Home High Efficiency Speaker Asylum

Need speakers that can rock with just one watt? You found da place.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ High Efficiency Speaker Asylum ]
[ Alert Moderator ]

RE: What makes a driver High Efficiency?

The root issue is the radiation resistance, that is the "acoustic load" a radiator feels and is the loudspeakers sound power.
This "load" is tiny and for a single direct radiator is usually so small it is hard to identify in the driver's impedance curve.

For example, in free space, 1 Acoustic Watt radiated from a tiny source (no directivity) produces 109dB at 1 Meter or 112dB at 1 Meter in half space (on the ground). So one can figure that a speaker that produced 92dB at 1 W 1m is approximately 1% efficient and 82dB ~ 1/10% efficiency.

As might be apparent most of the energy going to the driver is used simply moving the mass back and forth, the radiation is a very small part of the load. In fact it is the mass that makes a woofer have flat response, it has an acceleration controlled behavior. The weirdest part is that if one added additional mass to the vc (so it didn't effect the cone stiffness etc), the hf response does not change at all but the low F corner and efficiency both go down..

Hoffman's iron law and several other unpleasant realities make low frequencies the hardest to produce / rather more correctly the same rules apply except the size of the wavelength is much larger and so then is the device. Consider at 20KHz the wavelength is 1/1000 the size it is at 20Hz.
For a given box volume, with the perfect driver for the job, losses about 9dB sensitivity per octave as you lower the low corner F.

Horns can both confine the radiation pattern angle, making the on axis sensitivity higher AND they can also raise the actual efficiency of the system by coupling the load at the big end to the driver at the small end.
Compression drivers appear to be efficient and some are in the mid range but above say 5Khz, most depend on the directivity to get high numbers.

Reality is the actual acoustic power from the compression driver is rolling off starting at a couple KHz and above. On a CD horn (a horn that doesn't narrow down in angle up high in Frequency), the driver's true power response is revealed and so us usually compensated with a 6dB / oct rising EQ to make "flat" response.
Sort of an overview, hope that helps
Tom


Hi Bill
Oops i intended this to be a reply to the OP, not you.
Have a good weekend



Edits: 05/28/23
This post is made possible by the generous support of people like you and our sponsors:
  Kimber Kable  

Follow Ups Full Thread
Follow Ups
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]