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General speaker questions for audio and home theater.

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RE: To set the record straight on this antique JBL stuff...

Posted by villastrangiato on July 13, 2012 at 05:11:37:
There is way too much incoherent babbling by Thorsten above to correct point by point. So I will reiterate and re emphasize the main underlying problem as it seems Thorsten is intent on spreading his confusion to others. Thorsten doesn't know constant directivity from the tip of his nose. A given loudspeaker's beamwidth or radiation pattern cannot vary all over the place as it does with the D130 and 075 JBL and produce a constant directivity result. As the name implies, "constant" directivity means that as frequency increases across a loudspeaker's operating spectrum, the portion of radiated sound in a given direction remains essentially CONSTANT. A cursory look at the graphs I posted demonstrate clearly that the drivers in question are not capable of constant directivity - particularly over the frequency bands Thorsten was suggesting for them. Thorsen saying the 075 bullet tweeter maintains constant directivity is a clear indication that he doesn't have a clue what he's talking about. Over a +/- 20 degree window, practically every driver in existence will appear to have constant directivity. True constant directivity implies uniform radiation pattern with frequency over a wider angle - a design objective for high fidelity in a near field listening environment. Toole, who essentially wrote the book on directivity of loudspeakers, makes it pretty clear in his papers that response off axis to about 60 degrees needs to be a carbon copy of the on axis response (excepting a minor uniform level of attenuation with each increase in off axis angle). If the reader of this thread has any doubts, the Revel Ultima Salon 2 (a product design inspired in part by Toole) I linked to earlier possesses a directivity plot that is TEXTBOOK constant directivity. The response plots of the JBL D130 operated wide band and the 075 bullet tweeter responses look nothing like this. Neither do the plots of the Tannoy 12 inch two way referenced by Thorsten. Compare the plots of these speakers and you will get a better understanding of what constant directivity means and why constant beamwidth only suggests constant directivity when it occurs over a relatively wide listening angle. Forty degrees listening angle is clearly not in the same ballpark as 120 degrees. It might be in Thorsten's warped, myopic world view but not where real loudspeaker designers are concerned. Thorsten, given that every successive post of yours on this subject has provided further evidence of your ignorance on the subject, it might be wise for you to stick with electrical fuse design.

(ROFLMAO)