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Offline Simon Briggs  
#1 Posted : 15 February 2014 10:10:26(UTC)
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I have had an interest in these designs since my early Teenage years when I heard a pair of Spendor BC1s

I currently own and use Spendor BCIs BCIIIs and currently have Spendor SA3s in place in the main system.

Any forum members here have any experience with the LS 5/8 and the passive version the PM510?

I may look for a pair of the PM510s or maybe the LS5/8s to simply try them out

BBC Monitor

Edited by user 15 February 2014 10:20:11(UTC)  | Reason: Not specified

Offline kengale  
#2 Posted : 15 February 2014 16:23:58(UTC)
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Originally Posted by: darkmatter Go to Quoted Post
I have had an interest in these designs since my early Teenage years when I heard a pair of Spendor BC1s

I currently own and use Spendor BCIs BCIIIs and currently have Spendor SA3s in place in the main system.

Any forum members here have any experience with the LS 5/8 and the passive version the PM510?

I may look for a pair of the PM510s or maybe the LS5/8s to simply try them out

BBC Monitor


I used to hear them quite regularly at the BBC, but it's a long time ago, and I can't really remember exactly what I thought of them at the time compared with BC1's (like you, I've still got a pair of these, with the super-tweeters). But you do need rather a big room for them.
Offline frank23  
#3 Posted : 15 February 2014 16:35:09(UTC)
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Maybe you'd like these Spendors, specifically made for the WDR, the West Deutsche Rundfunk, or the West German Broadcasting organisation. Check the pics of the rear: http://www.audio-markt.d...m.php?id=1715058314&
Offline Simon Briggs  
#4 Posted : 15 February 2014 18:47:03(UTC)
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Originally Posted by: frank23 Go to Quoted Post
Maybe you'd like these Spendors, specifically made for the WDR, the West Deutsche Rundfunk, or the West German Broadcasting organisation. Check the pics of the rear: http://www.audio-markt.d...m.php?id=1715058314&


Interesting piece of history an 8" based system
Offline Simon Briggs  
#5 Posted : 17 February 2014 23:19:08(UTC)
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Still getting excellent results from my SA3s there is something special about a big two way hence my interest in getting my hands on a pair of LS 5/8s

This is an interesting beast the LS5/1

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Offline ashleym  
#6 Posted : 18 February 2014 00:08:30(UTC)
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I was always interested in behind baffle mounting of bass drivers. I take it this helps with directionality as the frequency goes up? All sorts of, to us, odd tweeters and they still work. Clever.
Offline Simon Briggs  
#7 Posted : 18 February 2014 00:10:51(UTC)
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Originally Posted by: ashleym Go to Quoted Post
I was always interested in behind baffle mounting of bass drivers. I take it this helps with directionality as the frequency goes up? All sorts of, to us, odd tweeters and they still work. Clever.


Yes helps with this with these big two way systems
Offline Simon Briggs  
#8 Posted : 18 February 2014 00:11:13(UTC)
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Offline Martin Colloms  
#9 Posted : 18 February 2014 10:36:21(UTC)
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Good BBC LS5/1 examples were very good

the problem was the lack of consistency for the Goodmans 12inch paper cones which were never intended for repeatable 2-way use up at this crossover point.

Thus the new project aim was consistency, plus improvement if you could get it.
On balance I preferred the 5/1 to the 5/8 but heard a good dem of an active 5/8 once

Always had a soft spot for the SA3 active, Spencer Hughes on top form

MartinC
Offline Simon Briggs  
#10 Posted : 18 February 2014 12:23:52(UTC)
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Originally Posted by: Martin Colloms Go to Quoted Post


Good BBC LS5/1 examples were very good

the problem was the lack of consistency for the Goodmans 12inch paper cones which were never intended for repeatable 2-way use up at this crossover point.

Thus the new project aim was consistency, plus improvement if you could get it.
On balance I preferred the 5/1 to the 5/8 but heard a good dem of an active 5/8 once

Always had a soft spot for the SA3 active, Spencer Hughes on top form

MartinC


Martin,

I reckon an 'approximation' but not a new version of the LS 5/1 could be made using this driver or even this?

Datasheets and response curves NB the 15" is quite smooth better than many so called hifi drivers, both will need slots to achieve improved diffraction and dispersion.

15"

18"

Edited by user 30 October 2015 12:28:14(UTC)  | Reason: Not specified

Offline Martin Colloms  
#11 Posted : 18 February 2014 14:23:18(UTC)
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the response curves are only on axis , you really need the off axis set to judge them

BTW the 'slot' barely worked and the cavity formed added some coloration

For the LS5/1 the two HF1300 were run in parallel to try and get some more power handling when operated so low in the frequency range, I recall 1.7kHz ?

Those little 19mm paper voice coils weren't up to much , 2W RMS if you were lucky , but with a steep crossover at 3.3k they would take 100W rated on unclipped uncompressed programme
Offline Simon Briggs  
#12 Posted : 18 February 2014 14:31:04(UTC)
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Originally Posted by: Martin Colloms Go to Quoted Post
the response curves are only on axis , you really need the off axis set to judge them

BTW the 'slot' barely worked and the cavity formed added some coloration

For the LS5/1 the two HF1300 were run in parallel to try and get some more power handling when operated so low in the frequency range, I recall 1.7kHz ?

Those little 19mm paper voice coils weren't up to much , 2W RMS if you were lucky , but with a steep crossover at 3.3k they would take 100W rated on unclipped uncompressed programme


Much as I suspected with the slot but will research further and determine the effects of such. I am going to contact PD to see if they have carried out some off axis measurement. Interestingly I have four of the high power Audax 34mm domes which can take the lower crossover frequency anticipated, likely if I did this that would roll one of them off above 5 K or so


Offline Simon Briggs  
#13 Posted : 18 February 2014 14:39:23(UTC)
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Questions asked to see if I can have sight of the off axis family indeed I am very interesting to see what they are like off axis

Edited by user 18 February 2014 15:05:56(UTC)  | Reason: Not specified

Offline kengale  
#14 Posted : 18 February 2014 19:20:29(UTC)
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Originally Posted by: ashleym Go to Quoted Post
I was always interested in behind baffle mounting of bass drivers. I take it this helps with directionality as the frequency goes up? All sorts of, to us, odd tweeters and they still work. Clever.


The slot in front of the speaker in this application is such a small change from the speaker's own diameter that you can pretty well ignore the effect on the speaker's directionality. Usually you'd aim at a slot with width roughly half the speaker's diameter, with the general view to widening the dispersion at right-angles to the slot over the top octave of its useful range.

But in general bass speakers of the day were rear mounted because they relied on trapping the cone surround edge between the speaker basket and the baffle, and had gaskets to aid in this. It's only later that bonding techniques developed so that you could rely on them not coming unstuck from the front of the basket.

Offline ashleym  
#15 Posted : 18 February 2014 20:39:54(UTC)
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Thanks all for the slot info.
Offline Simon Briggs  
#16 Posted : 18 February 2014 23:33:21(UTC)
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Going right back in time to the LSU/10 the LSU/12 and the LS3/1

http://www.highfidelityr...bbc-studio-monitors.html

UserPostedImage

Report with mention of the LSU/12A and LS3/1

http://downloads.bbc.co....pubs/reports/1958-31.pdf

Offline Simon Briggs  
#17 Posted : 19 February 2014 17:29:47(UTC)
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Originally Posted by: Martin Colloms Go to Quoted Post


Good BBC LS5/1 examples were very good

the problem was the lack of consistency for the Goodmans 12inch paper cones which were never intended for repeatable 2-way use up at this crossover point.

Thus the new project aim was consistency, plus improvement if you could get it.
On balance I preferred the 5/1 to the 5/8 but heard a good dem of an active 5/8 once

Always had a soft spot for the SA3 active, Spencer Hughes on top form

MartinC


Been searching for an SA3ex the SA3 actives but still cannot find a pair!!
Offline Simon Briggs  
#18 Posted : 20 February 2014 00:37:37(UTC)
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This link has some nice BBC speaker history & info

http://www.markhennessy.co.uk/rogers/bbc_txt.htm
Offline darkmatter  
#19 Posted : 30 October 2015 12:22:27(UTC)
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As an aside I recently located a fine example of the KEF LS5/1AE BBC Monitoring system.

I wuill be setting them up before the Carltons in my main system. Bless my Wife our "Bedroom" system will be running a pair on BCIIIs on the end of a Krell S550i and Orelle SA100 Integrated amps :)

I will report on the LS5/1AE system once they are set up

Simon BigGrin

Originally Posted by: darkmatter Go to Quoted Post
Still getting excellent results from my SA3s there is something special about a big two way hence my interest in getting my hands on a pair of LS 5/8s

This is an interesting beast the LS5/1

UserPostedImage


Offline mat  
#20 Posted : 30 October 2015 18:46:14(UTC)
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The occulsions should help a bit even though they are only slightly narrower than the woofer, they act as secondary point sources which have a wider dispersion pattern than a plane piston or for that matter a cabinet edge.


I've taken accurate polar measurements, and have seen BEM data which shows this effect clearly. These guys new what they wanted to achieve.


Mat.
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