I've followed the B15 original vs. B15R debate for a while. And thanks to all that have put their ideas on the table. Time for my 2 cents. I know, opinions are like $#&%*!@^; everyone has one!
I've owned 7 original B15's since 1978 and a B18x head with later (Ampeg-Magnavox) Altec 421A based B15 cabinet which was the best combo of them all. I sold all off I had 6 years ago. Just bought a B15R. I tested it for an hour playing alone. Sounded wonderful and got plenty loud. I took it on a gig with a loud blues trio. Guitarist has a Fender Deluxe Reverb '65 reissue which he runs at full tilt. We run a medium sized PA. It took all night till I found the right settings. But at the end it could just about cut it for stage volume on the loud tunes and on the low to moderate volume tunes, it ran fine, even without a direct out to the PA. I didn't compare the new B15 to the old ones.
Old vs New. I've read the posts about the 'R' being kind of a dog. I spoke to Jess Oliver, the designer of both the original B15 and a key consultant on this reissue. He feels that the new amp does a lot more than the old amp and is improved in many ways, most noticeably in power and the ability to deliver the low 'B' string. However, he said that this extra bass changes the sound so many think the new amp is different and to some, not as good. But, you have the ability on the 'R' to dial in the old amp sound by switching to the 60 watt setting, turning off the tweeter and reducing the bass control. This is not to say the new amp is the same as the old - it's been updated in an honest attempt to make an improved version that includes the original sound in its new format. I believe this fully. This is not just an ill-conceived reissue as it seems to be portrayed from time to time.
Knob settings. This is not an intuitive design to me. The tube bias and impedance selector switches are goofy and the manual doesn't explain what setting is where. I definately had them in the wrong position and the amp sounded inconsistent. The input volume needs to be run up from half to full. The output volume (master) can't exceed half. This is very different than the original which had a single volume control. I wonder if some of the owners of the 'R' never found the right settings which led to their dissatisfaction.
Improvements. I had the 'R' and an original side by side (but I didn't compare sound - sorry!). The new amp seems better built. The logo is metal (not sure if the original was, but this one seems heavier), the corners are screwed in instead of nailed on, the cabinet plywood is that nice 11 ply stuff as opposed to the standard lumber yard construction grade on the original, they went to a single channed head with lots of tone adjustments, the power and speaker cords detach, the transformers are much bigger, you can choose between 2 or 4 output tubes, and on and on...and it sounds real nice too.
Weight. The new amp is somewhere between a B18 and a B15 in size and heavier than the B18 in weight. But the weight is offset by the fact that I always carry the head and cabinet separately. So in this regard, each are about 50lbs and very manageable. The 'R' did not fit in my car trunk though (not a big trunk) as the original would have.
Old amp condition. This is a real wild card. The problem is that the original amps are now 40+ years old. Not being an engineer, I really don't know what I'm buying when I get an original. I was told the electrolytic caps would be leaking oil in an amp of that age and if changed to a different cap, would alter the sound. And that's just the caps. The age can affect a lot of the parts and thus the performance. Sure, if you find a 'closet classic' or can rebuild one to original spec, go for it. But be prepared for the cost and the fact it is a rebuild.
Flexibility. The 'R' has lots of options the original didn't allowing for the use of 5 string basses (according to Jess) and many more tone choices.
Ampeg goes overseas. With the company shifting most or eventually all production to Vietnam, will the US made 'R' become a classic in its own right?
Final thoughts. The 'R' is a beautiful, updated tribute product that does more than the original. I love the sound and it has Jess Oliver's seal of approval. Does the sound match an original if you dial it in carefully? I didn't do the demo. But how valid would the demo actually be? Here's why. My favorite B15 back in the 70's when these amps were only 15 years old was a B18/B15 Magnavox-Altec. And that was picked after extensive sound testing with 5 other B15's in the same room. So even back then, I didn't pick an 'original' as my chosen amp. Now, with the originals being 40+ years old, I don't know what I'd be testing against.
The short of it is the original B15 is the low-volume tone standard for electric bass. I wish I had stashed a few away in a closet. Since I didn't, I'm glad the 'R' is there. And even if I had a mint original, I might still own an 'R' (and maybe a real original B18 too!) YMMV.