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Spendor BC1 - One side quieter

Conor

Conor

Member
Hi all,

Just picked up a pair of early (2223/2224 Blue Alnico, white surrounds) Spendor BC1s and the right speaker is much lower in volume than the other, in order to get an even sound the balance on my Naim 32-5 is at 9 o'clock (12 o'clock being center) and the volume has to go up higher. I have swapped speakers and cables and re-terminated the wire with new banana plugs but still the same.

I'm wondering if there might be something in the crossover that's dead or dying? I usually don't like messing around with original bits if I don't have to.

Other than the volume difference, I absolutely love how it sounds. The amount of times I've wanted to **** the Naim stuff out the window for sounding edgy and harsh... Spendor to the rescue! (though still sounding a little sibilant with records).

Any tips welcome! Thanks in advance!

Set Up:
Thorens TD160 with Nagaoka MP150
Naim 32-5/HiCap/Nap 140/NACA5
Spendor BC1
 
Tony L said:
Are you certain all three drivers each side are actually working?
Click to expand...

My first thought was the bottom driver was blown and I was very upset, Tony! But no, once the balance is adjusted everything sounds like it should! But I'm guessing something is up if one is half the volume of the other.
 
Sorry if you've done all this already -
Simplest things first.
1: Check the cables are secure in the amp and speakers. Try it. Still the same? .......
2: Swop the cables over from one speaker to the other leaving them untouched at the amp end. Try again, if the same speaker is quiet then it's the speaker, if it moves to the other speaker it's the source, amp or cables.

Make certain the the cables are in the relevant sockets securely at each junction each time you change them and the amp should be turned off each time you swop cables over.

I'm sorry if this seems all too obvious, sometimes the worst symptoms have the easiest explaination.

Good luck on your quest!!

Andy
 
The only thing that can die are the electrolytic capacitors in the crossover drying out if there is any.
Easy to replace and cheap as well.
Nevertheless, some BC1 had a problem in the past where the woofer’s rear portion of the magnet was moved towards the bottom because of screws getting lose and the action of gravity/vibrations.
My local Spendor dealer recommended to turn the woofer 180 degrees every few years to avoid this problem, again very easy to do.
 
Andy Stephenson said:
Sorry if you've done all this already -
I'm sorry if this seems all too obvious, sometimes the worst symptoms have the easiest explaination.
Click to expand...

Thanks Andy, you're totally right - it's often the obvious that's overlooked and it has caught me out many times before! I have checked all the above. Maybe time to bring them to the speaker doctor if we have one here in Dublin.
 
Gervais Cote said:
The only thing that can die are the electrolytic capacitors in the crossover drying out if there is any.
Easy to replace and cheap as well.
Nevertheless, some BC1 had a problem in the past where the woofer’s rear portion of the magnet was moved towards the bottom because of screws getting lose and the action of gravity/vibrations.
My local Spendor dealer recommended to turn the woofer 180 degrees every few years to avoid this problem, again very easy to do.
Click to expand...

Thank you for these tips, bassman! I've had my eyes open for a 160BD since I started thinking about Naim, I'll try one if it ever comes up locally, things are finally starting to sound like they should around here. In my experience that only lasts a few weeks before I start thinking I should have gone down the valve route!
 
Conor said:
Thanks Andy, you're totally right - it's often the obvious that's overlooked and it has caught me out many times before! I have checked all the above. Maybe time to bring them to the speaker doctor if we have one here in Dublin.
Click to expand...
More than likely then you're right and it's something in the crossover.

Anyone who can wield a soldering iron and read and understand a multimeter should be able to track down the faulty component/s.

If one crossover's faulty, presumably because of age, the other could be ready to go the same way. It may be wise to get them both checked at the same time.

It's worth getting the BC1s sorted, you've got a well regarded classic on your hands. If you ever decide to move it on you should easily get your money back and probably make a profit on the deal.

Andy
 
If you have ruled everything else out, i.e. are certain the issue isn’t upstream and that all drivers are working (it can be hard for older folk to tell both tweeters are on, and if the lower one is out it would go a long way to explaining the issue), then try swapping the crossovers between speakers. I don’t know BC1s well enough to know if it is a clip-fit with push-tags, or whether you need to desolder them, but that should definitely establish if it is a crossover issue or a driver issue.
 
Thanks a million, everyone.

The man who owned them (from new - RIP) before me was an electrical engineer (made his own PSUs etc) and there seems to be a bit of modification going on with some silk fabric being glued over the bextrene driver and under the screws on the Coles supertweeter - unless that was a feature from the factory. The quiet one is also labelled "RIGHT" which makes me wonder if it was attenuated or something to fit a strange shaped room.

Here are some photos:
https://ibb.co/qN0VWg8
https://ibb.co/K2MRHKz
https://ibb.co/Z69XgSV
https://ibb.co/QMVfVBB
https://ibb.co/zfnLCKy
https://ibb.co/f9NLwrG
https://ibb.co/rHvxchL
https://ibb.co/JR2ZKmc
 
I had a tweeter not working yesterday with my diy 3-way speakers (forgot to solder the cable to it when messing with crossovers). On side was louder than the other, but I couldn't work out why. Certain tracks had parts of the music that seemed to be dominant on one side, other times it was fine.
 
Conor said:
…and there seems to be a bit of modification going on with some silk fabric being glued over the bextrene driver and under the screws on the Coles supertweeter - unless that was a feature from the factory.
Click to expand...

I have seen the cloth covering on BC1s before now, so that doesn’t ring an alarm bell for me. Others here will have more experience and be better able to assess the crossover for mods etc.

Are you competent with a soldering iron/do you have a multimeter? If so I’d swap the crossovers between speakers and at the same time (i.e. whilst they are disconnected) obtain and document an impedance reading for each driver. That done we should know where the problem is.
 
Tony L said:
I have seen the cloth covering on BC1s before now, so that doesn’t ring an alarm bell for me. Others here will have more experience and be better able to assess the crossover for mods etc.

Are you competent with a soldering iron/do you have a multimeter? If so I’d swap the crossovers between speakers and at the same time (i.e. whilst they are disconnected) obtain and document an impedance reading for each driver. That done we should know where the problem is.
Click to expand...

I built a theremin when I was a teenager but it turned out wonky - since then I've left any kind of soldering to the experts! But that seems like a great plan, thanks for taking the time to help!
 
Remove both grilles, put your ear tight against both mid band drivers, ensure they both work, then try the same with the top tweeter. If they differ in volume you need to check if your crossover has all black Erie E203 caps, they drift badly. Can you enclose a photo of the crossover?
 
Geoffreybombom said:
Remove both grilles, put your ear tight against both mid band drivers, ensure they both work, then try the same with the top tweeter. If they differ in volume you need to check if your crossover has all black Erie E203 caps, they drift badly. Can you enclose a photo of the crossover?
Click to expand...

Perhaps download some test tones to isolate the drivers. Something around 5 to 6khz should tell you if the tweeter is working.
 
Crossovers look standard. The material over the bass drivers is standard. Grille looks strange. They are normally recessed and I can't quite determine if it is original material.

Biggest problem is one that you can do nothing about. The early Blue Alnico bass unit white surrounds lose their shape and flatten out. They still sound good to most ears but measure poorly. Feature of the model.

If the bass unit is the culprit then you will have to keep fingers crossed that you are lucky and score one off the dreaded bay. Spendor stopped repairing them around 20 years ago as the tooling was cream crackered. Good news is that you can sell them on to HK, Korea etc and do well. They adore the early Alnico ones.
 
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