Isobaric Loudspeakers

[Richard Allen]

Hi.

I know this was discussed at length on here some 2 years ago but I can't find the thread. Now that the likes of Davedotco are on here I should like some opinions please.

What do you think of this type of loading in a loudspeaker?. Good, Bad or never heard one?. The design intrigues me that's all.

 

[davedotco]

On a theoretical level I have never really undestood the advantage of isobaric loading. Resonant frequency of the drivers are largely unchanged, the movement of the bass drived might be a little more linear (the air in the enclosure is not compressed) and the enclosure can be made smaller (but not by a lot).

On the other hand, it is complex and expensive, the extra power handling does not give a substantial increase in output and in the designs that I am familier with, results in a pretty low impedance.

That said, apart from the two old Linn models, I am struggling to think of any examples. I believe Neat have used this technique in recent times, maybe you should speak to Bob and his team.......*unknw*

 

[Richard Allen]

On a theoretical level I have never really undestood the advantage of isobaric loading. Resonant frequency of the drivers are largely unchanged, the movement of the bass drived might be a little more linear (the air in the enclosure is not compressed) and the enclosure can be made smaller (but not by a lot).

On the other hand, it is complex and expensive, the extra power handling does not give a substantial increase in output and in the designs that I am familier with, results in a pretty low impedance.

That said, apart from the two old Linn models, I am struggling to think of any examples. I believe Neat have used this technique in recent times, maybe you should speak to Bob and his team.......*unknw*

Spoke to Bob ages ago. See Dave, I've got this idea of using 2 Isobarically loaded pairs in each cabinet. Spiced it and it all seems to work ( in theory anyway ) with a pretty benign 8 ohm load ( 6.3 resistive ). I wouldn't mind so much if it was just a ponder, but it just won't go away. Driving me nutso!!.*dash1*

 

[Al ears]

I pressume I might be teaching my grandmother to suck eggs, so to speak, by suggesting this post:-

http://www.musicanddesign.com/Isobaric.html

 

[Vladimir]

If you got those IMO impressive 8 ohms and >84dB, I would definitely vote for such a speakers to be made. Those would be rare gems on today's market.

 

[davedotco]

We all get these crazy ideas.......*wacko*

I'm still at a loss to see what advantages such a configuration would bring to the table, perhaps you could explain what this would achieve over, say, a much better and more expensive single driver in an appropriate enclosure.

As for working on 'silly' ideas, back in the day when i could do this sort of stuff, I had a project involving my favourite bass driver, the JBL 2212, and the then very rare TAD compression driver as a high power, two way domestic monitor. I got as far as having the cabinets built, got BSS to build me a custom electronic crossover and was chatting to Westlake Audio about their 'baby' 1 inch wooden horn for the TAD.

Then I started to think how much this was costing.........

 

[Richard Allen]

If you got those IMO impressive 8 ohms and >84dB, I would definitely vote for such a speakers to be made. Those would be rare gems on today's market.

You sitting comfortably Vlad??. Try 88/89dB @ 2.8 volts!!!. This is the bit that's driving me nuts. And all in an enclosure 100cms tall, 24cms wide, 28cms deep. Crazy right??. Checked the model 9 times now. It's right though.*wacko*

 

[davedotco]

If you got those IMO impressive 8 ohms and >84dB, I would definitely vote for such a speakers to be made. Those would be rare gems on today's market.

You sitting comfortably Vlad??. Try 88/89dB @ 2.8 volts!!!. This is the bit that's driving me nuts. And all in an enclosure 100cms tall, 24cms wide, 28cms deep. Crazy right??. Checked the model 9 times now. It's right though.*wacko*

Time to stop computer modeling and start building. Just build the bass section and see what you get in practice, if it works you can design the rest of the speaker to suit.

Tiny enclosure, can you really maintain accurate isobaric loading in something that small?

 

[Richard Allen]

We all get these crazy ideas.......*wacko*

I'm still at a loss to see what advantages such a configuration would bring to the table, perhaps you could explain what this would achieve over, say, a much better and more expensive single driver in an appropriate enclosure.

As for working on 'silly' ideas, back in the day when i could do this sort of stuff, I had a project involving my favourite bass driver, the JBL 2212, and the then very rare TAD compression driver as a high power, two way domestic monitor. I got as far as having the cabinets built, got BSS to build me a custom electronic crossover and was chatting to Westlake Audio about their 'baby' 1 inch wooden horn for the TAD.

Then I started to think how much this was costing.........

What it means IF I cabinetise it, is it will realise more significant Bass output from a 'relatively' small cabinet whereas if I went down the single driver route the cabinet would a) have to be twice the size and b) it would have to be reflex loaded. Imagine a monster like that with all the room boundry issues it would have. A complete non-starter IMO.

As regards cost, I have all the bits I need in stock. Just have to build a pair of cabinets. The question is (?????) would it sell if it worked?. Sensitivity wise it should be OK to drive with a relatively 'small' amp. Impedance is, as I said relatively benign at 8 ohms. That's my dilema. Hence asking for input.

 

[Richard Allen]

Time to stop computer modeling and start building. Just build the bass section and see what you get in practice, if it works you can design the rest of the speaker to suit.

Tiny enclosure, can you really maintain accurate isobaric loading in something that small?

The trick I think is matching the parameters of the drivers. I can check em individually on Clio. Plus, the closed box should help to keep things tight ( I hope ). Still haven't gotta clue wot I'm doing this for though.

 

[davedotco]

I was under the impression that you could not make the isobaric setup too small due to pressure in the second chamber but I am absolutely no expert here.

I guess the big question is whether or not it would sell, everyone wants floor standers in the current market but as far as I can see, they want them cheap and with loads of bass.

Would enough people understand and purchase a big (ish) speaker with a flat response? I genuinely don't know, with that kind of sensitivity they should demo ok, but without the 'obvious' bass presence will they be chosen?

 

[Vladimir]

I was under the impression that you could not make the isobaric setup too small due to pressure in the second chamber but I am absolutely no expert here.

I guess the big question is whether or not it would sell, everyone wants floor standers in the current market but as far as I can see, they want them cheap and with loads of bass.

Would enough people understand and purchase a big (ish) speaker with a flat response? I genuinely don't know, with that kind of sensitivity they should demo ok, but without the 'obvious' bass presence will they be chosen?

If RA can get them reviewed on Stereophile and grab USA and Asian market, he can preorder a new yacht. UK and Europe is a bust for such exotica.

 

[Vladimir]

Good because you get very deep, accurate and undistorted bass from smaller enclosures, but it may kill your business since these days everyone wants small petite amps integrated inside a gadget. Isobariks are totems of days of old. Only model that it would work is making your own active speakers (class D servo on the woofers) with isobaric loading but then again you are going in a smaller market niche called actives.

I tend to prefer acoustic suspension solutions as easier to live with and with very good results. The problem with those is that it's not so easy to create the midbass hump everyone wants in the hi-fi showroom. They have to be realitively flat, unfortunately.

 

[Vladimir]

You sitting comfortably Vlad??. Try 88/89dB @ 2.8 volts!!!. This is the bit that's driving me nuts. And all in an enclosure 100cms tall, 24cms wide, 28cms deep. Crazy right??. Checked the model 9 times now. It's right though.*wacko*

That is insanely! good result. The drivers must have some very nice linear motors to be that efficient.

I especially like that speaker enclosure format. You can advertise those as a retro Isobaric style revival. Enough with the BBC monitor hysteria already...

Anyone heard the Linn Majik Isobarik?

 

[plastic penguin]

Is this what you're looking for?

 

[Al ears]

I was under the impression that you could not make the isobaric setup too small due to pressure in the second chamber but I am absolutely no expert here.

I guess the big question is whether or not it would sell, everyone wants floor standers in the current market but as far as I can see, they want them cheap and with loads of bass.

Would enough people understand and purchase a big (ish) speaker with a flat response? I genuinely don't know, with that kind of sensitivity they should demo ok, but without the 'obvious' bass presence will they be chosen?

If RA can get them reviewed on Stereophile and grab USA and Asian market, he can preorder a new yacht. UK and Europe is a bust for such exotica.

And if he does he'll need a bigger factory and more staff.... *biggrin*

 

[Vladimir]

And if he does he'll need a bigger factory and more staff.... *biggrin*

I would simply outsource to the Danes or Germans.

 

[matt49]

If you got those IMO impressive 8 ohms and >84dB, I would definitely vote for such a speakers to be made. Those would be rare gems on today's market.

You sitting comfortably Vlad??. Try 88/89dB @ 2.8 volts!!!. This is the bit that's driving me nuts. And all in an enclosure 100cms tall, 24cms wide, 28cms deep. Crazy right??. Checked the model 9 times now. It's right though.*wacko*

In comparison to the isobarically loaded Neat Ultimatum XLi, that's the same height, 2 cm wider and 9 cm shallower. So aside from the 9 cm extra depth of the Neats, it's very similar. Neat claim 87dB sensitivity.

 

[Al ears]

And Neat also claim about £9000 .....

 

[Vladimir]

Both Linn Majik Isobarik and Neat Ultimatum XLi are ported. Richard said he tested a closed box in Clio and got an easy impedance and good efficiency. A true Olson isobaric design, 64 years old now.

 

[matt49]

And Neat also claim about £9000 .....

True. I'm sure Richard will be aiming rather lower in price, if not performance.

 

[CnoEvil]

Anyone heard the Linn Majik Isobarik?

I have - briefly.

I preferred it to the other Majik speakers in the range. They were pleasant enough with more substantial bass, but nothing exceptional. I would prefer some R700s at £1500 cheaper.

 

[lindsayt]

I was disappointed with the Majik Isobariks when I heard them with Linn Klimax DS and LP12SE sources and Klimax pre-amp and a few thousand quids worth of active Linn power amplification.

Weakest area was the bass, which couldn't start and stop properly. It sounded like you were listening to bass drivers that had been put in a box with the sound coming out of a hole the box. IE like you were listening to what they are.

At a very high listening level the midrange was badly distorting too. To the point where it was difficult to tell an electric guitar from a synthesizer on the Led Zeppelin test track.

I prefer the original Linn Isobariks to the Majik Isobariks.

 

[Richard Allen]

And Neat also claim about £9000 .....

True. I'm sure Richard will be aiming rather lower in price, if not performance.

Ouch!!!. Thanks Matt!!. Lower in price yes. £4000ish. Lower in performance?. We'll see about that one. If I don't think it works then it won't see the light of day.

 

[Al ears]

And Neat also claim about £9000 .....

True. I'm sure Richard will be aiming rather lower in price, if not performance.

Ouch!!!. Thanks Matt!!. Lower in price yes. £4000ish. Lower in performance?. We'll see about that one. If I don't think it works then it won't see the light of day.

I don't think Matt meant it that way (at least I think not) *biggrin*

But it does beg to question how, if you have not actually built a pair of fully-functioning isobaric speakers, you can quote a price of £4000?

Do you build your speakers to a preconceived price.