Speaker Efficiency

[pds]

<font color='#000000'>Why are speakers so different in efficiency? &nbsp;Two speakers that look exactly the same can vary from 84 to 94 or even larger &nbsp;disparity in efficiency rating. &nbsp;What is the purpose of designing an inefficient speaker??? &nbsp;It would seem that an inefficient speaker wastes an awful lot of amplifier power for no purpose. &nbsp;My current speaker system is a 12 inch 4 way and has a 94 rating. &nbsp;You would think that such a large speaker wouldn't have such a high efficiency rating and would take more power than a smaller speaker.

I am not speaking of electrostatic or ribbon speakers which are totally different in power requirements than cone speakers. &nbsp;Any ideas???</font>

 

[jeffsg4mac]

<font color='#000000'>Good question, I know Macintosh did it just to sell their big 500-watt amp. Every speaker I ever built had over a 90db sensitivity. It is hard to make an inefficient speaker, you have to go out of your way to do it. I would never buy a speaker that was under 88 or 89 too hard to drive.</font>

 

[annunaki]

<font color='#000000'>Remember to keep in mind that efficency is not a good factor to use into which speaker would be louder. I would like to see a blind test done to see if some people here could actually discern which speaker is more efficent than the other using a modest 25 watt per channel amplifier. Especially if they were matched volume wise.</font>

 

[markw]

<font color='#000000'>Speaker design is a trade off between three main things.

1) &nbsp;Extended bass response

2) &nbsp;Small physical enclosure size

3) &nbsp;High efficiency.

You can have two, any two, but not all three.

Once you decide what you can live without, you can go ahead and design the speaker of your dreams.

And, unless one is into flea power, efficiency is not the most important factor in choosing a speaker. &nbsp;I'd rate overall balance at the top of my list.</font>

 

[av_phile]

Much of the work done to drive speakers are wasted in the form of heat. Heat from the voice coils of the drivers. And heat from the resistors, coils and capacitors in the dividing network. The more complex the dividing network, the less efficient overall. But why use comlex dividing networks. THis is where voicing the design comes in. Dividing or crossover networks have to be matched with the individual driver's response curves to effect a smooth curve across all the drivers employed. To do so may require the use of attenuating resistors, notch filters and steep filtering slopes that require more RLC components. All these enhancements can result in a more pleasing extended frequency response curve for the speaker in its entirety. But often at the expense of efficiency. Some of the most expensive and excellent sounding exotic speakers have 85 to 87 db sensitivity.

 

[petermwilson]

Hil
I use Totem as my main (music listening) 5 speakers. They are 4ohm and have a sensitivity of 87. Fortuneately my Denon 5800/03 at 170w perch has the juice to run them but if I were to move up from the Model 1's to the Mani 2's I would need more amps.

I love these speakers. I have no idea how ohms and sensitivity decisions are made. I have heard (not owned) fantastic sounding 8ohm speakers with a higher sensitivity.

Totem is not really in the amp business, so there must be some other reason for these decisions, I just don't know what they are and I guess I'm not helping this discussion much.

Peter m.

 

[zipper]

I'm curious about this. I just got my Axioms M60's a few days ago & one of the 1st things I've noticed is power required to achieve the same SPL as the Boston VR-950's that they replaced. The Bostons claim a sensitivity of 90.The Axioms claim 93 (or 89 anechoic).
The Axioms don't achieve a good listening level until I turn my Yamaha 3300 up to -50db. The Bostons were good at -62. Loud for the Axioms is @ -26 compared to -35 for the Bostons. These are approximate settings but I think you get the point. Max input for the Bostons is 150 watts,250 for the Axioms.Does this seem right?
Trust me, I'm still playing with the Axioms but it's obvious already that they are superior to the Bostons, but this is what I'm hearing.
For the record,the list price for the Bostons was $760/pr. The Axioms $800. The Axioms are CLEARLY the better speaker. Hands down.

 

[annunaki]

One way to tell for sure that one was more efficent than the other, if the impedance stayed the same, is to check with an SPL meter. Check the Bostons at -62db then check the Axioms at the same level. What is the difference? Use pink or white noise. The ear is not a good scientific tool.

 

[zipper]

I guess I'm confused on the "efficiency" issue. I thought the more efficient a speaker was,the less amplitude needed to achieve a certain volume. It doesn't really matter to me,all I know is that the Bostons played louder at the same volume setting than the Axioms do. I'm not unhappy or concerned in any way about this,I was just curious if I understood correctly what "efficiency" ratings are supposed to mean.

 

[annunaki]

You are correct, in that the more efficent a speaker is the less power it will require. It is not a good indicator of how loud a speaker will be however. I was basically hinting that you were using your ears as a judge for a difference in spl. The ear is very inaccurate as a decibel meter. It takes a 3db increase or decrease just for some people to even notice. Most people do not really notice a difference until around 5db. That is why I suggested you use a spl meter. The difference may be more or less than you think!

 

[av_phile]

I'm curious about this. I just got my Axioms M60's a few days ago & one of the 1st things I've noticed is power required to achieve the same SPL as the Boston VR-950's that they replaced. The Bostons claim a sensitivity of 90.The Axioms claim 93 (or 89 anechoic).
The Axioms don't achieve a good listening level until I turn my Yamaha 3300 up to -50db. The Bostons were good at -62. Loud for the Axioms is @ -26 compared to -35 for the Bostons. These are approximate settings but I think you get the point. Max input for the Bostons is 150 watts,250 for the Axioms.Does this seem right?
Trust me, I'm still playing with the Axioms but it's obvious already that they are superior to the Bostons, but this is what I'm hearing.
For the record,the list price for the Bostons was $760/pr. The Axioms $800. The Axioms are CLEARLY the better speaker. Hands down.

It is possible the Boston VR950's sensitivity of 90db was measured in an anechoic chamber which should be rightlly compared with that of the Axiom M60's anechoic response of 89db. And since they're both 8ohms, that would make the Boston at bit more sensitive. But that wouldn't account for what you said is the apparent 10db difference in volume setting for the two to play with the same perception of loudness. So maybe the sensitivity ratings were not derived on a level playing field to make any comparison that can justifiably correlate with your perceptions. Just my thoughts.

 

[petermwilson]

Hi,
Regardless of speakers there so may things out there that can affect the volume knob. My TV cable box is connected to my reciever from both the L/R analog outs as well as a coax out for the digital and HD channels (that broadcast in 5.1). Whenever I'm in the analog realm of channels I need to boost the volume knob compared to when I'm on a digital channel.

Recording levels and therefore playback levels for HIREZ music seems to be all over the map also. Regardless of this though at -50 I don't hear much volume at all and aside from my power hungry Totems I have a Pair of Axiom Dipole QS4's and a pair of Monitor Audio Bronze bookshelfs connected and each channel has its own amp so I would say if you get good sound at -50 your speakers are pretty efficient.

Peter m.

 

[Shadow_Ferret]

Instead of starting a whole new thread, I found this one!

OK, when I'm looking at speakers and they say they have a minimum recommended power of 25 watts, does that mean that you won't hear a peep out of these things until your amp is pumping out at least 25 watts?

Or does it mean that if you have an amp that is rated at 25rms or under you should be looking elsewhere for speakers?

Thanks.

 

[MDS]

Instead of starting a whole new thread, I found this one!

OK, when I'm looking at speakers and they say they have a minimum recommended power of 25 watts, does that mean that you won't hear a peep out of these things until your amp is pumping out at least 25 watts?

Or does it mean that if you have an amp that is rated at 25rms or under you should be looking elsewhere for speakers?

Thanks.

No. If that were the case, they would be silent 90% of the time. The vast majority of the time you will be using far less than 25 watts.

Take the speaker specs with a grain of salt. The minimum recommended power means absolutely nothing; the maximum recommended power has some validity but is generally very conservative and the speakers can generally take far more than that number without damage (at least for short periods of time).

 

[Shadow_Ferret]

The reason I was asking goes back quite a few years, to the 70s. A friend of mine had a 500w rms amp coupled to a pair of early Bose 901s which were so inefficient he had to crank the volume up to nearly half-way before they even started to make a sound.

 

[sjdgpt]

The reason I was asking goes back quite a few years, to the 70s. A friend of mine had a 500w rms amp coupled to a pair of early Bose 901s which were so inefficient he had to crank the volume up to nearly half-way before they even started to make a sound.

Back in those days, the Bose 901's were not as effecient as Klipsch (nothing was as effecient as Klipsch) but at the same time, the 901's were far more effecient than most of the accoustic suspension speakers of the day. I would guess about 90db of effeciency.

What was going on, was most likely the volume control for the preamp was not a linear device, and/or the gain stage was insufficient. Bottom line, just because the setting appeared to be at the halfway point, it didnot mean the output of the amp was at half power.

I remember a MacIntosh Preamp and Amp combo... 1/3of the max position on the preamp volume knob was about 1 watt of power output from the amp... an amp with about 300wpc of power. The preamp was designed for precise control of volume at lower volume levels.