|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
|
|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
In Reply to: RE: He already has that one posted by bwaslo on July 2, 2015 at 20:32:20:
Hi Bill
A plane wave tube response for a compression driver is essentially the same as a truly constant directivity horn except for level.
In this case, there are no drivers which have 110dB 1w sensitivity up high because the mass roll off begins around 2K for most 1 inch exit drivers and about an octave higher for drivers like the TAD.
The only way to get flat response on axis without compensation is by using a horn who's directivty narrows at a rate that compliments the fall off in electro-acoustic efficiency.
Conversely, if one examines the impedance curve for a "perfect" 50% efficient driver (in the frequency range it is 50%), one see's a resistive impedance that is 2X the Rdc, half the power is lost as heat (Rdc) while the other half is radiated. At the upper end of the frequency range, the mass controlled roll off becomes sharper due to the inductance which raises the impedance and the sum often gives that nice curve as the mass break is added to the inductive roll off gradually.
For an omni directional point source, 109 dB 1w 1m is 50% electro-acoustic efficiency and 112 would be 100% so "up high" figures in this neighborhood or higher certainly include directivity for example a horn with a directivity index of 10 increase the on axis level by 10dB over the driver on a CD horn.
The part of the horn that governs the directivity up high is near the throat or even inside the driver and can be seen by Don Keele's pattern loss formula. If one knows the horn wall angle and dimension (inches) inside the horn or at it's mouth, one can figure out where the pattern loss is. That thumb rule is for frequency = 10^6 / (angle X dimension) or for the dimension where pattern control is lost (inches)= 10^6/ (angle X frequency).
Working through a curved wall horn, one can follow why they narrow up high and why a CD horn must have a lower spl on axis.
Best,
Tom
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: He already has that one - tomservo 06:30:56 07/03/15 (1)
- RE: He already has that one - bwaslo 14:26:48 07/03/15 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
