Not ideal but I used a substantial sized transformer from Electra Print - it's 3.5k primary and 4, 8, 16ohm secondary - 120ma. My speaker is 8ohm so I just connect the OPT secondary to 4ohm. That reflects back to the primary making it 7K. I'm sure it did not have the appropriate inductance - that can cause a lack in bass (sorry I do not understand why) - it worked beautifully and with a single driver low/full bass is not there anyway. Something to think about if you have a similar transformer in your "storage bin".
-Joe