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‘Brik Input Sockets

J

jimmymcfarrell

pfm Member
Just recently purchased a pair of Linn Isobariks - having been playing with active Sara’s and stacks of amps, when some ‘Briks became available within sensible driving distance it was obvious they were going to be mine. They’re late model ‘Briks with external crossovers in the stands (not that I’m using the passive crossovers) and separate pairs of 4mm sockets for bass mid & treble. Then there’s a 4th pair of 4mm sockets, what are these for? Are the pairs of drivers wired separately to their respective input sockets & just paralleled at this point? What I’m getting at is can I use this 4th (I’m guessing, currently unused) pair of input sockets to split one of the pairs of drivers and power them individually? And if so, which pair of drivers would most benefit from being powered separately, woofers mids or tweeters? Instinct tells me it would be the woofers however I keep reading that one should use the best (most powerful?) amplifier available on the tweeters when running Isobariks, which seems totally counter-intuitive and may therefore dictate that as all my amplifiers are the same, it would be the two tweeters that would most benefit from being powered separately.
That being said they sound pretty damn good as is......
 
Mine were similar era, and had three pairs of 4mm sockets, bass, mid and treble. One mod that was popular with active Isobarik users was to use a separate power amp for each bass unit. I don't know if Linn ever offered this officially, but the Keltik was done this way, so they may have towards the end of production, perhaps.

The easiest way to find out is to take a 1.5v battery and a pair of wires and connect it briefly to each socket in turn, the external drivers will react but you may be less sure about the internal bass unit. Next level of sophistication would be to measure the DC resistance with a multimeter. The sockets attached to parallel drivers will be around 4 ohms, if the sockets are attached to just one of the B139s then it'll be nearer to 8 ohms. If there is no circuit, then they are just 'spare' sockets.

Ideally you should drive them actively with identical amplifiers, but I never had the funds to do that with mine, and I had two NAP160 an one NAP250, and would swap the 250 around... overall the sound was best with the 250 driving the tweeters, but leaving a 160 on the bass did rob the speakers of the bass control that the 250 offered. I also ran mine for a time with a Leak Stereo 20 on the midrange - it was superb, until the Leak died.

Lots of fun to be had - I also had a dilemma between the NAXO and Linn Activ/bingo crossovers - in my 'big' house the extra bass extension of the Activ/bingo was noticeable, when divorce downsized my living accommodation, I changed to the NAXO as the bass was too much for a small room. If I still had them I'd be playing with DSP and digital crossovers, as I think we maybe never got the best from these remarkable beasts.
 
Jem, thanks for your reply.
Currently, they’re definitely wired as expected: both B-139 to “bass” input, both B-110 to “mid” input & both tweeters to “treble” input. I’m just curious what the spare input sockets would be for. And my idea was as you say to separate the 2 bass drivers and power them separately utilising the conveniently provided pair of 4mm sockets. I just wondered why those spare sockets are there as this was never a factory option. And so it sounds like it’s the bass drivers that will most benefit from being driven independently of each other then and not the 2 mids or 2 tweeters?
If the passive crossovers were originally located in the aperture behind the input sockets (so the version in between DMS PMS with XLRs and the ones with the external crossovers) would the spare pair of inputs originally have been the passive input? This would make mine older than I thought with later crossovers being an addition) I wonder if there’s a pair of passive crossovers in there that I don’t know about?
 
Ah, it's starting to make sense: The version you have is the one with internal (well in a box at the bottom) crossover, and the 'spare' sockets are the passive input. The original crossovers may still be in there, though when the external crossovers came onto the market, dealers used to take the old ones in PX as they had some value for something that I cannot now recall, so you may not have anything in the box.
 
Thanks for the replies, has filled in some of the blanks. So the latest version of the Isobarik which came with the external 4ohm crossover from the factory wouldn’t have the extra pair of 4mm sockets for the passive input & despite mine having the latest crossovers the speakers themselves must be the generation before and the 4ohm crossovers are a later addition. Mine actually have a cannon socket sized hole on the rear baffle filled with glue, so I wonder if the cabinets were originally made when the DMS was still current, possibly at a time when they were just starting to fit the crossovers into the aperture behind the inputs, the 4 pairs of 4mm sockets look to have been there from day one however. Need to wrestle them back down off their stands & have a look at what’s behind that bottom panel.
 
Our current (Aktiv) Briks were bought second hand (late '90s) and had obviously been modded from DMS, such that the original XLR was removed and the hole filled with wood filler, and 3 pairs of banana sockets drilled in at the bottom.
 
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