Speaker Efficiency

My understanding about this is that less efficient speakers drive your tubes harder. So, shorter tube life. But I can’t say for sure, maybe someone can comment on that point. 

Speaker efficiency is sensitivity

Not really! See article below page one sec C:

https://www.lansingheritage.org/html/jbl/reference/notes/tech1-3a.htm

Speaker efficiency is sensitivity + impedance vs phase angles.

It is not solely the sensitivity spec, which is why you can’t assume a 90dB-sensitive speaker will mate well with a moderate/low power tube amp. This is why you don’t often see Wilson or Magico owners using tube power. 

Low impedance drivers generally perform better than their high impedance counterparts. They require more from the amplifier, but if the amp is up to the task, the speakers will perform better and have greater dynamic range. This is why the large ultra-high-end speakers in the $30K^ range almost always have a low average impedance. The only exceptions might be those with unconventional bass loading and compression/horn drivers. This isn’t to say all speakers with a low nominal impedance are “high-end.” Many low-nominal speakers have 8-ohm drivers, but the combination and number of drivers coupled with complex crossovers lowers the speaker’s average impedance. This is why it’s not uncommon for a <$4K tower speaker to have a 4 or 6 ohm nominal rating when in fact all its drivers (excluding the tweeters) are 8-ohm. 
 

All but very few speakers have impedance swings that will result in non-linearity when coupled with tube amps. The exceptions are rare. One reason tube amps are so popular is because the typical speaker load will result in a boost of the midrange and upper bass frequencies. It makes them louder and thus often results in the false perception of greater resolution and power delivery. It’s why you’ll encounter comments on the forums from Joe Schmo who claims his 20 WPC tube amp sounds more powerful than his 100 WPC solid state amp.  The reality is 20 watts is 20 watts, and Joe just hasn’t cranked the volume quite enough for the compression to become obvious. And since tube amps “soft clip,” when overdriven, the sound flattens before it becomes obviously distorted. 

@marktheshark wrote:

I have been listening to my Decware 300b tube amp for a few months now. At 8 watts, I have them paired with Klipsch Forte IV at 99db efficiency, and this set up has been sounding great. This morning I connected a pair of Sonus Faber Electa Amator speakers, 6ohms at 88db of efficiency. They sound fantastic, with more weight  and depth. I understand there is a huge price difference in the two speakers, but aside from that, if I am getting 80db of volume at my chair, 8' away, what is the draw back of using lower efficiency speakers with SET amps, so long as the volume is sufficient? I did notice turn the Pre amp, the tube amp and the Roon volume towards the highest setting, it starts sounding terrible....

There's the pragmatic approach that holds that if sounds great (i.e.: better) to your ears with an 8 watt SET amp to 88dB sensitive speakers in most any situation you can throw at it, then that's all that matters. 

I'd tempt that approach though by saying that such an amp/speaker combo defeats the purpose of the SET in particular; such an amp, to be its best, should be used using only a fraction of its output power to take advantage of its low distortion here, and for that you need high efficiency speakers (i.e.: no lower than honest ~98dB's) - preferably high impedance load. I would also be cautious about your 80dB listening level number as an indication of the actual load presented to the SET amp - at the listening distance, that is, with the particular speakers. You may well be running the amp closer to its ceiling than you might believe. 

@deep_333 Funny, :)

Ok, I did just that. Hildur Guðnadóttir 12’ away, at 85db, the "fleawatt" was at about 75%, the Roon app was at 80%, if I had to guess, I was probably running at 2, 2.5 watts. My room is 14X20 with vaulted ceiling. I didn’t hear any problems with the signal, although the room was shaking, and the dog ran like hell :0. But the real question is, why? You cant honestly listen to that soundtrack at 90db and enjoy it. I do like Schiit stuff, I’ve had Yiggi and Bitfrost DACs, I dont need a 200 watt Schiit Tyr to drive a pair of Forte’s? I do have a Hegel H590 (2 x 301 W into 8 Ω, Dual Mono) for the Sonus Fabers, maybe I’ll do a comparison.

 I have been listening to my Decware 300b tube amp for a few months now. At 8 watts, I have them paired with Klipsch Forte IV at 99db efficiency, and this set up has been sounding great. This morning I connected a pair of Sonus Faber Electa Amator speakers, 6ohms at 88db of efficiency. They sound fantastic, with more weight  and depth. I understand there is a huge price difference in the two speakers, but aside from that, if I am getting 80db of volume at my chair, 8' away, what is the draw back of using lower efficiency speakers with SET amps, so long as the volume is sufficient? 

It comes down to your choice of music as well. Here.. listen to this track by Icelandic composer, Hildur Guðnadóttir to check bass control and so on of your drivers. Turn subs off and just crank the speaker up to about ~90 db (Don't be shy, our good lady, Hildur is merely here to check for a minute if your stuff is any good or not). Compare back to back with a pair of Schiit Tyr Monoblocks and the Decware weak sauce fleawatt on the Electa Amator. When the Decware cries and runs to its daddy, i.e., fizzles out, i predict that i will see it on the Audiogon marketplace for sale real quick. 😁

https://www.youtube.com/watch?v=B7sj_XJJ9U8

But, If you are listening to some weak sauce track with a  twangy dude wailing to a single string at 65, 70db about how a gal broke his heart into just a few million pieces..... i suppose your Decware should be just fine with the Electa Amator.

@paradisecom  Looking at all the great information provided above, if your 6watt amp can provide 70db with 85db speakers, and your not on the higher end of the volume control, your probably not taxing the amp too badly. Continuing to play at louder and louder volumes, would create more distortion, and sound quality would diminish. Higher efficiency speakers would work better with the Decware amp, and should have less distortion on the signal, and overall could sound better.  If this is an office system, you probably don't need 40 watts.

I'm not sure whats out there for high efficiency bookshelf speakers, but if your system is in your smaller office, you may not need to be in the mid to high 90db range.

These are interesting, albeit expensive

https://devorefidelity.com/devore-fidelity-speakers/orangutan-series/micr-o-speakers/

@marktheshark I'm looking at the same crossroads for my office system.  I'm running a lower-powered Decware (rated at 6wpc) that sounds great with both sets of speakers I rotate through.  My bookshelf speakers are rated at 85dB, but sound fantastic and I usually listen at 65-70dB with the occasional listening in the 75-80dB (max) range when my wife isn't home.  I'm looking at experimenting with some more efficient bookshelf speakers, perhaps some Omega's, or moving to a 20-40 wpc tube amplifier.  I do have a subwoofer and this is a smaller space measuring only 12x11, plus I only sit about 8' from the speakers.  

So essentially I'm just wondering if there would be any improvement with a more powerful amplifier, or more efficient speakers, or both!  

Clayton is no longer at Spatial.

I have no idea why that amp didn’t work. On paper it was a great match and the Decware drove a pair of khorns like there was no tomorrow.

@ozzy62 that's interesting. I had a pair of Spatial M3's fed by a Parasound Halo amp. The clarity was amazing, even at deafening volumes. I don't play my systems that loud anymore. I sold the M3's and the amp to a buddy, and he has it set up in well treated room, sounds fantastic..... I miss those speakers.....

If I were to go in that direction, I would certainly talk to Clayton at Spatial.

Thank you @perkadin . As I sit listening to an Oscar Peterson LP, I agree the Forte's a great match for the 300b. The La Scala's would be wonderful in this room, but man the are beasts.

I’d be careful matching fleawatt amps with Spatial speakers. I had the x3 with powered subs and 96 db. You would think, easy to drive? A Decware Torii II @ 30 wpc wasn’t up to the task.

@marktheshark I think you already have one of the best speaker matches (Forte) for the Decware. As others have mentioned, thanks to the ambiguity of speaker sensitivity ratings (adjusted for impedence? echoic vs anechoic?) many speakers measure far below their rated spec, Klipsch Heritage lineup included. However that said, the Heritage speakers are still among the highest sensitivity speakers I’ve seen independently tested. The Forte IV reached 95.2, and the larger models hit 98+. The o/96 was measured by Stereophile at 91db. The 98db efficient AN-E Lexus Sigs? They measured 92.5. Still good, but the dropoff from the Forte will be noticeble with only 8 watts on tap, and if its my money I’d look at La Scala’s first. They smoke the Devore & Audio Note at that price point. The only one on your list that’s interesting to me is the Spatial and that is a different sound altogether. You’d need also need a higher powered push pull design or SS amp, along with the space to make dipoles work. Lots of changes you might not have anticipated.

Marktheshark Thank you for this thread. It also gives me more understanding how amp react to the speakers.Mikelavigne thank you for the link, It helps .

Thank you @audioman58 , I like the Decware 300b, so that's not going away. I would not leave the Sonus Faber's on that amp, it was more of an experiment, and that prompted my post. I certainly have a better understanding of speaker matching with all that has been written here. Regarding the Forte's, I like them, the pairing sounds very good. I'm sure upgrading the Forte's could result in a better sounding system, but what is the "cost / reward" ratio ?

Roadcykler, when I wrote that post Iam thinking about my viva 22 w , and my Andra  1 ? I was not able to to get the dynamic I want. 

@hotei Wrote:

Then why even make speakers in the 80db range if higher impedance is better?

One reason a four Ohm speaker will play louder then an eight Ohm speaker. See my post above. 😎

The video below explains impedance and the differences between efficiency and sensitivity.

Mike

https://www.youtube.com/watch?v=DNfpYncOQRc

I am using a 300B amp to drive Klipsch LaScala IIs. Of course the LS II is one of the highest sensitivity speakers one can buy, but I can drive them with 9 watts to levels greater than I can stand in a 400 sq. ft. room. I can listen to any genre of music to great effect,  no loss of volume, dynamics, or bass control.

@knotscott My current setup will remain as it was. The 300b amp with Forte's in the living room, with Dac. The Sonus Faber's in the bedroom with a Hegel Integrated and turntable. I agree, I love the sound of the Electa Amator's, and they look really nice, so the wife doesnt mind them in the BR.

    I'm spending the weekend swapping components of the two systems around out of curiosity. I do think at some point I may swap out the Forte for another speaker. @mapman suggested fritz, they are very interesting, and not hugely expensive. I have also listened to Devore, Audio Note, Spatial Audio, Zu Audio, all seem like a good match with the Decware amp. maybe even a Decware Speaker.  

@bigkidz I agree, the less expensive amp, may sound better depending on all other parts of the system. Trying to compare a myriad of components, matching speakers, down to the minutia of cables, cartridges and tweeks can be daunting. I listened to Devore O/96 this week at dealer and they sounded excellent, but this was a well treated room, with very expensive Dac and amplification. I thought, how would these speakers actually sound in my mediocre room, with my equipment?

Then why even make speakers in the 80db range if higher impedance is better? 

I have moved from 87 db on 94 db speakers. Much much better , also for the amp.

Obviously all parts of the system chain make a difference, but few make more difference than the speakers. Especially how they interact with the room and present a soundstage.

If you love the sound of the Electa Amator speakers, I’d look to get bigger tube amp. Even if it’s PP vs SET, there are some great sounding PP examples that would drive the Amator to the desired sound level.

On a side note - Not sure if you're running a sub, but a well setup pair of smallish active subs could be a nice pairing with your speakers/system.

Raise your hand if you're just repeating what a dealer told you to sell you a more powerful (and more expensive) amp?

I have a 300b Amp driving my Forte and it is a great sounding combo but it will run out of steam if you push it....which I don't.   The sweet spot for those amps are a few watts, not their full rated power.   

Those same speakers will play considerably louder with my Quicksilver. Amps that are 40 watts but they lack that beautiful tone that my WE 300bs have.   

I have a pair of Sonus Faber in my bedroom powered by a 40 watt Cyrus Integrated Amp.   That Amp drives the SF easily but being 85 dB sensitive they aren't the best match.  Again, they sound great until you push them.   Those are being replaced in a few days with Omega speakers that have a sens of 94.5 dB / w and should be a better match.    

I like low power amps but it limits your choice of speakers.   A lot.   I could see where Forte and a 300b amp would not be a good match,  it's not a lot of power and could be a problem with large rooms especially if the owner likes to crank it up.  Those amp's "forte" is awesome tone, not  high volume levels.

So much goes into the design of an amplifier.  Transformers, power supply section, parts selection, etc.  Audio Note, V-Caps, point-to-point wiring, copper chassis, etc.  Then there is the implementation to reduce the noise level.  In typically lower priced amplifiers, there are limitations based mainly on those factors.  Mid-range may sound fantastic but the overall bass and high end extension are limited.  Most people don't here the limitations until they have a direct comparison from something that is not limited in sound reproduction.  Just spend a day at a local dealer and we were discussing this within the various brands of manufacturers he offers.  Even between the lineup of some manufacturers you can hear the transformers influencing the sound and not always the more expensive unit was better.

Good into here though.

One thing I forgot Tom mention ,on efficiency of the speaker, Klipsch forte say 99 db actually closer to94-95 db efficiency 

the Sonus Faber you say are 88 DB efficient , for every 3 db it takes 50% more to get to the same volume level  ,the Sonus Faber take over 100%  more amplifier energy to reach the same volume level. Buy a SPL meter on Amazon for maybe$30 for a decent one to know exactly the db you are using ,

then at what db when the amplifier most likely is over driving and Transformer 

saturation is causing it to distort. Either upgrade the Klipsch ,or buy a much bigger amplifier,  the Quality and size ofthe transformers means Everything 

if you want excellent quality without major league pricing, Lookup 

Radu Tarta , one ofthe best custom Amp,preamp designers in all NorthAmerica , he uses Quality like Lundahl chokes and Transformers  , in the  decware a smaller type lower quality , Radu has built several Amplifiers and  preamps for myself .

not cheap but built to last a lifetime he is the-best especially SET amps

which are 8 watts ,or a class A parallel feed using4  power tubes you can get 18 watts . All depending on your plan and budget. Much more$$ though 

for sure though the SF speakers Waay underpowered.

You may have a low quality alps volume pot ,just look it is a round silver can it is only 2 wipers with a contact spray , once it gets past a certain point it can start loosing resolution , where a resistor ladder type ,or rely much better ,also 

for that speaker the Sonus Faber go down to under 3 ohms you need much more power then that ,the Klipsch are a good fit ,I rebuilt a bunch Klipsch speakers 

the stock internal Xovers are very low quality ,even crites  Xovers which were in it 

not that great the Xover is the ♥️ of the speaker ,having owned a Audio store 

and modding my own Xovers and others for years ,,if you plan on keeping the Forte 

then I highly recommend doing this even theForte 4 cheap Xover parts , once upgraded sounds much more detailed and refined in another league.

the Sonus Faber too could use better Xover parts just unscrew the Bass driver , and look inside , Thst speaker needs a EL34  pentode amplifier .

please remember if pushing a speaker peaks can hit 10 x  more on peaks ,that’s why it’s so e important to match the amp to the speaker .

@OP - typical 300B amplfiers start to distort above the couple of watts of their rated output.  80dB is pretty loud so, at least on peaks, you will be hearing large amounts of harmonic distortion. As the distortion products are musically consonant, you may not find them objectionable. However, every 300B amp I've ever heard does sound very compressed when driven hard, albeit that this tends to be most noticeable with full range speakers where the most obvious effect is a loss of impact and control in the bass. However, if you like what you're hearing from the combination, then all is well.

@jayctoy "Mark the 8w will not work on 88db on loud volume.."

A speaker with that efficiency will play at 88 dB with ONE watt. How loud do you think it would be with 5-6 watts? What? I can't hear you over the extremely loud music!.

I'm thinking that unless the room is huge, 80 db in the listening chair is nowhere near full crank.

Amps, and especially tube amps, do not perform sonically optimally as they’re pushed more toward their limits.  But, that said, if you had the volume knob pretty cranked and were still enjoying the sound maybe that amp even working sub-optimally still works for you.  Follow your ears. 

@mapman Wrote:

Oh it will work. Almost any pairing will “work” and make sound. It might even work well enough for some in some cases. But the pairing will never bring out the best in either component.

Exactly!

@marktheshark Wrote:

Typo, the Electa Amator is 4 ohms at 88db

That means the speaker is getting two watts not one watt. I.e. Sensitivity @ one watt @ one meter @ eight Ohms =88 dB SPL @ four Ohms= two watts for 88 dB SPL @ one meter. In other words, your speakers are getting two watts from the amp not one to get 88 dB SPL @ one meter. Also, any amplifier driving lower impedances = higher distortion.😎

@mikelavigne Wrote:

i’m not always the biggest Harley fan with his tendency toward hyperbole.....but in this case he nailes it. a quick read worth your time.

I agree!

Mike

@mikelavigne wrote:

i’m not always the biggest Harley fan with his tendency toward hyperbole.....but in this case he nailes it. a quick read worth your time.

I fully agree - on all mentioned. 

When you mentioned 80db at your listening position I’m assuming you mean peak not average, which isn’t all that loud.  The power needed to increase volume is logarithmic, you can still get to relatively loud levels with low power.  Tubes also soft clip so it could be cheating to get to 80 and you might not even notice.  Try hitting 90 or 95 db peaks and you’ll quickly realize why you originally had them paired with the Forte.  I’d also be much more concerned with damaging the speakers then the amp.  Clipping of any type is not good for voice coils.  I’ve paid to replace a few drivers once.  Learned my lesson.  Be really careful with low wattage amps.  They may have sounded great at the time and then you come back the next day and certain songs don’t sound quite right.  Then comes the fear and panic. It’s not pleasant. 

If the source has large and sudden dynamics, when low powered amp is driving lower sensitivity speakers, and they are lower impedance speakers (a hard combo for any amp) the amp will not have enough reserve to supply the juice to the speakers for the dynamics, especially bass which is the most power hungry frequencies.

My Office System: My Little Luxman Tube Integrated:10 wpc at 6 ohms

https://www.luxman.com/product/detail.php?id=33

is driving Vintage AR-2ax, 91.5 sensitivity at 8 ohms.

https://stereonomono.blogspot.com/2014/05/acoustic-research-ar-2ax.html

very nice combo, however I need to turn the volume up further than most amps I have owned over the years, and while enjoyable volumes are produced, I would not expect great dynamics out it this combo.

Previously, driving Wharfedale Diamond 225’s, sensitivity 87db at 8 ohms

https://www.stereophile.com/content/wharfedale-diamond-225-loudspeaker

the Luxman Volume had to go even higher.

It also sounded good in this room, but you have to know/acknowledge the limitations.

I bought the AR-2ax for nostalgia for my Garage/Shop system (I had them in college).  they sounded soooo good, I moved them to my office, gave the Wharfedales to my son, and bought a 2nd pair AR-2ax that I am restoring for my Garage/Shop system.

AR gives some power formulas here, page 12, magnify

https://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_brochures/acoustic_research_loudspeak.pdf

Oh it will work. Almost any pairing will “work” and make sound.    It might even work well enough for some  in some cases.  But the pairing will never bring out the best in either component.  

People who believe everything they read will tell you it won’t work. Of course they love to read manufacturers literature where the OEMs have to satisfy every customer including the teenager who wants to play at 130dB.

If you listen at 80 dB, you’ll be fine. Realize you won’t be able to turn it up to 100dB when others come over, and I’m fine with that.

That said, I much prefer the higher sensitivity (not efficiency, sorry to have to correct you) speakers. I have 96 dB sensitiveity non-horn speakers with very linear response and I think that’s about as good as it gets...

...sitting here listening to my 2 wpc decware amp.

I will add that before you invest in this speaker listen carefully to make sure you aren't missing something.  For example, sometimes people hear a wonderful midrange and forget to check for bass and dynamics, the first two things to suffer at lack of power, lack of current, lack of power supply, bad power cord, etc.

Jerry

@mikelavigne   hmm,  sounds like impedance curve has a an equal of greater effect than just speaker sensitivity. @mapman had mentioned Fritz Speakers (thank you mapman). Looking at the Fritz Carrera, with a sensitivity rating of 87db, but recommended watts is 5 to 200. Thanks for the Harley article, I'll read it this weekend.

what are you gaining? and what are you losing? when you put a low powered mismatched amp to a hard to drive speaker????

how large is your room? how loud do you listen? how close do you sit? how important is space and scale and the lowest octave? how flat is the impedance curve of the speaker?

here is a very concise article "Lies, Damn Lies, and Speaker Sensitivity Specs" written by Robert Harley in the Feb 23’ Issue of Absolute Sound regarding speaker efficiency. how specs can be misleading, and how it affects amplifier<->speaker matching. it’s a good place to start this conversation......

https://www.enjoythemusic.com/The_Absolute_Sound/02_2023/editorial.htm

i’m not always the biggest Harley fan with his tendency toward hyperbole.....but in this case he nailes it. a quick read worth your time.

Guys, thank you for all the Info. I think the Amator's are going back in the bedroom :)

@marktheshark of the sound is listenable the amp may be running hotter than optimal and producing more distortion. The volume attained and dynamics will level out. It’s like running a car engine. It’s always best to not make the engine work harder than it is designed to do for best results and longest life.

With flea power amps you will get the best results with speakers that are easy loads to drive in terms of impedance. The if they are also efficient they can go louder and clear as well.

I have looked at Fortes. Personally I would not chose them for a SET and expect best possible sound quality.

If you do not have to go very loud, I would recommend investigating Fritz speakers . These are generally designed to have benign impedance curves but are also monitors and efficiency is very modest. I have heard these at shows with flea power tube amps and was astounded with the results in a modest size room at least. Larger rooms are always a greater challenge but even in case adding a powered sub or two along with an active crossover to limit bass extension in the mains can address that

@mapman thank you, that makes sense now.

So, at 8 watts, into 4ohm 88db speakers, is the amp being damaged at playing 70db room volume?

Clipping is an amp thing and always associated with too little power not too much. Clipping means the amp is overdriven. Too much power can overdrive speakers and damage them but that is not “clipping”.

SET and most tube and Class D amps soft clip which is an advantage.  It’s an easy And informative google search to read up on clipping and how it works. 

Typo, the Electa Amator is 4 ohms at 88db

@ghdprentice  I agree, 80db is loud. What is the limitation? If the speakers are rated for, lets say 100 watts, why is the sound degrading at such a low wattage? I can see putting to much power into a speaker and it clips, but this is the opposite.

Distortion with SET amps in particular goes up quickly . My understanding is it’s best to not overdrive them which can happen easily with harder to drive speakers. Efficiency and how hard to drive are not the same thing. Efficient speakers may go louder but if impedance is low especially at lower frequencies they can still be hard to drive properly. The result is distortion. Set and tube amps both soft clip and introduce less offensive orders of distortion when overdriven so things may still sound very listenable and even good in some cases with some recordings.

But bottom line you never want to overdrive any amp for best results . Flea power SETs are the most easily overdriven.

limits dynamics

Probably none.

If it were solid state amps you would probably hear a big difference. Solid state amps are so fast to react and sound very bad when they run out of current. I have a friend with a Pass amp kit… 8 wpc. Sounded great until any volume and then sounded anemic.

80db is pretty loud. My average listening is done between 65 with peaks to 75… seldom more.

Yes the Amator is a great speaker. Of course, more power would likely result in even more dynamic sound.

Mark the 8w will not work on 88db on loud volume..