Linn's variable Isobarik design?

[SnapperMike]

I'm thoroughly enjoying the isobarik design of my Keltiks. The depth of bass makes me smile out loud.

What I'm trying to find out is why the design of Linn's original Isobarik speakers from the 70's and 80's and the Keltiks from the 1990's differ from the downward firing isobarik design of the Miso's and the current Akubarik loudspeakers.

I understand the isobarik principle, being that two bass units are mounted in a sealed container and driven in parallel so as to effectively double the speaker enclosure volume and extend its bass frequency response beyond what would be possible for otherwise identical speakers. The two bass units in my Keltiks are separated by about 8 inches and create the required enclosure but still both face forward. However, reading about the Akubariks, they have two bass drive units positioned face to face in the base of the cabinet. So the bass drivers in the original Isobarik's and Keltiks face the same way whilst the bass drivers in the Akubariks (and presumably the Miso's) face one another. 

Why is this the case? Also, what initiated the change for Linn to decide to have the bass units firing forward into the room (Isobariks and Keltiks) but then change to a downward firing design as found in the Miso's and Akubariks?

Mike.

 

[akamatsu]

Let's not forget the 530s. One of my favourites.

That's a tough one. At least it is if you don't know the answer. Which I don't. There has to be a reason. There may even be a good reason.

And I'm with you on the smile inducing musical bass.

 

[SnapperMike]

Let's not forget the 530s. One of my favourites.

That's a tough one. At least it is if you don't know the answer. Which I don't. There has to be a reason. There may even be a good reason.

And I'm with you on the smile inducing musical bass.

Thanks Michael, I didn't know that the 530's utilised the isobarik bass principle too. It looks as though that was also downward firing. The same as your Akubariks.

 

[akamatsu]

Thanks Michael, I didn't know that the 530's utilised the isobarik bass principle too. It looks as though that was also downward firing. The same as your Akubariks.

I used to call them "baby bariks." Similar form factor to the Akubariks.

Your query is an interesting one. I'm hoping someone in the know comes along. In the meantime, crank up that bass! :rockin:

 

[HansBertil]

I'm thoroughly enjoying the isobarik design of my Keltiks. The depth of bass makes me smile out loud.

What I'm trying to find out is why the design of Linn's original Isobarik speakers from the 70's and 80's and the Keltiks from the 1990's differ from the downward firing isobarik design of the Miso's and the current Akubarik loudspeakers.

I understand the isobarik principle, being that two bass units are mounted in a sealed container and driven in parallel so as to effectively double the speaker enclosure volume and extend its bass frequency response beyond what would be possible for otherwise identical speakers. The two bass units in my Keltiks are separated by about 8 inches and create the required enclosure but still both face forward. However, reading about the Akubariks, they have two bass drive units positioned face to face in the base of the cabinet. So the bass drivers in the original Isobarik's and Keltiks face the same way whilst the bass drivers in the Akubariks (and presumably the Miso's) face one another. 

Why is this the case? Also, what initiated the change for Linn to decide to have the bass units firing forward into the room (Isobariks and Keltiks) but then change to a downward firing design as found in the Miso's and Akubariks?

Mike.

My understanding (not confirmed) is that you want to keep the volume between the drive units small which might be the result when placing the drive units face to face. Otherwise the benefits with face to face mounting is that non-linearities in the motor system will be minimized since when one cone is moving outward the other is moving inward; the space taken from the enclosure volume is less compared to face to back mounting; connection wires are more easy to route (air tight). Drawback with face to face mounting is that the motor system on the outer drive unit is visible - it looks awkward. This might be one reason for firing them downwards. Another reason on the Akubariks is that baffle width could be kept narrow The isobaric elements are 200 mm and the upper bass 150 mm. Due to the curved side walls the isobaric element could be squeezed in from underneath and the baffle width be adapted to the size of the smaller upper bass unit. Furthermore, firing downwards will set a given distance between the drive unit and the bottom plate resulting in a given acoustic loading on the element. If the isobaric system is mounted on the cabinet rear to somewhat hide the motor system the acoustic loading can be anything between “pushed against the back wall” to “free space”.

Wilson Benesch has one standmount with isobaric bass where the motor system is visible. Maybe not so good looking. Even the ports are extended outside the cabinet likely to save enclosed volume.

https://www.google.com/search?q=wilson+benesch&tbm=isch&ved=2ahUKEwi2xYr53bX1AhWfCBAIHRHDAhAQ2-cCegQIABAC&oq=wilson+bene&gs_lcp=ChJtb2JpbGUtZ3dzLXdpei1pbWcQARgBMgcIIxDvAxAnMgUIABCABDIFCAAQgAQyBQgAEIAEMgUIABCABDoECAAQGDoGCAAQCBAeOgQIABBDOgoIIxDvAxDqAhAnUNQJWKdgYLFyaAFwAHgAgAFciAHdDZIBAjI4mAEAoAEBsAEFwAEB&sclient=mobile-gws-wiz-img&ei=QcfjYfagDJ-RwPAPkYaLgAE&bih=719&biw=1112&prmd=isnxv&rlz=1C9BKJA_enSE770SE770&hl=en-GB#imgrc=2zxmowTKXsPmlM

 

[Clavius]

Yes, @HansBertil by coupling the bass units face to face they operate with a 180 degree phase shift and their non linearities effectively cancel. Also the smaller air-spring (amount of trapped air) between the drivers in a clamshell push-pull configuration will help towards a true isobaric configuration. Another overlooked fact is that BL, or the motor force, of the system is doubled and of course the box size is halved for isobaric loading.  Proximity to the floor helps with bass gain.

 

[Clavius]

double post

 

[sunbeamgls]

I'm thoroughly enjoying the isobarik design of my Keltiks. The depth of bass makes me smile out loud.

What I'm trying to find out is why the design of Linn's original Isobarik speakers from the 70's and 80's and the Keltiks from the 1990's differ from the downward firing isobarik design of the Miso's and the current Akubarik loudspeakers.

I understand the isobarik principle, being that two bass units are mounted in a sealed container and driven in parallel so as to effectively double the speaker enclosure volume and extend its bass frequency response beyond what would be possible for otherwise identical speakers. The two bass units in my Keltiks are separated by about 8 inches and create the required enclosure but still both face forward. However, reading about the Akubariks, they have two bass drive units positioned face to face in the base of the cabinet. So the bass drivers in the original Isobarik's and Keltiks face the same way whilst the bass drivers in the Akubariks (and presumably the Miso's) face one another.

Why is this the case? Also, what initiated the change for Linn to decide to have the bass units firing forward into the room (Isobariks and Keltiks) but then change to a downward firing design as found in the Miso's and Akubariks?

Mike.

There are a few reasons, most of which will apply:

- the main one is that the moderm speakers have a larger "mid-range" driver which goes lower, allowing the bass drivers to cover only non-directional frequencies so the location of the bass drivers becomes non-critical for imaging purposes;
- by locating the bass drivers in the base of the cabinet, the distance between the driver and the nearest room boundary goes from being a variable to a fixed value, which makes for more consistently predictable results.
- moving the big drivers off the front baffle makes for a more domestically acceptable cabinet.

Also worth noting is the modern designs are ported enclosures whereas Isobarik and Keltik are sealed designs.

 

[bencat]

Not sure which version of the above my Linn Sara 9's use but they sounded excellent when they were passive despite each speaker housing one of the most complicated crossovers I have ever seen these could well have been sucking the life out of the speakers. Luckily I have now converted these to a full active two way using digital cr and they now sound even better and just a little less coloured than they use to . The bass from this small speaker is tight and very powerful .

 

[HansBertil]

Not sure which version of the above my Linn Sara 9's use but they sounded excellent when they were passive despite each speaker housing one of the most complicated crossovers I have ever seen these could well have been sucking the life out of the speakers. Luckily I have now converted these to a full active two way using digital cr and they now sound even better and just a little less coloured than they use to . The bass from this small speaker is tight and very powerful .

Sara bass elements are placed back to front in the cabinet. That was really some crossover. Although an isobaric design it is only a two way speaker. Likely a few dB are dumped in that circuitry.

 

[akamatsu]

Sara bass elements are placed back to front in the cabinet.

I did some reading about this yesterday. All the early Linn speakers were sealed enclosures. Both Saras and Isobariks used front to back (I call it spooning) arrangement in an hermetically sealed box. Linn then started making ported speakers when Dr. Rod Crawford showed up from Australia. Here's the story:

http://www.legendspeakers.com.au/Backup-old-site/legendstory.php

 

[pdcman]

mmmm.... but which speaker gives to a decent live sound 'thump in the belly' bass? Hint, its not the Akubariks.

 

[Imseti]

mmmm.... but which speaker gives to a decent live sound 'thump in the belly' bass? Hint, its not the Akubariks.

Keltiks!

 

[Tendaberry]

mmmm.... but which speaker gives to a decent live sound 'thump in the belly' bass? Hint, its not the Akubariks.

Well, the Komris of course

 

[NL.]

I wonder why Linn didn’t use isobaric in Komris, Artikulats and 350s ? Is it possible to have servo controlled isobaric bass driver? I suppose it is…

Earlier top of the range speakers (Isobariks and Keltiks) benefited from the isobaric concept… Also, Linn discontinued Majik Isobarics, which were IMHO better performing in bass area.

 

[NL.]

I also wonder if Akubariks were designed as ported isobarics, or sealed enclosure isobarics?

The same question applies for 350… I didn’t find any data in that respect. But I haven’t find any port on mine, so I assume both bass drivers are imbedded in sealed boxes.

 

[Suffolkboy]

I also wonder if Akubariks were designed as ported isobarics, or sealed enclosure isobarics?

The same question applies for 350… I didn’t find any data in that respect. But I haven’t find any port on mine, so I assume both bass drivers are imbedded in sealed boxes.

Akubariks are ported. 530s are isobaric. 350s are sealed enclosure.

 

[akamatsu]

Akubariks are ported. 530s are isobaric. 350s are sealed enclosure.

Akubariks are ported. But that's about all I can tell about them from looking. I haven't found any photos showing the insides. As was stated here, the two drivers are in a front to front configuration. I figure that the two ports are open to the upper driver, and the bottom driver is exposed at the visible cone.

As for 530s, I'm thinking same front to front drivers but in a completely sealed enclosure above the upper driver?

Edit: I just found this photo. So the 530s are ported, and appear to have the same configuration as the Akubariks.

 

[HansBertil]

I wonder why Linn didn’t use isobaric in Komris, Artikulats and 350s ? Is it possible to have servo controlled isobaric bass driver? I suppose it is…

Yes. Akubarik active and Exakt has servo controlled bass.

 

[Moomintroll]

Yes. Akubarik active and Exakt has servo controlled bass.

I don’t see this anywhere in the documentation. Have you read this somewhere?

’troll