Is it possible to get 100% efficiency when using a cone driver in a horn system?
In Leach's paper eq. 31 gives the efficiency for a maximum sensitivity design, when Ral (eq. 30) and St are set to the correct values.
Eq. 31 can be written as:
N (Wh) = (0,5*(((Wl*Wh)^0.5) / (Wl+Wh))) / ((1/(((Wl*Wh)^0.5)*Rae*((1/((Wl*Wh)^0.5))^2 / Mad))) - (((Wl*Wh)^0.5) / (Wl+Wh)))
For example, with the following parameters:
Mmd = 0,01515 kg
Sd = 0,012469 m^2
(Bl) = 13,04 T.m
Re = 10,8 Ohm
and a cutoff frequency of 70Hz (Wl becomes ~439), then you'll see that N=1 for Wh ~ 1120 (Fh = 178)
This means an efficiency of 100%, together with maximum sensitivity accross the horn's bandwidth.
Did I make a mistake in my calculations or is this a design with very nice properties??
In Leach's paper eq. 31 gives the efficiency for a maximum sensitivity design, when Ral (eq. 30) and St are set to the correct values.
Eq. 31 can be written as:
N (Wh) = (0,5*(((Wl*Wh)^0.5) / (Wl+Wh))) / ((1/(((Wl*Wh)^0.5)*Rae*((1/((Wl*Wh)^0.5))^2 / Mad))) - (((Wl*Wh)^0.5) / (Wl+Wh)))
For example, with the following parameters:
Mmd = 0,01515 kg
Sd = 0,012469 m^2
(Bl) = 13,04 T.m
Re = 10,8 Ohm
and a cutoff frequency of 70Hz (Wl becomes ~439), then you'll see that N=1 for Wh ~ 1120 (Fh = 178)
This means an efficiency of 100%, together with maximum sensitivity accross the horn's bandwidth.
Did I make a mistake in my calculations or is this a design with very nice properties??
I have used TAD compression drivers (and others) in large 180 cycle flare tratrix horns and it sure seems within a certain area they are purely efficient - off axis it's quite a bit different -
Probably the most efficient midbass system I've had is this one with a compression driver down to 80 hz - below that was three horn loaded 18's across the front wall
Probably the most efficient midbass system I've had is this one with a compression driver down to 80 hz - below that was three horn loaded 18's across the front wall
An externally hosted image should be here but it was not working when we last tested it.
"Is it possible to get 100% efficiency when using a cone driver in a horn system?"
No; it would take a diaphragm with zero mass and wire with zero resistance.
IIRC the theoretical max is 50% for a horn.
No; it would take a diaphragm with zero mass and wire with zero resistance.
IIRC the theoretical max is 50% for a horn.
noah katz said:
And I've heard that horn! 😀
Western Electric 15A Horn, 1950s vintage Westrex Driver.
Very close to 50% efficient. But only within its angle of dispersion. Was about 115dB/1W/1M.
Magnetar said:
Is this some sick goto/ale drivers with sportscar prices or are they something I should know about? Compression down to 80hz.. Jeez.. That would be the perfect midbass mates for my 350Hz TAD 🙄
Rocky said:
Nope, Emilar EC600 - when loaded in the right horn they go pretty low. I had them in the BIG Emilar mid horn on the floor and they did pretty well. Around 112 db/w/m from 80 to 3k. They use a 6" aluminum diaphram and a mylar surround.
An externally hosted image should be here but it was not working when we last tested it.
They are hard to find and not too expensive. The Community M4 is simular as well as the Adamson. I had the Adamson and didn't like it as well. It uses a 10" kevlar diaphram.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
"Very close to 50% efficient. But only within its angle of dispersion."
Efficiency is not determined by SPL on a particular axis; it's total acoustic output power/electrical input power
Efficiency is not determined by SPL on a particular axis; it's total acoustic output power/electrical input power
noah katz said:
I did make a mistake in my calculations, in my example Qmc becomes negative, so the calculations aren't correct. I already made a new efficiency formula, which seems to work well. Now I'm able to calculate a maximum sensitivity design with a chosen efficiency.
Maximum efficiency point for my drivers occured at ~67%. Anyway, 50% is enough for me 😀
noah katz said:
You are correct, sir! Terrible post on my part.
Sensitivity can will rise if we put the same about of power into a smaller angle. Efficiency will not.
But here the angle IS important, and you've left that out.
The same amount of power in a more narrow beam will give a higher SPL than in a broad beam. Light works the same way.
1 W acoustic power into free space generates a sound pressure of 109 dB SPL at 1 meter. That's thru 360 degrees in all directions. If we can focus all that power into a "beam" that is only 90x90 degrees wide, then SPL within that beam will go up.
So to say "50% is 121dB/1W/1M" doesn't work, unless we know the angle. Obviously we will not get 121dB into 360 degree free space. 109 is all we get.
That 1 watt of power (or 1/2 watt, if we are 50% efficient) has to be narrowed down into a tight beam to get 121dB, or even 115.
Does that make sense?
panomaniac said:
Yes.
In other hand, I never understud wish for very big efficient for home use. Like: "I want 125 dB at 16 Hz (with 500-1000 W power)", and things like that.
Agreed, furthemore people would attenuate very high efficency speakers to match a less efficient woofer or to be able to use knobs normally...
Very high efficiency is actually a big point, due to the wattage needed, as all sorts of ancient directly heated triodes can be used. Ofcourse, biamping is a necessity unless you have über sensitive bass horns for the bottom end. My very efficient TAD4001 setup with round horns (flea powered by 12A/71A DHTs and with passive TVC line stage) beats the crap out of *anything* I've heard in the frequency range they cover. Integrating them properly with a biamped bass system is difficult, but not impossible. So for those not padding away the efficiency, high efficiency does make sense.
Rocky is correct.
And even in a passive system, high efficiency can sound better than anything else.
It's not a matter of getting super loud SPL at home, it's matter of the compression driver having to move very, very little to give you the ~100dB levels you might need. Distortion drops to very low levels that way.
I have heard and used big Altec passive systems where the horns had to be padded down to match the "low" (100dB/W) sensitivity woofers. The sound was amazing and more dynamic than any other system I've ever heard.
There is plenty on this subject to be read on the web, so I won't beat it here. But high SPL is not the only reason for high efficiency, even padded down it still sounds amazingly musical.
And even in a passive system, high efficiency can sound better than anything else.
It's not a matter of getting super loud SPL at home, it's matter of the compression driver having to move very, very little to give you the ~100dB levels you might need. Distortion drops to very low levels that way.
I have heard and used big Altec passive systems where the horns had to be padded down to match the "low" (100dB/W) sensitivity woofers. The sound was amazing and more dynamic than any other system I've ever heard.
There is plenty on this subject to be read on the web, so I won't beat it here. But high SPL is not the only reason for high efficiency, even padded down it still sounds amazingly musical.
"In other hand, I never understud wish for very big efficient for home use."
To add to what others have said, it's not so much the need for high average SPL, as the capability for very high peak SPL, so that at normal levels there is low distortion and output compression.
To add to what others have said, it's not so much the need for high average SPL, as the capability for very high peak SPL, so that at normal levels there is low distortion and output compression.
454Casull said:
Greets!
Right, a horn can only theoretically attain 50% efficiency since half of the input power would be lost as heat due to thermal power compression.
GM
GM said:
Thanks for that, GM.
When we had set up the big W.E. 15a horns, Jean Hiraga, who owns them, said they were 115dB/w. "That's close to 50% efficient, the theorical limit" he said.
Never was sure why 50% was the limit for a horn, never researched it, just took it on faith. Worth looking into. Knowledge is good.
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