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January 14, 2012 / consort3

Metal dome tweeters

The Metal dome device was introduced to the Uk market in the shape of the Celestion SL6 speaker back in 1981. Monitor Audio introduced them in 1986. I actually bought some similar tweeters from Mo Iqbal the founder of Monitor Audio from his Tottingham factory about 1991. Actually Tottenham, but I prefer Ossie Ardiles pronunciation! The factory was the old Elac plant, confusingly there is a unrelated German speaker company with the same name.

http://www.falconacoustics.co.uk/falcon-archive-links-history-tips/falcon-acoustics-archive/imf-tdl-drive-unit-elac.html

http://www.avsforum.com/forum/89-speakers/1999074-elac-opens-north-american-design-facility-headed-andrew-jones.html

Early ELAC product

elac

Another thing out of Tottenham was the Dave Clark 5 who had a stomping hit Glad all over. Just watched a BBC documentary which showed that they were talented, smart and succesful. The documentary caught the zeitgeist. Funny how Glad all over is Crystal Palace’s theme tune rather than Tottenhams.

Not a lot of people know that Martin Colloms the Hi-Fi author & journalist was a co-founder of M.A.  After a brief dalliance with the metal dome I went back to soft dome types. Metal domes measure well but I find they are fatiguing after a while. I recently came across Richard Russels website (scroll down for the metal vs soft dome bit)

http://www.roger-russell.com/driverst.htm

A possible reason for the fatigue is the ultrasonic resonance of metal dome types. I measured the resonance of mine as 24.8kHz. Now the argument goes you cannot hear that high. However if you excite the tweeter with a transient  it rings at the resonant frequency which puts modulation on the waveform. The ear is an envelope detector and thus you hear what might be described as a thickening of the transient. It can sound good, I remember listening to a flamenco recording which had so much metallic ‘fire’ that you could have sworn the performers were in the room. But for those seeking truth, what do we do? Fortunately by adding a LC filter across the tweeter we can stop the resonance. I found I needed a 68 uH choke and a 0.61 uF capacitor in series across the tweeter to act as filter. However the 68uH choke measured 0.62 uH so I used a 0.66 capacitor (actually three 0.22 uF’s in parallel) The product of the 2 values has to be the same. If the tweeter is driven actively the low output impedance of the amp would damp the resonance.

When I measured this on the IMP MLSSA the impulse response showed the ringing has disappeared. I  tried  it on a speaker with the metal dome and it reduced the fatigue. The Celestion SL6 had the notch filter.

I recently saw  frequency response plots for some digital amps and they show an ultrasonic resonance  about the same frequency as the tweeter. Listening to a combination of the two would sound horrible! Another reason for Class D amps sounding bad:

http://www.planetanalog.com/author.asp?section_id=3065&doc_id=564363&

Talking of Flamenco, Manitas de Plata has passed away. He was an untypical performer being French and not sticking to the so-called rules:

http://www.youtube.com/watch?v=Eex1aqbfP08#t=39

Segovia in Dire straits. Spanish classical guitar version of Sultans of swing

http://www.youtube.com/watch?v=OcdrVidwmPY

Fantastic Spanish guitar Rodrigo y Gabriela Tamacun

https://www.youtube.com/watch?v=l-qgum7hFXk

Just to show how multicultural this is, The Isle of Mans most famous sons the Bee gees song performed by Jose Feliciano

https://www.youtube.com/watch?v=154qSmFBydg

The first rock star?

http://www.islamicspain.tv/Arts-and-Science/flight_of_the_blackbird.htm

I am interested in the cultural shift from Moorish Spain via Occitania to northern Europe. Was this helped or hindered by the complex geo-political situation at the time on what became the French/Spanish border. Helped I would say as the Nobles made strategic alliances by marrying their daughters to neighbouring states leaders. The unlucky daughters like Eleanor of Aquitaine and Katherine of Aragon ended up being married to English Kings!

Troubadour Poetry

Troubadour music

Occitan

Flamenco

https://en.wikipedia.org/wiki/Marca_Hispanica

The Troubadour music article mentions the Cathars, an interesting Sect. Ian Meadows wrote an article for the Spectator in 1973 about them:

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