Who's using Harbeth with tubes, what speaker model and how many watts per channel?


Curious what current consensus is regarding the above question.

Thank you.
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I've used Harbeth 40.1's with the following tube amps:
  • McIntosh MC275 MKV - 75 WPC (good synergy)
  • VAC Ren. 30/30 MK3 - 32 WPC (love this amp, but could have benefitted from more power)
  • VAC Ren. 70/70 Sig - 68 WPC (great amp, great synergy)
  • VAC PHI 200 (powerful bass, but lacks transparency and air)
  • Music Reference RM9 MK2 - 125 WPC (great match and added flexibility to use variety of power tubes to tailor  sound... I preferred KT88's with 40.1's)

I recently sold my trusty 40.1's for the 40.2 Anni's and continue to use the Music Reference RM9 MK2 with RAM EL34 tubes... sounds really good!!!  I have no intention of changing this amp... it's a classic and a great value on the used market when they come available.

I also owned a pair of SHL5's for a brief spell and powered them with the VAC 70/70 Sig (68wpc).   Not surprisingly, the SHL5's just don't sound nearly as impressive as the 40.1's and 40.2 Anniversaries to my ears.

I've tried a few solid state amps with the 40.1's and was not as impressed with the sound quality as I've been with the tube amps mentioned above.

I had the Harbeth SuperHL5+ driven by Conrad Johnson Premier 12 amps and CJ Premier 16LS2 pre-amp.

Gorgeous sound.   Rich and organic, but controlled and punchy from top to bottom.
Excellent gentlemen, thank you very much.


Harbeths C7s with either 40 watt QuickSilver mid monos or an Aric Audio 60 watt push pull. Both amps worked best with KT150 tubes to really make the speakers come alive. Leaner sounding dynamic speaker cables helped squeeze a lot of detail out of the beautiful rich midrange.
op needs to be clear, which harbeth, how big a room, how loud to play?

it matters
I use the P3ESR with Quicksilver 70 watt amps with KT88 tubes. I have used the same amps with the M30.1 and the C7s!
@jjss49 

Yes, everything matters. I am curious about what everyone is using and their experience. 
My curiosity starts with about 35wpc and C7, for example. While listenable, they don’t seem to come alive even at low to medium volume in a 14x16 room. 
I think Harbeth benefit from more power than people think regardless of amp type. I’ve owned C7, 30,1, 40.1 and have friends who own and love them (as I do). 
My hopes of using relatively low powered tubes is probably not realistic in my case. 
I remember visiting someone with a pair 40.1 using maybe 15wpc of 2A3 push/pull tubes and it was glorious with fairly simple music.

 I know posts disappear on the Harbeth forum with talk of tubes and power, etc. so I wanted to see what you guys were using. 
I'm currently using Harbeth P3ESR XD speakers along with my Allnic T-1500 Integrated 300B tube amp, 12.5 watts per channel. Sounds very good, I also use a pair of REL T7i subwoofers with all my speakers.
My Harbeth Super HL5 Plus started in my main system with 180 WPC Rogue Audio M-180 tubed (KT120) monoblocks.  They're now in my office with my Audio Research VSI55 50 WPC tubed (6550) integrated.  They sound great with "only" 50 watts, although I rarely play them loud in my office.
I like where this is going, thank you. Please keep it coming.
correct joe

few things to bear in mind w c7’s or super 5’s

harbeths are 6 ohms, dipping to 5 in 100 hz area roughly - need to use 4 ohm taps not 8 ohms on tube amps - very low powered units, single ended, 300b etc etc need not apply unless you are near-fielding

you have decent sized room... i suggest a tube amp with more beef - i have had great luck w primaluna hp, audio research with 4 power tubes per channel, the like... 70-80 wpc range will move and grip the woofers suitably

compact 7 errs on side of warmth, potential bass boom/muddiness, that is why many who want tube sound use tube linestage or dac for that lil bit of magic but let a very good ss amp do the heavy lifting - hegels pass ayre van alstine all excellent

and yes alan shaw is quite the amp-nazi on his forum - hug is a take it or leave it proposition... i chose the latter - he is a good speaker designer but is close minded somewhat intolerant to alternate views to his own

good luck
I’ve had the C7 and used a Cayin tube integrated at 45 watts per channel. The speakers sounded great, never had to turn the volume beyond 12 o’clock. I now have the SHL5 anniversary. I alternate between the Cayin and a Luxman 505ux @ 100 watts per channel. The speakers are very happy with both amps.

@jjss49 

"harbeths are 6 ohms, dipping to 5 in 100 hz area roughly - need to use 4 ohm taps not 8 ohms on tube amps"

Can you elaborate on this. I've been under the impression that with 6 ohm speakers, the 8 ohm taps were appropriate. Very difficult to AB this.
   
I use SS but someone else on the forum who hasn't chipped in yet uses Linear Tube Audio Zotl40's in monoblock configuration on 40.2A's.
I use the 8 ohm taps with any Harbeth that I have used. I never heard any difference between the two taps! This is from Stereophile!
Harbeth P3ESR loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs’ MLSSA system and a calibrated DPA 4006 microphone to measure the Harbeth’s frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. Harbeth specifies the P3ESR as having a sensitivity of 83.5dB/W/m. My estimate was slightly less than this, at 83dB(B)/2.83V/m, but this is within experimental error of the specification. This is a significantly lower sensitivity than the norm, meaning that the little Harbeth will need a fairly powerful amplifier to play at acceptable levels in all but small rooms. However, its limited power handling (50W program) places a strict upper limit on the loudness it will produce. The Harbeth is claimed to be "easy to drive," and indeed, its plot of impedance magnitude and phase revealed that to be the case (fig.1). It is also an easier amplifier load than its predecessor, the HL-P3ES2. Other than a dip to 5.7 ohms at the bottom of the midrange, the P3ESR’s impedance remains above 8 ohms for almost the entire audioband, which will make it a good choice for use with tube amplifiers, provided they can swing enough volts to drive it to high enough levels. However, the shape of the impedance curve suggests that the balance will tilt up a little at the high end with such an amplifier.


with respect to which tubes, perhaps i should not have made my prior statement with such ’absolute-ism’ - it obviously depends on your amp and your room

most harbeths are nominally 6 ohms, dropping to just above 4-5 ohms in the bass region

my understanding is that tube amps typically have trouble delivering a lot of current (certainly compared to ss amps which happily double their delivered power into 4 ohms vs their standard 8 ohm load specs), thus the care needed in making a tube amp drive loads that are low impedance in nature... furthermore, low impedance is most common and hardest for the tube amp to deal with when it is in the bass region, where cone/motor motion requires the most energy (this current, given a specified voltage level) to produce the strong bass notes

the tube amp in turn uses its output transformers to ’leverage’ the voltage differentials developed by the tube circuit into current flow, thus the lower impedance taps provide more transformer windings aiding the amp do this when called for...

obviously, at the end of the day, the circuit theory and governing concepts need to work in practice... your amps may do just fine driving the little p3’s with its 8 ohm taps... it is worth trying both if your amp has both (my audio research ref 75 amp has 4, 8, 16 ohm taps for instance) - as they say, it is a ’free at home trial’

in my own experience with arc and primaluna tube gear i feel there is little better drive and bass control to my c7's or super 5's at the 4 ohm tap, but a little more sparkle and spotlit nature up top and through the mids at the 8 ohm tap - difference is slight in magnitude, but i believe i do hear it consistently
I have the 30.1's and drive them with an Audio Research GS-150 tube amp (155 watts/channel).  Also use a AR GSPre (tube pre-amp).
I’m appreciating everyone’s posts. Thank you, so much great information.
Sorry to chime in, because I don’t have direct experience with tubes and Harbeth...Only my Croft (hybrid) amp, which is 45 watts per channel. That has driven my (now sold) P3’s, and current C7’s. I have a fair size space...23 X 12 X 8 ft ceilings. The consensus is they like power, yet quite a few Harbeth owners are running low power. A friend runs a 22 watt SET with his 40’s, and loves it. I have not heard his setup. If I had the scratch, I’d love to try a mid/high power KT 88 or KT 150 amp. I’m in budget mode right now, so I’m thinking of the Belles Aria amp. My hope is more power will make the C7’s come alive. I’d also like to hear them with a Luxman 550 class A amp.
Harbeth SHL5+ with Mc275 tube amp and Mc c2500 tube preamp here. I’m  a lightweight in the audio world but have played around some and this is a great combination. Also have Harbeth Compact 7’s driven with a Luxman Class A 590ax and that’s a great sound as well. 
I own Harbeth 30.1's driven by a pair of Rogue Audio M-180 monoblocks (180wpc) with KT120 output tubes. After years of experimenting I have found my sweet spot.

As far as using the 4 or 8 ohm taps, I was told to try both and use the ones that sound better. Without getting too deep in the weeds, for me it was the 8 ohm taps and that's what I use.
30.1s with Rogue Cronus Magnum 2 (100wpc). Stock KT 120 power tubes with NOS Mullard in preamp stage. Have never come close to feeling short on power. Don’t think I’ve ever gone past 2 o’clock on the volume dial. 
Thx @twoleftears. This isn’t the first thread on this controversial question so do a search for my info.

I have the 40.2 Annies and I’m using Linear Tube Audio’s Zotl40 Reference amps monoblocked which is approx 90 wpc in 8 ohms. The tubes in each amp are a quad of NOS Mullard EL34 (EF2 from early 1960’s). Berning’s Zotl adjusts to the impedance of the speaker.

According to some I may be missing out on certain peak transients but given the music I listen to (and vinyl only), it wouldnt be much. Otherwise the combination is sweet, warm, beautiful and musical to my ears that I can listen to for hours without fatigue which was had been a huge issue for me.
The impedance curve for the 40.2 below. Impedance appears to be ABOVE 8 OHMS ALMOST EVERYWHERE, except for a slight dip below that value in the vicinity of 100Hz.  So some unscrupulous manufacturers would claim the 40.2, 40.2A, and now the 40.3 are a 12 ohm speaker, but given how these measurements are averaged its clearly an 8 ohm speaker so use the 8 ohm tap.

Regarding ease of drive the minimum impedance  of 8 ohms means that most if not all amplifiers will be able to supply the necessary current for a given power output level without difficulty.   Otherwise the modest 86db sensitivity and the ultimate amount of power needed will depend on the usual factors- average listening level, distance to speakers and dynamic range of the music listened to. 


https://www.inputaudio.de/wp-content/uploads/2015/06/harbeth_m402_audio_test.pdf
with respect to which tubes, perhaps i should not have made my prior statement with such ’absolute-ism’ - it obviously depends on your amp and your room

most harbeths are nominally 6 ohms, dropping to just above 4-5 ohms in the bass region

sorry about the typo in my post below - 

should read: 'with respect to which taps on tube amps to use...'
@aj523 would love to see that review translated into English, but have been unable to find it.
@pdreher 
Yeah sorry I had someone read part of it to me but most importantly the red line is the frequency response measured in axis, green is 10 degrees above, and blue is 30 degrees to the side (lateral).


I have SHL5+ speakers and used the Rogue Audio Stereo 100 amplifier (100 WPC).  
Amazing dynamic and powerful sound.  Much more powerful than my previous 100WPC cronus magnum II.  
Med/ large room.  
4 ohm tap sounded weak and anemic, 8 ohm tap much better.  
The Stereo 100 is actually more dynamic sounding that the amplifier I replaced it with, a Parasound a21+.  Should have stopped while I was ahead.  
most harbeths are nominally 6 ohms, dropping to just above 4-5 ohms in the bass region

my understanding is that tube amps typically have trouble delivering a lot of current (certainly compared to ss amps which happily double their delivered power into 4 ohms vs their standard 8 ohm load specs), thus the care needed in making a tube amp drive loads that are low impedance in nature... furthermore, low impedance is most common and hardest for the tube amp to deal with when it is in the bass region, where cone/motor motion requires the most energy (this current, given a specified voltage level) to produce the strong bass notes

There's a bit of myth being engaged in the quote above and it has to do with math.


4-5 ohms might mean that you have to use a 4 ohm tap on a tube amp. If 50 watts is needed to make a certain sound pressure at that dip in impedance, it will not matter what kind of amp makes that power, it will be the same sound pressure and the exact same current.


Put another way, the current needed to make a certain amount of power is the same, tube or solid state. So if it is making the power for that sound pressure, it **has** to make the current. Power equals voltage times current.


Tube amplifiers are different from solid state in that they don't double power as impedance is halved, but nevertheless they can behave as a voltage source. To do this they simply cut power in half as the impedance is doubled. This is one of the reasons why tube amplifier power is more expensive than solid state.


There is a product called the ZERO (www.zeroimpedance.com) which will allow any tube amp to deal with the impedance. So this is really about how much power is needed to do the job. IMO one of the better tube amps to pair with this speaker is the RM-200.


seems to me ralph that the issue comes from transient response

yes power equals voltage times current, but when much current is needed in a hurry to deliver the bass punch we want, it seems to me that is when tube amps with good transformers, properly leveraged by the tubes, and with a lot of power supply capacity can do better, all other things being equal

i thought it is the nature of semiconductors/transistors that allow them to react faster and also their ability to pass more current without strain or overheating -- once again, given good power supply capability they are gating...

separate question ralph - you make otl amps, how do you handle low impedance loads and are otl’s fundamentally better than transformer coupled tube amps? i think back to my experience in the 90s with fourier otls... man that was quite memorable, those 32 6as7’s lighting up all at once --- wow!!
I have 40th anniversary p3s I use with a Rouge st100 and Rouge RP 5 and with the exception of the kt120s both pre and main are using nos Mullard and tectronix tubes. The mullards adds warmth to the 40th anniversary from which I read can be a bit brighter then the regular p3s. Though I don't have direct experience or have listened the regular p3s so I don't know.
Even tubes can improve the sound of Harbeths with SS amps.  While I prefer the H360, H390, H590 with my 30.1's and 40.2's... I did try my Class D Audio (brand) SDS 470C amp yesterday, and found my Harbeths sounded about as impressive as with my Hegel H590. Though, I was using the Schitt Yaggdrasil R2R DAC (which is superb), and the Audio Research Reference 5se tube preamp - which improves the overall sound quality of the 470C. The benefits of this set up is you get the spacious, airy, holographic sound of tubes, but with the bass and mids control of a powerful SS amp.  

So... a class d SS amp, can drive Harbeths very well... if... you have the right class d SS amp driven by the right sources and preamps.

I should also note that I also have just tried my Audio Research Reference 5se tube preamp in combination wth the Audio Research Reference 150se tube amp driving my 30.1’s and 40.2s... and the sound is sublime.

While the bass slam and control is not as great as with the SS amps I noted herein - the details, air and holographic stage is a bit better, and the organic tone, tenor and texture of the sound is a bit better. And the bass may actually may be a bit more real sounding. Real live bass may not have quite as sharp leading and trailing edges as with the SS amps I noted.

Regardless - all of these amps sound superb with the Harbeths - which have impressed me more than I thought they ever could - being box speakers. They sound very much like Quad 57’s, but with more bass slam - which means with the right set up they sound as good as it gets!
M30.1 Here with Air Tight ATM-2 at 80w KT88.
try some Audio research and Primaluna with lower than 80w but prefer more above 60W.
Also prefer KT to EL tubes.
30.2/ 40th.  Luxman MQ-88uC 25 watts. Using the 4 ohm taps.  Sounds glorious in my small 12’ x 13’ room.  Fully treated by GIK.
My Harbeth C7 sits idle most of the time since I got Gershman Avant Garde. Occasionally I switch to C7 with Plinius or Audio Research SS amp. I think C7 works fine with 50 wpc solid state amp in a small room.
i thought it is the nature of semiconductors/transistors that allow them to react faster and also their ability to pass more current without strain or overheating -- once again, given good power supply capability they are gating...

separate question ralph - you make otl amps, how do you handle low impedance loads and are otl’s fundamentally better than transformer coupled tube amps? i think back to my experience in the 90s with fourier otls... man that was quite memorable, those 32 6as7’s lighting up all at once --- wow!!

Tubes and transistors are the same speed. Think about the fact that old tube color TVs had chroma amplifiers in them, one for red, blue and green, and had to have bandwidth from DC to about 10MHz. Although not exactly the same, the ability to make bandwidth and ’speed’ are closely related. Just FWIW, the output sections of our amps have full power bandwidth from DC to well past 30MHz. Its our voltage amplifier section that limits bandwidth (and done intentionally). In most tube amps, its the output transformer that limits speed.


Its good to have lots of capacity in the power supply of any amp- it can reduce IMD at higher power levels.


If the OTL and transformer coupled tube amps are on a load that is friendly to both amps the OTL will be more transparent and obviously wider bandwidth (and more speed). However low impedance loads don’t work for most OTLs although we make some that can handle low impedances just fine (the MA-2 and MA-3 in particular). But IMO/IME low impedance loads and heavy phase angles are not not good for any amplifier (tube, solid state, class D) because in all cases the distortion will be higher.


At least in the world of high end audio, keeping distortion down is paramount to obtaining smoother, more detailed, more transparent and overall more neutral sound. The ear converts all forms of distortion into some form of tonality; hence the brightness of solid state, caused by higher ordered harmonics and IMD. Distortion is also why many tube amps sound ’warm’; this is caused by the 2nd and 3rd harmonic. But if you play a solid state amp on a higher impedance speaker it will sound smoother and more detailed since you have less distortion. You might think that the low distortion of solid state amps as inaudible (this has been the myth for the last 50 years) but if it were we would not be having a tubes vs transistors conversation!


We handle lower impedances with our smaller amps by the use of an outboard device called the ZERO (www.zeroimpedance.com). But the funny thing is that even solid state amps sound better driving lower impedances if a set of ZEROs are used and this is entirely due to the fact that you are reducing distortion.


Class D amps have problems with low impedances too- its no worries doubling power as load impedance is halved; class D amps have the lowest output impedance of any amp made (our prototypes have output impedance of only a few milliohms). But they have filters at their output, and the quality of the filter is directly affected by the load impedance- many are designed for 8 ohms. But they too have lower distortion into higher impedances.


Since this is an issue for all amps, I really don’t see the point of the speaker being hard to drive! You need a lot of power, and finding an amp that is simultaneously high power and able to sound like music at the same time is a challenge! Plus you get thermal compression caused by voice coil heating- something that is not nearly so severe with high efficiency speakers, which is part of why the latter sound more dynamic. The speaker cables become hyper critical. Finally an easier to drive speaker does not have to take a back seat when it comes to distortion and resolution- often they have less distortion and greater resolution. It does get progressively harder to make deep bass with higher efficiency, but there are simple ways around that problem.


@atmasphere 

Does the zero add-on to an OTL amp basically then function as a Berning type ZOTL amp which provides that properly impedance-matched tube output stage to the loudspeaker? 
@aj523
In terms of getting a match to a low impedance load, yes.
I've heard my 40.1's and now 40.2A's with Primaluna and Cary tube amps and thought they made lovely music, but once I switched to solid state amps (LFD NCSE and now Hegel H590) I am much happier with the sound.  The 40 series speakers are hungry for power, and the two tube amps I mentioned did not provide this as well as the Hegel or the LFD.  
@atmasphere 

thanks ralph your perspective is very helpful!
My favorite Harbeth/Amp combo was SHL5+ being driven by an Air Tight ATM-2 amp. 

The Air Tight makes approx. 80W, I used a Lampizator Big 7 as a preamp and DAC. 

The most enjoyable sound I've had in my home. 
@jayrossi13

ahhh airtight atm-2 -- what a wonderful piece what a sound

need to get mine out play it again... kt88 magic...

has front panel input thru volume pot too... eliminate the linestage if single sourcing!!!
@jjss49 

The ATM-2 is really an amazing amp. I regret selling and would love to find another. 


IMHO, Best Harbeth sound from tubes came from a pair of MC 60s my PE upgraded according to scientific principles to take advantage of the wide bandwidth output transformers. 
FWIW. I think it helps a lot if you use the same brand preamp-amp particularly if going with tubes. Perfect synergy, zero issues, and  minimizes costly mistakes. 
@ivanj

Best Harbeth sound from tubes came from a pair of MC 60s my PE upgraded according to scientific principles to take advantage of the wide bandwidth output transformers.

"upgraded according to scientific principles" ...  whaaaa??? please elaborate ... hee hee hee