KEF 104.2 Lacking Bass

Hey Bane,
Without getting into the debate I will just say that 104/2 is an awesome speaker when restored. I picked up a pair of 104/2 from the original owner about 2 years ago. Luckily they had not been messed with and had been sitting for probably 20 years.

I did the ferro fluid immediately. Then I did the doughnuts . Surrounds were the rubber ones and not replaced. Finally I got Falcon caps installed in the xovers.

Very strong speakers including bass for sure. I would make sure they are properly restored before adding a kube or anything else.

Good luck, these speakers are worth the effort of a quality restoration.

Ciao
 
I'm confused! I went to buy the kit on the Falcon website and they specify ALCAP caps! Also they only have the 5% tolerance caps available. What is the difference between 2% and 5% tolerance caps?? Also does Falcon sell a different set of caps that is not ALCAP?

The link I posted said the 2% are available in limited quantity. You may have to contact them and tell them you want the 2% caps. There will be a cost premium. Alcaps are what KEF used originally. Some of your original Alcaps have been replaced with Dayton Audio caps, a mixture of film and NPEs.. Some of the original Alcaps remain in place.

Capacitors and resistors come with a specified tolerance range, +/- 1%, +/-2%, +/-5%, +/- 10%, +/-20%, etc. So, a 100uF cap with a 2% tolerance will be between 98uF and 102uF. A 100uF 10% cap will vary from 90uF to 110uF. That's when new. Electrolytic caps drift in value over time as dielectric materials beak down. Once they get to be 30 years old, they can be far from original specs, but not necessarily. It depends on the quality of the cap, usage and storage conditions, etc.

The KEF 104/2 is a pretty complex crossover network. I'm pretty sure all the caps were originally specified as +/-2%. New +/-5% caps may be closer to the designed values than your 30 year old 2% caps, or they may not be. I haven't recapped my 104/2s. I've replaced the donuts and the ferrofluid in the tweeters. If I decide to keep the KEFs long term, I'd probably recap them with the 2% kit from Falcon. For now, the crossovers in mine remain stock and they sound pretty good.

I still have no idea what the previous owner of yours peakers was trying to accomplish with his random recapping. If you're not going to bother doing something the right way, just save your money leave them alone. Randomly replacing half your caps doesn't seem like a wise investment of time of funds.
 
The link I posted said the 2% are available in limited quantity. You may have to contact them and tell them you want the 2% caps. There will be a cost premium. Alcaps are what KEF used originally. Some of your original Alcaps have been replaced with Dayton Audio caps, a mixture of film and NPEs.. Some of the original Alcaps remain in place.

Capacitors and resistors come with a specified tolerance range, +/- 1%, +/-2%, +/-5%, +/- 10%, +/-20%, etc. So, a 100uF cap with a 2% tolerance will be between 98uF and 102uF. A 100uF 10% cap will vary from 90uF to 110uF. That's when new. Electrolytic caps drift in value over time as dielectric materials beak down. Once they get to be 30 years old, they can be far from original specs, but not necessarily. It depends on the quality of the cap, usage and storage conditions, etc.

The KEF 104/2 is a pretty complex crossover network. I'm pretty sure all the caps were originally specified as +/-2%. New +/-5% caps may be closer to the designed values than your 30 year old 2% caps, or they may not be. I haven't recapped my 104/2s. I've replaced the donuts and the ferrofluid in the tweeters. If I decide to keep the KEFs long term, I'd probably recap them with the 2% kit from Falcon. For now, the crossovers in mine remain stock and they sound pretty good.

I still have no idea what the previous owner of yours peakers was trying to accomplish with his random recapping. If you're not going to bother doing something the right way, just save your money leave them alone. Randomly replacing half your caps doesn't seem like a wise investment of time of funds.

Got it, thanks. I sent them an email so we'll see what they say. Is it just not worth it to get the 5% caps then? It doesn't seem like that big a difference to me but what do I know.
 
I don't recall if I got the 2% or the 5% caps. I will check and let you know if i can find my receipt.

My 2 cents are:
that either cap set would make you happy . Not really worth the brain damage to figure out why QC on some say values are within 2% variation and on others QC says they are within 5% variation.

Do a good job on each part of the restoration and either cap will impress you.

Enjoy the journey.
 
Got it, thanks. I sent them an email so we'll see what they say. Is it just not worth it to get the 5% caps then? It doesn't seem like that big a difference to me but what do I know.

At this point, the 5% caps will likely be better than the hodge podge mess the PO installed. Do the math. He installed a 33uF 5% cap in a place where the original design called for a 30uF 2%. 33%uF 5% could be nearly 35uF (34.65uF to be exact) and still be within spec. That's over 15% higher than the design target. So yes, 5% is better than 15%. And that's just what I can see in the photo you posted. If he was that careless in his capacitor selection, who knows where else he took liberties with the design.
 
If not previously mentioned, the first thing I'd check is the woofer's polarity to see if it was accidentallly mis-wired.

Wow, wouldn't that be funny if one of the woofers got wired wrong and was firing out of polarity. Wouldn't they cancel each other out? Could I just reach in the bass port and switch the leads on the bottom woofer? Nothing will explode right?
 
Wow, wouldn't that be funny if one of the woofers got wired wrong and was firing out of polarity. Wouldn't they cancel each other out? Could I just reach in the bass port and switch the leads on the bottom woofer? Nothing will explode right?
104.2 crossover diagram
1508911314.jpg
 
Lacking bass would be the woofer doughnuts, an out of phase woofer, or a bad woofer. These KEFs are unique in that one woofer is deliberately wired "out of phase" from the factory. Both the top and bottom woofers fire into that central chamber with the big port in the front. The top woofer cone moves downwards when the bottom one moves up.

As for the crossovers, if you can get them out, and can order the caps from Falcon, I can fix them if you send them to me.

Lee.
 
BTW, Lee did the cap replacement for me on my 104/2 xovers and did a great job!

Once the full restoration was completed a few months back the 104/2 are getting more front line duty that some other (more expensive) speakers. They are really good when restored.

Random question on the lack of bass thing: are the aluminum connecting rods still in place that tie the bass drivers together?
 
Lacking bass would be the woofer doughnuts, an out of phase woofer, or a bad woofer. These KEFs are unique in that one woofer is deliberately wired "out of phase" from the factory. Both the top and bottom woofers fire into that central chamber with the big port in the front. The top woofer cone moves downwards when the bottom one moves up.

As for the crossovers, if you can get them out, and can order the caps from Falcon, I can fix them if you send them to me.

Lee.

Thank you so much for offering. My turntable is having some speed issues as well so I am using that as an excuse to finally get these things re-capped. I figure if I have to take my turntable down to my guy on the south side, I might as well get my KEF's re-capped at the same time. :)

I still want to know, I'm 99% sure I can, but before I do...can I reach in the bass port, switch the wires on the PCB for the low frequency driver (positive to negative and vice versa) and see how it sounds? I'm pretty sure I just shouldn't turn it up too loud right? I don't want to blow my amp.

BTW, Lee did the cap replacement for me on my 104/2 xovers and did a great job!

Once the full restoration was completed a few months back the 104/2 are getting more front line duty that some other (more expensive) speakers. They are really good when restored.

Random question on the lack of bass thing: are the aluminum connecting rods still in place that tie the bass drivers together?

The rods are still there and the doughnuts are fine. I can't wait to hear what these babies can really do!
 
Lacking bass would be the woofer doughnuts, an out of phase woofer, or a bad woofer. These KEFs are unique in that one woofer is deliberately wired "out of phase" from the factory. Both the top and bottom woofers fire into that central chamber with the big port in the front. The top woofer cone moves downwards when the bottom one moves up.

As for the crossovers, if you can get them out, and can order the caps from Falcon, I can fix them if you send them to me.

Lee.

Yes, the 104.2 and 107 were wired to move in together then outwards, think of an accordion. This is what drives the air in and out of the port. Wire them to move in the same direction at the same time and you won't get much out of them. I am sure this has caught more than one DIY repair person out.
 
I still want to know, I'm 99% sure I can, but before I do...can I reach in the bass port, switch the wires on the PCB for the low frequency driver (positive to negative and vice versa) and see how it sounds? I'm pretty sure I just shouldn't turn it up too loud right? I don't want to blow my amp.

Yes, but can someone please answer this for me??

When I looked at the crossover, both the speakers seem to be wired correctly but I might as well switch one if I can just to see what happens.
 
Falcon Acoustics sells complete Alcap recap kits for the KEF 104/2:

https://www.falconacoustics.co.uk/kef-104-2-replacement-capacitor-set-alcap-alcap-100v-5.html

They come in 5% and 2% versions. Given the through hole nature of the PCB, replacing the caps should be an easy DIY project.

I just got a response from Falcon and they only have the 5% caps and have no estimate on when they might be receiving more of the 2% caps. I guess I'll order the 5%. From looking at the schematic it looks like KEF used 10% caps? Correct me if I'm wrong, but then what does the 10% on the description of some of the caps mean?
 
I just got a response from Falcon and they only have the 5% caps and have no estimate on when they might be receiving more of the 2% caps. I guess I'll order the 5%. From looking at the schematic it looks like KEF used 10% caps? Correct me if I'm wrong, but then what does the 10% on the description of some of the caps mean?

Yes, it does look like some of the original caps were +/-10%. It's not surprising to see this in the shunt circuits for the woofer and midrange (C1 and C8). I would have also expected it for the larger 450uF and 600uF woofer caps, but it appears the unlabeled caps may be 5%? What is surprising is that they used 10% caps in the signal path of the tweeter (C13 + C14, two parallel caps that basically make up a 7.5uF cap, followed by C15).

Of course, caps have properties other than capacitance. So, replacing 30-year old electrolytics with new, fresh caps is a good idea.
 
How much testing of the woofers (or anything else) did you do before ordering the new crossover components? Did you ever swap drivers left to right? To your crossovers, did you verify there's something wrong with one?
 
Cap % +/- is not rocket surgery.
Lower tolerance (ex. 2%) will be much closer to the stated value than one rated at 5% and and the 10% rated cap may be even further from the stated value.
It's the variance between the STATED VALUE and the range the cap may actually measure at.
Smaller is better.
You already know that KEF used 5%.
Many vintage speakers used +/- 10% caps.
 
How much testing of the woofers (or anything else) did you do before ordering the new crossover components? Did you ever swap drivers left to right? To your crossovers, did you verify there's something wrong with one?

I am going to take the woofer that I suspect is blown to my guy and have him test it, along with the tweeters to be sure.

As for the crossovers, considering some of the caps are still original and the rest are a hack job I want to replace all of them with a matched set for consistency as well as preventative maintenance. The expense is worth it to me.
 
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