Dipoles - Thorsten, what changed?

[ChrisPa]

Thorsten

Just been looking at the 'JASD' thread on diyAudio, because of a reference you made in another thread (interested in building some low cost dipoles for a simple high-quality PA system application - and maybe I'll like them for hifi).

In the JASD thread, post #99 diyAudio Forums - 'JASD' (Just A simple Dipolspeaker) makes reference to the use of a "Thorsten Curve"

This post then provides the following link:Suggested target curves and setup techniques for the Behringer Ultracurve digtal

And it raises a question where I'd be interested in your answer.

The section of particular interest is:

The key to much of percieved tonality is the behaviour of room and speaker though the reverbrant range, because in this range we find the fundamentals of most instruments and the human voice as well as all the harmonics. Above I commented that in reverbrant range the speaker behaves a lot like a light source.

For a long time two specific types of speakers have been sold to the unsuspecting public that have by design severe behavioural problems in this range. One type is the Full Range Dipole and the full range omnipolar speaker. Neither type is found in serious Studio or sound reinforcement applications for exactly this reason.

Dipoles and Omnipolar Speakers create way more problems than they solve, by radiating energy over a very WIDE frequency range and also a very wide area. Think simply of a naked lightbulb in a room. THis is your omnipolar speaker and to a lesser degree your dipole. this makes the frequency response in room within the reverbrant range maximally dependant on the room symetry, absorbtion etc. and thus will require major efforts on room treatment to correct for the problem. Of course, a notable minority of listeners actually likes the presentation of omni's and full range dipoles and they by all means are welcome to their preference.

So, is the above quote your's? (are you the Thorsten in the 'Thorsten Curve'?)
And if so, my question is, what changed in your thinking?

Not trying to pick holes, just trying to understand what happened to cause you to change from criticising dipoles, to building them.

Thanks

Chris

 

[3DSonics]

Hi,

So, is the above quote your's? (are you the Thorsten in the 'Thorsten Curve'?)

Yes, it is.

And if so, my question is, what changed in your thinking?

Nothing really. The version you have quoted is an older pre-release of the final document and contained a number of errors, omissions and lack of precision.

The later version available from my own Yahoo Group (see link below - you must be subscribed to yahoo groups though to read it) reads like this:

http://groups.yahoo.com/group/Thunderstone_technical/files/TL Circuits/Ultracurve/PADEQUSE.HTML

"For a long time two specific types of speakers have been sold to the unsuspecting public that have by design severe behavioral problems in this range. One type is the Full Range Dipole (Electrostatic or Planar) and the full range omnipolar speaker. Neither type is found in serious Studio or sound reinforcement applications for exactly this reason.

Dipoles and Omnipolar Speakers create way more problems than they solve, by radiating energy over a very WIDE frequency range and also a very wide area. Think simply of a naked lightbulb in a room. This is your omnipolar speaker and to a lesser degree your dipole. This makes the frequency response in room within the reverberant range maximally dependant on the room symmetry, absorption etc. and thus will require major efforts on room treatment to correct for the problems caused. Of course, a notable minority of listeners actually likes the presentation of omni's and full range dipoles and they by all means are welcome to their preference."

There are other sections on the usefulness of Dipoles in modal range in the document as well.

The key is to understand my designs and why they are fully in agreement with my criticism of full range dipoles (ESL's and Maggies etc.) is that even drivers with rather skelletal frames roll off quite rapidly behind the driver towards higher frequencies. So they operate as dipole only up to a given frequency, which is determined by the driver design.

Here a measurement taken by Siegfied Linkwitz on a fairly "open back" driver on a circular baffle:

One can see the rear radiation at 2KHz down by nearly 6db.

As a result classic cone drivers behave as dipole only up to a few hundert Hz (300-800Hz) or at worst to 1-2KHz, above that they are in fact quite directional monopoles.

So, "Dipole" <> "Dipole" if one uses dynamic drivers and the other planar drivers.

Ciao T