Basic question about sensitivity

Could impedance and sensitivity be getting mixed up somewhere?

@immatthewj Wrote:

 

Basic question about sensitivity

See article below:

Mike

I think, in general, the way you are looking at things with more sensitivity requiring more power is correct. I think Harbeth are somewhat of an anomaly.

Like all things audio, it depends. Recommended wpc amplification is a very open and unscientific… well recommendation. It can be as much marketing as a real requirment.

The nominal impedance of the Harbeth P3ESR XD is 6 ohms. Which they advertise as “easy to drive”, since many speakers with a sensitivity of 83 are very hard to drive, requiring a lot of power and having impedances dipping down to 2 ohms or lower. The impedance is a measure of easily electrons flow through… and at 2 ohms they flow easily, and if the amp can’t produce tremendous current then it runs out of power.

Also speakers are rated at nominal impedance… because they vary across the audio spectrum. So, some speakers dip to 1 ohm, then go to 8 or more ohms… the nominal impedance could be almost any thing. The electrical characteristics are so much more complicated that these two parameters show, they tell very little with certainty.

A better measure of amps is current… and for speakers the lower the impedance the more current they need to perform properly.

I never look at the power requirements and when purchasing solid state amps I have generally purchased amps of far more than the recommended power rating because they tend to sound better. Tube amps are not nearly as likely to show that they are running low on power.

I choose amps for their character and make sure they have lots of power… regardless of speaker. If you choose Harbeth, you are choosing a specialty speaker and should research amplification carefully.

Higher efficiency = easier to drive.

Higher sensitivity = more output at given voltage.

When the speaker is 8 Ohms, efficiency and sensitivity are the same.

Here’s a common example: Many mid woofers come in 8 ohm and 4 ohm versions. Nearly identical in all other aspects besides the impedance curves. The 8 Ohm version produces 87 dB at 2.83 V. That is, 87 db @ 1 Watt. The 4 ohm speaker produces 90 dB @ 2.83V, but since it has 2x the current it is 90 dB @ 2 Watts.

Generally speaking though, it’s hard to find high sensitivity speakers ( 97 dB or higher) that are not also benign impedance (8 Ohms or better).

To make it easier on you, keep an eye on "minimum impedance" not "nominal impedance."  Higher minimum is (generally) easier to drive, and the sensitifity/efficiency will tell you how loud it will get with your amp.

Higher efficiency = easier to drive.

Higher sensitivity = more output at given voltage.

When the speaker is 8 Ohms, efficiency and sensitivity are the same.

@erik_squires , thank you. The Monitor Audio Gold 300 5G (sensitivity 90) minimum impedance is stated to be 3.5 ohms, which would then explain the need for more power.

@ghdprentice , thank you; I am curious, when you refer to the Harbeth as a "specialty speaker," what do you mean by that.

Thank you for responding @ellajeanelle , no, I wasn’t confusing impedance with sensitivity; however I was not understanding the relationship between the two.

@ditusa , thank you for the link. I read through it quite quickly and it does appear to be quite informative. I am going to give it a careful thorough read.

OP,

You know, that is a great question… since they sit off in a niche to me, they are unique sounding. So, I had to ask that question. So, I did some research. I think in the process… came to the realization that the Harbeth claim of “easy to drive” may be more marketing hype than anything. Bard summarizes:

There are several reasons why Harbeth speakers are considered a niche speaker:

1. Limited Production: Unlike many mainstream speaker brands that mass-produce their products, Harbeth maintains a commitment to small-scale production. Each speaker is hand-assembled and inspected in their UK factory, ensuring high standards of craftsmanship and quality control. This limited production contributes to their exclusivity and appeal among audiophiles who appreciate the difference that handcrafted products can offer.

2. Unique Sound Signature: Harbeth speakers are not designed to cater to the broadest possible audience. Their distinctive "voicing" emphasizes a warm, smooth, and mid-range focused sound, which may not appeal to listeners who prefer a more neutral or analytical sound signature. This specific sonic character attracts a dedicated following among those who appreciate its natural and musical qualities, particularly for listening to acoustic genres and vocals.

3. Focus on Quality Over Technology: While many modern speakers incorporate cutting-edge technology and features,Harbeth prioritizes traditional construction methods and high-quality materials. They remain committed to using thick MDF cabinets, hand-built crossovers, and time-tested driver technologies. This focus on essential elements may not resonate with listeners who prioritize the latest technological advancements, but it appeals to those who value the enduring qualities of craftsmanship and classic design.

4. Specific Amplifier Requirements: Harbeth speakers have a nominal impedance of 6 ohms, which can be a challenge for some mainstream amplifiers. These amplifiers may not deliver enough current to drive the speakers to their full potential, potentially resulting in a less dynamic and detailed sound. This requirement for specific amplification options limits their accessibility to a broader audience, but it also attracts audiophiles who enjoy the challenge of pairing their speakers with compatible equipment to achieve the best possible sound.

5. Price and Value: Harbeth speakers are not inexpensive, and their pricing can be considered high compared to mass-produced speakers with similar features. This can be a barrier for entry for many potential buyers. However, for audiophiles who value exceptional build quality, unique sound character, and long-lasting value, Harbeth speakers offer a worthwhile investment. Their focus on quality over quantity ensures a superior listening experience that justifies their higher price point for dedicated music lovers.

Overall, Harbeth speakers occupy a niche within the speaker market due to their unique combination of traditional design,specific sonic character, high-quality materials, and limited production. They cater to a select group of audiophiles who appreciate the craftsmanship, musicality, and long-term value that they offer. This niche positioning allows them to focus on their core strengths and continue producing exceptional speakers for discerning listeners who value a truly special audio experience.

A singular focus on a particularly poorly crafted specification, in this case one that includes trash aka distortion as output, is not a wise pursuit. Easy load with low distortion ( breakup, frequency response, impulse, time and phase ) would be laudable.

@ghdprentice and a cabinet that contributes to….. output…not present in the…. input

4. Specific Amplifier Requirements: Harbeth speakers have a nominal impedance of 6 ohms, which can be a challenge for some mainstream amplifiers. These amplifiers may not deliver enough current to drive the speakers to their full potential, potentially resulting in a less dynamic and detailed sound. This requirement for specific amplification options limits their accessibility to a broader audience, but it also attracts audiophiles who enjoy the challenge of pairing their speakers with compatible equipment to achieve the best possible sound.

 

Thanks, @ghdprentice , I am running a Cary V12 which is switchable between 50 wpc triode and 100 wpc ultralinear. I am currently running it in triode, and honestly, I do not think I would want to pair it with anything that I could not drive in its triode setting.

and a cabinet that contributes to….. output…not present in the…. input

@tomic601 , can you expound upon that?

OP,

I have Audio Research 160 amps. They operate either 140 wpc ultra linear or 70 wpc triode. Although the sound output is hardly different between the two… the triode mode is more musical to me. I have paired this amp with 90db sensitive Sonus Faber Amati Traditional speakers. Works great at any volume. 
 

Your Cary amp sounds great. If I were you I would want to hear the combination before committing, 

A cabinet that contributes to output is one that moves or is not inert. This can be seen in the waterfall chart. The cabinet is storing and releasing energy after the driver has reproduced the input. Some people like that.  

in the general context of my comments, i wouldn’t overly focus on a single specification or measurement. @ghdprentice had it right by advocating for hearing a particular speaker of interest w your amplifier.

The EPDR measurement used by Hi Fi News and Stereophile gives a better indication of how difficult a load a speaker will present to the amplifiers.

The B&W 800 series are a good example of speakers that are relatively efficient but difficult to drive.

I am currently driving a 4 ohm, 96 dB speaker with a 2 wpc SET.  

Sensitivity is the efficiency of the Loudspeaker . Having modified alot of Loudspeakers ,the size can have something to do with it as well as drivers and 

most of all the Xover  and how complex it is. It’s always better to have more power ,

for in transients if youare playing loud peaks can go up 10 times that for 

a short fraction of a second and the amplifier can clip or distort which isnot good forthe drivers if a speaker says15 watts that’s minimum it is not full range 

and too what is the speakers capability ,in bass ? Many companies stretch the truth  there is no standard ,a speaker can say 38 hz but it maybe at + or -  6 DB which in truth speakers start to roll off earlier then the rated specs ,a good review will show 

a waterfall plot in how linear it is , I was watching and reading a Perlisten speaker review. They are very linear ,not many dips at all  , that’s why allways buy quality 

and as much amplifier you can afford to have overhead , more so if you are playing 

constantly over 85 db spend $30-50 on a good SPL level meter to see how loud 

you are playing . I have a Dynaudio speaker it says 87 db But it can dip down to 3 ohms which is pretty demanding I have shut down a 100 watt amp and my speakers are a 4 ohm loud I went to a amplifier that doubles it’s rating 150 8 ohms 

300 wpc at 4 ohms .  

on highly sensitive speakers, you can blow on your glowing tubes and hear wind from speakers, but on the good side all you need is quarter watt. 

On my experience, the size of the room & the volume you like to listen at have a huge impact on how much power you need for your speakers as well as their sensitivity. If you think about, the word “volume” applies both to the amount of db a speaker outputs as well as the cubic footage of the room. 
 

As Audioman58 pointed out, musical peaks,  both in the bass & lower midrange, can can easily demand 5- 10 times instantaneous peak power. I listen regularly in a large room ( over 6000 cubic feet) at volumes in the lower yo mid 90’s db’s & my 98 db sensitive Volti Rivals are barely using a few watts as indicated on the watt meter on my amp but when a loud peak comes, that can jump to 20 - 30 watts for a split second. 
 

Btw, I’m sure many of you folks are not horn loaded speaker fans but if you like your system to easily boogey on any kind of music & sound rich, detailed & not hard without really breaking a sweat, check out Volti’s! As Greg Roberts says - “have fun!”. 

OP,

Thank you for the question, I have had the same thoughts. I have four speakers:

(1) Thiel CS 2.3 - 87 db at 4 ohms

(2) Old school 1980s Infinity Reference Kappa 7s - 88 db at 4 or 6 ohms (don't understand the two values there)

(3) Buchardt Audio S400 MKIIs - 87 db at 4 ohms

(4) Clayton Shaw Caladans (on order) - 93 db at 4 ohms

I've never really understood the relationship between sensitivity and impedance, and how that translates into "easy or difficult to drive". Furthermore, how does that translate into the proper speaker cable: length, type of material, cable gauge, etc. It's never been an issue for me (that I've noticed), as I never listen to music at LOUD volumes....though I'm sure there is more that I should be paying attention to.

Also, why have I been drawn to the sound (except for the Caladans which I have never listened to in person) of 4 ohm speakers? Is it chance, or something more to it than that? It would seem on the surface, that I've ended up with speakers that are not the easiest to drive

It simply means that at one watt of power a speaker will produce the given amount of decibels. A flea watt amp will drive those Harbeth’s just fine, but it may not get loud enough to work in larger rooms.

@immatthewj,

Speaker sensitivity and efficiency are related, but not the same. See article below page one sec C:

Mike

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

Thank you to all for the informative responses.

@yoyoyaya  It is a good measurement except :

1. It is not universally available.  We only know about the from what they chose to review
2. It is not easy to calculate from normally published specifications.

Since manufacturers do not publish EPDR we are stuck trying to identify hard to drive speakers without it.  Often we can't even get minimum impedance values either.

@erik_squires - not disagreeing, but at least Stereophile and Hi Fi News are trying to be as informative as possible. But what the EPDR measurements of a range of speakers do tell us is that, in general, speakers are harder to drive than most manufacturers' generally used specifications tell us. So my rule of thumb is to take the nominal impedance and assume that the real impedance is lower than that.

The B&W 800 series are a good example of speakers that are relatively efficient but difficult to drive.

@yoyoyaya , I am running an ancient (going on 30 years old) pair of B&W 805s; I just took a look at the literature that came with them, and it states that the sensitivity is 87 and nominal impedance is 8 ohms. Since I have owned these speakers, I have ran them with three different tube amps, and am currently running them with one that is switchable between ultralinear and 50 wpc triode, and mostly always I have used the triode setting. I had never thought of these speakers as being particularly hard (for any of the amps I have owned) to drive; but with that typed, the largest room I have ever had them in was probably on the small side of medium, and presently, the room that they are in now is just plain SMALL.

@OP. I owned a pair of 805s for a number of years. Very nice loudspeakers and not difficult to drive. The newer 800 series - the floor stand speakers in particular - are a different kettle of fish entirely.

@yoyoyaya  , thanks, that's interesting (particularly since I am kicking around the idea of upgrading).

Given that my 805s are going on 30 yeras old, and taking in account for inflation and technology, how far do you think I'd need to go to make a significant upgrade?

@OP. Just speaking to your opening post. I think it would be well worth you while listening to a pair of P3 XDs. As you will gather from some of my posts on other threads, I'm not overly enamoured of the direction B&W have gone in voicing their recent speakers - and they are getting quite expensive. You might also want to listen to a pair of M30s or Spendor Classic 2/3s if you feel you need a bit more scale and bass extension. Lastly, though they are a bit polarising, I would listen to a pair of Kef LS 50 Metas, which are outstanding value for money. The foregoing comments are based on personal experience of all of those loudspeakers and of the current B&W range.

Try Tube Amp(s) now or some day?

That is why I recommend starting/auditioning higher sensitivity speakers, hopefully finding one you really want.

Also, avoid speakers whose impedance drops a lot from it's 'nominal' impedance rating, that will effect/limit the amps to ones that can properly handle low impedance.

Lower power needs lets you select amps/tube amp(s) that are smaller, less heat, more placement options, as well as being in a more competitive price category.

My friend is currently looking for a pair of 100 wpc tube mono blocks. Very limited, big, heavy, hot, big price

@yoyoyaya It's a very good point.  The Kef Reference 1 Meta is an excellent example.

I wish someone would loan me one of those, there is some truly wonky stuff going on in their crossover.

@OP and Erik_Squires, I just took another look at the LS50 Meta's measurements - it has a couple of tough impedance/phase dips in the bass and low midrange and it's insensitive, so might not be the best choice for the amp in triode mode. However, the crossover design choices have yielded a really very fine set of measurements otherwise.

@yoyoyaya , my amp does have 4 ohm taps. Do you think that might compensate for "tough impedance/phase dips in the bass and low midrange"?

And what did you mean by

though they are a bit polarising

?

@OP what I meant by polarising is that some people love LS50s and other's for some reason don't like them at all. In fact, that may be due to the fact that they are a tough speaker to drive. I went back and had a look at John Atkinson's measurements for your V12. On paper, even accounting for the 4 Ohm tap, they don't look like an ideal match for one another - due to the tough load and limited efficiency. However, a lot depends on what kind of music you listen to and what volume you listen at.

immatthewj OP

Those ARC's 110 wpc had to big, big, big (price, size, heat). How'd they sound?

@elliottbnewcombjr , if my memory serves me (and it may not), ARC was claiming that the VTM120s with four 6550s in each one were making 100 wpc.

In retrospect, I think that they sounded great. They could rock the house or whisper real quiet or just play sweet and smooth. My aural memory is probably not the most accurate, but now I think that they probably outperformed my current Cary V12 that I replaced them with. What I did not like about them (and I am not at all saying that this is applicable to all ARCs or even all VTM120s) was their reliability (or lack thereof). Every so often (and by that I mean way more often than once in a blue moon) on start up one of them would blow a grid resistor. It usually sounded like a lady-finger firecracker going off, or maybe not quite that loud, but it meant I had to get whichever was the offending amp down, put it on a table, pull the bottom panel off, and desolder the blown resistor from the circuit board and resolder in another one, of which I started keeping several on hand (I seem to remember them being 75 ohm resistors). It wasn’t the end of the world, but it wasn’t a great way to start a listening session. It got to where I would cross my fingers and grit my teeth when I flipped the switches. And most of the time I got my wish and they started up without incident; but a failure happened often enough that it was always on my mind.

By contrast, that Cary V12 that I replaced them with is super reliable. Occasionally it will blow an AC power fuse when I turn it on. Early in its life one of the output tubes went down, and a few years ago one of the signal caps failed, but all in all it is a very reliable amp, and I have had a lot of fun with it over the years.

Given that my 805s are going on 30 yeras old, and taking in account for inflation and technology, how far do you think I'd need to go to make a significant upgrade?

Any significant upgrade with modern speaker can turn out a downgrade so take that into consideration. It was the best monitor they've ever produced. They're easy to drive with tube amps, because of their stable impedance. 

I went back and had a look at John Atkinson’s measurements for your V12. On paper, even accounting for the 4 Ohm tap, they don’t look like an ideal match for one another - due to the tough load and limited efficiency. However, a lot depends on what kind of music you listen to and what volume you listen at.

Wow, thanks, @yoyoyaya ! I suppose I should be looking at something with similar specs to my current but aged 805s (sensitivity of 87 or greater and 8 ohm minimal impedance). My online window shopping I have been doing at Music Direct was starting to focus on the Wharfedale Elysian 1 with AMT tweeter, but considering the specs, a nominal impedance of 4 ohms and minimal impedance of 3.8 ohms (sensitivity 89) that impedance might make them tough for the Cary.

I will say that right now, and probably for some time to come, my listening is happening at a fairly near field in a small room, and usually consists of smaller jazz or folk presentations usually featuring a female vocalist and I am not cranking it to excessive levels.

I wonder if Klipsch should be on my radar at all? A while back ago in another thread I had asked about impressions of the Mobile Fidelity Source Point speakers, and @soix had recommended Joseph Audio Prisms and even sent me a link for a used pair. I haven’t contacted the seller about an audition period yet, but I wasn’t ruling them out, either.

Any significant upgrade with modern speaker can turn out a downgrade so take that into consideration. It was the best monitor they've ever produced. They're easy to drive with tube amps, because of their stable impedance. 

Thank you for responding @czarivey  , to be totally honest, I do not have a great understanding about this hobby, but I suppose in one respect, I am like most everybody else, and always wondering what the weak link is and what it would sound like if I upgraded past it.  When I bought those B&Ws way back in nineteen-ninety-something, I was so happy with them that I didn't even think about them as a weak link and I kept on upgrading the electtronics in front of them, and lately I was thinking that I had the front end to speaker ratio skewed.  And that is what prompted the recent "windo shopping" I have been doing.

@OP There is no problem using a 4 ohm speaker with your V12 as long as the speaker is fairly close to it's nominal impedance. But you probably want something in the region 87dB. But if you are sill happy with your 805s, I wouldn't be rushing out to change them.

Any significant upgrade with modern speaker can turn out a downgrade so take that into consideration. It was the best monitor they've ever produced. They're easy to drive with tube amps, because of their stable impedance.

But if you are sill happy with your 805s, I wouldn't be rushing out to change them.

@czarivey  and @yoyoyaya  thanks, that might be the best advice for me to live by for the time being. 

AOP - you're welcome.

As many have posted, the nominal impedance varies with frequency.  Getting lower efficiency speakers to make a sound with a few watts isn't that difficult, but getting the most out of them with insufficient power is.  Nearly all sensitivity ratings are made at 1000 Hz, so it's just a tiny slice of the spectrum we're attempting to amplify.  For example, if the speaker is 3 db less sensitive at 100 Hz, it will take 2x as much power at that frequency to produce the same volume as the 1000 Hz tone.  And if the impedance drops to 4 ohms, for example, at 100 Hz, then the current demands will be higher for 100 Hz than 1000 Hz.  I used to have Thiel CS3.5.  They were the first speaker I owned that really needed power.  They were excellent speakers for weeding out the amp collection.  Then I discovered Magnepans, which had a hard to drive, must have power reputation.  Yet they weren't nearly as difficult as the Thiels.  None of my tube amps could drive the Thiels well, while the Maggies love tubes.  Moral of the story, don't read too much into the specs.  They're a single data point.  Music is a nearly infinite amalgam of data points when you consider the frequencies and amplitudes at play.  Listen to speaker candidates with the amp(s) you have, or better yet, choose the speakers you like best, then find the amp that pairs the best with them.

@lemonhaze +1

Mike

@ditusa, Hi Mike, bet those JBLs can crank. Pink Floyd don't play through no stinkin dome tweeters.