Less dramatic variations in Dyna A35/A50, some NAIMs, and others.Aperiodic variation.
dave
However, unlike the Dynaco acoustic resistance enclosures (pictured), The Wharfedale columns had twin ports (vents) at the base.
In fact, Briggs referred to them as "vented columns".
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More about Wharfedale's acoustic filter from Briggs' book Loudspeakers:
The original Column 8 showed a dip in response around 150 Hz due to the vertical mode and this was removed by the acoustic filter.
The filter also reduces column resonance in general and cleans up the bass and middle registers.
The output below 100 Hz, we are told, is augmented by the two vents placed near the floor.
The original Column 8 showed a dip in response around 150 Hz due to the vertical mode and this was removed by the acoustic filter.
The filter also reduces column resonance in general and cleans up the bass and middle registers.
The output below 100 Hz, we are told, is augmented by the two vents placed near the floor.
Morning, apologies I have been away for six days without internet (sea cliff climbing). I haven't yet had a chance to investigate the speakers fully. Let me know what you would like to know and I'll strip the speakers down and see if I can answer your questions. It will be a while until I get around to 'renovating' these. I guess one of my first tasks is to work out what the cap value is on the '1943' caps in the crossover. I'll desolder and measure the ESR which should be interesting!
I'd be interested in knowing if there's any maker identification on the drivers, and what their DC resistances are.
If the tweeter is nominally 15 ohm impedance, I'd guess the capacitor is 2 uF for a 5 kHz crossover.
If the tweeter is nominally 15 ohm impedance, I'd guess the capacitor is 2 uF for a 5 kHz crossover.
Hi Galu, When I start stripping the speakers down I'll get back to you with DC resistance. In the meantime I took the top of thhe other speaker (see pictures). Unfortuntely, the tweeter is mising on this speaker. I'll have to source a replacement. There are no markings on the tweeter I have. Also, please see the pictures of the driver, no other than Richard Allan 15ohm. There are two dates, 1968 and 1969.
Richard Allan from Yorkshire no less!
The closest Richard Allan design I can find is the CG8.
In the 1968 Richard Allan catalogue, the CG8 is described thus:
Type: bass/mid driver
Resonance frequency: 55 Hz
Frequency range: 45 Hz - 10,000 Hz
Power handling: 6 W RMS (12 W peak)
Pole diameter: 25.4 mm
Flux density: 14,000 gauss
Total flux: 56,000 maxwells
Weight: 1.8 kg
The driver has a cambric surround.
The closest Richard Allan design I can find is the CG8.
In the 1968 Richard Allan catalogue, the CG8 is described thus:
Type: bass/mid driver
Resonance frequency: 55 Hz
Frequency range: 45 Hz - 10,000 Hz
Power handling: 6 W RMS (12 W peak)
Pole diameter: 25.4 mm
Flux density: 14,000 gauss
Total flux: 56,000 maxwells
Weight: 1.8 kg
The driver has a cambric surround.
An interesting piece of twiddle-twaddle is that there never was a 'Richard Allan'.
"The name was derived from the sons of two founder members: Jack Garfield, whose first son was named Richard, and the son of one of the other founders (possibly Mr Worley?) who was named Allan."
https://www.gracesguide.co.uk/Richard_Allan_Radio
Perhaps of more interest is that the first Class A amplifier made by Sugden was marketed under the Richard Allan name.
"The A21 amplifier made its first public appearance at the ’68 London Audio Fair in London. A 10W-per-channel integrated, it sold for £52, like Leak’s Stereo 30. These amps were handmade and entrusted to a single employee."
https://www.hifinews.com/content/richard-allan-a21-vintage
"The name was derived from the sons of two founder members: Jack Garfield, whose first son was named Richard, and the son of one of the other founders (possibly Mr Worley?) who was named Allan."
https://www.gracesguide.co.uk/Richard_Allan_Radio
Perhaps of more interest is that the first Class A amplifier made by Sugden was marketed under the Richard Allan name.
"The A21 amplifier made its first public appearance at the ’68 London Audio Fair in London. A 10W-per-channel integrated, it sold for £52, like Leak’s Stereo 30. These amps were handmade and entrusted to a single employee."
https://www.hifinews.com/content/richard-allan-a21-vintage
And they still make A21s. Evolved a bit. https://www.sugdenaudio.com/a21-series
Now 23 watts Class A.
dave
Now 23 watts Class A.
dave
I read that Richard Allan's partnership with Sugden was short lived and within a year the amplifier was renamed the SUGDEN A 21.
There's more information for A 21 aficionados here: https://www.audiomisc.co.uk/JES/RA/RAamps.html
"Richard Allan were well established as a manufacturer of excellent loudspeakers. They were located in Cleckheaton, Yorkshire, and were near to Sugden. They had got into discussions with Jim Sugden and arranged to market his Class A designs under their name. This was useful for both parties. Jim Sugden was developing exciting designs that audio fans were interested in buying, and Richard Allan had extensive experience with manufacturing for the UK Hi Fi market."
There's more information for A 21 aficionados here: https://www.audiomisc.co.uk/JES/RA/RAamps.html
"Richard Allan were well established as a manufacturer of excellent loudspeakers. They were located in Cleckheaton, Yorkshire, and were near to Sugden. They had got into discussions with Jim Sugden and arranged to market his Class A designs under their name. This was useful for both parties. Jim Sugden was developing exciting designs that audio fans were interested in buying, and Richard Allan had extensive experience with manufacturing for the UK Hi Fi market."
Hello, apologies for silence I was distracted by a Roland 808 drum machine I got in to fix! Anyway, here are some more pictures of the Sugden's. I dismantled the other speaker and discovered the driver was different from it's partner speaker. I guess one was replaced some time ago or the manufacturer wasn't fussy about what they put in. Any thoughts? I measured the DC resistance and they are as quoted on the driver. I removed one of the crossover capacitors and measured the ESR. As you can hopefully see it weighed in at 1.26UF. Amazing it was still even 'working' given it's age!
Finally, I removed the tweeter, which Galu observed was pointing down into the speaker cab. I measured the DC resistance of this but it was an open circuit so kaput. One question: I need to replace these the tweeters the other one was missing, does anyone have a suggestion as to what I should replace these with??? Also, I intend to replace the caps, should I use a 2.2uF or go for the 1.26uF I measured on the original cap?
Best wishes,
Craig
Finally, I removed the tweeter, which Galu observed was pointing down into the speaker cab. I measured the DC resistance of this but it was an open circuit so kaput. One question: I need to replace these the tweeters the other one was missing, does anyone have a suggestion as to what I should replace these with??? Also, I intend to replace the caps, should I use a 2.2uF or go for the 1.26uF I measured on the original cap?
Best wishes,
Craig
To summarise, one cone tweeter is missing and the other is open circuit. They were probably 15 ohm, but you can replace them with 8 ohm cone tweeters and a suitable choice of capacitor value.
With an 8 ohm cone tweeter I would use a 2.2 uF capacitor to provide a gradual roll off below 9 kHz.
Measure the dimensions of the tweeter and look for a physically compatible substitute. Possibilities are:
https://www.visaton.de/en/products/drivers-accessories/cone-tweeters
https://www.monacor.com/products/components/speaker-technology/hi-fi-tweeters-/ht-22-8/
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Here are some specifications of the Richard Allan CB8 15 ohm mid/bass driver you found in the second enclosure:
Resonance frequency = 55 Hz
Frequency range = 45 Hz - 10 kHz
Power handling = 30 W RMS
Cambric surround
Weight = 0.9 kg
Note: I can't yet find any specs for the Richard Allan Golden Eight that occupies the first enclosure.
I would accept any differences between the two drivers as simply forming part of the charm and originality of this vintage pair of speakers!
Resonance frequency = 55 Hz
Frequency range = 45 Hz - 10 kHz
Power handling = 30 W RMS
Cambric surround
Weight = 0.9 kg
Note: I can't yet find any specs for the Richard Allan Golden Eight that occupies the first enclosure.
I would accept any differences between the two drivers as simply forming part of the charm and originality of this vintage pair of speakers!
I did a total magnetic flux comparison:
CB8: 0.48 milliweber = 48,000 maxwell
Golden 8: 48,000 lines = 48,000 maxwell
So at least we can say that the two different models of mid/bass drivers are equal in that respect.
CB8: 0.48 milliweber = 48,000 maxwell
Golden 8: 48,000 lines = 48,000 maxwell
So at least we can say that the two different models of mid/bass drivers are equal in that respect.
Thank you Galu. As ever I am endebted to your knowledge and guidence. I forgot to mention that the CB8 has a date stamp of 1974 so I think that refutes the hypothesis that the manufacturer used odd speakers. I think the CB8 was probably a replacement.
I'll source some tweeters as suggested, add new caps and give the speakers a try. More to follow when I've completed the refurb.
I'll source some tweeters as suggested, add new caps and give the speakers a try. More to follow when I've completed the refurb.
The later date and the fact the CB8 appears to have a ceramic magnet rather than the Golden Eight's Alcomax II magnet would certainly support that supposition.
For the record, please supply the diameter of the tweeter and the diameter of its cut out hole.
I'm still hoping to learn more about the internal design of the column speaker - see my question in post #25 for example.