Rogers LS 3/5A restoration: questions

Hi, on the back sticker is written 15 ohm, and 6 ohm on the B 110, these speakers are 15 ohm version, speakers posts look good but made of brass, a Cardas full copper will have make a much better contact and will have improved the sound greatly.Really nice find, And listen your the boss, best regards Yvan

Sorry Yvan, that is incorrect, here are the facts from a prior post of mine when Satch found the speakers:

Satch, congratulations on your score, its one most of us can only dream of. Hopefully, they are still working. As you may surmise, the black covering isn't correct, they are actually walnut or teak cabinets as evidenced by the chips on the front, and the color of the wood inside the area holding the grille, plus black paint drips on the back panel. There's the oddity of orange paint on the backs which suggest there's yet another bit of paint from some oddball previous owner.

However, the fact that you have matching serial numbers with AB matched is really nice as they are a matched pair. I will advise that these Rogers speakers are what the LS3/5a community calls "Psuedo-15 ohm". This is because in 1987, the LS3/5a's were redesigned by the BBC and KEF to use a newer and more consistent KEF B110 (the "C" model with spec number SP1228) and a new crossover using a resistive ladder and ferrite core inductors instead of the previous radio core inductors and autotransformer. This new design was still called the LS3/5a (many feel it should have been the LS3/5B). However, Rogers had not used up all their 15 ohm labels and continue to use them until their supply was exhausted and then moved over to correctly labeling them 11 ohm.

The 11 ohm and Psuedo 15 use the woofer which is smooth and shiny cone with a thinner and flatter PVC surround compared to the rounder and thicker looking Neoprene surround of the original and venerable 15 ohm's KEF B110 SP1003 woofer. The redesign brought the LS3/5a back into the middle of its spec range and many feel it sounds very good, with less nasality of older 15 ohm units that have slowly drifted out of spec due to aging effects on the mid-woofer. Both the 15 and 11 ohm still use the same T27 tweeter with protective grille.

You have some options as to how to consider restoring them, and that probably is a topic for a new thread either in Speakers or in British Audio forum where there are plenty of LS3/5a fans including myself. Hopefully, all the wear is cosmetic and the drivers and crossover are in working condition. If you do start a new thread, link it here so we can follow your progress.

Very similar to my brother finding a pair of LS3/5a's at a garage sale not 4 blocks from our mother's home after lunch. He paid $20 for the pair after remembering what I told him about Rogers and LS3/5a speakers. He's always the lucky one in the family.

By the way Satch, if you need any help with LS3/5a's, my deputy moderator of the Yahoo! LS3/5a Newsgroup lives in Amsterdam.

From memory, the Psuedo-15 ohm units ran from roughly SN 31 or 32000 to around 34000.
 
Hi, yes Mech I saw the thread after I did my post,the B110 version is only 6 ohm?

The B110C SP1228 is a nominal 6 ohm unit. It is the crossover and its components and configuration which gives the speaker system its final impedance characteristics as seen by the amplifier and test gear. The same 8 ohm T27 SP1032 tweeter is used in either version. The original Ls3/5a woofer for the 15 ohm spec. Is an 8 ohm KEF B110/110A SP1003 selected to a BBC specification - only about 10% of KEF's production met that spec. The unusual 18 element crossover with autotransformer accounts for the higher than typical impedance.

Of note, the B110B SP1057 which was used in the KEF 101, and the KEF 105 series has not been used in the LS3/5a, despite misleading Ebay claims to the contrary.
 
Hi, the 1057 have a different surround, Falcon Acoustics with their New B 110 sp1003 is probably the good one when you buy the match ones,to use in the LS3/5 ,15 ohm.
 
Great job. Still dreaming of the day I walk into my local thrift store and find a pair like that, lucky!
Look forward to the finished project and your listening impressions.
 
Still wating for the binding posts and the seals. I decided in the meantime I'd try to clean up the grilles. So first I gently removed the badges, which are glued on (thnx mech986). Next step: not really sure ;)

Rogers.jpg
 
Probably determine if the sprayed on paint is really adhering well or not. A moderately stiff bristle brush might be able to physically brush off the paint without damaging the Tygan plastic weave grille material. Another option might be isopropyl alcohol dabbed or wiped across the grille fabric - but test in inconspicuous spot first. Since grille frames are made from wood, important not to get them wet.
 
Hard to see the difference, but in real life they're cleaner looking. Except two places where some goo (Blue Tack-like stuff) has been pushed in the mesh and I can't get it out. Oh well.

Rogers_20.jpg
 
Nice work, what cleaning method did you use?. That is also some nice test gear there! What do you do professionally and for hobbies?

A thought about the debris - you could try picking it out of the weave with a very sharp pick, or possibly put the grille into a heavy sealable plastic bag and then into the freezer. The goo might contract or become brittle. Upon taking it out Then You could immediately try a focused vacuum implement to suck the debris out.

Another option might be a concentrated pinpoint spray blast of compressed air from a can and slightly invert for freezing with the liquid air, or high pressure air blast from a compressor source - just be sure it's a dry source or will evaporate at room temp.

You might consider stapling a small synthetic fabric loop at the bottom of the grille to the inner surface. Early LS3/5as had this to aid in removing the grilles. Otherwise a stiff flat plastic card not unlike a credit card is best used to prise the grille loose from the Velcro holding without marking the cabinet lip. It is tempting to use a screwdriver or other such implement, but it can damage or mark the soft wood veneer surface.
 
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Thanks! Audio is just a hobby, although I did work as a (radio) broadcast engineer years ago. A couple of friends are still in that line of work, so every now and then I get to visit (and lend a hand) to a radiostation or recordingstudio. The gear was given to me by a technician who switched to some very nice Neutrik testgear. But the most-used gear is my trusty DMM-meter... ;)
On my blog (Dutch only, sorry!) I try to explain some basics of audio for people who want to get into this hobby, combining my love for audio and my profession (journalist/editor).
 
Very good. I made a slight edit in my last post so you might review it. My deputy moderator of the Yahoo! LS3/5A newsgroup, David Fagan, lives in Amsterdam and is an expert on LS3/5A and British speakers and loves Porsche 914-6 like I do, such a small world. I suspect you'd both have a lot in common.
 
I used a semi-stiff toothbrush and just brushed away, a bit like sanding it. Gonna try a pick to get rid of the debris.
I already know one big difference between David Fagan and me: I don't own a Porsche ;)
 
I used a semi-stiff toothbrush and just brushed away, a bit like sanding it. Gonna try a pick to get rid of the debris.
I already know one big difference between David Fagan and me: I don't own a Porsche ;)

There still plenty of time to fix that!
 
At the risk of you refusing all future help: if I'd have enough money to buy a really nice car instead of the Korean shoppingcart I'm currently driving, I'd probably buy a Mercedes. Sorry!
 
Excellent! How have the cabinets turned out now? Looks like you're in the home stretch of restoration.
 
How have the cabinets turned out now?

Mwah. They do have some small 'dinks' and minor damage. Overall I am pleased with the results, this being my first major loudspeaker restoration project including stripping paint etc. Maybe someone with more woodworking skills could have done a better job though.
Now I have to wait for new seals. The ones Falcon provided looked like they were used, big parts had debris on the sticky side. So I sent them a mail and within the hour they responded, saying they'd send me new seals. That's how service should be! But it does mean I have to wait for a couple more days. But in the meantime I found some new toys at the thrift, so I won't be bored... ;)
 
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