Revisiting Jim Rogers JR149s
Tony L
Administrator
They work well with a wide range of amps. If you have a search way back in the thread you’ll spot a Naim NAP 120 lurking on a shelf above Jim Rogers in one of the JR brochures linked, I guess he used it whilst designing them. They sound great on anything I’ve used; Quad 303, Leak valve amps, Pass Aleph 3 etc. I bet they’d be amazing with a bit more power, e.g. a Radford STA 25. They’ll certainly show you a nice amp from an average one, but there is nothing hard about the load. I’m clearly at the bottom of the power range with the Leaks, I’d want more that 10 Watts in a larger room. I listen so close to them it is no issue and they really do sound superb.
Agree:;
Have not heard jr149s sounding bad on any of my quad amps and valve amps,not tried them on my sta25 yet....
I have no explanation for this perhaps one of my power amps is better suited than the other? Any explanations greatly accepted.
Tony L
Administrator
It is the potentiometer pictured on the crossover on the previous page. I’d start with it at its middle setting and fiddle from there. It is quite subtle and IIRC is the opposite to what one expects in that counterclockwise is more treble. You’ll find a big crosshead screwdriver fits in there nicely. I’m surprised you feel they are dull though, maybe first be sure the tweeters are working. I don’t think the pot was ever intended as a user control, just a fine-adjustment at the factory, but with a speaker this old who knows what has happened in its history.
Tony L
Administrator
I think so, but I can’t quite remember. You’ll hear it though. I’d start by finding the mid-point of the pot’s range as that tends to be fairly close to the factory setting. Listen very closely to voices and instruments in that upper mid-band. The JR149 crosses around 3kHz, so the aim of the level setting is to get this area as seamless, smooth and natural. You will get more treble if it is currently set incorrectly, but really it is there to set the balance accurately between the two drivers. That is the area to focus on. Female vocal, sax, violin, trumpet etc.
PS Also remember exactly where it is set, mark it with a pen if need be, that makes it easy to reverse-out.
Do you know if the crossover has been recapped? Before I recapped min they sounded a bit dull/veiled but after the recap they really opened up and the dull sound went away. The treble afterwards was very clear and nothing like it was before.
No, crossover is not recapped, but I will do that soon.
Here it is with attenuator in original position on both. Despite very good advices from Tony I can't figure out how this thing works.
I moved it left and right but I don't hear any difference.
It is almost all the way in counterclockwise direction although.
I just hope that after recapping the crossover treble will be better.
Here it is with attenuator in original position on both. Despite very good advices from Tony I can't figure out how this thing works.
I moved it left and right but I don't hear any difference.
It is almost all the way in counterclockwise direction although.
I just hope that after recapping the crossover treble will be better.
Tony L
Administrator
Yes, absolutely. I flipped my 149s upside down and did them by ear and with the help of a measurement mic and REW.
Sadly there is no guarantee your drivers are working to spec. Mine weren’t even close, I couldn’t get a solid central stereo image out of them and they sounded different when panning a mono signal left to right with them sitting next to one another. Nothing much to be done other than replace the drivers in this scenario, hence my pair being fitted with new Falcon T27s and B110s. Hopefully you’ll have better luck.
ToTo Man
the band not the dog
A measurement mic would make it easier for us to remotely diagnose the issue, but in absence of this I'd recommend doing the following steps, one by one, and stopping when the problem is solved.
1) install fresh fuses (or bypass the fuses all together).
2) clean the variable resistors.
3) replace capacitors.
4) replace T27 with brand new Falcon F27.
5) replace B110 with brand new Falcon FB110.
6) if the speakers still sound dull after all this, then JR149 probably isn't the speaker for you.
