BBC Overview

This section of my website is dedicated to BBC and Rogers loudspeakers. It started life over 20 years ago with just a scan of an old Rogers brochure and my review of the LS7. Since then, it has grown a lot, and has become a fairly comprehensive source of information about BBC-designed loudspeakers. This gradual change in emphasis hasn't yet prompted me to move non-BBC designs from Rogers - such as the LS7 and the dB101 - to a separate section of the website, but that might well happen eventually. In the meantime, this section broadly divides into BBC and Rogers sections.

This page serves as an introduction to BBC loudspeakers, and includes an overview of the models created by the BBC over the years. I don't pretend it is complete or comprehensive, but it is a work in progress and will occasionally be updated in light of new information.

There are several other pages within this section that cover certain speakers in detail. As far as possible, pretty much everything I know about these speakers is contained within this section. I have been researching these speakers for over 20 years now, and even as a "background task", it's still consumed a lot of time and effort. I hope it remains of interest, and perhaps it's even more useful now, given the availability of newly manufactured BBC designs available today.

History of BBC loudspeakers

The BBC's R&D department actively investigated loudspeaker technology for many decades. A full history would be very hard to write, but in short, the first fruits of the BBC's loudspeaker research was the LSU/10, which arrived some time between 1948-1950. Early on it was realised that commercial offerings did not have the quality or - importantly - the consistency required by the corporation, especially as audio quality improved with the introduction of the microgroove LP and FM broadcasting, and that left no option but to design loudspeakers from the ground up.

Initially the BBC used commercially produced drive units, but once they realised that the manufacturing processes used to make paper diaphragms were one of the main reasons for the inconsistencies noted between different samples of the same unit, they started a programme of research into alternative materials for bass/mid duties - leading to the adoption of Bextrene first of all, and later polypropylene. Of course, these findings greatly benefitted the wider loudspeaker industry, and Bextrene was adopted by several manufacturers, as was polypropylene. The former is rarely seen today, but polypropylene is still in widespread use.

Once upon a time, there was a very detailed history on the Harbeth website, but over time this has become a much shorter work that focuses more on the earliest years and is rather critical of some of the later designs (for obvious reasons). The URL changes from time to time, but at the time of writing (March 2021) it can be found here:

https://harbeth.co.uk/harbeth-about-us-harbeth-the-bbc-heritage/

Sadly, the original series of articles was never finished, as far as I know, but what did get published remains an extremely interesting read, and can be found on the Wayback Machine:

https://web.archive.org/web/20140225082326/http://www.harbeth.co.uk/uk/index.php?section=aboutus&page=harbethhistory&pageno=1

While this remains accessible, there seems little point trying to duplicate effort, so I'll focus more on the products here.

BBC ENG INF - Loudspeakers - The BBC collection

This article discusses BBC speakers, past and present, and is a really good starting point. It was written at almost the end of the BBC's involvement with speaker design - only the LS5/12 emerged after this was published.

Please note: The copyright of this article belongs to the BBC, and while I believe that the inclusion here constitutes fair usage given the historical value, please be aware that it may be removed at any time.

Since making those scans, all issues of this in-house publication have been made available on-line at the BBCeng.info site, and there are lots of fascinating articles to be found there. I have gone through them and picked out the issues carrying articles relating to loudspeakers - see below - but as you might imagine, they cover a lot more than just speakers.

Grade 1 and Grade 2 monitors?

We need to get one thing clear: the BBC never had Grade 1 and Grade 2 monitor speakers!

This miconception is something I see all the time - people often call the LS3/5A a Grade 2 monitor, and likewise the LS5/8 is frequently described as Grade 1, and this, unfortunately, has "stuck" in the minds of many. As a result, people have come to believe that the "LS3/" part of the model number means "Grade 2" and "LS5/" means "Grade 1".

In reality, "LS3/" means "for OB use", and "LS5/" means "for studio use". Graham Whitehead confirms this in the ENG INF article above, though spot the unfortunate typo there!

Whatever the intended application, both OB and studio loudspeakers were designed to sound as good as they could be. Remember, BBC engineers were not labouring under the same constraints as their counterparts in the commercial world - they were given the time and budget to develop the best products they could, and of course, they had easy access to studios and performers, and an anechoic chamber - relatively few loudspeaker manufacturers could match this.

I suspect this idea of grading might come about from broadcast video monitors, which very much exist in grades 1, 2 and 3, and the prices definitely reflect the grade! I could say much more - indeed, broadcast video monitors is one of my areas of interests at work - but this would be rather off-topic for this section of the web site. I frequently refer interested folk to EBU Tech 3320

The main differences between OB and studio monitors were physical. OB monitors had to fit into smaller spaces, and they had to be placed rather nearer to the listener than would be the case for a studio monitor - leading to measures such as placing the tweeter in front of the woofer to help with power response and stereo imaging, for example. And for the same reason, the peak sound pressure levels required were often less. But none of that implies that a reduction in quality was acceptable.

So to summarise, the BBC model numbers follow this convention:

  • LS1/ - general use (offices, content monitoring, etc)
  • LS2/ - drive units
  • LS3/ - for OB use
  • LS5/ - for studio use

The number after the slash is simply the number assigned to a design, given out in order. This can cause confusion initially if you are not familiar with this - for example, you can be forgiven for wondering why the large LS5/8 has a lower number than the smaller LS5/9. But the LS5/8 was designed first - it's that simple!

Of course, there are gaps in the sequence - I've never heard of an LS5/10, for example. I don't have the data to explain this, but one can speculate that perhaps designs were started then abandoned? In 20 years of asking the question, I've yet to get an authoritative answer.

Now that we understand where the LS3/ or LS5/ designation comes from, we can anticipate the next response:

But the LS3/5A was most commonly found in studios...

Well yes, that is true - certainly in local radio, for example, where the LS3/5A was the mainstay in their studios and technical areas. And it was found in many more situations across the wider BBC, such as VT edit suites, playout areas, vision gallaries, and a whole host of other areas where the relative lack of bass extension and inability to play at very high levels were not a concern. While this might cause a degree of confusion at first, it's just a sign of the success of the LS3/5A design. No-one was going to say "sorry - you can't install an LS3/5A in this edit suite because it's an OB speaker"! If there had been such rigid thinking, then they would have had to release an identical version of it with a different number, perhaps LS5/7? That would have been crazy, of course!

That said, there were occasional models where something like this happened - for example, the LS3/1 and LS5/1. But while these models had much in common, they were sufficiently different in execution to deserve different model numbers.

The models

I don't pretend this is a complete list by any means, and I'm not going to claim the credit for it, as I've basically taken Graham Whitehead's document above as my starting point! If the model number is a link, then that will take you to my article about it on this website. Further sources of official information are in the right hand column.

General use loudspeakers

As found in non-critical areas, such as offices, etc.

General use loudspeakers
Type Description Links
LS1/1 Powered speaker using an 8" Goodmans drive unit and a valve amplifier AM8/2 that produces 3 watts from a single-ended EL38. BBCeng.info
LS1/2 Powered speaker using a Goodmans woofer and Celestion tweeter. The amplifier is the AM8/4A, which is a push-pull valve amplifier producing 15 watts from a pair of EL34s. BBCeng.info
LS1/8 Powered loudspeaker using a 6" bass driver and a pair of 3" cone tweeters mounted side by side. Solid state amplifier produces 10 watts.
LS1/9 As LS1/8, but with option of DC operation (12-24V via 4 pin XLR) in addition to mains input.
More about the LS1/8

I'm often asked about these as they are very common on the second-hand market. In short, avoid!

Being honest, whilst well-made, these sounded pretty average. And it's rare to find one in original condition that still works properly. The bass driver had a foam surround that rotted away, and most were repaired on-station with whatever drive units engineers could find in the RS or CPC catalogues that physically fitted the hole. I guess there was no point worrying about originality given their non-critical applications. One interesting substitution that I discovered was the Fane Sovereign 6-100, which is a PA driver! The results were much as you might expect...

Of course, if you find one with the original driver, you can have them re-foamed, but I honestly wouldn't bother. When I first heard these - back in the mid '90s when they were mostly still in original working condition - I was really disappointed with what I heard.

These were built by Keith Monks, and to be fair to them, they were presumably just supplying what the BBC specified. But having said that, I did read in an old Keith Monks catalogue that these were a development of one of their existing products - if I find a source online, I'll add a link to it.

I think the drivers were supplied by Goodmans. The cabinet was ported with a very long cardboard tube that is mitred and glued at a right angle to fit inside the box. The enclosure is constructed from thick chipboard with no panel damping; air damping provided by fibreglass or Rockwool insulation held in a cloth bag that is placed loosely inside. Veneers were usually teak, though I have seen the occasional '80s black ash example. The crossover amounted to just a 1uF "tropical fish" film capacitor in series with the two tweeters. The mono audio amplifier was usually based around TDA2030 but there is a version that uses a DIL power amp IC. It is powered by a small torroidal transformer that is worth rescuing for future projects! It accepts line-level audio signals on a PO316 input jack socket and uses a small transformer to convert from balanced to unbalanced. A combined rotary power/volume control and power lamp was mounted on the side. The BBC must have bought thousands of these!

Drive units

Many of these were built in-house; others were bought in - perhaps selected, perhaps not. Some were modified. I've never seen a complete list, so this is compiled from design reports and other documentation. This is very much a "work in progress"!

Drive units
Type Description
LS2/1 BBC-designed 12" Bextrene unit used in the LS5/5.
LS2/1A As LS2/1 but with improved power handling.
LS2/2 BBC-designed 8" Bextrene unit fitted to the LS5/5.
LS2/4 Modified version of the LS2/2, as fitted to the LS3/4.
LS2/5 Celestion HF1300 fitted to the LS3/6 and derivatives.
LS2/8 Audax HD12-9-D25 with protective cover. Used in LS3/7?
LS2/9 12" polypropylene driver fitted to the LS5/8.
LS2/10 Audax HD13D34H tweeter fitted to the LS5/8. Is this the bare unit, missing the protective grille?
LS2/11 12" polypropylene driver fitted to the LS5/8 - equivalent to LS2/9.
LS2/12 Audax HD34 tweeter fitted to the LS5/8 and LS5/9, and the LS3/4C and LS5/11. With additional metal protective grille.
LS2/13 8" Bextrene woofer fitted to the LS3/4C.
LS2/14 BBC-designed 8" polypropylene unit fitted to the LS5/9.
LS2/15 Audax HD34 tweeter fitted to the LS5/8 and LS5/9. With additional metal protective grille. What's the difference between this and the LS2/12? This designation comes from Graham Whitehead's ENG INF article, but I'm wondering if it was a typo? More information required.

OB loudspeakers

Originally designed for OB use, but frequently found in studios and other non-OB applications. As explained above, these are not "Grade 2" monitors!

OB loudspeakers
Type Description Links
LS3/1 Uses a Plessey 15" paper cone woofer and 2 Celestion HF1300 tweeters, mounted on a perforated panel in front of the woofer to allow close-range monitoring. Sealed cabinet. Uses the AM8/1, which is a 15W push-pull amplifier using a pair of EL34s. BBCeng.info
LS3/1A As the LS3/1, but with a Goodmans woofer. BBCeng.info
LS3/1B As the LS3/1A, but with a different crossover. BBCeng.info
LS3/4 Designed for MCRs (mobile control rooms), with an angled cabinet for mounting close to the ceiling. Uses a 8" Bextrene woofer LS2/4 (apparently supplied by Spendor - type BC2/8) and Celestion HF1300 tweeter. Woofers are prone to failure. BBC RD 1969/5
LS3/4B As LS3/4 - haven't yet been able to establish what changed.
LS3/4C Replaces LS3/4 and LS3/4B. Uses an 8" Bextrene woofer (LS2/13) and and Audax HD13D34 34mm dome tweeter (LS2/12).
LS3/5 The original BBC R&D design.
LS3/5A A modification of R&D's LS3/5 by BBC Designs Department, necessary because of changes in the KEF drive units. BBC RD 1976/29
BBCeng.info
LS3/6 A derivative of the Spendor BC1
LS3/7 Large OB speaker, designed to replace the LS3/1. Uses a 12" Bextrene woofer from Spendor and a 1" dome tweeter from Audax (HD12x9D25) that is mounted on a perforated baffle in front of the woofer to allow close-up use. The cabinet is ported. It is an active design based around a modified Quad 303 designated AM8/15. Surviving examples have normally had the tweeter replaced with a random "whatever vaguely fits" replacement, which is sadly not uncommon in the BBC in my experience. However, it appears that equivalent replacements are available from Falcon Acoustics, so anyone owning a pair that have been repaired this way in the past can at least bring them into spec (provided measurements with a calibrated measurement setup are done to set the replacements to the correct level). As I've never knowingly heard a pair with the original tweeters, I can't sensibly comment on the sound quality, other than to say that every example I've heard has been rather bass-heavy - taller stands would probably help. BBCeng.info

Studio loudspeakers

Originally designed for studio use. As explained above, these are not "Grade 1" monitors!

Studio loudspeakers
Type Description Links
LSU/10 Massive studio monitor designed back in the 1940s. I've never seen one of these in the flesh. BBCeng.info
BBC RD 1949/39
LS5/1 The studio version of the LS3/1. Larger cabinets with reflex loading and the two tweeters mounted above the woofer rather than in front. BBCeng.info
LS5/1A As the LS5/1, but with a Goodmans woofer and suitably revised crossover. BBCeng.info
LS5/2 A television version of the LS5/1 that uses a different shaped enclosure that allowed it to be suspended. BBCeng.info
LS5/2A As the LS5/1, but with a Goodmans woofer. BBCeng.info
LS5/4 A version of the LS3/1A for Bush House
LS5/5 A large 3-way loudspeaker incorporating a 12" Bextrene woofer, 8" Bextrene midrange and Celestion HF1400. Cabinet painted grey. BBC RD 1967/57
LS5/5B As LS5/5, but with a Spendor 8" midrange and teak veneer finish
LS5/6 As LS5/5, but different shaped cabinet for suspending. BBC RD 1967/57
LS5/8 The large active design based around a 12" polypropylene bass unit and an Audax HD13D34 tweeter, and a modified Quad 405 that incorporates a low-level crossover that is designated AM8/16. BBC RD 1979/22
LS5/8AL and R As the LS5/8, but with the baffle sloping in at 30 degrees for use in OB vehicles.
LS5/9 A medium-sized model that uses a BBC-designed 8" polypropylene bass unit and the same Audax tweeter as the LS5/8. Sometimes found with the 50 watt AM8/17 bolted to on the back panel. BBC RD 1983/10
LS5/11 A modified LS3/4, intended to sound like an LS5/9. Uses the same drive units as the LS5/9, but the crossover is modified.
LS5/12 The last design from the BBC, using Dynaudio drive units. A relatively compact model, with similar dimensions to the LS3/5A, but somewhat deeper, and with a bass reflex port on the rear panel. The design was by Graham Whitehead, so this is not from BBC R&D. Never commercially manufactured.
LS5/12A Modified version of the LS5/12. Sole manufacturer was Harbeth, and apparently the modifications that turned it into the A version were at Alan Shaw's insistance! I've only seen a very small number of these in the past, and have never had the chance to listen to them, so can't comment on them personally, but by all accounts it was not a terribly successful design. Stereophile reviewed it in 1995.

BBC R&D Design Reports

This is an attempt to list all of the BBC R&D design reports that cover loudspeaker design. Of course, some of these have already been linked to, on this page and elsewhere on this website, but this is intended to be a master list of all relevant R&D reports. These links will download the files from the BBC website, and of course, the copyright belongs to the BBC so you should read the copyright notice before downloading any of them.

BBC R&D reports
Report Description
1938-29 The technical design of O.B. loudspeaker amplifier and baffle
1944-09 Recent investigations into methods of measuring the transient response of loudspeakers
1946-06 Investigations into the use of R.K. loudspeakers for studio balancing with particular reference to the probable future use of wide range loudspeakers
1948-04 The selection of a wide-range loudspeaker for monitoring purposes (First Report)
1949-03 The selection of a wide-range loudspeaker for monitoring purposes (Second Report)
1949-07 A portable 7½W Loudspeaker Amplifier
1949-39 The design of a cabinet for use with monitoring loudspeakers
1952-05 The selection of a wide-range loudspeaker for monitoring purposes (Final Report)
1954-13 The Klein-Plessey Ionophone loudspeaker
1954-28 An automatic integrator for determining the mean spherical response of loudspeakers and microphones
1955-08 The Robbins-Joseph (R-J) loudspeaker enclosure
Monograph 08 (Aug 1956) An Automatic Integrator for Determining the Mean Spherical Response of Loudspeakers and Microphones
1958-31 The development of high-quality monitoring loudspeakers: A review of progress
1963-01 Influence of loudspeaker directivity and orientation on the effective audience area in two-channel stereophonic reproduction
1965-09 The Goodmans 'Maxim' loudspeaker
1966-28 The design of a low-frequency unit for monitoring loudspeakers
1967-57 The design of studio monitoring loudspeakers Types LS5/5 and LS5/6
Monograph 78 (Jan 1969) Aspects of High-quality Monitoring Loudspeakers
1969-05 The design of the LS3/4 loudspeaker
1970-13 Acoustic scaling: General outline
1972-25 Loudspeaker distortion associated with low-frequency signals
1972-34 Acoustic scaling: Instrumentation
1976-29 The design of the miniature monitoring loudspeaker Type LS3/5A
1977-03 Factors in the design of loudspeaker cabinets
1977-37 Improvements to cheap loudspeakers
1979-22 Design of the high-level studio monitoring loudspeaker type LS5/8
1981-12 Piezoelectric plastic transducers - a feasibility study
1983-10 The design of the prototype LS5/9 studio monitoring loudspeaker
1983-13 Optical methods of measuring loudspeaker diaphragm movement
1985-07 Acoustic scaling: the development of improved instrumentation
1986-03 Design of a prototype moving-coil high-frequency loudspeaker drive unit
1988-14 On the design of loudspeakers for broadcast monitoring

There is a lot of material available on there covering all aspects of broadcasting, and of course there's plenty more reading for audio engineers - I had to restrict myself from including much more! The acoustic scaling reports were included because that is the work that led to the LS3/5A, of course. Personally, I think it's amazing that the BBC gone to so much effort scanning and making all this material available for free - I remember that obtaining paper copies of these reports was far from easy back in the 1990s, but now we have all of it available at our fingertips. I only wish I had time to read and absorb it all! If there's anything that I've missed which is related to BBC loudspeaker design, please let me know...

Other BBC ENG INF articles

BBC ENG INF was an in-house publication primarily for engineering staff, that was published quarterly between 1980 and 1993. I have a small handful, and have already scanned one or two articles for this website - I did plan to scan more, but discovered that all of them are available already on the BBCEng.info website:

Here is a list of content related to loudspeaker design:

BBC ENG INFO
Edition Description
No. 4 - Spring 1981 Page 4 - Loudspeaker Developments
Mentions the new LS5/8 and the upcoming LS3/6/Spendor BC1 replacement, the LS5/9.
No. 10 - Autumn 1982 Page 6 - LS5/9 et Al
An introduction to the new LS5/9. Also mentions the LS3/4C and the awarding of licences to Spendor and Goodmans to build the LS3/5A. It goes on to say that Rogers has a licence to build "another BBC designed miniature monitoring loudspeaker the LS3/8A". Intriguing. Or just a typo?
No. 18 - Autumn 1984 Page 2 - Licence Agreements
The awarding of licences to build the LS5/9, to both Rogers and Spendor. I don't think Spendor made many - I've yet to see one.
Page 9 - Loudspeaker Components
This is a another summary of the LS5/9, but goes on to mention the dedicated amplifier (AM8/17, though this type number isn't mentioned in the text) and the mounting hardware developed for the LS5/9.
No. 43 - Winter 1990/1 Page 7 - Loudspeakers - The BBC Collection
Graham Whitehead's article cited above, which forms the basis of much of this page.
No. 51 - Winter 1992/3 Page 4 - New amplifier for the LS5/8
Detailing the AM8/20 - the Chord amplifiers replacing replace the Quad 405-based AM8/16.
No. 52 - Spring 1993 Page 2 - Stop Press...
Brief details of the AM8/21 - a stereo version of the AM8/20.

It's possible I've missed one or two speaker-related articles - if so, please let me know. There's lots more content to discover besides speakers, so be prepared to lose several hours of your life exploring them!