I don’t think anybody makes a modern woofer with parameters rivaling those of the Altec 416-8b and 416-8z, so it is rare to find an equivalent speaker today that offers a combination of efficiency and low-end extension similar to that of the Model 19.
Here’s why (as described to me by a veteran prosound loudspeaker engineer): The doping compound Altec used on their accordion surrounds had a unique combination of attributes which allowed an exceptionally high compliance, BUT it was toxic in its liquid state and gave off toxic fumes as it cured. My understanding is that it would be illegal today. Unfortunately modern non-toxic surround doping compounds simply do not rival its combination of attributes.
On the other hand horn design has progressed considerably, and compression driver design has progressed, and some modern prosound or prosound-style woofers outperform the Altec woofers in areas other than their combination of efficiency and low-end extension.
Duke
horn speaker manufacturer who wishes he could build the modern counterpart of the Model 19