@ Inuctor
"Bama, bama!"
Can't help If You don't know . . . . the past top technology . .
Yes, they manage in 3 days and each LP disk was cost from 250 to 300 German Marks in that time, only very small production run and only limited time, cost object perhaps?
just the best what money can buy. . . .
Regards
Andrew
"Bama, bama!"
Can't help If You don't know . . . . the past top technology . .
Yes, they manage in 3 days and each LP disk was cost from 250 to 300 German Marks in that time, only very small production run and only limited time, cost object perhaps?
just the best what money can buy. . . .
Regards
Andrew
Hello, I have just purchased a lovely black pair of Isobariks. I would love to be able to build my own and wondered if anyone had a drawing for them. Yes I have seen the "exploded" images, but need full dimensions. I should have tore apart the cheap pair I bought many years ago. I do have 4 pairs of B139s, 2 pair of B110s, and 2 pair of T27s (the replacement option for these speakers). I also have purchased a lovely :LK1 & LK2 (which was the origional pairing for the isobarik....by the way, I am happy to sell at least 1 pair of B139s
Thanks...Stuart
Thanks...Stuart
Hardly, back when I thought the earth was still flat, 1800's, mine had NAC42, NAP160's and I forget what the xover was called (NAXO?).
I'd also enlarge and extrapolate from the exploded drawings as none of the dimensions will be all that critical.
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As you already have a pair, 20 mins with a screw driver and tape measure will get enough dimensions to be able to work out the rest.
So you would blindly accept something posted on the net over your own measurements? I doubt you're going to get factory drawings.
So what? It's not a TL. It's sealed in the rear which is very tolerant of slight differences. Something you'd know if you'd ever built a few.
A smaller front LF chamber, such as clam shelling the drivers would reduce distortion: hint, make it as small as you can.
So find the T/S and model them in a good estimate of the sub enclosure volume, as well as 2x and 0.4x and I bet you'll find 2/10ths of F'all difference in the raw response, let alone the net with a xover in place.
And the tweets are sealed in the back so it doesn't matter as they are effectively in their own enclosure.
There is nothing magic in what Linn did decades ago, and thinking that by to the mm slavishly copying it is going to produce identical sound is foolish. It's simply not that critical. Individual driver tolerances will readily swamp that.
Hi,
I wish people understood isobaric properly. Its nothing flash in the way
Linn did it in the Isobarik and the Sara, and is no better than properly
specified driver parameters for the sealed box volumes involved.
Subwoofers with heavy cones are the equivalent of two drivers
with lighter cones mounted in the same direction. Presumably
you should go for a 10" 4 ohm subwoofer with Qbox the same
as the Isobarik and Fbox the same or even lower if you can.
Its just sealed loading, done with two drivers at half impedance
to get box parameters for the box size you can't get with one
of the drivers. But for the box size you can go directly to
half impedance (4ohm) and your wanted parameters with
an intelligent single driver choice in the first place.
Going isobarik is equivalent to choosing a driver 3dB less efficient.
rgds, sreten.
Hi,
That depends on your target numbers, 4ohm sensitivity, box volume,
Qbox and Fbox, might take a look later based on 2 isobaric B139's.
rgds, sreten,
If i had 4 B139s, i'd be doing a pair of one of these TLs (i have the ceilings for the straight ones 
.
Transmission Line Speakers
dave
.Transmission Line Speakers
dave
Reply number two
Hi,
OK, based on these numbers, 70's version of the driver :
8 ohm, 87dB, 3.0mm Xmax, 25Hz Fs, 0.37 Qts, 164L Vas
the only thing things that change for isobaric are :
a) Senstivity is still 87dB but efficiency wise its an 84dB / watt driver.
b) Impedance halves to 4 ohms
c) Vas halves to 82L
d) moving mass doubles
FWIW sealed box for Q=0.7 isobaric pair is 31L, Fbox = 50Hz (-3dB).
100L gives Qbox = 0.5 critically damped, Fbox = 34Hz (-6dB).
A fair compromise is around Bessel, around Q=0.6 (50L).
The numbers are fair enough and show a single driver needs big boxes.
Pity a lot of the time KEF didn't put them in particularly big boxes.
One trick used is about 1cuft with a series capacitor.
Most noteworthy IMO of the above spec is the 3mm Xmax, 6mm pk to pk.
Its pathetic by subwoofer and decent large woofer standards.
Europe Audio
Just by inspecting this TB 8"x12" woofer you can see its very near equivalent to
two isobaric B139's, 4 ohm, Vas is 70L, Fs 27Hz, Qts 0.34, and "efficiency" 85dB/W.
similarly with this Dayton 10" 4 ohm sub :
http://www.parts-express.com/pdf/295-460s.pdf
though here Qts is somewhat higher.
The reason ? The Tangband has an ~ twice as heavy cone as the
B139 and the Dayton even more, approaching 3 times approximately.
The most eyeopening spec is the Xmax for the two above, 12mm, 24mm pk to pk.
If cone areas are the same that equates to +12dB higher maximum
SPL and if sensitivities are the same (which they nearly are) 16 (!)
times the excursion limited power handling in the low bass.
That doesn't sound right does it ? But that is what the numbers say .....
(Perhaps 12mm is pk to pk, but that is still +6dB and 4 times the power handing.
Cross checking though it seems 12mm one way is doable with the above specs.)
FWIW the Isobarik required wall loading for the bass to be able to
keep up with the rest. I'd make the bass/mid c/o active at least
so bass sensitivity can be adjusted to match the mid /treble.
rgds, sreten.
Playing with the TB sealed you get a Bessel, Q=0.57 in 40L.
Same box vented low at 22Hz also looks very good.
Hi,
OK, based on these numbers, 70's version of the driver :
8 ohm, 87dB, 3.0mm Xmax, 25Hz Fs, 0.37 Qts, 164L Vas
the only thing things that change for isobaric are :
a) Senstivity is still 87dB but efficiency wise its an 84dB / watt driver.
b) Impedance halves to 4 ohms
c) Vas halves to 82L
d) moving mass doubles
FWIW sealed box for Q=0.7 isobaric pair is 31L, Fbox = 50Hz (-3dB).
100L gives Qbox = 0.5 critically damped, Fbox = 34Hz (-6dB).
A fair compromise is around Bessel, around Q=0.6 (50L).
The numbers are fair enough and show a single driver needs big boxes.
Pity a lot of the time KEF didn't put them in particularly big boxes.
One trick used is about 1cuft with a series capacitor.
Most noteworthy IMO of the above spec is the 3mm Xmax, 6mm pk to pk.
Its pathetic by subwoofer and decent large woofer standards.
Europe Audio
Just by inspecting this TB 8"x12" woofer you can see its very near equivalent to
two isobaric B139's, 4 ohm, Vas is 70L, Fs 27Hz, Qts 0.34, and "efficiency" 85dB/W.
similarly with this Dayton 10" 4 ohm sub :
http://www.parts-express.com/pdf/295-460s.pdf
though here Qts is somewhat higher.
The reason ? The Tangband has an ~ twice as heavy cone as the
B139 and the Dayton even more, approaching 3 times approximately.
The most eyeopening spec is the Xmax for the two above, 12mm, 24mm pk to pk.
If cone areas are the same that equates to +12dB higher maximum
SPL and if sensitivities are the same (which they nearly are) 16 (!)
times the excursion limited power handling in the low bass.
That doesn't sound right does it ? But that is what the numbers say .....
(Perhaps 12mm is pk to pk, but that is still +6dB and 4 times the power handing.
Cross checking though it seems 12mm one way is doable with the above specs.)
FWIW the Isobarik required wall loading for the bass to be able to
keep up with the rest. I'd make the bass/mid c/o active at least
so bass sensitivity can be adjusted to match the mid /treble.
rgds, sreten.
Playing with the TB sealed you get a Bessel, Q=0.57 in 40L.
Same box vented low at 22Hz also looks very good.
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I still have a similar system:
- Speakers: Linn Isobarik
- Record deck: Linn LP 12
- Turntable power supply: Linn Lingo
- Arm: Linn Ekos
- Cartridge: Linn Akiva
- CD player: Rega Planet
- Phono pre-amplifier: Kinshaw Perception
- Preamplifier: Exposure XI
- Power amplifier: (x 3) Exposure Super VIII
- Power supply: Exposure IX
- Active Crossover: Exposure V
I love the system, and also use it as part of my TV surround sound setup (Bariks are used for L and R speakers and subwoofer). I also use a Pioneer VSX-LX52 with MK Xenon centre and rear speakers.
I'd be interested to hear how your quest for Isobarik sound works out...
Speaker Builder magazine had several articles and designs for Isobariks in the late 80s and 90s. Some of them went into the principles and why they thought it worth pursuing.
FWIW, I'd have thought modern driver technology could do better now but it depends how much you want to recreate an old, idiosyncratic loudspeaker of questionable hi-fi merit. Remember, Linn were keen at the time to promote the idea that there was no such thing as stereo image - possibly because their speakers weren't very good at it. And yes, I have heard the original Isobariks.
FWIW, I'd have thought modern driver technology could do better now but it depends how much you want to recreate an old, idiosyncratic loudspeaker of questionable hi-fi merit. Remember, Linn were keen at the time to promote the idea that there was no such thing as stereo image - possibly because their speakers weren't very good at it. And yes, I have heard the original Isobariks.
Sreten is fully right.
What is even worse with the B139, of the many ones I happened to own in the early 80ties, not a single one measured a Fo below 32 Hz and some had an Fo as high as 38 Hz. Furthermore, the entire moving assembly was aligned so poorly in some cases they started to distort audibly even slightly above domestic listening levels. A nice thing in the late sities and early seventies, a highly overrated driver afterwards.
Eelco
Agree. I am in the process of "restoring" my DMS briks, and turning them into active ones using 4 hypex nc400 amp modules per box (1 each for the woofers, 1 for the mids and 1 for the tweeters), and a digital crossover.
I think Stuart mentioned the T27's as a "replacement option".
The original 'bariks used the Scan-Speak D2008, and then the made-for-Linn the Hiquphon D20-LP-1(from 1983) or D20-LP-2 (from 1988). The Hiquphon units are still made, but are not cheap. Not sure about the Scan-Speak.
A cheaper alternative of push-pull isobaric principle is a clone of the Totem Mani-2. Read the Stereophile rewiev first...... The original uses Dynaudio woofers, the clone (same box size, slightly different tuning) Hi-Vi D6.8-s. Sensitivity and impedance are pretty low (around 83-84 dB, and 3 ohms), but the bass for the size of the box is astonishing, in-room you can get down to 26-28 Hz.
