What determines Efficiency?

[stelleg151]

Forgive me if I am wrong, but from what I have learned, efficiency and the ease with which speakers can be driven are positively correlated. I havent been able to find exacly what determines efficiency, though.

My interest in high-efficiency speakers has come from my newfound interest in T-Amps, which as most of you probably know, arent the most beastly amps out there . So I would like to build some high efficiency speakers to match with a nice high efficiency T-Amp, so that I can bask in low-power, high efficiency Hi-Fi.

Anyways, if someone could give me a brief explanation or point me in the right direction I would be much obliged. I would consider any design too, from exotic acoustical fullranges to 3-ways to multi-driver speakers (I feel as though I remember seeing a pair of speakers that had about 6 identical mid drivers and that they didnt require much power to drive to reasonably loud levels).

But mostly I just would like to know what determines the efficiency of a speaker.

Thanks,

George

[ShinOBIWAN]

Quite a few things determine efficiency.

Moving mass, suspension, magnetic flux density, coil length, coil-gap clearance and so on.

Very simply put:

Its fairly complicated game of balancing the figures. You can have very high efficiency but you trade other things to achieve this and vice-versa.

[stelleg151]

Thanks for the reply. I guess everything in life is about balance, so of course speakers are too.

Howabout enclosure design considerations(horn designs and fullrange in particular) and number of speakers per cabinet, do these factors play into efficiency? And are there any sort of guidelines as how to approach this balance from a high efficiency point of view?

For convinience Ill put a list of things Ive seen that possibly increase efficiency, so please correct me if Im wrong or misleading.

1. Horn acoustics.
2. High SPL drivers.
3. Bipole drivers.

Short, but I am pretty new and still looking around. Any suggestions would be appriciated.

Thanks,
George

[tinitus]

well, I think crossovers plays a important role in this....let me put it this way.....a low efficient CSS FR125 without crossover will possibly be easily driven by your T-amp...but if you want to play loud the easy way is with a good fullrange....and there are a number of options and configurations available

maybe you should ask about this at "fullrange-forum"

[stelleg151]

Hey tinitus, thanks for the insight.

I wasnt sure if fullrange were easier to drive, which is why I asked the question here. I also have heard that fullrange can sound better with T-Amps so perhaps I will ask the question there as well.

Thanks,
George

[Rademakers]

The 2 formula's say it all:

5,44 e-4 x BL^2 x Sd^2 / (Re x Mms^2)

9,6 e-10 Fs^3 x Vas / Qes (9,6 e-8 to get the answer in %)

For calculating sensitivity use n0 (not in %). 112 - 10.log n0 = sensitivity in dB/W/m.

Now you can see that you'll trade (smaller) size of the box (Vas) or low frequency response (Fs) for efficiency.

In horn n0/sensitivity is of less improtance as loudspeaker parameters are more or less dominated by the horn parameters.

With kind regards Johan

[el`Ol]

There is no Rms in the term, am I right?

[myhrrhleine]

Originally posted by stelleg151
Thanks for the reply. I guess everything in life is about balance, so of course speakers are too.

Howabout enclosure design considerations(horn designs and fullrange in particular) and number of speakers per cabinet, do these factors play into efficiency? And are there any sort of guidelines as how to approach this balance from a high efficiency point of view?

For convinience Ill put a list of things Ive seen that possibly increase efficiency, so please correct me if Im wrong or misleading.

1. Horn acoustics.
2. High SPL drivers.
3. Bipole drivers.

Short, but I am pretty new and still looking around. Any suggestions would be appriciated.

Thanks,
George

Yep. They all come into play.
It's a balance between efficiency, and cabinet size, and low frequency cutoff, and low frequency 'cutoff' rate, etc.

[phn]

To use non-tech lingo, today's low-efficiency speakers rely on brute force. An 8-inch 90 db speaker might produce as deep, if not deeper, bass as a 15-inch 96 db speaker. It does so by moving air. You can feel the air pressure from modern speakers. Figuring everything else is equal, with high-efficiency speakers the only alternative is size, which includes horn designs. A 96 db speaker will sound as loud as a 93 db speaker driven with twice the power. For 90 db you will need four times the power and so on.

I recently sold my ss amp. And since my tube amp decided it was time for some RnR, I currently use a Sonic Impact T amp. I had it laying around. I had only tried it briefly with batteries once. Had no SMPS. I still have a hard time believing the power (about 2x6 useful watts) and authority from something that tiny using a 30W SMPS smaller and lighter than my Nokia! My ten times as powerful solid-state amp is getting r***d by a toy!

Open baffle could be an alternative.

[tinitus]

Entertaining reading guys, but I think George is more confused than ever
You are without much experience so...
1. I will rule out horns, which I think demands some knowledge to get right
2: OB=open baffle, that means no box, just a "plain" simle plate with the driver, but I believe thats for hardcore enthusiasts, but who knows
3. Quaterwave - easy to build, and with a lot of potential, and I will recommend you to look into Martin King

http://www.quarter-wave.com/Projects.html