More power for moderate listening levels?

Hello atmasphere,

     Awesome post.  I feel like I just went to a graduate level class, learned a lot and enjoyed it all very much.  Just excellent and I friggin mean it!

Thank you,
   Tim

My assumption is that the bigger Pass integrated would clean up the sound at higher decibels and would be a measure of protection against speaker damage if one of my family members decided to crank it when I'm not around.

It will help. But keep in mind that to go from 80 watts to 130 isn't even 3dB, and 3dB is a slightly higher volume level- its not much. You need about 10dB to seem like its 'twice as loud'. This phenomena has a name in the electronics world- its known as 'gold-plated decibels' since the price of an amplifier needed to really do the job, that also sounds as good as the one you have now, goes up exponentially. That is why a more efficient speaker is the better investment dollar-wise (and sound-wise). 

For that matter, what are your opinions on balanced vs. single-ended designs?

I'm a big fan of balanced designs (and my company was one of the first to offer them to home audio; we made the first balanced line preamps made anywhere). So my perspective might be considered skewed. But balanced circuits tend to have less problems with power supply noise and offer the potential for lower distortion as even ordered harmonics are cancelled. This means that the 3rd harmonic is the primary distortion component, and the 3rd is treated by the ear the same as the 2nd (adds a little 'bloom' but is otherwise innocuous and inaudible), but it will be at a much lower level than amps that tend to generate a 2nd harmonic as their primary component (for you math nerds, the difference between a quadratic non-linearity and a cubic non-linearity). This means the circuit can be more neutral, as the ear treats all forms of distortion as some form of tonality (hence the 'bloom' I mentioned). If the circuit is differential in nature, it will also have less noise for any given amount of gain; by a maximum of 6dB per stage of gain.


Now when you run balanced, you also have the opportunity to run balanced line interconnections. The advantage of this is that the balanced line connections have far less sonic artifact than single-ended cables (if you've ever auditioned the latter and heard differences, you know what I'm talking about) but this aspect is only realized if the equipment supports the balanced line standard, known as AES48. Most high end audio equipment doesn't seem to support the standard; my theory for this is either the manufacturer does not know it exists, regards it as too expensive, or sees it as an impediment because there are really very limited ways to do it correctly (one of the better ways to do it is with an output transformer, for example at the output of a preamp). But its nice to be able to run 30 feet of inexpensive interconnect, so you can have the amps right by the speakers and run short speaker cables- this advantage alone results in immediately audible greater resolution! Its nice to get off the interconnect merry-go-round at the same time.

As per Stereophile: XA25 80 watts into 8 ohms; XA30.8 130 watts into 8 ohms; and you can go up from there.

@atmasphere 
@twoleftears 

I purchased the Pass based on the measurements given by stereophile as well as reports of folks achieving great sound with lower power tube amps driving the Shl5. So far so good. With the volume halfway, the sound at my chair is fantastic with no strain. I'm a big fan of the sound when these two components are put together. The limitations of the system become apparent at much higher levels and with certain types of music. My assumption is that the bigger Pass integrated would clean up the sound at higher decibels and would be a measure of protection against speaker damage if one of my family members decided to crank it when I'm not around. Aside from the balanced design of the bigger Pass, does the extra headroom power-wise afford better sound at the levels that I normally listen to? For that matter, what are your opinions on balanced vs. single-ended designs? I would also be able to use the balanced outputs on my DAC.

My Klipsch KLF 20 with 100Watts Denon receiver sounds better, more live and dynamic with electronic and dance music than my Gershman Grand Avant Garde powered by 125Watts Plinius SA 102. As someone suggested, a separate system for dance music may be a cheaper solution if you have a space. Used KLF 20 and 100Watts receiver (or int amp) will cost $1000 or less.
By the way, my Harbeth C7ES sounds good at moderate listening level, but when cranked up with 125 Watts class A amp, it sounds stretched and nosisy. 

how does one assign a nominal single value in ohms to describe the impedance of this speaker?

Everyone does it different I imagine. 'Nominally' this looks like an 8 ohm speaker- if so that throws off my efficiency calculation by about 1.5dB. The impedance curve looks fairly benign, which is good. Its really the efficiency/sensitivity (which since its nominally 8 ohms are about the same thing) which is the issue here. Its assumed from the plot that the amplifier won't make a lot of power driving the impedance peaks- since the amp is a voltage source and the speaker is intended for that. 

@atmasphere 
Here's Stereophile's test of the Harbeth SLH5 plus.
https://www.stereophile.com/content/harbeth-super-hl5plus-loudspeaker-measurements
It drops to 6 ohms at one point, and just below 6 ohms at another point.  But for much of the range it is over 8, and for some of the range significantly over 8.  With the degree of variation of impedance that one can see in the plot, how does one assign a nominal single value in ohms to describe the impedance of this speaker?

@brianbiehs

If I got this right and the Harbeth is 6 ohms and 86 dB, its actual efficiency is around 84dB. That isn't quite criminally low efficiency, but it is quite low and in most rooms you're going to need about 600 watts to make it play. This is why the amp is being overloaded (which BTW also puts the tweeter in the speaker at risk; that's the classic method to damage a tweeter).


600 watts is a lot of power and that sort of requirement makes it a lot harder and more expensive to find an amp that sounds as good as one that makes only 100 watts. Further, there's really no reason to make a speaker that inefficient. It isn't bandwidth, it isn't speed, it isn't resolution. Plus when speakers are that inefficient, you get thermal compression caused by heating in the voice coils.


If you are driving that speaker with 100 watts (which is about what the Pass will do at clipping) it will make a certain sound pressure. But if the speaker were 94 dB instead of 84, you would need only 10(!) watts to make the same sound pressure. Now my speakers at home are 98dB and just to avoid doing the math I'm going to say for this argument that they are only 97dB... so 3db more than 94dB means that I can make the same sound pressure as you can with only 5 watts. I can tell you that in my listening room which is slightly on the small side that even with my speakers that isn't nearly enough. BTW a 3dB difference is a doubling of amplifier power, a 10dB difference is 10x the amplifier power. Decibels (dB) are on a logarithmic scale since that's how our ears hear.


I'm running an amp that makes about 45 watts/channel and its impossible to clip it in my room. To put that in perspective, that would be like having an amp that has 900 watts/channel in your system. In simple terms you're a country mile off when it comes to matching these two products.


The simple solution here is that if you like that amp and don't feel like going on the hunt for a 600-900w/channel **integrated** amplifier, change out the speakers for something more efficient! The combo might sound great at low levels, but if you want to hit anything that might be considered 'satisfying' its not going to work as you well know.

 I added a T+A power supply that adds 1800 watts.

Power is V x A.
Increasing 4Ω power from 500 to 1800 requires changing the voltage from 45 to 85. Current would increase from 11 to 22A. It very unlikely the output devices were that over spec'd and the heat almost certainly wasn't.

FanBoy prattle.

My amp puts out 500 watts into my 4 Ohm speakers. Sounds great. I added a T+A power supply that adds 1800 watts. I rarely play music over 84 decibels, generally in the 64 to 78 range at my listening chair.  With the extra 1800 watts I found listening at low levels to be more enjoyable & where the biggest difference was. You can actually feel the music at low volume levels, incredible dynamics also. 

That has got to be a lot more than a few mV bias.

The JC1 has 9 pairs of output transistors.
25W ≈ 22mV across 18x 1.3Ω emitter resistors

The "transition" for my lack of a better term for class A to B operation is really interesting. Certainly, the class A watts do not "go away" but get "added to" as more power is needed. Curious how the output device can operate in both modes. Am I thinking about this right?

@ieales, it would not be polite to tell you what I think of Tekton loudspeakers. 
I am pretty sure most speakers are destroyed not by raw power but by clipping. Certainly you could just plain overpower a driver but most people do not have that kind of power. 
I am not an electronics engineer but my JC 1's biased for 25 watts class A get hot enough that you can not keep a hand on the heat sink. That has got to be a lot more than a few mV bias. 
Who in their right mind would put a class A amp in a rack? Even millercarbon would not do that:)

I'm hoping the higher power amp (15W Class A before switching) shares some of the sonic character of the current amp.

Class AB amps don't 'switch' per se. The slide into Class B. Depending on the design and the load, the transition can be smooth and less so.

Getting AB bias currents exactly right as the amp plays is an engineering challenge. It almost always lags the amp's thermal state. Manual bias amps are frequently mis-biased from the factory as the amp is set up with the covers off in an environmentally controlled lab. Close it up and stick in a rack and all bets are off.

see https://www.zenmod.in.rs/pass-labs-x150-5-checkingadjusting-offsets-iq-and-gain/ for a Pass 150.5 bias adjustment tutorial.

Like many other recent 'inventions', 15W Class A before switching is nothing more than ≈30mV bias across 10x 2Ω emitter resistors in ± amp halves.

Pass is a brilliant designer with an impeccable pedigree, so his designs are likely SoA.

As opposed to choosing what is bad, I guess. Like tuberculosis.

@millercarbon 
Yeah, you named it. Now you will have it for the foreseeable future.

OP, many posters want you to buy what they have in speakers and amps. Sure that would be great.

It would be worth it if the reserve power of the new amplifier improved sound quality at all levels.

Yes, that is it. But if you are happy with your speakers as you seem to be, add more power. Same brand amp, different brand amp, what ever. Don't change your speakers, get more power. You'll be happy.

OP I was in the same dilemma not too long ago. My current set up, which I settled for is a small office (14x8) where I do low to moderate level listening. I have Harbeth p3esr and Croft Integrated amplifier. The pair excel and I mean excel in low to moderate level listening bringing out the best. Non-fatigue hours of listening with the perfect amount of details and warmth. 

As soon as I took the set up to my living room and throw a little party with the family it was a massive disappointment. There are a multitude of factors why that happened. The music genre changed and the power given to the amplifier changed in a much larger room. 

Harbeth p3 struggle with dance, electronic and rap music at loud volumes driven with an underpowered amp. I plugged in my 300w/channel earthquake amp followed by 180w/channel sim Audio W5 amp. Big difference - but that's where the p3 limitations kicked in. 

My recommendation - keep your dance party/family/home theater gear separate from your intimate listening room. I am very happy with my party/home theater room set up with Von Schweikerts VR4 speakers and Sim Audio w5 and Earthquake amp. 

Hope this helps somewhat. 

I got tired reading the answers; some may have been correct(I apologize for being impatient). Having a "high current amp" is what you want. The dynamic range of the source, the type of music you're reproducing, will dictate how much "power" you really need. To properly reproduce the 1812 overture’s canon shot, you will need almost 800 watts per channel of high current power. It’s the dynamic range. Most of your listening, may require only a modest amount of power. It’s when the drummer hits those cymbals, kick drum, or something like this-that’s when you need that extra current, which transfers into wattage, or your amp will "clip", trying to reproduce that passage or note. Caveat-I love Class "A" bias amps. They’re always wide open just sitting there waiting for you to turn up the preamp. Think of it like a hot fuel dragster sitting at the line, waiting for the go light. It’s revved up to max RPM’s-then the clutch is let out!

If you go about it bassackwards as Chucky says you’re in for trouble.

<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>

A laugh a minute.. If you know your equipment you buy accordingly..
MC knows his equipment..  Low watt amps 1st and second order XOs and well matched drivers with HIGH E factors, are a match made in heaven. Pass and Tekton are just that..

Power amps are rated by class. Class A, AB, and D are probably the most common.  There are valve amps that are pure class A, AB the same as SS but class Ds I seen hybrids of tube front ends and class d power amps..

Class A Amps run wide open, as you increase the power they actually cool down, AB is both usually, A up to a bias point and then AB from that point on.. Then it will create more heat....than the actual set class a bias point.. I'm sure someone will chime in all tec like.. LOL Me I'm just al ol mechanic...BUT that is the just of it...

So you could feed the world on circumcision soup, too, YUM ME!!

Get along now, come back for a second bowl of soup., any volunteers?

Regards.. 

Again, it's a matter preference. I'm hoping the higher power amp (15W Class A before switching) shares some of the sonic character of the current amp. Chalk and cheese or cheddar and brie. I think I will try. 

That sounds like a recommendation to change speakers to your fav.

As opposed to choosing what is bad, I guess. Like tuberculosis.

If you have never inserted a high power amp into your system, now is the time to try it out. Beg, borrow, or steal a big amp and give it a try. 

Tekton makes some great speakers, very high efficiency, great sound, and their favorite amp is Pass. It would seem a match made in heaven.  

That sounds like a recommendation to change speakers to your fav.

That’s not a contradiction, because I never said to buy speakers to match your amp.

To contradict Mr. Miller, you don’t buy speakers to match your amp. If you like your speakers (and I don’t have any familiarity with them), buy an amp that matches the speakers.

My mains are 85 dB sensitivity. I use tube mono blocks. When I started they had the popular EL34s, very sweet sounding but not enough power for the speakers at 50 watts in triode mode. I swapped the EL34s out and replaced them with KT150s doubling the power. In triode mode I now have 100 watts and can play almost anything at a reasonably loud volume. When I switch to ultra-linear it doubles the power again and you can hear an increase in volume as they switch in real-time. They’re 3 dB louder. Now at normal listening levels I have plenty of power in reserve for peaks and dynamics and if I want to go to 95 dB I still have enough power for peaks and dynamics. So yes, it is reserve power. Tubes burn the power that is needed based on how hard they are driven by the input signal. I'm absolutely sure someone will correct me if I am wrong, but I believe SS amps burn at full power all the time.


You have to pay attention to the damping factor and the impedance curve of your speakers. Once I had decided on my speakers, I carefully checked all the amp specs to see that I would match to the speakers properly. Then the listening began.


If you go about it bassackwards as Chucky says you’re in for trouble.

I have found that a high powered amp, even at low listening levels, provides a sense of dynamics that a low powered amp doesn't have

And I'm fairly certain that the amps are likely sonically chalk and cheese.

I have found that a high powered amp, even at low listening levels, provides a sense of dynamics that a low powered amp doesn't have, even with Klipsch Forte speakers.  Just makes sense to me.  

@hshifi speaks a bunch of truth here in regards to what constitutes a system for dancing, whether or not you subscribe to the cult of Klipsch or not. When it comes to dance music history there's the Richard Long side, but the Klipsch/Levinson combo is a major crossover for home dancing—the Mancuso/Loft approach, not about "power"—you could do similar with loads of old horn-driven speakers like JBL monitors, Altec, TAD etc... but again, more cults.

Your comments are taken to heart. Many folks swear by the difference that power makes. My initial question which is perhaps somewhat naive is whether all that power acts in a way to control the drivers at medium to low listening levels. It’s just sitting there in reserve but can it affect sound quality. I think a few posters here suggest that it can.

My 3 year old and 6 year old. 

Interesting--lots of commentary here but apparently not by many that own or have experience with Harbeth's. I would suggest you check out the Harbeth user forum. Tons of information there posted by people using many different amps with YOUR speakers. As a former Harbeth owner (and lover) who ran five different amps with my Compact 7s before moving on to another brand and can say this: Harbeth's like--need--power. Each time I put more power in front of my C7's they responded with more jump factor, better dynamics, more projection into the room. You can certainly get good sound with 25 good watts, particularly at low volumes, but if you want to crank them up more power is better. That said, it sounds like you only want to crank them at the occasional dance party and who is listening critically in those instances? 

I have heard, and liked, the HL5+, and to me, even with lower-powered tube amps, it can play quite loudly.  But, my idea of loud might be different from yours.  In building any speaker, compromises must be made, and I doubt that the HL5+ was designed to have extreme volume level as a strength.  The distortion you thought had been creeping in as the volume got louder might be something in the speaker and not necessarily a problem with the  amplifier you were using.  It would be instructive if you can find a more powerful amp to compare with the one you are using now.

I would personally be more inclined to be looking at amps that sound better at the volume levels I normally listen at, even if it means sacrificing some performance when playing at extremely high volume.  This is how I ended up with three tube amps, the one with the highest power rating being 6.5 watts/channel.

"You can never have too much power"--probably attributed to Bob Carver, inventor of the Phase Linear 500 and 700.  Sure, they blew-up a lot, but when they worked, they were shrill and loud.

Bi-amp with an external x-over or get two identical amps that will run in mono.

OR, buy a big honkin' solid state amp and rock out, I guess.

Speakers have to match amps in efficiency vs output to be ideal.

 Your dealer should have pointed this mismatch out to you given your desire for occasional high-volume listening.  Has he/she been to your room and listened to what he/she sold you?

Get a better dealer.

Cheers!

I hadn’t thought of TWO amps!

I have Super HL5 Plus and am currently running them with a 50 WPC tube integrated (ARC VSI55).  They are in my office, so I don't typically crank them up, but with the volume halfway up they are very dynamic and sound great.  At the low level I usually listen, they sound wonderful.  They're not going to fill a large room with sound though with 50 watts and I can't imagine they'd be satisfying with a 25 WPC amp if you want to listen loud from time to time. 

I have used them in my main system with 180 WPC tubed monoblocks and they can go to ear damaging levels, however I think they lose a little finesse. 

One of my friends had 40.2s with a Line Magnetic LM-805iA 48 WPC tube integrated and it was one of the best systems I've heard.  I didn't hear them cranked, but the detail, dynamics, micro dynamics, imaging, soundstage... it was all there. 

A little more quantity wouldn't hurt, but I'd focus more on quality than getting the most watts you can.  That is, assuming you decide you're not satisfied with the levels your current amp can drive the speakers to.

And again, thanks for all the comments and suggestions. I'm seeing that the journey is part of the fun.

All,

As MC stated, it's coming down to personal preference.I really like the sound of the Harbeth/Pass combination. I realize it's not everyone's cup of tea and I do have limited experience. However, I can listen for hours on this system while following precise bass lines and subtleties I did not know existed. Cliche I know.
Given all the great comments, I think the path to audio nirvana is a simple one for me:
1) Sit in the chair and critically listen at highish volumes (without risking speaker damage of course). Do I achieve sufficient loudness without losing clarity and oomph? Case closed.  
2) Sit there and wish for more? Go with more sensitive speakers (doubtful) or get a higher powered amp. If going this route it makes sense to me to skip an animal in the food chain and try the Int-250 with an increase from 95db to 105db at my listening chair. Looking at the distortion/watt graph, the 25 clips at 60W so I'm giving myself a ballpark of about 50W. Someone correct me if I'm wrong, but pushing it to 50W may be a problem if there is a big dynamic range in the music. The 250 deserves an audition but it comes at a steep (for me) price. It may be worth it, it may not.

Klipsch makes wonderful-sounding, efficient speakers.
My thought is keep the current Pass, get different speakers.
Not an owner (I prefer Vandersteens).
Just my 2c...

More power allows you to hear more of the instruments at lower volumes (e.g. sound floor).

I have Martin Logan Spires which are nominally 4Ω, but can draw down to 1Ω on some loads. Yeah, they've been known to blow up underpowered amps.

I drive them with a pair of 900 W monoblocks (4Ω), fed by a tubed (6SN7) preamp. I also have tube monoblocks that put out 75 W. 

When listening with the tube amps, the sound floor doesn't reach as low as with the s/s amps.

If I measured them they would be different again. As I said, I've seen a LOT of fudging and manipulation, of the numbers. How that mic is held what it is held with, background noise, I've seen some weird stuff to get NUMBERS. Wiring out of phase is real big.  Listen to the difference, when the mids are NOT wired out of phase... and when just one of three (EX; mid drivers) is wired out of phase, the number look good but  they sound "FLAT" because they are, they measure flat...

Tekton does not wire out of phase.... I don't know Mr. Pass views on  crossovers, but I do have one of his hand built First Watt  OXO.  Nothing more than 18 db XO, more like 6 and 12 db.. His amps are going to reflect sounding better, with a lower order XO, too.. Those long slopes help a lot when it comes to power demand...and lower watts.

24, 48 db slopes, and any low watt amp, the amp will labor, AND run out of gas.  Even if the E factor is high.... 25 watts is 25 watts..I have to look up the specs on the speakers...I have a hunch about the crossover...I just wonder if it is in the specs without, looking at the actual crossover.

Regards..

Tekton makes some great speakers

IF one likes that sort of thing.

In the Monitor review, Stereophile determined "My estimate of the Impact's sensitivity was 87.5dB(B)/2.83V/m, considerably lower than the specified 94dB." https://www.stereophile.com/content/tekton-design-impact-monitor-loudspeaker-measurements

Truth in advertising: Miller owns Tektons.

I found myself in a similar situation. I drive Sonus Faber Sonettos II with Pathos Classic One MKIII. Although I'm very pleased how it sounds at moderate to loud listening levels, every time I crank the volume up I feel like I miss dynamics and grunt from the amplifier. It seems the amplifier is having a hard time driving the speakers when reaching 85db+ SPL at my listening spot which is no more than 9 feet from the speakers. 
I'm on the same crossway as you. I really like the sound of the pathos but I always feel I need more power for the speakers to shine ...

If you want to go louder and clearer you can change amps and go for more muscle or change speakers to something that is better suited to 25 watts.  But they won't be Harbeths.

Cheapest solution is to bi-amp using 200+ wpc of class D for the bass
speaker.
Use the Pass 25 on the upper only. 

Also borrow/buy someone's measuring equipment to see if and when the clipping occurs.

Then report back.

It really comes down to priorities and preferences. If high quality at high volume is a priority then you need different speakers. Its that simple. The power demands of those speakers at high volume, forget reserve, you need hundreds of watts. Need. To use. Not have in reserve. Whatever that even means. 

Tekton makes some great speakers, very high efficiency, great sound, and their favorite amp is Pass. It would seem a match made in heaven.  

But if on the other hand you're totally in love with the medium volume sound, able to understand what's going on and live with the compromise at higher levels, that's fine too. 

Most of what I see here though sounds like trying to have it both ways. Since horses for courses didn't gain any traction how about don't put legs on a snake? You have some fine speakers, for what they are. Don't try and make them what they're not. Doing something up a rope, or into the wind, comes to mind.

If you enjoy the Pass sound I would certainly step up to a 250.8 you will still be getting the first 18 watts in class A where most of your listening is and plenty of reserve for loud listening. I have one powering my Maggie 3.7 and never hear any straining.

That Pass is a good amp but only 25 w/ch.

WHat you are hearing is most likely the amp clipping, ie struggling to deliver the power needed at higher volume to those not very efficient but very good sounding Harbeth speakers (if driven to the max properly)..

You need more power to go louder and clearer. It’s that simple. Basic physics and hifi 101.

Along with more power, more current delivery capability can again only help. From what I read, that is likely the case with those Harbeth. You need a better quality amp with higher quality power supply for that.

Higher damping factor specs and ability to double power into 4 ohms is a good indicator of a beefy amp capable of delivering lots of current when needed.

That is what you need to play it safe.

What amp specifically? Harder to say. A good quality Class D amp 200 w/ch into 8ohm, 400 into 4 or more would be a good bet. 100 w/ch to 8 ohm, 200 to 4 might even cut it.

It all depends how loud you need to go. Clipping is public enemy # 1. YOu want to avoid that at all costs. Power and current is your insurance policy for that. 25w/ch won’t cut it with most speakers out there for higher SPLs that are loud and clear.

TUbe amps are popular choices with Harbeth and can sound very good, but a higher power tube amp capable of driving Harbeth to their max at higher volume could cost some serious $$$$s and will consume a lot of power whenever on, whereas Class D is a reasonable alternative that should lower cost and keep power bills down.

Most tube amps and Class D amps soft rather than hard clip, so that will make it seem like fewer watts can go furtherbut will limit absolute SPLs and dynamic range. Still more digestible kind of distortion  to the ear than hard clipping. ANother reason tube amps and Class D are both reasonable choices depending.

As long as you can avoid clipping as described, specific amp choice will matter less. They all will be up to the task. Can’t sound good if not up to the task......not as hard if so.