Question: Isobaric vs. DVC - Page 3 - diyAudio
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Old 20th October 2011, 09:44 AM   #21
sreten is offline sreten  United Kingdom
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Location: Brighton UK
Quote:
Originally Posted by Don Hills View Post
There is no increase in overall power handling,
because each driver still requires 1 watt.
Hi,

No. There is no increase in maximum SPL. The efficiency is halved, the
overall power handling doubles so you end up with the same maximum SPL.
I assume that is what you are really meant.

Your basically trading efficiency with box size, halving both.

rgds, sreten.
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Last edited by sreten; 20th October 2011 at 09:46 AM.
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Old 21st October 2011, 12:18 AM   #22
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Quote:
Originally Posted by sreten View Post
... No. There is no increase in maximum SPL. The efficiency is halved, the overall power handling doubles so you end up with the same maximum SPL. I assume that is what you are really meant. ...
I thought that's what I said? :-)

Manuel asked:
"Witch actually means that the increased powerhandling (double the drivers) of an isobaric configuration will make up for the 3dB loss of efficiency?"

I answered:
"It makes up for it exactly. There is no increase in output."

Something I said later may have led to the confusion, for which I apologise:
"So for a given SPL in isobaric configuration you require twice the total power to compensate for the "half sized" box. There is thus no increase in overall power handling, because each driver still requires 1 watt."

What I tried to say is that there is no free lunch, you won't be able to generate more SPL from an isobaric than a comparably tuned (box twice the size) single driver.
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Old 21st October 2011, 11:07 AM   #23
dangus is offline dangus  Canada
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The Codrive subwoofer in the "Way Down Deep" article wasn't all that impressive for the price. Way Down Deep III CoDrive CB1 | Home Theater
It's an interesting and patentable idea, but you could get the same effect by just cutting another hole in the box and adding a second driver.

I find it difficult to think of any situation where an isobaric arrangement is useful, except possibly in a yacht where space is limited and extra weight will serve as ballast. Or a customer insists on it and doesn't care about cost. The sensible route is to put the money into one better or more appropriate driver, or enjoy the considerable benefits of two subs instead of one.

Last edited by dangus; 21st October 2011 at 11:20 AM.
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Old 21st October 2011, 02:01 PM   #24
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by dangus View Post

I find it difficult to think of any situation where an isobaric arrangement is useful.
Hi,

There is one. You have a 4 ohm sub amplifier and you've found a cheap 8 ohm
driver, but it can take the amplifiers output, but the box needed is somewhat
too large for your taste, due to high Vas, two isobarically are then an option.

If you use the so called clamshell arrangement, any assymetry in the drivers
suspension or magnet drive arrangement will be largely compensated, i.e.
you will make the driver "better", somewhat more linear.

I do agree the right driver is the best option, but sometimes you find
"bargain" drivers where isobaric could suit some circumstances.

rgds, sreten.
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Old 22nd October 2011, 09:25 AM   #25
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So there are actually drivers, lets say a 5 inch driver that has the same performance like a "standard" 5 inch driver but with half of the enclosure volume?
Lets say the normal enclosure volume for a 5 inch BR would be about 2.5 Liters, so a certain driver would just need less, around 1.25 liters?
Doesn't every driver size have it's typical enclosure volume, more or less I mean, to at once only have to use half of the "typical" volume sounds strange, like there was written before: there is no free lunch
What is there on the negative side? Lower efficiency? More power needed? etc...


Besides this, is it just possible to achieve a lower volume enclosure by just using double the power of a single driver, lets say 100 watt instead of a driver of 50 watts (or just a DVC of 2 times 50 watt) and some equalization? Would you get the same results as a isobaric configuration using the same two drivers of 50 watt?
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Old 22nd October 2011, 10:56 AM   #26
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by manuelbauwens View Post
So there are actually drivers, lets say a 5 inch driver that has the same
performance like a "standard" 5 inch driver but with half of the enclosure
volume?
Hi,

Simply put yes. Its down to how heavy you choose to make the cone,
that makes the suspension stiffer for a given Fs and how small you
can make the box for it.

But there is no free lunch, all things being equal, halving the box
volume you can use also halves the efficiency so you need twice
as much power. In the bass you can trade power and box size for
exactly the same bass response and maximum SPL capability.

rgds, sreten.
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There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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Old 22nd October 2011, 04:41 PM   #27
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Quote:
Originally Posted by sreten View Post
Simply put yes. Its down to how heavy you choose to make the cone,
that makes the suspension stiffer for a given Fs and how small you
can make the box for it.
Thank you for the clarification! A while ago I dismantled a jvc boomblaster, it had the ability to give some boom while being in itself not too big... There were two woofers(16 cm) inside, I always wondered why the surrounds and spiders were so stiff and why there was even a metal ring glued on the stick paper cone.
So if you stiffen up a driver cone and increase the moving mass, the enclosure can become smaller.

Things start to make more sense to me now
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