Review: JM Labs Diva Utopia Be Speaker
It's not a lot of work. NOthing at all compared to modding a Ming Da MC-2A3 preamp. Just 2 V-Cap OIMPs and 2 Solen 220uF 250Vs. The Solens are hard to install, creative tie-wrapping required due to size. Once figured out the mod for the pair can be done in 30 minutes or even less. The dead midrange was the $2 SCR lytic cap. This is the biggest difference between Diva and Micro. The Micro doesnt have it, thats why even in stock form the Micro has better midrange. Damn the speakers cost $14k new, how on earth can they get away with using this??? I am not using any premium film cap for that and its already night and day. The blunt highs were because of the 3.3uF Tru-cap. The V-Caps gave it the airiness and decay. Like I said I bought them just because I know somethings wrong with the design and can be fixed easily. The drivers are worldclass and I am a sucker for looks. |
Update: The mid bass dip and strange overtone actually appears courtesy of the series notch filter in the crossover board that connects to the 2 woofers (not the main Xover board where the speaker cables connect to, it's the board that's secured onto the inside of the front baffle. There lies the woofer low pass crossover and right before it gets to the drivers are in series a 440uF cap and an inductor and 3-paralleled-47Ohm resistors which makes the series notch filter which I had originally mis-identified as a Zobel. The series notch filter's purpose in theory was to smoothen and extend bass response, but sadly it does the exact reverse in practice. I removed it by disconnecting 1 lead of the 440uF and the bass comes alive and there is no hint of a mid bass suckout anymore. The Divas now sound a few classes better in dynamics and even transparency. Did Focal put that in for the sake of "spec"manship? Or was it to make these speakers possible to drive with OTLs? (Series notch fixes impedance spikes like Zobel, and calms resonances due to impedance peaks in theory) Even with extensive listening I dont hear a bass hump or a tendency to resonate. I will leave it disconnected until I find a compelling reason to put it back. |
Thanks for the advice Shadorne. Dont feel there's any anomaly at 1k or so right now especially after I pulled the series notch filter. There used be a bass suck out and wooden "middiness" (in addition to low freq muddiness) to these speakers which a friend has always described as nasal but its now gone. After reading up on the purpose of notch filters it seems that it works specifically at calming a resonance peak at a certain frequency which supposedly eliminates a nasal character due to resonance. I have a feeling the Focal came up with the values based on modeling and calculation but did not really check whether the suppression is dead on when everything is on the box along with that tuned port. A destructive cancellation might have turned into a whole can of worms and exacerbated the problem instead. Not touching the filter for the midrange for sure as all sounds fine from the mids to highs eversince the cap swap. |
I dont think its only my specific pair of speakers. When I auditioned the Divas a few years ago at a dealer the "wooden" bass and the nasal sound was all there, and I am sure most owners and ex-owners would agree with me. Funny even the salesguy said in a lot of respects the Electra Be sounds better than the Diva. I say with confidence that the cure is worse than the disease in this case. I would expect woofer ringing to be audible as a high bass low mid hump or nasal sound, but contrary to theory without the notch filter the preexisting nasal character actually went away. |
It's been exactly a year since I've owned the speakers. A fellow audiogoner bravely took the step of following my crossover mods and is quite pleased with the results. Recent communications with him sparked my interest in further pursuing the improvement of the still somewhat lethargic, constricted, and occasionally "one-note" bass as most evident in Holly Cole "I can see clearly now" and Eagles Live "Hotel California." I removed the woofer crossover board and carefully took measurements of the components. It's a 4th order crossover with L1=1.2mH C1=390uF L2=530uH C2=220uF. What disappoints me is the DC impedance of the inductors. 1.1 Ohm and 1.0 Ohm respectively. The 2 woofers are wired in parallel. 6 Ohms nominal per driver that makes it 3 ohms. With the inductors of such high impedance, no wonder the bass is lethargic. Kind of like having to drop 1/3 of the power before getting to the drivers! Better inductors of similar values should be 0.12 Ohms (Check Michael Percy Audio or Partsconnexion) A friend suggested that I do some tspice simulation of the circuit. Ouch, this crossover is extremely notchy and phasey (the phase shift as the frequency increases is not smooth at all.) The woofers are 4th order, the midrange is second order for sure. A rather strange combination. A friend suggested I use tspice and come up with values for just a Butterworth 4th order and run simulation to verify the drop is smooth. I compared the 2 plots and decided to be adventurous. Ordered the parts from Partsconnexion and THEN I realize how much bigger and heavier those inductors are. Even the strap on 68uF Mundorf bipolar lytic is 3 x the size of the incumbent 390uF (I need 460uF for C1). This is a much much more involved mod than the cap replacement of the mid and tweeter obviously. Took me many hours figuring out how to mount them creatively and somewhat non-invasively without having to build it externally. But even with only 1 speaker done I was able to tell the difference putting my ears close to the woofer. There is a world of difference in clarity. Another hour gets the 2nd channel done... drum roll... There is a lot more dynamic contrast in the bass notes. The decay characteristics of one drum beat vs another is clearly evident. It doesn't go any lower than before, but has the "fast bass" (a term used by Avalon's Niel Patel) that never existed with these speakers. Listening to no less than 10 of my favorite bass-challenging recordings I don't hear any note that stands out or causes a nasal sound. I'm not quite done yet. Ultimately I might just build an external crossover box for it so I can replace ALL bipolar lytics in the crossover and see if I can take it up another notch. |
It's a combination of analysing the current components and figuring out what kind of short-cuts the orig. mfr took to minimize cost/size and whether/how they relate to the current shortcoming in the sound first, then validate that in your current listening environment and decide what mods to apply. The approach of replacing a coil with the same inductance with a huge air core foil inductor (which will likely reduce series resistance) will give you improvments but likely not get you the max benefit vs a well thought out mod. But you never know until you try it out. Just be careful not to damage the old components in case you want to revert. |
Hi Jazzao1, The coupling caps for the tweeter is a good start which will get you 70% of the way. Getting the lytic replaced with a Solen AXON 250V 180uF bypassed with a 2uF Mundorf silver oil will get you to 100% of where the mids and highs should be. Both mods take less than 10 minutes per speaker. The woofer crossover mod is very involved. Honestly I would not recommend it unless you have some skilled DIYer with some special drills handy (or build and ext crossover box outright) |
If you don't do the woofer inductor mod then stick with 180uf unless you hear a midbass suckout in that case the subwoofer doesn't cross well in the room and you will need to get the midbass to play lower by using a 220uf. The 440uf lytic, ok to pull one lead out of circuit to disable series notch filter. Do this only if you do not intend to use OTL amps or flea powered amps to drive speakers. Caps: solen 250 and Axon 250 are the same. Anything is better than the stock lytic cap. Heck you can by from parts express the Dayton caps too. |
I am assuming you didnt detect and harhness/brightness immediately after the mod like
llkmi7 observed right? |
