Let's Talk About Amplifiers (1 Viewer)

[Dave Upton]

I am rather new to the forum so a bit of a late comment perhaps. In my relatively short time in HT, I have made great improvements by adding external amps to my set up. But, I have a question - my HiFi system utilises two 50 watt mono blocks and has two speakers, my HT has four amplifiers, around 1,400 watts, with 5 speakers. My HiFi system has more power than I will ever need and certainly doesn't have any problem creating a huge dynamic sound stage. How come I need so much more power with HT?

Hi Martyn,

I'm going to quote an old reply of mine which mostly explains this. The primary factors are transients (momentary power requirements) which are much more intense in theater applications, and damping/bass output:

Speakers have an electrical impedance they present to the amplifier which is often not quite what is advertised (note all speakers are a 4 or 8 ohm load, so the value is often rounded) and can vary quite a bit. On top of this, each speaker has a sensitivity factor that denotes how easy they are to drive. This used to be measured in SPL/w/1m - so sound pressure produced by 1W at 1m. This is now changing to SPL/2.83V/1m - which is a more accurate measurement that good designers are adopting.

Some designs are highly sensitive and will produce >90dB of sound driven by 2.83V at 1 meter, while others are quite hard to drive, at <85dB sensitivity. Give this a read if you're interested in more detail: https://www.audioholics.com/loudspe...dspeaker-sensitivity-engineering-vs-marketing

Keep in mind that the dB is logarithmic, a 6dB increase in measured sound pressure level (SPL) reflects a perceived doubling in volume, but a 3dB increase requires a doubling in power. More on that here. This means the difference between 91dB sensitivity and 85dB sensitivity is the difference between comfortably driving a speaker with a 5W SET amp and needing a 150W amp. When someone says a low powered class A amplifier drives inefficient speakers with ease, you need to define inefficient (because chances are the speakers in question are not *really* that inefficient), and also question the ears of the reviewer. There are a few speakers that are notoriously hard to drive (Apogee, Thiel) and no matter what some reviewer says, will sound like hot garbage when fed with moderate power.

I feed my ATC SCM19's which are 85dB sensitive with a 1500WPC amp. I likely never use this kind of power, but when listening at higher levels, transient (momentary) power demand can be much greater than average power demand. That sudden kick drum hit might require 10X the amplifier power for a fraction of a second, and if the amp can't deliver that - it will not reproduce the transient as accurately. This is much more common for low frequency transients, so home theater nerds like me are very concerned about amplifier headroom (excess power for these situations). Here's a good summary on that topic: https://pro.harman.com/insights/har...of-using-power-amplifiers-that-are-too-small/

Damping factor is typically higher in amplifiers with higher power output, but is not a result of power but output impedance, wire length and the speaker's impedance or load. I think many folks hear tighter bass and assume it's damping factor at play, which is not like always the case.

Ultimately, tight bass (removing acoustics from the equation) is a function of controlling the moving mass of the transducer. This is the result of the electrical ability to put the brakes on a woofer that is already at peak excursion and bring it back to a resting state. There are a ton of ways amp designers try to do this, but in general you'll find the best engineered amps typically have this consideration in common.

 

[Old Dog]

Thank you Dave!
Checking out those links has certainly blown away one thing I thought I knew (3dB = doubling of loudness).
Not being a very technically minded person, I try to understand technical concepts, but often, especially these days, a lot tends to go over my head. Just trying to think if I can turn that into a benefit of being old
I have always thought it better to have too much power rather than not enough, and still think it is surprising what relatively modest power amps can achieve with "typical" speaker loads, dependant, of course also on room size.
Recently, I thought bridging the Parasound (to produce over 600w) to power the centre in my HT would be overkill and totally unneccesary, not least because the amplifier I already had hooked up to it was rated at 260w. Whether it is down to raw power or whether it is down to synergy between the components I don't know, but the difference was really not minor.

 

[JohnRice]

Thank you Dave!
Checking out those links has certainly blown away one thing I thought I knew (3dB = doubling of loudness).
Not being a very technically minded person, I try to understand technical concepts, but often, especially these days, a lot tends to go over my head. Just trying to think if I can turn that into a benefit of being old
I have always thought it better to have too much power rather than not enough, and still think it is surprising what relatively modest power amps can achieve with "typical" speaker loads, dependant, of course also on room size.
Recently, I thought bridging the Parasound (to produce over 600w) to power the centre in my HT would be overkill and totally unneccesary, not least because the amplifier I already had hooked up to it was rated at 260w. Whether it is down to raw power or whether it is down to synergy between the components I don't know, but the difference was really not minor.

Too much power? You’re talking to the right guy. Dave has even me beat, and I have 1000 wpc to my front three channels. Power is a good thing.

 

[Old Dog]

I think I mentioned in my new member post something about can't teach old dogs new tricks? I have never felt the need for huge amounts of power with my HiFi. My modest 50 watt monos have always proven to be more than capable for my requirements. I seem to be appreciating the benefits of more power now though with HT.
What was that about old dogs and new tricks?
1000 wpc seems obscene (at the moment!) - I was looking for a smiley with a tin hat to put here, but couldn't find one

 

[ManW_TheUncool]

Too much power? You’re talking to the right guy. Dave has even me beat, and I have 1000 wpc to my front three channels. Power is a good thing.

Wait. Did you upgrade from the Emotiva DR amps? OR do you mean they're doing 1Kwpc into 4 ohms (and maybe somewhat lower impedance... for your Thiel CS3.6s)?

I just doublechecked, and the DR2 (stereo) is rated for 800wpc into 4 ohms though the DR1 (mono) is rated at 1Kwpc into 4 ohms.

IIRC though, the DR2 probably can actually exceed 1Kwpc into 4 ohms before clipping in practice (based on testing from a published review or two) vs what might possibly be somewhat conservative ratings provided by Emotiva...

_Man_

 

[JohnRice]

Wait. Did you upgrade from the Emotiva DR amps? OR do you mean they're doing 1Kwpc into 4 ohms (and maybe somewhat lower impedance... for your Thiel CS3.6s)?

I just doublechecked, and the DR2 (stereo) is rated for 800wpc into 4 ohms though the DR1 (mono) is rated at 1Kwpc into 4 ohms.

IIRC though, the DR2 probably can actually exceed 1Kwpc into 4 ohms before clipping in practice (based on testing from a published review or two) vs what might possibly be somewhat conservative ratings provided by Emotiva...

_Man_

Yeah, I'm referring to the DR2s, which do test out to provide at least 1KW into 4 Ohm, despite the 800WPC rating.

 

[John Dirk]

I feed 1350 WPC to my Legacy Focus SE's. It's really analogous to Internet bandwidth. There if needed, harmless otherwise.

 

[Clinton McClure]

Reminds me of my youth when I competed in car audio. A single 12” dual voice coil sub fed 1000w RMS at 4Ω and producing 142dB at the windshield.

 

[Old Dog]

OMG! Beginning to feel like the odd one out here

 

[Old Dog]

I feed 1350 WPC to my Legacy Focus SE's. It's really analogous to Internet bandwidth. There if needed, harmless otherwise.

That may explain it, my internet connection comes in at a massive 6.5 mbps. HaHa It might be funny if it wasn't true.

 

[MannyE]

I think it's past due to have an open, continuing thread discussing external amplifiers, using separates and so on. Especially helping to understand what benefits they present.

I definitely have things to start off with, which I will do once I get home from work.

In the meantime, let's get going on the topic.

I realize that not everyone "believes" in using external power, but please, no thread crapping. Let's keep it to constructive, first hand and helpful information on the topic.

I find when a thread goes beyond 3 or 4 pages, a refresher quote of the OPs original post is helpful.

I've recently had to finally move away from my beloved B&K Reference 50S2 preamp/Outlaw 750 combo because after almost 20 years, it finally gave up the ghost.

I'm absolutely flabbergasted at what is considered "enough" power in this day of 7,9 and even 11 speakers and the cost associated with these things. It seems everything is powered by D class amps that barely have enough power to drive TWO stereo speakers. And the ridiculous way of measuring that output.

I just bought a Denon AVR-X3700H that costs $1,300 REFURBISHED and it's only rated at 105 WPC into TWO speakers. What will that mean for a full complement of 9? 60 watts? What kind of speakers does Denon (And every other mid-range manufacturer (not picking on Denon... heck,I just bought one) think we are running? Lowthers? Maybe Fostex?

The reason I bought the 3700 is because it has those all-important pre-outs so that I can put my Outlaw 750 between it and the DefTech speakers I have now. And I will be looking for Outlaw 2220 monoblocks after I finish renovating the HT (and recover from the cost of said renovation) early in 2023. The 750 sends 165 watts to each speaker and eventually, if I can find the monoblocks, they will take over RCL duty (they produce 200 watts) and the 750 amp will go to adding height channels so I can see what this ATMOS hooey is all about.

I dunno if it's because mid-range receiver makers think that most people these days have tiny speakers or super-efficient speakers that those miniscule D amps can work with, or maybe I'm not aware of how far speaker technology has come since I bought my current set in the late '90s. Would love to hear a system that can make 60 WPC (pulling that out of my butt) sound convincing during, say, Saving Private Ryan D-Day scene or Mad Max Fury Road, or Endgame.

 

[ManW_TheUncool]

I find when a thread goes beyond 3 or 4 pages, a refresher quote of the OPs original post is helpful.

I've recently had to finally move away from my beloved B&K Reference 50S2 preamp/Outlaw 750 combo because after almost 20 years, it finally gave up the ghost.

I'm absolutely flabbergasted at what is considered "enough" power in this day of 7,9 and even 11 speakers and the cost associated with these things. It seems everything is powered by D class amps that barely have enough power to drive TWO stereo speakers. And the ridiculous way of measuring that output.

I just bought a Denon AVR-X3700H that costs $1,300 REFURBISHED and it's only rated at 105 WPC into TWO speakers. What will that mean for a full complement of 9? 60 watts? What kind of speakers does Denon (And every other mid-range manufacturer (not picking on Denon... heck,I just bought one) think we are running? Lowthers? Maybe Fostex?

The reason I bought the 3700 is because it has those all-important pre-outs so that I can put my Outlaw 750 between it and the DefTech speakers I have now. And I will be looking for Outlaw 2220 monoblocks after I finish renovating the HT (and recover from the cost of said renovation) early in 2023. The 750 sends 165 watts to each speaker and eventually, if I can find the monoblocks, they will take over RCL duty (they produce 200 watts) and the 750 amp will go to adding height channels so I can see what this ATMOS hooey is all about.

I dunno if it's because mid-range receiver makers think that most people these days have tiny speakers or super-efficient speakers that those miniscule D amps can work with, or maybe I'm not aware of how far speaker technology has come since I bought my current set in the late '90s. Would love to hear a system that can make 60 WPC (pulling that out of my butt) sound convincing during, say, Saving Private Ryan D-Day scene or Mad Max Fury Road, or Endgame.

I imagine it's mostly just the current economics of the bizz (and their sense for demand in their market segments) driving them to essentially cut corners in that way given the current available and/or demanded tech...

If the vast majority of customers in their market segments don't seem to understand and/or care that much about how underpowered AVRs are, then they're going to put little or much less in that part of the equation. And for those who do understand and care (but don't want to or aren't prepared to go w/ all separates), they're providing ways to supplement via pre-outs w/ whatever needed settings/adjustments to accommodate (again, to varying degrees based on demand and corresponding costs/pricing)...

Of course, the vast majority of people probably simply aren't that picky (to put that concisely) about sound quality to care enough, so...

_Man_

 

[MannyE]

I imagine it's mostly just the current economics of the bizz (and their sense for demand in their market segments) driving them to essentially cut corners in that way given the current available and/or demanded tech...

If the vast majority of customers in their market segments don't seem to understand and/or care that much about how underpowered AVRs are, then they're going to put little or much less in that part of the equation. And for those who do understand and care (but don't want to or aren't prepared to go w/ all separates), they're providing ways to supplement via pre-outs w/ whatever needed settings/adjustments to accommodate (again, to varying degrees based on demand and corresponding costs/pricing)...

Of course, the vast majority of people probably simply aren't that picky (to put that concisely) about sound quality to care enough, so...

_Man_

They also figure only a tiny percentage will take advantage of those pre-outs so they don't include them in anything that can be considered "budget" Because while $1300 is considered a low priced receiver relative to the high end choices, I suspect that these days only a few people would be able to allocate that nut to one piece of the HT puzzle.

In another thread where I asked for advice on a new AV Receiver, a couple of people were surprised that pre outs were no longer a thing on sub-$1000 units. Even $1200 doesn't get you pre-outs unless you're shopping used and that's a minefield I don't have time for.

 

[JohnRice]

I just bought a Denon AVR-X3700H that costs $1,300 REFURBISHED and it's only rated at 105 WPC into TWO speakers. What will that mean for a full complement of 9? 60 watts?

That's probably about right. Keep in mind, that would mean it can provide 60 watts to all channels simultaneously, but in most cases it won't need as much to the surround and overhead ones than the front three.

Still, I'm discovering that it's nearly impossible to get most people to really consider adding an external amp. They'll spend $5K on a receiver believing it provides ultimate power, but won't consider a less expensive receiver and a $500 three channel amp (like the Emotiva a3) dedicated to the front three channels or the $769 five channel Outlaw x5000. Even though that move will, in the real world, more than double the total power available to the system. The improvement in dynamics would be significant in most systems.

 

[MannyE]

That's probably about right. Keep in mind, that would mean it can provide 60 watts to all channels simultaneously, but in most cases it won't need as much to the surround and overhead ones than the front three.

Still, I'm discovering that it's nearly impossible to get most people to really consider adding an external amp. They'll spend $5K on a receiver believing it provides ultimate power, but won't consider a less expensive receiver and a $500 three channel amp (like the Emotiva a3) dedicated to the front three channels or the $769 five channel Outlaw x5000. Even though that move will, in the real world, more than double the total power available to the system. The improvement in dynamics would be significant in most systems.

Maybe conveying the reality that while processor software and surround modes will evolve, amplifier tech is pretty much the same as it was whenever the change from valves to ss happened.

Yes, there are improvements, but generally, if you bought a good amp 20, 30 or even 50 years ago, it will still work (assuming it's been serviced regularly). Yes, it might be a bigger expense now, but when the fickle HT science community decides the new standard is going to be ATMOS HOLO17 or whatever, all they have to do is go get a processor, boom! done.

Another advantage is if the AV receiver they own has a sound they just love, but is discontinued, and a lightning bolt took it out, no problem... buy one used and keep on going without worrying about that amp section that just spent 5-7 or however many years getting really hot...

I dunno, my point is amps last forever, processors, not so much.

 

[ManW_TheUncool]

They also figure only a tiny percentage will take advantage of those pre-outs so they don't include them in anything that can be considered "budget" Because while $1300 is considered a low priced receiver relative to the high end choices, I suspect that these days only a few people would be able to allocate that nut to one piece of the HT puzzle.

In another thread where I asked for advice on a new AV Receiver, a couple of people were surprised that pre outs were no longer a thing on sub-$1000 units. Even $1200 doesn't get you pre-outs unless you're shopping used and that's a minefield I don't have time for.

No doubt... as John subsequently mentioned above.

Yeah, they used to include pre-outs in much more affordable AVRs... and in fact, a budget-ish AVR -- a ~$550 (MSRP) Yamaha model that I paid only ~$350 towards the end of its production run back around 2008/2009(?) -- was the last-and-only AVR I ever bought... and I've never actually bothered to use its amp section at all since I already had a solid B&K 5-channel amp... and still have that AVR in storage for the past year (and mainly used it for headphone output in my home office after I upgraded the HT back to a prepro). That old, budget-ish Yamaha AVR worked quite well as a prepro (though w/ only 2 HDMI inputs... and of course, no Atmos/DTS-X and very minimal bells-and-whistles)...

I've essentially retired the 25-30-yo B&K amp now (relegating it to 2ndary duties on its dying last legs... as it's probably too expensive to bother repairing/restoring/refreshing)... and switched to an Emotiva XPA-5 Gen 3 instead (at least for now)...

_Man_

 

[3dbinCanada]

I imagine it's mostly just the current economics of the bizz (and their sense for demand in their market segments) driving them to essentially cut corners in that way given the current available and/or demanded tech...

If the vast majority of customers in their market segments don't seem to understand and/or care that much about how underpowered AVRs are, then they're going to put little or much less in that part of the equation. And for those who do understand and care (but don't want to or aren't prepared to go w/ all separates), they're providing ways to supplement via pre-outs w/ whatever needed settings/adjustments to accommodate (again, to varying degrees based on demand and corresponding costs/pricing)...

Of course, the vast majority of people probably simply aren't that picky (to put that concisely) about sound quality to care enough, so...

_Man_

I disagree with all of your assertions. Putting power amps into any one my 3 Yamaha AVR powered systems will NOT improve the sound one little bit. All of my AVRs are barely touching their power reserves even when pushing my speakers into the high 80 low 90 db which is very loud BTW. My eldest AVR predates HDMI and is getting close to 20 years old and it still operates without a glitch. My newest one is an RX-A3060 which I bought used and its working without any glitches.

 

[ManW_TheUncool]

I disagree with all of your assertions. Putting power amps into any one my 3 Yamaha AVR powered systems will NOT improve the sound one little bit. All of my AVRs are barely touching their power reserves even when pushing my speakers into the high 80 low 90 db which is very loud BTW. My eldest AVR predates HDMI and is getting close to 20 years old and it still operates without a glitch. My newest one is an RX-A3060 which I bought used and its working without any glitches.

Shrug... Not just my assertion(s)... but obviously, you belong to the vast majority who don't feel the need for more, cleaner power from a separate/external amp (no matter the details and finer points), so we have what we have in the marketplace, which was actually what that post was mainly speaking to (in follow-up to others who feel that way)...

Anyhoo, if you're happy w/ your AVRs in your particular HT setup, I'm not here to tell you otherwise...

_Man_

 

[3dbinCanada]

Shrug... Not just my assertion(s)... but obviously, you belong to the vast majority who don't feel the need for more, cleaner power from a separate/external amp (no matter the details and finer points), so we have what we have in the marketplace, which was actually what that post was mainly speaking to (in follow-up to others who feel that way)...

Anyhoo, if you're happy w/ your AVRs in your particular HT setup, I'm not here to tell you otherwise...

_Man_

If one isnt tapping into the power, then its not needed. Having extra power doesnt provide benefit until needed. The benefits of adding power needs be verified by controlled DBT listening tests, not subjective evaluation filled with biases that the listener is unaware exists. I'm also in the camp that all amps sound the same provided they stay well within their power delivery envelope.

 

[JohnRice]

"Bias" might be defined as joining a thread dedicated to a certain topic with the sole purpose of asserting that topic is imaginary.