Vacuum tube powered subwoofer

[Reap]

I was recently given an  Eveready A-C Model 3 receiver. This radio was built in 1928 and uses a separate speaker. The RF section looks to be burned out and also has cooked/cracked tubes. The audio amplification looks pristine and is even on a separate chassis.  My thought is to pick up a single sub with a high efficiency and make a powered home theater subwoofer.  It's a push/pull design using a pair of Type 27 tubes. I know these were very early tubes in the AC technology and have  very large list of replacement tubes available. What I do not know is which of these tubes would meet the criteria of being affordable and good tubes for low frequencies. Can anyone with the knowledge please advise me on the correct tubes to use and the pros and cons? Also, what kind of power could I expect to get out of this? Here's a list of tubes that can be used: http://www.radiomuseum.org/tubes/tube_27.html

Thank you!

Identical to 27 = C327 = DE-1 = 227 = 127 = A227 = UY227 = ER227 = 38027 = VT-29 = P227_USA = F209 = N27 = 427 = G-27 = CV944 = EY627 = PH227 = MY227 = AC227 = Y227

Similar Tubes
Other shape (e.g. bulb type):
  G-27-S ; M27

Normally replaceable-slightly different:
  AGX2270 ; C-427 ; F209A ; FY227 ; R30

http://www.ai4fr.com/main/page_ham_radio_broadcast_eveready.html

 

[Paul Birkeland]

Push-pull 27's will make almost no power at 8 Ohms, maybe just enough for a really efficient pair of headphones.

Are there any other tubes on the chassis?

 

[Paul Joppa]

And do you have the separate speaker? From that vintage, some radios may have still used telephone handset earphones, coupled to coiled horns. Response is probably 300-3000Hz - no bass, no treble, telephone voice band.

 

[Reap]

There are other tubs as listed in the last link to the description. But they are for the tuners, volume control, and antenna attenuation. Similar tubes though. 26's and such. Yes, the speaker is wired to the desktop unit. I've not yet looked at it. Though I did plan to. If the rest of the unit is pretty much useless I still plan to look more at the speaker. Not because I particularly want it but I know others might.

Ah well, I was hoping to make something out of this. I could make a guitar amp but that's not a good use I think. I would rather make the Bottlehead guitar amp when I ever get around to that. Thanks for looking guys.

 

[Reap]

The tubes in the amp section have actually been replaced by 71A tubes. This was done in the 1940s so I'm going to assume they work fine. They may actually power a very efficient sub in the right enclosure.

 

[Reap]

Well, a little bit of research shows that 71A was the right tube from the beginning. I think someone had written their piece wrong. Anyway, in push/pull this thing is only going to crank out about 2 watts of power. Not enough I think. I wanted a minimum of 15 and was hoping for 25.

 

[Paul Birkeland]

2 Watts is plenty, you just need a pair of 18's and some large boxes...