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Rare EMI score

I just picked up a pair of these at a yard sale today for an Andrew Jackson. Cosmetically they need some TLC, they are both in working order too. I hooked them up to my modified RCA RS-177 tube amp and they sound pretty, pretty good.
 
Hello all...yesterday I purchased a pair of EMI 711a s in beautiful physical condition. After some rear switch cleaning, all the drivers are now working..however the woofers have absolutely no bass response...they are working, just all treble...
 
..they are larger then they seemed to be in the ad , built like tanks ..in gonna have to open them up today...I'm hoping for an easy fix..
 
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Fairlane said:
Those are lovely. I would have been all over those too.

Hope you get them sorted.
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Thank you Fairlane...so do i...both of the woofers have the same symptom...I'll post my findings...
...a family purchased a home from an elderly couple, and found these hiding in a nice dry closet.....probably why they are so well preserved...it dwarfs the dls529 next to it...

Thx again..Mike
 
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The surrounds are probably stiff, and as you play them for a while, they may loosen up. If not, it may be time for a brake fluid application.
It also occurs to me that it is worth making sure that there isn't some problem in the wiring, and that one speaker is out of phase with the other. If you just play one speaker, rather than both, is the sound better?
 
Hey Nat..thanks for your input....I did reverse the connection on one speaker with no change...and did tap the inside of the woofer and had a nice healthy thump when I did, and the surrounds do look like new using g a bright flashlight thru the grill. What I did find out , when I isolated the woofer by clipping the wire connection and measured its res, it was 7.1 ohms....a good sign..I think...pictures are as im moving along.. 20210516_120617.jpg20210516_120715.jpg20210516_122637.jpg20210516_122645.jpg20210516_123756.jpg20210516_123925.jpg
 
Further input ..the midrange and tweeters do react to the switching panel correctly , It so seems, and was hoping that loosening and re tightening the screw terminals on the bottom of the crossover box would solve it, alas it did not. I'm going to try this same procedure with the other speaker to see if it will yield a better result....I actually love every minute of this...
 
I decided not to open the second cabinet up just yet, but to take Nat's advice that the woofer surrounds may be stiff, or as I have reqd in previous threads, maybe the cones are sagging? I'm going to turn the cabinets upside down and play them for the week like that and see if anything changes.

I will post any updates ..thanks to all for your valuable input!
 
One other suggestion: try (very gingerly) turning it up. Sometimes the solder joints between the voice coil leads and the tinsel go cold and will work with high power, but inconsistently, and not at low power. They need to be reflowed, which may require the scraping off the the good that is painted on to glue them in place so they don't rattle, and to insulate them. I haven't found a way to do this elegantly, and obviously you need to be careful so you don't carbonize the cone (or if it is in the aluminum foil section, melt it), but it is possible to do, and without looking flat our terrible.
 
Thank you Nat. After work today I did try turning up to power a little...and I really think the volume thru those woofers did get a little louder then the day before, albeit still with no low frequency output...still like a miniature transistor radio of that mid 60s era...but louder. My tech described to me about reforming ancient caps on long dormant tube gear and how he's made it work, and I have as well....patiently....so I'm using that principle here.
If this does not work, could there be a bad crossover cap/res that could block this low frequency response?

These are such nice looking and well built pieces ..I want to hear their full potential no matter the time it takes...cost is another issue of course..

Also, being that both speakers seem to have the exact same issue seems like a real common situation with them....still love them tho.....just another thought
 
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Caps block low frequencies, so they aren't a likely cause of your issues since they aren't usually in the woofer circuit.
I'd look very carefully at both crossovers to make sure all the wires are the same. And even though tightly fastened screw terminals are pretty effectively sealed from corrosion, it might be worth loosening, cleaning and retightening.
Your symptoms are puzzling.
 
I did loosen each terminal on the bottom of the xover box, just as a preliminary attempt, but now I will completely disconnect and clean/reconnect.....
I'm now wondering if the sound emanating from the woofers is actually forced vibration from the other 3 sealed drivers as opposed the being electrical.....the woofer did measure 7.1 ohms when isolated, if the spider wires had a bad or no contact, would I still get a seemingly valid ohm measurement?
 
Something just occurred to me - is it possible the magnets have shifted? If you have continuity and the cone is locked, that is a likely cause - an overheated and distorted voice coil might also do it, but typically it can be moved a bit, albeit crunchily. If the magnet has shifted, there is no motion possible.
It looks like they are glued, not bolted, which complicates things if the magnet gets loose since you can't just use a jig to get the magnetic gap back and then tighten the bolts, you have get the magnet off without damaging the voice coil, clean the old glue off, apply new glue and then get the magnet back on without it mashing your fingers, smashing into the back of the voice coil, or locking the voice coil again, this time while the glue is drying. That magnet has but one ambition in life, and that is to do all those things, so you need a strong jig to center and hold it. There are various threads on how to do this.
 
Your input is thorough, well explained and much appreciated Nat....but I really hope my complete terminal cleansing work my friend...! I will attack it this weekend and will report back...
 
v8caz said:
Your input is thorough, well explained and much appreciated Nat....but I really hope my complete terminal cleansing work my friend...! I will attack it this weekend and will report back...
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I found a pair of 630's which are the bookshelf model from about 1963. The clarity of these is remarkable.
The guitar and Hammond on Incredible Jimmy Smith record is excellent. Then the Sax of Stanly Turrentine sounds like he is in the room.
Hope you solved your mystery.
 
Hello all... great profile pic Champco, I have yet to dive into it. I always tend to load up on projects then have to attend to them a little later down the line. But knowing all this valuable info is here at my fingertips whenever I need it, is very reassuring that eventually all will be well and sounding as it should. I should be opening the EMIs very soon ..

..and btw, that Incredible Jimmy Smith album is exactly that ... incredible...
 
I just put my 711A's back into rotation. I didn't do anything to them after i bought them at a yard sale quite a while back. I did notice if you use them as floor standing speakers they sound better upside down. the little metal plate on the short side on the back should be on the top. I hope you get them sounding up to snuff.... mine sound very pretty pretty good.
 
Hey portnoy...I'm just about ready to officially attack these....I have alot of speaker projects but these are special in my eyes... I will turn them upside down and hope that that solves my problem...they are very stately and have quite a footprint.These were in a closet for many decades and forgotten about supposedly. I will try to make it a near term priority.....we're your speakers lacking in bass response before you turned them around?
 
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