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Old 4th Mar 2018, 5:59 am   #21
Radio Wrangler
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Default Re: Mystery massive hi-fi speakers ID required

You have to be careful with the power ratings of transistor amplifiers. Some were clearly rated in the sort of Watts used by the makers of CB radio 'burners'

Roj's 200 watts/channel job was most probably capable of that power only into a lower impedance than his speakers, and then only for a short endurance.

The impedance of transmission line bass speakers is fairly well controlled at the bottom end of the frequency range and you don't get some of the dips exhibited by tuned-port designs (or the notorious Isobariks) So the amplifier really has to do a good voltage swing, and can't fall back on a low load impedance to give an impressive power spec.

Arthur Radford was principally a transformer designer/manufacturer, and a very good one at that. Arthur Bailey added some highly competent electronic design skills to the mix. They dealt in real watts, and the transformers without any cut corners at the design stage to cut manufacturing costs were designed to go as low as his speakers. The results were good.

For those Atkinsons, a 405 would be a better starting point than a 303. You're into territory where big mains transformers and big external heatsinks make a difference. Amplifiers designed by accountants need not apply

David
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Old 4th Mar 2018, 10:57 am   #22
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Default Re: Mystery massive hi-fi speakers ID required

Jealous! A really good find, well done! I'll leave it to others to advise on the amp.
Andy
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Old 4th Mar 2018, 12:13 pm   #23
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Default Re: Mystery massive hi-fi speakers ID required

Well I spent a very pleasant evening listening to all kinds of music on these speakers. I am a great fan of 60s 'lounge music' - Henry Mancini etc. I must say that the plucky little Leak seems to drive the speakers quite happily and the detail in the sound is quite extraordinary. I heard things in familiar recordings I'd not noticed before. I was also struck that on some recordings, vocals seem to materialise quite detached some way away from the speaker, rather than issuing directly from it (if that makes any sense at all). Quite spooky! With the cabinets being so large it's hard to escape the expectation of thundering bass, but as mentioned further up the thread, that's not the case at all and it's all a lot more refined and controlled.

What the future holds for these speakers I've yet to decide. They have arrived at the exact point in time when I was about to begin clearing everything out of the front room for redecoration and realistically they are too darn big to be accommodated long term. If they are of value, as seems to be the case, and I do decide to move them on then I will make a decent donation from any proceeds back to the Sue Ryder Charity from whence they came. On the other hand owning a pair of speakers like these is probably a once in a lifetime opportunity, so there is still some pondering to do. Meanwhile I shall continue to enjoy soaking up the sound!

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Old 4th Mar 2018, 12:26 pm   #24
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Default Re: Mystery massive hi-fi speakers ID required

These are similar in size to the Atkinsons but have a constant cross-sectional area line. 39 years since I built them. Still going strong, only the midrange foam surrounds have been replaced and the B139s get turned upside down every 10 years.

The Peerless K040MRF came along a bit after the B110 and HF1300 drivers and does a very smooth job of bridging the gap between the B139 and the 1 inch dome. K040s are unobtainium too nowadays.

£5 is an unbelievable bargain. You have a pair of speakers for life. Once you get used to them, nothing else will do.

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Old 4th Mar 2018, 12:32 pm   #25
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Default Re: Mystery massive hi-fi speakers ID required

Photo didn't make it.... try again!

If you really will have to get rid of them, don't listen to too much with them, you'll get attached!

David
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Old 4th Mar 2018, 2:02 pm   #26
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Default Re: Mystery massive hi-fi speakers ID required

He's right - there is nothing to compare. My Radfords belonged to a diplomat before I got them - he was posted to India, Africa and assorted other destinations throughout his career. He always took them with him, and brought them back. And you are right about vocals in particular - close you eyes and the singer is right there in front of you. That's what I mean by the speakers 'disappearing' before your very ears!
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Old 4th Mar 2018, 3:29 pm   #27
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Default Re: Mystery massive hi-fi speakers ID required

Quote:
Originally Posted by Colourstar View Post
What the future holds for these speakers I've yet to decide. They have arrived at the exact point in time when I was about to begin clearing everything out of the front room for redecoration and realistically they are too darn big to be accommodated long term.
The timing of many fortunate things in life isn't optimum, and I for one wouldn't look a gift horse in the mouth for the sake of a short-term inconvenience. The equivalent quality on the open market would cost many hundreds. The disappearing act is the mark of a really uncoloured speaker, as is the lack of bass until there's actually some in the programme material.
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Old 6th Mar 2018, 12:58 pm   #28
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Those are incredible speakers, and that is coming from someone who rescued a pair of 100KG Wilson Audio speakers from the tip!

If you sell them, please try and ensure they don't just get broken up for the drivers, there are so many LS3's out there, can't be many of these left.
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Old 6th Mar 2018, 1:53 pm   #29
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I'm seriously impressed at your bargain here, and I bet they sound fab!
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Old 6th Mar 2018, 2:05 pm   #30
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Excellent bargain ! I bet they will sound good nice one .
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Old 6th Mar 2018, 3:45 pm   #31
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I like them in the all over grey finish [2nd photo] Steve. There's a 35' lounge her in Bexhill but even so

I'm wondering how you got them home-flat bed truck and a team from the pub?

Dave W
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Old 8th Apr 2018, 9:05 am   #32
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Default Re: Mystery massive hi-fi speakers ID required

Hi guys, hope you don’t mind me posting, have a set of these speakers, built in 1977, by Roy Irwin, P.atkinson design, believed to have been made for studio recording, dedicated left and right, running them with quad 11 amps and yaquin pre amp,
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Old 6th Jun 2020, 5:45 pm   #33
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Default ID required of large transmission line speaker around 2018.

Hi from Maidenhead, UK.

The speaker is the 'Atkinson monitor', designed by Peter? Atkinson in 1975, I think it was, it appeared in the HiFi News magazine in 1975 as a serious DIY project.

The drive units were, Bass - Kef B139 8ohm; Lower midrange - Kef B110 8ohm; Upper midrange - 2 x Celestine HF 1500 16ohm; Treble - Kef T27 8ohm; Super Treble - Coles 4001 8ohm.

These were magnificent speakers, FR - 18hz to 24khz within +&- 3db, 16hz to 25khz within +&- 6db have been claimed, having built a pair in late '80's, I can confirm the 18hz to 24khz. Oh yes, when finished they weigh a number of hernias!

The bass output was detailed and staggering, as was the mid and treble response, certainly brilliant for large orchestral and opera reproduction.
Sadly Kef no longer make the B139 or B110, the same for the T27.
Though I did read a report - yet to be confirmed, that Fane? Maybe starting manufacture of the Kef drivers for speaker manufacturers and DIY'er's.

Good luck.

Last edited by Station X; 6th Jun 2020 at 9:32 pm. Reason: Threads merged.
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Old 6th Jun 2020, 11:33 pm   #34
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Default Re: ID required of large transmission line speaker around 2018.

Quote:
Originally Posted by Hifiman View Post
Though I did read a report - yet to be confirmed, that Fane? Maybe starting manufacture of the Kef drivers for speaker manufacturers and DIY'er's.
Falcon: https://www.falconacoustics.co.uk/

They do the B110, T27 and more recently the B139. The latter was launched in Munich a few years back, and I happened to be there when Ken Kessler spotted it on the stand. Let's just say he got very, very excited about it!

As the website explains, these new drive units have pedigree, given that their original designer is on board.

https://www.falconacoustics.co.uk/dr...rive-unit.html
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Old 7th Jun 2020, 12:25 am   #35
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Default Re: Mystery massive hi-fi speakers ID required

It says something that these drive units are so respected and so sought after this long after they were introduced.

I've been watching the Falcon B139s and wondering about treating my speakers to a new pair. I've been using those B139s since 1975.

So here we are, two years and change later. Does Colourstar still have the Atkinsons?
Not many people have had such an easy entry to the big transmission line club.

I understand what Ted says about the LS3/5A using selected B110, and that those on sale to joe public have a gap in their statistical spreads as a result, but that won't stop some people offering large amounts of cash for any B110 they come across. Suitable or not, they'll try to build what they think is an LS3/5.

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Old 7th Jun 2020, 11:51 am   #36
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It was a massive problem. Rogers were rejecting around 30% of them, and this apparently got much worse as the weather changed (90% reject rate, apparently!). Unfortunately, they could only assemble the speaker and measure the whole thing before deciding if the woofer was acceptable or not, which is not exactly an efficient way to manufacturer.

It was at this point KEF discovered that the drive units used by the BBC to finalise the LS3/5A were at the end of the tolerance range. With the insight KEF gained during this work into the driver requirements, they were able to pre-select the B110s for Rogers. I'm not sure if similar arrangements were made with the other licensees.

The B110 was very variable throughout its life, and the T27 wasn't perfect either. The 11 ohm redesign addressed many of the problems, and they are the best ones to go for in my opinion. But with depressing predictability, "internet wisdom" says the exact opposite. The most sought-after examples of LS3/5A - on sound quality grounds, ignoring rarity, etc - are the ones that are furthest away from the original spec. Which proves that it's the mystique that sells most of these, not the idea of listening to a neutral monitor speaker. Luckily, the latter is a pull to many, so there is plenty of choice in this area.

I've got measurements of dozens of LS3/5A from different licensees from different eras to back this up (can't share them because of commercial sensitivities. But it does rather show that the whole thing is a bit of a joke. The new LS3/5As available today that I've measured are much close to the original spec than any surviving 15 ohm examples.

There's similar stories around the Celestion HF1300. While it's easy to assume the speaker design hasn't really come a long way since those days, things really have improved in terms of consistency, and that's a big deal for manufacturers today.
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Old 7th Jun 2020, 4:40 pm   #37
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Default Re: Mystery massive hi-fi speakers ID required

An interesting 'inside story' Mark

Do you have any evidence of performance drift with time in monitor speaker drive units? For example I have a couple of B110s dating from around 1974 and I sometimes wonder how they now would compare with more recent versions.

As an extreme example, I guess we're all well familiar with the way that some polymers over time can depolymerise into goo, normally when they're an idler or drive belt. What typically happens to Bextrene or polypropylene I wonder. Does it soften or harden? What happens to the 'magic' damping dope applied to the Bextrene to reduce its inherent 'disposable coffee cup' resonances? Does it harden over time? Similarly, we know that extreme failures can happen to foam surrounds, but what typically happens to a rubber roll surround?

I ask here particularly because the BBC is the most likely place to find evidence of change of speaker characteristics over time. We know that initial acceptance tests used to be rigorously applied to monitor speakers, but is there a process of periodic retesting? If so, is any particular drift in characteristic detectable over the years - and though extreme care taken in matching crossover network design to driver characteristics at the design stage, is some readjustment needed over the life of the speaker?

We're all familiar with changes in electronic components over time, but are we right to assume that speakers are immune from drift in material properties?

Martin
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Old 7th Jun 2020, 5:53 pm   #38
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Pretty much everything I said above is in the public domain - I'm very "boring" like that. As for in-service testing, I'm not aware of any official policies, beyond a recommendation that faulty speakers were returned to Avenue House for repair and checking in preference to being fixed on station. But I joined fairly late, relatively speaking, so others might well know better.

We were discussing polypropylene degrading in this thread: https://www.vintage-radio.net/forum/...d.php?t=166887 - that was a new one on me, as I've always found polyprop diaphragms to be pretty stable with time, even though it's not one of the best plastics in regard to UV exposure in "raw" form. I'm not aware of any measurements that chart or prove any systematic degradation in terms of audio performance, but it is always something to keep in mind for any speaker, naturally. We know that PVC is a bad choice for a surround - that is something I've gently investigated - but rubber is fairly well behaved and neoprene better still.

There are many uncertainties here, but fortunately technical staff seem to be able to work around some really quite extreme loudspeaker behaviour - after all, some of them use PMC speakers!
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Old 7th Jun 2020, 8:29 pm   #39
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I don't know what is supposed to be so extreme about PMC loudspeakers. I have used LB1s very happily for twenty years and more and find them more amenable to this pair of BBC trained ears than the ATCs I have owned. I did however, happily balance a big OB on the custom ATC100s in the TRU van.

As regards driver ageing in general and LS3/5as in particular, my 1978 pair of Chartwells sound pretty much as they ever did, and they have seen some service, believe me. How they would measure is a moot point, but from my point of view any deterioration is negligible.

In my time in the corporation, speakers were generally fixed in the field - on an OB there was little choice, and if the two speakers matched on a mono signal, you were good to go. In the early days of the 5/8, there was some variability in tweeter efficiency, and David Stripp personally adjusted the tweeter tapping on the crossover of each speaker against the reference unit before it was issued. Ideally, I suppose tweeter replacement would involve return to ED for this to be repeated, but in practice the "pair" test sufficed.
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Old 7th Jun 2020, 10:50 pm   #40
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I've measured many of the smaller PMC speakers, including the LB1. They are far from flat - aside from the funny bass, they all have a recessed mid and a lifted up HF. That much is apparent on audition. Painfully so, in the case of the exaggerated HF, although I object to that less than I used to At least they moved away from the metal-dome tweeters - those set my teeth on edge. They still have them in the Radio 1 studios.

Just checking, i don't have any curves on this machine, but might have some on my work laptop - I'll try to remember to look tomorrow, but there are other measurements online that say much the same thing. In short, for the TB2 the midrange is about 4dB down, and the HF is about 8dB up. It's funny - none of my operational colleagues believed me when I described them, and when I bought my measurement setup and presented the facts, they still refused to take any notice. So I probably won't change your mind either. Not that I'm trying...

There's something weird about the crossover region on the two pairs of TB2s that we have - in that they don't produce a narrow mono image, and pressing the phase reverse button doesn't really change much. The (much cheaper) ATC domestic SCM7 image like a 4k TV, and measures basically flat - they're not "nice" sounding speakers, but are an amazing tool providing they have enough power behind them. As you'd expect, hitting the phase reverse button on mono turns your head inside out.

All that said, I can see why people like the PMC sound - it's quite appealing, especially for those with older ears - but they are sold as monitors, and as such, they should surely measure at least roughly like every other monitor out there rather than hi-fi speakers? I especially dislike the way the powered TB2As are marketed as "digitally activated", which is a cunning way of implying they are active speakers. And of course, class D amps are not "digital". Well, in a way they are, because the Flying Mole amps cooked themselves and stopped working after a couple of years! The PMC branded replacements - using decent Hypex modules - lasted slightly longer before suffering the same fate. There just isn't room in the available space for that much heat. We now use them with conventional amplifiers.

Funnily enough, Chartwell are one of the worst performers in my experience. Looking at some curves now (which I'm not allowed to share), the top end is some 4-5dB above where they should be, and in the lower treble/upper mid, they are about 3dB up. Some of the rise will be down to the T27 itself (which they started doing as time went by - the 11 ohm crossover brought down the region above 7kHz to help with this), but it looks like someone has selected the wrong tapping for the tweeter level. I can't claim they all do that, but that trend is frequently observed, and makes me wonder if they weren't measuring them terribly well at the factory - measuring speakers was much more difficult and expensive back then. But then, Chartwell weren't short of cash at the start - they spent a lot setting themselves up to manufacturer their own polypropylene bass drivers, for example, and started selling those LS3/5A kits (there's no way any of those met the original spec unless you were extremely lucky!). All that caused quite a few sleepless nights at Rogers. Well, until they went into receivership and Rogers were able to buy the remains...

But as I hinted earlier, that doesn't stop them being one of the most sought-after of the LS3/5As. I've got a very tatty pair in my workshop, and they're perfectly enjoyable, but for critical listening, my 11 ohm examples are much better. Both pairs measure very close to each other, which isn't something that could be said for all the 15 ohm examples I've seen and measured.

The handful of Goodmans samples I've seen measure quite well for a 15 ohm version. Falcon Acoustics made the crossovers for those, and selected all the very components carefully (there's a tale there that I'm not sure if I'm allowed to share - ask Jerry Bloomfield if you like). Still a bit hot at the top end compared to the 11 ohm versions, but better than most Rogers and Chartwells that I've seen. But of course, while I've measured a fair few, I haven't measured them all by any means. But I know others who have found similar variations. The fact that there's so much inconsistency out there tells you it's hard to know just what you're getting when you buy an old LS3/5A, even if you're lucky enough to find unmolested examples.

Of course, any change that takes place over the years happens far too slowly to be audible - your ears might well change at a similar pace, frankly. Audio memory is notoriously unreliable, and I never trust it. Remember; all these LS3/5As did once meet the spec - now they don't. So they have changed - there can be no doubt about that. If an A-B test was possible to set up, the differences would leap out. The differences between the samples I have at home definitely do. But I still like them
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