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Loudspeakers (Read 10742 times)
Richard_Carruthers
Ex Member





Loudspeakers
Jun 22nd, 2003, 8:01pm
 
Greetings!

I am not ex-BBC and probably shouldn't be here so please accept my apologies for crashing the party. Nevertheless, I do hope someone may be able to help.  

I am a devotee of vintage Tannoy speakers and for a long time have been trying to obtain information/drawings etc. relating to the BBC LSU/10 speaker which employed such a unit. This is mentioned in the ex-Studio Managers' forum, www.oldsms.co.uk/gear/typeb.php.

If any of you can help me with any information about this in-house design, I shall be most grateful.

With best wishes,

Richard Carruthers.
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mikatherton
Ex Member





Re: Loudspeakers
Reply #1 - Jul 11th, 2003, 11:47am
 
Suggest U contact BBC designs dept. Kingwood warren who should have the bbc technical instruction (TI) for the LS/10.
We had several at BUSH Hse but at 9 cu feet and with little H.F. response these monsters were not for the faint hearted to consider moving or listening for cymbels.
We ended up fitting Lorenz tweeters to improve HF response.
But it still needed two people to move them.
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Louis_Niebur
Ex Member





Re: Loudspeakers
Reply #2 - Jul 15th, 2003, 5:32pm
 
Hello Richard, and all,

(I am an intruder on this site, and probably shouldn't be here either!) I just wanted to expand slightly on what Mike said...

There is a bit on the LSU/10 in Edward Pawley's book, BBC ENGINEERING 1922-1972 from 1972. He says it is based on a Parmeko model, and, like Mike noted, that its response fell off above 7000Hz. The biggest problem with this was that it made it impossible to hear the 10125Hz buzz that sometimes appeared from a 405-line television signal, and would end up in radio and television programmes! By adding the Lorenz tweeter, this was fixed.

The Lorenz tweeter (ok, we're getting pretty nerdy here!) was the LP-65 model, and some advertising I found for it says it is "Clean, Clear, and Crisp up to 16,000 cycles!). It used 2 watts, impedance, 5.5 ohms and was 2 1/2 inches in diameter.

I assume (although I am not an engineer) that you would need the HP-1 Kingdom High Pass Filter to go with the Tweeter, since it enables clean movement between the frequencies of the woofer and tweeter...

Hope this helps!
Louis
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Richard_Carruthers
Ex Member





Re: Loudspeakers
Reply #3 - Jul 16th, 2003, 1:42am
 
Mike, Louis - I thank you both.

The LSU/ . .   series contained a number of drivers since the inception of LSU/1 before the war. The first being a  Wharfedale.

I am curious about the seemingly poor performance of the Tannoy unit as, if this was of the dual-concentric type, the tweeter was within 3dB of "flat" up to 20kHz which would have been more than adequate to catch the 405-line annoyance. It has been suggested that a speaker having greater treble dispersion (that is, greater than that allowed by the horn of the DC principle) was required when initial experiments with stereo broadcasting were begun at around this time (ca.1962).

Tannoy did produce a "full range" driver (i.e. a conventional speaker without the concentric tweeter) and I am wondering if this type, possibly being of inferior top end performance relative to the DC models, might have been incorporated in the LSU/10 and hence giving rise to the need for additional/alternative treble units to be fitted. Does anyone know? Sadly, Mr Shorter, who I think designed the LSU/10, no longer is with us.

Interesting if recondite stuff - I'm grateful to the forum for allowing me the air time.

Richard.
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Gargantuan_Sound
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Re: Loudspeakers
Reply #4 - Aug 6th, 2003, 11:53pm
 
Louis,

you mention about the BBC Engineering manual 1922-1972. Is this a standard available book? Or is it a BBC published training manual?

Also would anyone know where to get the old BBC Engineering Training Manuals from?

Many thanks


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