Please Explain Speaker Sensitivity (1 Viewer)

[John Dirk]

The title may be a bit misleading as I already understand the basic concept of speaker sensitivity. What I'm hoping to learn more about here is what [in the speaker design] ultimately determines the sensitivity of a particular enclosure. Clearly the better performers in this area tend to be associated with correspondingly high end manufacturers. Mine are 87dB and they sound pretty good but I've seen others rated at 98dB. Should I be looking at those or should I be satisfied with what I have? My room is approximately 21 x 11 ft with an 8ft ceiling.

Thanks for all expert advice.

 

[JohnRice]

Clearly the better performers in this area tend to be associated with correspondingly high end manufacturers.

Actually, the exact opposite is true. High efficiency is typically achieved by sacrificing the sonic performance of speakers. Designers of high end speakers know their customers are more willing to spend big bucks on better amplification, to overcome the more difficult load of the speakers they design. Look at any truly high end speaker, and you're likely to find they have low impedance and low sensitivity. 4 Ohm, or even lower impedance, and sensitivity in the mid 80s is typical. Mine are 4 Ohm, 86 dB, which qualifies as a pretty difficult load, which is why I have a bullet-proof, Class A/B 500 WPC amp for them. A typical speaker from companies like Cerwin Vega or Klipsch will be a solid 8 Ohm with sensitivity in the high 90s or even low 100s. The reason I mention those two brands is because they have a long history of making speakers with extremely high efficiency.

Another popular misconception is that larger drivers, like a Pioneer speaker from the 70s with a 15" woofer, are less efficient. It's another case where it's almost always the exact opposite. As a general rule, smaller speakers are less efficient than larger ones. Those big party speakers (talking those enormous Cerwin Vegas again) are almost always extremely efficient.

The interesting thing is, if you want an easy indication of a better speaker, the odds are that between two similar choices, the one with lower sensitivity and lower impedance will sound better, because it was designed with sound more in mind than efficiency. The problem is, they need more and better power to drive them. Look at the Elac Uni-Fi UB5. A small, reasonably priced bookshelf speaker. 4 Ohm, 85dB. A very difficult speaker to drive. Then read the reviews of them.

 

[John Dirk]

Great information and I appreciate it.

 

[ManW_TheUncool]

There are bound to be exceptions to such rules though.

Consider those modestly priced Tektons that someone else recently asked about (as upgrade over his B&W bookshelves).

I was quite skeptical until I checked some of Stereophile's recommended lists from the last several years (and also a couple other reviews, including on Audiogon). IF you want a (relatively) modestly priced, efficient speaker that's audiophile quality and might suit you, seems like the Tektons are definitely worth considering (and might really be the only option that fits all those criteria). That's not to say Tektons are perfect for everyone who wants high fidelity sound of course... even if the hype is real...

_Man_

 

[JohnRice]

There are always exceptions. I was just responding to the comment that higher sensitivity means higher end. I mentioned Klipsch, and my first really "good" speakers were the original Klipsch Forte, which I bought in '87 or '88. They were very good speakers, and had 98dB sensitivity, so they easily played loud. I wish I still had them. They were my main speakers until I got my Thiels somewhere around '93. The Fortes were good, but the Thiels are just in a different league. Still, if you only used them for movies, you might not find one was clearly better than the other. It's with music that the Thiels show their strength, so with a system that was all video sources, they'd probably be a waste of money.

I wanted to add, that I bought a pair of JBL 4311s somewhere around '79, and I thought they were the greatest thing, until I got the Fortes, which I thought were the greatest, until I got the Thiels.

 

[ScottHM]

The interesting thing is, if you want an easy indication of a better speaker, the odds are that between two similar choices, the one with lower sensitivity and lower impedance will sound better, because it was designed with sound more in mind than efficiency.

"Better" is highly subjective. Low efficiency speakers will never have the dynamic range of a highly efficient system. The question is, are you more likely to find a reasonably accurate high efficiency speaker, or a highly dynamic low efficiency speaker? I believe it's the former.

---------------

 

[JohnRice]

Low efficiency speakers will never have the dynamic range of a highly efficient system.

I'm sorry, but that simply is not true. Lower efficiency speakers merely require more power. A highly efficient speaker with easy impedance is just less reliant on what's driving it. There are too many factors that go into aspects of a speaker, like dynamics. It can't be narrowed down to one simple number. It's a result of multiple design factors of the speaker, plus the amp itself. With amps, like with speakers, their characteristics can't be narrowed down to one number. Better amps can have (but not always) more power, but they also control the drivers of the speaker better, which will result in various improvements in sound, one of the most pronounced is improved dynamics. We just haven't figured out a good way to measure several of those aspects. For example, when a speaker's sensitivity is lower, the noise floor is lower, which increases the potential dynamic range. My Klipsch Fortes were very nice, lively, dynamic speakers, with very high sensitivity. As impressed as I was with them, they couldn't touch the dynamics the Thiels produce, with their 10+ dB lower sensitivity, as long as they are fed the right power.

Sensitivity really has very little to do with the dynamic capability of a speaker. There are low sensitivity speakers that are smooth in a way that can be interpreted as flat. Take electrostatics, for instance. There are high sensitivity speakers that are also flat.

But yeah, "Better" is highly subjective.

 

[ScottHM]

I'm sorry, but that simply is not true. Lower efficiency speakers merely require more power.

Correct. A speaker with 85dB (@ 1W) efficiency will require 16 times more power than one with 97dB efficiency to play at the same loud volumes (assuming the speaker can even handle that much power), which makes it impractical for most people with low efficiency speakers to reproduce wide dynamic ranges. It's not that "merely" more power is required, it's that massively more power is required.

---------------

 

[JohnRice]

That's not what you said. You said "Low efficiency speakers will never have the dynamic range of a highly efficient system."

Low efficiency speakers will never have the dynamic range of a highly efficient system.

Plus, a 97dB speaker will never need more than about 10 watts to make the walls crumble, so 16x 10 watts isn't exactly insurmountable.

Anyway, I've tried my best to fully explain the original question, as well as I am able to, and carefully in a way where I don't have to backtrack due to things I never stated. In fact, in my very first response, I clearly stated I'm using a 500 WPC amp with my speakers. I have genuinely tried to explain as fully and accurately as I am able. So, I'll just move on unless anything else compelling is brought up.

 

[John Dirk]

Sam and Scott - This is all great information for me. Hearing different perspectives from knowledgeable sources is hugely valuable.

Much appreciated!!!

 

[bigshot]

In a nutshell... Speaker designers balance three factors: size of the cabinet, sensitivity and deep bass. You can design to get two of those things, but not all three at once. In the 70s speakers were efficient and had deep bass but the cabinets were large. That was a good thing, because amps weren't as powerful back then. Now we have small speakers that have deep bass, but they aren't as efficient. And modern amps are more powerful. It's all tradeoffs.

 

[ScottHM]

Hearing different perspectives from knowledgeable sources is hugely valuable.

---------------

 

[JohnRice]

We can right-fight until everyone gives up and goes away. I think it's more productive to stay away from statements like "this can never match that" because speaker design is extremely complicated. Far more complicated than any of us, including I, can comprehend. I've heard great things about ZU speakers for years, and Sean Casey is really blowing the doors off a lot of ideas about speaker design. Like Stephen said, most of the best recent speaker designers, like Richard Vandersteen, David Wilson, Andrew Jones and Jim Thiel, haven't been very concerned about efficiency. Probably because power isn't a big hurdle. their priorities have been in some of the infinite other aspects of a speaker. The only other prominent speaker designer I can think of who championed efficiency was Paul Klipsch, but he was back in the day when power was at much more of a premium. Maybe he was right. He certainly had a point, but not the only point.

An argument was made that it's financially "impractical for most people with low efficiency speakers to reproduce wide dynamic ranges" because high power amps are too expensive. OK, but you can't back up that argument with highly efficient speakers that cost, for floor standing models, mostly between $4,500-$17,000. Not only are those expensive, but I guarantee people who buy those aren't powering them with a $300 Denon receiver. They're mostly using multi-K$ pure Class-A and tube amps.

Still, what Sean Casey is doing is fascinating. I'd sure like to hear his speakers.

 

[Josh Steinberg]

I just want to throw out there, apropos of nothing, that when I was looking to buy speakers a few years ago, John Rice had infinite patience with my questions here and made some of these complex issues seem understandable to me. I remain grateful.

 

[JohnRice]

I appreciate the kudos. Too often I feel I cause more conflict than good here on HTF. Through the years it's prompted me to sometimes stay away for long periods of time.

To get back to the issue of sensitivity (that topic seems kind of ironic) I've just been trying to provide information based on what is available in the marketplace. The fact is, the overwhelming majority of high sensitivity speakers are fairly low end. There are a few exceptions, but they're definitely the exceptions. That doesn't mean that they have to be, just that almost all designers of higher end speakers simply don't make efficiency a priority. I don't know nearly enough about the nuts and bolts of speaker design to know if they're missing out on something or not. What I can say from my own experience is that the Klipsch Fortes I owned years ago were ultimately driven with an Adcom GFA-555 amp, which had far more power than the speakers needed and is still highly regarded, and even though the Fortes really were one of the best high sensitivity speakers available, and as good as they sounded, they just didn't produce the same dynamics as the far more difficult Thiels, with even more power. Not only that, but they would start breaking up at lower playback levels than the Thiels can produce. It seems to make sense that more efficient speakers would be capable of more dynamics. We might find out if more companies made high end enough ones to truly compete with what's available now.

 

[JohnRice]

This thread, along with some others that have been kind of annoying to deal with, got me thinking over a lot of stuff again. It's been good to think some stuff through. For one, someone had commented about the benefits of higher efficiency speakers. My response was regarding what speakers are actually available, but it also got me digging more into what could be with high efficiency speakers. Zu was what got me thinking.

There are clear benefits, and some negatives, to higher efficiency speakers, so I started wondering why high end speakers are almost always difficult to drive. I think part of it is because they can be. Designers of high end speakers know their customers are willing to pay to drive them. Speaker design is incredibly complicated, and not adding high efficiency to the list of goals and obstacles just makes it a little easier. Plus, I think there's a certain attitude, arrogance really, to knowing they are helping to drive the high end industry by building speakers that will promote sales of fancy, expensive electronics. As I've been reading, I've learned how drivers can be made more efficient, but it adds cost, as well as creating other complications. The designers might find that the added cost to manufacture more efficient drivers doens't make good design sense, all things considered. That highly efficient, full range driver Zu uses sounds like it's extremely expensive to build. The speakers sure are expensive, considering how simple they are on other ways, such as not having a crossover.

I've gotten caught in some other arguments that have been frustrating, but I think I'm understanding more why they are happening. For instance, everything I find confirms that larger speakers and woofers lean toward higher efficiency. First, because the larger the woofer cone (or more woofers), the less movement, and less power, is needed to reproduce a certain low frequency at a certain level. It seems that the efficiency of the woofer(s) is a major determination in how efficient a speaker is on the whole. The lower the frequency being reproduced, the more power it takes to reproduce it. I think that might be where most of the disagreement about driver size came from. A woofer (which is larger) requires more power than a tweeter (which is smaller) not because of their size, but because of what frequencies they are reproducing. Also, and this is what seems counter intuitive, a larger speaker, with a larger woofer and maybe more drivers overall, will be more efficient than a much smaller one. A big part of it is because if the smaller woofer has 1/9th the area of the larger one, it takes 9x as much linear travel to produce the same pressure, which requires a lot more power. With sound, you have to move a certain amount of air and that's with either a lot more movement from a smaller woofer, or less movement from a large one.

Anyway, time to move on.