Presto Machine Products speaker driver?

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Angus McCarthy
Posts: 760
Joined: Mon Aug 23, 2010 6:22 pm
Location: Bloomsburg, PA, USA

Presto Machine Products speaker driver?

Post: # 46396Unread post Angus McCarthy
Sun Mar 12, 2017 6:25 pm

Hello all, it's been a long time but I'm finally back in a position where I can think about cutting again.

I've recently acquired this piece of Presto-branded equipment, which I believe to be a horn speaker driver from the late 1920s - early '30s.

Image Image Image

It certainly has the old logo, and a Brooklyn address, which makes me think this was a product of the Presto Machine Products Co. - the predecessor of Presto Recording Corp. We know that they produced add-ons and attachments for radios and phonographs, and I believe this is one of them.

Other early horn drivers and headphones have an iron diaphragm that is set in motion by an electromagnet, but this is built a little differently, more like some early loudspeakers I've seen. There is still an iron plate present, but it is much smaller, and is sandwiched between the two poles of the large magnet. This is attached, via linkage, to what appears to be a mica diaphragm - much as you would find in a phonograph reproducer. There is also another possibility - that this was intended to replace the soundbox on an acoustic phonograph, turning it into the sound system for your radio receiver.

The fascinating thing is, while I was checking the coil with my multimeter, I realized that it was generating voltage from noise in the room - it was functioning as a microphone! With the help of modern electronics, we can hear it quite clearly:

https://www.mediafire.com/?7qo2as49ydyyxa6

Has anyone else come across early Presto pieces like this? I would love to be able to reconstruct the horn, or at least find out more information about it.

User avatar
Angus McCarthy
Posts: 760
Joined: Mon Aug 23, 2010 6:22 pm
Location: Bloomsburg, PA, USA

Re: Presto Machine Products speaker driver?

Post: # 60247Unread post Angus McCarthy
Tue Feb 15, 2022 11:44 am

Revisiting this post to note that I eventually learned the proper term for this kind of driver is a "moving iron" or "reed" element. The plan for this example, considering the result from, basically, yelling near the bare opening, is to construct a narrow, straight horn (Edison recorder-style) and use it in reverse as a low-fidelity microphone element. This is actually not entirely out of the realm of original intended use, as these kind of transducers were known to be used in two-way intercom speakers.

Still curious if any other early pieces of Presto branded audio hardware have been encountered in the wild.

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