Suitable Enclosure

[TNA]

Would anyone have suggestions fro dimensions for making a suitable enclosure for the speaker in the photos. This will be used with a 1928 RCA Radiola 18 radio, so I don't expect anything miraculous for sound, although, given the age, it isn't too bad. This speaker isn't too far off for an impedance match for the 71A output tube, and avoids buying a matching transformer.

The enclosure is primarily to protect the speaker, but as I'll need to make it, it might as well be somewhat compatible. I don't have any specifications for this speaker, and suspect it was open baffle, probably mounted in a ceiling originally. I'll probably set the enclosure on top of the Radiola case, which is ~ 27 1/2" W X 8 3/4" H X 7 1/2" D. It could also be set under the case. I'd like to avoid anything too large, and suspect bass output from the Radiloa doesn't justify too large a volume anyway. I can duplicate the original pot metal speaker enclosure shape in wood, but perhaps someone will have a better suggestion that may improve the sound somewhat.

Thank you.

[billfitzmaurice]

You can probably get a much better result than the original, but to do so you'd need to measure the specs yourself.

[Chris Roemer]

Since no one will see it, why not use something new (like an AURA NS3 / Dayton ND90) ?

[TNA]

I could, but would still need a matching transformer between the 71A output tube and the speaker. The Jensen actually sounds fairly good compared to the original, there's a little more high frequency.The original produces a slightly muddy midrange. There's also no tone control, only volume, and that, quite remarkably is a rheostat directly in line with the antenna, that is, the antenna input connects directly to the rheostat before any amplification or filtering. The Jensen matching transformer isn't ideal, but close enough.

[LOUT]

I'm going to throw out a random-ish guess of about 1.2-1.5cu-feet (around34-42liters...or something like 27.5"W x 12"-14"T x 7.5"D) with a ~45hz tuned port (around 3"-diameter x 4"long).
Just because that happens to work okay-ish with some 7"-8" high-efficiency, low-mass, low XMAX drivers that some older drivers tend to have some similarities with.
Like I said, pretty much a total guess.
I'm honestly having a bit of a rough time simply guessing the driver diameter..sorry.

[TNA]

Sorry, I didn't think to include that, it's 8". They are PA speakers, as I understand it, the transformer is to use them with a PA amplifier that produces 70 Volts. The 71A requires an impedance of around 2K Ohms. From what I could find regarding these radios, the matching transformer is probably close enough to that impedance to work. The sound was fairly good through the Jensen, better than the through one of the 2 original speakers I have. I need a 3rd speaker as I have 3 of these radios.