hatrack71
distracted by everything
Interesting. Maybe they have a spare pair of the horn lenses minus the ribbon drivers.:scratch2:
Decca London Ribbon Tweeters -- project application ?
- Thread starter Ohighway
- Start date
Interesting. Maybe they have a spare pair of the horn lenses minus the ribbon drivers.:scratch2:
Michael-Otto
Well-Known Member
That is a DECCA LONDON RIBBON HF LOUDSPEAKER from DECCCA Special Products.
I was 1974 in the Factory Shop in London and bought 2,
the price for 2 was 50 pounds + 8% Vat.
Some info from am a DECCA flyer.
The New London High Frequency Speaker
The new London High Frequency Speaker is the tatest result of the continuous development by Decca of speakers using the ribbon principle. This unit possesses all the inherent advantages of its predecessor the DK30 while being able to handle frequencies from 1000Hz to beyond the audio range. Now bass speakers specifically designed for handling only the low frequencies (previously only usable with the ribbon speaker in conjunction with a mid range unit) can be used with the London Ribbon Speaker in a two unit system. This eliminates the added phasing problems encountered with three-speaker systems.
The existence of the London Speaker is important in that it coincides with the emergence an the-Hi Fi market of pick-ups and amplifiers which can faithfully reproduce the top end of the frequency spectrum. However, what is not generally appreciated is that many types of conventional moving coil tweeters are unable to reproduce the complicated transients, and often cause listening fatigue through their attempts to do so. The quotation of a frequency response gives no indication of a speakers transient response: standardisation of a method of transient response quotation is still a matter of controversy.
What makes the ribbon speakerdifferent?
The answer lies in the ribbon itself (only 1/10th the thickness of a human hair), which, being the only moving part of the speaker, and with a very low mass has, therefore, very low inertia. This factor allows the ribbon to reproduce accurately the middle and top frequencies, while still preserving the transient characteristic. An alternating current flowing through this ribbon produces its own magnetic field which reacts with that of the magnet system. The resultant mechanical force is applied uniformly and in phase over the whole diaphragm. This ensures a remarkably smooth response, free from resonance, quite unlike conventional moving coil type tweeters where the force is applied only at the line of contact between the voice coil and the diaphragm.
The rear face of the ribbon terminates in an acoustic resistance contained in a sealed cavity allowing the unit to be mounted in low frequency enclosures without any intermodulation effects whatsoever. The ribbon is coupled to the air by a specially designed horn, which gives high coupling efficiency at all frequencies from 1 K to 35KHz. The horn incorporates a fin to ensure correct dispersion of sound.
The transformer of the London Ribbon speaker is of special design and has a insertion loss of less than 1dB and maximum distortion of less than 0.5% from the operating frequencies band at 30 watts input. lt is essential that the ribbon is protected by the use of a suitable cross-over. The ideal cross-over frequency is 1,000 Hz at which frequency cut-off rate should not be less than 12dB per octave.
Crossover Network CO/1000/8
Mounted an a ridged printed board, close tolerance carbon polyester capacitors and inductors are used ensuring unvarying performance. The low pass section is a standard, constant-impedance, 6dB per octave filter while the high section attenuates at 12dB per octave. The cross-over frequency is 1,000Hz and intermodulation distortion is virtually eliminated.
Technical Specifications
LONDON RIBBON SPEAKER
Frequency response: 1,000 to 25,000 Hz
Power capacity (average speech and music Brit. Stand.) 30 watts max.
Impedance: 8/15 ohms
Dynamic Mass: 10 milligrams
Force/Mass ratio: 7 10-7 dynes per gram per watt
Horn loading : Resistive above 1,000 Hz/750 Hz cut-off
Distortion : Less 7han 1.7% at 2,5Hz with 30 watts inp,
CROSSOVER NETWORK
Crossover Frequency : 1,000 Hz
Low Pass Slope: 12dB per octave
High Pass Slope: Initially 12dB per octave,and final slope 45dB per octave:
attenuation at frequencies below, 700 Hz greater than 40 dB
Insertion Loss: Less than 1 dB in pass band
Impedance:8 ohms constant
Michael-Otto
I was 1974 in the Factory Shop in London and bought 2,
the price for 2 was 50 pounds + 8% Vat.
Some info from am a DECCA flyer.
The New London High Frequency Speaker
The new London High Frequency Speaker is the tatest result of the continuous development by Decca of speakers using the ribbon principle. This unit possesses all the inherent advantages of its predecessor the DK30 while being able to handle frequencies from 1000Hz to beyond the audio range. Now bass speakers specifically designed for handling only the low frequencies (previously only usable with the ribbon speaker in conjunction with a mid range unit) can be used with the London Ribbon Speaker in a two unit system. This eliminates the added phasing problems encountered with three-speaker systems.
The existence of the London Speaker is important in that it coincides with the emergence an the-Hi Fi market of pick-ups and amplifiers which can faithfully reproduce the top end of the frequency spectrum. However, what is not generally appreciated is that many types of conventional moving coil tweeters are unable to reproduce the complicated transients, and often cause listening fatigue through their attempts to do so. The quotation of a frequency response gives no indication of a speakers transient response: standardisation of a method of transient response quotation is still a matter of controversy.
What makes the ribbon speakerdifferent?
The answer lies in the ribbon itself (only 1/10th the thickness of a human hair), which, being the only moving part of the speaker, and with a very low mass has, therefore, very low inertia. This factor allows the ribbon to reproduce accurately the middle and top frequencies, while still preserving the transient characteristic. An alternating current flowing through this ribbon produces its own magnetic field which reacts with that of the magnet system. The resultant mechanical force is applied uniformly and in phase over the whole diaphragm. This ensures a remarkably smooth response, free from resonance, quite unlike conventional moving coil type tweeters where the force is applied only at the line of contact between the voice coil and the diaphragm.
The rear face of the ribbon terminates in an acoustic resistance contained in a sealed cavity allowing the unit to be mounted in low frequency enclosures without any intermodulation effects whatsoever. The ribbon is coupled to the air by a specially designed horn, which gives high coupling efficiency at all frequencies from 1 K to 35KHz. The horn incorporates a fin to ensure correct dispersion of sound.
The transformer of the London Ribbon speaker is of special design and has a insertion loss of less than 1dB and maximum distortion of less than 0.5% from the operating frequencies band at 30 watts input. lt is essential that the ribbon is protected by the use of a suitable cross-over. The ideal cross-over frequency is 1,000 Hz at which frequency cut-off rate should not be less than 12dB per octave.
Crossover Network CO/1000/8
Mounted an a ridged printed board, close tolerance carbon polyester capacitors and inductors are used ensuring unvarying performance. The low pass section is a standard, constant-impedance, 6dB per octave filter while the high section attenuates at 12dB per octave. The cross-over frequency is 1,000Hz and intermodulation distortion is virtually eliminated.
Technical Specifications
LONDON RIBBON SPEAKER
Frequency response: 1,000 to 25,000 Hz
Power capacity (average speech and music Brit. Stand.) 30 watts max.
Impedance: 8/15 ohms
Dynamic Mass: 10 milligrams
Force/Mass ratio: 7 10-7 dynes per gram per watt
Horn loading : Resistive above 1,000 Hz/750 Hz cut-off
Distortion : Less 7han 1.7% at 2,5Hz with 30 watts inp,
CROSSOVER NETWORK
Crossover Frequency : 1,000 Hz
Low Pass Slope: 12dB per octave
High Pass Slope: Initially 12dB per octave,and final slope 45dB per octave:
attenuation at frequencies below, 700 Hz greater than 40 dB
Insertion Loss: Less than 1 dB in pass band
Impedance:8 ohms constant
Michael-Otto
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