Powered Speakers: Motorola Lo-Fi

michael

Active Member
Picked up a pair of Motorola speakers w/little tube amps inside, about 18 x 8 x 9. Each has a power transformer using a 6X4 rectifier and a 12AX7(?) driving a 6BQ5. Kinda unusual, to say the least. The front's a fabric grille with volume, bass and treble controls, plus an indicator light; behind that, a two-way speaker system. Outside of a pair of Ampex powered speakers--620's?--I had several years ago, I don't recall seeing any low-end stuff like this. Back's are vented, of course, so the sound's going to be a bit lacking.
Anyone have any info on these?

Thanks,
Michael
 
Depending on the size of the transformers which will decide the bandwidth you can get from the OPTs you have something very nice to much better than that. If nothing else you have a pair of fixer uppers that you can turn into winners. Try and give me all the info you can get off them and I will check my Sam's catalog to see if there is a repair guide published on them.
Thatch
 
We exchanged a couple of emails and I think Mike might have the basics for a great pair of SE mono blocks. He said that both the power and op transformers seemed to be far too large to the task of driving the single full range speakers. So with a beefy power supply and hopefully good wide band OPTs a bit of tweaking might get him a quick, easy and cheap start into SE. There was no Sam's so I sent him to Antique Radio on Gooble to see if there was a Rider's on it and told him about the Texas Bottlehead group on Yahoo so that he might find someone close by in central Texas to help him out.
I of cource wanted to tell him that they were crap and I'd give him $20 for tha pair,............but hopefully we (most important) get someone else on the forum getting into the great sounds and faults of 3 watt SE glory.
When I had some prototype Mullard 3 amps built in England by the transformer designer that Chimera Labs uses for transformers and chokes I had a number of not friends over to listen to these little 6BQ5s bring the performance into my living room. Every one was amazed at the power and bass responce I was able to get before the amps would start to clip driving my 92db speaks. One friend was very shocked as we both like Romantic Warrior and use it as a test standard on each others systems that though the amps could not deliver the bass (or anything else for that matter) at more than around 105 db what he did hear just blew him away. He being not the freak that I am is still happy with his gear or just does not want to spend money on upgrading his sound system. He still comes over here to listen and then watch movies. I might hook him yet.
Thatch
 
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