JM Labs Electra 946 lack of high-end detail

I have a large open-plan home theater room that I could not fill with enough sound from my Boston VR-M90 mains. My (5th) sub, an SVS PB2 Plus, was up to the job, but overwhelmed the Bostons. So after reading the critiques in this forum I bought a used pair of Electra 946s. With a single Adcom 5802 they lack all high end detail. Bi-amping them with the Adcom 5802 bottom and 2 channels of an Adcom 5503 (a bright amp) brought out a lot of detail in the speakers, but they still lack the finesse and detail of the Bostons. (I like the Boston sound.) I use an Outlaw 970 pre/pro.

Any suggestions as to how to brighten up these speakers would be appreciated. My beef in partivular is with the single 5" midrange speaker and tweeter, which sound dead.

These speakers are the '80s speakers I couldn't afford back then: big stupid bass, as someone has pointed out, efficient, loud, but not refined.
Are you sure the tweeters are functioning properly? I know, stupid question, but I don't even want to recount the times I've been to audiophiles' houses to audition gear they were selling and discovered they had drivers out and didn't even realize it. As far as I know (haven't heard this particular JM Lab model), this is not a speaker thought to lack treble detail. Certainly no Boston models I've heard, including some VRs, have had the treble detail I've heard in other JM labs models, including lower line Choruses, but this is going back some years.
Congratulations! You are the first to ever find JM Labs lacking in treble detail and refinement.

It could be yours have a problem. Did you get them from a dealer? They should leave the Bostons in the dust. Maybe you aren't used to neutral sound? We are only familiar with what we are used to...

Also, you may not have them setup properly. Do you have any toe-in on them? In general, they need some.

The midrange driver is not 5" but 6.5" and the tweeter is a one inch inverted dome. If you have something different, they your speakers were messed with.

Finally, these speakers didn't exist in the 80s, or even the 90s. They came out in 2001 with the OPC crossover. Are you sure you have Electra 946?
Aball, I think the 80's speakers he is refering to is the Bostons, not the JM Labs.. Focal drivers used in all JM labs I have had are anything but forgiving and low detailed highs or Crisp mids.. Mostly they are normally pretty midrang and Hi's heavy, so something else is going on here in my opinion.. Maybe a speaker Short to a wire inside or you have them Out of phase hooked at the amps, but that would normally make them even more Thin and bright..
Uh, guys, I'm sure the archetypal "80's speakers" Lmhlaw was referring to are neither Bostons nor JM Labs in his mind -- that was just a pejorative description of the sound. And I really don't think someone took out a healthy 6.5" mid and left a skinny little 5" shivering in its place. Every not take things so literally dudes? And yes, lots of bass and no highs does not indicate out of phase hook up...As I said, there is probably something screwy going on with the tweeters, which are more easily damaged. Well, in any case at least we all agree this ain't right...
Thank you all for the instant feedback. The mid-range speaker is indeed 6.5" measured from to the outer edges (beyond the screws). It just looks approximately like a Boston 5" speaker. At any rate, on your suggestions I unscrewed (use metric hex) and pulled it out a bit and to the side to make sure it was working. It was, although it may be blown for all I know. I then examined the 6.5" mid-range in both speakers and noted that the cone was detached from the center concave post "button", i.e., the cone moves back and forth along the center shaft. I've never seen an arrangement like this, but it seems right, since the center convex hard plastic button does not move in and out to the touch.

In sum, unless the mid-range is clearly damaged, I may just replace the tweeters and see if that improves the high end. Any suggestions where to get them? (I understand this is a grossly subjective judgment, but what I mean by high end is a certain bell-like clarity which may be an artifact of the Adcom/Boston combination.)

Lastly, by '80 speaker I had in mind the big Infinitys -- the kind of speaker Cream sounds just right on (as opposed to, say, The Clientele.)
Yeah, the midrange is supposed to work that way. So, you're getting plenty of sound from both tweeters and both midranges if you put your ear up to them? Hard for me to judge what you're hearing wrong then, because I certainly never heard "a bell-like clarity" to the high end of the Boston/Adcom combo back when I used to sell that stuff, but that was 11 years ago now. Anyway, the JM Labs shouldn't sound so deficient, so it seems to me the most likely candidates are either damaged but partially working drivers, or somehow damaged crossovers. Really the only way I can think of that both crossovers would be 'damaged' the same is if somebody deliberately altered them. This doesn't seem very likely either though. Only other easily conceivable option, as has been mentioned, is that your perception of hearing the speakers is what's off. Who/where did you buy these from, and have you recontacted them about this? I think what you may need at this point is a second, in-person opinion from an experienced listener.
You can get exact driver replacement from in new york, if they are still in business.. Also back when I had some Midrange drivers from Focal, I think they were what is called the Polycarbonate type or something, basically had a grey sand like feeling surface, they did not have the greatest quality control for some reason.. I would get a driver here and there when building kits that would actually make a scratching noise when moved by hand in the piston like pumping motion, this was a hung up or slightly out of center voice coil, and I guess it would make them not perform as well as a super smooth piston movement and made them sound like More Restricted..

I ended up getting them replaced and then they sounded better, I would assume having something like that out of whack and supposedly being the Hi quality tolerance FOCAL driver the gap and resistance.. etc in the speaker was off. By the way JM labs are FOCAL drivers, and can be found at other places as well, like ..

Other than that Zaikesman could be correct in the crossover, maybe a out of tolerance resistor or Cap??
Sounds to me like there is a problem with your Electras. My 946s have a very detailed midrange and treble. Infact I have even heard complaints about the Electras being too detailed and bright sounding. I find my 946 Electras to sound neutral although some components and cables can make them sound bright and forward. IMO Bostons are good speakers but not in the same league as JM Lab and Adcom equipment is decent quality but not the last word in high end resolution. Could be you are just used to that particular sound. I am using Threshold power and pre amps with my 946s and have no complaints and have heard various Electra models driven by amps such as Pass Labs, Krell, and Belcanto and all sounded very good. The 946 Electras do have a lot of bass energy though and it could also be that your room needs some tuning as the bass could be overpowering the higher frequencies causing them to sound dull. As someone mentioned it might be a good idea to get someone else to listen to them who is more familiar with the sound of these speakers before you start replacing drivers. In any case if the speakers mechanicaly check out fine and after a bit of room tunig they are still not your cup of tea, you should have no porblem selling them and getting most if not all of your money back and stick with the Bostons.
Lmhlaw - what size is your listening room?
Aball, the "main" line-of-sight area in which the HT/listening area is located is about 75x25' and there are another 1000 or so sq. ft. of rooms with doors branching off this center "nave".

Arnold, I have suspected the Adcoms and the pre/pro too. The Adcoms vary considerably according to model. I have had several, from the 565 monoblocks to the GFA 7000, which sounds the best to my ears but overheats easily even with bookshelf speakers (Bostom VR-M60s). Would I get more bang for the buck buying a different pre/pro first, say a Krell HTS 7.1, or changing the amps? (I currently have an Outlaw 970 pre/pro).

And Zaikesman and Undertow, thanks again for the helpful suggestions.
Well then yes, I think there is a problem with your speakers.