Efficient vs. Inefficient speaker - AVS Forum
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Old 10-08-2010, 01:41 PM - Thread Starter
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I was reading in another thread that someone thought their Ascend Sierras were inefficient at 87db. That made me think about mine Home Theater Direct level 3 speakers and their respective sensitivity of 89db. I fully plan on adding an amp (emotiva, adcom, et al) in the future but was curious as to what is considered an efficient or inefficient speaker.
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Old 10-08-2010, 01:55 PM
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Take with a grain (or perhaps block) of salt, but in the Olden Days I was taught that generally speaking 95 dB sensitivity and up was very efficient, 90 - 95 dB "efficient", 85 - 90 dB "less efficient", and below 85 dB inefficient. You'll probably get as many answers as people, and the usual tirades about mixing up "efficiency" and "sensitivity", but there's my opinion.

Interestingly, a lot of good smaller speaker systems (bookshelfs) are pretty inefficient because the midrange, where the drivers are most efficient/sensitive, is reduced in level by the (effect of) crossover to provide a wider frequency response for the overall system.

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Old 10-08-2010, 01:57 PM - Thread Starter
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I figure it all becomes moot if pushed with a quality AVR or a decent one with an external amp.
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Old 10-08-2010, 02:12 PM
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Well, there is really no such thing as an efficient speaker. They are all very poor at converting electrical energy to sound energy. The more sensitive ones are just more efficient.

Sensitivity used to be important for home systems back in the vacuum tube days when output power from amplifiers was limited. Now it is mostly an issue for large venues. But today, it is just a matter of how big an amplifier do you need.
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Old 10-08-2010, 02:31 PM
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Could not disagree more. These days speaker sensitivity is very, very important.

Music in general is demanding. H/T in particular is extremely demanding due to the very wide dynamic range contained in contemporary soundtracks and LFE techniques.


Just adding more power to achieve higher levels in an inefficient speaker, does work, but you can easily end up with more and more compression, and eventually premature driver failure.

Additionally, I find that dynamics compression in some speakers, really compromises the overall immersive experience, and impacts the sound in a way that's not as easy to recognize as other forms of distortions.

When compression sets in, the presentation ceases to increase in volume at all freqs at the same rate. Whatever driver encounters compression first, that freq band will thicken and begin to get muddy. It's not offensive, it just loses that nice transient snap and transparency.

IMO, sensitivity is of paramount importance. For H/T, at realistic levels, it a must.

Check this out;
Ignoring room reflections, lets look at a speaker that has a sensitivity of 88db, power handling of 120 watts and a listening distance of 14 feet (OPers distance)

At one meter
1 watt 88db
2 watts 91db
4 watts 94db
8 watts 97db
16 watts 100db
32 watts 103db
64 watts 106db
120 watts nearly 109db

Now you have to subtract for distance
2 meters -6db
4 meters -12db

109db -12db = 97db max output.

Now you have to subtract 3db to 6db for power compression. I will only use 3db. 97db-3db = 94db. If you want to have clean peaks you need at least 3db of headroom. 94db-3db=91db. 91db is your clean peak db level for that speaker. Since HT has 20db to 30db swings, your average listening level needs to be at a maximum of 71db. Any peak in the movie that exceeds 20db will be clipped and distorted with that speaker.

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Old 10-08-2010, 02:40 PM - Thread Starter
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Quote:
Originally Posted by FOH View Post

Could not disagree more. These days speaker sensitivity is very, very important.

Music in general is demanding. H/T in particular is extremely demanding due to the very wide dynamic range contained in contemporary soundtracks and LFE techniques.

Just adding more power to achieve higher levels in an inefficient speaker, does work, but you can easily end up with more and more compression, and eventually premature driver failure.

Additionally, I find that dynamics compression in some speakers, really compromises the overall immersive experience, and impacts the sound in a way that's not as easy to recognize as other forms of distortions.

When compression sets in, the presentation ceases to increase in volume at all freqs at the same rate. Whatever driver encounters compression first, that freq band will thicken and begin to get muddy. It's not offensive, it just loses that nice transient snap and transparency.

IMO, sensitivity is of paramount importance. For H/T, at realistic levels, it a must.

Check this out;
Ignoring room reflections, lets look at a speaker that has a sensitivity of 88db, power handling of 120 watts and a listening distance of 14 feet (OPers distance)

At one meter
1 watt 88db
2 watts 91db
4 watts 94db
8 watts 97db
16 watts 100db
32 watts 103db
64 watts 106db
120 watts nearly 109db

Now you have to subtract for distance
2 meters -6db
4 meters -12db

109db -12db = 97db max output.

Now you have to subtract 3db to 6db for power compression. I will only use 3db. 97db-3db = 94db. If you want to have clean peaks you need at least 3db of headroom. 94db-3db=91db. 91db is your clean peak db level for that speaker. Since HT has 20db to 30db swings, your average listening level needs to be at a maximum of 71db. Any peak in the movie that exceeds 20db will be clipped and distorted with that speaker.

Wow, I really need to go back to school
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Old 10-08-2010, 04:06 PM
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Consider this;

Individuals drool and obsess over an amplifier that has twice the power of theirs, however when considering speakers, the same person gives little thought to a 3 db difference in sensitivity....which are equivalent.

The inadequacies of a vast majority of dome tweeter based hi-fi type speakers and their inherent limitations, are by and large not capable of realistic playback levels of H/T material.

Break-up and compression, destroy the suspension of dis-belief. When one experiences low distortion, high output devices at realistic levels whereby the peaks are being handled appropriately, the quest begins. The quest of attaining system capability, that allows playback of dialog scenes at live levels, and yet handles the the 30 to 40 db peaks with aplomb.


Have fun

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Old 10-08-2010, 05:34 PM
 
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Depends entirely on your needs.

Even with relatively inefficient and difficult-to-drive loudspeakers, you can achieve amazing SPL if they have the capability and you have the amp power (particularly electrostats for example).

But many listeners, myself included, place dynamic range capabilities far down the list of sound requirements, so whether the speaker has high sensitivity and can hit high SPLs cleanly is not a major concern.

I can appreciate the benefits of such capabilities, but doing that extremely well comes at a very high $ cost, or comes at a major sacrifice of sound quality when you're not talking about $10,000 speakers.

So it really depends on your priorities whether speaker sensitivity is even something worth paying attention to. It is something that some people pay particular attention to, and for good reason. And it is also something that some people like myself pay almost no attention to at all, also for good reason.
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Old 10-08-2010, 05:38 PM
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Quote:
Originally Posted by FOH View Post

Could not disagree more. These days speaker sensitivity is very, very important.

Music in general is demanding. H/T in particular is extremely demanding due to the very wide dynamic range contained in contemporary soundtracks and LFE techniques.


Just adding more power to achieve higher levels in an inefficient speaker, does work, but you can easily end up with more and more compression, and eventually premature driver failure.

Additionally, I find that dynamics compression in some speakers, really compromises the overall immersive experience, and impacts the sound in a way that's not as easy to recognize as other forms of distortions.

When compression sets in, the presentation ceases to increase in volume at all freqs at the same rate. Whatever driver encounters compression first, that freq band will thicken and begin to get muddy. It's not offensive, it just loses that nice transient snap and transparency.

IMO, sensitivity is of paramount importance. For H/T, at realistic levels, it a must.

Check this out;
Ignoring room reflections, lets look at a speaker that has a sensitivity of 88db, power handling of 120 watts and a listening distance of 14 feet (OPers distance)

At one meter
1 watt 88db
2 watts 91db
4 watts 94db
8 watts 97db
16 watts 100db
32 watts 103db
64 watts 106db
120 watts nearly 109db

Now you have to subtract for distance
2 meters -6db
4 meters -12db

109db -12db = 97db max output.

Now you have to subtract 3db to 6db for power compression. I will only use 3db. 97db-3db = 94db. If you want to have clean peaks you need at least 3db of headroom. 94db-3db=91db. 91db is your clean peak db level for that speaker. Since HT has 20db to 30db swings, your average listening level needs to be at a maximum of 71db. Any peak in the movie that exceeds 20db will be clipped and distorted with that speaker.

Hmmmmm....

#1. You've ignored room reinforcement.
#2. You've assumed 120 watts per channel max amplifier output.
#3. You assumed 120 watts maximum power handling.
#4. You are only specifying ONE speaker. Most systems have at least 2, (+3 db), and possibly 3 to 5 or 7, (+6 or more db).

Lets take a different system and add in for room reinforcement and multiple speakers:

90 dB sensitivity speaker, 1 watt/1 meter, anechoic, with 300 watts power handling, 300 wpc amps, and speakers placed in an "average" sized, non-treated room.

At one meter (per speaker):
1 watt 90db + 6 dB of room reinforcement = 96 dB
2 watts 99db
4 watts 102db
8 watts 105db
16 watts 108db
32 watts 111db
64 watts 114db
128 watts 117db
256 watts 120db

Now you have to subtract for distance
2 meters -6db
4 meters -12db

120db -12db = 108db max output PER speaker.

Add 2 more front speakers and 2 surrounds: = (at least) +6 db.

That is a total system volume of 114 dB, just for the speakers.

Add a capable subwoofer system with the 10 dB boost of the LFE channel, and total system SPL's of 120 dB are easily possible.

All you need is moderate sensitivity speakers with high power handling, strong amplifiers and good subwoofers.

There is more than one way to reach the goal.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

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Old 10-09-2010, 10:54 AM
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Chris Wiggles,

You're correct, it does depend on one's needs and priorities. That's why I stated that for H/T in particular, the lack of proper dynamic capability limits one's ability to create an immersive experience, that's free from the inherent limitations of low sensitivity speakers. A very specific quality, in a specific application.

Like many of us here, I've been very fortunate having been exposed to an extremely wide variety of equipment. From every live sound pro audio experience you can imagine, studio sessions, and being an avid home audio enthusiast since the 70s, there are two speaker system qualities that I strongly feel all paramount above all others; flat FR, and dynamic capability.

Others obviously feel differently. But when those two qualities are covered, everything else I value comes much easier. Flat FR is somewhat self explanatory, but dynamic capability can be achieved utilizing differing approaches. Beginning with high sensitivity designs, creates a much more fertile environment in which to work.

Lower excursions retain the driver in a more linear envelope, and keeps many types of distortions down to an acceptable level. Keeping power levels down, keep both types of potential compression, magnetic and thermal, to a level at which their contribution is minimized.

You mentioned amazing spls that are capable from electrostats. I'm not sure what constitutes amazing, however I do know that stats are anything but linear devices. They do have their place however, it's just not in H/T with the inherent dynamics involved.

I thank you for the electro-static speaker referance, it truly reminds me of my most memorable benchmark in audio. Electrostats in general, Acoustats specifically are what I credit to my pursuit of high end audio. Salesman sat me down in front of the Acoustats, with an Audio Research front end, properly set up room. He put some Spanish guitar LP on a good turntable, closed the sliding door and he left the room...(loved those HiFi Salons)......... My goodness... Magic! I'd never heard anything like this. Palpable, 3D, left to right, front to back....lovely detailed, yet lushly enveloping. I'll never forget the feeling. So he comes back in the room in about 10 minutes. I was smiling ear to ear, and he asked me what I thought. I couldn't really articulate how I felt, but I asked him to turn it up. He chuckled and said "that's as loud as they'll go". Lessen learned; design compromises. I remember the store, the salesman's name (still in the business, afaik), I remeber all the gear they had in that "A" room, and some of the stuff they had in the "B" room as well.

Anyway I can appreciate your feelings toward stats. But for me, an immersive suspension of disbelief can not be achieved in H/T with stats.

Thank You

btw, can you elaborate on this statement? wrt sensitivity;
Quote:


And it is also something that some people like myself pay almost no attention to at all, also for good reason

Honestly, why for good reason would you disregard sensitivity?

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Old 10-09-2010, 11:03 AM
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Quote:
Originally Posted by craig john View Post

Hmmmmm....

#1. You've ignored room reinforcement.
#2. You've assumed 120 watts per channel max amplifier output.
#3. You assumed 120 watts maximum power handling.
#4. You are only specifying ONE speaker. Most systems have at least 2, (+3 db), and possibly 3 to 5 or 7, (+6 or more db).

Lets take a different system and add in for room reinforcement and multiple speakers:

90 dB sensitivity speaker, 1 watt/1 meter, anechoic, with 300 watts power handling, 300 wpc amps, and speakers placed in an "average" sized, non-treated room.

At one meter (per speaker):
1 watt 90db + 6 dB of room reinforcement = 96 dB
2 watts 99db
4 watts 102db
8 watts 105db
16 watts 108db
32 watts 111db
64 watts 114db
128 watts 117db
256 watts 120db

Now you have to subtract for distance
2 meters -6db
4 meters -12db

120db -12db = 108db max output PER speaker.

Add 2 more front speakers and 2 surrounds: = (at least) +6 db.

That is a total system volume of 114 dB, just for the speakers.

Add a capable subwoofer system with the 10 dB boost of the LFE channel, and total system SPL's of 120 dB are easily possible.

All you need is moderate sensitivity speakers with high power handling, strong amplifiers and good subwoofers.

There is more than one way to reach the goal.

Craig




Craig John,

I much prefer your version. The version I posted was a copy and paste from another thread regarding the importance of the "free lunch" of sensitivity. (hence the "check this out", and referring to the OPers distance, as well as the italics) So if what I used is in accurate, I should have been more careful.

I've got several questions concerning your numbers, somethings you may have to help me out with.

As soon as I get some time, I need to wrap my head around what you posted, and continue this.

Thank you for the clarification.

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Old 10-09-2010, 12:16 PM
 
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Quote:
Originally Posted by FOH View Post

Chris Wiggles,

You're correct, it does depend on one's needs and priorities. That's why I stated that for H/T in particular, the lack of proper dynamic capability limits one's ability to create an immersive experience, that's free from the inherent limitations of low sensitivity speakers. A very specific quality, in a specific application.

Like many of us here, I've been very fortunate having been exposed to an extremely wide variety of equipment. From every live sound pro audio experience you can imagine, studio sessions, and being an avid home audio enthusiast since the 70s, there are two speaker system qualities that I strongly feel all paramount above all others; flat FR, and dynamic capability.

Others obviously feel differently. But when those two qualities are covered, everything else I value comes much easier. Flat FR is somewhat self explanatory, but dynamic capability can be achieved utilizing differing approaches. Beginning with high sensitivity designs, creates a much more fertile environment in which to work.

Lower excursions retain the driver in a more linear envelope, and keeps many types of distortions down to an acceptable level. Keeping power levels down, keep both types of potential compression, magnetic and thermal, to a level at which their contribution is minimized.

Absolutely. Doing this really well though, is somewhat difficult. One of the better dynamic theaters that hit reference level cleanly and with great ease was all Genelec, and it was like $200K of speakers in a medium-large theater space, with I think like 9 subwoofers.

Running some movies with great dynamics is breathtaking in these kinds of systems, the impact you get from explosions or gunshots is amazing.

But, like I said, doing this and doing it with really good SQ overall does not come cheap.

Quote:


You mentioned amazing spls that are capable from electrostats. I'm not sure what constitutes amazing, however I do know that stats are anything but linear devices. They do have their place however, it's just not in H/T with the inherent dynamics involved.

My statement was confusing, I was referring particularly to the need for large amps for electrostats, rather than SPL so much. A lot of other designs will walk all over them in terms of max SPL they'll hit, but some of the dynamics and high-frequency clarity you can hit with electrostats can be pretty amazing. Obviously you run into problems with the midrange and bass, but for HF they can be very impressive, just require TONS of amplifier power.

I did a system with some of the biggest Martin Logans and a whole bunch massive B&K mono amps for a guy who loved rock/metal, and that system got LOUD, but did it really cleanly. Martin Logans aren't really my taste, but given his goal and music tastes it made a lot of sense and that was actually the first time I was truly impressed with MLs, but mainly because they were being fed by like a 1000 pounds of amplifiers that I spent all day wrestling into place...

Quote:


I thank you for the electro-static speaker referance, it truly reminds me of my most memorable benchmark in audio. Electrostats in general, Acoustats specifically are what I credit to my pursuit of high end audio. Salesman sat me down in front of the Acoustats, with an Audio Research front end, properly set up room. He put some Spanish guitar LP on a good turntable, closed the sliding door and he left the room...(loved those HiFi Salons)......... My goodness... Magic! I'd never heard anything like this. Palpable, 3D, left to right, front to back....lovely detailed, yet lushly enveloping. I'll never forget the feeling. So he comes back in the room in about 10 minutes. I was smiling ear to ear, and he asked me what I thought. I couldn't really articulate how I felt, but I asked him to turn it up. He chuckled and said "that's as loud as they'll go". Lessen learned; design compromises. I remember the store, the salesman's name (still in the business, afaik), I remeber all the gear they had in that "A" room, and some of the stuff they had in the "B" room as well.

Right. Sometimes it's all compromises, particularly when you don't have an endless budget.

Quote:


Anyway I can appreciate your feelings toward stats. But for me, an immersive suspension of disbelief can not be achieved in H/T with stats.

Thank You

btw, can you elaborate on this statement? wrt sensitivity; Honestly, why for good reason would you disregard sensitivity?

Well, like I said it's not necessarily something everyone is looking for.

Just for example, there are some people who like using mid-sized full-range drivers. That's a horribly insensitive design, you're not going to have really any bass to speak of, and you're not going to be able to hit even moderate SPL very cleanly. But it's also the kind of speaker some folks will like to put on tube amps or the like, and I've heard systems like this truly sing on sparse jazz and things like that. That's not my taste, but that would be someone who is going entirely the other direction on sensitivity and dynamic range capability because of the particular sound they're after. Now, obviously that's also someone who is not at all interested in Home Theater use where such a system would be truly crippled, but preference is like anything, really. It's kind of arbitrary.

For me for instance, my mains are Dynaudios which have a pretty lowish sensitivity of 86dB, and are small stand-mounted 2-way speakers. Which also, btw, have a very low 1st odrer xover point for the tweeter. I'm powering them with a decently robust Denon 5308 flagship, but my goals in speakers were entirely oriented for 2-channel audio and what I like best about my speakers is the imaging and the non-fatiguing HF detail. Lots of other speakers I have heard over the years can hit higher SPL, have way more dynamics, etc and I could have spent similar amounts of money on those, but none of them got the imaging and detail right for me. Dynaudios just tickle my fancy, so to speak.

Now, they also double for theater use (and frankly probably get more use on movies than music anyway) and my HT sounds fantastic. But it doesn't hold a candle dynamics-wise to the Genelec theater I mentioned before. I get pretty good dynamics and I don't have any problems even at loud volume with clipping or serious distortion, but there's definitely compression happening because gunshots and things like that are plenty loud but not BANG IN YOUR FACE like a system with truly impressive dynamics.

I could have achieved that, but that was not my goal because I was oriented more towards what I could achieve sonically for music with imaging and detail which is what I really care about. If I had $80K I could have achieved both with some very high-end dynaudios, still not with amazing sensitivity, but given enough amplifier power the capability to hit very high SPL cleanly.

So it's really just all about goals. And if impressive dynamics is a goal, high sensitivity helps with that. But it's not always a primary goal, and you can still achieve that even with lower-sensitivity speakers if they are powered right and have the ability to hit those SPLs.

My main point is that sensitivity is something that really comes down to the listener's goals and needs. I was aware when I bought my speakers that they were lower in sensitivity, and nominal 4ohm speakers and benefitting from more powerful amps. Didn't really phase me because I was buying them for imaging and detail, not for dynamics. Someone else who might be interested entirely in dynamics might do better to pay more attention to that than I did because they have very different goals.
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Old 10-09-2010, 03:55 PM
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Quote:
Originally Posted by FOH View Post

Ignoring room reflections

You can only ignore room reflections when you're listening outside or live in a research facility with an anechoic chamber.

Quote:


Now you have to subtract for distance
2 meters -6db
4 meters -12db

If you want to talk theory, in a reverberant space with a diffuse field moving past the critical distance (2-4' for typical speaker/room combinations) will not drop the SPL more than 3dB regardless of how far you get.

In practice it's more complex; with real spaces tending towards a 3dB/distance doubling draw down rate (2 meters -3dB, 4 meters -6dB).

Toole summarizes nicely in __Sound Reproduction: Loudspeakers and Rooms_.
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Old 10-09-2010, 04:44 PM
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this is just another field where compromises are everything..

you have a that triangle of options.

1. Inexpensive/less expensive speakers
2. Efficient speakers
3. Top draw sound quality

you can only choose two..

it seems most high efficiency inexpensive speakers are far from sounding very good, like those cheaper klipsch's that sound like they do nothing but scream. there are some very nice sounding klipsh's *got a chance to hear a set of k-horns recently* but of course they aren't cheap..

At least those are the generalities I have seen.... I would likely take sound quality as my primary point before efficiency. Course by that I mean low distortion numbers, flat frequency and quality cabinets+cross over components..

My time working in music studios has pushed that idea too. I have heard plenty of monitor setups that go really loud or have huge dynamics but are completely useless for proper mixing or mastering.. They are great for wowing clients with large amounts of sound.. Other then that they are pretty much useless.. Unless of course we are taking about studios with million dollar budgets and even then they comprise by using hifi style speakers for large parts of their work and then the big loud monitors to show clients final products or to wow them...

*shrug* ymmv

Matt

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Old 10-11-2010, 11:04 AM
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To those getting into the deciBel math (which is the correct approach), I'd just like to state that 100dB is approximately the level of a jackhammer operating 1 meter away. This is also known as REALLY LOUD.

Assuming an average to high quality amplifier that won't compress or distort at levels of 10W, and that the speaker is designed to handle this average load, it really doesn't matter if one speaker is more efficient than another. One speaker is 89dB, another is 91dB. Sure, you'll have to drive the amp harder to get the same volume, but if that's enough to affect the sound output, you either 1) have the volume way too loud, or 2)have crap gear.
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great subject. today many expensive speakers are insensitive with ratings as low as 85 and 86db. if you listen side by side to speakers with a 93db rating and speakers with an 87db rating same source, same amp.receiver, same volume on amp you will notice the volume from the speaker go down significantly. You need more and more watts today to run today's expensive insensitive speakers, and low volume listening is poor. what is behind this offering of so many expensive, inefficient speakers? who knows, but money most likely- bigger amps cost more. less sensitive speakers are probably cheaper to make, but with a 200 wpc amp and moderately loud volume these seem to sound great. not really. do some serious listening with lower powered amp, and lower volume, and speakers with sensitivity rating of 93db. you hear all the nuances. inefficient is inefficient. not good. all the pieces in making in reproducing recorded sound are inefficient in electrical engineering terms. tube amps- it take a lot of juice from the wall socket to run even a 40wpc tube amp compared to running an 85wpc solid state amp. this is what is comes down to in the end. more power to driver lower efficiency speakers. where does that power ultimately come from- the wall socket man. but, still tube amps sound nice. love my little jolida amp. and have a jolida hybrid i love too.
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Old 05-11-2013, 06:53 PM
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To those getting into the deciBel math (which is the correct approach), I'd just like to state that 100dB is approximately the level of a jackhammer operating 1 meter away. This is also known as REALLY LOUD.
Sorry, but this is simply irrelevant to the discussion. A jackhammer is producing a constant/average SPL of 100dB and nobody is suggesting that you listen to your HT at that level. What is being discussed is the ability to play at an average of 75dB and the ability to cleanly play dynamic peaks that crest through 100dB or more.
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Old 05-11-2013, 07:04 PM
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Take with a grain (or perhaps block) of salt, but in the Olden Days I was taught that generally speaking 95 dB sensitivity and up was very efficient, 90 - 95 dB "efficient", 85 - 90 dB "less efficient", and below 85 dB inefficient. You'll probably get as many answers as people, and the usual tirades about mixing up "efficiency" and "sensitivity", but there's my opinion.
That's about right though.

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Interestingly, a lot of good smaller speaker systems (bookshelfs) are pretty inefficient because the midrange, where the drivers are most efficient/sensitive, is reduced in level by the (effect of) crossover to provide a wider frequency response for the overall system.
The reason they're inefficient is that Hoffman's Iron Law trade offs hit. To get it small (what most people want especially women) and to have decent LF performance (even if only at modest levels) then it will need to be inefficient. You're savvy enough to work through T/S to detemine it's true yourself.

To save me typing, here it is explained from a another site.

"Hoffman's Iron Law". First formulated back in the early 1960's by Anthony Hoffman (the H in KLH), Hoffman's Iron Law is a mathematical formula that was later refined by Thiele and Small, whose work now forms the basis of all modern loudspeaker design.
Hoffman's Iron Law states that the efficiency of a woofer system is directly proportional to its cabinet volume and the cube of its cutoff frequency (the lowest frequency it can usefully reproduce). The obvious implication is that to reduce the cutoff frequency by a factor of two, e.g. from 40 Hz to 20 Hz, while still retaining the same system efficiency, you need to increase the enclosure volume by 23=8 times! In other words, to reproduce ever lower frequencies at the same output level you need an extremely large box! This is why we see so many subwoofers or low eff multidriver towers. Using 5-7 in drivers. Larger woofers are better woofers, larger cabinets are more efficient and produce deeper bass with less thermo compression and Superior transient response. If one compromises size efficiency or range one can make a smaller design.
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Old 05-11-2013, 10:03 PM
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Thanks, I was trying to not get too deep. I thought HIL was for sealed boxes only? I am not a loudspeaker designer, however.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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Old 05-12-2013, 05:07 PM
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Another way of looking at this is simply a choice of which parameters are most important to a designer and the resultant optimization (hopefully) of those choices. AFAIK, you can't optimize all possible performance characteristics simultaneously.

High efficiency drivers and/or speaker design is one such example, being both a design choice and performance characteristic. ie, sometimes it is the driving choice in system design, sometimes it follows naturally from other choices.

Other choices can also lead to very high performing speakers, and choosing to go down a path other than high efficiency isn't inherently bad, just different. You pay for all choices in one way or another. Which ties into my summarization... high efficiency speaker design isn't the only path to high quality audio, but I believe it is by far the least expensive.

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Old 05-13-2013, 07:03 AM
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Thanks, I was trying to not get too deep. I thought HIL was for sealed boxes only? I am not a loudspeaker designer, however.

Hoffman's Iron Law applies to all loudspeakers to some extent but in various ways. Whenever you see an apparent violation of it, detailed investigation will usually show a circumvention, not a falsification. A good example of this is bandpass subwoofers. At first blush they provide a lot more efficiency in a small box, but they do that by trading off high frequency extension. Vented speakers provide more efficiency within their bandpass, but they trade off low frequency extension.
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Old 05-13-2013, 09:38 AM
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Something to be aware of, is REAL effeciency of retail speakers. Often they lack baffle step compensation, or are rated on the +3db side of the +/-3db frequency response, or are half space or even quatre space rated (Klipsch). Once you get them into the room, you run audessay or what ever and it puts a meager 3db boost at 200hz and wham, you double doubled your amplifier requiremens. You aren't listening to them in half space, but pulled away from walls (as you should) and wham, another double the amp requirements. You hear the average frequency response rather than the little peaks, so there's anothe 3db. Another double the amp requirements. Before you know it, instead of 300 watts, you need 2400 watts, and how do you think your speakers are going to appreciate that?

My speakers are an honest 98db/w/m 8ohm speaker and I listen from less than 10' away. I also listen at well below reference. Occasionally I get close. Needless to say, they take it with ease and the sound difference is noteicable. If you want hifi sound during very complex demanding passages (music or HT) the speaker needs to not be stressed out. That's something my big speakers can do much better than my little speakers. The complex demanding stuff. They keep all the instruments separate instead of mushing them all together trying to meed the program demands. Not as easy a task as some people think.

Personally I think an honest 90db/w/m can do hifi provided the SPL is not to high, and not reference levels (that's loud).
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Old 05-13-2013, 10:58 AM
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What average level do you like to listen to?

Depending on the answer, speaker efficiency may play no roll at all with adequate amplification. If on the other hand, the speakers are 8 or 10ft away AND you require 100db average listening levels, then your going to need above average speaker efficiency AND amplification.

On the headroom issue, I feel 10db is preferred. So if after you have done all your math and/or measuring you need 10 watts to get to the average level you want, you ought to have a amp capable of 100 watts for headroom. Obviously, this requires the speakers to handle the peak power not just the average power.

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Old 05-13-2013, 12:51 PM
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@Arny -- Thanks for that. I have not looked closely at loudspeaker design for decades.

General random comments:
  1. ESLs and planer dynamics like my Magnepans tend to look like line sources over most of their fequency range and thus realize an effective 3 dB gain at the listening position relative to point-source speakers. The influence of the room makes general statements fairly meaningless, however.
  2. In the midrange, 1 dB is barely noticeable an requires 1.26x the power. 3 dB is what most hear as a "slight increase" and requires 2x the power. 10 dB is twice as loud and requires 10x the power.
  3. 80 dB average is pretty loud to most people (it certainly is to me). "Realistic volume" is often defined by the listener and of course the room's size and background level must be considered. Almost all the time I go to a movie I find it too loud. YMWV (your mileage will vary).
  4. My system using inefficient Magnepan speakers and 500 W/ch (amp spec into 4 ohms, I did not measure the input power) will reach 105+ dB peak SPLs with about 1% THD measured. I do not want to be in the room when that happens (I wore sound protection to run the tests; need my ears for the orchestra).
  5. Most people are blissfully ignorant of just how much distortion their speakers generate. It is low enough that it matters little much of the time, and we are less sensitive to distortion as it gets louder anyway.
  6. Given the relative cost of speakers and amplifiers, and my listening preferences, and with the (significant) caveat that speaker power handling must be considered, speaker sensitivity is not a major factor for me (but I do own Maggies so my bias is clear). It is one factor to consider when assembling a system.

FWIWFM - Don

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Old 05-13-2013, 01:23 PM
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On the headroom issue, I feel 10db is preferred.
Not even close to adequate. There are plenty of examples in movies with >20dB peaks and some near 30dB above average.
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Old 05-13-2013, 01:29 PM
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Not even close to adequate. There are plenty of examples in movies with >20dB peaks and some near 30dB above average.

I was talking about typical audio only program material not movies. But I did mean this as a "minimum" figure.

But I agree, the more the merrier.

To listen at a 1w average, and have 30db headroom, you would have to have 1000 watts. Goodbye speakers tongue.gif

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Old 05-13-2013, 01:43 PM
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I was talking about typical audio only program material.
10dB is still poor for music. Some of the compressed loudness wars stuff is around 10dB (some are worse), but well recorded music can easily be 20dB, even on LP. Cordell when actually testing this found a 31dB peak on one recording, so I'm sure there are more out there.
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To listen at a 1w average, and have 30db headroom, you would have to have 1000 watts. Goodbye speakers tongue.gif
On a short term peak? Not likely unless a driver exceeds Xmech.
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Old 05-13-2013, 01:55 PM
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10dB is still poor for music. Some of the compressed loudness wars stuff is around 10dB (some are worse), but well recorded music can easily be 20dB, even on LP. Cordell when actually testing this found a 31dB peak on one recording, so I'm sure there are more out there.

There are exceptions to everything. And I think much of our debate depends on how you define "average".

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On a short term peak? Not likely unless a driver exceeds Xmech.

Very likely considering not one person ive ever known has a 1000 watts (per channel) and given most amps people DO have would be driven to over 20% distortion TRYING to make a 1000w peak.

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Old 05-13-2013, 02:08 PM
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Very likely considering not one person ive ever known has a 1000 watts (per channel) and given most amps people DO have would be driven to over 20% distortion TRYING to make a 1000w peak.

Subwoofer amps tend to be among the largest amps in use. I have a friend with 4 Behringer EP2500 amplifiers, each channel driving a 2 ohm voice coil that is part of a dual voice coil 18" subwoofer. That's over a thousand watts x 8. AC power via is a 30 amp 230 volt dedicated circuit. I have 2 other friends with subwoofers that are only a little smaller.
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Old 05-13-2013, 02:13 PM
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On the headroom issue, I feel 10db is preferred.
Not even close to adequate. There are plenty of examples in movies with >20dB peaks and some near 30dB above average.

The crest factor of music generally runs from about 8 to 20 dB. I don't doubt that are are a few examples beyond 20 dB, but I'm not sure that many people build systems to handle them while listening at high average levels.

Reference level (85 dB) with 2 channels runs a watt or two in most systems, so peak levels might reach 100 wpc. Infrequent brief clipping is hard to detect.

You can play around with system parameters here:

http://myhometheater.homestead.com/splcalculator.html
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