Substitute Driver for Horn Speaker?

[Winky Dink]

Now that I have the Atwater Kent 37 up and running, I've turned my attention to a Model H speaker I picked up some time ago. The obvious damage affected not just the base, but the driver case as well.



Despite my best efforts, the pot metal driver case fractured in three pieces while I was attempting to unscrew it. I managed to straighten the base pretty well, and I can piece together the driver case, but both coils are dead as well, so I'm trying to substitute something for the driver.

I know this issue has been addressed many times by many people. I've read several articles and posts about this, but apparently I still don't get it.

The electrodynamic cone speaker that came with the set measures 1200 ohms. I have a 2-inch, 8-ohm, .25W speaker and a 3-inch, 8-ohm, .5W speaker that will fit in the case. I've tried both (with a 1120 ohm 7W resistor in series) and I can get barely acceptable volume from a strong signal with the rheostat cranked up full. Under the best conditions, several people could listen to the radio if they sat close to the horn in a quiet room.

So, what am I doing wrong, or am I expecting too much? I've read about others who have used this system with good results and others who have use old headphones as drivers. Anyone have any experience with this?



Thanks for your attention--I'll appreciate any advice.

- Winky

[mstaton]

You should use a audio matching transformer. Roughly 1200 ohms to 8 ohms. Go see Alan Sr. at Agem in Caldwell. He should have something that will work. Your volume should be much better after that.

[Winky Dink]

Thanks, I may do that.

[Reece]

I've used a 3" PM speaker with matching transformer in a horn and it works fine, and no doubt sounds better than the original anyway. I had room in the base to store the transformer, but it could be in the radio cabinet as well. You actually can use any old output transformer you have lying about from a scrap table set and it should be fine.

[Winky Dink]

Thanks, guys. It works great.
- Winky