Tweeters to replace electrostatic speakers - UK Vintage Radio Repair and Restoration Discussion Forum

telstar · 4th Feb 2007, 10:42 am

Hi. I have managed to obtain some suitable tweeters to replace my side mounting electrostatic speakers, which were missing on my Grundig valve radio. I obtained these slim line tweeters from Maplin in Leeds. These are not piezo types, so an audio coupling capacitor is required to couple the tweeter to the main speaker. The part number for the tweeter is L64AW, and the coupling capacitor required for each tweeter is 1uF, part number KR78.
Thought that this info may be of help to someone with the same problem as myself. I have not tried them out yet, as Maplin have ordered the coupling caps for me (not in stock at the branch).
I also need a tweeter and a cap for my Bush VHF72.
Regards
Mike

quantum · 4th Feb 2007, 3:35 pm

If your output is 3-4 ohms you might find that 1uf is a bit small, most sets or grams I've come across have 2-4uf caps to link the tweeter with a 3 ohm output. You might also be disappointed with the amount of treble that is 'tweeted' anyway, as it is possible that a set designed for electrostatic tweeters might not have an output transformer designed for good high frequency response.

One alternative I've seen (although I've not tried it myself) is to use the insert from a crystal microphone in the place of the electostatic speaker, and make sure that the cap which links it from the anode of the output valve to the HT has a high voltage rating as the HT would destroy the crystal.

4th Feb 2007, 10:42 am	#1
telstar Octode Join Date: Dec 2003 Location: Leeds, West Yorkshire, UK. Posts: 1,592	Tweeters to replace electrostatic speakers Hi. I have managed to obtain some suitable tweeters to replace my side mounting electrostatic speakers, which were missing on my Grundig valve radio. I obtained these slim line tweeters from Maplin in Leeds. These are not piezo types, so an audio coupling capacitor is required to couple the tweeter to the main speaker. The part number for the tweeter is L64AW, and the coupling capacitor required for each tweeter is 1uF, part number KR78. Thought that this info may be of help to someone with the same problem as myself. I have not tried them out yet, as Maplin have ordered the coupling caps for me (not in stock at the branch). I also need a tweeter and a cap for my Bush VHF72. Regards Mike

4th Feb 2007, 3:35 pm	#2
quantum Retired Dormant Member Join Date: Mar 2003 Location: Birmingham, West Midlands, UK. Posts: 785	Re: Tweeters to replace electrostatic speakers If your output is 3-4 ohms you might find that 1uf is a bit small, most sets or grams I've come across have 2-4uf caps to link the tweeter with a 3 ohm output. You might also be disappointed with the amount of treble that is 'tweeted' anyway, as it is possible that a set designed for electrostatic tweeters might not have an output transformer designed for good high frequency response. One alternative I've seen (although I've not tried it myself) is to use the insert from a crystal microphone in the place of the electostatic speaker, and make sure that the cap which links it from the anode of the output valve to the HT has a high voltage rating as the HT would destroy the crystal.