DLK ULM Speakers

onanysunday

chasing realism
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I just picked these up for $20 at a thrift store. Possibly the most rare DLK speaker (mfg.'78-'79) moreso than the DLK Model 3 or 4 from what I gathered on the web. I've been looking for a pair of these type of mini bookshelf vintage speakers (any other recommendations?) that sit on top of your towers ever since I purchased a pair of Rectilinear Micro-3 bookshelves. I was so impressed with the Micro and what they contributed to the overall sound enhancement of my completely upgraded Genesis Physics III, that I've been on the lookout for another similar set for the floorstanders in my other sound setup. Obviously, I couldn't just pass these up, they're too interesting..

There were meant to sit on top the DLK Model 3 or 4. Apparently, you were supposed to dial back your tweeter pot on your floorstander and use this speaker as a high-frequency replacement. From what I've heard so far, that sounds about right. Before you get too carried away, I am saddened to report there is something a bit "off" with the sound of these speakers, just like the KEF C75 pair I just purchased. The ULM's sound pretty clear on the treble, but also seem to be missing alot (and I mean alot) of sound information and have very low volume overall with a teeny tiny soundstage. So..what do you think, does this mean they are blown, or could a recap revive them (as that is what I had planned on doing when I purchased them but don't want to waste the time if it's not going to properly rejuvenate them. I can check resistance of the windings to have a comparative assessment between comparable sets of drivers. But it does seem like something is wrong with them that I may not be able to diagnose. These little speakers are in wonderful shape and grilles look perfect. Part of one wood base is cracked all the way across and the glue on a couple little wooden braces has broken loose. Otherwise, they are in great shape.

On the back photo, you can see a little gap beneath the speaker grille and base of the speaker. This is where you route your speaker wire to connect to terminals within the cabinet. Simple crossover, I only see a 4.7uf 50V and a 2.2uf 200V bi-polar cap in each for re-capping. There is very little info on these from the web, which is also part of the reason I am posting. Does anyone have experience with these or what may be wrong with the sound of mine? Thank you.

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Those aren't electrostatic. Electrostatic speakers don't use magnets.

While recapping is a good bet, before you start, I'd check each driver separately with a multimeter and make sure they all read the same, as you suggested. You could also try connecting each tweeter directly to your amp (at very low volume, of course) and make sure they all play OK. Since they're connected in series, one bad tweeter would affect the entire speaker.

If they all check out OK, then I'd do the recapping. At the same time, I'd replace those awful spring connections with decent binding posts.
 
I comparatively tested the resistance both speakers, let's call them "A" and "B".


"A" = all three drivers test out equally at 2.6 ohms, while the electrolytic situated on top of the middle driver was 2.6 ohms. The larger cap was OPEN

"B" = all three drivers test out equally at 2.5 ohms, while the electrolytic situated on top of the middle driver was 2.6 ohms. The larger cap was OPEN


Interesting, one matched set of drivers tested out at 2.5 while the other 2.6 ohms. Would this most likely be due to the degraded, inline capacitor values or the voice coils of the drivers themselves? I am happy with this result as it gives me the illusion of hope that if I recap them with HQ metallized poly's all will be right with the world once more..

Looks like it's recap time.
 
A .1 ohm difference isn't relevant enough to change anything audibly.

I've heard several models of DLKs and while some are more to my liking than others, none of them were poor performers by any stretch.

Yes, recap and relisten and keep us posted, I'd expect you might be surprised how these sounds with fresh caps.
 
The resistance on the drivers are consistent which is good, however 2.5 ohm speakers is an extremely low resistance, isn't it?
 
They're in series, so a total of close to 8 Ω. Also, you shouldn't be measuring capacitors with an ohmmeter, you won't get any meaningful results. Replacing them should be cheap enough, I'd just go ahead and do it.
 
They're in series, so a total of close to 8 Ω. Also, you shouldn't be measuring capacitors with an ohmmeter, you won't get any meaningful results. Replacing them should be cheap enough, I'd just go ahead and do it.

Yes. Thanks for the clarification on all this, it's helpful. I only checked resistance on the caps because it was the only test I could think of to get a reading that could be used for a side-by-side comparison. I don't have a capacitance test on my digital multimeter to get a proper reading, although the open resistance value I obtained on the larger caps should be indicative of an open (failed) capacitor, unless I am not reading that correctly?

I am still hoping that all these speakers need are some fresh caps. For the time being, I do have one leftover Dayton 2.2 UF 250V cap that I can put in to see how it sounds. I am excited to get these back up and running again as I have a hunch they may offer nice, supplementary high frequency sound to my Quartets and enhance the overall soundstage.
 
FYI, there were several versions of ULM's the early version(rarest) were Electrostatics, intended to sit atop the 3's and 4's
 
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