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JBL 4349 Review (Studio Monitor Speaker)

changer

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What does constant directivity mean to you? To me it means the directivity index sees no change through the frequency range. This speaker sees a narrowing as frequency increases, like most speakers do.
There was a similar discusion recently at another place https://www.diyaudio.com/forums/multi-way/375458-constant-directivity-home-post6749276.html and in this context constant directivity is synonymous with uniform directivity, not as in public adress systems an actual constant directivity throughout the speaker's bandwidth. Therefore, you will also find that Don Keele spoke about a constant-energy response monitor, the goal beeing no directivity errors. https://www.pearl-hifi.com/06_Lit_A...her_Publications/Improvements_Monitor_LSs.pdf
 

Chromatischism

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But a speaker that has no directivity "errors" (defined in the CEA2034 format as sudden changes in the directivity index trend) yet still narrows as frequency increases has variable directivity, not constant – just using the literal definition of the words.

This is an example of a constant directivity speaker for much of the tweeter region. Notice how the DI does not change from 3000-10000 Hz:

index.php


Another, coincidentally also a JBL:

CEA2034 -- JBL M2 (Crown iTech 5000 Amp; M2 Base Configuration).png


Definitions:

From Princeton:

Abstract

"It is often desired that a transducer have a polar radiation pattern that is invariant with frequency, but there is currently no way of quantifying the extent to which a transducer possesses this quality (often called “constant directivity” or “controlled directivity”)."

Introduction

"Many applications in audio benefit from transducers (or transducer arrays) whose directional characteristics do not vary with frequency. For example, in live sound reinforcement, it is often desirable for each loudspeaker to cover a certain region of the audience. Consequently, the loudspeaker’s coverage angle should be constant over its usable frequency range so that no part of the audience lacks any part of the frequency spectrum."

Conclusions

"Motivated by the lack of a precise, standardized definition of constant directivity, and of metrics that quantify the extent to which a transducer exhibits constant directivity, we derived a set of five metrics, each of which satisfy one or more of three criteria for constant directivity specified in Section 2. These criteria were also used to define the term “constant directivity” as either a characteristic of a transducer whose polar radiation patterns are invariant across a specified range of frequencies, or, more leniently, as a transducer whose directivity factor (index) is invariant with frequency."

For consistency, it is much the same in electromagnetics – from Wikipedia:

"In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction. It measures the power density the antenna radiates in the direction of its strongest emission, versus the power density radiated by an ideal isotropic radiator (which emits uniformly in all directions) radiating the same total power."
 
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Valentin R

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Yeah, it still has some beaming, but a ~5dB increase would for sure make it sound much more neutral. Oddly, the manual says the horn center should be ear level.

If Amir really wants to sell these, maybe he should remeasure them :p
Well the design axis is at the bottom of the horn
Not at the center of it
That’s 5 inches of distance ( it does make a difference)
 
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