1950's Parmeko Co-axial 15" BBC speakers - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th March 2006, 05:42 PM   #1
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
Default 1950's Parmeko Co-axial 15" BBC speakers

Hi,
I have recently acquired a pair of Parmeko LSU/10 Broadcast monitors used in the BBC studios in the 1950's and 1960's.
I am looking for any information about them.
They contain a LS-1 15" co-axial driver with an (added by the BBC) Lorenz LPH 65 super tweeter. The co-axial tweeter has a six segment cellular horn. The Lorenz tweeter has a clear poly cone.
There is a space in the cabinets for a tube amplifier.
Any and all help/information would be very much appreciated.
Attached Images
File Type: jpg p1.jpg (63.0 KB, 726 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 05:48 PM   #2
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
front
Attached Images
File Type: jpg lsu10.jpg (23.8 KB, 650 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 06:07 PM   #3
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
My word! How on earth did a pair of those wardrobes make their way across the Atlantic?

The amplifier was an LSM/8 which was a slightly modified Leak TL12 using triode-strapped KT66 to produce about 15W. I've never seen an LSU/10 with those tweeters - the one we had (when I was at BBC Broadcasting House) had a pair of Celestion HF1300 mounted in front of the 15" driver.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 15th March 2006, 06:18 PM   #4
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
EC8010

They made thier way across the pond with the help of a whole lot of money and Virgin Atlantic airways.
In this photo you can see the tweeter clearly.

According to Edward Pawley's book All the LSU/10's were augmented with the Lorenz tweeters when the 405 line television standard was introduced.
Thanks
Tom
Attached Images
File Type: jpg 27frombalcony.jpg (75.8 KB, 613 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 06:32 PM   #5
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
They flew?! Ours definitely had Celestion HF1300 - perhaps a later modification. (By the way, 405 line television predated the LSU10 - the Marconi/EMI 405 line and the Baird system were in use in parallel before WWII.)

Here's something that may be of interest.


Instruction S.8

Cabinet LB/8 (Fig. 1.3)

The cabinet is constructed in the form of a vented enclosure which gives a smoother and wider-range bass response than the box baffles used hitherto. The rear of the cabinet is completely boxed in and an opening or vent in the form of a rectangular hole is provided in the base. This vent opens into a cavity between the base and the floor and is bounded by the plinth which supports the cabinet. The plinth is arranged as three sides of a square and directs sound waves transmitted through the vent outwards from the front of the cabinet. The vent and associated cavity have the nature of an acoustic inductance whilst the air enclosed inside the cabinet behaves as a capacitance and the dimensions are chosen to give resonance at the lowest frequency it is desired to reproduce. Low-frequency sound waves generated at the rear of the loudspeaker diaphragm are transmitted through the vent and, over a limited frequency range, are in phase with the radiation from the front of the loudspeaker. The design is such that the useful range of the loudspeaker is extended downwards by about half an octave.

To prevent high-frequency sound waves being transmitted through the vent the upper half of the cabinet is lined with about 1 inch thick slag wool. This is obtained in pre-formed slabs which are stuck to the sides of the cabinet and are then covered with a layer of carpet loom felt. Such treatment is effective in suppressing high-frequency sound waves but does not sufficiently eliminate low-frequency vertical air-column resonance which occurs at about 120 c/s. This is suppressed by three inch layers of carpet loom felt stretched horizontally across the centre of the cabinet where the standing waves have maximum particle velocity. Very little high-frequency radiation reaches the lower half of the cabinet and the only acoustic treatment necessary is provided by a single layer of carpet loom felt. If a thin layer of absorbing material were attached directly to the walls the absorption would be low because particle velocity is a minimum close to a reflecting surface. For this reason the felt in the lower half of the cabinet is attached to battens to space it about 1 inch from the walls.

The loudspeaker amplifier LSM/8 is situated on a shelf within a small compartment in the lower half of the loudspeaker cabinet and at the right-hand side (viewed from the front) and the gain control is accessible through a hole in the lower right-hand panel. This panel and the rear panel adjacent to the amplifier have windows of expanded metal to provide ventilation and a baffle is fitted to the amplifier chassis to direct hot air out of the amplifier compartment. Before the amplifier can be removed the side and rear panels of the amplifier compartment must be detached. These are each held in place by a number of screws and the amplifier itself is secured to the shelf by four bolts. There is, of course, no need for acoustic treatment of the interior of the amplifier compartment but the outside is lagged with three layers of carpet felt.
Attached Images
File Type: gif lsu10.gif (28.6 KB, 569 views)
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 15th March 2006, 06:34 PM   #6
diyAudio Member
 
tomtt's Avatar
 
Join Date: Aug 2002
Location: kansas city mo, and on occasion, around the world ...
Blog Entries: 15
http://www.german-vintage-loudspeake...hp2_nav_id=109
````````````````````````````````````````````````

could you post a pic of the backs of the drivers?

```````````````````````````````````````````````

http://www.oldsms.co.uk/gear/typeb.php
  Reply With Quote
Old 15th March 2006, 06:43 PM   #7
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
EC8010
Thank you so much for that information. It really helps a lot.

tomtt
Here is the back of the driver. They have been in cloth bags since new.

PS: Thank you very much for the links.
Attached Images
File Type: jpg p4.jpg (65.7 KB, 602 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 06:45 PM   #8
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
spider
Attached Images
File Type: jpg oldspider.jpg (46.3 KB, 516 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 06:46 PM   #9
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
Dividing network.
Attached Images
File Type: jpg xovers.jpg (65.4 KB, 485 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote
Old 15th March 2006, 07:54 PM   #10
tom1356 is offline tom1356  United States
diyAudio Member
 
Join Date: Mar 2002
Location: boston
I forgot to mention these are the speakers used at Abbey Road studios to record The Beatles.
Pretty cool huh?
Attached Images
File Type: jpg coax3.jpg (59.0 KB, 478 views)
__________________
My "cult-like" following is accepting applications.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
70cm tall, 3 way, diy speakers based on 10"/4"/1" japanese ken brown drivers. facundonu Multi-Way 34 9th March 2009 04:59 AM
One vintage Stephens Trusonic 206-AXA 15" co-axial driver (16 ohm) zobsky Swap Meet 1 1st January 2007 08:02 PM
Gauss 3288 12" Co-axial Speakers snoopyma Multi-Way 5 28th November 2004 03:07 PM
Tri-axial Car Speakers for Small Room? r_s_dhar Multi-Way 14 13th November 2002 06:49 AM
Parmeko Oil Filled Transformers Tube (Valve) Power Amp 110V up to 250V mozfet Swap Meet 5 29th October 2002 10:57 AM


New To Site? Need Help?

All times are GMT. The time now is 02:27 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2