Low-sensitivity speakers — What's special about them?

Thanks for linked article, @alexberger. In real-world scenarios with mostly passively configured, inefficient speakers - certainly approaching to some extent live acoustic (or amplified) levels - Thermal Distortion is an inescapable factor.

@lonemountain --

Focusing on efficiency as a measure of speaker technology or quality is like judging a passenger car based on miles per gallon.

That’s only assuming high efficiency has main priority regardless of other aspects and ultimately sonic outcome - a convenient position trying to make your own point, but hardly the bigger picture.

Low efficiency is a hindrance; never a trait, and as such has that to fight as well in addition to all other areas in speaker design. They’re the product initially of a desire and need for smaller size to cater to a commercial market, NOT because they were deemed better sounding (but of course marketing efforts made their best to sell the acoustic suspension principle as such).

High efficiency and large size as a foundation is giving acoustics their more proper due, but also moves the design, at least partially, into the realm of acoustic transformation. The most predominant enemy of horns it seems, except when they’re bad designs and too small, is passive cross-overs and too shallow slopes. Horns generally don’t like working outside of their "comfort zone" or design specifics here, something active configuration can more readily accommodate with steeper cut-offs compared to (the side effects of) complex passive filters.

So, a high efficiency design properly (and actively) configured is a win-win scenario from my chair, the only real drawback being - to whom it may concern - large size.

There are newer generations of horns that are much better no doubt.  But well known to have lower distortion?  That gem is not in my physics text book!  Maybe I should qualify my comments to apply to normal SPLs in  nearfield applications (home audio)?  Maybe that's what you mean, that at higher SPL horns can measure better?  Over long distances or high SPL I would think could be true, but I'm not sure.  But nearfield?   I very much doubt that horns beat direct radiators in the low distortion game.  Certainly isn't my direct experience in my years in the audio business.   One only needs look to what the best of the best speaker designers of the industry are using for their best nearfield designs- and only in very rare cases (the JBL M1 comes to mind) are horns used.  

Does this mean there aren't horn based systems that sound good?   I've heard some that were very impressive.  But if you want Tom Petty's guitar to sound exactly like the real thing in the studio or at home, off axis and on axis, at listening SPLs we'd really use at home or the studio, Tom's engineer and Tom himself chose direct radiators.  Most of the great records over the past 30 years used direct radiators for monitoring AND mastering.  

Controlled directivity- In a nearfield setting, highly controlled directivity can be a negative for audio quality as off axis reflections are now significantly different from on axis speaker output.  This is a big no-no for authentic reproduction.  In real life a trumpet or a guitar don't create a limited dispersion sound.  Reflections are a natural part of real life music and are needed for authentic imaging.  So authentic imaging needs its off axis output to look very similar to the on axis output, only lower in SPL (level).   Like a guitar playing in your living room, the guitar radiation pattern bounces energy off side walls that recombines with the direct sound at your ear.  This is one big reason why some rooms sound different.  .

A room with highly reflective surfaces (lets say glass sidewalls and tile floors to illustrate the point), doesn't sound good by nature.  A wide dispersion speaker does not sound good there.  These super reflective rooms can benefit by  avoiding sending energy to these highly reflective walls.  This is the time where a highly controlled dispersion loudspeaker (such as a horn) at home pays off.  It could also be controlled by acoustic control, such as drapes or absorption on the sides and rugs on the floor.  .            

Brad  

Did you mean the JBL M2? 

(the JBL M1 comes to mind) are horns used.  

Yes JBL M2- Sorry!.

This efficiency issue is one "spec" out of many that a designer must balance. All these performance parameters are evidence of the enormous number of trade offs in creating a complete driver/box/electronics design. So designers make their own choice ("I want a horn, that’s what I like") and balance everything to favor their choice ( it will have limited dispersion, HF narrowing, but that’s okay I’ll try and minimize it, etc). This is the way speaker design is, balancing hundreds of issues that represent hundreds of choices and all of them have resulting tradeoffs. You may want a low distortion driver but its too expensive, or the OEM manufacturer can’t build it till next year and you’ll be out of business by then. Or, the horn you want to use wont fit the box you already bought or built, or you don’t care about efficiency as amps are cheap so you want the widest bandwidth possible, ..on and on.

There is a practical science at play here, with product development controlled by economics, engineering principles, sales, marketing and a whole bunch of other factors we’ll never know about at the factory that drive those choices. In the end, the company "sells what they have" as ALL speakers are a sum of trade offs. Many of the issues debated are really arguments over someone’s clever marketing points and we as consumers take these marketing issues as gospel, as facts. Since everything is choices, it may be these performance features are important only in THIS type of design. To another design, they don’t matter. Like wide dispersion is not desirable when you are trying to throw sound over a long distance (think football stadium). But to home audio, and wide dispersion means I get to sit on both ends of the couch and hear it properly, that matters a whole lot to me.

The company I work with makes perhaps the best cone and dome drivers on the planet but their speaker cabinets are plain rectangular boxes. Some say the box is everything but in this design 2 of the 3 drivers have their own chamber and the box is not involved in the driver at all. The baffle is more or less "a holder" for position and improves output as there is acoustic gain by sealing drivers to a surface. Some say the box looks old fashioned- so to balance that we use some exotic woods and make them look like beautiful furniture. The best you can do is find a way to make some happy and others will just not see it/hear it the way you do.

These are trade offs made all the time by speaker builders and then we as purchasers and users get to choose if we agree and make the same choices. The funny part is how people, who aren’t acoustics scientists, want to insist their isn’t a choice, there is only one way to do it, and this is it! I know, I read the entire brochure! Or, I saw this demo once that showed XYZ and THAT was the truth let me tell you!   "Their" speaker maker’s choices are the only right ones, they understood it and no one else does.   A comment like this company is the only one "that really understands cabinets" is a very simple view of a very very complex business. Speaker engineering and building is HARD and because its physics, many of the choices are not flexible or open to interpretation. There is a large body of science behind all this that is available to everyone to draw on. I certainly don’t think the brand I work with has the only solution. There IS more than one way to do it and many good sounding speakers out there. Each has its own application set that it excels at and other applications that it doesn’t do well with. We have not arrived at a universal solution.

Brad