ADS L400 crossover capacitor

[Coleman4130]

Hello,

I am refurbishing a nice little pair of L400's.  I'm pretty new to this so thought Id ask your opinion before proceeding.  I ordered Dayton 5% 25uf 250v caps to replace the original 25uf 65v caps and they are giant!  Is this ok or do I need a different product?

On a side not I am new to the forum but have enjoyed many of the speakers talked about here.  A regret selling a pair of L730...

Thanks, -John

 

[owlsplace]

John,

You are fine if you can get it into the space. I probably would have used Carli 150v caps from Madisound.

Roger

 

[Coleman4130]

Thank you Roger, for the low price of these caps I will consider your recommendation.  And with a speaker this small I am worried about losing precious internal cabinet size for bass response! LOL. 

[ra.ra]

Hi John, and welcome to this forum. I love the tiny ADS speakers - - I have a pair of metal bookshelf 300's that were given to me by a former staffer from the Wilmington factory. They are built like tanks.

In fact, I own two pairs of ADS speakers - - both from the early or mid 80's - - but have never felt the need to recap anything. Of course, like yourself, I've been tempted to replace the electrolytic cap simply because I've jumped on the bandwagon and gotten all caught up in the re-cap frenzy. One reason I decided not to re-cap is to avoid what you've run into - - the difficulty of finding an "upgrade" cap which will suitably fit the circuit board. As Roger has noted, a 150V cap will tend to be a bit smaller than a 250V cap, but Carli does not offer a 25uF cap, and even if they did, it would still dwarf the original 63V cap and be a challenge to install.

The second reason I decided not to replace the cap is because this cap is not in the signal path and therefore, not so crucial. Look at C1 in the schematic, which along with R1, runs parallel to the woofer. Compare this with C2 which runs in series with the tweeter. C2 is the most important cap relative to performance, and ADS is known for using very high quality film caps for their excellent tweeters.

The third reason, in my case, is that my speakers have always sounded just fine "as-is" and so I wisely chose to comply with the old adage, "If it ain't broke, don't fix it."

  

[ra.ra]

BTW, John, which type of 400's do you have?

[owlsplace]

Good points, Robert.

You would have to piggyback two Carli's for 25mfd.

I think I would make the swap on one speaker then compare it to the other -- simple enough to put the old cap back in or just lift one leg.

I did this recently with some AR's originally equipped with electrolytics and was amazed how much cleaner the recapped speaker sounded.

My ADS L-980's will be getting the same treatment.

Roger

[ra.ra]

Yes, the suggestion to modify only one speaker for comparison to the original is always a good idea, but it is unclear what the OP is trying to accomplish with a re-cap in the first place. I have this exact same cap type (except 18uF) in a pair of ADS 570/2 performing the very same function, and there is no apparent need whatsoever for any crossover revisions with my pair, which is why I leave it all alone. I just can't imagine myself making any sonic improvements with this replacement on the woofer circuit.

I like the Carli caps very much since they seem to offer very good price-performance value, are smaller in physical dimension than 250V caps, and Roy's measurements seem to suggest that their ESR more closely approximates that of the original NPE caps. Still, paralleling two Carlis - - a 10uF (20x31mm) and a 15uF (23x31 mm) will present a bundle wider in girth but half as long as the Dayton (30x61 mm), presenting its own challenges to install and costing a bit more than the Dayton.

If it was indeed desirable to replace this 25uF cap (part of Zobel circuit), I'd have no problem using an electrolytic cap: it is not that critical; it is inexpensive; and it will fit. Using Erse caps (about 12x25 mm), you could do both speakers for just over a buck total. If a more exotic cap was desired, I'd probably think about trying to piggyback a 10 and 15uF Mundorf E-cap (100V RAW version, 10x30 mm each) for about $3.50 per cabinet. In my opinion, this is not an instance where a large, high voltage, expensive film cap is going to pay off with notable bang-for-buck performance.  

http://www.partsconnexion.com/capacitor_ele_mundorf_bipol.html  

[owlsplace]

All good points, but personally I don't like old electrolytics so I'm predisposed to using film caps. If cost/size was my main concern I would still want to replace any electrolytic over twenty years old. It is simple enough to do a sound test one speaker at a time to see if it is worth the effort at any rate.

Here a shelf life rating of ten years is used for aluminum electrolytics: http://www.wa4bpj.com/Ham_Radio/Ham_Radio_Tech_Info/capacitor.htm

Roger

 

[Coleman4130]

Great conversation and recommendations, I am learning a lot.  I will proceed with an A/B comparison.  

The project started when upon receiving these I instantly snapped the cheap spring connector trying to install speaker cable.  Then while removing the woofer I noticed its rubber surround is half unattached.  And so it goes though I do look forward to hearing these sometime soon.

Thank you again.  This is a great resource.

Next up, KLH Six's and Dynaco A25's.

 

[ra.ra]

So it sounds like you have a couple other issues that require attention. Yeah, I've never liked spring clip wire terminals either, and they might be the only compromised component in this series of speaker models. Take a look at the other woofer to inspect all of the rubber surrounds to ensure full adhesion elsewhere. 

Looking inside the cabinet, I'm curious how that corner edge was constructed that results in the quarter-round shape.