I replaced the B110s in my IMFs with FB110s.. wow.. do drivers get worse with age?

canuckaudiog

canuckaudiog

On a quest for high fidelity
tl;dr version: Replacing the original B110s in my IMF Professional Monitors with new Falcon FB110s resulted in a dramatic improvement. So much so, I am now going to be recommending and replacing *all* B110s I run across in these speakers if possible. However, I think it's wise to replace only the mids, and other drivers if you can afford it, since mids cover the majority of what you hear. This has led me to believe that other vintage speakers are potentially suffering from similar issues, and likely there are a lot of vintage speakers out there that are no longer performing to their original specs, even after you refoam the drivers and replace the capacitors. Does this mean you should stop buying vintage speakers - no, many still sound great - but it is something to keep in mind since some speakers can have the drivers restored (such as Altecs, JBLs) and it can have a significant impact on how close to their original performance they can realize.

I acquired a pair of IMF Professional Monitors about a month or so ago. One thing I have always wanted to explore with these speakers is replacing the drivers with the newly made Falcon Acoustics drivers (the FB110 and FB139) because of a comment Jerry Bloomfield (the owner of Falcon Acoustics) made about KEF B110s. He had found that every pair he measured were out of spec, even a NOS pair. This would suggest that these drivers suffer from age-related issues, and also means that like replacing capacitors, to bring a speaker back to its former glory, these drivers should also be replaced.

Thankfully, because Jerry Bloomfield is such a gem and has made it possible to reproduce the B110 to exacting specs, this is now something that can be done with speakers that use this driver. In addition, the T27 and B139 have also been reproduced under the same conditions. There are a great number of speakers that use these drivers, so though it is expensive, it's something worth considering since it is available.

About two weeks ago my wife and I were sitting down for coffee and discussing future plans, and the topic of the IMFs came up. I had suggested that as far as restoring them goes, a worthwhile investment is to replace the B110s with Falcon FB110s. We were deciding whether to buy a new amplifier (to replace an A/V receiver we were using as a stopgap) or if we should invest in a better phono amplifier, or something else. I felt the drivers would bring about the greatest improvement. Also, for those wondering, my wife takes an interest in the stereo because the IMFs are hers - she was the one who originally suggested we buy them (it's part of why I married her ;-) ). We spend many evenings together playing cards and spinning vinyl on her IMFs so improving their quality and longevity is an interest for both of us.

Anyhow, I ordered the FB110s a couple of weeks ago and they arrived this past Friday. I wasted no time at all and installed them right away. To begin with, I installed one driver and compared it against the original B110. I always do this with these kinds of restorations because it's important to know if there is actually a difference or not, and if so, is it an improvement? I played a mono signal through the speakers and listened to one against the other. The difference between them was so great, that I had to double check my wiring to see if I had futzed something up. After confirming the wiring was correct, it left me with the conclusion that the new FB110 is far better. It sounded much lighter, clearer, and more natural than the original. I cannot understate the improvement here - the difference was astonishing.

Once I had confirmed the new FB110 was better, I went ahead and installed the second one. My wife and I spent the good part of that evening going through our music collection and listening to music, as if it were anew. We were both taken back by how much better the IMFs now sound. Everything I have read about the B110, how it is a vocal star, how it conveys midrange information so naturally, became apparent and true. A murkiness that resided in the midrange is completely gone now, and left is this beautiful, bell-like clarity with beautiful tone and character. In the 7 years of doing this I have never heard IMFs nor the B110 sound like this. The clarity in the midrange and overall sound depth has been taken up several notches. I still cannot believe what I am hearing!

This has left me with some conclusions, some that have changed my way of thinking around vintage speakers.

1. Drivers do age. I don't know exactly what it is, but my guess is it is the suspension that becomes hard with time and constricts the movement of the driver, lowering its overall sensitivity and frequency response. This is akin to replacing the ferro fluid in a Kef T33. Perhaps the magnet loses sensitivity over the years (ala Altec AlNiCo). Obviously as every driver has a different design and uses different materials, this varies from driver to driver.
2. The KEF B110 is a driver that suffers from age-related issues, and does benefit from being replaced with the Falcon FB110. Mine were from 1972, making them 47 years old, and I imagine the older they are, the greater the benefit realized. How old they need to be to be far enough out of spec to warrant replacing is not something I know of, but based on Jerry's comments, it would seem the majority of B110s (the SP1003 variety) out there are now old enough to warrant replacement.
3. Should every single driver (bass, mids, tweeters etc) be replaced? I don't think so. The midrange driver covers the majority of what you hear, so replacing the other drivers would result in less of an improvement. The bass driver would likely be the next contender (which I am looking into as I write this), but since it only covers a small portion of the frequency range, will not realize as great a benefit. In the case of my IMFs, the B139 is the next driver to look at, and the FB139 is much more expensive than the FB110 so there is that to consider. Tweeters I still have yet to explore, but I imagine there are similar issues there - perhaps to a lesser extent since a tweeter's movement is much finer.
4. Should this change how you buy vintage speakers? I think vintage speakers are still wonderful. But, it has made me rethink about what speakers I buy, because if the ability to restore the drivers is available, that is more attractive because those speakers will sound better with refreshed drivers. It means a 100% restoration is possible, whereas if you cannot refresh the drivers (either by replacing with new ones of the exact same type or are very very similar, or reconing), you may only realize 80% of their former sonic performance (just an example, not a hard number). For me this is important because I am into vintage speakers partially as a historian - I want to experience what they were like so many years ago.

I think a lot of us go through this hobby thinking that drivers do not get worse with age, and this experience has shown me that it's quite possible that is not true. At least, in this specific example it is not true. However, because drivers are not so different from one another in certain aspects, this is likely something that translates to many other speakers so I felt it worthwhile to discuss.

All right, that was a severely long post and if you made it this far, I appreciate your time. Do you have any experience with replacing drivers with new ones, or aging drivers? I'd like to hear your thoughts and experiences.
 
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Thanks for your post. This is good info.

From what I have read, the B110s were always difficult to manufacture to spec, and even new ones had unusually wide variations in performance. Falcon went to great lengths to reproduce them correctly. Let's hope they stay that way, and last longer than the originals.
 
sqlsavior said:
Thanks for your post. This is good info.

From what I have read, the B110s were always difficult to manufacture to spec, and even new ones had unusually wide variations in performance. Falcon went to great lengths to reproduce them correctly. Let's hope they stay that way, and last longer than the originals.
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I did ask Jerry what the production plans for the B110 were, and he said there were no plans to stop it anytime soon. On the contrary, they are trying to keep up with demand. Not a surprise at all! Yes, certainly the lengths they went to paid off - the results are fantastic.
 
Wow, great news on the Facon replacements! I have a pair of LS3/5A clones that have B110s that I purchased over 40 years ago. I will be looking at replacing them with the Falcon driver. I also have a larger pair of speakers I designed that have B139s - may have to replace those too.
 
While butyl surrounds don't show age/stiffening as obviously as foam surrounds, drying up/crosslinking/whatever is common in polymers/rubber/whatever. With foam, you can see the problem, but usually not so with butyl or whatever - though I've seen more than a few that have cracked all around, so complete failure is a possibility.
I've also wondered about the damping applied to bextrene cones. It appears to be somewhat hydroscopic because it does get milky looking, and in some cases, it detaches from the cone. Neither can be good for how the speakers sound.
 
Thanks for the info! You can replace rubber surrounds on older B110s, if necessary. I've bought and replaced a few before with UK-sourced surrounds found on Ebay. I'm sure those Falcon drivers are great.
 
Aren't there some sub-versions of B110? I bought T27's from Falcon for my Kef 101's and remember noticing their B110's are suitable for ls3/5a's but not the Reference 101.
 
The information about how the new Falcon B110s compare with old ones is all nice and dandy, but man, sharing the hobby with your wife? That's the killer story.

Ageing of the bextrene, coated speakers is of course an issue, regardless of how the surrounds look. Normally, on a typical mid-woofer, the surround is not providing any stiffness to the diaphragm. It is there to mount the cone and terminate the waves generated at the point where the voice coil meets the cone. The spider is many times stiffer than the surround and practically the main source of stiffness. But I have only seen one case of butyl surrounds deteriorate, and that was only with B200 SP1039 drivers (KEF 104 drivers). They don't rot, but tend to stretch and become flatter, losing the half circle profile. Perhaps that doesn't affect performance at low levels but it does show to mechanically restrict linear excursion, so not a good thing for real performance.

Spiders obviously age and with older KEF speakers, I have only seen one (B300) become less loose than the average. There was practically no control in cone movement. In most cases, what develops is a stiffer surround. In one extreme example, it had a serious impact in sensitivity. I did not measure Fs and Cms but your post makes me want to do that test. I have almost a dozen B110 and I will eventually try them out.

Specifically for the KEF Bextrene cones, since they were treated with a coating of material similar to PVA glue (but not PVA glue), that coating will deteriorate with time, depending on the conditions. Certainly moisture will play a role and if they take in moisture, they will show increased mass. If that starts to lose adhesion to the cone, it will additionally worsen damping and probably generate a few high frequency secondary emissions.

As a side note, I am interested in the Falcon B139 version. It is based on later version design and gives better power handling. That has to be useful as the original SP1044 was a bit wanting in the power handling capacity.
 
schnitzle said:
Aren't there some sub-versions of B110? I bought T27's from Falcon for my Kef 101's and remember noticing their B110's are suitable for ls3/5a's but not the Reference 101.
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There are several variants for the B110 midrange. For KEF naming, B110 simply means "bass" unit, 110mm diameter.
The original version was A6362. There was also a 24Ohm variant, A6542. These were used in the 60s.
The first "modern" B110 was the SP1003 and was used in many models, including the early BBC monitor, but it was selected units from production. The typical B110 SP1003 was out of spec for that use.
The second iteration was the SP1057, and that was used in the Reference 101, Reference 105, and more.
There was also an SP1083, that was OEM for Meridian, SP1186 (special version for the KM1), SP1190 (special build for the Reference 104), SP1209 (4 Ohm version for the Reference 107 and 107/2), the SP1228 (used in BBC LS3/5a) SP1234 (used in C15) and SP1274 (Reference 104/2)
 
SaSi said:
The information about how the new Falcon B110s compare with old ones is all nice and dandy, but man, sharing the hobby with your wife? That's the killer story.

Ageing of the bextrene, coated speakers is of course an issue, regardless of how the surrounds look. Normally, on a typical mid-woofer, the surround is not providing any stiffness to the diaphragm. It is there to mount the cone and terminate the waves generated at the point where the voice coil meets the cone. The spider is many times stiffer than the surround and practically the main source of stiffness. But I have only seen one case of butyl surrounds deteriorate, and that was only with B200 SP1039 drivers (KEF 104 drivers). They don't rot, but tend to stretch and become flatter, losing the half circle profile. Perhaps that doesn't affect performance at low levels but it does show to mechanically restrict linear excursion, so not a good thing for real performance.

Spiders obviously age and with older KEF speakers, I have only seen one (B300) become less loose than the average. There was practically no control in cone movement. In most cases, what develops is a stiffer surround. In one extreme example, it had a serious impact in sensitivity. I did not measure Fs and Cms but your post makes me want to do that test. I have almost a dozen B110 and I will eventually try them out.

Specifically for the KEF Bextrene cones, since they were treated with a coating of material similar to PVA glue (but not PVA glue), that coating will deteriorate with time, depending on the conditions. Certainly moisture will play a role and if they take in moisture, they will show increased mass. If that starts to lose adhesion to the cone, it will additionally worsen damping and probably generate a few high frequency secondary emissions.

As a side note, I am interested in the Falcon B139 version. It is based on later version design and gives better power handling. That has to be useful as the original SP1044 was a bit wanting in the power handling capacity.
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SaSi! It's great to hear from you, and great to see you are still around. You are a fountain of knowledge when it comes to KEF! I still remember your thread on the 105s you rescued from a store way back when. Do you still have those?

Thank you for that information. That's very interesting! The surrounds on my old B110s look perfectly OK, so I didn't think that was an issue and figured it must be something else causing them to sound off. Sounds like it is a combination of factors when it comes to the B110 - making the FB110 that much more important. Yes please, do test the B110s you have, I'd be very interested to know how they measure up now. I am thinking about putting in one of the old B110s and getting some frequency response measurements to see the difference there. If I do that I'll post the results here.

The B139 is certainly very interesting, and the fact they achieved higher power handling makes them appealing. Unfortunately my IMFs have the 6171 variety in them, so it is not a direct swap, but after talking to Jerry, I want to investigate this more. You wouldn't happen to have any knowledge here, would you? That is, swapping the 6171 for the SP1044? My understanding is the frames are different shapes. I'm hoping to find a busted B139 just so I can try to figure out what I need to do before spending the money on the FB139s.
 
I still have these R105s. But they are tasked for secondary tasks in the living room. I recreated a pair of R107s, having only the mid-hi domes and crossovers as well as the KUBE. Used 4 B200 SP1014 that measured excellent as replacements and my version of the 107 sound terrific. So good, I had no real urge to build any new speakers for almost 5 years now.

I will do the free air resonance test first and see what that gives me. I suspect that any ones with a serious deviation in Fs will also have other issues.
 
Getting back to the original question I do sincerely believe after decades of playing with vintage speaker drivers that all drivers do suffer some degradation with age from very minor in some to extreme failure of others depending on the driver's original design and construction materials and how they have been stored. Drivers exposed to temperature extremes and extremes of humidity will age and deteriorate the most quickly.

Surrounds: With replacement foam surrounds so readily available these days those vintage drivers with foam surrounds are likely the easiest to get back close to original spec as long as the spiders are still good and retain their original flexibility, the magnet retains its original force, and no ferro-fluid is involved in the voice coil gap. Butyl rubber surrounds tend to stiffen over time and finally crack and then disintegrate. I've found treated cloth accordion surrounds to be especially problematic depending upon the brand and driver as they can become rock hard and then crumble. Half roll treated cloth surrounds on vintage Foster/Fostex drivers also become stiff and crispy over time, even on new old stock units properly stored. The drivers with paper accordion surrounds that are an extension of the cone usually crack in the surround area over time due to the constant flexing movement and age related deterioration of the paper.

Personal Note: I recently purchased an orphan Pioneer CS-51 speaker from the late 1960's to play with the PE-12 driver used as a woofer in that model. The inverted treated cloth half roll surround is a thin cloth material with a thin flexible chemical treatment coating and it is still as supple as the day the driver was made, which is quite amazing and especially from a Japanese manufacturer in that era. The only drawback of this surround is that it is so thin and so pliable it lacks the centering force a surround should exhibit to properly damp cone movements.

Cone Materials: Thicker paper cones that are not exposed to temperature and humidity extremes seem to be very durable, while really thin paper cones (common in less expensive US made drivers in the 1950's and early 60's) become crispy and then crack and crumble. Metal cones should last forever if they are made from aluminum, but they are not common as metal can exhibit serious resonance problems if not properly designed.. Polymer cones run the gamut from seemingly indestructible to cones that disintegrate over time no matter how well you treat them based upon the design and construction material used (the dome midrange drivers of some 1980's Infinity Kappa series models being an extreme example of self-destructiveness). Likely the most durable cones ever made are the kevlar cones used in some B&W models over the years.

Magnets: Alnico magnets are well known to often lose magnetic field force over time and especially if they have been subject to hard impacts (I've found re-chargable batteries to lose charge with sharp impacts as well) or strong external magnetic fields. When Great Plains Audio was offering alnico magnetic revitalization for vintage Altec Drivers that was a valuable and unique service but such services are rare. Ceramic magnets seem to hold their field strength quite well if made of the proper quality materials but their field strength levels vary greatly for each type of individual driver. The strongest ceramic magnets for their size I've encountered personally were Jensen Syntox 6 magnets on a 5" woofer from an early 60's X-10 model extension speaker. I've had many vintage Japanese drivers where the ceramic magnets were so weak they wouldn't even hold a steel screwdriver securely to their side and all of these weak magnet drivers sounded like crap. Neodymium magnets aren't found in older drivers, so I have no idea how they would age.

Spiders: I've never had any personal experience with older vintage drivers with phenolic spiders, so I can't comment on those. For typical cloth spiders I've experienced the full range from those that have become stiff as a board and others that became really loose and floppy (The 12" woofer from a BIC Formula 6 curbside find had the floppiest spider I've ever encountered) but most seem to be somewhere near their original compliance if not abused and stored well in controlled environments. Its a good thing that most vintage drivers still have usable spiders as having to replace them would cost far more than what most of those drivers are worth. Spider condition can indeed affect the sound quality of vintage drivers but is not something most people take into consideration.

Final Conclusion: Based upon driver design, construction materials used, past usage patterns, and the temperature and humidity extremes the driver's have been subjected to over their lifespan, vintage speaker systems can sound really close to original specs in some cases to sounding drastically degraded with most falling somewhere along that continuum. The continuing popularity of 60's and 70's iconic speakers such as KLH Model 6's, Rectilinear 3's , Dynaco A-25's, and the Original Large Advent is very much due to their ability to maintain their sound quality over decades if the woofer surrounds are properly maintained while most other mass market speakers of that era have fallen by the wayside.
 
@stickman Wow, what an informative post. Thank you for chiming in and providing your experience and details. As I go about discovering vintage speakers and learning more about restoring them, this has started to become the forefront of my thinking.. the drivers themselves. As I mentioned in the first post, I tend to think that drivers don't get worse with age and basically stay the same. But it seems that being able to differentiate drivers based on the material they are made of and learn more about their inner construction is actually a pretty useful skill to have, because then you would have a good idea of whether or not something like that is going to stand up to the test of time.

This is fantastic stuff, and exactly the kind of thing I was hoping to hear about. Thank you again for your time and thoughts.
 
Almost nothing remains intact with the passage of time in the construction of a speaker unit. (Well, perhaps cast steel or aluminum baskets can be considered not to exhibit wear that has an impact on performance).
If we combine a loss in magnetic power in the magnet with an increased stiffness in the spider, then the unit will become less sensitive having smaller BL and lower Cms. Other parameters will be affected.
It is conceivable that the alteration of parameters is such that the critical values remain consistent with the behavior of the speaker but showing a lower efficiency and lower overall SPL. It is also equally possible that the behavior becomes so different that the overall alignment of the driver goes way out of spec. That can only be determined with measurements of the 30-40 years old driver and comparing these with the specifications of the new drivers (for those of the drivers that such information is readily available). For the rest, we can measure several drivers and examine the spread of the values; if it is a wide spread, it shows that the parameters are going off spec.

However, in practice, for 40 years old loudspeakers, I have found that the main source of discrepancies emanates from capacitors getting old, losing value and showing an increased ESR. Replacing these capacitors, restores a very good level of performance.
 
Stickman's observations are in agreement with my experience and thoughts. A useful summation.
 
SaSi said:
There are several variants for the B110 midrange. For KEF naming, B110 simply means "bass" unit, 110mm diameter.

The first "modern" B110 was the SP1003 and was used in many models, including the early BBC monitor, but it was selected units from production. The typical B110 SP1003 was out of spec for that use.
Click to expand...

I have a NOS SP1003 sitting on the shelf. I got it with a pair of Chartwell LS3/5As.
 
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