Historically, brake fluid with Bendix or similar here in the USA and assume anywhere there's USA made hydraulic brakes used and at least in England, Castrol.
We have different grades of brake fluid here, DOT 3, 4 & 5.
I would use the one which is safest for old rubber.
Brake fluid is also sold by the brake makers here, the companies that supply the caliper / drum assemblies to car makers.
Ask around, use a good brand.
I would use the one which is safest for old rubber.
Brake fluid is also sold by the brake makers here, the companies that supply the caliper / drum assemblies to car makers.
Ask around, use a good brand.
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3 and 4 is more about temperature in a actual car
But are glycol based. So will soften rubber.
Either be fine likely.
5 is silicon so likely wouldn't soften it much
But are glycol based. So will soften rubber.
Either be fine likely.
5 is silicon so likely wouldn't soften it much
I don't think you can reconcile the two. The SP1014 starts off with a Q of a half and a large surface area giving a VAS of 131 litres. Your maximally flat sealed cabinet (Q=0.707) is therefore 130L (giving an effective 65L), which is miles away from the 20 something of the Chorale. It's a bit of an abberation in the KEF lineup of that era because all the rest of the drivers have alignments of T/S components such that they really are very close to the maximum low frequency that can reasonably (meaning not 120g etc.) be achieved by a driver of that size. Most people didn't get close, and still don't. SB have obviously worked it out - of the present day companies - and SEAS have historically always been good on this aspect, but there aren't many others.
Those small cabinets must have had Qs well over 1 (I get nearly 1.3 for an effective volume of 20L). I guess that starting from a free air resonance of 25Hz, at least the rolloff point stays low in freq so you're getting quite a lot of extension from your box. They did tackle this problem from a couple of angles. One, with the larger magnet and higher power B200s and two, with a more heavily damped surround on what was otherwise a 1014. From memory these got the Qs down to 0.4 or 0.44.
There are so many ways to view this. I'm not sure of the date of the Chorale ('68?) but I'm going to guess there were more valve amps round then, so who knows what Q they actually had? You could also view it as a very flexible driver that worked in cabinets from 25L to 125L and didn't need a midrange. What is actually pretty incredible is how nearly all of them are still around and working. Assuming they haven't been in a workshop or garage they all look the same and, AFAIK, perform much the same. That's really quite amazing 50 years on.
Modeling based on the factory data indictes a very large box, but the TM3, which i am familiar with, the same driver worked well in a smallish sealed box (about 19 litres, Q of 1.4 by sim).
dave
dave
I'd say it's a reasonably valid choice for a driver these days. It has a lower free air resonance than most of what you can buy today at 25Hz and it's reasonably tough (though if you want it to be properly tough then go for the larger magnet and 1.5" coil versions. For something you can pick up at £15 a piece it's fantastic value for money. I have used it on and off since I was 14 or 15 and in the '80s had a speaker company that used it in a £350 speaker.
Personally I wouldn't use it the same way as I did then. Nowadays the x-o frequency would already come down to 2kHz (from 3kHz then) and that might save some of the rising response. You could probably go lower still, or turn it into a 3-way. 3 way is a nice idea with it as I don't honestly think it's a great midrange unit - the KEF 104, which is surprisingly lovely to listen to, notwithstanding. It certainly isn't as good a midrange as the B110 SP1228, having two advantages over it of the damped PVC surround and a polypropylene rather than bextrene cone. In fact I'm of the view that both the Kans and the Isobariks are far better speakers than the Saras, right across the board. So that means that even the B110 SP1003 is better than most B200s - and I wouldn't dream of using a B110A in a modern speaker. But as a bass unit with either a beefy tweeter or a midrange and tweeter, the only thing that lets it down is linear excursion, though you're already quite loud by the time that kicks in. Its limitation is a 12mm VC in a 6mm gap, whereas you can get SEAS and other makes with 37mm VCs that are 16mm or 18mm long in a 6mm gap (giving you twice the 'linear' excursion). If you want a two-way in a more conventional speaker then I would probably go for something from SB Acoustics. I like the look of their 8" ceramics where a 30L cabinet will achieve something in the region of Isobarik territory (ie. around 45Hz) and I have a technique that would take two of them down to about 16Hz, from memory. (I'll have to check that wasn't 19Hz, but it's bloody low.)
If you're budget limited, and especially if you're beginning, the B200 is a valid choice. I struggled with it in the 1980s, with there always being a niggle somewhere or other in the frequency range. But I wouldn't use a 19mm tweeter with it these days and would hand its breakup region over to some other driver - either a large tweeter in a waveguide or a dedicated midrange, probably in paper. Either would end up better than a not-so-well executed project using up to date drivers.
Funnily enough I was thinking of getting a pair off eBay just as a personal challenge to see what I could do with them today. It might be helpful to mention that almost the first thing I'd do is put some felt across the dust cap, copying what Touraj did in the first Roksan speakers, until I could get a decent frequency response above 1k. His is a better idea than the Linn disc across the dust cap, though I suspect even Linn could do better these days, now that we have better measurement systems and none of it is so laborious. (Edit: Nah, I'm gonna change my mind there. If they can get 50Hz charging spikes showing up on the output of their amps, they're sure to f*ck it up.)
Personally I wouldn't use it the same way as I did then. Nowadays the x-o frequency would already come down to 2kHz (from 3kHz then) and that might save some of the rising response. You could probably go lower still, or turn it into a 3-way. 3 way is a nice idea with it as I don't honestly think it's a great midrange unit - the KEF 104, which is surprisingly lovely to listen to, notwithstanding. It certainly isn't as good a midrange as the B110 SP1228, having two advantages over it of the damped PVC surround and a polypropylene rather than bextrene cone. In fact I'm of the view that both the Kans and the Isobariks are far better speakers than the Saras, right across the board. So that means that even the B110 SP1003 is better than most B200s - and I wouldn't dream of using a B110A in a modern speaker. But as a bass unit with either a beefy tweeter or a midrange and tweeter, the only thing that lets it down is linear excursion, though you're already quite loud by the time that kicks in. Its limitation is a 12mm VC in a 6mm gap, whereas you can get SEAS and other makes with 37mm VCs that are 16mm or 18mm long in a 6mm gap (giving you twice the 'linear' excursion). If you want a two-way in a more conventional speaker then I would probably go for something from SB Acoustics. I like the look of their 8" ceramics where a 30L cabinet will achieve something in the region of Isobarik territory (ie. around 45Hz) and I have a technique that would take two of them down to about 16Hz, from memory. (I'll have to check that wasn't 19Hz, but it's bloody low.)
If you're budget limited, and especially if you're beginning, the B200 is a valid choice. I struggled with it in the 1980s, with there always being a niggle somewhere or other in the frequency range. But I wouldn't use a 19mm tweeter with it these days and would hand its breakup region over to some other driver - either a large tweeter in a waveguide or a dedicated midrange, probably in paper. Either would end up better than a not-so-well executed project using up to date drivers.
Funnily enough I was thinking of getting a pair off eBay just as a personal challenge to see what I could do with them today. It might be helpful to mention that almost the first thing I'd do is put some felt across the dust cap, copying what Touraj did in the first Roksan speakers, until I could get a decent frequency response above 1k. His is a better idea than the Linn disc across the dust cap, though I suspect even Linn could do better these days, now that we have better measurement systems and none of it is so laborious. (Edit: Nah, I'm gonna change my mind there. If they can get 50Hz charging spikes showing up on the output of their amps, they're sure to f*ck it up.)
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You know you don't need to Sim that, don't you? It can be done on a pocket calculator. In this instance, much of it can be done in your head as it has nice numbers like Q=0.5 at 25Hz. So as long as you've remembered that 25 x sqrt(2) is 35.35 you are practically there. And for a smaller cabinet your Q=1 is at 50Hz in an effective volume of 33L, which probably turns out to be a box of around 50L.
I liked the TM1 and TM3 in their time. Rather recessed in the mid but I always remember the bass as being impressive in the TM1s. I don't know the TM3 as intimately but it's surprising how little the bass suffered with a B200 in a smaller cabinet. In that respect it's one of the easiest drivers I have ever used. Though that might be because I don't ever start a design with Qs at 1 or above these days.
I picked up an unmolested pair in great condition recently. I really enjoy listening to them. The crossover's never been touched and I wonder if I should buy a replacement set of electrolytics from Falcon to see whether it'll make a difference.
Unlike most people here, I have never found any problem with those Alcap/Elcap electrolytics getting old. Even after as much as almost 40 years on. Certainly the tweeter ones see minimal stress, and they're not really being troubled conducting what power there is above 2kHz or so on the midrange. Maybe there's an argument for the 120uF ones acting at 300Hz or so to have had a tougher life. If they have then that should show up in the value. Falcon don't half charge for them as well. If you've got an LCR meter and can match the values closely, it might be worth doing but, if not, you might only be taking matched components and replacing them with unmatched ones (if it's a Reference Series). Incidentally, I can probably test a few to see how much they have drifted over the past 20 years as I measure them all as the bags are opened. I'll be very surprised if any of them have drifted more than 1% but I haven't done this for a while so don't absolutely know.
I think it depends a bit in what context we look at it.
If I am correct, Seas, Dynaudio and Scan Speak (Peerless) already had similar woofers at that point.
Although it's a little hard to exactly track down all dates, mostly because in all history books, you find just information about their tweeters and not so much about their woofers.
Although around mid 70s, it seems that Seas already had demodulation rings in their speakers as well as Dynamic Damping.
KEF speakers are very standard (even today), which gives the impression that Seas should perform better.
Source: https://www.cfuttrup.com/history/seas.html
What's even more difficult, is to find objective data about these woofers.
To make it EVEN more complicated, is that back than the vision of how to design a loudspeaker cabinet was very different.
So in most cases, brands didn't have a complete line up to pick and choose from like we have today.
Practically this means it's very hard to compare apples with apples.
Nowadays these old KEF speakers don't hold up very well, except for nostalgia purposes.
Their capabilities and distortion levels are on par with your super average woofer.
other sources:
https://www.cfuttrup.com/history/scan-speak.html
https://www.cfuttrup.com/history/dynaudio.html
https://audioxpress.com/files/attachment/2683
Compared to other brands, it's really hard to compare as well.
I do have some more experience and feeling with Philips.
But again, comparing apples to apples is really tricky.
Interesting info, thanks (yes they are from the Reference series).
Thank you for this thread. Came across a pair of mint Corellis and the B200s do hold their own really well. The bass is adequate, the cabinet well built. It tends to get muddled when turned up but the staging is impressive for the age and the clarity. Great for listening at a desk/close proximity.
I'll be updating the crossovers with new caps for a before/after comparison hopefully as time permits.
I'll be updating the crossovers with new caps for a before/after comparison hopefully as time permits.
Looking at this some time on from the original post, it seems to me that the way to go is a 2 way with the Scanspeak 10F as the mid-treble unit crossing over somewhere around 400Hz, as in the IMF TLS50. I haven't built my speaker enclosure yet but hoping to get it started soon.
There is some truth in that but the reputation started before the subjectivists came on the scene and it's worth reminding ourselves of why they got a good reputation. Before the '80s almost no one knew how to design a crossover, largely because there was no modeling software, so people either copied the KEF designs and adjusted them a touch for their choice of tweeter - IMF, Cambridge, Nightingale etc. - or just plain lifted them - Ariston/Linn Isobariks, which started with the original T27. Probably half the speakers submitted for review back then will have had gross errors in the x-over and it wouldn't have been hard for reviewers to hear the mistakes. Also, KEF were among the few who had accurate measurement setups, both electrically and acoustically, so could pinpoint the mistakes before they got out the door. Similarly, KEF were the ones who originated the maths for loading the drivers in the correct sized cabinet and not many makers were able to put this into practice optimally (still aren't, in general). People's view of the drivers were lifted by this addition technical expertise. In those days only KEF, SEAS and perhaps Audax could be relied on to give you a driver that got close to the maximum producible for that size at low frequencies - that is until Audax lost the plot with their Aerogel range and then, I think, went bust. Nowadays you can add SB Acoustics to the list of those manufacturers who do optimise their bass drivers' response in cabinet and they actually have some 8" ceramics from which I once worked out that, with an additional technique I came up with about 20 years ago, I could get 2 of them to go down to 16Hz. It was going to take a 150L cabinet each side (divided into two) but, Hell, they were doing better than two B139s which i think would have been 19Hz. (The technique has nothing to do with Isobarik loading which I think is a terrible waste of one driver's output.)
I don't think I'd call the R101 "modest" technically. The 1" T33 is an advance on the T27 on just excursion alone and the 3rd version of the B110, the SP1228, was one of the first polypropylene cones and one of the very few drivers in plastic or Aluminium that didn't have a gross impedance mismatch at the surround - producing that peak and dip around 1k to 1.5k. In the X-O you have KEF's Acoustic Butterworth on the tweeter (probably the single most important advance in crossover design ever (though you don't have to do it the way they do) and Andrew's idea of a 3rd Order rolloff at the bottom end which also lifted the upper bass in a way that partially compensated for the 2pi to 4pi transition (the baffle step). Sure the LS50 driver will be far more accomplished product but you'll have to like an aluminium midrange, which I'm not sure I do, though I've never had that KEF driver in my hands.
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Hi,
Didn't read whole post in details, sorry. I'm b200g sp1075 owner since 1993, when refurbishing Pls check many times what you can use. Don't come anywhere close to those with alcohol... Not for rubber suspension, but coating on bextrene membrane peels off with almost any chemical. Pls be careful.
Otherwise, they sounded great. My friend has linn Isobarik refurbished and it is still big pleasure to listen (even that one has no b200g inside). I remember my system (not in use anymore) b200g +b110 b + t33 in active setup was great. Have no idea how it measured, but good for music playing, that's sure
Didn't read whole post in details, sorry. I'm b200g sp1075 owner since 1993, when refurbishing Pls check many times what you can use. Don't come anywhere close to those with alcohol... Not for rubber suspension, but coating on bextrene membrane peels off with almost any chemical. Pls be careful.
Otherwise, they sounded great. My friend has linn Isobarik refurbished and it is still big pleasure to listen (even that one has no b200g inside). I remember my system (not in use anymore) b200g +b110 b + t33 in active setup was great. Have no idea how it measured, but good for music playing, that's sure
Soon I'll pair my b200g with visaton b80, similar to 10F, think it's gonna be just lovely mid size speaker
In the 50s everyone with a reasonable formal education in acoustics was familiar with speaker radiation patterns, cabinet impedances, crossovers, etc... and how to analyse them using equivalent electrical circuits. This can be seen in acoustic text books from the time (not academic papers but text books!) such as Olson, Beranek, Kinsler & Frey, Morse &,... The idea that technically educated people learnt how to analyse speakers in the 70s is not correct. However, one can make a case for those without a formal technical education starting to perform analyses with the help of design rules such as those from Thiele and Small but most of the large established home audio companies would have employed some engineers with a formal education in acoustics or ones with a formal education in another branch of engineering that had taught themselves from acoustic text books.
The LS3/5A was designed to monitor sound in an outside broadcast van when headphones were undesirable and at levels below those for monitoring music. What we would likely call computer monitor today which weren't really a thing in those days. It is clearly stated in the BBC publications of the time. They are not appropriate for listening to music in a room and if used for this purpose the reproduction quality is well below that of a high fidelity speaker designed for the purpose. They were good quality computer monitors 50 years ago but as one might expect these days there are plenty around with both a better technical performance and a lower equivalent price.
How some home audio products with a modest technical performance became highly valued by nontechnical enthusiasts was via marketing in it's broadest sense. The process is probably easiest to observe with components where there is no difference in technical performance between products that are highly valued and those that are lowly valued by groups of nontechnical enthusiasts. What is perhaps less easy to understand, at least for myself, is what determines which products will become subjectively highly valued and which will not. Then again I have little-to-no knowledge of the technical side of marketing and perhaps to those that do it is straightforward. Interesting subject though.
About the LS3/5A, keep in mind that the very vast majority of people refer to the Roger variant, NOT the BBC variant.
They have a very different frequency response.
If you compare the two. The BBC variant makes sense in the entire context it was designed for.
edit:
see https://www.diyaudio.com/community/...af-g-h1283-tweeter.402669/page-2#post-7440430
They have a very different frequency response.
If you compare the two. The BBC variant makes sense in the entire context it was designed for.
edit:
see https://www.diyaudio.com/community/...af-g-h1283-tweeter.402669/page-2#post-7440430
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