evident that supports they are not just so called hard to drive, but are in fact hard to drive, relatively speaking. That said, it is still important to consider the key factors that include listening habit and seating distance, as if those two conditions are "right", even a midrange AVR can do the job, if not, then amps rated 300 W/500 W 8/4 ohms such as the Hypex NC502MP, or ATI6000 series. Great speakers deserve great amps!

Will have, was going to buy straight the way but decided on avm90 (and better rc) and amp first hence me asking what amp would suit them.
Knew they were difficult but did'nt consider other factors like voltage/current and how low indepedence speakers react, especially when they have low curves like that.
Speakers will only be about 7ft away and listening is 75db avg.
Using a yamaha a8 at the mo, and gene measured the a6 at 150wx2, so there was some power but had huge doubts trying to power anything hard to drive, ie these.

 

[PENG]

Will have, was going to buy straight the way but decided on avm90

Decided on, or pull the trigger already? The AVM90 is nice, but if for better RC, I would have picked the AV20 and spend the $ on DLBC, though it is subjective to some extent.

 

[Sly]

Decided on, or pull the trigger already? The AVM90 is nice, but if for better RC, I would have picked the AV20 and spend the $ on DLBC, though it is subjective to some extent.

Heard the r3's, liked them a lot just wished certain aspects were better, one thing being dynamics, felt the r3 was a bit to flat. Not to say they were boring, just wanted more from them. Which was probably the intention.
Was picking between the avm90 and av10, went through the diffrences/rc's and anything i could find, prefered arc (considering ive never used rc besides ypao before, or even used/owned a laptop) and fitted a bit more as im not really a tinkerer.
The only thing that appealed was better reliability on the av10, but hopefully most bugs are ironed out on the 90.
Things like extra zones/video processing were things that i did'nt really need, and everything pointed me to the 90.

 

[TLS Guy]

You have very nice speakers, but it is a fact that their impedance/phase angle vs frequency curves are evident that supports they are not just so called hard to drive, but are in fact hard to drive, relatively speaking. That said, it is still important to consider the key factors that include listening habit and seating distance, as if those two conditions are "right", even a midrange AVR can do the job, if not, then amps rated 300 W/500 W 8/4 ohms such as the Hypex NC502MP, or ATI6000 or AT54XNC series. Great speakers deserve great amps!

The point is, at that price you should be able to buy any decently designed amp to drive them, and not have these concerns. What make it even more depressing is that Raymond Cooke the founder of KEF taught an published circuits designed to correct these issues.

When I designed my three ways and made a definite tribute to him in the design. I used his teachings on impedance correction.

This speaker can easily be driven by any decent respectable amp.

The driving amp barely gets war, even if you push them hard, and the are driven full range and not crossed over.

If a customer is going to spend that much as the OP on speakers, he should not have to worry about them blowing up any well designed amp.

 

[highfigh]

Tried to email them about it but seems impossible from a phone, won't scroll sideways.
Unless theres a simplified phone version, which i can't seem to access.

Sorry, I meant EPDR, not typical impedance.

 

[highfigh]

In terms of current, lower EPDR than the impedance does not increase current, but could result in a lot more heat in the output devices so not a good idea.

How does heat increase without higher current?

 

[PENG]

How does heat increase without higher current?

Ideally, if the load is like a resistor, the heat will be mostly dissipated in the load resistor. If the load is highly reactive, such as a combo of an inductor and a capcitor (speaker loads are obviously somewhere in between), then almost no heat will be dissipated in the load but would end up getting dissipated in the amp’s output devices, resulting in the amp running much hotter and may also result in stability issue.

 

[highfigh]

Ideally, if the load is like a resistor, the heat will be mostly dissipated in the load resistor. If the load is highly reactive, such as a combo of an inductor and a capcitor (speaker loads are obviously somewhere in between), then almost no heat will be dissipated in the load but would end up getting dissipated in the amp’s output devices, resulting in the amp running much hotter and may also result in stability issue.

I know that but how many speakers present a purely rsistive load? However, load resistors still need to be driven by output devices and THEY become warm/hot due to the current conducted by them, too. If the temperature of the drivers' voice coils increases, the resistance should increase, too- that won't happen instantly at low/moderate levels, but if the system is driven like a plow horse, it could mitigate some of the effective impedance drop, as seen in EPDR.

 

[PENG]

I know that but how many speakers present a purely rsistive load? However, load resistors still need to be driven by output devices and THEY become warm/hot due to the current conducted by them, too. If the temperature of the drivers' voice coils increases, the resistance should increase, too- that won't happen instantly at low/moderate levels, but if the system is driven like a plow horse, it could mitigate some of the effective impedance drop, as seen in EPDR.

Yes, that's why I use words like "most", "almost", it is all relative. The simple fact is, heat = I^2*R so it the load is a resistor, most of the heat involved will be in the load, not the amplifier. If the load is highly reactive, then most of the heat will be dissipated in the output devices.

In the latter case, it is too much to try and explain it in an easily understood way as it involves more than Ohm's law lol.., so if you really want to understand the details, please do your own research as I have done in the past.

Below is a couple of places for a good start, without spending too much time on it:
Phase Angle Vs. Transistor Dissipation

And, below is interesting, but lots of people don't realize, when all they care are "power/watts":

The 'magic' figure of 45° is worst case with typical systems, where the transistors must dissipate double the normal peak power, while the load only receives half the power it would normally get. Note that the amplifier peak dissipation appears to fall after 45 degrees - this is only because of the increased impedance presented because of the reactance. While these figures are reasonably accurate, it must be understood that the situation varies depending on output power and supply voltage - there are a great many variables, and it is not practical to try to cover them all.

The load power is interesting. Notice that at 90 degrees, there is zero power delivered to the load! There is voltage and current (referred to as VA with transformers), but no power, so no physical work is done - the speaker would be silent. This phenomenon is well known in the power industry, and is called power factor. The ideal case is a power factor of 1, where every volt and amp is converted into work - heat, light or rotation (for example).

Obviously, the worst case is a power factor of zero. Volts and amps are readily measured, yet no work is done, and the electricity meter remains still. The majority of real loads are somewhere in between, and the loudspeaker is no exception. A speaker load will always have a 'real' component in the equation - the voicecoil resistance - so a power factor of zero is not possible. It is beyond the scope or intent of this article to discuss this further, so I won't.

The essential to understand is that any power amplifier must have sufficient reserve power dissipation in the output (and driver) transistors to handle the maximum possible peak thermal loading. In real terms, this always means more (or larger) output devices than you anticipated.

As usual, this website covers lots more than the above on power dissipation, but the above article is just a good starting point.

Now the popular EPDR, that also seem to get misunderstood a lot, as it mislead (inadvertently) some to think high phase angle results in higher current drawn, where in fact, Stereophile use this concept to illustrate in terms of heat, the effects would be as though the load draw more current. That's a case of creating new confusion, while trying to make complex matters easier for people to understand. And specifically, in this EPDR thing, Stereophile uses the "equivalent" concept, using lowered impedance, there would result in higher current (Ohm's law) and then people can understand right away, higher current means tougher on amps, when in fact, what makes it tougher on the amp is the higher power dissipation portion in the output devices, current does not really change because if the load is say 4 ohm, if the output voltage is 40 V, then the current is still 40/4=10 A, regardless of the phase angle. It is only that with a larger phase angle, the effects of the 10 A that goes through the output device, would result in more heat in the output devices (usually power transistors) than if the phase angle is smaller. I need to stop now, as I am just writing casually/randomly, and I know I am expressing myself well, so please try the links provided and you will have better time than reading my post.

Equivalent peak dissipation resistance, EPDR | AV NIRVANA

Heavy Load: How Loudspeakers Torture Amplifiers Page 2 | Stereophile.com