I like your idea of a Mono Garage speaker, next is: what content?.
I just finished listening to Benny Carter Quartet Mono, 1959, ’Swingin’ the 20’s’. Mono cartridge, preamp L+R > L speaker only.
As I write, I just listened to a Stereo LP the same full mono way, Oscar Peterson ’Soul-O’, also 1959, getting horiz info only.
I’m playing it now with Stereo Cartridge , (get both horiz & vert info); then preamp MONO mode (both speakers, same signal). Let’s me know how well the L-Pads are matched L and R speakers, a full centered image without frequency wander to either side.
Next will be full Stereo. Sometimes, solo piano, stereo, is mic’ed in a way that it sounds like the worlds biggest piano, some frequencies left speaker, some center, some right, very strange if in centered ’imaging’ spot. I thought I’d start full mono, then move ’up’ to hear the differences.
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back to your speakers
1. impedance: you can research and measure, see what the crossover says if labeled. I suspect 16 ohm drivers, thus best if the amp has 16 ohm taps. my vintage tube amps and my newer Cayin have 16 ohm taps, few modern amps do, even my cayin A88T, only version one has 16. 16 ohm drivers might measure i.e. 11.5 ohms when idle, only research will let you know what’s correct, but you will get clues.
2. level control between the woofer and horn(s). Many vintage, nearly all Electrovoice packages and their combo of drivers/crossovers were designed with L-Pads, half-attenuation being ’normal’, less for dull rooms, more for live rooms. i.e. my 3 way have two L-Pad AT-37’s (16 ohm versions): one for adjusting the mid horn to the woofer; another for adjusting the tweeter horn to that mix. not interactive, simply individual attenuators. However, L-Pads, not Pots, as L-Pads maintain the impedance shown to the crossover at any position; pots alter the impedance which alters the frequency response.
new high quality L-Pads are available, some 16 ohms, IOW: if originally present, they are needed to achieve the original designed frequency response.
perhaps L-Pads were not needed in the theater, but if they don’t sound right in your garage, you might rig a temp attenuator, see if it helps things. Of course preamp tone controls can help but not like individual driver level controls.
3. 15" woofers, that old, can be re-coned, however the surrounds might be pleated cloth type, new foam or rubber surrounds will not be ’right’. The coil?
best of luck, I would do a new enclosure last, after they prove themselves worthy.
