A Linn Isobarik PMS clone for the 21st century?

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Dingman

Member
Joined 2011
AndrewJ said:
Although by its name, isobaric, implies that there is no pressure change within the cavity between the two drivers, this is not actually true. A simple analysis or measurement will reveal this.
Linn used the isobaric technique simply to get the right driver parameters for their chosen box volume and lf limit, something that was not readily available at the time from a single driver, and they were not about to manufacture a custom driver.
Isobaric produces the equivalent of a single driver with double the moving mass, double the Bl and half the impedance, but wastes the output capability that usually two drivers would give. Not a good trade off.
Interestingly, do you know on of the reasons for using the B139? Its because it was the only driver unit that would pass through its own hole!! Think about it, how did they mount the internal driver.....they mounted it through the hole for the front driver by rotating it sideways. You cant do this with a round driver!
And do you know why KEF made the B139 in the first place? At the time there was an extra sales tax on professional speakers. Professional was defined as any speaker having a driver of 10" diameter or greater. By making it 13" x 9", technically KEF could claim it was only 9" wide, avoiding the tax, while its till had the area of a 10" driver.
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This is one of the most interesting things I've read about the DMS. Fascinating how the most simple factors greatly affect the outcome.
 
Mr. dB

Mr. dB

Member
Joined 2003
AndrewJ said:
And do you know why KEF made the B139 in the first place? At the time there was an extra sales tax on professional speakers. Professional was defined as any speaker having a driver of 10" diameter or greater. By making it 13" x 9", technically KEF could claim it was only 9" wide, avoiding the tax, while its till had the area of a 10" driver.
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I thought the tax was higher for consumer loudspeakers than professional, this was supposedly the reason why Spendor added the Coles supertweeter to the BC1 to make it a three-way, so it would qualify for a lower tax.
 
F

flashgo

Member
Joined 2008
Still wonderful

I can't speak to the price, but I've rebuilt a pair of 'Briks along the lines of Simon Hamnett rebuilds, and they're truly wonderful when driven by six of Avondale's current M180-300 amps in an active configuration. These amps are a massively improved re-design of the original NAP-135s. (See the "Avondale Audio" Facebook page and not the public website.) My system sounded significantly better than a Naim Signature / Focal Sopra setup at a nearby dealer. The 'Briks weren't nearly as loud, but they're eminently more natural and listenable.
 
planet10

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
Paid Member
I have been a big NAIM fan. Nait, 2 x NAIT2, 3 x NAP160, and whatever NAC went with it (i mostly used other preamps).

I have been keeping the Avondale sin my interested column. If you were to do a speaker inspired by you could do much better with mordern drivers. But i do have to admit i have a special place for the B139. Used many of those. Sold way, way more.

dave
 
F

flashgo

Member
Joined 2008
Simon has been replacing the mids in his 'Brik rebuilds, and I followed his choice at the time of Monacors in my rebuild. The Monacors are no longer made. He's very friendly to DIYers, so you can call him for advice on current replacement parts. I also replaced the front-facing Hiquphons with current compatible models. The sound is still nicely integrated. Imaging is excellent, thanks to the Avondale amps, and the up-firing tweeters and mids fill the room nicely.
The two requirements for realizing the potential of 'Briks appear to be:
1. Loads of power
2. High ceilings
 
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