Speaker sensitivity question (1 Viewer)

[robert bartsch]

Long ago, I had a pair of Altec voice of the theater speakers with 15 inch drivers and cast horns. Their sensativity rating was 98DB with 1 watt at 3 feet. A smallish amp of 80 watts or so was sufficent to raise the roof.


Anyway, I have since bought a set of Klipcsh home speakers which I enjoy. They take up less space and still produce clean sound with the modern multi-channel receivers of today. These are rated at 92DB.

Although I never compared the two speakers side-by-side, my recollection is that it the Altecs produce a much higher sound level than the Klipsch's - given the same input power.


So my question is this; there must be a very noticable difference in speaker effeciency rating 92 Vs. 98; right? Why don't they build home speakers with higher sensitivity ratings?


On a hunch, I recently looked at some JBL professional series drivers and many are rated at over 110 DB. Wow, these must crank at low to moderate power levels.

 

[JohnRice]

Because speakers are complex electronic/mechanical systems and sensitivity isn't the only important factor for them.

 

[robert bartsch]

Hey John:
Is it fair to say that speaker sensitivity ratings are a measure, in part, of the strenght of the electro-magnetic field within the voice coil gap?

Isn't this rating indicative of the mechanical efficency of the driver?

Some of the professional series speakers have some monster magnets, super high sensitivity ratings (+100 DB), and can make high sound pressure levels with moderate power. Therefore, isn't a high sensitivity rating beneficial; if not, why are these ratings provided?

 

[JohnRice]

There is certainly a benefit to high sensitivity, but it also has nothing to do with the quality of sound the speaker produces. If your only priority is playing high volume with little power, then sensitivity is all that matters. Most people are also concerned with the sound quality of a speaker.

 

[Robert_J]

Magnet size is not an indication of high BL though. You have to know the size of the magnetic gap, the strength of the magnets, the type of steel used in the motor and the size, windings, layers of wire in the voice coil. All of that combines to determine the BL. Normal cermic magnets are cheap and pretty powerful. Neodymium magnets are MUCH stronger size for size when compared to ceramic magnets. I have a 45 pound sub motor with ceramic magnets and a 20 pound sub motor with neo magnets and they are basically the same.

Moving mass of the cone or dome (mms specification) is a better indication of sensitivity. Also, the frequency range that the driver is designed to play over is a huge factor. A driver can't play a 20hz tone at 100db with 1 watt of power. The current technology isn't there.

Hoffman's Iron Law is also in effect here. It basically says that you trade sensitivity for lower frequency response. Like all of speaker design, everything is a tradeoff when you are trying to reach your goals.

-Robert

 

[robert bartsch]

Well I got a new receiver w/ 130 watts per channel and cranked it up with the 92Db Klipsch towers (4) and center.

The sound level was no where near that of the old Altecs. I always thought the Altecs did an excellent job of reproducing low passages, music, voices, etc.

 

[JohnRice]

I'll be blunt. It is clear your priority is sensitivity and maximum output, so, I suggest getting a set of PA speakers. They are outrageously sensitive (typically well over 100dB) and have almost limitless maximum output. Look at partsexpress.com for numerous options. Your old Altecs were really just borderline PA speakers in less industrial cabinets. You'll be in hog heaven.

 

[robert bartsch]

I suppose speakers are a subjective thing.

It is a fair statement that the Klipsch floors are quality untis but IMO they can't produce the quality sound that a professional cinema speakers.

I'm considering these, which seem like a steel:

JBL Professional 3677 at Performance Audio

 

[JohnRice]

Robert, "quality" is a subjective thing. The more common spelling for your use of the word would be "L-O-U-D", which is not the same as what most people would consider to be the defining characteristic of "Q-U-A-L-I-T-Y".

For your priorities, I would say the JBLs you linked would do the trick, though I expect you can find even more sensitive models.

 

[robert bartsch]

I'm not a fan of loud music.

I think if you listened to some professional studio monitors with compression drivers in a home setting you would agree that home speakers do not compare.

I can say this because I owned the studios for about 30 years! My comparision is based my current system with 4 Klipsch floor tower monitors and a Klipsch center and powered sub through Denon and Onkyo receivers with 105 and 130 watts @ each with THD of .05%, respectively.

I'm assuming some of this relates to the fact that Klipsch's require a moderate amount of power to produce normal listening levels whereas the studios require very little. The other beef I have is the need for a sub in my current system which is not necessary for accuarate reproduction with the studios. The sub is an interesting concept but my complaint is that the lower frequency sound is localized to a single spot in the room.

Oh well, since my Denon has now returned from the repair shop once more, I'm planning to buy a pair of these:

http://www.performanceaudio.com/medi...100/1254_s.pdf


At

 

[Rich Allen]

A properly setup sub isn't localized to a single spot as many here can tell you.

 

[chuckg]

Howdy!

jsut dropping my twenty millidollars here.

Speakers are less efficient these days because it is easy and cheap to build powerful amplifiers. Back in the 60s no audiophile would be caught dead with icky transistors. Tube amps of limited power were the rage, and speakers had to be big to make the sound loud enough to drown out the neighbors tea party. There are still such audiophiles around today, though tubes are a tad harder to come by.

Ten decibels of loudness difference should be twice as loud (or quiet), and therefore a speaker that is ten dB more efficient ought to produce about twice the loudness at the same amplifier output power.

As others have said, efficiency is just one measure. Having a flat response, and maintaining quality over a wide power range are more important than sheer efficiency.

I would tend to disagree, though, with the poster who compared the Altec VOTT speakers to borderline PA. In my experience, PA speakers are harsh nasty things intended only to make the human voice loud enough to cut through the general hubbub. VOTT is way nicer than that...

 

[Robert_J]

If you want high sensitivity and quality sound, then John Janowitz can build you something - studio monitors.

-Robert

 

[JeremyErwin]

How do you reproduce sounds in the lowest octave without a subwoofer?

 

[Sansui 2000X]

A properly adjusted sub is anything BUT localized!! If you sit, blindfolded in a room where a good properly adjusted sub is playing, I promise you won't be able to pin-point it's location.
Paul

 

[JohnRice]

Robert, you are reaching conclusions based on very little actual observation and a great deal of speculation. From what I can tell, you owned a pair of speakers you liked for 30 years, and have determined from listening to one other pair that sensitivity is a panacea and that a sub is of no real benefit.

I can absolutely assure you that you have not heard real bass, based on the two speakers you have owned. You should try it. Also, sensitivity is not the panacea you think it is. You just happened to have extremely sensitive speakers, but that has little to do with the sound you liked from them.

I suggest you do more actual listening to different speakers.

 

[robert bartsch]

OK, a reasonable argument has been made for me to listen to more [different] speakers.

Did I mention, I have a few different receivers and speakers located in different rooms in the house including:

1. Bose/ Denon
2. Klipsch/ Onkyo
3. JBL/Denon

OK, so nothing truly exotic but each of these is designed for the home and the systems provide for an interesting and valid comparision. I'm not sure of the model numbers but none are lower-end units with the Klipsch/Onkyo system being a higher-end system (130 watts and 4 floor towers, a sub, a mid, etc.)

Over the years, I have also spent contless hours listening to equipment in high-end audio stores including Harvey's, a well known retailer in NY.

Now then; How many of you can say you have critically listened to a set of professional reference monitors with compression drivers in a home setting?

 

[robert bartsch]

I forgot to list the Denon/Premier Acustic tower system I have in the bedroom (pure sewage).

Anyway, the information above that says a difference of 10 DB is equal to an increase in the sound pressure level of 100%. Many professinal compression drivers have sensativity levels in excess of 110 BD - 1 watt @ 3 feet; right?

My Klipsch powered sub has a 12 inch driver and the LF sound seems localized to me. I assume these are necessary these days since the main speakers often have 6 inch drivers or so that don't do an adequate job of LF reproduction; right?

 

[SethH]

The localization is likely due to your crossover point. If you set your crossover at

 

[JohnRice]

The previous comment that a 10 dB increase is double is incorrect. Objectively, 3 dB is double and 10 dB is a 10x change. Many people consider 10 dB to "sound" like double though the hard facts disagree.

Regarding using studio monitors for home use, there are plenty of well educated individuals here who can scientifically explain why studio monitors are generally a bad choice for home use. Some factors are their being designed for near-field use in an optimally treated room of limited size. The inverse argument against using them would be, how many of you have rooms in your house designed as recording studios?

As far as localization of subs goes, there are a multitude of reasons. I have personally found it is NOT necessary to crossover so low as 80 Hz for reasonable blending. I good sub (most aren't) properly calibrated and positioned can often be quite a way off from center and still be rather unobtrusive.