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Orange isobaric 2x12 cabs


SteveXFR
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Isobarik cabs run two drive units in parallel - one behind the other - in a sealed cabinet. The idea is to prevent standing waves from the main/front driver from reflecting from inside of the cabinet and striking the driver cone out of phase. It is supposed to enable the main driver to act more pistonically, increase bass extension and give a cleaner, greater output than a single driver would. The disadvantages are that Isobarik cabs are usually heavy, bulky and power hungry. Because the drivers are paralleled, they have low impedance and make greater demands on amplification. The principle was invented in the 1950s and a few manufacturers of hi-fi speakers, notably Linn Audio, made them. Modern bass reflex designs and drive units have made them pretty much unnecessary nowadays.

Edited by Dan Dare
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43 minutes ago, SteveXFR said:

Thanks for that. It seems odd then that Orange made them relatively recently. 

 

I've always wondered why they did. They do work, but are expensive and heavy. Although a 2x12, they are effectively a 1x12 (a good one, granted) in terms of output. You can buy a 1x12 from companies like BF, Bergantino, Epifani and others for similar money that will be lighter, less bulky/heavy and give equivalent performance.

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2 hours ago, SteveXFR said:

 What waste reason for the design?

An isobaric configuration reduces the cabinet size required to realize a desired low frequency response. For those of you who know what T/S specs are the Vas is halved compared to one driver, and therefore so is the cabinet volume exclusive of the space taken up by the second driver. The downside is that the cone displacement exposed to the air, T/S spec Vd, is the same for the two drivers as it is for one, so maximum output is the same as with one driver, albeit from a smaller cab. Isobarics were somewhat logical decades ago, when Vas values of 600 liters weren't unusual, making cabs capable of going low really huge. Since the drivers used in the Orange have a Vas around 150 liters the size advantage gained isn't that much, and as you've found it doesn't go nearly as loud as a standard 212, by 6dB to be precise.

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19 minutes ago, Downunderwonder said:

By the time you reduced the cab size of a 110 by dint of making a 210iso the amount of timber saved would be less weight than the extra driver. Craziness. 

I suppose it was about a size statement...but a traditional 2 * 10 isn't exactly unwieldy. I don't think that series of cabs was very successful for them   

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  • 3 weeks later...

Linn Isobariks are one of the most regarded Hi-Fi speakers; they're not small, so the isobaric principle wasn't used to save space.

If I had a warehouse full of kit, there'd be a pair of those Orange ones in there, next to pairs of Ampeg 8x10 and Acoustic bass bins, but I haven't, so I haven't!

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9 hours ago, prowla said:

Linn Isobariks are one of the most regarded Hi-Fi speakers; they're not small, so the isobaric principle wasn't used to save space.

If they weren't isobaric they'd be even larger. They may not seem small today, but they were by the standards of their time. This is a quote from the Linn product information sheet:

Each speaker has two of each drive unit fitted – i.e. two bass, two mid and two treble. The second bass unit is hidden inside the cabinet, behind the visible bass unit and this forms the basis for our patented Isobarik equal-pressure bass system. This means that the front speaker behaves as if it is in a much bigger enclosure.

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I had an SP212 a few years back - picked it up second hand as it was going cheap and I was interested to try one out for myself given that I'd read a lot of people commenting less than favourably from an engineering standpoint, but some saying they sounded good irrespective. I had an original Terror 500 to pair it with so it looked very much the part, seemed like it would take a lot of punishment, and I must admit I quite liked the sound in a band mix - quite 'big' without being overpoweringly loud. Sadly I couldn't get rid of the smell of the previous owner's cigarettes and didn't much like the weight of the thing, so off it went to its next owner and I haven't actually missed it.

 

It was responsible for a fun moment one rehearsal. I'd taken the terror straight from a gig where it was paired with the SP212 and whilst I'd switched it to 4ohm, I hadn't altered the volume control before plugging it into my BF Super 12. It was pointed straight at one of our guitarists when I flicked the standby and played the first note. I nearly cost him a perfectly good pair of strides that day.

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On 20/02/2022 at 04:03, prowla said:

Linn Isobariks are one of the most regarded Hi-Fi speakers

 

Were, not are. The design and components (KEF bass and midrange drivers and a Scanspeak tweeter), whilst good in their day, are not comparable with more modern offerings. I'm not suggesting that everything modern is automatically better, but drive unit technology, cabinet design and measurement capability has advanced considerably since the 1970s.

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