More power for moderate listening levels?

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? 

My 3 year old and 6 year old. 

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.

@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.

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.  

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.

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.

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

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.

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. 

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

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

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. 

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.. 

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!

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. 

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.

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.

@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:)

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?

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

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. 

 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.

@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.

@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?

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. 

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. 

@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.

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

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.

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